title: Pyrene excimer fluorescence as a probe for parallel G-quadruplex formation.
abstract: The formation and properties of G-quadruplex structures from short single-strand oligonucleotide conjugates possessing two to four guanines and a 5'-terminal pyrenebutanol are reported. The 4-G conjugate forms a stable G-quadruplex under low or high potassium ion concentrations, whereas the 3-G conjugate forms a stable G-quadruplex only in the presence of high potassium. The 2-G conjugate fails to form a stable G-quadruplex even at low temperature and high potassium concentration. Both pyrene monomer and excimer fluorescence are observed for the G-quadruplex structures, whereas only monomer fluorescence is observed for the single-strand conjugates. Thus, pyrene excimer fluorescence can be used as a probe for the formation of G-quadruplex structures. The excimer/monomer intensity ratios for the G-quadruplex structures are dependent upon both the temperature and potassium or lithium salt concentration. The salt effect is attributed to a change in the structure of the hydrophobic pyrene chromophores, which are assembled on the 5'-face of the G-quadruplex as a consequence of electrostriction.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Huihe
authors.initials: H
authors.lastname: Zhu
authors.forename: Frederick D
authors.initials: FD
authors.lastname: Lewis
mesh_terms: D002942:Circular Dichroism; D015180:Electrophoresis, Gel, Two-Dimensional; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D018021:Lithium Chloride / Q000737:chemistry; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005456:Fluorescent Dyes; D009838:Oligodeoxyribonucleotides; D011721:Pyrenes; D006147:Guanine; D011189:Potassium Chloride; C030984:pyrene; D018021:Lithium Chloride