SOME PROPERTIES OF THE TRIPLET EXCITED STATE OF THE PHOTOSENSITIZING FUROCOUMARIN: 3-CARBETHOXYPSORALEN |
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| Authors: | J. C. Ronfard-Haret,D. Averbeck,&dagger ,R. V. Bensasson,E. Bisagni,&dagger E. J. Land |
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| Affiliation: | *Laboratoire de Biophysique Inserm U.201, Museum National d'Histoire Naturelle,61, rue Buffon 75005 Paris, France;†Institut Curie, Section de Biologie, 16, rue d'Ulm, 75231 Paris Cedex 05, France;‡Institut Curie, Batiment 110, 91405 Orsay, France;§Paterson Laboratories, Christie Hospital and Holt Radium Institute, Manchester M2O 9BX, UK |
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| Abstract: | Abstract— 3-Carbethoxypsoralen (3-CPs) has been tested in the photochemotherapy of psoriasis. It only forms monoadducts with DNA and is being considered as a non-carcinogenic alternative to 8-MOP which itself forms DNA crosslinks that arc difficult to repair. Using laser flash photolysis or pulse radiolysis, the triplet state of 3-CPs, a possible intermediate in photosensitization, has been generated in several solvents: ethanol, water and benzene. The triplet lifetime, extinction coefficient and quantum efficiency of formation have been measured. Triplet reactivities towards (i) the solvents used, (ii) 3-CPs, (iii) oxygen, (iv) tryptophan and (v) tyrosine, leading, respectively, to photoadditions with water, ethanol and 3-CPs, to 1O2, semioxidized tryptophan and semioxidized tyrosine, (vi) thymine and (vii) uracil have been investigated. The dark binding of 3-CPs to DNA has been studied by comparing the reactivity of eaq- with free 3-CPs, free DNA and the 3-CPs DNA complex. Some photophysical and photochemical properties of 4',5'di-hydro-3-carbethoxypsoralen(DH–3-CPs), model of the main fluorescent photo-product of 3-CPs, have also been investigated. Biological consequences of the photochemical properties of 3-CPs andDH–3-CPs have been studied in a cellular system (haploid yeast). |
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