Recent findings in our laboratory demonstrate that 17O nmr is a highly sensitive probe for structural and dynamic investigations of amino acids and peptides in the solid state. The 17O nmr spectrum of glycine in a single crystalline form reveals five 17O transitions each consisting of two lines due to inequivalency of the oxygen atoms in the unit cell, and each of these lines reveals a dipolar doublet structure due to hydrogen bonding interactions between the 17O and the nearest hydrogen atom. The spectral width was found to be of the order of magnitude of MHz and the line widths of the order of magnitude of 2 kHz. Thus, the transition frequencies may be determined at the very high precision of 0.2% (200 Hz). As a result, the chemical shift and electric field tensors, the nuclear quadrupolar coupling, and the 17O - 1H and 17O - 13C coupling tensors can be determined. The same feature of 17O, the nuclear quadrupole moment and the resulting large nuclear quadrupolar coupling, that was considered a drawback earlier may now be utilized as a highly precise probe in structural and dynamic studies of peptides and proteins. We propose to focus our studies during the first three year grant period on the structural and dynamic properties of melanocyte stimulating hormone release inhibiting factor (Pro-Leu-Gly-NH2) (MIF), its constituent amino acids, and several linear and cyclic dipeptides (diketopiperazines), 17O labeled at the peptide carbonyl, carboxyl, and carboxamide groups. Intra- and internuclear distances, their spatial orientation and dynamics of motion will be determined. We hope to pursue these studies in the future to larger molecules such as peptide hormones and proteins.
| Tritt-Goc, J; Goc, R; Ponnusamy, E et al. (1989) 17O, 14N and 15N n.m.r. studies of the Co2+ complexes of cyclo(Pro17O-Gly15N) and cyclo(Gly17O-Pro) in aqueous solution. Int J Pept Protein Res 34:299-305 |
