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 isotopic composition at natural abundance. These HETCOR spectra often have 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 with C-H distance and can be used to estimate distances with standard derivation 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 distances for most of C-O ... H-X hydrogen bond pairs are within the range that is observable by HETCOR.