The protein amide 1HN chemical shift temperature coefficient reflects thermal expansion of the N-H•••O=C hydrogen bond

The protein amide H-1(N) chemical shift temperature coefficient can be determined with high accuracy by recording spectra at different temperatures, but the physical mechanism responsible for this temperature dependence is not well understood. In this work, we find that this coefficient strongly correlates with the temperature coefficient of the through-hydrogen-bond coupling, (3h)J(NC'), based on NMR measurements of protein GB3. Parallel tempering molecular dynamics simulation suggests that the hydrogen bond distance variation at different temperatures/replicas is largely responsible for the H-1(N) chemical shift temperature dependence, from which an empirical equation is proposed to predict the hydrogen bond thermal expansion coefficient, revealing responses of individual hydrogen bonds to temperature changes. Different expansion patterns have been observed for various networks formed by beta strands.