Conformational dependence of vicinal ¹³C'NC^αH coupling constants in peptides: a dirac vector model investigation

Abstract

Theoretical calculations of the heteronuclear vicinal coupling constant ³J(¹³C'NC^αH) in peptides have been carried out using the Dirac vector model. The results showed an angular dependence for this coupling constant, which can be expressed in the form ³J(¹³C'NC^αH) = Acos²θ + Bcosθ + C, where A, B, and C are constants and θ is related to the torsional angle Φ of the peptide backbone. The results of the present calculations are in very good agreement with those obtained using finite perturbation theory at the INDO level of approximation.