Does s-methyl methanethiosulfonate trap the thiol-disulfide state of proteins?

S-Methyl methanethiosulfonate (MMTS) is a reagent used to trap the natural thiol-disulfide state of the proteins. The efficiency of trapping mixed disulfides in vivo has been found to be higher for MMTS than for the more commonly used N-ethylmaleimide. MMTS has also been used for studying protein S-nitrosylation and the role of catalytic and structural cysteines on enzyme activities. However, the treatment of a protein with MMTS can potentially generate additional protein disulfide bonds. These results indicate that in vitro MMTS is able to form both intramolecular and intermolecular protein disulfide bonds in addition to dithiomethane adducts.