Conformation of Cyclolinopeptide A Observed by Nuclear Magnetic Resonance Spectroscopy
AUTOR(ES)
Brewster, Anne I.
RESUMO
The 220 MHz spectrum of the cyclic nonapeptide Phe-Phe-Leu-Ile-Ile-Leu-Val-Pro-Pro (all L), designated cyclolinopeptide A, is analyzed by decoupling, exchange of peptide NH protons with deuterium, and measurement of the temperature dependence of the NH chemical shift. Measurement of the NH doublet spacings gives values of JNα, the vicinal coupling of α-CH and NH protons of specific amino acid residues. These in turn provide estimates of the rotation angles [unk] about the HN—CαHα bonds, which in combination with energy minimization studies, allow the determination of the conformation of the main chain. It is concluded that this polypeptide in dimethylsulfoxide solution does not contain intramolecular hydrogen bonds. Deuterium-exchange rates and temperature-dependence studies indicate that of the seven peptide NH protons, five are exposed to solvent, while two, which exchange somewhat more slowly than the others, may be situated in the interior of the ring.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=389153Documentos Relacionados
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