Covalent modification of DNA by cis-Rh(phen)2Cl2+ upon irradiation in the red region.
The metal complex, cis-Rh(phen)2Cl2+ (phen = 1,10-phenanthroline), absorbs in the near UV region and is apparently transparent in the red region of the electromagnetic radiation. We have previously shown that the chemical can be photosensitized by the red light absorbing dye, methylene blue, and the activated compound forms permanent bonds with DNA. In the present paper we report that despite the negligible absorption of the metal complex beyond UVA (320-400 nm) region, irradiation with red light populates a highly reactive excited state, which forms covalent linkages with DNA. The purified DNA photoadducts indicate binding as high as 105 nmol Rh, which corresponds to 1.8% metal incorporation. The quantum efficiency for covalent binding of Rh complex to DNA with the 633 nm-excitation is in the range of 0.01-0.02 under anaerobic conditions. These data reveal that one Rh atom occurs approximately every 300 DNA bases. HPLC and UV/Vis analyses of the enzymatic digest of the photoadducts support that the DNA-Rh photoadducts are stable to nucleolytic enzymes. The DNA photo-modification is inhibited by the presence of oxygen indicating that the new excited state of cis-Rh(phen)2Cl2+ to be different from that populated by UVA excitation.
Mohammad
Taj
T
Department of Chemistry and Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907-2033, USA. taj@purdue.edu
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002417:Cattle; D004247:DNA / Q000737:chemistry* / Q000187:drug effects; D018736:DNA Adducts / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects*; D009942:Organometallic Compounds / Q000737:chemistry* / Q000494:pharmacology / Q000528:radiation effects; D010618:Phenanthrolines / Q000737:chemistry* / Q000494:pharmacology / Q000528:radiation effects; D010777:Photochemistry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013950:Thymus Gland / Q000737:chemistry / Q000528:radiation effects; D014466:Ultraviolet Rays
D018736:DNA Adducts; D009942:Organometallic Compounds; D010618:Phenanthrolines; C120941:bis(1,10-phenanthroline)rhodium(III); D004247:DNA