Structural dependencies of protein backbone ²J _NC′ couplings

Protein folding can introduce strain in peptide covalent geometry, including deviations from planarity that are difficult to detect, especially for a protein in solution. We have found dependencies in protein backbone ²J_NC′ couplings on the planarity and the relative orientation of the sequential peptide planes. These dependences were observed in experimental ²J_NC′ couplings from seven proteins, and also were supported by DFT calculations for a model tripeptide. Findings indicate that elevated ²J_NC′ couplings may serve as reporters of structural strain in the protein backbone imposed by protein folds. Such information, supplemented with the H-bond strengths derived from ^h3J_NC′ couplings, provides useful insight into the overall energy profile of the protein backbone in solution. Published by Cold Spring Harbor Laboratory Press.