DNA condensation monitoring after interaction with hoechst 33258 by atomic force microscopy and fluorescence...

DNA condensation was only observed after the addition of Hoechst 33258 (H33258) among various types of DNA binding molecules. The morphological structural change of DNA was found to depend on the H33258 concentration. On comparison of fluorescence spectrum measurements with AFM observation, it was found that fluorescence quenching of DNA-H33258 complexes occurred after DNA condensation. Additionally, we showed that DNA condensation by H33258 was independent of sequence selectivity or binding style using two types of polynucleotides, i.e. poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC). Moreover, it was concluded that the condensation was caused by a strong hydrophobic interaction, because the dissolution of condensed DNA into its native form on dimethyl sulfoxide (DMSO) treatment was observed. This study is the first report, which defines the DNA condensation mechanism of H33258, showing the correlation between the single molecule scale morphology seen on AFM observation and the bulky scale morphology observed on fluorescence spectroscopy.