通过电子光谱法、电子自旋共振光谱法和电位滴定法对金属博来霉素进行的研究。

Studies of metallobleomycins by electronic spectroscopy, electron spin resonance spectroscopy, and potentiometric titration.

作者信息

Sugiura Y, Ishizu K, Miyoshi K

出版信息

J Antibiot (Tokyo). 1979 May;32(5):453-61. doi: 10.7164/antibiotics.32.453.

DOI:10.7164/antibiotics.32.453

Abstract

The 1:1 bleomycin-A2-Cu(II) complex shows an absorption maximum at 595 nm (epsilon 120), circular dichroism extrema at 555 nm (delta epsilon + 1.21) and 665 nm (-0.61), and electron spin resonance (ESR) signal with g = 2.211, g = 2.055, and A = 178 x 10(-4) cm-1. The formation constant (log K = 12.630) and deprotonation constant (PKc = 3.585) of the 1:1 bleomycin-Cu(II) complex were determined by computer analysis of potentiometric data. The results of potentiometric titration also indicate that the stability of bleomycin-metal complexes is in the order Fe(II) less than Co(II) less than Ni(II) less than Cu(II) greater than Zn(II) and that these divalent metal complexes have a similar coordination environment. The bleomycin-Cu(II) complex has substantially a square-pyramidal configuration in which the secondary amine nitrogen, pyrimidine(N-1) ring nitrogen, deprotonated peptide nitrogen of histidine residue, and histidine imidazole(N-1) nitrogen coordinate to Cu(II) as planar ligand donors, and the alpha-amino nitrogen as axial donor. The specific Cu(II)-binding site of bleomycin has been compared with that of human serum albumin.

摘要

博来霉素 - A2 - Cu(II) 1:1复合物在595 nm处有最大吸收峰（ε为120），在555 nm（Δε为 + 1.21）和665 nm（ - 0.61）处有圆二色性极值，并且具有g = 2.211、g = 2.055和A = 178×10⁻⁴ cm⁻¹的电子自旋共振（ESR）信号。通过对电位滴定数据进行计算机分析，确定了博来霉素 - Cu(II) 1:1复合物的形成常数（log K = 12.630）和去质子化常数（PKc = 3.585）。电位滴定结果还表明，博来霉素 - 金属复合物的稳定性顺序为Fe(II) ＜ Co(II) ＜ Ni(II) ＜ Cu(II) ＞ Zn(II)，并且这些二价金属复合物具有相似的配位环境。博来霉素 - Cu(II)复合物基本上具有四方锥构型，其中仲胺氮、嘧啶（N - 1）环氮、组氨酸残基的去质子化肽氮以及组氨酸咪唑（N - 1）氮作为平面配体供体与Cu(II)配位，而α - 氨基氮作为轴向供体。已将博来霉素特定的Cu(II)结合位点与人血清白蛋白的进行了比较。