ACMA (9-amino-6-chloro-2-methoxy acricline) forms three complexes in the presence of DNA

摘要

The interaction of ACMA (9-amino-6-chloro-2-methoxy acridine) (D) with DNA (P) has been studied by absorbance, fluorescence, circular dichroism, spectrophotometry, viscometry and unwinding electrophoresis. A T-jump kinetic study has also been undertaken. The experimental data show that, totally unlike other drugs, ACMA is able to form with DNA three complexes (PD_I, PD_(II), PD_(III)) that differ from each other by the characteristics and extent of the binding process. The main features of PD_I fulfil the classical intercalation pattern and the formation/ dissociation kinetics have been elucidated by T-jump techniques. PD_(II) and PD_(III) are also intercalated species but, in addition to the dye units lodged between base pairs, they also bear dye molecules externally bound, more in PD_(III) relative to PD_(II). A reaction mechanism is put forward here. Comparison between absorbance, fluorescence and kinetic experiments has enabled us to determine the binding constants of the three complexes, namely (6.5 ± 1.1) x 10~4 M_(-1) (PD_I), (5.5 ± 1.5) x 10~4 M~(-1) (PD_(II)) and (5.7 ± 0.03) x 10~4 M_(-1) (PD_(III)). The Comet assay reveals that the ACMA binding to DNA brings about genotoxic properties. The mutagenic potential studied by the Ames test reveals that ACMA can produce frameshift and transversion/transition mutations. ACMA also is able to produce base-pair substitution in the presence of S9 mix. Moreover, the MTT assays have revealed cytotoxicity. The biological effects observed have been rationalized in light of these features.