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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
Author(s) -
Genest D.,
Malfoy B.
Publication year - 1986
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360250309
Subject(s) - chemistry , ethidium bromide , polynucleotide , ionic strength , intercalation (chemistry) , fluorescence , bromide , circular dichroism , ionic bonding , polymer , solvent , crystallography , platinum , stereochemistry , aqueous solution , inorganic chemistry , organic chemistry , dna , ion , biochemistry , catalysis , physics , quantum mechanics
A time‐resolved fluorescence study of ethidium bromide (EB) in the presence of poly(dG‐dC) and of poly(dG‐dC) modified by chlorodiethylenetriamine platinum(II) 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 Z‐conformation (≃25 ns) than when bound to the B‐conformation (≃23.7 ns). The nature of the salt has been checked. In the presence of 2.5 M NaClO 4 , no transition from the Z‐conformation to another conformation is observed when EB is added. On the contrary, in the presence of 4.25 M NaCl, 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(dG‐dC) 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.