Formation of the thiol adducts of 4'-(9-acridinylamino)methanesulfon-m-anisidide and their binding to deoxyribonucleic acid.

We investigated the interactions of 4'-(9-acridinylamino)methanesulfon-m-anisidide (mAMSA) with thiol-containing compounds and the potential binding of the thiolytic adducts to DNA. All thiols tested (glutathione, cysteine, coenzyme A, 2-mercaptoethanol and lactate dehydrogenase) formed adducts with mAMSA as evidenced by changes in the absorption spectrum of mAMSA and induction of fluorescence. Spectral changes induced by the thiols were different, suggesting that each thiol induced specific changes in the electronic structure of the acridine nucleus. Treatment of glutathione with p-chloromercuribenzoate eliminated the absorption spectral changes and induction of fluorescence, indicating that the reduced-thiol group is involved. In high ionic strength buffer, addition of calf thymus DNA induced fluorescence-quenching of both the mAMSA-glutathione and mAMSA-cysteine adducts without spectral shift. Viscometric studies showed that mAMSA and mAMSA-glutathione intercalated into DNA and produced similar increases in the length of linear DNA.