FRANCIS BITTER MAGNET LABORATORY

The Francis Bitter Magnet Laboratory (FBML) has continued to make notable advances in several areas of science and engineering involving high magnetic fields. The research program in Magnetic Resonance (nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR)) has continued to grow and remains the largest effort at the FBML. The program is funded primarily by the NIH and DOE, and involves ~20 NMR and EPR magnets and spectrometers.

A few of this year’s highlights include the following.

Professor Robert G. Griffin, together with Professor Gerhard Wagner of Harvard University, continue to operate The MIT/Harvard Center for Magnetic Resonance, a collaborative research effort between MIT and Harvard Medical School. The Center is supported by a NIH Research Resource grant that was renewed for five years.

Professor Harald Schwalbe joined the Department of Chemistry in October, 1999. His offices and laboratory space are presently located at the FBML. Professor Schwalbe’s area of research is focussed on solution NMR studies of protein folding and structures of ribonucleic acids.

Professor Cory and his colleagues continue to make rapid advances in the theory, practice and implementation of quantum information processing. In collaboration with Bruker Instruments, Inc., they have helped to develop and taken delivery of the first special-purpose commercial NMR designed for quantum information processing. They are now constructing a second-generation quantum processor that is designed to reach more than 10 qubits.

Dr. Yukikazu Iwasa received funding from NIH to construct a very high field, wide bore 700 MHz NMR system. The system is essentially complete and has successfully passed most test and we anticipate delivery in a few weeks. A unique feature of the magnet is a ą500 Gauss sweep coil essential for dynamic nuclear polarization experiments.

Dr. Jagadeesh Moodera has continued to strengthen his research efforts in condensed matter physics through collaboration with various universities and industries, as well as the ONR and NSF. In addition, he has continued his mentoring of graduate students, undergraduate and high school students by providing research opportunities within his lab. Dr. Moodera received the 2000 TDK Research Award for his pioneering studies in spin tunneling.

RESEARCH ACTIVITIES

Professor David G. Cory’s research activities include the following:

Quantum Information Processing (QIP). Professor Cory continues to explore NMR approaches to quantum information processing through a set of collaborations with Dr. T. Havel (HMS), Professor Seth Lloyd (Mechanical Engineering), Dr. Raymond Laflamme (LANL), Dr. E. Knill (LANL) and Dr. J. Yepez (AFRL). Much of our recent efforts have been directed to making liquid-state NMR implementations of quantum information processing robust at the level of 5 to 7 qubits. They have also articulated two new schemes for extending the success of NMR approaches to QIP to larger systems and have started to build a solid-state device capable of coherently controlling 10 ñ 30 qubits, which will have the unique feature of a resettable qubit. This is essential for exploring quantum error correction.
NMR of heterogeneous semi-solids. In collaboration with Dr. S. Singer, and Dr. Pabitra Sen of Schlumberger Doll Research Laboratory, Professor Cory has continued to explore the structure and fluid dynamics of complex media. This is facilitated by a series of recently developed methods that permit the separation of the pore structure factor from the incoherent fluid motion. They have shown that the NMR signal (after suitable averaging and manipulation) provides a fingerprint of the sample geometry and that much of the inverse problem can be solved. Applications are expected in both biology and in granular or porous media.
NMR imaging of fluid transport through granular media. In collaborations with Professor Culligan (Civil and Environmental Engineering) and Professor Czerwinski (Nuclear Engineering), the transport of lanthanides and the displacement of contaminants in model sands, soils and resins are being studied by NMR. For resorcinol resins (used to trap metals) the NMR results provide a clean and unambiguous measure of bound, plasticizer and free water ñ including their exchange properties.

