The relationship between the helical conformation and C-13 NMR chemical shift of amino acid residue carbonyl carbons of polypeptides in the solid state

The C-13 NMR chemical shift (delta(C=0)) contour maps of Gly, L-Ala, L-Val, L-Leu and L-Asp amino acid residue carbonyl carbons in polypeptides as functions of the dihedral angles (phi, psi) in the vicinity of the alpha-helix conformation were made by using the linear relationship between the delta(C=0) and hydrogen-bond length (R-N ... O) as reported previously. In order to ascertain whether the obtained contour maps reasonably explain the experimental C-13 chemical shift behavior or not, the conformational analysis has been carried out for helical polypeptides containing Gly, L-Ala, L-Val and L-Leu amino acid residues and for small proteins such as basic pancreatic trypsin inhibitor (BPTI). (C) 1997 Elsevier Science B.V.