13C-NMR chemical shift tensor and hydrogen-bonded structure of glycine-containing peptides in a single crystal

C-13-nmr chemical shift tensor components are reported for a C-13-labeled Gly(1) amide carbonyl carbon of a glycylglycine (Gly(1)Gly(2)) single crystal, a GlyGly . HNO3 single crystal and a GlyGly . HCl . H2O single crystal, for which the three-dimensional crystal structures have already been determined by x-ray diffraction. The tensor components were measured by changing the angle between the crystal plane and the applied magnetic field by using a goniometer designed in this work for use in conventional C-13 cross-polarization/magic angle spinning nmr probe. From these experimental data, the principal values of the C-13 chemical shift tensor and its directions for the Gly(1) amide carbonyl carbon were determined It was found that the C-13 chemical shift tensor components (delta(11), delta(22), and delta(33)) for the Gly(1) amide carbonyl carbon in GlyGly and GlyGly . HNO3 with a >NH ... O=C< type of hydrogen bond depend on the hydrogen-bond length and the directions of the delta(22) components of these peptides are along the hydrogen-bonded >C=O bond axis. In addition, the magnitude of the deviation from the bond axis depends on the hydrogen-bond angle. Further the experimental result for GlyGly . HCl . H2O with a-O-H ... O=C< type of hydrogen bond was discussed. (C) 1999 John Wiley & Sons, Inc.