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Methods. 2013 Dec 15;64(3):212-7. doi: 10.1016/j.ymeth.2013.07.021. Epub 2013 Jul 19.

A parallel G-quadruplex-selective luminescent probe for the detection of nanomolar calcium(II) ion.

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Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.


A parallel G-quadruplex-selective iridium(III) complex has been synthesized and employed as a luminescent probe in a label-free G-quadruplex-based detection assay for Ca(2+) ions in aqueous solution. In this assay, a guanine-rich oligonucleotide (G4, 5'-G4T4G4-3') initially exists in an antiparallel G-quadruplex conformation, resulting in a low luminescence signal. Upon incubation with Ca(2+) ions, the antiparallel G-quadruplex is induced into a parallel G-quadruplex conformation, which greatly enhances the luminescence emission of the iridium(III) probe. This method was highly sensitive for Ca(2+) ions with a limit of detection in the nanomolar range, and was selective for Ca(2+) over other metal ions.


Ca(2+) ions; G-quadruplex; Iridium; Luminescence; Metal complex; calf-thymus DNA; ctDNA; double-stranded DNA; dsDNA; single-stranded DNA; ssDNA

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