The goal of this project is the characterization of low-barrier hydrogen bonds in serine proteases and model compounds utilizing NMR spectroscopic techniques. Chymotrypsin, with various inhibitors (including N-acetyl-L-leucyl-L-phenylalanyl-trifluoromethyl ketone) will be studied by proton NMR to evaluate the low-field chemical shifts in buffer solutions such as acetate, formate and succinate. The deuterium chemical shift values of chymotrypsin amd chymotrypsin complexed with specific inhibitors are also of interest, and will be examined. A series of acetic acid derivatives in 1:1 complexes with N-methylimidazole is also under investigation. These complexes are proposed to model the histidine-aspartate coupling in chymotrypsin and will be studied by proton and deuterium NMR in order to examine the low-field chemical shift values. Other intramolecular model compounds will be studied to examine the low-field chemical shifts. The model compounds will be prepared in solvents such a chloroform, methylene chloride and benzene.