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Dalton Trans. 2017 Jun 27;46(25):8157-8166. doi: 10.1039/c7dt00884h.

Exploring the boundaries of direct detection and characterization of labile isomers - a case study of copper(ii)-dipeptide systems.

Author information

1
Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary. gyurcsik@chem.u-szeged.hu and PhD Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Japan.
2
Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Magyar tudósok körútja 2, Hungary.
3
Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Magyar tudósok körútja 2, Hungary and Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Spintronics Research Group (PROSPIN), P.O. Box 91, H-1521 Budapest, Hungary.
4
Department of Physical Chemistry and Material Sciences, University of Szeged, Aradi Vértanuk tere 1, H-6720 Szeged, Hungary.
5
Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary. gyurcsik@chem.u-szeged.hu.

Abstract

The investigation of the linkage isomers of biologically essential and kinetically labile metal complexes in aqueous solutions poses a challenge, as these microspecies cannot be separately studied. Therefore, derivatives are commonly used to initially determine the stability or spectral characteristics of at least one of the isomers. Here we directly detect the isomers, describe the metal ion coordination sphere, speciation and thermodynamic parameters by a synergistic application of temperature dependent EPR and CD spectroscopic measurements in copper(ii)-dipeptide systems including His-Gly and His-Ala ligands. The ΔH = (-23 ± 4) kJ mol-1 value of the standard enthalpy change corresponding to the peptide-type to histamine-type isomerisation equilibrium of the [CuL]+ complex was corroborated by several techniques. The preferential coordination of the side-chains was observed at lower temperatures, whereas, metal-binding of the backbone atoms became favourable upon increasing temperature. This study exemplifies the necessity of using temperature dependent multiple methodologies for a reliable description of similar systems for upstream applications.

PMID:
28607997
DOI:
10.1039/c7dt00884h
[Indexed for MEDLINE]

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