The stoichiometry, stability constants and solution structure of the complexes formed in the reaction of copper(II) with oligopeptides containing histidyl residues at the C-termini (Gly3His, Gly4His and Gly5His) have been determined by potentiometric, UV–VIS and EPR spectroscopic methods. The formation of the species [CuHL]2+, [CuL]+, [CuH−1L], [CuH−2L]– and [CuH−3L]2− was detected in all cases. Binding modes of the species [CuL]+, [CuH−1L] and [CuH−2L]− were characterized by the metal ion co-ordination of the terminal amino group, carbonyl oxygen or one or two deprotonated amide nitrogens in joined five-membered chelates from the N-termini, while the fourth co-ordination site of the metal ion was occupied by nitrogen donors of imidazole in the form of a macrochelate. The stability of the macrochelate was decreased upon increasing the length of the peptide molecule. For the penta- and hexa-peptides the species [CuH−3L]2− was characterized as a 4N-complex with equatorial co-ordination of the terminal amino group and subsequent three deprotonated amide nitrogens, with unco-ordinated imidazolyl residues, while a 5N-species was suggested to form for Gly3His with axial interaction of the imidazole-N donor atom. Copper(II) complexes of Gly2His and pentaglycine were also investigated for reliable comparison.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?