title: Modifications of circular DNA by photoalkylation.
abstract: The effects of photoalkylation on superhelical PM2 DNA were examined. The chief product was 8-(2-hydroxy-2-propyl)guanine, formed exclusively in sequences of alternating purines and pyrimidines. Other purine damages included 8-(2-hydroxy-2-propyl)adenine and smaller quantities of two uncharacterized adenine products. DNA strand breaks were formed with increasing irradiation. A small quantity of thymine-containing photodimers was formed. Photoalkylation of poly(dG-dC):poly(dG-dC) reduced the concentration of salt required to effect inversion of the circular dichroic spectrum. This suggests that photoalkylation induces the transition of poly(dG-dC):poly(dG-dC) from the right-handed B form of DNA to the left-handed Z form.
mesh_terms: D000478:Alkylation; D001435:Bacteriophages / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D002854:Chromatography, Paper; D002942:Circular Dichroism; D004270:DNA, Circular / Q000528:radiation effects*; D004279:DNA, Viral / Q000528:radiation effects*; D009690:Nucleic Acid Conformation / Q000528:radiation effects*; D010777:Photochemistry; D011687:Purines / Q000032:analysis; D013997:Time Factors
chemical_list: D004270:DNA, Circular; D004279:DNA, Viral; D011687:Purines