title: Methylation mechanism of tin(II) by methylcobalamin in aquatic systems.
abstract: 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).
authors.affiliation: 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.
authors.forename: Baowei
authors.initials: B
authors.lastname: Chen
authors.forename: Qunfang
authors.initials: Q
authors.lastname: Zhou
authors.forename: Jiyan
authors.initials: J
authors.lastname: Liu
authors.forename: Dandan
authors.initials: D
authors.lastname: Cao
authors.forename: Thanh
authors.initials: T
authors.lastname: Wang
authors.forename: Guibin
authors.initials: G
authors.lastname: Jiang
mesh_terms: 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*
chemical_list: D014867:Water; D012965:Sodium Chloride; D014001:Tin; C019476:mecobalamin; D014805:Vitamin B 12