1 RasMol


2 Notices


 This software has been created from several sources. Much of the 
 code is from RasMol 2.6, as created by Roger Sayle. The torsion 
 angle code, new POVRAY3 code and other features are derived from the 
 RasMol2.6x1 revisions by Arne Mueller. The Ramachandran printer plot 
 code was derived from fisipl created by Frances C. Bernstein. See 
 the Protein Data Bank program tape. 

 The CIF modifications make use of a library based in part on CBFlib 
 by Paul J. Ellis and Herbert J. Bernstein. Parts of CBFlib is 
 loosely based on the CIFPARSE software package from the NDB at 
 Rutgers university. Please type the RasMol commands 'help copying', 
 'help general', 'help IUCR', 'help CBFlib',  and 'help CIFPARSE' for 
 applicable notices. Please type 'help copyright' for copyright 
 notices. If you use RasMol V2.6 or an earlier version, type the 
 RasMol command 'help oldnotice'. 

3 Copying_RasMol
 This version is based on RasMol version 2.6_CIF.2, RasMol 2.6x1 and 
 RasMol_2.6.4. If you are not going to make changes to RasMol, you 
 are not only permitted to freely make copies and distribute them, 
 you are encouraged to do so, provided you do the following: 

  1. Either include the complete documentation, especially the file 
 NOTICE, with what you distribute or provide a clear indication where 
 people can get a copy of the documentation; and 

  2. Please give credit where credit is due citing the version and 
 original authors properly; and 

  3. Please do not give anyone the impression that the original 
 authors are providing a warranty of any kind. 

 If you would like to use major pieces of RasMol in some other 
 program, make modifications to RasMol, or in some other way make 
 what a lawyer would call a "derived work", you are not only 
 permitted to do so, you are encouraged to do so. In addition to the 
 things we discussed above, please do the following: 

  4. Please explain in your documentation how what you did differs 
 from this version of RasMol; and 

  5. Please make your modified source code available. 

 This version of RasMol is _not_ in the public domain, but it is 
 given freely to the community in the hopes of advancing science. If 
 you make changes, please make them in a responsible manner, and 
 please offer us the opportunity to include those changes in future 
 versions of RasMol. 

3 General_Notice
 The following notice applies to this work as a whole and to the 
 works included within it: 

 * Creative endeavors depend on the lively exchange of ideas. There 
 are laws and customs which establish rights and responsibilities for 
 authors and the users of what authors create. This notice is not 
 intended to prevent you from using the software and documents in 
 this package, but to ensure that there are no misunderstandings 
 about terms and conditions of such use. 

 * Please read the following notice carefully. If you do not 
 understand any portion of this notice, please seek appropriate 
 professional legal advice before making use of the software and 
 documents included in this software package. In addition to whatever 
 other steps you may be obliged to take to respect the intellectual 
 property rights of the various parties involved, if you do make use 
 of the software and documents in this package, please give credit 
 where credit is due by citing this package, its authors and the URL 
 or other source from which you obtained it, or equivalent primary 
 references in the literature with the same authors. 

 * Some of the software and documents included within this software 
 package are the intellectual property of various parties, and 
 placement in this package does not in any way imply that any such 
 rights have in any way been waived or diminished. 

 * With respect to any software or documents for which a copyright 
 exists, ALL RIGHTS ARE RESERVED TO THE OWNERS OF SUCH COPYRIGHT. 

 * Even though the authors of the various documents and software 
 found here have made a good faith effort to ensure that the 
 documents are correct and that the software performs according to 
 its documentation, and we would greatly appreciate hearing of any 
 problems you may encounter, the programs and documents and any files 
 created by the programs are provided **AS IS** without any warranty 
 as to correctness, merchantability or fitness for any particular or 
 general use. 

 * THE RESPONSIBILITY FOR ANY ADVERSE CONSEQUENCES FROM THE USE OF 
 PROGRAMS OR DOCUMENTS OR ANY FILE OR FILES CREATED BY USE OF THE 
 PROGRAMS OR DOCUMENTS LIES SOLELY WITH THE USERS OF THE PROGRAMS OR 
 DOCUMENTS OR FILE OR FILES AND NOT WITH AUTHORS OF THE PROGRAMS OR 
 DOCUMENTS. 

 Subject to your acceptance of the conditions stated above, and your 
 respect for the terms and conditions stated in the notices below, if 
 you are not going to make any modifications or create derived works, 
 you are given permission to freely copy and distribute this package, 
 provided you do the following: 

 1. Either include the complete documentation, especially the file 
 NOTICE, with what you distribute or provide a clear indication where 
 people can get a copy of the documentation; and 

 2. Give credit where credit is due citing the version and original 
 authors properly; and 

 3. Do not give anyone the impression that the original authors are 
 providing a warranty of any kind. 

 In addition, you may also modify this package and create derived 
 works provided you do the following: 

 4. Explain in your documentation how what you did differs from this 
 version of RasMol; and 

 5. Make your modified source code available. 

3 RasMol_V2.6_Notice
 The following notice applies to RasMol V 2.6 and older RasMol 
 versions. 

 Information in this document is subject to change without notice and 
 does not represent a commitment on the part of the supplier. This 
 package is sold/distributed subject to the condition that it shall 
 not, by way of trade or otherwise, be lent, re-sold, hired out or 
 otherwise circulated without the supplier's prior consent, in any 
 form of packaging or cover other than that in which it was produced. 
 No part of this manual or accompanying software may be reproduced, 
 stored in a retrieval system on optical or magnetic disk, tape or 
 any other medium, or transmitted in any form or by any means, 
 electronic, mechanical, photocopying, recording or otherwise for any 
 purpose other than the purchaser's personal use. 

 This product is not to be used in the planning, construction, 
 maintenance, operation or use of any nuclear facility nor the 
 flight, navigation or communication of aircraft or ground support 
 equipment. The author shall not be liable, in whole or in part, for 
 any claims or damages arising from such use, including death, 
 bankruptcy or outbreak of war. 

3 IUCR_Policy
 The IUCr Policy for the Protection and the Promotion of the STAR 
 File and CIF Standards for Exchanging and Archiving Electronic Data 

 Overview 

 The Crystallographic Information File (CIF)[1] is a standard for 
 information interchange promulgated by the International Union of 
 Crystallography (IUCr). CIF (Hall, Allen & Brown, 1991) is the 
 recommended method for submitting publications to Acta 
 Crystallographica Section C and reports of crystal structure 
 determinations to other sections of Acta Crystallographica and many 
 other journals. The syntax of a CIF is a subset of the more general 
 STAR File[2] format. The CIF and STAR File approaches are used 
 increasingly in the structural sciences for data exchange and 
 archiving, and are having a significant influence on these 
 activities in other fields. 

 Statement of intent 

 The IUCr's interest in the STAR File is as a general data 
 interchange standard for science, and its interest in the CIF, a 
 conformant derivative of the STAR File, is as a concise data 
 exchange and archival standard for crystallography and structural 
 science. 

 Protection of the standards 

 To protect the STAR File and the CIF as standards for interchanging 
 and archiving electronic data, the IUCr, on behalf of the scientific 
 community, 

  * holds the copyrights on the standards themselves, 

  * owns the associated trademarks and service marks, and 

  * holds a patent on the STAR File. 

 These intellectual property rights relate solely to the interchange 
 formats, not to the data contained therein, nor to the software used 
 in the generation, access or manipulation of the data. 

 Promotion of the standards 

 The sole requirement that the IUCr, in its protective role, imposes 
 on software purporting to process STAR File or CIF data is that the 
 following conditions be met prior to sale or distribution. 

  * Software claiming to read files written to either the STAR File 
 or the CIF standard must be able to extract the pertinent data from 
 a file conformant to the STAR File syntax, or the CIF syntax, 
 respectively. 

  * Software claiming to write files in either the STAR File, or the 
 CIF, standard must produce files that are conformant to the STAR 
 File syntax, or the CIF syntax, respectively. 

  * Software claiming to read definitions from a specific data 
 dictionary approved by the IUCr must be able to extract any 
 pertinent definition which is conformant to the dictionary 
 definition language (DDL)[3] associated with that dictionary. 

 The IUCr, through its Committee on CIF Standards, will assist any 
 developer to verify that software meets these conformance 
 conditions. 

 Glossary of terms 

 [1] CIF: is a data file conformant to the file syntax defined at 
 http://www.iucr.org/iucr-top/cif/spec/index.html 

 [2] STAR File: is a data file conformant to the file syntax defined 
 at http://www.iucr.org/iucr-top/cif/spec/star/index.html 

 [3] DDL: is a language used in a data dictionary to define data 
 items in terms of "attributes". Dictionaries currently approved by 
 the IUCr, and the DDL versions used to construct these dictionaries, 
 are listed at http://www.iucr.org/iucr-top/cif/spec/ddl/index.html 

 Last modified: 30 September 2000 

 IUCR Policy Copyright (C) 2000 International Union of 
 Crystallography 

3 CBFLIB
 The following Disclaimer Notice applies to CBFlib V0.1, from which 
 this code in part is derived. 

 * The items furnished herewith were developed under the sponsorship 
 of the U.S. Government. Neither the U.S., nor the U.S. D.O.E., nor 
 the Leland Stanford Junior University, nor their employees, makes 
 any warranty, express or implied, or assumes any liability or 
 responsibility for accuracy, completeness or usefulness of any 
 information, apparatus, product or process disclosed, or represents 
 that its use will not infringe privately-owned rights. Mention of 
 any product, its manufacturer, or suppliers shall not, nor is it 
 intended to, imply approval, disapproval, or fitness for any 
 particular use. The U.S. and the University at all times retain the 
 right to use and disseminate the furnished items for any purpose 
 whatsoever. 

 Notice 91 02 01 

3 CIFPARSE
 Portions of this software are loosely based on the CIFPARSE software 
 package from the NDB at Rutgers University. See 

  http://ndbserver.rutgers.edu/NDB/mmcif/software 

 CIFPARSE is part of the NDBQUERY application, a program component of 
 the Nucleic Acid Database Project [ H. M. Berman, W. K. Olson, D. L. 
 Beveridge, J. K. Westbrook, A. Gelbin, T. Demeny, S. H. Shieh, A. R. 
 Srinivasan, and B. Schneider. (1992). The Nucleic Acid Database: A 
 Comprehensive Relational Database of Three-Dimensional Structures of 
 Nucleic Acids. Biophys J., 63, 751-759.], whose cooperation is 
 gratefully acknowledged, especially in the form of design concepts 
 created by J. Westbrook. 

 Please be aware of the following notice in the CIFPARSE API: 

 This software is provided WITHOUT WARRANTY OF MERCHANTABILITY OR 
 FITNESS FOR A PARTICULAR PURPOSE OR ANY OTHER WARRANTY, EXPRESS OR 
 IMPLIED. RUTGERS MAKE NO REPRESENTATION OR WARRANTY THAT THE 
 SOFTWARE WILL NOT INFRINGE ANY PATENT, COPYRIGHT OR OTHER 
 PROPRIETARY RIGHT. 

2 Introduction
 RasMol is a molecular graphics program intended for the 
 visualisation of proteins, nucleic acids and small molecules. The 
 program is aimed at display, teaching and generation of publication 
 quality images. RasMol runs on wide range of architectures and 
 operating systems including Microsoft Windows, Apple Macintosh, UNIX 
 and VMS systems. UNIX and VMS versions require an 8, 24 or 32 bit 
 colour X Windows display (X11R4 or later). The X Windows version of 
 RasMol provides optional support for a hardware dials box and 
 accelerated shared memory communication (via the XInput and MIT-SHM 
 extensions) if available on the current X Server. 

 The program reads in a molecule coordinate file and interactively 
 displays the molecule on the screen in a variety of colour schemes 
 and molecule representations. Currently available representations 
 include depth-cued wireframes, 'Dreiding' sticks, spacefilling (CPK) 
 spheres, ball and stick, solid and strand biomolecular ribbons, atom 
 labels and dot surfaces. 

 The RasMol help facility can be accessed by typing "help <topic>" or 
 "help <topic> <subtopic>" from the command line. A complete list of 
 RasMol commands may be displayed by typing "help commands". A single 
 question mark may also be used to abbreviate the keyword "help". 
 Please type "help notices" for important notices. 

2 Commands
 RasMol allows the execution of interactive commands typed at the 
 'RasMol>' prompt in the terminal window. Each command must be given 
 on a separate line. Keywords are case insensitive and may be entered 
 in either upper or lower case letters. All whitespace characters are 
 ignored except to separate keywords and their arguments. 

 The commands/keywords currently recognised by RasMol are given 
 below. 

