Dye-sensitized photooxidation

Acher, A. F. and Juven, B. I. (1977). Destruction of faecal coliforms in sewage water by dye-sensitized photooxidation. /. Appl. Environ. Microbiol. 33,1019-1023. 

It has recently been shown by Spikes150 that uracil and a number of substituted uracils are subject to dye-sensitized photooxidation under certain conditions. Methylene blue and Eosin Y were active photosensitizers in the pH range 8-11.5, but were inactive below pH 8. FMN was very active over the pH range of 2.4-11.5. Photooxidation was measured with a rotating platinum oxygen electrode. 

Dye-sensitized photooxidation of methionine occurs selectively in strong formic or acetic acid media (131). All four methionine residues in RNase-A appear to be converted to sulfoxides under these conditions. The product still showed 13% of the initial activity in the Kunitz RNA assay at pH 5 [see, however, Neumann et al. (ISO)]. Apparently an oxygen atom can be accommodated next to each Met sulfur atom in a structure closely resembling that of the native enzyme. The 3 buried tyrosine residues appeared to have been largely normalized. It would be interesting to know if the binding of inhibitors returned these to the buried condition. 

Photooxygenation of vinylsilane in the presence of acetic anhydride and pyridine furnishes a convenient procedure for the synthesis of a-trimethylsilylenones 185 in moderate to good yields (equation 156)278. Dye-sensitized photooxidations of allylsilane with singlet oxygen produces a mixture of (E)- and (Z)-3-trimethyl-silylallyl hydroperoxides 186 (equation 157)279. 

Dye-sensitized photooxidation (Ray 1967 Westhead 1972) has been employed successfully in a number of cases (e.g. Forman et al. 1973) to obtain selective destruction of histidyl residues. 

Acher, A. M. and I. Rosenthal. 1977. Dye-sensitized photooxidation—a new approach to the treatment of organic matter in sewage effluents. Water Res. 11, 557-562. 

Wasserman and Floyd ° first demonstrated the dye-sensitized photooxidation of oxazoles to prepare triamides 255 in 1966 (Fig. 3.75). This reaction has since become a valuable synthetic tool. Several reports have now appeared that establish the mechanism of this transformation to proceed through an initial [4-P 2]-cycloaddition to provide an unstable 2,5-endoperoxide, 252. Oxygen-18 studies were consistent with the formation of 252 and excluded the formation of an... 

Epoxldation. Dye-sensitized photooxidation of aliphatic olefins results in formation of altylic hydroperoxides from reaction with singlet oxygen. Photo-IMiidation with -diketone sensitizers follows a different course epoxides are the foain products. Of several a-diketones examined, epoxides are obtained in highest yields with biacetyl, which is oxidized at the same time mainly to acetic acid. In some cases yields of epoxides in biacetyl photooxidation are 90% or more. Both cis- and trans-alkenes yield mainly tran.r-epoxides. Both epoxidatioh and ketone destruction are much slower with benzil. The nature of this epoxidation reaction is discussed, although many points of ambiguity remain. This reaction is Of practical importance. ... 

The active site of Neurospora PPO is thought to contain two mols copper/mol active site (Solomon, 1981) Elucidation of the complete amino acid sequence of Neurospora PPO (Lerch, 1978), coupled with dye-sensitized photooxidation (Pfiffner and Lerch, 1981) and inhibition (Pfiffner et al , 1981) indicated that... 

In the diagram, R is a postulated bridging ligand. HiSj gg, His] 93 and His239 are destroyed by dye-sensitized photooxidation while His306 destroyed by inhibition. The other two ligands... 

Dye-sensitized photooxidation is a well-known method which has been used to modify certain amino acid residues in proteins. In this technique, a mixture of a dye and the protein under study is irradiated in the presence of oxygen at wavelengths at which only the dye can absorb light. In this way one can, under special conditions, accomplish very specific chemical modification of one or several amino acid residues in proteins. By using a ligand as the sensitizer, modification can be obtained preferentially at the ligand-binding site of the protein. ... 

For our pilot studies of the specificity of the dye-sensitized photooxidative coupling reaction we have, for several reasons, chosen the coupling of fluorescein to bovine serum albumin. The first advantage of this system is that the photochemistry of fluorescein - is well known. 

Eskins, K., C. Glass, W. Rohwedder, R. Kleiman, and J. Sloneker Dimers of Isoeugenol by Dye-Sensitized Photooxidation. Tetrahedron Lettet 1972, 861. 

Also obtained by dye-sensitized photooxidation of enolic tautomer of l-(3,4-dihydro-1 -hydroxy-2-naphthalenyl)-1 -propanone [ 134643-89-3] (19-24%) [7780]. 

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