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Conformation of oligopeptides with L ‐leucyl‐ L ‐leucyl‐ L ‐alanyl and L ‐methionyl‐ L ‐methionyl‐ L ‐leucyl repeating units
Author(s) -
Katakai Ryoichi,
Iizuka Yasuko
Publication year - 1984
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.360230722
Subject(s) - chemistry , oligopeptide , peptide , circular dichroism , helix (gastropod) , amino acid , stereochemistry , solvent , precipitation , crystallography , biochemistry , ecology , physics , snail , meteorology , biology
The conformation of oligopeptides with hydrophobic side chains, Nps‐( L ‐Leu‐ L ‐Leu‐ L ‐Ala) n ‐OEt and Nps‐( L ‐Met‐ L ‐Met‐ L ‐Leu) n ‐OEt( n = 1–6), in the solid state, obtained either by evaporation of the solvent or by precipitation with diethyl ether from a 1,1,1,3,3,3‐hexafluoropropan‐2‐ol (HFIP) solution, has been studied with ir spectroscopy and x‐ray powder‐diffraction measurements. The conformation of these peptides in the HFIP solution has been studied by CD spectroscopy. Due to a strong preference of the amino acids to form an α helix, the peptides begin forming α helices at the dodecapeptide in the HFIP solution, and in the solid state by evaporation. In the solid state, with precipitation, the α‐helical conformation is first observed at the octadecapeptide and the lower peptides assume a β structure. The conformational change, from the α helix to the β structure of the peptides with 12 to 15 amino acid residues, during the precipitation process, is due to a strong tendency of the amino acids to form the β‐structure in rather short peptide lengths.