Professor Robert G. Griffin’s research acitivities included the following:

High Frequency Electron Paramagnetic Resonance (EPR). About a year ago the capabilities of the 140 GHz EPR spectrometer were dramatically extended by the incorporation of a four-phase microwave pulse-forming network and amplifier with 30 mW of output power. Professor Griffin has just received funding for a further upgrade to ~110 mW. The greater microwave power and phase switching capability allows us to develop and perform sophisticated pulsed EPR techniques. In particular, his group is working on developing new pulsed methods for spectral filtering, electron/nuclear cross polarization and multiquantum EPR experiments for measuring long-range distances (10-30 Å) in spin labeled proteins and peptides. In addition, the 140 GHz pulsed Electron-Nuclear Double Resonance (ENDOR) capability has already been used to examine a number of systems. For example, the increased sensitivity, resolution, and orientation selection available in the ENDOR experiment at this high frequency/field has enabled us to determine in detail the electronic structure of the tyrosyl radical of ribonucleotide reductase. (RNR) ENDOR studies of the RNR inhibitor complexes.
Structural Studies of Alzheimer’s Disease Amyloid. Amyloidoses are a group of peptide or protein misfolding disorders characterized by the accumulation of insoluble fibrillar protein material in extracellular spaces. Sixteen different peptides are known to form amyloid-like aggregates. The aggregation of these peptides is involved in several diseases. ß-amyloid (Aß) is involved in Alzheimer's disease, the conversion of the prion protein PrPc to PrPsc leads to the transmissible spongiform encephalopathie, and the synuclein protein is responsible for Parkinson's disease.
During the last two years, Professor Griffin’s lab has worked on methods to obtain large amounts of fibrillar peptide material. Fibril preparation is crucial for obtaining narrow lines, maximizing spectral resolution, and optimizing signal intensities. Fibril formation is also important for the biological relevance of the structural model. Furthermore, we have obtained ¹³C/¹⁵N labeled Ab 1-40 and prepared fibrils of this material. High-resolution AFM (Atome Force Microscopy) images indicate that this fragment forms regular fibrils as well and our first ¹³C /¹⁵N MAS spectra reveal resolved a few resonances. During the coming year, we are planing serious structural studies of the Ab peptide.

A web site describing some of Professor Griffin’s research can be found at http://web.mit.edu/fbml/cmr/griffin-group/.

In addition, Professor Griffin’s group has underway studies of smaller fibrillar peptides in collaboration with Professor Chris Dobson of Cambridge University.

Dynamic Nuclear Polarization. During the past year they have operated the 250 GHz gyrotron on a routine basis and have initiated high frequency DNP experiments with the device. The DNP/NMR spectrometer consist of 125 mm bore 375 MHz NMR magnet and a new spectrometer console is being assembled for these experiments. The initial results indicate that we will achieve substantial signal enhancements at this frequency. At present these represent the highest frequency DNP experiments ever performed, and more importantly suggest that even higher frequency operation will be successful. Thus, in collaboration with the PSFC they are now in the process of designing and constructing a 460 GHz gyrotron that will be used in conjunction with the 700/89 widebore magnet mentioned above.
Dipolar Recoupling. Over the last decade they have been heavily involved in the development of techniques to measure distances and torsion angles in solids. The ultimate goal is to be able to determine the structure of membrane proteins, amyloid fibrils, etc with solid state NMR. This past year we have succeeded in developing methods for performing these experiments in uniformly ¹³C /¹⁵N labeled molecules and we have utilized them to determine the structure of a small peptide. They anticipate that with increased signal to noise available form DNP experiments that these methods will be applicable to a large number of systems not accessible to solution NMR and X-ray crystallographic investigations.
Center for Magnetic Resonance. The Center for Magnetic Resonance has completed its 24^th year of operation as a facility open to scientists needing access to high field NMR equipment. During this year, 69 projects were worked on by 126 investigators, from departments within MIT including Chemistry, Physics and Nuclear Engineering, as well as users and collaborators from institutions outside of MIT such as Harvard University, Brandeis University and Brigham & Women’s Hospital. Work resulted in 52 publications in print or in press. Highlights of work conducted at the center include advances in high frequency dynamic nuclear polarization of proteins (DNP), time resolved studies of protein folding, structures of large proteins, and high frequency EPR and ENDOR. A competing proposal was submitted to NIH for review during the summer of 1998 and is now funded for an additional five-year period.

