A highly specific sodium aptamer probed by 2-aminopurine for robust Na+ sensing
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Date
2016-09-20
Authors
Zhou, Wenhu
Ding, Jinsong
Liu, Juewen
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
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 similar to 40% fluorescence increase. The signaling is improved by a series of rational mutations, reaching > 600% with the C(10)A(20) double 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.
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Keywords
Lanthanide-Dependent Dnazyme, In-Vitro Selection, Resonance Energy-Transfer, Uranyl-Specific Dnazyme, RNA-Cleaving Dnazyme, Metal-Ions, Dna Enzyme, Living Cells, Sites, Sensors