Photochemistry of the furan-side 8-methoxypsoralen-thymidine monoadduct inside the DNA helix. Conversion to diadduct and to pyrone-side monoadduct

We have studied the photochemical reactions of 8-methoxypsoralen (8-MOP) with calf thymus DNA. Analysis of the photoproducts formed was carried out by enzymatic digestion of the 8-MOP-modified DNA, followed by HPLC separation of photoadducts by high-pressure liquid chromatography (HPLC). The 4'...

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Bibliographic Details
Published in:Biochemistry (Easton) 1985-03, Vol.24 (7), p.1669-1676
Main Authors: Tessman, John W, Isaacs, Stephen T, Hearst, John E
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Biological and medical sciences
Cattle
DNA
Fundamental and applied biological sciences. Psychology
In Vitro Techniques
Methoxsalen
Molecular biophysics
Photochemistry
Photochemistry. Photosynthesis. Bioluminescence
Radiation-biomolecule interaction
Thymidine
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Summary:We have studied the photochemical reactions of 8-methoxypsoralen (8-MOP) with calf thymus DNA. Analysis of the photoproducts formed was carried out by enzymatic digestion of the 8-MOP-modified DNA, followed by HPLC separation of photoadducts by high-pressure liquid chromatography (HPLC). The 4',5' (furan-side) monoadduct of 8-MOP bound to thymidine is converted to cross-linked thymidine-8-MOP-thymidine diadduct by 341.5 nm light with a quantum yield of 0.028 +/- 0.004. This is 4 times greater than the quantum yield for initial adduct formation (0.0065 +/- 0.0004). When low levels of 8-MOP are covalently bound to DNA by using 397.9 nm light, less than 10% of the adducts formed are diadducts yet nearly 70% are in 5'-TpA cross-linkable sites. The furan-side monoadducts in these sites can subsequently be converted to diadduct or to a lesser extent 3,4 (pyrone-side) monoadduct.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00328a015