Directed coordination study of [Pd(en)(H2O)2]2+ with hetero-tripeptides containing C-terminus methyl esters employing NMR spectroscopy

Post- print / Lokaútgáfa höfundarAlkylation of the C-terminus acids in small peptides allows direction to amine and amide coordination, while changing the peptide composition to form tetradentate κ4[n,5,5], where n = 5-, 6-, 7-, or 8-membered ring coordination geometries, can be achieved. The alkylated tripeptide ligands, TrpAlaGly(OMe), β-Asp(OtBu)AlaGly(OMe), Asp(OtBu)AlaGly(OMe), and the fully methylated GSH, γ-Glu(OMe)Cys(SMe)Gly(OMe), were synthesized and their coordination properties to [Pd(en)(H2O)2]2+ were studied. pH-dependent coordination was analyzed by NMR spectroscopy and the coordination to the alkylated tripeptides at selected pH values inferred from their NMR spectra. If selective coordination of amine/amide donors results in metal complexation, allowing for flexible and adjustable ligand frameworks, then this strategy could potentially be extended to other metal ions and peptide system.Financial support by The Icelandic Centre of Research (Rannis) grant nr 152323 is gratefully acknowledged. SGS and GRR thank COST Action CM1105 for STSM Grant and Prof. Etelka Farkas for hosting the STMS at the early stages of this project. Dr Sigridur Jonsdottir is thanked for assistance with the collection of mass spectrometry data.Peer reviewe