Structural dependencies of ^h3J_NC′ scalar coupling in protein H-bond chains

The H-bond (^h3J_NC′) and peptide bond (¹J_NC′) scalar couplings establish connectivity of the electronic structure in the H-bond chains of proteins. The correlated changes of ^h3J_NC′ and ¹J_NC′ couplings extend over several peptide groups in the chains. Consequently, the electronic structure of the H-bond chains can affect ^h3J_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 ^h3J_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 ^h3J_NC′ and ¹J_NC′ couplings by measuring the coupling constants in ubiquitin ($β-fold) intestinal fatty acid binding protein (β-barrel) and carp parvalbumin (α-helical).