Methanethiosulfonates

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... 

Stauffer, D.A., and Karlin, A. (1994) Electrostatic potential of the acetylcholine binding sites in the nicotinic receptor probed by reaction of binding-site cysteines with charged methanethiosulfonates. Biochemistry 33, 6840-6849. 

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. 

Kamdar, G., Penado, K. M., Rudnick, G., and Stephan, M. M. (2001) Functional role of critical stripe residues in transmembrane span 7 of the serotonin transporter. Effects of Na+, Li+, and methanethiosulfonate reagents. J. Biol. Chem. 276,4038 1045. 

The most important flavour compound in raw onions is thiopropanal-S-ox-ide, the lachrymatory factor [145,146]. Other important flavour compounds are 3,4-dimethyl-2,5-dioxo-2,5-dihydrothiophene and alkyl alkane thiosulfonates such as propyl methanethiosulfonate and propyl propanethiosulfonate with a distinct odour of freshly cut onions [35, 36, 147]. Various thiosulfinates that have a sharp and pungent odour may also contribute to the flavour of onions. These compounds, however, are rapidly decomposed to a mixture of alkyl and alkenyl monosulfides, disulfides and trisulfides (Scheme 7.3) of which dipropyl disulfide, methyl ( )-propenyl disulfide, propyl ( )-propenyl disulfide, dipropyl trisulfide and methyl propyl trisulfide are the most important contributors to the aroma of raw and cooked onions (Table 7.5, Fig. 7.6) [148-150]. Recently, 3-mercapto-2-methylpentan-l-ol was identified in raw and cooked onions eliciting intense meat broth, sweaty, onion and leek-like odours [142, 151]. 

Hydrogel formation from four-arm polyethylene glycol methanethiosulfonate... 

Fig. 24. Methanethiosulfonate (MTS) reagent reacting with a thiol (sulfhy-dryl), typically of a cysteine residue in a protein, forming a disulfide bond and thus introducing the dye moiety (label)—SR.

Thiols can be linked to insoluble supports as disulfides by disulfide interchange. Mixed disulfides can be prepared on insoluble supports by treating support-bound thiols with excess activated disulfide (e.g. 2-benzothiazolyl, 2-nitrophenyl, 3-nitro-2-pyridyl disulfides [60,676] or a methanethiosulfonate MeS02-SR [677] Figure 3.33), or by treating a support-bound disulfide (e.g. a 2-pyridyl disulfide [191]) with a thiol. Resin-bound disulfides are stable under the conditions of standard Fmoc peptide synthesis, but can be cleaved by reducing agents (Entries 8 and 9, Table 3.37 [191,676,678-681]). 

Bloxham, D. P., and Sharma, R. P. (1979) The development of S,S -poIymethylenebis-(methanethiosulfonates) as reversible cross-linking reagent for thiol groups and their use to form stable catalyticaUy active cross-linked dimers with glyceraldehyde-3-phosphate dehydrogenase. Biochem. J. 181, 355. 

Hydroxypropyl methanethiosulfonate. Organo-sulfur group. Good bacterial slime controller for cooling systems with pH below 7.5. Limited value as algaecide or fungicide and at alkaline pH. Typical product is 11 to 12% active, with dose rate of 20 to 100 ppm based on volume. 

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