Journal Article

pH-Dependent Effects of L-Cysteine on Mercury Dissolution of α-HgS and β-HgS

Bi, Hongtao, Li, Cen, Du, Yuzhi, Zhang, Ming, Wei, Lixin

2018

Overview

Mercury sulfide is an insoluble inorganic mercury compound, and it is the main chemical form in traditional oral mercury-containing medicines. Hg2+ has a high affinity for thiols, and small molecule thiols in the gastrointestinal tract may promote mercury dissolution of mercury sulfide by binding to Hg2+. L-cysteine is the only amino acid that possesses a reducing sulfhydryl group (-SH), out of the 20 amino acids. This study investigates the effect of L-cysteine on mercury dissolution of mercury sulfide at pHs ranging from 1.2 to 7.2. The results showed that L-cysteine had different pH-dependent effects on the mercury dissolution of α-HgS and β-HgS. For α-HgS, the dissolved mercury concentration increased from 5.47 ± 0.97 ng/mL to 12.49 ± 0.54 ng/mL when the pH rose from 1.2 to 4.2, and decreased to 3.37 ± 0.70 ng/mL at pH 6.0 and then increased to 9.36 ± 0.79 ng/mL at pH 7.2. For β-HgS, the dissolved mercury concentration increased from 151.09 ± 2.25 ng/mL to 2346.71 ± 62.62 ng/mL when the pH increased from 1.2 to 7.2. In conclusion, L-Cys was distinctly enhanced upon mercury dissolution of α-HgS and β-HgS with increasing pH. These results may contribute to our understanding of the mercury absorption mechanism of traditional oral mercury-containing medicines.

• Publisher: Springer Nature B.V
• Subject: Amino acids / Cysteine / Dissolution / Dissolving / Gastrointestinal tract / Mercury / Mercury (metal) / Mercury compounds / pH effects / Sulfides / Sulphides / Thiols