The influence of flavin mononucleotide on interaction in ethidium bromide-DNA system

The study of intercalator ethidium bromide (EB) interaction with DNA in the presence of vitamin B2 analogue flavin mononucleotide (FMN) is carried out using the differential scanning calorimetry (DSC) and spectrophotometry (SF). Calorimetric investigations indicate that addition of FMN leads to the increase of DNA melting temperature, enthalpy, entropy and free energy in its complex with EB. The spectra of binary (EB-DNA, DNA-FMN) and ternary (FMN-EB-DNA) systems at different temperatures are obtained. Comparison of the experimental spectra shows that the intensity of the summary spectrum (EB-DNA+FMN-DNA) is higher than the intensity of the ternary system spectrum obtained experimentally. It should be noted that the intensity difference rises with the temperature increasing. The observed by DSC and SF effects can be explained by the increase of the concentration of ethidium bromide associated with DNA in the presence of FMN