Vibrational Spectrum of the Unordered Keratin Polypeptide Chain: A Raman Study of Feather

Raman spectra of native and solubilized feather keratin have been obtained, and the amide I and amide 111 regions have been analyzed by band resolution techniques. The amide I region of the native form indicates that at least 64% of the protein has an antiparallel chain pleated sheet structure, the remainder being unordered. For the solubilized keratin all of the protein is in an unordered state. The amide I11 region is not as easily analyzed into component contributions. Normal vibration analyses on N-acetyl-L-alanine-N-methylamide support the conclusion that the amide 111 region is not as satisfactory as the amide I region in characterizing unordered structures. Even in the latter case caution must he used, since the observed amide I band is an average over the conformational distribution in the particular unordered system.