Graduate Study in - Chemistry - Johns Hopkins University

Joel R. Tolman
Biophysical Chemistry
jtolman@jhu.edu
Ph.D., Yale University
Human Frontier
Postdoctoral Fellow,
University of Toronto
Postdoctoral, École
Polytechnique Fédérale de
Lausanne
Within the past two decades, Nuclear Magnetic Resonance spectroscopy
(NMR) has become a powerful technique for the study of
macromolecular structure and dynamics in the solution state. Research
in my lab will be concerned with both the development and application
of novel NMR techniques for studying the complex interactions that
underlie biological function. Of particular interest are studies of molecular dynamics,
the nature of intermolecular recognition and the quaternary organization of multidomain
protein systems.
The full repertoire of multidimensional NMR methodology will be employed
to study these problems, including spin relaxation, scalar coupling, NOE, and
hydrogen exchange experiments. However, the primary approach will be centered
around recently developed techniques for the measurement of Residual Dipolar
Couplings (RDCs) in macromolecules. These RDCs, which are normally averaged to
zero in solution, are made observable by introducing a very weak degree of alignment
of the biomolecule relative to the magnetic field. This alignment is typically achieved
by dissolving the protein or nucleic acid along with a suitable co-solute, such as
bacteriophage particles. The resulting RDCs are relatively easily measured and
represent an abundant source of highly precise information on the relative
orientations of different internuclear ‘bonds’ within the molecule. Intriguingly, RDCs
also exhibit sensitivity to molecular motions on the nsec-sec timescales, during which
many functionally important motions occur. These motional timescales have
traditionally been very difficult to access experimentally, and thus a major objective
will be to develop RDC-based techniques to enable the study of these motions.
One of the applications of these techniques will be to investigate the
quaternary organization of tetrameric ubiquitin. Tetramers of the protein ubiquitin
can assume a multi-faceted role in cellular signal-transduction mechanisms, which
depends on how they are linked together. A major goal will be to gain insights into
the nature of this important and versatile signal through studies of its solution state
conformations. In addition, efforts are ongoing to develop methodology for the
simultaneous determination of both the 3-dimensional structure and a detailed
description of the dynamics of a protein. A closely related objective is to develop the
capability of using NMR to rapidly determine the backbone fold of a protein to
moderate resolution, which would represent an important contribution to current
structural genomics initiatives.
Selected publications include:
Tolman, J.R., “Dipolar Couplings as a Probe of Molecular Dynamics and Structure in Solution,”
Curr. Opin. Struct. Biol. 2001, 11, 532-539.
Al-Hashimi, H.M.; Tolman, J.R.; Majumdar, A.; Gorin, A.; and Patel, D.J., “Determining
Stoichiometry in Homomultimeric Nucleic Acid Complexes Using Magnetic Field Induced Residual
Dipolar Couplings,” J. Am. Chem. Soc. 2001, 123, 5806-5807.
Tolman, J.R.; Al-Hashimi, H.M.; Kay, L.E.; and Prestegard, J.H., “Structural and Dynamic Analysis
of Residual Dipolar Coupling Data for Proteins,” J. Am. Chem. Soc. 2001, 123, 1416-1424.
Tolman, J.R.; Flanagan, J.M.; Kennedy, M.A.; and Prestegard, J.H., “NMR Evidence for Slow
Collective Motions in Cyanometmyoglobin,” Nature Struct. Biol. 1997, 4, 292-297.
20 Graduate Study in Chemistry at The Johns Hopkins University