Dr. Yukikazu Iwasa’s research activities include the following:

Dr. Iwasa’s group has continued research on the key operational issue of protection for high temperature superconducting (HTS) magnets operating in the temperature range 10-60 K. In addition to this basic protection study, they have investigated practical aspects of cryocooler-cooled operation. They have studied small coils wound from silver-sheathed BSCCO-2223 tapes in the temperature range 20--60 K. they have developed a numerical NZP model for a three-dimensional, dry-wound, BSSCO-2223 superconducting magnet. The test magnet operates under quasi-adiabatic conditions at 20~K and above, in zero background field. The NZP model is based on the two-dimensional transient heat diffusion equation. Agreement between voltage traces obtained in the test magnet during heater-induced quenching events and those computed by the numerical NZP model is reasonable. The model is also used to simulate quenching in magnets similar to the test magnet.
A new 2-year DOE-funded joint FBML-FSU/NHMFL project has started on 06/01/2000 to study stability and quench protection of YBCO wires and coils. Of particular interest to the project is the study of beneficial effects of solid nitrogen impregnated in the winding of a high-temperature superconducting coil. Solid nitrogen in the temperature range below ~60K has a heat capacity much greater than that of silver. Thus, even a small amount of solid nitrogen present within the coil winding is expected to enhance the overall heat capacity of the winding, making the coil more stable against transient heating such as that can be caused by overcurrent pulses in electric power devices.
Also started on 06/01/2000 is a new 2-year NIH-funded project on development of a flux pump for use in a high-field superconducting NMR magnet containing a high-temperature superconducting insert coil. Because of low indices, HTS insert coils, even with superconducting splices, cannot be operated perfectly in persistent mode; their currents will decay slowly albeit at a very small rate. An HTS insert coil coupled to a flux pump can receive precisely metered quantities of energy and operate effectively in persistent mode.
His work on developing a "permanent" HTS magnet system is nearly complete. The system combines the simplicity and ease of operation of a ferromagnetic permanent magnet with the strength, capability and versatility in field generation of an electromagnet. Once energized and producing a desired field, the system, without being coupled to a cooling source, can maintain that field for a long period. This HTS magnet is particularly suitable for an on-board or portable unit requiring a constant field and where "permanence" means a duration of hours, days, weeks, months, or even years. The system’s other features are "recooling" and "recharging" capabilities designed to have the system re-cooled while maintaining its constant field to make the field literally permanent, and recharged if its upper operating temperature is exceeded and the field decays.
An application has been filed to the U.S. Patent and Trademark Office for invention of a new high-temperature superconducting (HTS) current lead. The new HTS lead requires HTS materials that are substantially less than those required by the conventional HTS current leads available on the market. The core of the invention is that, in the new HTS current lead, a warm part of the HTS lead is operated in the so-called "current-sharing" (partially resistive) mode rather than completely in the superconducting state as in the conventional HTS current lead.

Dr. Jagadeesh S. Moodera’s research activities include the following:

In condensed matter physics, in particular magnetism, his research continues to make significant contributions to both fundamental science and industrial application. His basic investigation emphasizes interfacial exchange interaction and spin transport in thin film structures. Using his molecular beam epitaxy (MBE) system, his research seeks to contribute to the understanding of the spin properties of conventional materials and to unraveling the spin properties of certain novel magnetic compounds that have a high potential for technological application. His research in these materials has already shown the possibility of a four-level memory/logic element. Several companies, including IBM, HP, Motorola, TDK and Fujitsu, are developing this structure for application in digital storage. In this context, his group is continuing national and international collaborative research efforts with scientists and faculty from national laboratories, US universities, the University of Paris at Orsay, the University of Eindhoven, Tohoku University, the Tata Institute of Fundamental Research and the Ukrainian Academy of Sciences. Exchange of scientists and graduate students is a part of this program.
In the area of semiconductors, our continued collaboration with Hewlett-Packard Company has been valuable in searching for far future material for atomically resolved storage ( > Terabytes/in² ). He are exploring the materials with the appropriate properties and giving HP the fundamental information necessary for their program. In this direction we have been successful in identifying a possible candidate material from among thousands of compounds. There is ongoing collaboration with other companies such as NVE Inc., TDK (Japan) in the field of magnetism.
Three postdoctoral scholars, one graduate, four undergraduate and four high school students have taken part in Dr. Moodera’s research. One graduate student (from DMSE) obtained his doctoral degree. The high school students won several science competitions, including a semifinalist in Intel-Westinghouse Science Competition, as well as other regional top awards. Notably, one high school student who participated in the RSI program at MIT under Dr. Moodera’s supervision won the top award in Singapore National Science competition. Research resulted in nine publications and over ten invited talks at various national and international conferences, universities and laboratories. Dr. Moodera spent some time at Eindhoven Technical University as a visiting professor and was one of five US researchers invited to give a presentation and participate in a NSF panel discussion regarding the next ten years of research initiative. In addition, he was invited to write a feature article for Physics Today and received TDK Research Award once again in 2000 for his research in spin tunneling.

