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Circular dichroic studies on Cu(II) interactions with a protamine, scylliorhinine Z 3
Author(s) -
Kozlowski H.,
Aubert J. P.,
Gusse M.,
Chevaillier P.,
LoucheuxLefebvre M. H.
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.360230708
Subject(s) - chemistry , dichroic glass , crystallography , protamine , chelation , metal , complex formation , nitrogen , molar ratio , stereochemistry , inorganic chemistry , copper , organic chemistry , catalysis , heparin , biochemistry , materials science , nanotechnology
The interaction of Cu(II) with the protamine scylliorhinine Z 3 was studied by means of CD measurements. At a 1:1 molar ratio, three complexes are formed. (1) In the pH range 5–6.5, the results suggest the formation of a five‐membered chelate ring through the coordination of two nitrogen atoms, the N‐terminal and the contiguous peptide nitrogen. (2) At pH ≥ 6.4, there is involvement of the lateral NH 2 group of Arg; at pH 6.5–8, the formation of a 3N cupric complex is strongly suggested. (3) At pH ≥ 8, results indicate the formation of a 4N complex as a major species in Cu(II)‐Z 3 solution. The transformation from a 2N to a 3N complex, and from a 3N to a 4N complex was followed with the help of the σ(αNH 2 ) → Cu(II) charge‐transfer dichroic band transitions. At Cu(II):Z 3 molar ratios ≥ 2 and at pH > 8, a new dichroic band appears, indicating the involvement of the tyrosine residue side chain in metal‐ion complexation.