Fluorescence decay of ethidium bromide in the presence of the Z-conformation of poly-(dG-dC) and of poly(dG-dC) modified by chlorodiethylenetriamine platinum(II) chloride

✍ Scribed by D. Genest; B. Malfoy

• Publisher: Wiley (John Wiley & Sons)
• Year: 1986
• Tongue: English
• Weight: 638 KB
• Volume: 25
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360250309

✦ Synopsis

A timeresolved fluorescence study of ethidium bromide (EB) in the presence of poly(dGdC) and of poly(dGdC) modified by chlorodiethylenetriamine platinum(I1) chloride is presented under solvent conditions in which these polymers adopt the Z-conformation (high ionic strength). It is shown that these polynucleotides can intercalate a very small quantity of EB. The binding parameters have been determined. The fluorescence lifetime of EB is slightly higher when bound to the Zconformation (-25 ns) than when bound to the Bconformation (-23.7 ns). The nature of the salt has been checked. In the presence of 2.5M NaC104, no transition from the Z-conformation to another conformation is observed when EB is added. On the contrary, in the presence of 4.25M NaC1, EB induces a cooperative transition from the Z-conformation to a conformation characterized by a much higher affinity for EB intercalation. In the case of poly(dGdC) this last conformation is identical to the one observed at low ionic strength (B-conformation), but in the case of the platinated polymer this conformation is slightly different, as judged by the smaller value of the fluorescence lifetime of the intercalated EB.