Photosensitization mechanism

Peng Q, Moan J, Nesland JM, Rimington C (1990) Aluminum phthalocyanines with asymmetrical lower sulfonation and with symmetrical higher sulfonation a comparison of localizing and photosensitizing mechanism in human tumor LOX xenografts. Int J Cancer 46 719-26. 

UVA exposure of cells gives rise to 8-oxodGuo that was detected by HPLC-ECD. Evidence was provided that mostly O2 is involved in the UVA induced formation of 8-oxodGuo as the result of a predominant type II photosensitization mechanism. ... 

Smith G, McGimpsey WG, Lynch MC, Kochevar IE, Redmond R. An efficient oxygen independent 2-photon photosensitization mechanism. Photochem Photobiol 1994 59 135-9. 

The main adverse effects of the NSAID carprofen are cutaneous and hepatic. Photoreactions are being increasingly reported and its chemical similarity to benoxaprofen is worth noting (SEDA-12, 84). The photosensitivity mechanism is either toxic or allergic. 

It has been demonstrated in this short review that the understanding of the photosensitization mechanism in polymers may be applied for the improvement of their photostability and for the development of polymers with controlled lifetime. 

An electron-transfer mechanism from the photosensitizer excited state to triazines has been proposed, which has permitted a satisfactory interpretation of the observed fluorescence quenching. The steps of the photosensitization mechanism of PAGs with bromine-containing compounds by BPHTs are summarized below ... 

Hoebeke, M. (1995) The importance of liposomes as models and tools in the understanding of photosensitization mechanisms, J. Photochem. Photobiol. B Biol., 28, 189-196. 

Scheme 35. Scission of pyrimidine dimers by a singlet photosensitization mechanism (154).

Inhibition of EGF-R tyrosine kinase by hypericin 1 was shown to be irreversible, non-competitive and time as well as temperature dependent. The IC50 increased from 0.75 pM in the dark to 44 nM with light illumination for 30 min. This effect was presumably due to a type I photosensitization mechanism since exclusion of oxygen did not alter the inhibition curve. Some Ser/Thr protein kinases (e.g., protein kinase A, casein kinase 1 and 2) and the enzyme 5 -nucleotidase were not inhibited even at concentrations > 100 pM [144]. However, the same authors recently reported that hypericin 1 in addition to protein kinase C also caused the light-dependent inhibition of certain other Ser/Thr kinases (e.g. protein kinase CK-2, mitogen-activated kinase) and the insulin receptor tyrosine kinase, while it was ineffective towards the cytosolic tyrosine kinases Lyn, Fgr, TPK-IIB and CSK. These results suggest that distantly related protein kinases could still share common reactive domains for the interaction with hypericin 1 [156]. In contrast to the above mentioned studies, Richter and Davies [157] observed no inhibition of EGF-induced tyrosine phosphorylation of the EGF-R in HN5 squamous carcinoma... 

G. Smith, W.G. McGimpsey, M.C. Lynch, I.E. Kochevar, R.W. Redmond (1994). An efficient oxygen independent two-photon photosensitization mechanism. Photochem. PhotobioL, 59, 135-139. 

Fig. 3. Photosensitization mechanism based on electron transfer from triplet-state anthracene to the iodonium initiator (see reference 73).

Smith G et al. An efficient oxygen independent two-photon photosensitization mechanism. Photochemistry and Photobiology 59 135-9, 1994. 

Their effects on long-term performance, particularly photostability is much more variable and depends on the photosensitization mechanism [20]. However, they can all be improved to the level of non-degradable plastics by the use of inexpensive stabilizing systems [14] should this be required in the future. 

Photosensitivity, mechanical integrity, corrosion protection, and suitable adhesion properties. 

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