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Copper ion complex formation of polypeptide containing side‐chain pyridyl groups
Author(s) -
Nagata Yoshitomo,
Kanuka Satoru,
Kinoshita Takatoshi,
Takizawa Akira,
Tsujita Yoshiharu,
Yoshimizu Hiroaki
Publication year - 1994
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.360340603
Subject(s) - chemistry , side chain , intramolecular force , helix (gastropod) , crystallography , monomer , molecule , copper , pyridine , stereochemistry , chelation , ion , inorganic chemistry , medicinal chemistry , organic chemistry , polymer , ecology , snail , biology
The complex formation behaviors of an α‐helical polypeptide containing pyridyl ligands in the side chains, poly (N ω ‐2‐pyridylmethyl L ‐glutamine) (P2PG), were investigated by absorption and CD spectroscopy using Cu 2+ ion as a guest molecule in 2,2,2‐trifiuoroethanol solution. In the low Cu 2+ ion concentration, P2PG exhibited the predominant formation of Cu 2+ and two pyridyl side‐chain complexes, involving a regular arrangement of the pyridyl side chains. On the other hand, the complexes were converted to Cu 2+ and one pyridyl side‐chain species with increasing Cu 2+ ion concentration. The conversion was accompanied by the disappearance of the side‐chain ordered structure without any changes in the backbone conformation. Moreover, the still remaining coordination sites of Cu 2+ were capable of complexing monomer pyridine (Py) added as a second guest to form ternary complexes, P2PG‐Cu 2+ ‐Py, following the reconstitution of the ordered structure on the periphery of the α‐helix backbone. The unique characteristics of P2PG can be explained in terms of the restriction of the pyridyl side chains to form intramolecular chelate complexes, depending on the rigid α‐helix conformation. © 1994 John Wiley & Sons, Inc.