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Block oligopeptides ( L ‐lysyl) m ‐( L ‐alanyl) n ‐ L ‐Tyrosyl‐( L ‐Alanyl) n ‐( L ‐Lysyl) m . II. Circular dichroism and pulsefluorimetry conformational studies
Author(s) -
Mayer R.,
Gauduchon P.,
Spach G.,
Wahl Ph.
Publication year - 1978
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.1978.360170207
Subject(s) - chemistry , circular dichroism , fluorescence , peptide , quenching (fluorescence) , oligopeptide , lysine , aqueous solution , chromophore , ionic strength , solvent , stereochemistry , crystallography , amino acid , organic chemistry , biochemistry , physics , quantum mechanics
The conformation of chromatographically pure block oligopeptides ( L ‐lysyl) m ‐( L ‐alanyl) n ‐ L ‐tyrosyl‐( L ‐alanyl) n ‐( L ‐lysyl) m with n = 3 and m = 6 or 3 is investigated. By circular dichroism it is shown that these peptides may exhibit a partially α‐helical structure depending upon pH, ionic strength, solvent, and temprerature. An attempt is made to describe the helical content of these small peptides by utilizing the data obtained on high‐molecular‐weight poly( L ‐lysine). By measurement of the quantum yield and the decays of the peptides fluorescence, it is shown that, in aqueous solution, at neutral pH, the fluorescence of the peptides is quenched by interactions with the peptide carbonyl groups. The decays are multiexponential, which shows the presence of several conformations of the phenolic chromophore relative to the peptide chain. The addition of methanol, which induced the helix formation, decreases the quenching of the fluorescence and the multiexponential character of the decays. In presence of sodium hydroxide, which further increases the helical content of the peptides, a dynamic quenching occured that can be attributed to interactions between the phenol hydroxyl group of tyrosine ( i th residue) and the ε‐amino groups of the ( i +4)th and ( i ‐4)th lysyl residues.