HYDROGEN-BONDING AND DISTANCE STUDIES OF AMINO-ACIDS AND PEPTIDES USING SOLID-STATE 2D H-1-C-13 HETERONUCLEAR CORRELATION SPECTRA

Solid state C-13-H-1 2D HETeronuclear CORrelation spectra (Caravatti, P.; Bodenhausen, G.; Ernst, R. R. Chem. Phys. Lett. 1982, 89, 363-367. Roberts, J. E.; Vega, S.; Griffin, R. G. J. Am. Chem. Sec. 1984, 106, 2506-2512) are reported for many amino acids and peptides with C-13 i sotopic composition at natural abundance. These HETCOR spectra often h ave multiple proton cross peaks for each carbon, and these cross peaks can be extremely helpful for assigning the spectrum. Apart from peaks due to groups that have a lot of motion, the peak volumes correlate w ith C-H distance and can be used to estimate distances with standard d erivation of 0.2 Angstrom; the longest distances for which cross peaks are visible is 3 Angstrom. The HECTOR pulse sequence also appears to be very useful for studying hydrogen bonding interactions, since the d istances for most of C-O ... H-X hydrogen bond pairs are within the ra nge that is observable by HETCOR.