A large fraction of our research effort is devoted to the development of new magnetic resonance techniques to study molecular structure and dynamics. Typical of the problems that we address is the design of experiments to measure 13C-13C and 13C-15N dipolar couplings, and therefore to perform spectral assignments and to measure internuclear distances and torsion angles, in solids from magic angle spinning (MAS) NMR spectra. This information leads directly to molecular structures of amyloid and membrane peptides and proteins (vide infra). In addition, we are developing high field dynamic nuclear polarization (DNP)/NMR experiments. The motivation behind this research is the possibility to obtain large nuclear spin polarizations, and therefore increased NMR signal intensities. The top figure at the left illustrates signal enhancements recorded from a sample of U(13C,15N) proline where we have observed a factor of ~20 larger signal strengths when the sample is doped with paramagnetic centers and irradiated with 250 GHz microwaves. The experiments have developed to the point where it is possible to record multiple dimensional spectra as illustrated in the middle panels of the figure. This increased signal intensities should enable many new applications to be addressed. As part of this project, we are also performing CW and pulsed EPR experiments at 140 GHz. For systems not susceptible to g-strain, the higher EPR frequencies offer considerably increased resolution and ease of interpretation of the spectral lineshapes. Finally, we are also involved in the development of approaches for investigating dynamic processes in solids. Generally, these experiments involve analysis of 2H NMR powder patterns, and details concerning the rates and mechanism of the motion are derived from the lineshapes.

The second major part of our research is the application of the magnetic resonance techniques described above to interesting chemical, biophysical, and physical problems. We are currently employing MAS NMR experiments to investigate the structure of large enzyme/inhibitor complexes, membrane proteins and amyloid peptide and proteins. By measuring chemical shifts and dipolar couplings between homonuclear and heteronuclear spin pairs in inhibitors or active sites, we have been able to address structural questions in several cases. For example, we have performed NMR on photochemical intermediates of bacteriorhodopsin trapped at low temperature to study the mechanism of proton pumping and the origin of the opsin shift in the optical spectrum of retinal in this protein. More recently we have completed the initial two structures of peptides with MAS dipole recoupling techniques. One of these, an 11-mer from the protein transthyretin, is illustrated in the bottom part of the figure and is the initial structure of a peptide in an amyloid fibril. Since these molecules do not diffract and are not soluble, their structures can only be determined by high resolution solid state NMR.

2008

M. L. Mak-Jurkauskas, V. S. Bajaj, M. K. Hornstein, M. Belenky, R. G. Griffin, and J. Herzfeld, “Gradual Winding of the Bacteriorhodopsin Chromophore in the First Half of Its Ion-Motive Photocycle: a Dynamic Nuclear Polarization-Enhanced Solid State NMR Study”, Proc. Nat’l. Acad. Sci. 105, 883-888 (2008)

K-N. Hu, C. Song, H-h. Yu, T.M. Swager, and R.G. Griffin, “High-Frequency Dynamic Nuclear Polarization Using Biradicals: A Multifrequency EPR Lineshape Analysis”, J. Chem. Physics 128, 052302 (2008)

M. J. Bayro, R. Ramachandran, M. A. Caporini, M. T. Eddy, and R. G. Griffin,” Radio frequency-driven recoupling at high magic-angle spinning frequencies: Homonuclear recoupling sans heteronuclear decoupling,” J. Chem. Physics 128, 052321 (2008)

T. Maly, G. T. Debelouchina, V. S. Bajaj, K-N. Hu, C-G. Joo, M. L. Mak-Jurkauskas, J. R. Sirigiri, P. C. A. van der Wel, J. Herzfeld, R. J. Temkin and R. G. Griffin, “Dynamic Nuclear Polarization at High Magnetic Fields” J. Chem. Physics 128, 052211 (2008)

G. De Paëpe, J.R. Lewandowski, R. G. Griffin, “Spin dynamics in the modulation frame: Application to homonuclear recoupling in magic angle spinning solid-state NMR,” J. Chem. Physics 128 124503 (2008)

A. B. Barnes, G. De Paëpe, P.C.A. van der Wel, K-N. Hu, C-G. Joo, V. S. Bajaj, M. L. Mak-Jurkauskas, J. R. Sirigiri, J. Herzfeld, R. J. Temkin, and R. G. Griffin,” High Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR” Applied Magnetic Resonance 34, 237-263 (2008)

G. De Paëpe, J. R. Lewandowski, A. Loquet, A. Böckmann, R. G. Griffin, “Proton Assisted Recoupling and Protein Structure Determination” J. Chem. Physics 129, 245101 (2008)

