Tosyl Moiety Research Articles

2'-O-Tosyladenosine

In the title compound, 2'-O-tosyl(toluenesulfonyl)-adenosine, C 17 H 19 N 5 O 6 S, the adenine base is in the syn conformation with a glycosidic torsion angle of 62.7 (4)°. The ribose sugar adopts the envelope conformation ( 2 E). The tosyl moiety is nearly parallel to the base. Both Watson-Crick and Hoogsteen sites of the adenine bases are involved in intermolecular hydrogen bonds.

Greater guest binding ability of .BETA.-cyclodextrin having both a cap and floor.

β-Cyclodextrin having both 2-naphthalenesulfonyl and tosyl moieties as the cap and floor has a greater ability to bind guests than β-cyclodextrin which has a cap only.

Studies on the mechanism of phosphorylation and transport of β-galactosides by the lactose phosphotransferase system of Staphylococcus aureus kinetic investigations using tosyl galactosides as reversible dead-end inhibitors

Tosyl galactosides, previously shown to be potent reversible dead-end inhibitors of the membrane-bound Enzyme IIlac of the lactose phosphotransferase system of Staphylococcus aureus, were used for an investigation of the kinetic mechanism of the sugar phosphorylation/transport reaction catalyzed by this enzyme: phospho-Factor IIIlac&sugar Enzyme IIlac lead to Factor IIIlac&sugar phosphate. Inhibition of Enzyme IIlac was studied in three different systems. Washed membranes, and washed membranes in the presence of 0.1% Triton X-100 were used for phosphorylation experiments, and whole cells were used for transport studies. When washed membranes were used to supply Enzyme IIlac, inhibition of phosphorylation by tosyl galactoside was linear non-competitive against both the sugar and phospho-Factor IIIlac substrates, with an apparent Ki of about 0.5 mM. This Ki decreased with increasing Factor IIIlac concentration. In the presence of 0.1% Triton X-100, the phosphorylation reaction was stimulated; under these conditions the inhibition became strictly competitive against sugar, and completely uncompetitive against phospho-Factor IIIlac. Apparently washed membranes can catalyze phosphorylation both via a reaction sequence in which sugar binds first and via one in which phospho-Factor IIIlac binds first, but in the presence of 0.1% Triton the reaction does not occur by the former sequence. The inability of bound phospho-Factor IIIlac to hinder the binding of tosyl galactosides suggests that the initial binding sites of the two substrates of Enzyme IIlac are separated by at least the distance of the tosyl moiety. Radioactive methyl 6-O-(p-toluenesulfonyl) beta-galactoside was not converted into a phosphorylated product in the reaction mixtures, i.e. it is a true dead-end inhibitor. Inhibition of beta-galactoside transport into whole cells by tosyl galactosides was competitive, with an apparent Ki of 5-10 mM, an order of magnitude higher than the Ki for inhibition of phosphorylation by membrane preparations. This result suggest that a significant level of unphosphorylated phospho-Factor IIIlac is present inside the cells, or that cellular levels of this compound are considerably lower than those used for in vitro sugar phosphorylation assays. Radioactive tosyl galactoside inhibitor was not transported into whole cells.

Folded conformations. Part VI. An NMR spectroscopic study of the preferred solution conformation of N,N′‐[bis(α‐tosylbenzyl)]urea

AbstractComparison of NMR spectral data of a number of N‐tosylalkyl‐ and N,N′‐bis(tosylalkyl)ureas reveals that the methyl protons of the tosyl moiety and the α‐sulfonyl alkyl proton in the N,N′‐[bis(α‐tosylbenzyl)]ureas 1‐3 resonate at unusually high fields. The presence of both sulfonyl groups and the aromatic rings of the benzyl moieties are prerequisites for the observation of appreciable upfield shifts. Evidence is presented that intramolecular shielding phenomena are involved. It is proposed that 1‐3 in solution predominantly adopt conformations in which each tosyl methyl group is positioned in the shielding region of the phenyl ring of the most remote benzyl group.