Influence of thermal motion on H-1 chemical shifts in proteins: The case of bovine pancreatic trypsin inhibitor

The possible influence of thermal motion on H-1 chemical shifts is discusse d for a small stable protein, the bovine pancreatic Kunitz trypsin inhibito r (BPTI). The thermal effects on the aromatic side chains and on the backbo ne are treated separately. The thermal motion of the aromatic side chains i s accounted for in terms of their rotation around the C-alpha-C-beta bond a nd the motion of each individual proton is interpreted as a ratio between t he amount of ordered and quite disordered states. The influence of hydrogen bonds is introduced as an extra contribution to the chemical shifts of the bonded proton. Their contribution to the chemical shifts resulting from th e polarization of the peptide bond is investigated, as is their influence o n local flexibility. Finally, the relative importance of each contribution to the chemical shift information is compared. Copyright (C) 2001 European Peptide Society and John Wiley & Sons, Ltd.