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Drastic Effect of the Peptide Sequence on the Copper‐Binding Properties of Tripeptides and the Electrochemical Behaviour of Their Copper(II) Complexes
Author(s) -
Mena Silvia,
Mirats Andrea,
Caballero Ana B.,
Guirado Gonzalo,
Barrios Leoní A.,
Teat Simon J.,
RodriguezSantiago Luis,
Sodupe Mariona,
Gamez Patrick
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704623
Subject(s) - deprotonation , chemistry , copper , tripeptide , electrochemistry , amide , redox , crystallography , metal , coordination sphere , glassy carbon , ligand (biochemistry) , inorganic chemistry , peptide , stereochemistry , cyclic voltammetry , crystal structure , organic chemistry , electrode , ion , biochemistry , receptor
The binding and electrochemical properties of the complexes Cu II ‐HAH , Cu II ‐HWH , Cu II ‐Ac‐HWH , Cu II ‐HHW , and Cu II ‐WHH have been studied by using NMR and UV/Vis spectroscopies, CV, and density functional calculations. The results obtained highlight the importance of the peptidic sequence on the coordination properties and, consequently, on the redox properties of their Cu II complexes. For Cu II ‐HAH and Cu II ‐HWH , no cathodic processes are observed up to −1.2 V; that is, the complexes exhibit very high stability towards copper reduction. This behaviour is associated with the formation of very stable square‐planar (5,5,6)‐membered chelate rings (ATCUN motif), which enclose two deprotonated amides. In contrast, for non‐ATCUN Cu II ‐Ac‐HWH , Cu II ‐HHW complexes, simulations seem to indicate that only one deprotonated amide is enclosed in the coordination sphere. In these cases, the main electrochemical feature is a reductive irreversible one electron‐transfer process from Cu II to Cu I , accompanied with structural changes of the metal coordination sphere and reprotonation of the amide. Finally, for Cu II ‐WHH , two major species have been detected: one at low pH (<5), with no deprotonated amides, and another one at high pH (>10) with an ATCUN motif, both species coexisting at intermediate pH. The present study shows that the use of CV, using glassy carbon as a working electrode, is an ideal and rapid tool for the determination of the redox properties of Cu II metallopeptides.