title: A Selective Na(+) Aptamer Dissected by Sensitized Tb(3+) Luminescence.
abstract: A previous study of two RNA-cleaving DNAzymes, NaA43 and Ce13d, revealed the possibility of a common Na(+) aptamer motif. Because Na(+) binding to DNA is a fundamental biochemical problem, the interaction between Ce13d and Na(+) was studied in detail by using sensitized Tb(3+) luminescence spectroscopy. Na(+) displaces Tb(3+) from the DNAzyme, and thus quenches the emission from Tb(3+) . The overall requirement for Na(+) binding includes the hairpin and the highly conserved 16-nucleotide loop in the enzyme strand, along with a few unpaired nucleotides in the substrate. Mutation studies indicate good correlation between Na(+) binding and cleavage activity, thus suggesting a critical role of Na(+) binding for the enzyme activity. Ce13d displayed a Kd of ∼20 mm with Na(+) (other monovalent cations: 40-60 mm). The Kd values for other metal ions are mainly due to non-specific competition. With a single nucleotide mutation, the specific Na(+) binding was lost. Another mutant improved Kd to 8 mm with Na(+) . This study has demonstrated a Na(+) aptamer with important biological implications and analytical applications. It has also defined the structural requirements for Na(+) binding and produced an improved mutant.
authors.affiliation: School of Pharmaceutical Sciences, Central South University, 172 Tongzipo Road, Changsha, Hunan, 410013, China.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Wenhu
authors.initials: W
authors.lastname: Zhou
authors.affiliation: School of Pharmaceutical Sciences, Central South University, 172 Tongzipo Road, Changsha, Hunan, 410013, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Ding
authors.affiliation: School of Pharmaceutical Sciences, Central South University, 172 Tongzipo Road, Changsha, Hunan, 410013, China. liujw@uwaterloo.ca.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada. liujw@uwaterloo.ca.
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D021881:DNA, Catalytic / Q000737:chemistry* / Q000378:metabolism; D049449:Luminescence; D008163:Luminescent Measurements; D012964:Sodium / Q000737:chemistry* / Q000378:metabolism; D013725:Terbium / Q000032:analysis*
chemical_list: D021881:DNA, Catalytic; D013725:Terbium; D012964:Sodium
keywords: aptamers; luminescence; sensors; sodium; terbium