Dependence of melittin structure on its interaction with multivalent anions and with model membrane systems.

摘要: The conformation and the aggregation state of melittin were investigated in aqueous solutions having different pH values ionic composition as well upon interaction with phospholipids. While circular dichroism could only show existence, solution, either a random-coil or right-handed helical conformation, high resolution 1H 13C n.m.r. spectra, together results photon correlation spectroscopy, produced evidence favour number well-defined structural states, depending on anion concentration charge pH. In pure water at neutral appeared to exist flexible random-cell monomer; dilute NaCl monomeric form was found which still essentially unordered, but presented pronounced rigidity structure, be approximated prolate ellipsoid. When divalent anions present (or when strengths reached even monovalent anions) molecules associated into compact disc-like tetramer; by 31P n.m.r., correlations established between binding phosphate ions variations structure polypeptide chains. As alkaline tetramer also found, different, however, from that formed presence Upon phospholipids, can visualized, similarly what happens solutions, consisting bent helix, grouping polar residues along one face molecule. glutamine lysine strongly immobilized, while there no for any self-aggregation peptide; ability induce dichromate efflux phospholipid vesicles fact higher peptide than tetrameric one.