Premium
Vibrational 13 C‐cross‐polarization/magic angle spinning NMR spectroscopic and thermal characterization of poly(alanine‐glycine) as model for silk I Bombyx mori fibroin
Author(s) -
Monti Patrizia,
Taddei Paola,
Freddi Giuliano,
Ohgo Kosuke,
Asakura Tetsuo
Publication year - 2003
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10408
Subject(s) - fibroin , silk , chemistry , magic angle spinning , random coil , bombyx mori , raman spectroscopy , crystallography , alanine , infrared spectroscopy , polymer chemistry , nuclear magnetic resonance spectroscopy , stereochemistry , amino acid , circular dichroism , materials science , organic chemistry , biochemistry , physics , optics , composite material , gene
This study focuses on the conformational characterization of poly(alanine‐glycine) II (pAG II) as a model for a Bombyx mori fibroin silk I structure. Raman, IR, and 13 C‐cross‐polarization/magic angle spinning NMR spectra of pAG II are discussed in comparison with those of the crystalline fraction of B. mori silk fibroin (chymotryptic precipitate, Cp) with a silk I (silk I‐Cp) structure. The spectral data give evidence that silk I‐Cp and the synthetic copolypeptide pAG II have similar conformations. Moreover, the spectral findings reveal that silk I‐Cp is more crystalline than pAG II; consequently, the latter contains a larger amount of the random coil conformation. Differential scanning calorimetry measurements confirm this result. N‐Deuteration experiments on pAG II allow us to attribute the Raman component at 1320 cm −1 to the amide III mode of a β‐turn type II conformation, thus confirming the results of those who propose a repeated β‐turn type II structure for silk I. The analysis of the Raman spectra in the νNH region confirms that the silk I structure is characterized by the presence of different types of H‐bonding arrangements, in agreement with the above model. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 329–338, 2003