Mononuclear copper(II) complexes of alloferons 1 and 2: a combined potentiometric and spectroscopic studies |
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Authors: | Kowalik-Jankowska Teresa Biega Łukasz Kuczer Mariola Konopińska Danuta |
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Institution: | Faculty of Chemistry, University of Wroc?aw, Wroc?aw, Poland. terkow@wchuwr.chem.uni.wroc.pl |
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Abstract: | Mononuclear copper(II) complexes of the alloferon 1 His-Gly-Val-Ser-Gly-His-Gly-Gln-His-Gly-Val-His-Gly, alloferon 2 Gly-Val-Ser-Gly-His-Gly-Gln-His-Gly-Val-His-Gly, Ac-alloferon 1 Ac-His-Gly-Val-Ser-Gly-His-Gly-Gln-His-Gly-Val-His-Gly and Ac-alloferon 2 Ac-Gly-Val-Ser-Gly-His-Gly-Gln-His-Gly-Val-His-Gly have been studied by potentiometric, UV-vis, CD and EPR spectroscopic methods. The potentiometric and spectroscopic data shows that acetylation of the amino terminal group induces significant changes in the coordination properties of the Ac-alloferons 1 and 2 compared to the alloferons 1 and 2, respectively. The presence of four (Ac-alloferon 1) or three (Ac-alloferon 2) histidyl residues provides a high possibility for the formation of macrochelates via the exclusive binding of imidazole-N donor atoms. The macrochelation suppresses, but cannot preclude the deprotonation and metal ion coordination of amide functions and the CuH−3L species with {NIm, 3N−} bonding mode at pH above 8 are formed. The N-terminal amino group of the alloferons 1 and 2 takes part in the coordination of the metal ion and the 4N complex with {NH2, 3NIm} coordination mode dominates at physiological pH 7.4 for alloferon 1 and the 3N {NH2, CO, 2NIm} binding mode for alloferon 2. However, at higher pH values sequential amide nitrogens are deprotonated and coordinated to copper(II) ions. |
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Keywords: | Alloferon 1 Alloferon 2 Copper(II) complexes Stability constants Spectroscopic studies |
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