Dissociation of a model DNA compound dApdA by monochromatic soft X-rays in solids and comments on the high selectivity for 3' breakage in the phosphoester bond.
The dissociation products of dApdA (2'-deoxyadenylyl-(3'-5')-2'-deoxyadenosine) irradiated in the solid state by highly monochromatic soft X-rays (energy resolution, less than 10(-3) near the K-edge of phosphorus were analysed using thin-layer chromatography. The major chemical species identified were adenine base and 5'-dAMP in approximately equal amounts, indicating that the dissociation occurred between the 3' carbon (C3') of deoxypentose and its adjacent phosphorus over the energy range of 2.147-2.167 keV, including the K-edge resonance absorption of phosphorus at 2.153 keV. In conjunction with the accumulated data on the degradation of dApdA and related oligonucleotides by vacuum-UV radiation (above 7 eV), which generally indicate a simple, selective dissociation at the 3' side of the deoxypentose as observed with the soft X-rays, an hypothesis is presented on the molecular mechanism of radiation-induced breakage of phosphoester bonds that led to the selective 3' breakage, based on the differential flexibility of torsion angles of C3'-O3'-P and C4'-C5'-O5'-P groups in relation to those of the sugar ring.
Biological and Medical Research Division, Argonne National Laboratory, IL 60439-4833.
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D000225:Adenine / Q000032:analysis; D002855:Chromatography, Thin Layer; D003838:Deoxyadenine Nucleotides / Q000032:analysis; D015226:Dinucleoside Phosphates / Q000528:radiation effects*
D003838:Deoxyadenine Nucleotides; D015226:Dinucleoside Phosphates; C020269:2'-deoxyadenylyl-(3'-5')-2'-deoxyadenosine; D000225:Adenine