title: Wavelength dependence for the photoreactions of DNA-psoralen monoadducts. 1. Photoreversal of monoadducts.
abstract: We have studied the wavelength dependence for the photoreversal of a monoadducted psoralen derivative, HMT [4'-(hydroxymethyl)-4,5',8-trimethylpsoralen], in a single-stranded deoxyoligonucleotide (5'-GAAGCTACGAGC-3'). The psoralen was covalently attached to the thymidine residue in the oligonucleotide as either a furan-side monoadduct, which is formed through the cycloaddition between the 4',5' double bond of the psoralen and the 5,6 double bond of the thymidine, or a pyrone-side monoadduct, which is formed through the cycloaddition between the 3,4 double bond of the psoralen and the 5,6 double bond of the thymidine. As a comparison, we have also investigated the wavelength-dependent photoreversal of the isolated thymidine-HMT monoadducts. All photoreversal action spectra correlate with the extinction spectra of the isolated monoadducts. In the case of the pyrone-side monoadduct, two absorption bands contribute to the photoreversal with a quantum yield of 2 X 10(-2) at wavelengths below 250 nm and 7 X 10(-3) at wavelengths from 287 to 314 nm. The incorporation of the monoadduct into the DNA oligomer had little effect upon the photoreversal rate. For the furan-side monoadduct at least three absorption bands contribute to the photoreversal. The quantum yield varied from 5 X 10(-2) at wavelengths below 250 nm to 7 X 10(-4) at wavelengths between 295 and 365 nm. In contrast to the case of the pyrone-side monoadduct, the incorporation of the furan-side monoadduct into the DNA oligomer reduced the photoreversal rate constant at wavelengths above 285 nm.
mesh_terms: D003432:Cross-Linking Reagents / Q000494:pharmacology; D004277:DNA, Single-Stranded / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D004586:Electrophoresis; D005363:Ficusin / Q000378:metabolism / Q000494:pharmacology*; D005663:Furans / Q000378:metabolism; D011564:Furocoumarins / Q000494:pharmacology*; D009841:Oligonucleotides / Q000494:pharmacology; D011487:Protein Conformation; D013936:Thymidine / Q000378:metabolism; D014307:Trioxsalen / Q000031:analogs & derivatives / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D004277:DNA, Single-Stranded; D005663:Furans; D011564:Furocoumarins; D009841:Oligonucleotides; C016507:hydroxymethyltrioxsalen; D005363:Ficusin; C039281:furan; D013936:Thymidine; D014307:Trioxsalen