Molecular mechanisms of photosensitization in biological systems: from membrane targeting to molecular recognition in DNA

The exptl. strategies directed to clarify the mol. mechanisms of photosensitization in biol. systems initiated by UVA absorbing xenobiotic agents such as drugs are briefly discussed. Studies of hemolysis, protein crosslinking, phospholipid and cholesterol oxidn., release of markers entrapped in unilamellar liposomes, together with the anal. of the effect of metal ions on these processes are related to the membrane targeting. Photosensitizers can also interact with DNA double strand either through surface binding or intercalation. Photosensitization is followed through detn. of the linearization rate of supercoiled circular DNA with agarose gel electrophoresis, and through CD, fluorescence polarization and oxygen consumption techniques. Use of DNA sequencing of plasmid restriction fragments and oligonucleotides provides information about specific recognition on the double strand. The photophysics of the investigated mols. in the presence or in the absence of DNA supplies further information on the obsd. process.