3 Backbone
 The RasMol 'backbone' command permits the representation of a 
 polypeptide backbone as a series of bonds connecting the adjacent 
 alpha carbons of each amino acid in a chain. The display of these 
 backbone 'bonds' is turned on and off by the command parameter in 
 the same way as with the 'wireframe' command. The command 'backbone 
 off' turns off the selected 'bonds', and 'backbone on' or with a 
 number turns them on. The number can be used to specify the cylinder 
 radius of the representation in either Angstrom or RasMol units. A 
 parameter value of 500 (2.0 Angstroms) or above results in a 
 "Parameter value too large" error. Backbone objects may be coloured 
 using the RasMol 'colour backbone' command. 

 The reserved word backbone is also used as a predefined set ("help 
 sets") and as a parameter to the 'set hbond' and 'set ssbond' 
 commands. The RasMol command 'trace' renders a smoothed backbone, in 
 contrast to 'backbone' which connects alpha carbons with straight 
 lines. 

 The backbone may be displayed with dashed lines by use of the 
 'backbone dash' command. 

3 Background
 The RasMol 'background' command is used to set the colour of the 
 "canvas" background. The colour may be given as either a colour name 
 or a comma separated triple of Red, Green and Blue (RGB) components 
 enclosed in square brackets. Typing the command 'help colours' will 
 give a list of the predefined colour names recognised by RasMol. 
 When running under X Windows, RasMol also recognises colours in the 
 X server's colour name database. 

 The 'background' command is synonymous with the RasMol 'set 
 background' command. 

3 Cartoon
 The RasMol 'cartoon' command does a display of a molecule 'ribbons' 
 as Richardson (MolScript) style protein 'cartoons', implemented as 
 thick (deep) ribbons. The easiest way to obtain a cartoon 
 representation of a protein is to use the 'Cartoons' option on the 
 'Display' menu. The 'cartoon' command represents the currently 
 selected residues as a deep ribbon with width specified by the 
 command's argument. Using the command without a parameter results in 
 the ribbon's width being taken from the protein's secondary 
 structure, as described in the 'ribbons' command. By default, the 
 C-termini of beta-sheets are displayed as arrow heads. This may be 
 enabled and disabled using the 'set cartoons' command. The depth of 
 the cartoon may be adjusted using the 'set cartoons <number>' 
 command. The 'set cartoons' command without any parameters returns 
 these two options to their default values. 

3 Centre
 The RasMol 'centre' command defines the point about which the 
 'rotate' command and the scroll bars rotate the current molecule. 
 Without a parameter the centre command resets the centre of rotation 
 to be the centre of gravity of the molecule. If an atom expression 
 is specified, RasMol rotates the molecule about the centre of 
 gravity of the set of atoms specified by the expression. Hence, if a 
 single atom is specified by the expression, that atom will remain 
 'stationary' during rotations. 

 Type 'help expression' for more information on RasMol atom 
 expressions. 

 Alternatively the centring may be given as a comma separated triple 
 of [CenX, CenY, CenZ] offsets in RasMol units (1/250 of an Angstrom) 
 from the centre of gravity. The triple must be enclosed in square 
 brackets. 

3 Clipboard
 The RasMol 'clipboard' command places a copy of the currently 
 displayed image on the local graphics 'clipboard'. Note: this 
 command is not yet supported on UNIX or VMS machines. It is intended 
 to make transfering images between applications easier under 
 Microsoft Windows or on an Apple Macintosh. 

 When using RasMol on a UNIX or VMS system this functionality may be 
 achieved by generating a raster image in a format that can be read 
 by the receiving program using the RasMol 'write' command. 

3 Colour
 Colour the atoms (or other objects) of the selected region. The 
 colour may be given as either a colour name or a comma separated 
 triple of Red, Green and Blue (RGB) components enclosed in square 
 brackets. Typing the command 'help colours' will give a list of all 
 the predefined colour names recognised by RasMol. 

 Allowed objects are 'atoms', 'bonds', 'backbone', 'ribbons', 
 'labels', 'dots', 'hbonds' and 'ssbonds'. If no object is specified, 
 the default keyword 'atom' is assumed. Some colour schemes are 
 defined for certain object types. The colour scheme 'none' can be 
 applied to all objects except atoms and dots, stating that the 
 selected objects have no colour of their own, but use the colour of 
 their associated atoms (i.e. the atoms they connect). 'Atom' objects 
 can also be coloured by 'alt', 'amino', 'chain', 'charge', 'cpk', 
 'group', 'model', 'shapely', 'structure', 'temperature' or 'user'. 
 Hydrogen bonds can also be coloured by 'type' and dot surfaces can 
 also be coloured by 'electrostatic potential'. For more information 
 type 'help colour <colour>'. 

3 Connect
 The RasMol 'connect' command is used to force RasMol to 
 (re)calculate the connectivity of the current molecule. If the 
 original input file contained connectivity information, this is 
 discarded. The command 'connect false' uses a fast heuristic 
 algorithm that is suitable for determining bonding in large 
 bio-molecules such as proteins and nucleic acids. The command 
 'connect true' uses a slower more accurate algorithm based upon 
 covalent radii that is more suitable to small molecules containing 
 inorganic elements or strained rings. If no parameters are given, 
 RasMol determines which algorithm to use based on the number of 
 atoms in the input file. Greater than 255 atoms causes RasMol to use 
 the faster implementation. This is the method used to determine 
 bonding, if necessary, when a molecule is first read in using the 
 'load' command. 

3 Define
 The RasMol 'define' command allows the user to associate an 
 arbitrary set of atoms with a unique identifier. This allows the 
 definition of user-defined sets. These sets are declared statically, 
 i.e. once defined the contents of the set do not change, even if the 
 expression defining them depends on the current transformation and 
 representation of the molecule. 

3 Dots
 The RasMol 'dots' command is used to generate a van der Waals' dot 
 surface around the currently selected atoms. Dot surfaces display 
 regularly spaced points on a sphere of van der Waals' radius about 
 each selected atom. Dots that would are 'buried' within the van der 
 Waals' radius of any other atom (selected or not) are not displayed. 
 The command 'dots on' deletes any existing dot surface and generates 
 a dots surface around the currently selected atom set with a default 
 dot density of 100. The command 'dots off' deletes any existing dot 
 surface. The dot density may be specified by providing a numeric 
 parameter between 1 and 1000. This value approximately corresponds 
 to the number of dots on the surface of a medium sized atom. 

 By default, the colour of each point on a dot surface is the colour 
 of its closest atom at the time the surface is generated. The colour 
 of the whole dot surface may be changed using the 'colour dots' 
 command. 

3 Echo
 The RasMol 'echo' command is used to display a message in the RasMol 
 command/terminal window. The string parameter may optionally be 
 delimited in double quote characters. If no parameter is specified, 
 the 'echo' command displays a blank line. This command is 
 particularly useful for displaying text from within a RasMol 
 'script' file. 

3 English
 The RasMol 'English' command sets the menus and messages to the 
 English versions. The command 'Spanish' may be used to select 
 Spanish menus and messages. 

3 HBonds
 The RasMol 'hbond' command is used to represent the hydrogen bonding 
 of the protein molecule's backbone. This information is useful in 
 assessing the protein's secondary structure. Hydrogen bonds are 
 represented as either dotted lines or cylinders between the donor 
 and acceptor residues. The first time the 'hbond' command is used, 
 the program searches the structure of the molecule to find hydrogen 
 bonded residues and reports the number of bonds to the user. The 
 command 'hbonds on' displays the selected 'bonds' as dotted lines, 
 and the 'hbonds off' turns off their display. The colour of hbond 
 objects may be changed by the 'colour hbond' command. Initially, 
 each hydrogen bond has the colours of its connected atoms. 

 By default the dotted lines are drawn between the accepting oxygen 
 and the donating nitrogen. By using the 'set hbonds' command the 
 alpha carbon positions of the appropriate residues may be used 
 instead. This is especially useful when examining proteins in 
 backbone representation. 

3 Help
 The RasMol 'help' command provides on-line help on the given topic. 

3 Label
 The RasMol 'label' command allows an arbitrary formatted text string 
 to be associated with each currently selected atom. This string may 
 contain embedded 'expansion specifiers' which display properties of 
 the atom being labelled. An expansion specifier consists of a '%' 
 character followed by a single alphabetic character specifying the 
 property to be An actual '%' character may be displayed by using the 
 expansion specifier '%%'. 

 Atom labelling for the currently selected atoms may be turned off 
 with the command 'label off'. By default, if no string is given as a 
 parameter, RasMol uses labels appropriate for the current molecule. 

 The colour of each label may be changed using the 'colour label' 
 command. By default, each label is drawn in the same colour as the 
 atom to which it is attached. The size and spacing of the displayed 
 text may be changed using the 'set fontsize' command. The width of 
 the strokes in the displayed text may be changed  using the 'set 
 fontstroke'  command. 

3 Load
 Load a molecule coordinate file into RasMol. Valid molecule file 
 formats are 'pdb' (Protein Data Bank format), 'mdl' (Molecular 
 Design Limited's MOL file format), 'alchemy' (Tripos' Alchemy file 
 format), 'mol2' (Tripos' Sybyl Mol2 file format), 'charmm' (CHARMm 
 file format), 'xyz' (MSC's XMol XYZ file format), 'mopac' (J. P. 
 Stewart's MOPAC file format) or 'cif' (IUCr CIF or mmCIF file 
 format). If no file format is specified, 'PDB', 'CIF', or 'mmCIF' is 
 assumed by default. Only a single molecule may be loaded at a time. 
 To delete a molecule prior to loading another use the RasMol 'zap' 
 command. 

 The 'load' command selects all the atoms in the molecule, centres it 
 on the screen and renders it as a CPK coloured wireframe model. If 
 the molecule contains no bonds (i.e. contains only alpha carbons), 
 it is drawn as an alpha carbon backbone. If the file specifies fewer 
 bonds than atoms, RasMol determines connectivity using the 'connect' 
 command. 

 The 'load inline' command also allows the storing of atom 
 coordinates in scripts to allow better integration with WWW 
 browsers. A load command executed inside a script file may specify 
 the keyword 'inline' instead of a conventional filename. This option 
 specifies that the coordinates of the molecule to load are stored in 
 the same file as the currently executing commands. 

3 Monitor
 The RasMol 'monitor' command allows the display of distance 
 monitors. A distance monitor is a dashed (dotted) line between an 
 arbitrary pair of atoms, optionally labelled by the distance between 
 them. The RasMol command 'monitor <number> <number>' adds such a 
 distance monitor between the two atoms specified by the atom serial 
 numbers given as parameters 

 Distance monitors are turned off with the command 'monitors off'. By 
 default, monitors display the distance between its two end points as 
 a label at the centre of the monitor. These distance labels may be 
 turned off with the command 'set monitors off', and re-enabled with 
 the command 'set monitors on'. Like most other representations, the 
 colour of a monitor is taken from the colour of its end points 
 unless specified by the 'colour monitors' command. 

 Distance monitors may also be added to a molecule interactively with 
 the mouse, using the 'set picking monitor' command. Clicking on an 
 atom results in its being identified on the rasmol command line. In 
 addition every atom picked increments a modulo counter such that, in 
 monitor mode, every second atom displays the distance between this 
 atom and the previous one. The shift key may be used to form 
 distance monitors between a fixed atom and several consecutive 
 positions. A distance monitor may also be removed (toggled) by 
 selecting the appropriate pair of atom end points a second time. 

3 Pause
 The RasMol 'pause' command is used in script files to stop the 
 script file for local manipulation by a mouse, until any key is 
 pushed to restart the script file. 'Wait' is synonymous with 
 'pause'. This command may be executed in RasMol script files to 
 suspend the sequential execution of commands and allow the user to 
 examine the current image. When RasMol executes a 'pause' command in 
 a script file, it suspends execution of the rest of the file, 
 refreshes the image on the screen and allows the manipulation of the 
 image using the mouse and scroll bars, or resizing of the graphics 
 window. Once a key is pressed, control returns to the script file at 
 the line following the 'pause' command. While a script is suspended 
 the molecule may be rotated, translated, scaled, slabbed and picked 
 as usual, but all menu commands are disabled. 

3 Print
 The RasMol 'print' command sends the currently displayed image to 
 the local default printer using the operating system's native 
 printer driver. Note: this command is not yet supported under UNIX 
 or VMS. It is intended to take advantage of Microsoft Windows and 
 Apple Macintosh printer drivers. For example, this allows images to 
 be printed directly on a dot matrix printer. 

 When using RasMol on a UNIX or VMS system this functionality may be 
 achieved by either generating a PostScript file using the RasMol 
 'write ps' or 'write vectps' commands and printing that or 
 generating a raster image file and using a utility to dump that to 
 the local printer. 

3 Quit
 Exit from the RasMol program. The RasMol commands 'exit' and 'quit' 
 are synonymous, except within nested scripts. In that case, 'exit' 
 terminates only the current level, while 'quit' terminates all 
 nested levels of scripts. 

3 Refresh
 The RasMol 'refresh' command redraws the current image. This is 
 useful in scripts to ensure application of a complex list of 
 parameter changes. 

