Copper(II), Nickel(II) and Zinc(II) Complexes of Peptide Fragments of Tau Protein

• Published in: Molecules (Basel, Switzerland) Vol. 29; no. 10; p. 2171
• Main Authors: Kastal, Zsuzsa, Balabán, Adrienn, Vida, Szilvia, Kállay, Csilla, Nagy, Lajos, Várnagy, Katalin, Sóvágó, Imre
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 07.05.2024
• Subjects: Binding sites; Coordination Complexes - chemistry; Copper; Copper - chemistry; copper(II) catalyzed oxidation; copper(II) complex; Histidine - chemistry; histidine-containing fragments; Hydrogen Peroxide - chemistry; Hydrogen-Ion Concentration; Nickel - chemistry; nickel(II) complex; Oxidation; Oxidation-Reduction; Peptide Fragments - chemistry; Peptides; Proteins; tau protein; tau Proteins - chemistry; Thermodynamics; Zinc; Zinc - chemistry; zinc(II) complex; zinc(II) complex; nickel(II) complex; UV-Vis spectroscopy; histidine-containing fragments; copper(II) catalyzed oxidation; potentiometry; copper(II) complex; tau protein; CD spectroscopy
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules29102171

Copper(II), nickel(II) and zinc(II) complexes of various peptide fragments of tau protein were studied by potentiometric and spectroscopic techniques. All peptides contained one histidyl residue and represented the sequences of tau(91-97) (Ac-AQPHTEI-NH ), tau(385-390) (Ac-KTDHGA-NH ) and tau(404-409) (Ac-SPRHLS-NH ). Imidazole-N donors of histidine were the primary metal binding sites for all peptides and all metal ions, but in the case of copper(II) and nickel(II), the deprotonated amide groups were also involved in metal binding by increasing pH. The most stable complexes were formed with copper(II) ions, but the presence of prolyl residues resulted in significant changes in the thermodynamic stability and speciation of the systems. It was also demonstrated that nickel(II) and especially zinc(II) complexes have relatively low thermodynamic stability with these peptides. The copper(II)-catalyzed oxidation of the peptides was also studied. In the presence of H O , the fragmentation of peptides was detected in all cases. In the simultaneous presence of H O and ascorbic acid, the fragmentation of the peptide is less preferred, and the formation of 2-oxo-histidine also occurs.