13C‐nmr chemical shift and conformation of L‐alanine residues incorporated into poly(β‐benzyl L‐aspartate) in the solid state

Abstract

Abstract13C‐nmr spectra of poly(β‐benzyl L‐aspartate) containing 13C‐enriched [3‐13C]L‐alanine residues in the solid state were recorded by the cross polarization–magic angle spinning method, in order to elucidate the conformation‐dependent 13C chemical shifts of L‐alanine residues taking various conformations such as the antiparallel β‐sheet, the right‐handed α‐helix, the left‐handed α‐helix, and the left‐handed ω‐helix forms obtained by appropriate treatment. The latter two conformations for L‐alanine residues are achieved when L‐alanine residues are incorporated into poly(β‐benzyl L‐aspartate). We found that the alanine Cβ carbon show significant 13C chemical shift displacement depending on conformational change, and gave the 13C chemical shift values at about 17 ppm for the left‐handed ω‐helix, 14 ppm for the left‐handed α‐helix, 15.5 ppm for the right‐handed α‐helix, and 21.0 ppm for the antiparallel β‐sheet relative to tetramethylsilane.