The Cu²⁺ Binding Properties of Branched Peptides Based on l-2,3-Diaminopropionic Acid

Abstract

Three new branched peptides, namely, H-Gly-Dap(H-Gly)-Gly-NH2 (3G), H-His-Dap(H-His)-Gly-NH2 (2HG), and H-Gly-Dap(H-Gly)-His-NH2 (2GH), where Dap stands for the 2,3-diaminopropionic acid residue, were synthesized by solid phase procedures. Because of the junction at Dap these peptides have three available pending arms for metal chelation. The complex formation between these peptides and 1 equiv of Cu(2+) was investigated as a function of pH by potentiometry ultraviolet-visible absorption, circular dichroism, and X-band electron paramagnetic resonance spectroscopy in aqueous medium. Our results clearly demonstrate that cooperation between all three peptide arms essentially contributes to the stability of copper(II) complexes.

Electrocatalytic water oxidation by CuII complexes with branched peptides

“…These peptides were reported to form stable 1 : 1 Cu II complexes that are distinguished by their ligand set and stability at basic pH resulting from the equatorially coordinated C-terminal His residue in 2GH. 15 According to potentiometry, the predominant form of the 1 : 1 Cu II complex above pH 7 (L = 3G) or above pH 8 (L = 2GH) is Cu II H À2 L (1 and 2, respectively) alike. Parallel X-Band EPR, UV/ VIS and CD spectroscopic changes with increasing pH suggested a {NH 2 ,2N À ,NH 2 } equatorial ligand set for 1.…”

“…The presence of 1-H + (e.g., Cu II -OH) is in line with potentiometry. 15,25 Cyclic voltammetry (CV) was performed on 1 and 2 in phosphate buffer (PB) at a glassy carbon working electrode (GCE). Upon increasing the pH to 11, a new electrocatalytic wave occurs (Fig.…”

Branched peptide with three histidines for the promotion of CuII binding in a wide pH range – complementary potentiometric, spectroscopic and electrochemical studies

“…1 2HG, 2GH). 10 Here we report a new branched tetrapeptide that is also built on Dap and contains one C-terminal and two N-terminal histidine residues (Fig. 1, 3H).…”

“…3,10 The improved targeting properties of this peptide family, compared to linear ones, was applied in gene transport processes, e.g., His-rich peptides. 11 The unique, three dimensional (3D) structure was also improved to be more effective in multiple antigen peptides (MAP), 12 in antibacterial 13 and in some therapeutic 14 agents.…”

“…6b). 10 Somewhat surprisingly 3H is by far the best Cu II complexing agent in the whole pH range, leaving behind both its N-(2HG) and C-terminal (2GH) domains (Fig. 1, S1b and d †).…”