NMR studies of strong hydrogen bonds in enzymes and in a model compound

Hydrogen bond lengths on enzymes have been derived with high precision (les s than or equal to +/- 0.05 Angstrom) from both the proton chemical shifts (delta) and the fractionation factors (phi) of the proton involved and were compared with those obtained from protein X-ray crystallography. Hydrogen bond lengths derived from proton chemical shifts were obtained from a corre lation of 59 O-H ... O hydrogen bond lengths, measured by small molecule hi gh resolution X-ray crystallography, with chemical shifts determined by sol id-state NMR in the same crystals [A. McDermott, C.F. Ridenour, Encyclopedi a of NMR, Wiley, Sussex, England, 1996, 3820pp]. Hydrogen bond lengths were independently obtained from fractionation factors which yield distances be tween the two proton wells in quartic double minimum potential functions [M .M. Kreevoy, T.M. Liang, J. Am. Chem. Sec. 102 (1980) 3315]. The high preci sion hydrogen bond lengths derived from their corresponding NMR-measured pr oton chemical shifts and fractionation factors agree well with each other a nd with those reported in protein X-ray structures within the larger errors (+/-0.2-0.8 Angstrom) in lengths obtained by protein X-ray crystallography . The increased precision in measurements of hydrogen bond lengths by NMR h as provided insight into the contributions of short, strong hydrogen bonds to catalysis for several enzymes including ketosteroid isomerase, triosepho sphate isomerase, and serine proteases. The O-H ... O hydrogen bond length derived from the proton chemical shift in a model dihydroxy-naphthalene com pound in aqueous solution agreed well with lengths of such hydrogen bands d etermined by high resolution, small molecule X-ray diffraction. (C) 2000 El sevier Science B.V. All rights reserved.