Characterization of new furocoumarin derivatives by their dark and light-mediated action on RNA bacteriophage MS2

The monofunctional and bifunctional furocoumarin derivatives 8-methyl-3-carbethoxypsoralen (8Me3CPs) and 8-methoxypsoralen (8MOP) as well as their thiosubstituted derivatives (2-thio-8Me3CPs and 2-thio-8MOP) were compared in terms of their reactivities towards a ribonucleoprotein, the bacteriophage MS2. The order of their photoreactivities differed from that measured with nuclear DNA and mitochondrial DNA. Besides their widely investigated photoreactivity, their biological activity in the dark and after pre-irradiation was quantified. A parameter was defined which compares the number of molecules acting in the dark for 1 h with the number of absorbed photons which lead to the same degree of inactivation. The parameter for the furocoumarin derivatives examined, including 3-carbethoxypsoralen (3CPs) and 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), was in the following order: AMT greater than 3CPs greater than 8MOP greater than 8Me3CPs greater than 8Me3CPsS approximately 8MOPS. A similar parameter was also determined for the dark effect of pre-irradiated compounds.