Copper(II) complexes of N-terminal protected tri- and tetra-peptides containing histidine residues |
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Authors: | Sanna Daniele Micera Giovanni Kallay Csilla Rigo Viktoria Sovago Imre |
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Institution: | Istituto CNR di Chimica Biomolecolare, Sezione di Sassari, trav. La Crucca 3, I-07040 Li Punti, Sassari, Italy. |
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Abstract: | Copper(II) complexes of peptides containing two or three histidyl residues (Ac-HisGlyHis-OH, Ac-HisGlyHis-NHMe, Ac-HisHisGlyHis-OH and Ac-HisHisGlyHis-NHMe) have been studied by potentiometric, UV-Vis, EPR and CD spectroscopic measurements. The imidazole nitrogen atoms are described as the primary metal binding sites of all ligands resulting in the formation of various macrochelates in the pH range 4 to 7. The (Nim, N-, Nim)-co-ordinated CuH-1L]0+ complexes were mainly detected in samples containing free carboxylates at the C-termini, whilst the CuH-2L]-(0) complexes were the predominant species in slightly alkaline solution and their binding modes were described via 4N-co-ordination (Nim, N-, N-, Nim) in (7,5,6)-membered fused chelate rings. Deprotonation and co-ordination of the third amide nitrogens were detected above pH approximately 9 in all cases. |
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