Photo inactivation

Several novel porphyrin derivatives can then be obtained by following the mentioned cycloaddition methodologies many of the new products fulfil the requirements to be considered as potential new drugs mainly for the detection and treatment (PDT) of cancer situations and in the photo-inactivation of microorganisms. 

Other evidence indicates however that it is unlikely that histidine is part of the catalytic site. The enzyme can be photo-inactivated in the... 

J. Mitchell, S. McPherson, W. Degraff, J. Gamson, A. Zabell, A. Russo (1985). Oxygen dependence of hematoporphyrin derivative-induced photo-inactivation of Chinese hamster cells. Cancer Res., 45, 2008-2011. 

PHOTOREACTIVATION AND PHOTO INACTIVATION OF PHOTOSYSTEM II AFTER A COMPLETE REMOVAL OF MANGANESE FROM PEA SUBCHLOROPLAST PARTICLES... 

PHOTO INACTIVATION OF PS-II. It might be assumed that the reactivation of electron transfer by Mn++ (Fig.4) is related to a destructive photooxidation of the organic matter surrounding the RC. However, it is not the case. We showed /9/ that the complete removal of Mn from DT-20 particles considerably increases the sensitivity of PS-II to the inhibitory action of light. A two-minute exposition of PS-II particles lacking Mn to the light, used usually to measure the PS-II activities, leads to the loss of the capability of PS-II to be reactivated by the subsequent addition of Mn " (Ffg.5). We showed that this photoinactiva-... 

Photosystem II reaction center is susceptible to light induced damage and steady state photosynthesis is maintained by continual repair of the photo-inactivated photosystems. An increase in the rate of inactivation (by over excitation of PS II) or a decrease in the rate of repair of PSII centers can result in accumulation of damaged PS II and consequent photoinhibition of photosynthesis. Since the assembly and stability of PS II complex involves close interaction with membrane lipids, photoinhibition and recovery of PS II centers are likely to be affected by the lipid composition of the thylakoid membrane. 

Vargas, E, Rivas, C. and Fernandez, A. 2006. Photodegradation and phototoxicity of antibacterial agents and the new alternatives for the photo-inactivation... 

Used industrially as a chemical intermediate in the manufacture of couplers for color photography, as a photo polymerization agent for vinyl compounds, as a solvent, and as an enzyme inactivator in biological research. 

For Aspergillus niger extracellular endo-D-galacturonanase, the role of histidine in the enzyme reaction was investigated by the method of photo-oxidative inactivation, catalyzed by Methylene Blue.140 The inactivation of the enzyme was paralleled by the decomposition of histidine. The similarity of pH profiles, as well as the values of the rate constants of enzyme inactivation (4.0 X 10-2 min-1) and of decomposition of histidine (3.9 X 10-2 min-1), indicate that one of the five histidine residues present in the molecule of the enzyme141 is essential for its activity. 

Melis, A., Zhang, L., Forestier, M., Ghirardi, M. L. and Seibert, M. (2000) Sustained photo-biological hydrogen gas production upon reversible inactivation of oxygen evolution in the green alga Chlamydomonas reinhardtii. Plant Physiol., 122, 127-36. 

Reduction of Ozonized Lysozyme. Methionine sulfoxide can revert to methionine with the generation of the lytic activity for photo-oxidized lysozyme (14). We tested whether the ozonized lysozyme could be reactivated by chemical reduction. The ozonized lysozyme was treated with 2-mercaptoethanol, dialysed, purified by passage through a column of Sephadex G-25 and lyoph-ilized. The product showed no increase in its lytic activity. This is not surprising because residues other than methionine are oxidized, but it may be concluded that the oxidation of methionine alone cannot account for enzyme inactivation. 

Munakata, N. Saito, M. Hieda, K. Inactivation action spectra of Bacillus subtilis spores in extended ultraviolet wavelengths (50-300 nm) obtained with synchrotron radiation. Photo-chem. Photobiol. 1991, 54 (5), 761-768. 

Although chloramphenicol inhibits carotenoid synthesis, it also inactivates photo-chemically responsive membranes in which carotenoids are located, and hence previous conclusions that the enzymes involved in carotenoid biosynthesis are themselves synthesized in the cytoplasm are not strictly valid. However, the demonstration367 that dark-grown Euglena gracilis, which has carotenoids localized in the proplastids, can synthesize carotenoids in the presence of chloramphenicol indicates that such synthesis is not dependent on protein synthesis in the proplastid. 

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