Binding characteristics of aflatoxin B1 with free DNA in vitro.

Abstract

In this paper, the binding characteristics of aflatoxin B1 (AFB1) with the herring sperm deoxyribonucleic acid (DNA) in vitro were investigated through different analytical methods. The ultraviolet-visible spectroscopy (UV-vis), fluorescence, and circular dichroism (CD) spectra results showed that a new AFB1-DNA complex was formed. All the results suggested that AFB1 interacted with free DNA in vitro in an intercalating binding mode. The results of the DNA melting experiments also showed that the melting temperature of DNA increased by about 12.1°C due to the addition of AFB1, which was supposed to be closely related to the intercalation of AFB1 into DNA. The agar gel electrophoresis experiments further confirmed that the binding mode of AFB1 and free DNA in vitro was indeed intercalation. In addition, the fluorescence quenching induced by adding AFB1 to the ethidium bromide-DNA (EB-DNA) mixture indicated the presence of competitive non-covalent intercalating binding interaction with a competitive binding constant of 5.58L/mol between AFB1, EB, and DNA. The thermodynamic data demonstrated that the main driving forces of the binding reaction were van der Waals forces and hydrogen bond. The resonance light scattering (RLS) assay results showed that the DNA binding saturation values of AFB1, EB, psoralen (PSO), and angelicin (ANG) were 2.14, 15.59, 0.74, and 0.74, respectively. These results indicated that the DNA binding capacity of AFB1 was weaker than that of EB, but stronger than those of PSO and ANG.