The Application Of Nucleic Acid Probes For Mercuric Ions Detection

Mercury is an important of metal elements and a kind of important environmental pollutants.Therefore,a high sensitive and high selective method used in the detection of mercury ion in environmental and food has very important significance.In the research of this paper,we developed the following two nucleic acid probes to detect mercury ions and biothiols:We devised a DNA three way junction?3WJ?probe for specific detection of Hg²⁺and biothiols-The 3WJ molecular device is composed of three single-stranded DNA?ssDNA?molecules,SS and QS have a 3' BHQ1?black hold quencher 1?and a 5'HEX?hexachlorofluorescein?label at the end respectively,AS without any label.The SS and the AS single-strand DNA are T-rich sequences.In the absence of Hg²⁺,this 3WJ adopts a reasonably well defined global structure with three helical arms.While in the presence of Hg²⁺,the metal ions can diffuse into the cavity and mediate T-Hg²⁺-T base pairing.This propensity leads to the reformation of the global structure at desirable temperatures,at which SS and AS are doublestranded and QS is hence"pushed out".Consequently,the HEX dye is free from quenching,and a "turn-on"fluorescence can be obtained.The approach is sensitive and the limit of detection?LOD?is 3 nM.This method is further exploited for detection of glutathione and cysteine.The detection range is 20 nM-400 nM.This proposed method is highly selective,wide detection range,specificity,simple and easy to operate.A simple method was developed,based on the inherent of G-quadruplex and fidelity of the"thymine-Hg²⁺-thymine"binding motif.A G-rich sequence was named as HT-DNA,a T-rich sequence was named as RHT-DNA.In the absence of Hg²⁺,HT-DNA can form G-quadruplex structure.HT-DNA and RHT-DNA are not paired into double stranded DNA by the principle of complementary base pairing.In the-presence of Hg²⁺,HT-DNA and RHT-DNA can pair into double stranded DNA through "thymine-Hg²⁺-thymine",lead to G-quadruplex structure can not be formed.This sensor can recorded by fluorescent spectrophotometer and ultraviolet spectrophotometer,based on the characteristics of G-quadruplex.The detection limit of fluorescence analysis and ultraviolet analysis approach can achieve 17.2 nM and 15nM,respectively.The novel method needs no modification of DNA,simple design and highly selective,identificate by naked eye.