title: A highly specific sodium aptamer probed by 2-aminopurine for robust Na+ sensing.
abstract: Sodium is one of the most abundant metals in the environment and in biology, playing critical ecological and physiological roles. Na+is also the most common buffer salt for nucleic acids research, while its specific interaction with DNA has yet to be fully studied. Herein, we probe a highly selective and robust Na+aptamer using 2-aminopurine (2AP), a fluorescent adenine analog. This aptamer has two DNA strands derived from the Ce13d DNAzyme. By introducing a 2AP at the cleavage site of the substrate strand, Na+induces ∼40% fluorescence increase. The signaling is improved by a series of rational mutations, reaching >600% with the C10A20double mutant. This fluorescence enhancement suggests relaxed base stacking near the 2AP label upon Na+binding. By replacing a non-conserved adenine in the enzyme strand by 2AP, Na+-dependent fluorescence quenching is observed, suggesting that the enzyme loop folds into a more compact structure upon Na+binding. The fluorescence changes allow for Na+detection. With an optimized sequence, a detection limit of 0.4 mM Na+is achieved, reaching saturated signal in less than 10 s. The sensor response is insensitive to ionic strength, which is critical for Na+detection.
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Wenhu
authors.initials: W
authors.lastname: Zhou
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Ding
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China liujw@uwaterloo.ca.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D015075:2-Aminopurine / Q000737:chemistry*; D052157:Aptamers, Nucleotide / Q000737:chemistry* / Q000235:genetics; D020029:Base Pairing; D015374:Biosensing Techniques; D021881:DNA, Catalytic / Q000378:metabolism; D009154:Mutation; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D052157:Aptamers, Nucleotide; D021881:DNA, Catalytic; D009841:Oligonucleotides; D015075:2-Aminopurine; D012964:Sodium