Raman spectrum of model peptide (Ala-Gly)15 for Bombyx mori silk fibroin with Silk I form and theoretical calculation according to repeated β-turn type II structural model

Abstract

We observed Raman spectra of Silk I and Silk II powders of (Ala-Gly)15, which is a model peptide of crystalline region of Bombyx mori silk fibroin. Additionally Raman spectra of Ac-(Gly-Ala)4-NHMe and Ac-(Gly-Ala)3-NHMe with Silk I and Silk II forms were calculated according to the repeated β-turn type II structural model and β-sheet model, respectively. The ab initio molecular orbital calculation was used for the theoretical calculation. The calculated results could reproduce the spectra. Especially, in silk I form, observation of splitting of amide I and III bands was in agreement with the predicted bands according to the repeated β-turn type II structural model.