Methylation mechanism of tin(II) by methylcobalamin in aquatic systems.
The methylation reaction of tin(II) with methylcobalamin (CH(3)B(12)) in aquatic systems was modeled in the laboratory. The products were detected by a sensitive gas chromatography-flame photometric detector (GC-FPD), and further identified by gas chromatography-mass spectrometry (GC-MS). Both monomethyltin (MMT) and dimethyltin (DMT) were found as methylation products. Three important effecting factors during the methylation reaction, salinity, pH and aerobic or anaerobic, were studied. The results showed that methyl group can be transferred from CH(3)B(12) to tin in aquatic solutions as a radical or carbonium, as well as a carbanion. Two explanations for the pH-dependency of the methylation reaction between tin(II) and CH(3)B(12) were proposed: pH-dependency of the equilibrium states of CH(3)B(12), and pH-dependency of inorganic tin(II) species whose reactivity vary with the redox potential in the solution. Salinity can influence the activity of the methyl donor, which cause changes in the methylation efficiency. Kinetic experiments showed that the methylation reaction was pseudo-first-order for CH(3)B(12).
Chen
Baowei
B
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, PR China.
Zhou
Qunfang
Q
Liu
Jiyan
J
Cao
Dandan
D
Wang
Thanh
T
Jiang
Guibin
G
D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012965:Sodium Chloride / Q000737:chemistry; D014001:Tin / Q000737:chemistry*; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D014867:Water; D012965:Sodium Chloride; D014001:Tin; C019476:mecobalamin; D014805:Vitamin B 12