SEQUENCE SPECIFICITY OF TETRAHYDROBENZOPSORALEN PHOTOBINDING TO DNA

The sequence specificity of photobinding to DNA of two tetrahydrobenzo psoralen derivatives has been investigated by testing the photoreactiv ity toward a number of self-complementary oligonucleotides. The thermo dynamic constant for noncovalent binding to each DNA sequence was eval uated. The extent of photoreactivity was greatly dependent upon base c omposition. The two tetracyclic compounds show similar behavior in com parison to other bifunctional derivatives. Their overall rate constant s were greatly enhanced in comparison to classical psoralens. However, their high efficiency of covalent binding is counterbalanced by low a ffinity for noncovalent interaction with DNA.