Sulfation species defect

Studies on the metabolic fate of phenol in several species have indicated that four urinary products are excreted (Figure 9.5). Although extensive phenol metabolism takes place in most species, the relative proportions of each metabolite produced varies from species to species. In contrast to the cat, which selectively forms sulfate conjugates, the pig excretes phenol exclusively as the glucuronide. This defect in sulfate conjugation in the pig is restricted to only a few substrates, however, and may be due to the lack of a specific phenyl sulfotransferase because the formation of substantial amounts of the sulfate conjugate of 1-naphthol clearly indicates the occurrence of other forms of sulfotransferases. 

Experiments generating sulfate radicals, SO/", by UV photolysis of S2O82 in aqueous suspensions of silica nanoparticles showed a fast disappearance of the aqueous sulfate radicals yielding two transient species with absorption maxima around 320 and 600 nm, respectively [20]. The results indicated that at pH 3-9 S04 radicals build up an adduct on the surface with maximum absorption at 320 nm. This adduct shows similar reactivity to that observed for the sulfate radical in aqueous solution. The transients with absorption maximum at 600 nm were identified as SiO surface defects formed from the reaction between the adduct and deprotonated geminal and single silanols. Other less oxidative radicals lead to different radical-silica interactions. For example, thiocyanate radicals react with deprotonated silanols, not involving silanol oxidation. 

The 2-OST null mutant has been described in C. elegans as well. Surprisingly, 2-OST-deficient mutants are viable and fertile without any locomotory defect or embryonic paralysis as observed in perlecan-deficient worms. The phenotypes of 2-OST null worms are only detectable in nervous system development by displaying axonal guidance and migration defects in a neuron-type specific manner. These findings suggest that the 2-0-sulfation of HS plays very specific roles in metazoan development. These roles may vary in the developmental schemes of different species. 

At 27°C some sulfide ions are oxidized to sulfite and no hint of sulfate was observed. In contrast, at 77°C all sulfides are oxidized after ca. 100 s to sulfite and subsequently to sulfate. After 600 s, sulfate is the dominant species on the surface. Measurements at different temperatures allowed the determination of the activation energy for this oxidation. It was found that this energy on the stepped Pt(335) surface is less than half that on a flat Pt(l 11) surface, which indicates that sulfur oxidation occurs mainly at steps or other defects of the surface. Such investigations are important for a mechanistic understanding of the catalytic process. 

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