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:
- 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. Recently the NIH issued an RFA to support the purchase of 900 MHz spectrometers and we plan to submit applications to this program in fall of 2001.
- 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 advances in the theory, practice and implementation of quantum information processing. Over the past year this has included the first exploration of decoherence control via noiseless subsystem encoding, and the first NMR demonstrations of entanglement transfers and quantum erasers.
- 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 tests and we anticipate delivery in a few weeks. A unique feature of the magnet is a ±500 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
Quantum Information Processing
Professor Cory and his students continue to explore NMR approaches to quantum information processing (QIP) through a set of collaborations with Dr. Timothy Havel (NED), Professor Seth Lloyd (Mechanical Engineering), Professor Eddie Farhi (Physics), Dr. Raymond Laflamme (LANL), Dr. Emanuel Knill (LANL), Dr. Jeff Yepez (AFRL). Our liquid state NMR implementation of quantum information processing is now being implemented at the 10 qubit level; a complexity far beyond other approaches to quantum information processing.
We have started to construct a new scheme for extending the success of NMR approaches to QIP to larger systems via a solid state device capable of coherently controlling 10-30 qubits. This is essential for exploring quantum error correction. We have also obtained funding to explore lattice gas computations on classically distributed quantum computers.
NMR of heterogeneous semi-solids
In collaboration with Dr. Samuel Singer, and Dr. Pabitra Sen of Schlumberger-Doll Research Laboratory we have continued to explore the structure and fluid dynamics of complex media. This has led to a new prognosticator of tumor grade for soft tissue sarcomas, and a new measure of local organization for heterogeneous samples. For the first time, the effects of motion can be cleanly separated from the overall spin dynamics which provides a simple and direct means of characterizing micron scale structures.
NMR imaging of neuron structure and function
In collaborations with Dr. Alan Jasanoff (a Whitehead Fellow at MIT), the neuron structure and response of blow flies is being explored at high resolution via NMR microscopy. The use of blow flies provides a stable and well characterized test bed, while simultaneously permitting near cellular resolution in the NMR. The goal of the program is to observe neuron activity in living/functioning tissue with the markers being directly traceable to neuron biochemistry.
Professor Robert G. Griffin
High Frequency Electron Paramagnetic Resonance (EPR)
About a two years 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. We are in the process of 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, we are 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 are in progress.
Structural Studies of Alzheimer's Disease Amyloid
Amyloidoses are a group of disorders due to peptide or protein misfolding and characterized by the accumulation of insoluble fibrillar protein material in extracellular spaces. Sixteen different peptides are known to form amyloid-like aggregates, and are involved in several diseases. ß-amyloid (Aβ) in Alzheimer's disease, the prion protein PrPc converts to PrPsc leading to the transmissible spongiform encephalopathie, and the synuclein protein is responsible for Parkinson's disease.
During the last two years, we developed methods to obtain large amounts of fibrillar peptide material. And to maintain this material in a state suitable for MAS NMR experiments. We have used these techniques in a collaborative study of the structure of 11-mer fibrillar peptides in collaboration with Professor Chris Dobson of Cambridge University. The peptides are derived from transthyretin and to date have yielded excellent spectra. We are presently in the process of assigning these spectra and plan by next year to have a structure of a fibrillar system.
Dynamic Nuclear Polarization
During the past year we have improved the operation of the 140 GHz system and have obtained the initial MAS spectra exhibiting an enhancement of ~15 at ~90K. We have continued to operate the 250 GHz gyrotron on a routine basis and are near to initiating MAS DNP experiments with the device. At present these represent the highest frequency DNP experiments ever performed, and more importantly suggest that even higher frequency operation will be successful. In collaboration with the PSFC we have designed and are constructing a 460 GHz gyrotron that will be used in conjunction with the 700/89 widebore magnet which is installed and operating.
Dipolar Recoupling
Over the last decade we have been heavily involved in the development of techniques to measure distances and torsion angles in solids. The goal is to be able to determine the structure of membrane proteins, amyloid fibrils, etc with solid state NMR. This past year we completed the initial structure of a small peptide. We anticipate that with increased signal to noise available from 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 25th year of operation as a facility open to scientists needing access to high field NMR equipment. During this year, 53 projects were worked on by 90 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 and Women's Hospital. Work resulted in 48 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.
Recently the NIH issued an RFA to support the purchase of 900 MHz spectrometers and we plan to submit applications to this program in fall of 2001. The 900's will be operated as part of the CMR. In addition we anticipate applying for additional widebore 800 class systems in the next year or two.
More information about the Griffin Group's research can be found at http://web.mit.edu/fbml/cmr/griffin-group/.
Dr. Yukikazu Iwasa
We are involved in Research and Development of superconducting magnet technology, particularly of high-temperature superconductor (HTS). Specific HTS-related projects that the Magnet Technology Division (MTD) is currently involved include: development of a flux pump for NMR superconducting magnets that incorporates HTS inserts; phase 1 project of a 3-phase, 6 year program to complete a 1-GHz NMR magnet that includes an HTS insert; development of vapor-cooled current leads that combine HTS and copper sections; study of stability/protection of HTS magnets used in electric power devices; and development of a "noise-free" NMR magnet system. Topics 4 and 5 apply solid nitrogen technology recently developed by the MTD. These projects are briefly summarized below.
Flux Pump for NMR Superconducting Magnets
Flux pump is considered a viable technology for achieving the 1-GHz milestone. By allowing precisely metered quantities of magnetic energy to be injected into a slightly dissipative superconducting coil, e.g., an HTS insert coil in a 1-GHz magnet system, a flux pump can make the dissipative coil operate in an effectively persistent mode.