3 Renumber
 The RasMol 'renumber' command sequentially numbers the residues in a 
 macromolecular chain. The optional parameter specifies the value of 
 the first residue in the sequence. By default, this value is one. 
 For proteins, each amino acid is numbered consecutively from the N 
 terminus to the C terminus. For nucleic acids, each base is numbered 
 from the 5' terminus to the 3' terminus. All chains in the current 
 database are renumbered and gaps in the original sequence are 
 ignored. The starting value for numbering may be negative. 

3 Reset
 The RasMol 'reset' command restores the original viewing 
 transformation and centre of rotation. The scale is set to its 
 default value, 'zoom 100', the centre of rotation is set to the 
 geometric centre of the currently loaded molecule, 'centre all', 
 this centre is translated to the middle of the screen and the 
 viewpoint set to the default orientation. 

 This command should not be mistaken for the RasMol 'zap' command 
 which deletes the currently stored molecule, returning the program 
 to its initial state. 

3 Restrict
 The RasMol 'restrict' command both defines the currently selected 
 region of the molecule and disables the representation of (most of) 
 those parts of the molecule no longer selected. All subsequent 
 RasMol commands that modify a molecule's colour or representation 
 affect only the currently selected region. The parameter of a 
 'restrict' command is a RasMol atom expression that is evaluated for 
 every atom of the current molecule. This command is very similar to 
 the RasMol 'select' command, except 'restrict' disables the 
 'wireframe', 'spacefill' and 'backbone' representations in the 
 non-selected region. 

 Type "help expression" for more information on RasMol atom 
 expressions. 

3 Ribbons
 The RasMol 'ribbons' command displays the currently loaded protein 
 or nucleic acid as a smooth solid "ribbon" surface passing along the 
 backbone of the protein. The ribbon is drawn between each amino acid 
 whose alpha carbon is currently selected. The colour of the ribbon 
 is changed by the RasMol 'colour ribbon' command. If the current 
 ribbon colour is 'none' (the default), the colour is taken from the 
 alpha carbon at each position along its length. 

 The width of the ribbon at each position is determined by the 
 optional parameter in the usual RasMol units. By default the width 
 of the ribbon is taken from the secondary structure of the protein 
 or a constant value of 720 (2.88 Angstroms) for nucleic acids. The 
 default width of protein alpha helices and beta sheets is 380 (1.52 
 Angstroms) and 100 (0.4 Angstroms) for turns and random coil. The 
 secondary structure assignment is either from the PDB file or 
 calculated using the DSSP algorithm as used by the 'structure' 
 command. This command is similar to the RasMol command 'strands' 
 which renders the biomolecular ribbon as parallel depth-cued curves. 

3 Rotate
 Rotate the molecule about the specified axis. Permitted values for 
 the axis parameter are The integer parameter states the angle in 
 degrees for the structure to be rotated. For the X and Y axes, 
 positive values move the closest point up and right, and negative 
 values move it down and left, respectively. For the Z axis, a 
 positive rotation acts clockwise and a negative angle 
 anti-clockwise. 

3 Save
 Save the currently selected set of atoms in a Protein Data Bank 
 (PDB), MDL, Alchemy(tm) or XYZ format file. The distinction between 
 this command and the RasMol 'write' command has been dropped. The 
 only difference is that without a format specifier the 'save' 
 command generates a 'PDB' file and the 'write' command generates a 
 'GIF' image. 

3 Script
 The RasMol 'script' command reads a set of RasMol commands 
 sequentially from a text file and executes them. This allows 
 sequences of commonly used commands to be stored and performed by 
 single command. A RasMol script file may contain a further script 
 command up to a maximum "depth" of 10, allowing complicated 
 sequences of actions to be executed. RasMol ignores all characters 
 after the first '#' character on each line allowing the scripts to 
 be annotated. Script files are often also annotated using the RasMol 
 'echo' command. 

 The most common way to generate a RasMol script file is to use the 
 'write script' or 'write rasmol' commands to output the sequence of 
 commands that are needed to regenerate the current view, 
 representation and colouring of the currently displayed molecule. 

 The RasMol command 'source' is synonymous with the 'script' command. 

3 Select
 Define the currently selected region of the molecule. All subsequent 
 RasMol commands that manipulate a molecule or modify its colour or 
 representation only affect the currently selected region. The 
 parameter of a 'select' command is a RasMol expression that is 
 evaluated for every atom of the current molecule. The currently 
 selected (active) region of the molecule are those atoms that cause 
 the expression to evaluate true. To select the whole molecule use 
 the RasMol command 'select all'. The behaviour of the 'select' 
 command without any parameters is determined by the RasMol 'hetero' 
 and 'hydrogen' parameters. 

 Type "help expression" for more information on RasMol atom 
 expressions. 

3 Set
 The RasMol 'set' command allows the user to alter various internal 
 program parameters such as those controlling rendering options. Each 
 parameter has its own set or permissible parameter options. 
 Typically, omitting the paramter option resets that parameter to its 
 default value. A list of valid parameter names is given below. 

3 Show
 The RasMol 'show' command display details of the status of the 
 currently loaded molecule. The command 'show information' lists the 
 molecule's name, classification, PDB code and the number of atoms, 
 chains, groups it contains. If hydrogen bonding, disulphide bridges 
 or secondary structure have been determined, the number of hbonds, 
 ssbonds, helices, ladders and turns are also displayed, 
 respectively. The command 'show phipsi' shows the phi and psi angles 
 of the currently selected residues and the omega angles of cis 
 peptide bonds. The command 'show RamPrint' (or 'show RPP' or 'show 
 RamachandranPrinterPlot') shows a simple Ramachandran printer plot 
 in the style of Frances Bernstein's fisipl program. The command 
 'show selected' (or 'show selected group' or 'show selected chain' 
 or 'show selected atom' ) shows the groups (default), chains or 
 atoms of the current selection. The command 'show sequence' lists 
 the residues that comprise each chain of the molecule. The command 
 'show symmetry' shows the space group and unit cell of the molecule. 

3 Slab
 The RasMol 'slab' command enables, disables or positions the 
 z-clipping plane of the molecule. The program only draws those 
 portions of the molecule that are further from the viewer than the 
 slabbing plane. Integer values range from zero at the very back of 
 the molecule to 100 which is completely in front of the molecule. 
 Intermediate values determine the percentage of the molecule to be 
 drawn. 

3 Spacefill
 The RasMol 'spacefill' command is used to represent all of the 
 currently selected atoms as solid spheres. This command is used to 
 produce both union-of-spheres and ball-and-stick models of a 
 molecule. The command, 'spacefill true', the default, represents 
 each atom as a sphere of van der Waals radius. The command 
 'spacefill off' turns off the representation of the selected atom as 
 spheres. A sphere radius may be specified as an integer in RasMol 
 units (1/250th Angstrom) or a value containing a decimal point. A 
 value of 500 (2.0 Angstroms) or greater results in a "Parameter 
 value too large" error. 

 The 'temperature' option sets the radius of each sphere to the value 
 stored in its temperature field. Zero or negative values have no 
 effect and values greater than 2.0 are truncated to 2.0. The 'user' 
 option allows the radius of each sphere to be specified by 
 additional lines in the molecule's PDB file using Raster 3D's COLOUR 
 record extension. 

 The RasMol command 'cpk' is synonymous with the 'spacefill' command. 

3 Spanish
 The RasMol 'Spanish' command sets the menus and messages to the 
 Spanish versions. The command 'English' may be used to select 
 English menus and messages. 

3 SSBonds
 The RasMol 'ssbonds' command is used to represent the disulphide 
 bridges of the protein molecule as either dotted lines or cylinders 
 between the connected cysteines. The first time that the 'ssbonds' 
 command is used, the program searches the structure of the protein 
 to find half-cysteine pairs (cysteines whose sulphurs are within 3 
 Angstroms of each other) and reports the number of bridges to the 
 user. The command 'ssbonds on' displays the selected "bonds" as 
 dotted lines, and the command 'ssbonds off' disables the display of 
 ssbonds in the currently selected area. Selection of disulphide 
 bridges is identical to normal bonds, and may be adjusted using the 
 RasMol 'set bondmode' command. The colour of disulphide bonds may be 
 changed using the 'colour ssbonds' command. By default, each 
 disulphide bond has the colours of its connected atoms. 

 By default disulphide bonds are drawn between the sulphur atoms 
 within the cysteine groups. By using the 'set ssbonds' command the 
 position of the cysteine's alpha carbons may be used instead. 

3 Star
 The RasMol 'star' command is used to represent all of the currently 
 selected atoms as stars (six strokes, one each in the x, -x, y, -y, 
 z and -z directions). The commands 'select not bonded' followed by 
 'star 75' are useful to mark unbonded atoms in a 'wireframe' display 
 with less overhead than provided by 'spacefill 75'. This can be done 
 automatically for all subsequent wireframe displays with the command 
 'set bondmode not bonded'. 

 The command 'star true', the default, represents each atom as a star 
 with strokes length equal to van der Waals radius. The command 'star 
 off' turns off the representation of the selected atom as stars. A 
 star stroke length may be specified as an integer in RasMol units 
 (1/250th Angstrom) or a value containing a decimal point. A value of 
 500 (2.0 Angstroms) or greater results in a "Parameter value too 
 large" error. 

 The 'temperature' option sets the stroke length of each star to the 
 value stored in its temperature field. Zero or negative values have 
 no effect and values greater than 2.0 are truncated to 2.0. The 
 'user' option allows the stroke length of each star to be specified 
 by additional lines in the molecule's PDB file using Raster 3D's 
 COLOUR record extension. 

 The RasMol 'spacefill' command can be used for more artistic 
 rendering of atoms as spheres. 

3 Stereo
 The RasMol 'stereo' command provides side-by-side stereo display of 
 images. Stereo viewing of a molecule may be turned on (and off) 
 either by selecting 'Stereo' from the 'Options' menu, or by typing 
 the commands 'stereo on' or 'stereo off'. The separation angle 
 between the two views may be adjusted with the 'set stereo [-] 
 <number>' command, where positive values result in crossed eye 
 viewing and negative values in relaxed (wall-eyed) viewing. The 
 inclusion of '[-] <number>' in the 'stereo' command, as for example 
 in 'stereo 3' or 'stereo -5', also controls angle and direction. 

 The stereo command is only partially implemented. When stereo is 
 turned on, the image is not properly recentred. (This can be done 
 with a 'translate x -<number>'  command.) It is not supported in 
 vector PostScript output files, is not saved by the 'write script' 
 command, and in general is not yet properly interfaced with several 
 other features of the program. 

3 Strands
 The RasMol 'strands' command displays the currently loaded protein 
 or nucleic acid as a smooth "ribbon" of depth-cued curves passing 
 along the backbone of the protein. The ribbon is composed of a 
 number of strands that run parallel to one another along the peptide 
 plane of each residue. The ribbon is drawn between each amino acid 
 whose alpha carbon is currently selected. The colour of the ribbon 
 is changed by the RasMol 'colour ribbon' command. If the current 
 ribbon colour is 'none' (the default), the colour is taken from the 
 alpha carbon at each position along its length. The central and 
 outermost strands may be coloured independently using the 'colour 
 ribbon1' and 'colour ribbon2' commands, respectively. The number of 
 strands in the ribbon may be altered using the RasMol 'set strands' 
 command. 

 The width of the ribbon at each position is determined by the 
 optional parameter in the usual RasMol units. By default the width 
 of the ribbon is taken from the secondary structure of the protein 
 or a constant value of 720 for nucleic acids (which produces a 
 ribbon 2.88 Angstroms wide). The default width of protein alpha 
 helices and beta sheets is 380 (1.52 Angstroms) and 100 (0.4 
 Angstroms) for turns and random coil. The secondary structure 
 assignment is either from the PDB file or calculated using the DSSP 
 algorithm as used by the 'structure' command. This command is 
 similar to the RasMol command 'ribbons' which renders the 
 biomolecular ribbon as a smooth shaded surface. 

3 Structure
 The RasMol 'structure' command calculates secondary structure 
 assignments for the currently loaded protein. If the original PDB 
 file contained structural assignment records (HELIX, SHEET and TURN) 
 these are discarded. Initially, the hydrogen bonds of the current 
 molecule are found, if this hasn't been done already. The secondary 
 structure is then determined using Kabsch and Sander's DSSP 
 algorithm. Once finished the program reports the number of helices, 
 strands and turns found. 

3 Trace
 The RasMol 'trace' command displays a smooth spline between 
 consecutive alpha carbon positions. This spline does not pass 
 exactly through the alpha carbon position of each residue, but 
 follows the same path as 'ribbons', 'strands' and 'cartoons'. Note 
 that residues may be displayed as 'ribbons', 'strands', 'cartoons' 
 or as a 'trace'. Enabling one of these representations disables the 
 others. However, a residue may be displayed simultaneously as 
 backbone and as one of the above representations. This may change in 
 future versions of RasMol. Prior to version 2.6, 'trace' was 
 synonymous with 'backbone'. 

