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BIOLOGICAL DEACTIVATION AND SINGLE‐STRAND BREAKAGE OF PLASMID DNA BY PHOTOSENSITIZATION USING TRIS(2,2′‐ BIPYRIDYL)RUTHENIUM(II) AND PEROXYDISULFATE
Author(s) -
AboulEnein Ahmed,
ScHulteFrohlinde Dietrich
Publication year - 1988
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1988.tb02782.x
Subject(s) - ruthenium , chemistry , tris , quantum yield , peroxydisulfate , dna , aqueous solution , irradiation , divalent , photochemistry , ion , pbr322 , dna damage , catalysis , plasmid , organic chemistry , biochemistry , physics , quantum mechanics , nuclear physics , fluorescence
— Single‐strand break formation and biological deactivation of plasmid pBR322 DNA in the presence of tris(2,2′‐bipyridyl)‐ruthenium(II), Ru(bpy)2/3; + , and K 2 S 2 O 8 , upon irradiation with visible light(400–500 nm), were studied in aqueous solution at room temperature. Conditions of complete binding of Ru(bpy)2/3; + to the strand were employed. The damage is initiated mainly by the SO 2/3; ; radical anion. Under anoxic conditions at a ratio of nucleotide to sensitizer concentrations (N/S) of 18 and S 2 O2/8 ‐ concentrations of 0.5 mM the quantum yield of single‐strand break (ssb) formation is φ ssb = 8.4 times 10 ‐3 while that of biological deactivation (bd) is Ø bd = 7.6 times 10 ‐3 (φ ssb = 5.2 times 10 ‐3 6.4 times 10 ‐ 3, 6.0 times 10 ‐3 and φ bd = 4.2 times 10 ‐3 , 5.2 times 10 ‐ 3, 4.8 times 10 ‐3 at N/S=3, 6, and 9, respectively). The quantum yields are approximately 2.5 times smaller in air‐saturated solutions. At N/S = 18 about 33 SO 4 ‐ radical anions are required per one lethal event. φ bd increases linearly with the S 2 Oφ ‐ concentration (up to 0.5 mM). The damage to DNA is drastically reduced on addition of mono‐ or divalent salts (e.g. NaC10 4 , MgCl 2 ). These additives cause the release of Ru(bpy)2 + from the strand. The observed damage to DNA is thus the result of a site specific reaction. When the phenanthroline analogue, Ru(phen)φ + , is used as sensitizer, φ ssb and φ bd are three times smaller.