The role of methylation in the copper(II) coordination properties of a His-containing decapeptide


Cite this: DOI: 10.1039/c8dt05037f Received 21st December 2018, Accepted 24th December 2018 DOI: 10.1039/c8dt05037f The role of methylation in the copper(II) coordination properties of a His-containing decapeptide† Alexandre Hautier,a Tiago Carvalho, a Daniela Valensin, b A. Jalila Simaan,a Bruno Faure, a Pedro Mateus, c Rita Delgado c and Olga Iranzo *a N-Methylation of the peptide amide bond has proven to be a powerful strategy to fine-tune the confor- mation and properties of peptides. In this context and for the first time, we show that N-methylation can also be used to control the copper(II) coordination properties of peptides and stabilize at high pH values the copper(II) species lacking amidate coordination. Namely, we have prepared a derivative of the O-Asp peptide where the copper(II) coordinating amino acids, i.e. Asp and His residues, were N-methylated (ONMe-Asp). A combined study using potentiometric and spectroscopic (UV-Vis, CD, EPR and NMR) tech- niques indicates the formation of the wanted major species, [CuH(ONMe-Asp)]2+, where copper(II)is bound to His4(Nε), His7(Nε), His9(Nε) and Asp2(COO−). With respect to the parent non-methylated O-Asp peptide, [CuH(ONMe-Asp)]2+ is stable at higher pH values but has lower affinity for copper(II). Additionally, electrochemical studies reveal a Cu(II) ⇌ Cu(I) redox process with a larger cathodic and anodic peak separ- ation. Species containing copper(II) coordinating amidates were not observed for this ONMe-Asp peptide.


Alexandre Hautier, Tiago Carvalho, Daniela Valensin, A. Jalila Simaan, Bruno Faure, Pedro Mateus, Rita Delgado, Olga Iranzo

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