基于T-Hg^(2+)-T结构的非标记共振光散射法检测汞离子

Label-Free Resonance Light Scattering Detection of Hg^(2+) Based on Specific Structure Thymine-Hg^(2+)-Thymine

根据目标物诱导核酸分子构象发生变化,导致体系共振光散射强度增大的原理建立了检测Hg^(2+)的新方法。当溶液中有Hg^(2+)存在时,基于"T-Hg^(2+)-T"特异性结合作用,促使Hg^(2+)特异核酸探针的构象发生变化,由单链状态变为刚性双链结构,使体系共振光散射强度增大。在波长566nm处,当汞离子浓度在7.2×10^(-9)~9×10^(-8)mol·L^(-1)范围内时,体系的共振光散射增强程度ΔI与汞离子的浓度(c)具有良好的线性关系。其线性方程为ΔI=5.12c+3.55(r=0.999 5)。将该方法用于环境水样中汞离子的测定,相对标准偏差(RSD)小于1.9%;样品加标回收率为99.4%~104.3%。该方法以Hg^(2+)的高度特异性核酸探针作为识别元件,通过控制Hg^(2+)浓度的变化调节共振光散射强度的变化,将Hg^(2+)的检测转化为对DNA分子构象变化的检测,该转化有利于增强体系共振光散射强度,提高方法灵敏度,该共振光散射检测方法能检测到浓度为2.16×10^(-9)mol·L^(-1)的Hg^(2+)。同时,由于"T-T"错配碱基对对Hg^(2+)的特异结合能力,显著提高了该分析方法对Hg^(2+)的选择性。另外,该方法操作简便、不需标记。

A new label-free resonance light scattering method for the highly selective and sensitive detection of mercury ion was designed. This strategy makes use of the target-induced DNA eonformational change to enhance the resonance light scattering intensity leading to an amplified optical signal. The Hg^2＋ ion, which possesses a unique property to bind specifically to two DNA thymine （T） bases, in the presence of Hg^2＋ , the specific oligonueleotide probes form a conforrnational reorganization of the oligonucleotide probes from single-chain structure to duplex-like complexes, which can greatly enhance the resonance light scattering intensity. Under the optimum experimental conditions, the enhanced resonance light scattering intensity at 566 nm was in proportion of mercury ion concentration in the range 7. 2 × 10^-9 -9 × 10^-8mol · L^-1 with the linear regression equation was △I= 5. 12cq-3.55（r=0. 999 5）. This method was successfully applied to detection of Hg2＋ in enviro nmental water samples, the RSD were less than 1.9M and recoveries were 99. 4-104. 3%. This label-free strategy uses the mercury specific oligonucleotide probes as recognition elements and control the strength or resonance light scattering by changing the concentration of Hg^2＋. It translating the small molecule detection into the DNA hybridization behavior leading to an amplified resonance light scattering signal can well enhance the sensitive detection of Hg^2＋. With amplification by DNA hybridization behavior, the sensitivity for the detection of Hg^2＋ can achieve 2.16 × 10^-9 mol ·-1 Lt. In this study, the stacked T-Hg^2＋ -Tfunctioned not only as amplification property but also as an selective recognition. The highly specific detection of Hg^2＋ is attributed to the formation of a stable T-Hg^2＋-T complex.