The N- and C-terminal blocked hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide (LAHYNK) representing the 80-85 fragment of histone H2B was synthesized and its interactions with Cu(II) and Ni(II) ions were studied by potentiometric, UV-Vis, CD, EPR, and NMR spectroscopic techniques in solution. Our data reveal that the imidazole N(3) nitrogen atom is the primary ligating group for both metal ions. Sequential amide groups deprotonation and subsequent coordination to metal ions indicated an {N(imidazole), 3N(amide)} coordination mode above pH approximately 9, in all cases. In the case of Cu(II)-peptide system, the almost exclusive formation of the predominant species CuL in neutral media accounting for almost 98% of the total metal ion concentration at pH 7.3 strongly indicates that at physiological pH values the sequence -LAHYNK- of histone H2B provides very efficient binding sites for metal ions. The imidazole pyrrole N(1) ionization (but not coordination) was also detected in species CuH(-4)L present in solution above pH approximately 11.

中文翻译：

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Cu(II) 和 Ni(II) 与组蛋白 H2B (80-85) 的末端封闭六肽 Ac-Leu-Ala-His-Tyr-Asn-Lys-酰胺模型相互作用。

合成了代表组蛋白 H2B 80-85 片段的 N 端和 C 端封闭的六肽 Ac-Leu-Ala-His-Tyr-Asn-Lys-amide (LAHYNK) 及其与 Cu(II) 和 Ni(II) 的相互作用) 离子通过电位、UV-Vis、CD、EPR 和 NMR 光谱技术在溶液中进行研究。我们的数据显示咪唑 N(3) 氮原子是这两种金属离子的主要结扎组。在所有情况下，连续的酰胺基团去质子化和随后与金属离子的配位表明 {N(咪唑), 3N(酰胺)} 配位模式高于 pH 值约 9。在 Cu(II)-肽系统的情况下，主要物种 CuL 在中性介质中几乎排他性地形成，占 pH 7 时总金属离子浓度的近 98%。图 3 强烈表明，在生理 pH 值下，组蛋白 H2B 的序列 -LAHYNK- 为金属离子提供了非常有效的结合位点。咪唑吡咯 N(1) 电离（但不是协调）也在 pH 值高于 11 的溶液中存在的物种 CuH(-4)L 中检测到。