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

Abstract

The 13C NMR chemical shift( δ CO) 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(ø, ψ) in the vicinity of the α-helix conformation were made by using the linear relationship between the δ CO and hydrogen-bond length ( R N·O) as reported previously. In order to ascertain whether the obtained contour maps reasonably explain the experimental 13C 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).