Premium
Conformation of malformin A: A proton magnetic resonance and a circular dichroism study
Author(s) -
Ptak Marius
Publication year - 1973
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.1973.360120711
Subject(s) - chemistry , circular dichroism , intramolecular force , crystallography , molecule , proton nmr , proton , resonance (particle physics) , stereochemistry , organic chemistry , quantum mechanics , particle physics , physics
Malformin A is a cyclic pentapeptide with an intramolecular disulfide bridge. The conformation in solution of this molecule has been studied by NMR and CD. The 270 MHz Proton spectrum in dimethyl sulfoxide is well resolved and the peaks corresponding to the five residues have been assigned. From the temperature dependence of chemical shifts of the peptide protons and from the exchange rate of these protons, it is concluded that the NH proton of one Cys is shielded from the solvent. This observation and HN α CH angles, estimated from the corresponding coupling constants, a proposed conformation of the peptide backbone. From the H β C α CH coupling constants, a P chirality for the disulfide bridge is proposed. Such a conformation is confirmed by the circular dichroism spectrum which shows a negative band at λ > 250 nm. It is concluded that the conformation of malformin A is rigid and that the disulfide bridge is exposed to interact with biological receptors.