Study the effects of divalent metallic ions on the combination of DNA and histones with fluorescence anisotropy assays

The effects of divalent ions(Mn2 ,Mg2 ,Ca2 ) on the interaction between DNA and histone are studied using a fluorescence anisotropy assay. Fluorescence anisotropies of DNA and DNA-histone in the presence of divalent ions(Mn2 ,Mg2 ,Ca2 ) are measured. The results indicate that histone reduces the fluorescence anisotropy of lambda DNA while the divalent ions(Mn2 ,Mg2 ,Ca2 ) significantly enhance the fluorescence anisotropy. Compared to the case of DNA incubated with histone alone,there are more histones binding to DNA when divalent ion,histone and DNA are incubated together. We also find that Mn2 makes the DNA-histone complexes more condensed than the other ions do.