Photosensitizer action

The isomerization of all-trans-[3-carotene under N2 atmosphere by photosensitization action of eight chlorophyll compounds naturally present in the extracts of green vegetables was investigated by illumination with fluorescent white light (3000 lux) at 12°C to minimize the thermal degradation (O Neil and Schwartz 1995). All chlorophylls showed similar isomeric distribution and efficiency, 9-d.s- 3-carotene is the main isomer formed. On the other hand, the illumination of all-fran.s-(3-car-otene without chlorophylls indicated that the main isomer formed was 13-d.s- 3-carotcnc, probably due to the population of a different triplet state manifold by direct photolysis. 

Indirect photolysis mechanisms involve the excitation of an additional compound called a photosensitizer (PS), which in its excited state can directly oxidize the pollutant of interest. This type of mechanism was investigated by Faust and Hoigne [82] using fulvic substances as photosensitizers of phenols in natural waters. These latter mechanisms correspond to the indirect photolysis of M. In fact, Faust and Hoigne [82] reported that there are four possible routes of the excited photosensitizing action ... 

The present chapter concentrates on the photoelectrochemistry of aggregates of cyanine dyes adsorbed at the semiconductor electrodes with special emphasis given to the difference in the photosensitization action of polymer aggregate species and monomeric dye. 

It has been shown that Gram-positive bacteria, such as Escherichia coli, are susceptible to the photosensitizing action of a variety of photosensitizers, among them amphiphilic metalloporphyrins (Pd11) [16], cationic metallophthalocyanines (Zn11) [15,17], or water-soluble derivatives of chlorophylls [18]. 

The red toxin causes 1Ight-dependent lipid peroxidation 11421 and membrane disruption In plants 11431. by Its photosensitizing action that produces singlet oxygen 11441. 

The photosensitizing action of Ti02 pigments in isopropanol depends on their crystal structure and the presence of any surface modifications. The Ti02-ZnO-photocatalysed oxidation of hexane is a good model for polyolefins. Using e.s.r. and luminescence spectroscopy, Ti centres have been... 

Although the photosensitizing action of zinc oxide suspensions has aroused a good deal of interest over the years, notably for the production of hydrogen peroxide, very little attention has been given in academic studies to ZnO photosensitization in the dry state. The simplest photo-... 

As it follows from above-mentioned conclusions, decrease of photosensitizing action of HAC has to improve its light-protective effect. 

The mode of photosensitizing action of coumarins has been studied before [192]. An important mechanism in this action is coupling of the compounds to thymine of DNA [188]. Some plant cells especially the... 

On the other hand, Kamiya et al. [43] observed an increased photodegradation of eleven organophosphorus pesticides in humic water after complexation to a-, p-, and y-CyDs. They concluded that the promotion effects of CyDs towards photodegradation were attributable to their inclusion-trapping abilities, which are active not only to the pesticides, but also to photoradical species, such as superoxide and hydroxyl radicals, discharged by the photosensitization action of humic acids. 

Herbs listed in the Botanical Safety Handbook with potential photosensitizing action ... 

The nature of the anion, the metal ion impurity is bound to, should be very important for the resistance of the pol5Tner 42) to photooxidation in fact, with increasing electron affinity of the anion, the absorption of the metal compound tends to shift toward shorter wavelengths than those present in sunlight at earth levd. In this favourable case, the photosensitizing action of metal reddues should tend to decrease. 

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