 'Trace temperature' displays the backbone as a wider cylinder at 
 high temperature factors and thinner at lower. This representation 
 is useful to X-ray crystallographers and NMR spectroscopists. 

3 Translate
 The RasMol 'translate' command moves the position of the centre of 
 the molecule on the screen. The axis parameter specifies along which 
 axis the molecule is to be moved and the integer parameter specifies 
 the absolute position of the molecule centre from the middle of the 
 screen. Permitted values for the axis parameter are Displacement 
 values must be between -100 and 100 which correspond to moving the 
 current molecule just off the screen. A positive displacement moves 
 the molecule to the right, and a positive displacement moves the 
 molecule down the screen. The pair of commands 'translate x 0' and 
 'translate y 0' centres the molecule on the screen. 

3 Wireframe
 The RasMol 'wireframe' command represents each bond within the 
 selected region of the molecule as a cylinder, a line or a 
 depth-cued vector. The display of bonds as depth-cued vectors (drawn 
 darker the further away from the viewer) is turned on by the command 
 'wireframe' or 'wireframe on'. The selected bonds are displayed as 
 cylinders by specifying a radius either as an integer in RasMol 
 units or containing a decimal point as a value in Angstroms. A 
 parameter value of 500 (2.0 Angstroms) or above results in an 
 "Parameter value too large" error. Bonds may be coloured using the 
 'colour bonds' command. 

 Non-bonded atoms, which could become invisible in an ordinary 
 'wireframe' display can be marked by a preceding 'set bondmode not 
 bonded' command. If nearly co-linear bonds to atoms cause them to be 
 difficult to see in a wireframe display, the 'set bondmode all' 
 command will add markers for 'all' atoms in subsequent 'wireframe' 
 command executions. 

3 Write
 Write the current image to a file in a standard format. Currently 
 supported image file formats include 'bmp' (Microsoft bitmap) and 
 'gif' (Compuserve GIF), 'iris' (IRIS RGB), 'ppm' (Portable Pixmap), 
 'ras' (Sun rasterfile), 'ps' and 'epsf' (Encapsulated PostScript), 
 'monops' (Monochrome Encapsulated PostScript), 'pict' (Apple PICT), 
 'vectps' (Vector Postscript). The 'write' command may also be used 
 to generate command scripts for other graphics programs. The format 
 'script' writes out a file containing the RasMol 'script' commands 
 to reproduce the current image. The format 'molscript' writes out 
 the commands required to render the current view of the molecule as 
 ribbons in Per Kraulis' Molscript program and the format 'kinemage' 
 the commands for David Richardson's program Mage. The following 
 formats are useful for further processing: 'povray' (POVRay 2), 
 'povray3' (POVRay 3 -- under development), 'vrml' (VRML file). 
 Finally, several formats are provided to provide phi-psi data for 
 listing or for 'phipsi' (phi-psi data as an annotated list with cis 
 omegas), 'ramachan' and 'RDF' and 'RamachandranDataFile' (phi-psi 
 data as columns of numbers for gnuplot), 'RPP' and 
 'RamachandranPrinterPlot' (phi-psi data as a printer plot). 

 The distinction between this command and the RasMol 'save' command 
 has been dropped. The only difference is that without a format 
 specifier the 'save' command generates a 'PDB' file and the 'write' 
 command generates a 'GIF' image. 

3 Zap
 Deletes the contents of the current database and resets parameter 
 variables to their initial default state. 

3 Zoom
 Change the magnification of the currently displayed image. Boolean 
 parameters either magnify or reset the scale of current molecule. An 
 integer parameter specifies the desired magnification as a 
 percentage of the default scale. The minimum parameter value is 10; 
 the maximum parameter value is dependent upon the size of the 
 molecule being displayed. For medium sized proteins this is about 
 500. 

2 Set_Parameters
 RasMol has a number of internal parameters that may be modified 
 using the 'set' command. These parameters control a number of 
 program options such as rendering options and mouse button mappings. 

3 Ambient
 The RasMol 'ambient' parameter is used to control the amount of 
 ambient (or surrounding) light in the scene. The 'ambient' value 
 must be between 0 and 100. It controls the percentage intensity of 
 the darkest shade of an object. For a solid object, this is the 
 intensity of surfaces facing away from the light source or in 
 shadow. For depth-cued objects this is the intensity of objects 
 furthest from the viewer. 

 This parameter is commonly used to correct for monitors with 
 different "gamma values" (brightness), to change how light or dark a 
 hardcopy image appears when printed or to alter the feeling of depth 
 for wireframe or ribbon representations. 

3 Axes
 The RasMol 'axes' parameter controls the display of orthogonal 
 coordinate axes on the current display. The coordinate axes are 
 those used in the molecule data file, and the origin is the centre 
 of the molecule's bounding box. The 'set axes' command is similar to 
 the commands 'set boundbox' and 'set unitcell' that display the 
 bounding box and the crystallographic unit cell, respectively. 

3 Backfade
 The RasMol 'backfade' parameter is used to control backfade to the 
 specified background colour, rather than black. This is controlled 
 by the commands 'set backfade on' and 'set backfade off'. For 
 example, this may be used to generate depth-cued images that fade to 
 white, rather than black. 

3 Background
 The RasMol 'background' parameter is used to set the colour of the 
 "canvas" background. The colour may be given as either a colour name 
 or a comma separated triple of Red, Green, Blue (RGB) components 
 enclosed in square brackets. Typing the command 'help colours' will 
 give a list of the predefined colour names recognised by RasMol. 
 When running under X Windows, RasMol also recognises colours in the 
 X server's colour name database. 

 The command 'set background' is synonymous with the RasMol command 
 'background'. 

3 BondMode
 The RasMol 'set bondmode' command controls the mechanism used to 
 select individual bonds and modifies the display of bonded and 
 non-bonded atoms by subsequent 'wireframe' commands. 

 When using the 'select' and 'restrict' commands, a given bond will 
 be selected if i) the bondmode is 'or' and either of the connected 
 atoms is selected, or ii) the bondmode is 'and' and both atoms 
 connected by the bond are selected. Hence an individual bond may be 
 uniquely identified by using the command 'set bondmode and' and then 
 uniquely selecting the atoms at both ends. 

 The 'bondmode [all | none | not bonded]' commands add 'star 75' or 
 'spacefill 75' markers for the designated atoms to 'wireframe' 
 displays. Stars are used when the specified wireframe radius is 
 zero. 

3 Bonds
 The RasMol 'bonds' parameter is used to control display of double 
 and triple bonds as multiple lines or cylinders. Currently bond 
 orders are only read from MDL Mol files, Sybyl Mol2 format files, 
 Tripos Alchemy format files, CIF and mmCIF, and suitable PDB files. 
 Double (and triple) bonds are specified in some PDB files by 
 specifying a given bond twice (and three times) in CONECT records. 
 The command 'set bonds on' enables the display of bond orders, and 
 the command 'set bonds off' disables them. 

3 BoundBox
 The RasMol 'boundbox' parameter controls the display of the current 
 molecule's bounding box on the display. The bounding box is 
 orthogonal to the data file's original coordinate axes. The 'set 
 boundbox' command is similar to the commands 'set axes' and 'set 
 unitcell' that display orthogonal coordinate axes and the bounding 
 box, respectively. 

3 Cartoon
 The RasMol 'cartoon' parameter is used to control display of the 
 cartoon version of the 'ribbons' display. By default, the C-termini 
 of beta-sheets are displayed as arrow heads. This may be enabled and 
 disabled using the 'set cartoons <boolean>' command. The depth of 
 the cartoon may be adjusted using the 'cartoons <number>' command. 
 The 'set cartoons' command without any parameters returns these two 
 options to  their default values. 

3 CisAngle
 The RasMol 'cisangle' parameter controls the cutoff angle for 
 identifying cis peptide  bonds. If no value is given, the cutoff is 
 set to 90 degrees. 

3 Display
 This command controls the display mode within RasMol. By default, 
 'set display normal', RasMol displays the molecule in the 
 representation specified by the user. The command 'set display 
 selected' changes the display mode such that the molecule is 
 temporarily drawn so as to indicate currently selected portion of 
 the molecule. The user specified colour scheme and representation 
 remains unchanged. In this representation all selected atoms are 
 shown in yellow and all non selected atoms are shown in blue. The 
 colour of the background is also changed to a dark grey to indicate 
 the change of display mode. This command is typically only used by 
 external Graphical User Interfaces (GUIs). 

3 FontSize
 The RasMol 'set fontsize' command is used to control the size of the 
 characters that form atom labels. This value corresponds to the 
 height of the displayed character in pixels. The maximum value of 
 'fontsize' is 48 pixels, and the default value is 8 pixels high. 
 Fixed or proportional spacing may be selected by appending the "FS" 
 or "PS" modifiers, respectively. The default is "FS". To display 
 atom labels on the screen use the RasMol 'label' command and to 
 change the colour of displayed labels, use the 'colour labels' 
 command. 

3 FontStroke
 The RasMol 'set fontstroke' command is used to control the size of 
 the stroke width of the characters that form atom labels. This value 
 is the radius in pixels of cylinders used to form the strokes. The 
 special value of "0" is the default used for the normal single pixel 
 stroke width, which allows for rapid drawing and rotation of the 
 image. Non-zero values are provided to allow for more artistic atom 
 labels for publication at the expense of extra time in rendering the 
 image. 

 When wider strokes are used, a larger font size is recommend, e.g. 
 by using the RasMol 'set fontsize 24 PS' command, followed by 'set 
 fontstroke 2' 

 To display atom labels on the screen use the RasMol 'label' command, 
 and to change the colour of displayed labels use the 'colour labels' 
 command. 

3 HBonds
 The RasMol 'hbonds' parameter determines whether hydrogen bonds are 
 drawn between the donor and acceptor atoms of the hydrogen bond, 
 'set hbonds sidechain' or between the alpha carbon atoms of the 
 protein backbone and between the phosphorous atoms of the nucleic 
 acid backbone, 'set hbonds backbone'. The actual display of hydrogen 
 bonds is controlled by the 'hbonds' command. Drawing hydrogen bonds 
 between protein alpha carbons or nucleic acid phosphorous atoms is 
 useful when the rest of the molecule is shown in only a schematic 
 representation such as 'backbone', 'ribbons' or 'strands'. This 
 parameter is similar to the RasMol 'ssbonds' parameter. 

3 Hetero
 The RasMol 'hetero' parameter is used to modify the 'default' 
 behaviour of the RasMol 'select' command, i.e. the behaviour of 
 'select' without any parameters. When this value is 'false', the 
 default 'select' region does not include any heterogeneous atoms 
 (refer to the predefined set 'hetero' ). When this value is 'true', 
 the default 'select' region may contain hetero atoms. This parameter 
 is similar to the RasMol 'hydrogen' parameter which determines 
 whether hydrogen atoms should be included in the default set. If 
 both 'hetero' and 'hydrogen' are 'true', 'select' without any 
 parameters is equivalent to 'select all'. 

3 HourGlass
 The RasMol 'hourglass' parameter allows the user to enable and 
 disable the use of the 'hour glass' cursor used by RasMol to 
 indicate that the program is currently busy drawing the next frame. 
 The command 'set hourglass on' enables the indicator, whilst 'set 
 hourglass off' prevents RasMol from changing the cursor. This is 
 useful when spinning the molecule, running a sequence of commands 
 from a script file or using interprocess communication to execute 
 complex sequences of commands. In these cases a 'flashing' cursor 
 may be distracting. 

3 Hydrogen
 The RasMol 'hydrogen' parameter is used to modify the "default" 
 behaviour of the RasMol 'select' command, i.e. the behaviour of 
 'select' without any parameters. When this value is 'false', the 
 default 'select' region does not include any hydrogen, deuterium or 
 tritium atoms (refer to the predefined set 'hydrogen' ). When this 
 value is 'true', the default 'select' region may contain hydrogen 
 atoms. This parameter is similar to the RasMol 'hetero' parameter 
 which determines whether heterogeneous atoms should be included in 
 the default set. If both 'hydrogen' and 'hetero' are 'true', 
 'select' without any parameters is equivalent to 'select all'. 

3 Kinemage
 The RasMol 'set kinemage' command controls the amount of detail 
 stored in a Kinemage output file generated by the RasMol 'write 
 kinemage' command. The output kinemage files are intended to be 
 displayed by David Richardson's Mage program. 'set kinemage false', 
 the default, only stores the currently displayed representation in 
 the generated output file. The command 'set kinemage true', 
 generates a more complex Kinemage that contains both the wireframe 
 and backbone representations as well as the coordinate axes, 
 bounding box and crystal unit cell. 

3 Menus
 The RasMol 'set menus' command enables the canvas window's menu 
 buttons or menu bar. This command is typically only used by 
 graphical user interfaces or to create as large an image as possible 
 when using Microsoft Windows. 

