Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary.
Department of Applied Chemistry, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary.
Molecules. 2024 May 7;29(10):2171. 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 HO, the fragmentation of peptides was detected in all cases. In the simultaneous presence of HO and ascorbic acid, the fragmentation of the peptide is less preferred, and the formation of 2-oxo-histidine also occurs.
采用电位法和光谱法研究了铜（II）、镍（II）和锌（II）与tau 蛋白各种肽段的配合物。所有肽段都含有一个组氨酸残基，代表 tau(91-97)（Ac-AQPHTEI-NH）、tau(385-390)（Ac-KTDHGA-NH）和 tau(404-409)（Ac-SPRHLS-NH）的序列。组氨酸的咪唑-N 供体是所有肽段和所有金属离子的主要金属结合位点，但对于铜（II）和镍（II），随着 pH 值的增加，去质子酰胺基团也参与了金属结合。与铜（II）离子形成最稳定的配合物，但脯氨酸残基的存在导致体系热力学稳定性和形态发生显著变化。还证明镍（II），尤其是锌（II）与这些肽的配合物具有相对较低的热力学稳定性。还研究了铜（II）催化的肽氧化。在 HO 的存在下，在所有情况下都检测到肽的片段化。在 HO 和抗坏血酸同时存在的情况下，肽的片段化不太可能发生，同时也会形成 2-氧代组氨酸。
