title: Fluorescence-detected circular dichroism of ethidium in vivo and bound to deoxyribonucleic acid in vitro.
abstract: Fluorescence-detected circular dichroism (FDCD) spectra are reported for ethidium in Escherichia coli cells and bound to E. coli DNA in vitro. FDCD bands are observed at 325 and 385 nm. These bands change amplitude as the ethidium to DNA ratio changes. Spectra are similar for in vivo and in vitro measurements. However, the bands at 325 and 385 nm disappear when ethidium binds to macromolecules without intercalating between base pairs. The results demonstrate that FDCD spectra can be measured in cell suspensions and indicate that ethidium binds to nucleic acids in E. coli cells by intercalation.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism / Q000295:instrumentation / Q000379:methods; D004269:DNA, Bacterial; D004926:Escherichia coli; D004996:Ethidium; D009690:Nucleic Acid Conformation; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods
chemical_list: D004269:DNA, Bacterial; D004996:Ethidium