3 Monitor
 The RasMol 'set monitor' command enables 'monitors'. The distance 
 monitor labels may be turned off with the command 'set monitor off', 
 and re-enabled with the command 'set monitor on'. 

3 Mouse
 The RasMol 'set mouse' command sets the rotation, translation, 
 scaling and zooming mouse bindings. The default value is 'rasmol' 
 which is suitable for two button mice (for three button mice the 
 second and third buttons are synonymous); X-Y rotation is controlled 
 by the first button, and X-Y translation by the second. Additional 
 functions are controlled by holding a modifier key on the keyboard. 
 [Shift] and the first button performs scaling, [shift] and the 
 second button performs Z-rotation, and [control] and the first mouse 
 button controls the clipping plane. The 'insight' and 'quanta' 
 options provide the same mouse bindings as other packages for 
 experienced users. 

3 Picking
 The RasMol 'set picking' series of commands affects how a user may 
 interact with a molecule displayed on the screen in RasMol. 

 Enabling/Disabling Atom Picking: Clicking on an atom with the mouse 
 results in identification and the display of its residue name, 
 residue number, atom name, atom serial number and chain in the 
 command window. This behavior may be disabled with the command 'set 
 picking none' and restored with the command 'set picking ident'. The 
 command 'set picking coord' adds the atomic coordinates of the atom 
 to the display. 

 Disabling picking, by using 'set picking off' is useful when 
 executing the 'pause' command in RasMol scripts as it prevents the 
 display of spurious message on the command line while the script is 
 suspended. 

 Measuring Distances, Angles and Torsions: Interactive measurement of 
 distances, angles and torsions is achieved using the commands: 'set 
 picking distance', 'set picking monitor', 'set picking angle' and 
 'set picking torsion', respectively. In these modes, clicking on an 
 atom results in it being identified on the rasmol command line. In 
 addition every atom picked increments a modulo counter such that in 
 distance mode, every second atom displays the distance (or distance 
 monitor) between this atom and the previous one. In angle mode, 
 every third atom displays the angle between the previous three atoms 
 and in torsion mode every fourth atom displays the torsion between 
 the last four atoms. By holding down the shift key while picking an 
 atom, this modulo counter is not incremented and allows, for 
 example, the distances of consecutive atoms from a fixed atom to be 
 displayed. See the 'monitor' command for how to control the display 
 of distance monitor lines and labels. 

 Labelling Atoms with the Mouse: The mouse may also be used to toggle 
 the display of an atom label on a given atom. The RasMol command 
 'set picking label' removes a label from a picked atom if it already 
 has one or displays a concise label at that atom position otherwise. 

 Centring Rotation with the Mouse: A molecule may be centred on a 
 specified atom position using the RasMol commands 'set picking 
 centre' or 'set picking center'. In this mode, picking an atom 
 causes all futher rotations to be about that point. 

3 Radius
 The RasMol 'set radius' command is used to alter the behaviour of 
 the RasMol 'dots' command depending upon the value of the 'solvent' 
 parameter. When 'solvent' is 'true', the 'radius' parameter controls 
 whether a true van der Waals' surface is generated by the 'dots' 
 command. If the value of 'radius' is anything other than zero, that 
 value is used as the radius of each atom instead of its true vdW 
 value. When the value of 'solvent' is 'true', this parameter 
 determines the 'probe sphere' (solvent) radius. The parameter may be 
 given as an integer in rasmol units or containing a decimal point in 
 Angstroms. The default value of this parameter is determined by the 
 value of 'solvent' and changing 'solvent' resets 'radius' to its new 
 default value. 

3 Shadow
 The RasMol 'set shadow' command enables and disables ray-tracing of 
 the currently rendered image. Currently only the spacefilling 
 representation is shadowed or can cast shadows. Enabling shadowing 
 will automatically disable the Z-clipping (slabbing) plane using the 
 command 'slab off'. Ray-tracing typically takes about several 
 seconds for a moderately sized protein. It is recommended that 
 shadowing be normally disabled whilst the molecule is being 
 transformed or manipulated, and only enabled once an appropiate 
 viewpoint is selected, to provide a greater impression of depth. 

3 SlabMode
 The RasMol 'slabmode' parameter controls the rendering method of 
 objects cut by the slabbing (z-clipping) plane. Valid slabmode 
 parameters are 

3 Solvent
 The RasMol 'set solvent' command is used to control the behaviour of 
 the RasMol 'dots' command. Depending upon the value of the 'solvent' 
 parameter, the 'dots' command either generates a van der Waals' or a 
 solvent accessible surface around the currently selected set of 
 atoms. Changing this parameter automatically resets the value of the 
 RasMol 'radius' parameter. The command 'set solvent false', the 
 default value, indicates that a van der Waals' surface should be 
 generated and resets the value of 'radius' to zero. The command 'set 
 solvent true' indicates that a 'Connolly' or 'Richards' solvent 
 accessible surface should be drawn and sets the 'radius' parameter, 
 the solvent radius, to 1.2 Angstroms (or 300 RasMol units). 

3 Specular
 The RasMol 'set specular' command enables and disables the display 
 of specular highlights on solid objects drawn by RasMol. Specular 
 highlights appear as white reflections of the light source on the 
 surface of the object. The current RasMol implementation uses an 
 approximation function to generate this highlight. 

 The specular highlights on the surfaces of solid objects may be 
 altered by using the specular reflection coefficient, which is 
 altered using the RasMol 'set specpower' command. 

3 SpecPower
 The 'specpower' parameter determines the shininess of solid objects 
 rendered by RasMol. This value between 0 and 100 adjusts the 
 reflection coefficient used in specular highlight calculations. The 
 specular highlights are enabled and disabled by the RasMol 'set 
 specular' command. Values around 20 or 30 produce plastic looking 
 surfaces. High values represent more shiny surfaces such as metals, 
 while lower values produce more diffuse/dull surfaces. 

3 SSBonds
 The RasMol 'ssbonds' parameter determines whether disulphide bridges 
 are drawn between the sulphur atoms in the sidechain (the default) 
 or between the alpha carbon atoms in the backbone of the cysteines 
 residues. The actual display of disulphide bridges is controlled by 
 the 'ssbonds' command. Drawing disulphide bridges between alpha 
 carbons is useful when the rest of the protein is shown in only a 
 schematic representation such as 'backbone', 'ribbons' or 'strands'. 
 This parameter is similar to the RasMol 'hbonds' parameter. 

3 Stereo
 The RasMol 'set stereo' parameter controls the separation between 
 the left and right images. Turning stereo on and off doesn't 
 reposition the centre of the molecule. 

 Stereo viewing of a molecule may be turned on (and off) either by 
 selecting 'Stereo' from the 'Options' menu, or by typing the 
 commands 'stereo on' or 'stereo off'. 

 The separation angle between the two views may be adjusted with the 
 'set stereo [-] <number>' command, where positive values result in 
 crossed eye viewing and negative values in relaxed (wall-eyed) 
 viewing. Currently, stereo viewing is not supported in 'vector 
 PostScript' output files. 

3 Strands
 The RasMol 'strands' parameter controls the number of parallel 
 strands that are displayed in the ribbon representations of 
 proteins. The permissible values for this parameter are 1, 2, 3, 4, 
 5 and 9. The default value is 5. The number of strands is constant 
 for all ribbons being displayed. However, the ribbon width (the 
 separation between strands) may be controlled on a residue by 
 residue basis using the RasMol 'ribbons' command. 

3 Transparent
 The RasMol 'transparent' parameter controls the writing of 
 transparent GIFs by the 'write gif <filename>' command. This may be 
 controlled by the 'set transparent on' and 'set transparent off' 
 commands. 

3 UnitCell
 The RasMol 'unitcell' parameter controls the display of the 
 crystallographic unit cell on the current display. The crystal cell 
 is only enabled if the appropriate crystal symmetry information is 
 contained in the PDB, CIF or mmCIF data file. The RasMol command 
 'show symmetry' display details of the crystal's space group and 
 unit cell axes. The 'set unitcell' command is similar to the 
 commands 'set axes' and 'set boundbox' that display orthogonal 
 coordinate axes and the bounding box, respectively. 

3 VectPS
 The RasMol 'vectps' parameter is use to control the way in which the 
 RasMol 'write' command generates vector PostScript output files. The 
 command 'set vectps on' enables the use of black outlines around 
 spheres and cylinder bonds producing "cartoon-like" high resolution 
 output. However, the current implementation of RasMol incorrectly 
 cartoons spheres that are intersected by more than one other sphere. 
 Hence "ball and stick" models are rendered correctly but not large 
 spacefilling spheres models. Cartoon outlines can be disabled, the 
 default, by the command 'set vectps off'. 

3 Write
 The RasMol 'write' parameter controls the use of the 'save' and 
 'write' commands within scripts, but it may only be executed from 
 the command line. By default, this value is 'false', prohibiting the 
 generation of files in any scripts executed at start-up (such as 
 those launched from a WWW browser). However, animators may start up 
 RasMol interactively: type 'set write on' and then execute a script 
 to generate each frame using the source command. 

2 Atom_Expressions
 RasMol atom expressions uniquely identify an arbitrary group of 
 atoms within a molecule. Atom expressions are composed of either 
 primitive expressions, predefined sets, comparison operators, 
 'within' expressions, or logical (boolean) combinations of the above 
 expression types. 

 The logical operators allow complex queries to be constructed out of 
 simpler ones using the standard boolean connectives 'and', 'or' and 
 'not'. These may be abbreviated by the symbols respectively. 
 Parentheses (brackets) may be used to alter the precedence of the 
 operators. For convenience, a comma may also be used for boolean 
 disjunction. 

 The atom expression is evaluated for each atom, hence 'protein and 
 backbone' selects protein backbone atoms, not the protein and 
 [nucleic] acid backbone atoms! 

Examples:    backbone and not helix
             within( 8.0, ser70 )
             not (hydrogen or hetero)
             not *.FE and hetero
             8, 12, 16, 20-28
             arg, his, lys


3 Primitive_Expressions
 RasMol primitive expressions are the fundamental building blocks of 
 atom expressions. There are two types of primitive expression. The 
 first type is used to identify a given residue number or range of 
 residue numbers. A single residue is identified by its number 
 (position in the sequence), and a range is specified by lower and 
 upper bounds separated by a hyphen character. For example 'select 
 5,6,7,8' is also 'select 5-8'. Note that this selects the given 
 residue numbers in all macromolecule chains. 

 The second type of primitive expression specifies a sequence of 
 fields that must match for a given atom. The first part specifies a 
 residue (or group of residues) and an optional second part specifies 
 the atoms within those residues. The first part consists of a 
 residue name, optionally followed by a residue number and/or chain 
 identifier. 

 The second part consists of a period character followed by an atom 
 name. An atom name may be up to four alphabetic or numeric 
 characters. An optional semicolon followed by an alternate 
 conformation identifier may be appended. An optional slash followed 
 by a model number may also be appended. 

 An asterisk may be used as a wild card for a whole field and a 
 question mark as a single character wildcard. 

3 Comparison_Operators
 Parts of a molecule may also be distinguished using equality, 
 inequality and ordering operators on their properties. The format of 
 such comparison expression is a property name, followed by a 
 comparison operator and then an integer value. 

 The atom properties that may be used in RasMol are 'atomno' for the 
 atom serial number, 'elemno' for the atom's atomic number (element), 
 'resno' for the residue number, 'radius' for the spacefill radius in 
 RasMol units (or zero if not represented as a sphere) and 
 'temperature' for the PDB isotropic temperature value. 

 The equality operator is denoted either The inequality operator as 
 either The ordering operators are for less than, for less than or 
 equal to, for greater than, and for greater than or equal to. 

3 Within_Expressions
 A RasMol 'within' expression allows atoms to be selected on their 
 proximity to another set of atoms. A 'within' expression takes two 
 parameters separated by a comma and surrounded by parentheses. The 
 first argument is an integer value called the "cut-off" distance of 
 the within expression and the second argument is any valid atom 
 expression. The cut-off distance is expressed in either integer 
 RasMol units or Angstroms containing a decimal point. An atom is 
 selected if it is within the cut-off distance of any of the atoms 
 defined by the second argument. This allows complex expressions to 
 be constructed containing nested 'within' expressions. 

 For example, the command 'select within(3.2,backbone)' selects any 
 atom within a 3.2 Angstrom radius of any atom in a protein or 
 nucleic acid backbone. 'Within' expressions are particularly useful 
 for selecting the atoms around an active site. 

2 Predefined_Sets
 RasMol atom expressions may contain predefined sets. These sets are 
 single keywords that represent portions of a molecule of interest. 
 Predefined sets are often abbreviations of primitive atom 
 expressions. In some cases the use of predefined sets allows 
 selection of areas of a molecule that could not otherwise be 
 distinguished. A list of the currently predefined sets is given 
 below. In addition to the sets listed here, RasMol also treats 
 element names (and their plurals) as predefined sets containing all 
 atoms of that element type, i.e. the command 'select oxygen' is 
 equivalent to the command 'select elemno=8'. 

