ABSTRACT
A simple,fast and highly sensitive fluorescence analysis method for detection of mercury ion was developed based on N-methyl-mesoporphyrin IX (NMM)/G-quadruplex DNA system and specific T-Hg-T mismatches.In this strategy,a large number of thymine was introduced into guanine-rich oigonucleotides which could form G-quadruplex.In the presence of Hg2+,guanine-rich oigonucleotides and complementary strand could form double-stranded DNA molecule by specific T-Hg-T mismatch pair,leading to destruction of G-quadruplex DNA structure.In the absence of Hg2+,guanine-rich oigonucleotides spontaneously formed G-quadruplex DNA structure that could bound NMM to generate intense fluorescence.Based on the above facts,a sensitive fluorescence biosensor for determination of Hg2+ was fabricated.And the optimal conditions for Hg2+ determination were as follows:buffer solution pH of 6.7,20 mmol/L KCl and 2.5 μmol/L NMM in buffer and incubation for 2 h.Under the optimal conditions,the fluorescence intensity signal change (F0-F) and the Hg2+ concentration exhibited a linear correlation within 50 nmol/L to 1000 nmol/L range with a low detection limit of 22.8 nmol/L (3σ).The biosensor exhibited good selectivity toward common metal ions.The developed method was successfully employed to detect Hg2+ in tap water with recovery of 106.1％-107.8％.