An Exceptionally Selective DNA Cooperatively Binding Two Ca2+ Ions |
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Authors: | Wenhu Zhou Runjhun Saran Po‐Jung Jimmy Huang Prof Dr Jinsong Ding Prof Dr Juewen Liu |
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Affiliation: | 1. School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China;2. Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON, Canada |
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Abstract: | Ca2+ is a highly important metal ion in biology and in the environment, and thus there is extensive work in developing sensors for Ca2+ detection. Although many Ca2+‐binding proteins are known, few nucleic acids can selectively bind Ca2+. DNA‐based biosensors are attractive for their high stability and excellent programmability. We report a RNA‐cleaving DNAzyme, EtNa, cooperatively binding two Ca2+ ions but to only one Mg2+. Four DNAzymes with known Ca2+‐dependent activity were compared, and the EtNa had the best selectivity for Ca2+. The EtNa is 90 times more active in Ca2+ than in Mg2+. Phosphorothioate (PS) modification showed that both non‐bridging oxygen atoms at the scissile phosphate contribute equally to Ca2+ binding. The pH–rate profile suggests two concurrent deprotonation reactions. EtNa was further engineered for Ca2+ sensing, and found to have a detection limit of 17 μm Ca2+ and excellent selectivity. The detection of Ca2+ in tap water was performed, and the result was comparable with that by ICP‐MS. This study offers new fundamental insights into Ca2+ binding by nucleic acids and improved metal selectivity by having multiple cooperative metal binding sites. |
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Keywords: | aptamers biosensors calcium DNA DNAzymes |
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