3 AT_Set
 This set contains the atoms in the complementary nucleotides 
 adenosine and thymidine (A and T, respectively). All nucleotides are 
 classified as either the set 'at' or the set 'cg' This set is 
 equivalent to the RasMol atom expressions "a,t", and "nucleic and 
 not cg". 

3 Acidic_Set
 The set of acidic amino acids. These are the residue types Asp and 
 Glu. All amino acids are classified as either 'acidic', 'basic' 'or' 
 'neutral'. This set is equivalent to the RasMol atom expressions 
 "asp, glu" and "amino and not (basic or neutral)". 

3 Acyclic_Set
 The set of atoms in amino acids not containing a cycle or ring. All 
 amino acids are classified as either 'cyclic' or 'acyclic'. This set 
 is equivalent to the RasMol atom expression "amino and not cyclic". 

3 Aliphatic_Set
 This set contains the aliphatic amino acids. These are the amino 
 acids Ala, Gly, Ile, Leu and Val. This set is equivalent to the 
 RasMol atom expression "ala, gly, ile, leu, val". 

3 Alpha_Set
 The set of alpha carbons in the protein molecule. This set is 
 approximately equivalent to the RasMol atom expression "*.CA". This 
 command should not be confused with the predefined set 'helix' which 
 contains the atoms in the amino acids of the protein's alpha 
 helices. 

3 Amino_Set
 This set contains all the atoms contained in amino acid residues. 
 This is useful for distinguishing the protein from the nucleic acid 
 and heterogeneous atoms in the current molecule database. 

3 Aromatic_Set
 The set of atoms in amino acids containing aromatic rings. These are 
 the amino acids His, Phe, Trp and Tyr. Because they contain aromatic 
 rings all members of this set are member of the predefined set 
 'cyclic'. This set is equivalent to the RasMol atom expressions 
 "his, phe, trp, tyr" and "cyclic and not pro". 

3 Backbone_Set
 This set contains the four atoms of each amino acid that form the 
 polypeptide N-C-C-O backbone of proteins, and the atoms of the sugar 
 phosphate backbone of nucleic acids. Use the RasMol predefined sets 
 'protein' and 'nucleic' to distinguish between the two forms of 
 backbone. Atoms in nucleic acids and proteins are either 'backbone' 
 or 'sidechain'. This set is equivalent to the RasMol expression 
 "(protein or nucleic) and not sidechain". 

 The predefined set 'mainchain' is synonymous with the set 
 'backbone'. 

3 Basic_Set
 The set of basic amino acids. These are the residue types Arg, His 
 and Lys. All amino acids are classified as either 'acidic', 'basic' 
 or 'neutral'. This set is equivalent to the RasMol atom expressions 
 "arg, his, lys" and "amino and not (acidic or neutral)". 

3 Bonded_Set
 This set contain all the atoms in the current molecule database that 
 are bonded to at least one other atom. 

3 Buried_Set
 This set contains the atoms in those amino acids that tend (prefer) 
 to be buried inside protein, away from contact with solvent 
 molecules. This set refers to the amino acids preference and not the 
 actual solvent accessibility for the current protein. All amino 
 acids are classified as either 'surface' or 'buried'. This set is 
 equivalent to the RasMol atom expression "amino and not surface". 

3 CG_Set
 This set contains the atoms in the complementary nucleotides 
 cytidine and guanosine (C and G, respectively). All nucleotides are 
 classified as either the set 'at' or the set 'cg' This set is 
 equivalent to the RasMol atom expressions "c,g" and "nucleic and not 
 at". 

3 Charged_Set
 This set contains the charged amino acids. These are the amino acids 
 that are either 'acidic' or 'basic'. Amino acids are classified as 
 being either 'charged' or 'neutral'. This set is equivalent to the 
 RasMol atom expressions "acidic or basic" and "amino and not 
 neutral". 

3 Cyclic_Set
 The set of atoms in amino acids containing a cycle or rings. All 
 amino acids are classified as either 'cyclic' or 'acyclic'. This set 
 consists of the amino acids His, Phe, Pro, Trp and Tyr. The members 
 of the predefined set 'aromatic' are members of this set. The only 
 cyclic but non-aromatic amino acid is proline. This set is 
 equivalent to the RasMol atom expressions "his, phe, pro, trp, tyr" 
 and "aromatic or pro" and "amino and not acyclic". 

3 Cystine_Set
 This set contains the atoms of cysteine residues that form part of a 
 disulphide bridge, i.e. half cystines. RasMol automatically 
 determines disulphide bridges, if neither the predefined set 
 'cystine' nor the RasMol 'ssbonds' command have been used since the 
 molecule was loaded. The set of free cysteines may be determined 
 using the RasMol atom expression "cys and not cystine". 

3 Helix_Set
 This set contains all atoms that form part of a protein alpha helix 
 as determined by either the PDB file author or Kabsch and Sander's 
 DSSP algorithm. By default, RasMol uses the secondary structure 
 determination given in the PDB file if it exists. Otherwise, it uses 
 the DSSP algorithm as used by the RasMol 'structure' command. 

 This predefined set should not be confused with the predefined set 
 'alpha' which contains the alpha carbon atoms of a protein. 

3 Hetero_Set
 This set contains all the heterogeneous atoms in the molecule. These 
 are the atoms described by HETATM entries in the PDB file. These 
 typically contain water, cofactors and other solvents and ligands. 
 All 'hetero' atoms are classified as either 'ligand' or 'solvent' 
 atoms. These heterogeneous 'solvent' atoms are further classified as 
 either 'water' or 'ions'. 

3 Hydrogen_Set
 This predefined set contains all the hydrogen, deuterium and tritium 
 atoms of the current molecule. This predefined set is equivalent to 
 the RasMol atom expression "elemno=1". 

3 Hydrophobic_Set
 This set contains all the hydrophobic amino acids. These are the 
 amino acids Ala, Leu, Val, Ile, Pro, Phe, Met and Trp. All amino 
 acids are classified as either 'hydrophobic' or 'polar'. This set is 
 equivalent to the RasMol atom expressions "ala, leu, val, ile, pro, 
 phe, met, trp" and "amino and not polar". 

3 Ions_Set
 This set contains all the heterogeneous phosphate and sulphate ions 
 in the current molecule data file. A large number of these ions are 
 sometimes associated with protein and nucleic acid structures 
 determined by X-ray crystallography. These atoms tend to clutter an 
 image. All 'hetero' atoms are classified as either 'ligand' or 
 'solvent' atoms. All 'solvent' atoms are classified as either 
 'water' or 'ions'. 

3 Large_Set
 All amino acids are classified as either 'small', 'medium' or 
 'large'. This set is equivalent to the RasMol atom expression "amino 
 and not (small or medium)". 

3 Ligand_Set
 This set contains all the heterogeneous cofactor and ligand moieties 
 that are contained in the current molecule data file. This set is 
 defined to be all 'hetero' atoms that are not 'solvent' atoms. Hence 
 this set is equivalent to the RasMol atom expression "hetero and not 
 solvent". 

3 Medium_Set
 All amino acids are classified as either 'small', 'medium' or 
 'large'. This set is equivalent to the RasMol atom expression "amino 
 and not (large or small)". 

3 Neutral_Set
 The set of neutral amino acids. All amino acids are classified as 
 either 'acidic', 'basic' or 'neutral'. This set is equivalent to the 
 RasMol atom expression "amino and not (acidic or basic)". 

3 Nucleic_Set
 The set of all atoms in nucleic acids, which consists of the four 
 nucleotide bases adenosine, cytidine, guanosine and thymidine (A, C, 
 G and T, respectively). All neucleotides are classified as either 
 'purine' or 'pyrimidine'. This set is equivalent to the RasMol atom 
 expressions "a,c,g,t" and "purine or pyrimidine". The symbols for 
 RNA nucleotides (U, +U, I, 1MA, 5MC, OMC, 1MG, 2MG, M2G, 7MG, OMG, 
 YG, H2U, 5MU, and PSU) are also recognized as members of this set. 

3 Polar_Set
 This set contains the polar amino acids. All amino acids are 
 classified as either 'hydrophobic' or 'polar'. This set is 
 equivalent to the RasMol atom expression "amino and not 
 hydrophobic". 

3 Protein_Set
 The set of all atoms in proteins. This consists of the RasMol 
 predefined set 'amino' and common post-translation modifications. 

3 Purine_Set
 The set of purine nucleotides. These are the bases adenosine and 
 guanosine (A and G, respectively). All nucleotides are either 
 'purines' or 'pyrimidines'. This set is equivalent to the RasMol 
 atom expressions "a,g" and "nucleic and not pyrimidine". 

3 Pyrimidine_Set
 The set of pyrimidine nucleotides. These are the bases cytidine and 
 thymidine (C and T, respectively). All nucleotides are either 
 'purines' or 'pyrimidines'. This set is equivalent to the RasMol 
 atom expressions "c,t" and "nucleic and not purine". 

3 Selected_Set
 This set contains the set of atoms in the currently selected region. 
 The currently selected region is defined by the preceding 'select' 
 or 'restrict' command and not the atom expression containing the 
 'selected' keyword. 

3 Sheet_Set
 This set contains all atoms that form part of a protein beta sheet 
 as determined by either the PDB file author or Kabsch and Sander's 
 DSSP algorithm. By default, RasMol uses the secondary structure 
 determination given in the PDB file if it exists. Otherwise, it uses 
 the DSSP algorithm as used by the RasMol 'structure' command. 

3 Sidechain_Set
 This set contains the functional sidechains of any amino acids and 
 the base of each nucleotide. These are the atoms not part of the 
 polypeptide N-C-C-O backbone of proteins or the sugar phosphate 
 backbone of nucleic acids. Use the RasMol predefined sets 'protein' 
 and 'nucleic' to distinguish between the two forms of sidechain. 
 Atoms in nucleic acids and proteins are either 'backbone' or 
 'sidechain'. This set is equivalent to the RasMol expression 
 "(protein or nucleic) and not backbone". 

3 Small_Set
 All amino acids are classified as either 'small', 'medium' or 
 'large'. This set is equivalent to the RasMol atom expression "amino 
 and not (medium or large)". 

3 Solvent_Set
 This set contains the solvent atoms in the molecule coordinate file. 
 These are the heterogeneous water molecules, phosphate and sulphate 
 ions. All 'hetero' atoms are classified as either 'ligand' or 
 'solvent' atoms. All 'solvent' atoms are classified as either 
 'water' or 'ions'. This set is equivalent to the RasMol atom 
 expressions "hetero and not ligand" and "water or ions". 

3 Surface_Set
 This set contains the atoms in those amino acids that tend (prefer) 
 to be on the surface of proteins, in contact with solvent molecules. 
 This set refers to the amino acids preference and not the actual 
 solvent accessibility for the current protein. All amino acids are 
 classified as either 'surface' or 'buried'. This set is equivalent 
 to the RasMol atom expression "amino and not buried". 

3 Turn_Set
 This set contains all atoms that form part of a protein turns as 
 determined by either the PDB file author or Kabsch and Sander's DSSP 
 algorithm. By default, RasMol uses the secondary structure 
 determination given in the PDB file if it exists. Otherwise, it uses 
 the DSSP algorithm as used by the RasMol 'structure' command. 

3 Water_Set
 This set contains all the heterogeneous water molecules in the 
 current database. A large number of water molecules are sometimes 
 associated with protein and nucleic acid structures determined by 
 X-ray crystallography. These atoms tend to clutter an image. All 
 'hetero' atoms are classified as either 'ligand' or 'solvent' atoms. 
 The 'solvent' atoms are further classified as either 'water' or 
 'ions'. 

3 Summary
 The table below summarises RasMol's classification of the common 
 amino acids. 

2 Colours_Schemes
 The RasMol 'colour' command allows different objects (such as atoms, 
 bonds and ribbon segments) to be given a specified colour. Typically 
 this colour is either a RasMol predefined colour name or an RGB 
 triple. Additionally RasMol also supports 'alt', 'amino', 'chain', 
 'charge', 'cpk', 'group', 'model', 'shapely', 'structure', 
 'temperature' or 'user' colour schemes for atoms, and 'hbond type' 
 colour scheme for hydrogen bonds and 'electrostatic potential' 
 colour scheme for dot surfaces. The 24 currently predefined colour 
 names are listed below with their corresponding RGB triplet. 

