Nuclear Magnetic Resonance is one of the most powerful spectroscopic tools in identifying chemical structure. Unfortunately, its inherent small nuclear Zeeman polarization causes NMR to be a low sensitivity technique. To combat this sensitivity issue the Griffin Group has pioneered the advancement of high field Dynamic Nuclear Polarization NMR using high frequency high power microwave devices (i.e., Gyrotrons), low temperatures and magic-angle spinning NMR probes. DNP was initially proposed by Overhauser and demonstrated at low magnetic fields (i.e., < 1 T) by Carver and Slichter.
DNP relies on the transfer of electron polarization (typically from an organic based exogenous radical) to neighboring nuclei offering significant gains in sensitivity, for example 1H can achieve a theoretical enhancement of ~660 using this technique. Since the early 1990’s we have been developing methods and instrumentation to improve sensitivity for chemical systems by orders of magnitude (i.e., 10 to ~103) using high field (i.e., 5 to 18.8 T) Dynamic Nuclear Polarization. The sensitivity enhancement from DNP enables acquisition of NMR spectra and structural parameters that are otherwise not available. These methods are widely applicable to biological solids including peptides, nanocrystals, membrane proteins and amyloid fibrils – offering further constraints not possible using ssNMR alone.
Figure 1: Various radicals that are used for Dynamic Nuclear Polarization
We currently house five home-built high field DNP NMR spectrometers within the Francis Bitter Magnetic Laboratory. Three of these are on-line and include the 211 MHz / 140 GHz, 380 MHz / 250 GHz and 699 MHz / 460 GHz instruments. Two additional units are being assembled and should be on-line by 2015, including a 500 MHz / 330 GHz and an 800 MHz / 527 GHz.
A Few Recent DNP NMR Publications:
108.) B. Corzilius, V.K. Michaelis, S.A. Penzel, E. Ravera, A.A. Smith, C. Luchinat, R.G. Griffin "Dynamic nuclear polarization of 1H, 13C, and 59Co in a tris(ethylenediamine)cobalt(III) crystalline lattice doped with Cr(III)" J. Am. Chem. Soc. 136, 11716-11727 (2014) DOI: 10.1021/ja5044374
94.) V.K. Michaelis, T.-C. Ong, M.K. Kiesewetter, D.K. Frantz, J.J. Walish, E. Ravera, C. Luchinat, T.M. Swager, R.G. Griffin "Topical developments in high-field dynamic nuclear polarization" Israel J. Chem. 54, 207-221 (2014) DOI: 10.1002/ijch.201300126
93.) G. Debelouchina, M.J. Bayro, A.W. Fitzpatrick, M.M. Rosay, V. Ladizhansky, M.A. Caporini, C.P. Jaroniec, V.S. Bajaj, C. MacPhee, W.E. Maas, C.M. Dobson, R.G. Griffin, “Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy ” J. Am. Chem. Soc. 135, 19237-19247 (2013) DOI: 10.1021/ja409050a
84.) Qing Zhe Ni, Eugenio Daviso, Thach V. Can, Evgeny Markhasin, Sudheer K. Jawla, Timothy M. Swagerb, Richard J. Temkin, Judith Herzfeld, and Robert G. Griffin, “High Frequency Dynamic Nuclear Polarization” Accounts of Chemical Research 46, 1933–1941 (2013) DOI: 10.1021/ar300348n
78.) E. Ravera,B. Corzilius,V. K. Michaelis, C. Rosa, R.G. Griffin, C. Luchinat, and I. Bertini, “Dynamic Nuclear Polarization of Sedimented Solutes”, J. Am. Chem. Soc., 135, 1641−1644 (2013) DOI: 10.1021/ja312553b PMCID: PMC3578289
Current High Field DNP NMR Systems Online
Current High Field DNP NMR Systems under Construction