Secondary structure of peptides: 15. 13C n.m.r. CP/MAS study of solid elastin and proline-containing copolyesters |
| |
Authors: | Hans R Kricheldorf Detlef Müller |
| |
Institution: | Institut für Angewandte Chemie der Universität, Martin-Luther-King-Platz 6, D-2000 Hamburg 13, FRG;Bruker Analytische Messtechnik GmbH, Silberstreifen, D-7512 Rheinstetten/Fo., FRG |
| |
Abstract: | In order to study the chemical shifts and the cis—trans isomerism of prolyl units neighbouring glycine or other amino acids, 75.4 MHz13C nuclear magnetic resonance (n.m.r.) cross-polarization/magic angel spinning (CP/MAS) spectra of the following solid oligopeptides and sequence polypeptides were measured: Z-Gly-Pro-OH,Z-Gly-Pro-Gly-Gly-OEt,Z-Gly-Pro-Ala-Ala-OMe,(Gly-Pro-Gly)n,(Gly-Pro-Ala)n,(β-Ala-Pro)n and ). Whereas all these oligo- and polypeptided contain exclusively trans X-Pro bonds, both cis and trans peptide bonds were found in a polypeptide prepared by copolymerization of glycine- and in pyridine. On the basis of these model compounds, the 13C n.m.r. CP/MAS spectra of solid elastin allows the following conclusions. Almost all X-Pro bonds assume the trans conformation, most alanine and leucine units form α-helical chain segments, whereas only a small fraction of β-sheet structure is present. A 30.3 MHz 15N n.m.r. CP/MAS spectrum of solid elastin confirms that ~25% of all amino acids assume the α-helical structure. A model of elastin is discussed consisting of an amorphous phase, α-helical chain segments and helical segments of still unknown pitch. |
| |
Keywords: | Polypeptides copolypeptides secondary structure polyproline elastin |
本文献已被 ScienceDirect 等数据库收录! |
|