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PROFLAVINE PHOTOSENSITIZATION OF DOUBLE AND SINGLE STRANDED DNA: EPR STUDY OF THE EFFECT OF VARIOUS SULPHUR-CONTAINING SUBSTANCES |
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| Authors: | Jacques Piette Claire-M Calberg-Bacq Albert Van de Vorst† |
| Institution: | Laboratory of General and Medical Microbiology, University of Liège, Sart-Tilman, 4000 Liège, Belgium;†Department of Atomic and Molecular Physics, University of Liège, Sart-Tilman, 4000 Liège, Belgium |
| Abstract: | Abstract—The proflavine-mediated photosensitization of both double-stranded calf thymus and single-stranded DNA from bacteriophage φ× 174 was followed in terms of the induction of free radicals in frozen solutions by EPR measurements in the presence of oxygen. The effect of the addition of various sulphur-containing substances to the proflavine DNA mixtures was studied and quantitatively expressed for definite amounts of proflavine bound to both DNAs. Upon irradiation with visible light, RS radicals were observed in the presence of these sulphur-containing substances. Some of them caused a decrease in the amount of peroxide radicals normally induced in the photosensitized DNA. This decrease appeared to be linked to the property of the compounds to interact with DNA in such a way that they modify the binding of proflavine to DNA. Cysteine, cysteamine, cystamine and cystine, protect calf thymus DNA against the "proflavine and light" free radical induction by 55, 58, 64 ahd 62% respectively. φ× 174 single-stranded DNA is also protected by the addition of cysteamine and cystamine, although to a lesser extent than calf thymus DNA (35%). These protection factors were measured under conditions where strong binding of the dye to the DNA was predominant. |
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