Structural dependencies of h3JNC′ scalar coupling in protein H-bond chains

The H-bond ((h3)J(NC')) and peptide bond ((1)J(NC')) scalar couplings establish connectivity of the electronic structure in the H-bond chains of proteins. The correlated changes of (h3)J(NC'), and (1)J(NC'), couplings extend over several peptide groups in the chains. Consequently, the electronic structure of the H-bond chains can affect (h3)J(NC'), in a manner that is independent of the local H-bond geometry. By taking this into account, and by using a more complete set of H-bond geometry parameters, we have predicted (h3)J(NC'), couplings in the H-bond chains with deviations commensurate to the standard deviations of the experimentally determined values. We have created a comprehensive database of (h3)J(NC') and (1)J(NC') couplings by measuring the coupling constants in ubiquitin (alphabeta-fold) intestinal fatty acid binding protein (beta-barrel) and carp parvalbumin (alpha-helical).