Abstract: | Theoretical calculations of the heteronuclear vicinal coupling constant 3J(13C′NCαH) 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′NCαH) = A cos2 θ + B cos θ + C, where A, B, and C are constants and θ is related to the torsional angle ? 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. |