Characterization of a DNA-hydrolyzing DNAzyme for generation of PCR strands of unequal length

Advances in the Functional Nucleic Acid Biosensors for Detection of Lead Ions

Lead ions (Pb²⁺) are destructive to the natural environment and public health, so the efficient detection of Pb²⁺ is particularly important. Although the instrumental analysis methods have high accuracy, they require high cost and precise operation, which limits their wide application. Therefore, many strategies have been extensively studied for detecting Pb²⁺ by biosensors. Functional nucleic acids have become an efficient tool in this field. This review focuses on the recent biosensors of detecting Pb²⁺ based on functional nucleic acids from 2010 to 2020, in which DNAzyme, DNA G-quadruplex and aptamer will be introduced. The biosensors are divided into three categories that colorimetric, fluorometric and electrochemical biosensors according to the different reported signals. The action mechanism and detection effect of each biosensor are explained. Finally, the present situation of nucleic acid biosensor for the detection of Pb²⁺ is summarized and the future research direction is prospected.

Insight into an Oxidative DNA-Cleaving DNAzyme: Multiple Cofactors, the Catalytic Core Map and a Highly Efficient Variant

An oxidative DNA-cleaving DNAzyme (PL) employs a double-cofactor model “X/Cu²⁺” for catalysis. Herein, we verified that reduced nicotinamide adenine dinucleotide (NADH), flavin mononucleotide, cysteine, dithiothreitol, catechol, resorcinol, hydroquinone, phloroglucinol, o-phenylenediamine, 3,3′,5,5'-tetramethylbenzidine, and hydroxylamine acted as cofactor X. According to their structural similarities or fluorescence property, we further confirmed that reduced nicotinamide adenine dinucleotide phosphate (NADPH), 2-mercaptoethanol, dopamine, chlorogenic acid, resveratrol, and 5-carboxyfluorescein also functioned as cofactor X. Superoxide anions might be the commonality behind these cofactors. We subsequently determined the conservative change of individual nucleotides in the catalytic core under four different cofactor X. The nucleotides A4 and C5 are highly conserved, whereas the conservative levels of other nucleotides are dependent on the types of cofactor X. Moreover, we observed that the minor change in the PL's secondary structure affects electrophoretic mobility. Finally, we characterized a highly efficient variant T3G and converted its double-cofactor NADH/Cu²⁺ to sole-cofactor NADH.

•

An oxidative cleavage DNAzyme works with various cofactor X

•

Catalytic nucleotide conservation fluctuates with different cofactor X

•

The PL DNAzyme's minor secondary structure change affects electrophoretic mobility

•

Double-cofactor model of the variant T3G can be converted to sole-cofactor model