Desulfurization Activated Phosphorothioate DNAzyme for the Detection of Thallium

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• 作者：Po-Jung Jimmy Huang ; Mahsa Vazin ; Juewen Liu
• 刊名：Analytical Chemistry
• 出版年：2015
• 出版时间：October 20, 2015
• 年：2015
• 卷：87
• 期：20
• 页码：10443-10449
• 全文大小：522K
• ISSN：1520-6882

文摘

Thallium (Tl) is a highly toxic heavy metal situated between mercury and lead in the periodic table. While its neighbors have been thoroughly studied for DNA-based sensing, little is known about thallium detection. In this work, in vitro selection of RNA-cleaving DNAzymes is carried out using Tl³⁺ as the target metal cofactor. Both normal DNA and phosphorothioate (PS)-modified DNA are tested for this purpose. While no Tl³⁺-dependent DNAzymes are obtained, a DNA oligonucleotide containing a single PS-modified RNA nucleotide is found to cleave by 鈭?% by Tl³⁺ at the RNA position. The remaining 93% are desulfurized. By hybridization of this PS-modified oligonucleotide with the Tm7 DNAzyme, the cleavage yield increases to 鈭?0% in the presence of Tl³⁺ and Er³⁺. Tm7 is an Er³⁺-dependent RNA-cleaving DNAzyme. It cleaves only the normal substrate but is completely inactive using the PS-modified substrate. Tl³⁺ desulfurizes the PS substrate to the normal substrate to be cleaved by Tm7 and Er³⁺. This system is engineered into a catalytic beacon for Tl³⁺ with a detection limit of 1.5 nM, which is below its maximal contamination limit defined by the U.S. Environmental Protection Agency (10 nM).