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High‐Precision Measurement of Hydrogen Bond Lengths in Proteins by Nuclear Magnetic Resonance Methods

We have compared hydrogen bond lengths on enzymes derived with high precision (≤ ±0.05 Å) from both the proton chemical shifts (δ) and the fractionation factors (ϕ) of the proton involved with those obtained from protein X‐ray crystallography. Hydrogen bond distances derived from proton chemical shifts were obtained from a correlation of 59 O—H····O hydrogen bond lengths, measured by small molecule high‐resolution X‐ray crystallography, with chemical shifts determined by solid‐state nuclear magnetic resonance (NMR) in the same crystals (McDermott A, Ridenour CF, Encyclopedia of NMR, Sussex, U.K.: Wiley, 1996:3820–3825). Hydrogen bond distances were independently obtained from fractionation factors that yield distances between the two proton wells in quartic double minimum potential functions (Kreevoy MM, Liang TM, J Am Chem Soc, 1980;102:3315–3322). The high‐precision hydrogen bond distances derived from their corresponding NMR‐measured proton chemical shifts and fractionation factors agree well with each other and with those reported in protein X‐ray structures within the larger errors (±0.2–0.8 Å) in distances obtained by protein X‐ray crystallography. The increased precision in measurements of hydrogen bond lengths by NMR has provided insight into the contributions of short, strong hydrogen bonds to catalysis for several enzymatic reactions. Proteins 1999;35:275–282. © 1999 Wiley‐Liss, Inc.