Infrared Spectra of Polypeptides and Related Compounds. I

Abstract

Infrared absorption spectra of nine polypeptides have been measured in the frequency region from 5000 to 600 cm.-1. There have been observed many bands common to all these polypeptides, but some of the bands appearing between 1200 and 800 cm.-1 were found to depend considerably on the sequence of amino acids in the polypeptide. It was concluded that in silk fibroin glycine and alanine residues are arranged alternately, although some authors prefer the at-random arrangement to the periodic arrangement.Many papers have been published on the infrared spectra of polypeptides and proteins.1•2 There are, however, many problems remaining to be solved as to the interpretation of the spectra in terms of the structure of polypeptides. Concerning these(1) G. B. B. M. Sutherland, Advances in Protein Chem., 7, 291 (1952),(2) L. J. Bellamy, "The Infrared Spectra of Complex Molecules," Methuen, London, 1954, Chapter 12.

Chemical composition and physical properties of Gonometa rufobrunnae silk

“…Therefore, the sharp absorption band at 965 cm-' should be related to the presence of alaninealanine linkages in the fibroin chain^.^^^'^ No evidence of either glycine-glycine linkage or glycinealanine periodic arrangement was found, whereas the presence of glycine-alanine random linkage in the amino acid sequence of G. rufobrunnae fibroin could not be excluded. 21 On the basis of these findings and taking into account the amino acid composition reported in Table I, we suggest that G. rufobrunnae silk fibroin should be regarded as a typical p silk as the other Lasiocampidae silks already ~haracterized. '','~…”

Wet spinning of Bombyx mori silk fibroin dissolved in N-methyl morpholine N-oxide and properties of regenerated fibres

“…This solvent, as well as other alcohols, is a well-known annealing agent able to induce SF crystallization by random-coil → ␤-sheet conformational transition [42]. Other weak but significant IR bands present in both native and regenerated fibres are those at 1015 and 1003-978 cm −1 , respectively attributed to Gly-Gly and Gly-Ala motifs which characterize the highly repetitive polypeptide sequence of SF [43,44].…”

Fabrication and characterization of nanofibrous scaffold developed by electrospinning

“…The SF Raw (Figure 8a) displayed a strong absorption band at 3239 cm -1 (NHstretching), assigned to the hydrogen bonded NH groups, in addition to the characteristic amide bands at 1698 and 1631 cm -1 (amide I), 1518 cm -1 (amide II), 1263 and 1231 cm -1 (amide III) assigned to the β sheet, as described elsewhere 44,45 . Spectra shows strong twin bands at 996 and 976 cm -1 however no bands at 1015 and 965 cm -1 which can be conclude that in the part of silk fibroin the glycine and alanine residues are arranged alternately just as in periodic sequence 46 . This conclusion is supported by the presence of sharp bands at 1631 and 1518 cm -1 in the amide I and II range, respectively.…”