2009

C-G. Joo, A. Casey, C.J. Turner and R.G. Griffin, “In Situ Temperature Jump Dynamic Nuclear Polarization: Enhanced Sensitivity in Two Dimensional 13C–13C Correlation Spectroscopy in Solution” J. Am. Chem. Soc. 131, 12-13 (2009)

V. S. Bajaj, P. C. A. van der Wel, and R. G. Griffin, “Observation of a Low-Temperature, Dynamically Driven, Structural Transition in a Polypeptide by Solid State NMR Spectroscopy” J. Am. Chem. Soc. 131, 118-121 (2009)

H. Zipse, E. Artin, S. Wnuk, G. J. S. Lohman, D. Martino, R.G. Griffin, S. Kacprzak, M. Kaupp, B.M. Hoffman, M. Bennati, J. Stubbe, N. Lees, “ Structure of the nucleotide radical formed during reaction of CDP/TTP with the E441Q-a2b2 of E. coli ribonucleotide reductase” J. Am. Chem. Soc. 131, 200-211(2009)

A. C. Sivertsen, M. J. Bayro; M. Belenky R.G. Griffin, J. Herzfeld, “Solid-state NMR evidence for inequivalent GvpA subunits in gas vesicles”, J. Mol. Biol. 387,1032-1039 (2009)

M. J. Bayro, M. Huber, R. Ramachandran, T. C. Davenport, B. H. Meier, M. Ernst and R. G. Griffin "Dipolar truncation in magic-angle spinning NMR recoupling experiments." J. Chem. Phys. 130, 114506 (2009)

J. Lin, M. Bayro, R. G. Griffin, and N. Khaneja, “Dipolar recoupling in solid state NMR by phase alternating pulse sequences” Jour. Magnetic Resonance 197, 145-152 (2009)

J. R. Lewandowski, G. De Paëpe, M. T. Eddy, R. G. Griffin, “15N-15N Proton Assisted Recoupling” J. Am. Chem. Soc., 131, 5769–5776 (2009)

E. L. Dane, T. Maly, G. T. Debelouchina, R. G. Griffin, and T.M. Swager,” Synthesis of a BDPA-TEMPO Biradical” Organic Letters 11, 1871-1874(2009)

A. B. Barnes, M. L. Mak-Jurkauskas, Y. Matsuki, V. S. Bajaj, P.C. A. van der Wel, R. Derocher, J. Bryant, J. R. Sirigiri, R. J. Temkin, J. Lugtenburg, J. Herzfeld, and R. G. Griffin,” Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization”, Jour. of Magnetic Resonance 198, 261–270 (2009)

V. S. Bajaj, M. L. Mak-Jurkauskas, M. Belenky, J. Herzfeld, R. G. Griffin, “Functional and Shunt States of Bacteriorhodopsin Resolved by 250 GHz Dynamic Nuclear Polarization-Enhanced Solid State NMR,” Proc. Nat’l Acad. Sci. USA 106, 9244-49 (2009)

Y. Matsuki, T. Maly, O. Ouari, S. Lyubenova, J. Herzfeld, T. Prisner, P. Tordo and R. G. Griffin,” Dynamic Nuclear Polarization using a Rigid Biradical”, Angewandte Chemie 48, 4996-5000 (2009)

J. R. Lewandowski, G. De Paëpe, M. T. Eddy, J. Struppe, W. Maas, and R. G. Griffin, “Proton Assisted Recoupling at High Spinning Frequencies”, J. Phys. Chem. B 113, 9062-69 (2009)

P.C.A. van der Wel, M. T. Eddy, R. Ramachandran, and Robert G. Griffin, “Targeted 13C-13C distance measurements in a microcrystalline protein via J-decoupled rotational resonance width measurements”, ChemPhysChem 10, 1656-63 (2009)

M. J. Bayro, T. Maly, N. R. Birkett, C. M. Dobson, and R. G. Griffin, ”Long-Range Aliphatic Correlations in Protein MAS NMR”, Angewandte Chemie 48, 5708-5710 (2009)

M. Aluas, C. Tripon, J. M. Griffin, X. Filip, V. Ladizhansky, R. G. Griffin, S. P. Brown, C. Filip, “CHHC and 1H-1H magnetization exchange: Analysis by experimental solid-state NMR and 11-spin density-matrix simulations”, Jour. of Magnetic Resonance 199,173-187 (2009)

A. B. Barnes, L. Andreas, M. Huber, R. Ramachandran, P.C.A. van der Wel, M. Veshtort, R.G. Griffin and M. A. Mehta, “High-Resolution Solid-State NMR Structure of Alanyl-Prolyl-Glycine“, Jour. of Magnetic Resonance 200,95–100(2009)