title: Synthesis of unimolecularly circular G-quadruplexes as prospective molecular probes.
abstract: Synthesis of unimolecularly circular G-quadruplex has been accomplished for the first time during our investigation on the template basis of G-quadruplex through chemical ligations of guanine-rich linear sequences of oligodeoxyribonucleotides. The uniqueness of this newly designed circularization course is its self-recognition and self-templating on the scale of individual strand of oligodeoxyribonucleotide in which the same linear sequence serves both as a template and as a substrate simultaneously. The results from our exonuclease and DNAse hydrolysis studies confirm that there is indeed absence of open termini within the structure of the identified circular product. Our subsequent investigation on the loop-size effect indicates that the unimolecularly circular G-quadruplex possessing two or more thymine nucleotides within their connecting loops is readily attainable, while the linear sequence with a single thymine nucleotide between guanine tracts is not a proper precursor for our ligation reaction. In addition, conformation dependency of the circularization course as well as the effects of alkali ions, pH values and concentration of potassium ions on the circularization reaction are examined during our investigation. The implication of our current studies and possible application of the obtained unimolecularly circular G-quadruplex in certain biological processes are also discussed in this report.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, Peking University, 38 Xueyuan Road, Hiandian District, Beijing 100083.
authors.forename: Tianyan
authors.initials: T
authors.lastname: Zhou
authors.forename: Guoshu
authors.initials: G
authors.lastname: Chen
authors.forename: Yifan
authors.initials: Y
authors.lastname: Wang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Ming
authors.initials: M
authors.lastname: Yang
authors.forename: Tianhu
authors.initials: T
authors.lastname: Li
mesh_terms: D004247:DNA / Q000096:biosynthesis* / Q000737:chemistry; D011088:DNA Ligases / Q000378:metabolism; D004270:DNA, Circular / Q000096:biosynthesis* / Q000737:chemistry; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes / Q000096:biosynthesis* / Q000737:chemistry; D011188:Potassium / Q000494:pharmacology
chemical_list: D004270:DNA, Circular; D007477:Ions; D015345:Oligonucleotide Probes; D006147:Guanine; D004247:DNA; D011088:DNA Ligases; D011188:Potassium