title: An Exceptionally Selective DNA Cooperatively Binding Two Ca2+Ions.
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.
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: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Runjhun
authors.initials: R
authors.lastname: Saran
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Po-Jung Jimmy
authors.initials: PJ
authors.lastname: Huang
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.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Juewen
authors.identifier: 0000-0001-5918-9336
authors.initials: J
authors.lastname: Liu
mesh_terms: D001665:Binding Sites; D015374:Biosensing Techniques; D002118:Calcium / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*; D002623:Chemistry Techniques, Analytical / Q000379:methods* / Q000592:standards; D021881:DNA, Catalytic / Q000737:chemistry / Q000378:metabolism*; D007477:Ions / Q000378:metabolism; D057230:Limit of Detection; D014867:Water / Q000737:chemistry
chemical_list: D021881:DNA, Catalytic; D007477:Ions; D014867:Water; D002118:Calcium
keywords: DNA; DNAzymes; aptamers; biosensors; calcium