Majima E, Goto S, Hori H, Shinohara Y, Hong Y M, Terada H
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
Biochim Biophys Acta. 1995 Apr 13;1243(3):336-42. doi: 10.1016/0304-4165(94)00159-u.
The stabilities of the SH-reagent eosin-5-maleimide (EMA) and its adducts with the SH-compounds L-cysteine, N-acetyl-L-cysteine and glutathione (reduced form) were studied under various conditions in comparison with those of the adducts of N-ethylmaleimide (NEM). Studies by reversed-phase high performance liquid chromatography and mass spectrometry showed that EMA was less stable than NEM at neutral and moderately alkaline pH values. EMA formed a succinimide-type adduct with SH-compounds, and then underwent further modification by nucleophilic attack of OH- or an amino group. The succinimide-type adducts with acetylcysteine and glutathione were converted to open-type adducts, in which the succinimide ring was cleaved, whereas the adduct with cysteine was modified to a thiazine-type adduct. Kinetic analyses showed that these open-type and thiazine-type adducts were readily formed and were stable at moderately alkaline pH values such as pH 8.0 or 9.0.
在各种条件下，研究了巯基试剂 eosin-5-马来酰亚胺（EMA）及其与巯基化合物 L-半胱氨酸、N-乙酰-L-半胱氨酸和谷胱甘肽（还原型）的加合物的稳定性，并与 N-乙基马来酰亚胺（NEM）的加合物进行了比较。反相高效液相色谱和质谱研究表明，在中性和适度碱性 pH 值下，EMA 比 NEM 稳定性差。EMA 与巯基化合物形成琥珀酰亚胺型加合物，然后通过 OH-或氨基的亲核攻击进行进一步修饰。与乙酰半胱氨酸和谷胱甘肽的琥珀酰亚胺型加合物转化为开环型加合物，其中琥珀酰亚胺环被裂解，而与半胱氨酸的加合物则被修饰为噻嗪型加合物。动力学分析表明，这些开环型和噻嗪型加合物易于形成，并且在适度碱性 pH 值（如 pH 8.0 或 9.0）下稳定。
