The effects of NaCl concentration on bleomycin-induced cleavages of single-strand and double-strand DNA fragments containing the phage G4 origin of complementary DNA Strand synthesis were investigated. It was found that bleomycin could be used as a reagent to analyze secondary and tertiary structures and subtle changes of DNA structures. The effects of NaCl concentration on cleavages of single-stranded DNA were distinct at every target site, indicating that the diversity of topolotical properties of DNA might change the selectivity of the bleomycin-induced DNA cleavage. These results showed alternative secondary structures within and close to the G4 origin of complementary DNA Strand synthesis.
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Acknowledgments. This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan