Interactions of new derivatives of anthracene with calf thymus DNA

摘要

A series of anthracenes and bis-anthracenes have been subjected to photophysical study in water and in solutions of calf thymus DNA. The DNA binding properties have been studied using absorption, emission, melting DNA, viscometric and fluorescence polarization experiments. These studies indicate intercalation of anthryl probes into DNA helix. Trifunctional molecules consisting of two anthracenes linked by a polyamine chain intercalate into DNA with binding constants in the range 2x10~4 ― 8x10~5 M~(-1) depending on the linker properties. In the homogeneous solution the fluorescence of anthracene moieties shows the mono-exponential decay, with a life-time of about 8-9 ns. Upon binding to DNA, the fluorescence of anthryl probes is strongly quenched by the DNA bases. Furthermore, the fluorescence decay profile shows a distinct bi-exponential behavior in the presence of DNA with a short-lived component of 8 ns and with dominating long-lived component of 30 ns. The anthryl triplet decay kinetics is also altered by the presence of the polynudeotides. On the one hand the yield of the triplet is dramatically decreased, and on the other hand the life-time of the triplet is increased in the DNA solution. The reaction of the aquated electron (e_(aq)~-) with intercalators has been investigated by pulse radiolysis technique in water and in the presence of DNA. The rate of reaction of e_(aq)~- with intercalated anthracenes is reduced tenfold in respect to that for free molecules. While direct scavenging of e_(aq)~- by the anthracenes intercalated into DNA was observed, electron migration from DNA base radical anion to the intercalator was not.