Dr. Harald Schwalbe’s research includes the following:

His research is focussed on the studies of structural and kinetic aspects of protein folding. He uses high resolution NMR spectroscopy as our primary tool. The random coil state of a protein consists of an ensemble of conformers. We have developed a model to predict the conformational averaging around the angles f, y, and c1 in the random coil state and could test this model from NMR measurements of chemical shifts, coupling constants and cross-correlated relaxation rates. In order to link the conformational analysis with the kinetics of folding, we are carrying out time-resolved NMR studies to gain insight into the structures of folding intermediates. This has been achieved by coupling the folding of proteins to the rapid release of ions from photo labile precursor molecules. The folding kinetics of single atoms could be determined. The accessibility of aromatic residues was further tested using Photo-CIDNP experiments. Single scan experiments could be performed that show the reorientation of the hydrophobic core of the protein during folding.
A second focus is the characterization of structure and dynamics of RNA. His group was able to develop new NMR methods to determine all free torsion angles in RNA oligonucleotides including the backbone angles a and z which were considered inaccessible in the literature by exploiting cross-correlated relaxation in high resolution NMR. New research is now determining the geometry and energetics of Watson-Crick base pairs in solution. In the light of our new findings, Watson-Crick base pairs have to be described by a three state model, in which an intermediate is populated for 1%. In this intermediate, the nucleobases remain stacked but the hydrogen bonding interactions are weakened. Our new data allows the dissection of the energy contribution of hydrogen bonds and stacking to base pair stability.

FACILITIES

During the past year, FBML resources were consolidated into one building. We now boast an upgraded space for 2 750 MHz NMR magnets, as well as space for the wide bore 750 MHz magnet to be built under Dr. Yukikazu Iwasa.

Newly renovated facilities have recently been provided for Professor Cory’s research group, including a wet lab and a computer lab.

Professors Keith Nelson and Andrei Tokmakoff of the Department of Chemistry have left the temporary lab space on the first floor used during completion of their permanent laser lab facility in the Chemistry Department.

Extensive renovation has been complete on the second floor to provide office space for Professor Jacquelyn Yanch, Professor David Cory and their students.

EDUCATION AND PERSONNEL

The Laboratory contributes to undergraduate education by participation in the Undergraduate Research Opportunities Program (UROP) a program that encourages and supports research-based intellectual collaborations of MIT undergraduates with Institute faculty and research staff. In addition, the laboratory has 20 full-time graduate and 8 postdoctoral students performing research.

FUTURE PLANS

Third magnet cell for a wide bore 700 MHz magnet is under renovation and requires completion.

During the past year 900 MHz instruments have been completed, and we have been told that NIH will issue a call for proposals to purchase these instruments early in 2001. We plan to submit such a proposal for a complete system which will be part of the MIT-Harvard CMR. In connection with this proposal will be requesting that NW15 be renovated to accommodate two 900/1000 MHz NMR magnets.

In the longer term we also plan to complete construction of the second floor magnet hall, and instruments currently housed on the fourth and fifth floors will be relocated in order to create a comprehensive "Center for Magnetic Resonance." An alternative plan would be as Professor Schwalbe’s research group grows, the space could house his instrumentation.

Robert G. Griffin

MIT Reports to the President 1999–2000