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Some G-quadruplex-hemin complexes can be used as a type of DNAzymes with peroxidase activity, it can efficiently catalyze H2O2-mediated oxidation reactions. Herein, a simple, colorimetric, and homogenous sensor design strategy based on G-quadruplex-hemin DNAzymes was developed. This strategy takes advantages of the competition between a DNA/DNA duplex and a DNA/target complex, and the formation of catalytically active G-quadruplexes in the presence of targets. With this method, no labeled oligonucleotides are needed, and no expensive instruments are required. This strategy may be developed as a general approach for the analysis of many metal ions and aptamer substrates. In this paper, the feasibility of this strategy in Hg2+ and adenosine triphosphate (ATP) detection was studied, and results showed that this “turn-on” process enabled the selective detection of aqueous Hg2+ and adenosine triphosphate (ATP) using a simple colorimetric technique.

Some transition metals–sodium dodecyl sulphate (M–SDS) complexes are used to mimic the active group of peroxidase. The catalytic characteristics of these mimic‐enzymes in the oxidation reaction of fluorescence substrate, pyronine B (PB), with hydrogen peroxide have been studied. Though the catalytic activities of M–SDS complexes are much lower than horseradish peroxidase (HRP), they can catalyze the oxidation reaction of PB with hydrogen peroxide leading to fluorescence quenching of PB. Mo(VI)–SDS complex exhibited the highest catalytic activity among same type mimic enzymes. Under optimum conditions, linear relationship between fluorescence quenching F 0/F and concentration of H2O2 is in the range of 0.0–8.6 × 10−7 M. By coupling this mimic catalytic reaction with the glucose oxidase, glucose can be detected. Linear relationship between F 0/F and concentration of glucose is in the range of 0.0–1.4 × 10−7 M. The method has been applied to the determination of glucose in human serum and the result...

Based on a detailed study of the interaction of toluidine blue (TB) with nucleic acids, a novel resonance light scattering (RLS) method was developed for the determination of nucleic acids. The RLS intensity of TB at 400 nm was greatly enhanced in the presence of nucleic acids at pH 3.17. Linear relationships between the enhanced RLS intensity and the concentration of nucleic acids were observed in the range of 0.0–2.7 µg cm−3 for calf thymus DNA (ctDNA), 0.0–2.2 µg cm−3 for fish sperm DNA (fsDNA), and 0.0–0.5 µg cm−3 for yeast RNA (yRNA), respectively. The limits of detection (3σ) were determined to be 24.0 ng cm−3 for ctDNA, 22.7 ng cm−3 for fsDNA and 5.1 ng cm−3 for yRNA. The binding constants were evaluated to be 1.1 × 104 dm3 mol−1 for ctDNA, 1.8 × 104 dm3 mol−1 for fsDNA, and 1.7 × 104 dm3 mol−1 for yRNA. The maximum binding numbers (n) were 2.7, 5.5, and 15.0 for ctDNA, fsDNA and yRNA, respectively. The proposed method was applied for determination of the nucleic acids in chicken blood. Th...

This paper reports a novel and biological compatible biosensor that was used to study the electrochemical behavior of horseradish peroxidase (HRP) incorporated in salt bridge-supported bilayer lipid membrane (Sb-BLM). The incorporation of HRP was achieved by electrostatic interaction between HRP and LA anion sites pre-incorporated in Sb-BLM, which result in the enhancement of the electron exchange between the protein and the electrode surface. A quasi-reversible electron transfer of HRP was observed even in the absence of mediators. The electrocatalytically kinetic behavior of HRP and the electrode-kinetic process were investigated with this biosensor. In the presence of hydrogen peroxide, the electrocatalytical activity of HRP was determined.

Potentiometric behaviors of a salt-bridge supported bilayer lipid membrane (Sb-BLM) modified with Calix[n]arene (n=4, 6, 8) derivatives are described for some alkali metal ions. The modified Sb-BLM was used as an alkali cation sensor. The membrane potentials were observed to generate Nernstian responses to the concentration of alkali metal ions in electrolyte. The Sb-BLM modified with the calix[n]arenes show high selectivity for individual alkali metal ions: Calix[8]arenes for K+, calix[6]arenes for Cs+ Calix[4]arenes show no selectivity for any alkali ions. The interacting mechanism is also discussed.

β-Cyclodextrin polymer (β-CDP) adsorbed resin phase spectrophotometry with 1- (2-pyridylazo) -2-naphthol (PAN) has been developed for determination of copper at the μg level in soybean and human hair. Cobalt, nickel, zinc and manganese, which form colored species with PAN in the resin phase, can be completely masked with a solution composed of phenanthroline (2.78×10−5 mol/1) and sodium hexametaphosphate (3.27×10−3 mol/1). To whom correspondence should be addressed.