Protonation equilibria and solubility of l-cystine.
Protonation equilibria and solubility of l-cystine.
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L-胱氨酸的质子化平衡和溶解度。
DOI：
10.1016/s0039-9140(01)00570-7
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
M. R. Festa
中科院分区：
文献类型：
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作者：
F. Apruzzese;E. Bottari;M. R. Festa
L-胱氨酸是天然存在的氨基酸中最不可溶的。其溶解度是氢离子浓度的函数，取决于其质子化。本文研究了25°C下，不同浓度（3.00，2.00，1.00，0.500，0.150 mol dm−3）的L-胱氨酸在NaCl恒定离子介质中的性质。在这样的实验条件下，溶解度及其作为氢离子浓度的函数的变化进行了测定。用玻璃电极原电池电动势法研究了胱氨酸在酸碱溶液中的质子化反应。四个质子化常数l-胱氨酸测定在所有选定的浓度的离子介质。在不同浓度的离子介质中，这些常数的不同值可以用活度系数的变化或L-胱氨酸与钠离子形成络合物来解释。不同浓度的NaCl溶液中溶解度的变化也被观察到。
l-Cystine is the natural least soluble of the naturally occurring amino acids. Its solubility is a function of the hydrogen ion concentration depending on its protonation. This paper presents an investigation on properties of l-cystine in a constant ionic medium of NaCl at different concentrations (3.00,2.00,1.00,0.500,0.150 mol dm−3) and at 25°C. In such experimental conditions, solubility and its changes as a function of hydrogen ion concentration were determined. Protonation of cystine was studied in acid and basic solution, by measuring the electromotive force of galvanic cell involving a glass electrode. Four protonation constants for l-cystine were determined in all the selected concentrations of ionic medium. The different values obtained for the constants in ionic medium of different concentration could be explained both with the variation of activity coefficients or with the complex formation between l-cystine and sodium ions. Variations of solubility for different concentration of NaCl were observed as well.