5-METHOXYPSORALEN PHOTOADDUCT FORMATION - CONVERSION OF MONOADDUCTS TO CROSS-LINKS

5-Methoxypsoralen is often substituted for 8-methoxypsoralen in the ph otochemotherapy of psoriasis even though the nature of the resulting p hotadducts in cellular DNA has not been determined. A recent molecular mechanics study with a model oligonucleotide predicted that intercala ted 5-methoxypsoralen molecules would tend to favor the preferential f ormation of 3,4-monoadducts. Such a result would be contrary to the ph otoadduct patterns observed with other psoralens. In this study we sho w that 5-methoxypsoralen photoadducts formation is, in fact, very simi lar to that for other psoralens, i.e., the primary photoadduct is the 4',5'-monoadduct which can be quantitatively converted to crosslink.