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Conformational properties of L ‐leucine, L ‐isoleucine, and L ‐norleucine side chains in L ‐lysine copolymers
Author(s) -
Arfmann H.A.,
Labitzke R.,
Wagner K. G.
Publication year - 1977
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.1977.360160815
Subject(s) - norleucine , chemistry , isoleucine , circular dichroism , helix (gastropod) , stereochemistry , leucine , steric effects , side chain , residue (chemistry) , crystallography , monomer , amino acid , organic chemistry , biochemistry , polymer , ecology , snail , biology
The structure inducing properties of L ‐leucine, L ‐isoleucine, and L ‐norleucine residues incorporated into poly( L ‐lysine) were investigated by the observation of the circular dichroism of the respective random copolypeptides. The comparison involves the coil‐helix transition in water/methanol mixtures, the formation of ordered structures at higher pH, and the kinetics of the α‐helix to β‐conformation transition of the leucine and norleucine copolymers induced by temperature changes at pH 10.5. The results confirm the known properties of the leucine residue, strongly supporting the α‐helix conformation. They also support the idea that the isoleucine residue is one of the most powerful candidates for β‐structure formation, and they show that the unbranched norleucine residue has intermediate properties. The results are discussed on the basis of steric and hydrophobic properties of the three side chains.