Methyl Methanethiosulfonate

Methyl methanethiosulfonate (MMTS) is a small reversible blocking agent for sulfhydryl groups (Thermo Fisher, Toronto Research). It reacts with free thiols to form a dithiomethane modification with release of sulfinic acid (Figure 1.122). The sulfinic acid component decomposes into volatile products, which don t affect the disulfide formed from the MMTS reaction Alkylthiosulfonates react rapidly with thiols under mild conditions at physiological pH. The MMTS compound is a liquid at 10.6 M concentration and is conveniently added to a reaction medium by pipette. Complete thiol modifications of available cysteine residues in proteins can... 

Roberts, D. D., Lewis, S. D Ballou, D. P., Olson, S. T and Shafer, J. A. (1986) Reactivity of small thiolate anions and cysteine-25 in papain toward methyl methanethiosulfonate. Biochemistry 25, 5595-5601. 

Methyl methanethiosulfonate, 5, 454-455 7, 243-244. Supplier Aldrich. The reagent can be prepared in 70-80% yield by reaction of excess DMSO with chlorotrimethylsilane and then with ethylene glycol (cf. 9, 190). ... 

Cysteine lodoacetamide, iodoacetate p -Hydro gmaercuribenzoate Methyl methanethiosulfonate Ellman s reagent (DTNB) N-Ethylmaleimide lodoacetamide has the potential to modify histidines and lysines... 

REDUCTION OF SULFONYL HALIDES WITH ZINC POWDER S-METHYL METHANETHIOSULFONATE (Methanesulfonothioic acid, S-methyl ester)... 

S-Methyl methanethiosulfonate is commercially available, but is expensive. Other preparation methods involve oxidation of thiols or disulfides by halogens or peroxides,3 reduction of sulfinyl halides5 (which have to be prepared) or sulfonyl halides with potassium iodide6 or copper/bronze7 as well as thermolysis of sulfonylhydrazines.8 Finally, a two-day procedure for the preparation of methyl methanethiosulfonate has been reported from dimethyl sulfoxide.9... 

REDUCTION OF SULFONYL HALIDES WITH ZINC POWDER S-METHYL METHANETHIOSULFONATE. 

A variety of (dithioperoxo)thioic acid esters 220 were synthesized in moderate to good yields by reacting dithioate magnesium halides 221 with S-alkyl p-toluenethiosulfonates 222 or S-methyl methanethiosulfonates (223) (Scheme 43) [136,137]. Oxidation of 220 with m-CPBA gave the sulfines 224 as an E-Zgeometrical mixture [136]. These sulfines isomerized to acyl trisulfides (R C(O)-S3R ) after 10 days at room temperature. 

To date, the most commonly used spin labels for membrane proteins are pyrroline-type nitroxide radicals. Several labeling strategies and spin labels are available at present. However, the extreme specificity for the free thiol of cysteines, a stoichiometric reaction at most sites, and the relatively small size and flexibility of the modified side chain make the (l-oxyl-2,2,5,5-tetramethyl-A3-p3Troline-3-methyl) methanethiosulfonate spin label (MTSSL) the most popular choice for SDSL applications. 3 -(2-lodoacetamido)-2,2,5,5-tetramethyl-1 -pyrrolidinyloxy radical labels (lAP) are also used in combination with cysteines. The advantage of LAP vs MTSSL is that the covalent bond with the cysteine is irreversibly formed and this may be more suitable for particular situations in which the MTSSL tends to be released from the labeled sites. 

HYDROXY-a,d-UNSATURATF.D ESTERS Methyl methanethiosulfonate. IMINOAZIRIDINES Copperfll) trrfluoromethanesulfonate. 

Methyl methanethiosulfonate, CH3SO2SCH3 (1), 5, 454-455. Mol. wt. 126.20, b.p. 96 91°IA.5 mm. The reagent can also be obtained by reaction of methyl-siilfenyl chloride, CH3SCI, with water. ... 

Methyl methanethiosulfonate was negative in chromosomal aberration assays conducted in Saccharomyces cerevisiae strain D7 or S. cerevisiae haploid strain N123 at concentrations of up to 300 pg/ml (Dorange et al., 1983). 

A combination of circular dichroism, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chemical crosslinking, and analytical ultracentrifugation studies showed that both the apo- and metallated derivatives of H21(31-mer) form two-stranded a-helical coiled coils in aqueous solution. Further characterization of these derivatives by EPR spin-label experiments helped to determine its three-dimensional backbone structure. In these studies, a Cys-21 mutant of the 31-mer coiled coil, H21/C21(31-mer), was prepared and labeled with a thiol-specific nltroxide spin label (MTSL = l-oxyl-2,2,5,5-tetramethyl-A -pyrroline-3-methyl-methanethiosulfonate) at position 21 of the peptide sequence which is the site of metal substitution in the ET heterodimer. Comparison of the low-temperature, dipolar-broadened spectrum of the spin-labeled dimer with those of magnetically dilute peptide samples yielded a backbone-to-backbone distance that was nearly identical to that of the GCN4 homodimer. Based on these results, computer modeling studies provided an estimate of the metal-to-metal distance in the ET heterodimer of m-m > 25 A. The electron-transfo properties of this system are now being studied by a combination of laser flash-quench and pulse radiolysis techniques. 

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