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Cu II Ion Coordination to an Unprotected Pentadecapeptide Containing Two His Residues: Competition Between the Terminal Amino and the Side‐Chain Imidazole Nitrogen Donors
Author(s) -
Conato Chiara,
Kamysz Wojciech,
Kozłowski Henryk,
Łuczkowski Marek,
Mackiewicz Zbigniew,
Mancini Francesca,
Młynarz Piotr,
Remelli Maurizio,
Valensin Daniela,
Valensin Gianni
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200200551
Subject(s) - chemistry , protonation , imidazole , stability constants of complexes , stoichiometry , electron paramagnetic resonance , copper , ligand (biochemistry) , crystallography , ion , calorimetry , nitrogen , complex formation , bioinorganic chemistry , histidine , inorganic chemistry , side chain , stereochemistry , amino acid , organic chemistry , biochemistry , physics , receptor , nuclear magnetic resonance , thermodynamics , polymer
The complex‐formation equilibria of the pentadecapeptide TLEGTKKGHKLHLDY, the 114−128 protein fragment of SPARC, with the Cu II ion have been investigated, at I = 0.1 mol·dm −3 (KNO 3 ) and T = 298.2 K. Protonation and complex‐formation constants have been determined potentiometrically, and formation enthalpies measured by direct solution calorimetry; the complex‐formation model and species stoichiometry have been carefully checked by means of UV/Vis absorption, CD and EPR spectroscopy. The structure hypotheses of the complex species are also based on detailed study of the 1 H and 13 C NMR spectra of the ligand in both the absence and presence of copper ions. The involvement in complex‐formation of both the terminal amino and imidazole groups has been suggested and their specific behaviour at different pH values elucidated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)