The O-17-NMR shielding range and shielding time scale and detection of discrete hydrogen-bonded conformational states in peptides

The O-17-NMR shielding range and shielding time scale due to hydrogen-bondi ng interactions in peptides are critically evaluated relative to those of H -1-NMR. Furthermore, the assumptions and conclusions in previous O-17-NMR s tudies on the detection of discrete conformational states in peptides (V. T sikaris et al., Biopolymers, 2000, Vol. 53, pp. 135-139) are reconsidered. Consistent examination of the method demonstrates that although O-17 shield ings of peptide oxygens are very sensitive to hydrogen bonding interactions , the O-17-NMR shielding time scale is not advantageous compared to that of H-1-NMR, and thus it is not suitable for the detection of discrete hydroge n-bonded conformational states in peptides. O-17-NMR spectroscopy is prone to interpretation errors due to the formation of O-17-labeled impurities du ring the synthetic procedures (A. Steinschneider et al., International Jour nal of Peptide and Protein Research, 1981, Vol. 18 pp. 324-333). (C) 2001 J ohn Wiley & Sons, Inc.