Photolytic covalent binding of indoleacrylic acid to DNA.
E-beta-Indol-3-ylacrylic acid (IA), radiolabelled at the 2 position with 14C, and calf thymus DNA have been irradiated with UV light (lambda greater than 280 nm) in phosphate buffer (pH 7.0). Re-isolation of the DNA indicates covalent binding of IA at levels of up to 295 nmol IA/mg native DNA (0.097 IA/base). Binding is observed for both native and heat denatured DNA, but is more efficient with the latter. Quantum efficiencies of 2.60 X 10(-5) and 2.30 X 10(-4) mol IA bound to native DNA/mol photon absorbed have been measured at 308 and 266 nm, respectively. Studies with the four polyribonucleotides indicate a strong preference for binding to poly[U]. Photolysis of either untreated or enzymatically degraded labeled native DNA with 254 nm light leads to the reformation of IA, and a 2 + 2 photocycloadduct of IA and thymidine has been isolated and characterized and matched by HPLC to a DNA derived adduct. Equilibrium dialysis studies provide no evidence for preassociation of IA to DNA.
Farrow
S J
SJ
Department of Chemistry, Purdue University, West Lafayette, IN 47907.
Mohammad
T
T
Baird
W
W
Morrison
H
H
D002273:Carcinogens; D004247:DNA / Q000528:radiation effects; D007211:Indoles; D010782:Photolysis; D013936:Thymidine; D014466:Ultraviolet Rays
D002273:Carcinogens; D007211:Indoles; C001446:indoleacrylic acid; D004247:DNA; D013936:Thymidine