Started on June 1, 2000, we have since designed, built, and successfully operated a model flux pump to confirm its experimental results with analysis. Presently, we are designing a prototype flux pump that will be coupled to a Phase 1 LTS/HTS NMR magnet presently under construction in the MTD, described below.
HTS Insert Coil for 1-GHz NMR Magnet
The MTD is presently undertaking Phase 1 of a 6 year 3-Phase project to complete a high-resolution 1-GHz NMR magnet. In each phase, an HTS insert coil will be designed, built, and operated in a background LTS magnet. Started on October 1, 2000, we have since designed the HTS insert and presently are in the process of winding it. We expect to perform critical current measurements of the insert in a high background field at the National High Magnetic Field Laboratory, Tallahassee, FL in September 2001, and afterward proceed to assemble the insert into a background NMR magnet already available in the MTD.
Vapor-Cooled HTS/Copper Current Leads
As a DOE-sponsored STTR project, we collaborated with American Magnetics, Inc., Oak Ridge, TN, to successfully complete Phase I program to develop a new type of commercially viable vapor-cooled HTS/Copper current leads. This new type of current leads is based on a concept recently developed in the MTD and patented by MIT.
A large heat capacity of solid nitrogen in the temperature range 10-60K is considered beneficial for operation of HTS magnets in some applications.
Stability/Protection of HTS Magnets
The large heat capacity of solid nitrogen impregnating the winding of an HTS magnet in an electric power device limits the temperature rise in the HTS winding subjected to fault-mode overcurrent pulses. We are investigating quench/recovery processes of YBCO-coated tape subject to transient heating in the presence and absence of a minute amount of solid nitrogen in the HTS winding.
"Noise-Free" NMR Magnet
A "noise-free" magnet/cryo-cooler NMR system incorporates solid nitrogen in the system. The large heat capacity of the solid nitrogen permits "noise-free" operation of an NMR system with its cryocooler idled over a period long enough for measurement. (Microphonics from the running cryocooler precludes microscopic scattering measurements.) Starting June 1, 2001, we began development of a commercially viable compact NMR magnet system based on this concept as an NIH STTR Phase I project in collaboration with American Magnetics, Inc., Oak Ridge, TN.
Dr. Jagadeesh S. Moodera
In condensed matter physics, in particular magnetism, our research continues to make significant contributions to both fundamental science and industrial application. Our basic investigation emphasizes interfacial exchange interaction and spin transport in thin film structures. Using our molecular beam epitaxy (MBE) system, our 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. Our 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, we are continuing national and international collaborative research efforts with scientists and faculty from national laboratories, U.S. 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.
Recently we have begun a program on the thin film studies of a recently discovered novel superconductor which has a high potential for application in Josephson junction based computers, logic elements, mixers switches and sensors. The results have been quite promising. 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). We 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.
Five postdoctoral scholars, four undergraduates and six high school students have taken part in Dr. Moodera's research. One of the undergraduates did her B.S. thesis and another one is carrying out her thesis under the PI's supervision. The high school students won several science competitions, including a semifinalist in Intel-Westinghouse Science Competition, as well as other regional and state level awards. Research resulted in four publications including a feature article for Physics Today and over eight invited talks at various national and international conferences, universities and laboratories. Dr. Moodera has been invited to spend some time at Eindhoven Technical University as a visiting professor. He has taken part at the national level magnetism committee policies and meeting initiatives, as well as serving in the scientific board of international meetings. There are nine research grants under Dr. Moodera's supervision, including four NSF, two ONR, one NASA and from two other companies. Dr. Moodera was elected as Fellow of American Physical Society in the fall of 2000.
Dr. Harald Schwalbe
Our research is focussed on the studies of structural and kinetic aspects of protein folding using high resolution NMR spectroscopy. It is now known that the process of protein folding and unfolding is coupled to a wide range of biological phenomena from the regulation of cellular activity to neurodegenerative diseases. The nature of the conformations sampled in non-native proteins is crucial for the understanding of all these phenomena. In the last year, we have used a combination of nuclear magnetic resonance spectroscopy and site-directed mutagenesis to study unfolded states of the protein lysozyme. Extensive clusters of hydrophobic structure exist in the wild-type protein even under strongly denaturing conditions. These clusters are, however, dramatically destabilized by a single point mutation, W62G, located in the interface of the main structural domains in the native state. The results provide remarkable evidence for the presence and exact location of long-range cooperative interactions within the ensemble of non-native conformations both in the presence and absence of native disulfide bonds. In a second research project, we try to understand the importance of these non-native conformations for the kinetics of protein refolding. Using time-resolved Photo-CIDNP NMR methods, we were able to characterize the Ca2+ induced refolding of a-lactalbumin with unprecedented temporal and site resolution. Refolding at constant denaturant concentration was initiated by laser induced ion release from photolabile chelators. The NMR data allows derivation of aspects of the structure of the intermediate populated after 200ms. Part of the polypeptide chain in the b-domain of a-lactalbumin samples non-native conformations while a hydrophobic core of the a-domain is formed.
Facilities
During the past year, we have started the renovation process for the magnet cell to accommodate the 700/89 system. We are also beginning to discuss the renovations for the 900 MHz instruments.
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 20 postdoctoral fellows performing research.
Future Plans
Discussion of for space for the 900 MHz magnets is under discussion and proposals are being prepared for acquisition of this system.
We are discussing plans to place a 3 Tesla imaging system on the first floor of Building NW14. The system will be used by investigators from the Deptartment of Brain and Cognitive Science and others interested in functional magnetic resonance imaging.
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.