Photooxidation Rose Bengal

Photooxidation Rose bengal (anionic) or methylene blue (cationic) as sensitizer... 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

The rate of phosphoprotein formation in the presence of 5 mM CaCl2 was only slightly affected by mild photooxidation in the presence of Rose Bengal, but the hydrolysis of phosphoenzyme intermediate was inhibited sufficiently to account for the inhibition of ATP hydrolysis [359]. The extent of inhibition was similar whether the turnover of E P was followed after chelation of Ca with EGTA, or after the addition of large excess of unlabeled ATP. These observations point to the participation of functionally important histidine residues in the hydrolysis of phosphoprotein intermediate [359]. 

Bilski P, Motten AG, Bilska M, Chignell CF (1993) The photooxidation of diethylhydroxylamine by rose bengal in micellar and nonmicellar aqueous solutions. Photochem Photobiol 58 11-18. 

Baeckstrom and coworkers utilized the enhanced selectivity of singlet oxygen towards different types of double bonds, as the key step for the synthesis of trani-Sabinene . By using the method of simultaneous oxidation and reduction (Rose Bengal sensitized photooxidation in the presence of tetrabutylammonium borohydride) they managed to isolate compound 166 by a total conversion of 164 (Scheme 61). Compound 165 remained... 

Risk labels, lATA/ICAO, 751-3 Risk phrases, 621, 748, 749 River water, peroxide determination, 642 RNA, ozone disinfection, 616 ROS see Reactive oxygen species Rose Bengal sensitized photooxidation, 890 Rotational barriers, regioselective allylic hydroperoxide formation, 836, 847-9 Rotational isomers, peroxynitrous add, 8-9 Rotational spectra, ozonides, 721, 722-3 RP-HPLC, hydrogen peroxide determination, 627... 

Rose Bengal mediated photooxidation <2> (<2> deoxyguanosine protects... 

Among the more interesting applications of polymer Rose Bengal is that of a sensitizer in studying the oxidation of other polymeric substrates [301]. Rose Bengal immobilized on Sepharose has been reported as a sensitizer for protein photooxidation [302], The oxygen uptake by the amino acids cysteine, hisitidine, methionine, tryptophan, and tyrosine was reported to be about 20% as much from the immobilized dye as from the free dye in aqueous solution. 

A number of workers have looked at the effect of photooxidation and photodynamic sensitizers on DNA. Rose Bengal photosensitizes strand breaks in double-stranded, supercoiled, pBR322 DNA the effect follows first-order kinetics with respect to light fluence and dye concentration. The reaction is substantially more efficient in the absence of oxygen, but the quantum yield of strand breaks in air is only 10 8. The results are consistent with the initiation of chain scission by Rose Bengal triplet, with some additional mechanism coming into play in the presence of oxygen. 

Substituent effects in the dye-sensitized (Rose Bengal or methylene blue) singlet oxygen photooxidation of a wide variety of furans have been investigated.287 Solvents effects on the value of p, which became less negative as polarity of the medium was increased was indicative of... 

Inactivated by photooxidation in the presence of methylene blue (60), riboflavine (60), or Rose Bengal (61). Together with the inactivation the concomitant loss of histidine residues is observed. One (probably His 92) or more histidine residues might participate in the enzyme activity. 

Photooxidation of alkaline phosphatase in the presence of methylene blue and Rose Bengal causes loss of activity for both native and apo-enzyme. In the case of the native enzyme, zinc protects 2 to 3 of the 16 histidine residues. The rate of oxidation of tryptophan is not affected by zinc, and there was no loss of tyrosine. Also, photooxidation of the apoenzyme diminishes zinc binding. It would appear that histidine residues play a role in binding the two zinc ions necessary for enzymic activity (91). 

Figure 2. Quantum yields of the Rose Bengal sensitized photooxidation of Q shown in a plot derived from Equation 39.

The results of several control experiments made it clear that polymer rose bengal was an authentic singlet oxygen sensitizer.1 Photooxidation of typical singlet oxygen acceptors in non-polar... 

Both curves have similar shapes and it is clear that the photooxidation process is controlled by the diffusion of oxygen into the rose bengal sites in the polymer solution. These results suggest that when a snail amount of rose bengal is attached to the polymeric backbone (P-RB-51, 102 152 305) the quantum yield of of singlet oxygen formation is essentially the same (about 0.38). 

Photooxidation of alcohols to ketones in high yields is performed at room temperature with oxygen in the presence of at least 1 mol of a base (Na, NaH, NaOH, KOH, or terr-BuOK) under irradiation with rose bengal as a sensitizer [45]. 

Lead dioxide will oxidise 4,4 -(trimethylene)bis(2,6-di-t-butylphenol) leading to formation of a dispiro-compound by intramolecular cyclisation at the 4,4 -positions, and irradiation of this compound in a methylcyclohexane matrix at — 150°C gives 4,4 -(trimethylene)bis(2,6-di-t-butylphenoxy) diradical as a stable triplet species. Rose Bengal photooxidation of 2,3-dihydroxy-naphthalene and 2,7-dihydroxynaphthalene in basic aqueous solution gives the l,r-dimeric products by coupling of the radicals formed by electron transfer either to the excited sensitizer or to 02( Ag). ° The dimer which originates from 2,7-dihydroxynaphthalene is subject to further oxidation to 6,7-dihydroxyperylene-l,12-quinone. Irradiation of the dimethoxyphenol (82) under constant current electrolysis leads via (83) to formation of the substituted tricyclo[5.4.0.0 ]undec-8-ene (84) which can be converted into ( )-isoitalicene (85 R = Me, R = H). ... 

In the presence of Rose Bengal as sensitizer and under either aerobic or anaerobic conditions, proline is photodecarboxylated to A -pyrroline, and under similar conditions the methyl ester yields an equimolar mixture of A -and A -pyrroline-2-carboxylic acid methyl esters. These observations suggest that the reaction proceeds by a Type I photooxidation. 

The photooxidation of oxopurines such as caffeine, theophylline, theobromine, and 1,3,7-trimethyluric acid using Rose Bengal as sensitizer occurs by a type II mechanism. 3-Methyl-5-(methylamine)-l,5-dehydrohydantoin has been characterised as a reaction product, and evidence is presented which suggests that the initial exciplex formed between 02( Ag) and the oxopurine evolves into a zwitterionic transition state. 

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