Sequestration of Hg2+ by Some Biologically Important Thiols

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• 作者：Paola Cardiano ; Gabriella Falcone ; Claudia Foti ; Silvio Sammartano
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2011
• 出版时间：December 8, 2011
• 年：2011
• 卷：56
• 期：12
• 页码：4741-4750
• 全文大小：960K
• 年卷期：v.56,no.12(December 8, 2011)
• ISSN：1520-5134

文摘

A potentiometric and ¹H NMR investigation on the interactions between Hg²⁺ and some biologically important sulfhydryl ligands, such as cysteine (H₂CYS), penicillamine (H₂PSH), and glutathione (H₃GSH), is reported. Equilibria were studied at T = 298.15 K, in the ionic strength range (0.1 to 1) mol路kg^鈥?, using as ionic medium NaCl in the presence of iodide (NaI) as a competitive ligand. Results show the formation of HgL^2鈥?i>z, HgLH^3鈥?i>z, HgLH₂^4鈥?i>z, HgL₂^2鈥?z, HgL₂H^3鈥?z, and HgL₂H₂^4鈥?z species (L^{z鈥?/sup> = CYS2鈥?/sup>, PSH2鈥?/sup>, or GSH3鈥?/sup>) together with HgL₂H₃鈥?/sup> for GSH3鈥?/sup> only. Formation constant values are very high with, as an example, log 尾 = 34.54, 34.24, and 32.05 for Hg(CYS)0, Hg(PSH)0, and Hg(GSH)鈭?/sup> species, respectively (at I = 0.25 mol路kg鈥?, T = 298.15 K). 1H NMR measurements at I = 0.25 mol路kg鈥? (NaCl) fully confirm the potentiometric findings. The speciation diagrams show that most of the metal fraction is present as complex species in a wide pH range, and the hydrolysis of the cation is completely suppressed. The sequestering ability of ligands toward Hg2+ is very high, and it was analyzed and compared at different pH and ionic strengths.}