    Black        [0,0,0]            Orange       [255,165,0]
    Blue         [0,0,255]          Pink         [255,101,117]
    BlueTint     [175,214,255]      PinkTint     [255,171,187]
    Brown        [175,117,89]       Purple       [160,32,240]
    Cyan         [0,255,255]        Red          [255,0,0]
    Gold         [255,156,0]        RedOrange    [255,69,0]
    Grey         [125,125,125]      SeaGreen     [0,250,109]
    Green        [0,255,0]          SkyBlue      [58,144,255]
    GreenBlue    [46,139,87]        Violet       [238,130,238]
    GreenTint    [152,255,179]      White        [255,255,255]
    HotPink      [255,0,101]        Yellow       [255,255,0]
    Magenta      [255,0,255]        YellowTint   [246,246,117]


 If you frequently wish to use a colour not predefined, you can write 
 a one-line script. For example, if you make the file 'grey.col' 
 containing the line, 'colour [180,180,180] #grey', then the command 
 'script grey.col' colours the currently selected atom set grey. 

3 Alt_Colours
 The RasMol 'alt' (Alternate Conformer) colour scheme codes the base 
 structure with one colour and applies a limited number of colours to 
 each alternate conformer. In a RasMol built for 8-bit color systems, 
 4 colours are allowed for alternate conformers. Otherwise, 8 colours 
 are available. 

3 Amino_Colours
 The RasMol 'amino' colour scheme colours amino acids according to 
 traditional amino acid properties. The purpose of colouring is to 
 identify amino acids in an unusual or surprising environment. The 
 outer parts of a protein that are polar are visible (bright) colours 
 and non-polar residues darker. Most colours are hallowed by 
 tradition. This colour scheme is similar to the 'shapely' scheme. 

   ASP,GLU Bright Red [230,10,10]     CYS,MET     Yellow [230,230,0]
   LYS,ARG Blue       [20,90,255]     SER,THR     Orange [250,150,0]
   PHE,TYR Mid Blue   [50,50,170]     ASN,GLN     Cyan   [0,220,220]
   GLY     Light Grey [235,235,235]   LEU,VAL,ILE Green  [15,130,15]
   ALA     Dark Grey  [200,200,200]   TRP         Purple [180,90,180]
   HIS     Pale Blue  [130,130,210]   PRO         Flesh  [220,150,130]
   Others  Tan        [190,160,110]


3 Chain_Colours
 The RasMol 'chain' colour scheme assigns each macromolecular chain a 
 unique colour. This colour scheme is particularly useful for 
 distinguishing the parts of multimeric structure or the individual 
 'strands' of a DNA chain. 'Chain' can be selected from the RasMol 
 'Colours' menu. 

3 Charge_Colours
 The RasMol 'charge' colour scheme colour codes each atom according 
 to the charge value stored in the input file (or beta factor field 
 of PDB files). High values are coloured in blue (positive) and lower 
 values coloured in red (negative). Rather than use a fixed scale 
 this scheme determines the maximum and minimum values of the 
 charge/temperature field and interpolates from red to blue 
 appropriately. Hence, green cannot be assumed to be 'no net charge' 
 charge. 

 The difference between the 'charge' and 'temperature' colour schemes 
 is that increasing temperature values proceed from blue to red, 
 whereas increasing charge values go from red to blue. 

 If the charge/temperature field stores reasonable values it is 
 possible to use the RasMol 'colour dots potential' command to colour 
 code a dot surface (generated by the 'dots' command) by 
 electrostatic potential. 

3 CPK_Colours
 The RasMol 'cpk' colour scheme is based upon the colours of the 
 popular plastic spacefilling models which were developed by Corey, 
 Pauling and later improved by Kultun. This colour scheme colours 
 'atom' objects by the atom (element) type. This is the scheme 
 conventionally used by chemists. The assignment of the most commonly 
 used element types to colours is given below. 

 The assignment of element type to colours is given below. 

    Carbon       light grey       Chlorine         green
    Oxygen       red              Bromine, Zinc    brown
    Hydogen      white            Sodium           blue
    Nitrogen     light blue       Iron             orange
    Sulphur      yellow           Magnesium        forest green
    Phosphorous  orange           Calcium          dark grey
                                  Unknown          deep pink


3 Group_Colours
 The RasMol 'group' colour scheme colour codes residues by their 
 position in a macromolecular chain. Each chain is drawn as a smooth 
 spectrum from blue through green, yellow and orange to red. Hence 
 the N terminus of proteins and 5' terminus of nucleic acids are 
 coloured red and the C terminus of proteins and 3' terminus of 
 nucleic acids are drawn in blue. If a chain has a large number of 
 heterogeneous molecules associated with it, the macromolecule may 
 not be drawn in the full 'range' of the spectrum. 'Group' can be 
 selected from the RasMol 'Colours' menu. 

 If a chain has a large number of heterogeneous molecules associated 
 with it, the macromolecule may not be drawn in the full range of the 
 spectrum. When RasMol performs group coloring it decides the range 
 of colors it uses from the residue numbering given in the PDB file. 
 Hence the lowest residue number is displayed in blue and the highest 
 residue number is displayed as red. Unfortunately, if a PDB file 
 contains a large number of heteroatoms, such as water molecules, 
 that occupy the high residue numbers, the protein is displayed in 
 the blue-green end of the spectrum and the waters in the yellow-red 
 end of the spectrum. This is aggravated by there typically being 
 many more water molecules than amino acid residues. The solution to 
 this problem is to use the command 'set hetero off' before applying 
 the group color scheme. This can also be achieved by toggling 
 'Hetero Atoms' on the 'Options' menu before selecting 'Group' on the 
 'Colour' menu. This command instructs RasMol to only use non-hetero 
 residues in the group color scaling. 

3 NMR_Model_Colours
 The RasMol 'model' colour scheme codes each NMR model with a 
 distinct colour. The NMR model number is taken as a numeric value. 
 High values are coloured in blue and lower values coloured in red. 
 Rather than use a fixed scale this scheme determines the maximum 
 value of the NMR model number and interpolates from red to blue 
 appropriately. 

3 Shapely_Colours
 The RasMol 'shapely' colour scheme colour codes residues by amino 
 acid property. This scheme is based upon Bob Fletterick's "Shapely 
 Models". Each amino acid and nucleic acid residue is given a unique 
 colour. The 'shapely' colour scheme is used by David Bacon's 
 Raster3D program. This colour scheme is similar to the 'amino' 
 colour scheme. 

ALA      Medium Green  [140,255,140]   GLY      White         [255,255,255]
LEU      Olive Green   [ 69, 94, 69]   SER      Medium Orange [255,112, 66]
VAL      Light Purple  [255,140,255]   THR      Dark Orange   [184, 76,  0]
LYS      Royal Blue    [ 71, 71,184]   ASP      Dark Rose     [160,  0, 66]
ILE      Dark Green    [ 0,  76,  0]   ASN      Light Salmon  [255,124,112]
GLU      Dark Brown    [102,  0,  0]   PRO      Dark Grey     [ 82, 82, 82]
ARG      Dark Blue     [  0,  0,124]   PHE      Olive Grey    [ 83, 76, 66]
GLN      Dark Salmon   [255, 76, 76]   TYR      Medium Brown  [140,112, 76]
HIS      Medium Blue   [112,112,255]   CYS      Medium Yellow [255,255,112]
MET      Light Brown   [184,160, 66]   TRP      Olive Brown   [ 79, 70,  0]
ASX,GLX,PCA,HYP
         Medium Purple [255,  0,255]

A        Light Blue    [160,160,255]   C        Light Orange  [255,140, 75]
G        Medium Salmon [255,112,112]   T        Light Green   [160,255,160]

Backbone Light Grey    [184,184,184]   Special  Dark Purple   [ 94, 0, 94]
Default  Medium Purple [255, 0,255]


3 Structure_Colours
 The RasMol 'structure' colour scheme colours the molecule by protein 
 secondary structure. Alpha helices are coloured magenta, 
 [240,0,128], beta sheets are coloured yellow, [255,255,0], turns are 
 coloured pale blue, [96,128,255] and all other residues are coloured 
 white. The secondary structure is either read from the PDB file 
 (HELIX, SHEET and TURN records), if available, or determined using 
 Kabsch and Sander's DSSP algorithm. The RasMol 'structure' command 
 may be used to force DSSP's structure assignment to be used. 

3 Temperature_Colours
 The RasMol 'temperature' colour scheme colour codes each atom 
 according to the anisotropic temperature (beta) value stored in the 
 PDB file. Typically this gives a measure of the mobility/uncertainty 
 of a given atom's position. High values are coloured in warmer (red) 
 colours and lower values in colder (blue) colours. This feature is 
 often used to associate a "scale" value [such as amino acid 
 variability in viral mutants] with each atom in a PDB file, and 
 colour the molecule appropriately. 

 The difference between the 'temperature' and 'charge' colour schemes 
 is that increasing temperature values proceed from blue to red, 
 whereas increasing charge values go from red to blue. 

3 User_Colours
 The RasMol 'user' colour scheme allows RasMol to use the colour 
 scheme stored in the PDB file. The colours for each atom are stored 
 in COLO records placed in the PDB data file. This convention was 
 introduced by David Bacon's Raster3D program. 

3 HBond_Type_Colours
 The RasMol 'type' colour scheme applies only to hydrogen bonds, 
 hence is used in the command 'colour hbonds type'. This scheme 
 colour codes each hydrogen bond according to the distance along a 
 protein chain between hydrogen bond donor and acceptor. This 
 schematic representation was introduced by Belhadj-Mostefa and 
 Milner-White. This representation gives a good insight into protein 
 secondary structure (hbonds forming alpha helices appear red, those 
 forming sheets appear yellow and those forming turns appear 
 magenta). 

      Offset    Colour    Triple
        +2      white     [255,255,255]
        +3      magenta   [255,0,255]
        +4      red       [255,0,0]
        +5      orange    [255,165,0]
        -3      cyan      [0,255,255]
        -4      green     [0,255,0]
      default   yellow    [255,255,0]


3 Potential_Colours
 The RasMol 'potential' colour scheme applies only to dot surfaces, 
 hence is used in the command 'colour dots potential'. This scheme 
 colours each currently displayed dot by the electrostatic potential 
 at that point in space. This potential is calculated using Coulomb's 
 law taking the temperature/charge field of the input file to be the 
 charge assocated with that atom. This is the same interpretation 
 used by the 'colour charge' command. Like the 'charge' colour scheme 
 low values are blue/white and high values are red. 

     25 < V          red       [255,0,0]
     10 < V <  25    orange    [255,165,0]
      3 < V <  10    yellow    [255,255,0]
      0 < V <   3    green     [0,255,0]
     -3 < V <   0    cyan      [0,255,255]
    -10 < V <   3    blue      [0,0,255]
    -25 < V < -10    purple    [160,32,240]
          V < -25    white     [255,255,255]


3 Amino_Acid_Codes
 The following table lists the names, single letter and three letter 
 codes of each of the amino acids. 

3 Booleans
 A boolean parameter is a truth value. Valid boolean values are 
 'true' and 'false', and their synonyms 'on' and 'off'. Boolean 
 parameters are commonly used by RasMol to either enable or disable a 
 representation or option. 

2 File Formats


3 Protein_Data_Bank_Files
 If you do not have the PDB documentation, you may find the following 
 summary of the PDB file format useful. The Protein Data Bank is a 
 computer-based archival database for macromolecular structures. The 
 database was established in 1971 by Brookhaven National Laboratory, 
 Upton, New York, as a public domain repository for resolved 
 crystallographic structures. The Bank uses a uniform format to store 
 atomic coordinates and partial bond connectivities as derived from 
 crystallographic studies. In 1999 the Protein Data Bank moved to the 
 Research Collaboratory for Structural Biology. 

 PDB file entries consist of records of 80 characters each. Using the 
 punched card analogy, columns 1 to 6 contain a record-type 
 identifier, the columns 7 to 70 contain data. In older entries, 
 columns 71 to 80 are normally blank, but may contain sequence 
 information added by library management programs. In new entries 
 conforming to the 1996 PDB format, there is other information in 
 those columns. The first four characters of the record identifier 
 are sufficient to identify the type of record uniquely, and the 
 syntax of each record is independent of the order of records within 
 any entry for a particular macromolecule. 

 The only record types that are of major interest to the RasMol 
 program are the ATOM and HETATM records which describe the position 
 of each atom. ATOM/HETATM records contain standard atom names and 
 residue abbreviations, along with sequence identifiers, coordinates 
 in Angstrom units, occupancies and thermal motion factors. The exact 
 details are given below as a FORTRAN format statement. The "fmt" 
 column indicates use of the field in all PDB formats, in the 1992 
 and earlier formats or in the 1996 and later formats. 

 Residues occur in order starting from the N-terminal residue for 
 proteins and 5'-terminus for nucleic acids. If the residue sequence 
 is known, certain atom serial numbers may be omitted to allow for 
 future insertion of any missing atoms. Within each residue, atoms 
 are ordered in a standard manner, starting with the backbone 
 (N-C-C-O for proteins) and proceeding in increasing remoteness from 
 the alpha carbon, along the side chain. 

 HETATM records are used to define post-translational modifications 
 and cofactors associated with the main molecule. TER records are 
 interpreted as breaks in the main molecule's backbone. 

