Nanosecond fluorescence studies of noncovalent interaction of monomeric and dimeric intercalators with DNA

Publisher Website
Google Scholar
Abstract
The noncovalent interaction of 2-aminodipyrido [1,2-a:3'',2''-d]imidazole (Glu-P-2) and its derivatives, which are potent mutagens isolated from L-glutamic acid pyrolysate, with calf thymus DNA was studied by steady-state and nanosecond fluoresence spectroscopies. The fluorescence of these compounds exhibits static quenching by noncovalent interaction with DNA. Fluorescence lifetimes of the free and intercalated states of these compounds were determined to be 9-10 and 0.5-1 ns, respectively. The bisintercalative effect of the dimeric analogue of Glu-P-2, bis(Glu-P-2)spermine (2GP-SP), to DNA was also investigated. This 2GP-SP, which has two Glu-P-2 moieties at each end of spermine, indicates a strong intramolecular interaction exhibiting remarkable quenching of fluorescence spectrum and lifetime (.female. = 3.5 ns) in the absence of DNA. In the presence of DNA, however, the 3.5-ns lifetime component of fluorescence disappeared, and a two-exponential decay of fluorescence (t = .apprx. 10 and 1.5 ns) was observed at a DNA concentration of more than .apprx. 0.001 mM P, while the solution containing a very dilute DNA concentration (.ltoreq. 0.001 mM P) exhibits a three-component decay of fluorescence (1.5, 3.5, and .apprx. 10 ns). The potent bis intercalation of two moieties in 2GP-SP with an identical DNA molecule was suggested by the DNA-concentration dependence of these fluorescence lifetimes and their intensity.