title: Chemical synthesis and thermodynamic characterization of oxanine-containing oligodeoxynucleotides.
abstract: Oxanine (Oxa, O), one of the major damaged bases from guanine generated by NO- or HNO2-induced nitrosative deamination, has been considered as a mutagen-potent lesion. For exploring more detailed properties of Oxa, large-scale preparation of Oxa-containing oligodeoxynucleotide (Oxa-ODN) with the desired base sequence is a prerequisite. In the present study, we have developed a chemical synthesis procedure of Oxa-ODNs and characterized thermodynamic properties of Oxa in DNA strands. First, 2'-deoxynucleoside of Oxa (dOxo) obtained from 2'-deoxyguanosine by HNO2-nitrosation was subjected to 5'-O-selective tritylation to give 5'-O-(4,4'-dimethoxytrityl)-dOxo (DMT-dOxo) with a maximum yield of 70%. Subsequently, DMT-dOxo was treated with conventional phosphoramidation, which resulted in DMT-dOxo-amidite monomer with a maximum yield of 72.5%. The amidite obtained was used for synthesizing Oxa-ODNs: the coupling yields for Oxa incorporation were over 93%. The prepared Oxa-ODNs were employed for analyzing the thermodynamic properties of DNA duplexes containing base-matches of O:N [N; C (cytosine), T (thymine), G (guanine) or A (adenine)]. Melting temperatures (Tm) and thermodynamic stability (DeltaG37(0)) were found to be lower by 6.83 approximately 13.41 degrees C and 2.643 approximately 6.047 kcal mol(-1), respectively, compared with those of oligodeoxynucleotides, which had the same base sequence except that O:N was replaced by G:C (wild type). It has also been found that Oxa-pairing with cytosine shows relatively high stability in DNA duplex compared with other base combinations. The orders of DeltaDeltaG37(0) were O:C > O:T > O:A > O:G. The chemical synthesis procedure and thermodynamic characteristics of Oxa-ODNs established here will be helpful for elucidating the biological significance of Oxa in relation to genotoxic and repair mechanisms.
authors.affiliation: International Innovation Center, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Seung Pil
authors.initials: SP
authors.lastname: Pack
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nonogawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kodaki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Makino
mesh_terms: D020029:Base Pairing; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D011684:Purine Nucleosides / Q000138:chemical synthesis / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: C504691:5'-O-(4,4'-dimethoxytrityl)-dOxo-amidite; D009838:Oligodeoxyribonucleotides; D011684:Purine Nucleosides; C468766:oxanine