 If present, RasMol also inspects HEADER, COMPND, HELIX, SHEET, TURN, 
 CONECT, CRYST1, SCALE, MODEL, ENDMDL, EXPDTA and END records. 
 Information such as the name, database code, revision date and 
 classification of the molecule are extracted from HEADER and COMPND 
 records, initial secondary structure assignments are taken from 
 HELIX, SHEET and TURN records, and the end of the file may be 
 indicated by an END record. 

3 RasMol_Interpretation_of_PDB_fields
 Atoms located at 9999.000, 9999.000, 9999.000 are assumed to be 
 Insight pseudo atoms and are ignored by RasMol. Atom names beginning 
 ' Q' are also assumed to be pseudo atoms or position markers. 

 When a data file contains an NMR structure, multiple conformations 
 may be placed in a single PDB file delimited by pairs of MODEL and 
 ENDMDL records. RasMol displays all the NMR models contained in the 
 file. 

 Residue names "CSH", "CYH" and "CSM" are considered pseudonyms for 
 cysteine "CYS". Residue names "WAT", "H20", "SOL" and "TIP" are 
 considered pseudonyms for water "HOH". The residue name "D20" is 
 consider heavy water "DOD". The residue name "SUL" is considered a 
 sulphate ion "SO4". The residue name "CPR" is considered to be 
 cis-proline and is translated as "PRO". The residue name "TRY" is 
 considered a pseudonym for tryptophan "TRP". 

 RasMol uses the HETATM fields to define the sets hetero, water, 
 solvent and ligand. Any group with the name "HOH", "DOD", "SO4" or 
 "PO4" (or aliased to one of these names by the preceding rules) is 
 considered a solvent and is considered to be defined by a HETATM 
 field. 

 RasMol only respects CONECT connectivity records in PDB files 
 containing fewer than 256 atoms. This is explained in more detail in 
 the section on determining molecule connectivity. CONECT records 
 that define a bond more than once are interpreted as specifying the 
 bond order of that bond, i.e. a bond specified twice is a double 
 bond and a bond specified three (or more) times is a triple bond. 
 This is not a standard PDB feature. 

3 PDB_Colour_Scheme_Specification
 RasMol also accepts the supplementary COLO record type in the PDB 
 files. This record format was introduced by David Bacon's Raster3D 
 program for specifying the colour scheme to be used when rendering 
 the molecule. This extension is not currently supported by the PDB. 
 The COLO record has the same basic record type as the ATOM and 
 HETATM records described above. 

 Colours are assigned to atoms using a matching process. The Mask 
 field is used in the matching process as follows. First RasMol reads 
 in and remembers all the ATOM, HETATM and COLO records in input 
 order. When the user-defined ('User') colour scheme is selected, 
 RasMol goes through each remembered ATOM/HETATM record in turn, and 
 searches for a COLO record that matches in all of columns 7 through 
 30. The first such COLO record to be found determines the colour and 
 radius of the atom. 

 Note that the Red, Green and Blue components are in the same 
 positions as the X, Y, and Z components of an ATOM or HETA record, 
 and the van der Waals radius goes in the place of the Occupancy. The 
 Red, Green and Blue components must all be in the range 0 to 1. 

 In order that one COLO record can provide colour and radius 
 specifications for more than one atom (e.g. based on residue, atom 
 type, or any other criterion for which labels can be given somewhere 
 in columns 7 through 30), a 'don't-care' character, the hash mark 
 "#" (number or sharp sign) is used. This character, when found in a 
 COLO record, matches any character in the corresponding column in a 
 ATOM/HETATM record. All other characters must match identically to 
 count as a match. As an extension to the specification, any atom 
 that fails to match a COLO record is displayed in white. 

3 Multiple_NMR_Models
 RasMol loads all of the NMR models from a PDB file no matter which 
 command is used: 'load pdb <filename>' or 'load nmrpdb <filename>' 

 Once multiple NMR conformations have been loaded they may be 
 manipulated with the atom expression extensions described in 
 'Primitive Expressions'. In particular, the command 'restrict */1' 
 will restrict the display to the first model only. 

3 CIF_and_mmCIF_Format_Files
 CIF is the IUCr standard for presentation of small molecules and 
 mmCIF is intended as the replacement for the fixed-field PDB format 
 for presentation of macromolecular structures. RasMol can accept 
 data sets in either format. 

 There are many useful sites on the World Wide Web where information 
 tools and software related to CIF, mmCIF and the PDB can be found. 
 The following are good starting points for exploration: 

 The International Union of Crystallography (IUCr) provides access to 
 software, dictionaries, policy statements and documentation relating 
 to CIF and mmCIF at: IUCr, Chester, England 
 (www.iucr.org/iucr-top/cif/) with many mirror sites. 

 The Nucleic Acid Database Project provides access to its entries, 
 software and documentation, with an mmCIF page giving access to the 
 dictionary and mmCIF software tools at Rutgers University, New 
 Jersey, USA (http://ndbserver.rutgers.edu/NDB/mmcif) with many 
 mirror sites. 

 This version of RasMol restricts CIF or mmCIF tag values to 
 essentially the same conventions as are used for the fixed-field PDB 
 format. Thus chain identifiers and alternate conformation 
 identifiers are limited to a single character, atom names are 
 limited to 4 characters, etc. RasMol interprets the following CIF 
 and mmCIF tags: A search is made through multiple data blocks for 
 the desired tags, so a single dataset may be composed from multiple 
 data blocks, but multiple data sets may not be stacked in the same 
 file. 

2 Machine-Specific Support


 In the following sections, support for 'Monochrome X-Windows', 
 'Tcl/Tk IPC', 'UNIX sockets based IPC', 'Compiling RasWin with 
 Borland and MetroWerks' are described. 

3 Monochrome_X-Windows_Support
 RasMol supports the many monochrome UNIX workstations typically 
 found in academia, such as low-end SUN workstations and NCD 
 X-terminals. The X11 version of RasMol (when compiled in 8 bit mode) 
 now detects black and white X-Windows displays and enables dithering 
 automatically. The use of run-time error diffusion dithering means 
 that all display modes of RasMol are available when in monochrome 
 mode. For best results, users should experiment with the set ambient 
 command to ensure the maximum contrast in resulting images. 

3 Tcl/Tk_IPC_support
 Version 4 of Tk graphics library changed the protocol used to 
 communicate between Tk applications. RasMol version 2.6 was modified 
 such that it could communicate with both this new protocol and the 
 previous version 3 protocol supported by RasMol v2.5. Although 
 Tcl/Tk 3.x applications may only communicate with other 3.x 
 applications and Tcl/Tk 4.x applications with other 4.x 
 applications, these changes allow RasMol to communicate between 
 processes with both protocols (potentially concurrently). 

3 UNIX_sockets_based_IPC
 The UNIX implementation of RasMol supports BSD-style socket 
 communication. An identical socket mechanism is also being developed 
 for VMS, Apple Macintosh and Microsoft Windows systems. This should 
 allow RasMol to interactively display results of a computation on a 
 remote host. The current protocol acts as a TCP/IP server on port 
 21069 that executes command lines until either the command 'exit' or 
 the command 'quit' is typed. The command exit from the RasMol 
 server, the command 'quit' both disconnects the current session and 
 terminates RasMol. This functionality may be tested using the UNIX 
 command 'telnet <hostname> 21069'. 

3 Compiling_RasWin_with_Borland_and_MetroWerks
 A number of changes were made to the source code in the transition 
 from version 2.5 to 2.6 to allow the Microsoft Windows version of 
 RasMol to compile using the Borland C/C++ compiler. These fixes 
 include name changes for the standard library and special code to 
 avoid a bug in _fmemset. Additional changes were made in the 
 transition from 2.6 to 2.7 to allow compilation with the MetroWerks 
 compilers. 

2 Bibliography


3 Molecular_Graphics
 [1] Nelson Max, "Computer Representation of Molecular Surfaces", 
 IEEE Computer Graphics and Applications, pp.21-29, August 1983. 

 [2] Arthur M. Lesk, "Protein Architecture: A Practical Approach", 
 IRL Press Publishers, 1991. 

3 Molecular_Graphics_Programs
 [3] Per J. Kraulis, "MOLSCRIPT: A Program to Produce both Detailed 
 and Schematic Plots of Protein Structures", Journal of Applied 
 Crystallography, Vol.24, pp.946-950, 1991. 

 [4] David Bacon and Wayne F. Anderson, "A Fast Algorithm for 
 Rendering Space-Filling Molecule Pictures", Journal of Molecular 
 Graphics, Vol.6, No.4, pp.219-220, December 1988. 

 [5] David C. Richardson and Jane S. Richardson, "The Kinemage: A 
 tool for Scientific Communication", Protein Science, Vol.1, 
 No.1,pp.3-9, January 1992. 

 [6] Mike Carson, "RIBBONS 2.0", Journal of Applied Crystallography, 
 Vol.24, pp.958-961, 1991. 

 [7] Conrad C. Huang, Eric F. Pettersen, Teri E. Klein, Thomas E. 
 Ferrin and Robert Langridge, "Conic: A Fast Renderer for 
 Space-Filling Molecules with Shadows", Journal of Molecular 
 Graphics, Vol.9, No.4, pp.230-236, December 1991. 

3 Molecular_Biology_Algorithms
 [8] Wolfgang Kabsch and Christian Sander, "Dictionary of Protein 
 Secondary Structure: Pattern Recognition of Hydrogen-Bonded and 
 Geometrical Features", Biopolymers, Vol.22, pp.2577-2637, 1983. 

 [9] Michael L. Connolly, "Solvent-Accessible Surfaces of Proteins 
 and Nucleic Acids", Science, Vol.221, No.4612, pp.709-713, August 
 1983. 

 [10] Khaled Belhadj-Mostefa, Ron Poet and E. James Milner-White, 
 "Displaying Inter-Main Chain Hydrogen Bond Patterns in Proteins", 
 Journal of Molecular Graphics, Vol.9, No.3, pp.194-197, September 
 1991. 

 [11] Mike Carson, "Ribbon Models of Macromolecules", Journal of 
 Molecular Graphics, Vol.5, No.2, pp.103-106, June 1987. 

 [12] Mike Carson and Charles E. Bugg, "Algorithm for Ribbon Models 
 of Proteins", Journal of Molecular Graphics, Vol.4, No.2, 
 pp.121-122, June 1986. 

 [13] H. Iijima, J. B. Dunbar Jr. and G. Marshall, "Calibration of 
 Effective van der Waals Atomic Contact Radii for Proteins and 
 Peptides", Proteins: Structure, Functions and Genetics, Vol.2, 
 pp.330-339,1987. 

3 Graphics_Algorithms
 [14] J. Foley, A. van Dam, S. Feiner and J. Hughes, "Computer 
 Graphics: Principles and Practice", 2nd Edition, Addison Wesley 
 Publishers, 1990. 

 [15] J. Cleary and G. Wyvill, "Analysis of an Algorithm for Fast Ray 
 Tracing using Uniform Space Subdivision", The Visual Computer, 
 Vol.4, pp.65-83, 1988. 

 [16] Thomas Porter,"Spherical Shading", Computer Graphics Vol.12, 
 ACM SIGGRAPH, pp.282-285, 1978. 

 [17] Jean-Michel Cense, "Exact Visibility Calculation for 
 Space-Filling Molecular Models", Journal of Molecular Graphics, 
 Vol.9, No.3, pp.191-193, September 1991. 

 [18] Chris Schafmeister, "Fast Algorithm for Generating CPK Images 
 on Graphics Workstations", Journal of Molecular Graphics, Vol.8, 
 No.4, pp.201-206, December 1990. 

 [19] Bruce A. Johnson, "MSURF: A Rapid and General Program for the 
 Representation of Molecular Surfaces", Journal of Molecular 
 Graphics, Vol.5, No.3, pp.167-169, September 1987. 

3 File_Formats
 [20] Frances C. Bernstein et al., "The Protein Data Bank: A 
 Computer-Based Archival File for Macromolecular Structures", Journal 
 of Molecular Biology, Vol.112, pp.535-542, 1977. 

 [21] Arthur Dalby, James G. Nourse, W. Douglas Hounshell, Ann K. I. 
 Gushurst, David L. Grier, Burton A. Leland and John Laufer, 
 "Description of Several Chemical File Formats Used by Computer 
 Programs Developed at Molecular Design Limited", Journal of Chemical 
 Information and Computer Sciences, Vol.32, No.3, pp.244-255, 1992. 

 [22] Adobe Systems Inc., "PostScript Language Reference Manual", 
 Addison-Wesley Publishers, Reading, Mass., 1985. 

 [23] Philip E. Bourne et al., "The Macromolecular Crystallographic 
 Information File (mmCIF)", Meth. Enzymol. (1997) 277, 571-590. 

 [24] Sydney R. Hall, "The STAR File: a New Format for Electronic 
 Data Transfer and Archiving", Journal of Chemical Information and 
 Computer Sciences, Vol. 31, 326-333, 1991.