Goren H J, Fridkin M
Int J Pept Protein Res. 1978 Jan;11(1):1-8. doi: 10.1111/j.1399-3011.1978.tb02814.x.
The thiolysis of Nim-2,4-dinitrophenyl-histidine peptides with 2-mercaptoethanol demonstrates an optimal rate between pH 8.5 and 9.0. Base lability of both reactants and product was investigated as a possible cause for the pH optimum. N-2,4-Dinitrophenylimidazole, a model for Nim-2,4-dinitrophenylhistidine peptides, 2-mercaptoethanol and the product of thiolysis, 2,4-dinitrophenyl-S-mercaptoethan-2-ol, were subjected to aqueous basic conditions (pH 8.5 to 12.0). The reactions were followed spectrophotometrically, and products were identified by comparison of their ultra-violet spectra with commercially available or synthetic compounds. Mechanisms and rate constants for base hydrolysis of 2,4-dinitrophenyl-thio ethers are presented. Although N-2,4-dinitrophenylimidazole and 2,4-dinitrophenyl-S-mercaptoethan-2-oldohydrolyze, it is the oxidation of 2-mercaptoethanol to 2-mercaptoethanol disulfide which results in the decreasing rate of thiolysis above pH 9.0.
用2-巯基乙醇对Nim-2,4-二硝基苯基-组氨酸肽进行硫解反应，结果表明在pH 8.5至9.0之间反应速率最佳。研究了反应物和产物的碱不稳定性，将其作为出现最佳pH值的可能原因。以N-2,4-二硝基苯基咪唑作为Nim-2,4-二硝基苯基组氨酸肽的模型，使其与2-巯基乙醇以及硫解反应产物2,4-二硝基苯基-S-巯基乙醇-2-醇在碱性水溶液条件下（pH 8.5至12.0）进行反应。采用分光光度法跟踪反应过程，并通过将产物的紫外光谱与市售或合成化合物的紫外光谱进行比较来鉴定产物。文中给出了2,4-二硝基苯基硫醚碱水解的反应机理和速率常数。尽管N-2,4-二硝基苯基咪唑和2,4-二硝基苯基-S-巯基乙醇-2-醇会发生水解，但在pH 9.0以上硫解反应速率下降是由于2-巯基乙醇氧化为二硫化2-巯基乙醇所致。
