Detection and analysis of Bacillus subtilis growth with piezoelectric quartz crystal impedance based on starch hydrolysis

Study on the enhancement of catalytic activity for hemoglobin by quinhydrone in poly(o-aminophenol) film

Hemoglobin (Hb) and quinhydrone (QHQ) were incorporated in poly(o-aminophenol) [o-AP, POAP] film by electropolymerization of o-aminophenol in a weak acid solution containing Hb and QHQ. The nonconducting polymer film was found to be nearly rigid by piezoelectric quartz crystal (PQC) impedance. Therefore, the thickness of the Hb-QHQ-POAP film was estimated as about 104 +/- 10 nm by quartz crystal microbalance (QCM). The QHQ mediation effects on the biomacromolecule Hb entrapped in the POAP film were investigated by using cyclic voltammetry, amperometric technique and kinetic study. Cyclic voltammograms showed that the redox peaks in the Hb-QHQ-POAP film are much more reversible than those in the Hb-POAP film. The response current of the Hb-QHQ-POAP film to H(2)O(2) was almost twice than that of the Hb-POAP film. The Michaelis-Menten constant and the activation energy of Hb in the Hb-QHQ-POAP film are 7.47 mM and 13.91 kJ/mol, respectively, both are smaller than that in the Hb-POAP film. These results showed that the immobilized Hb in POAP film exhibited higher catalytic activity to H(2)O(2) due to the mediation of QHQ.

Assay and analysis for anti- and pro-oxidative effects of ascorbic acid on DNA with the bulk acoustic wave impedance technique

A bulk acoustic wave (BAW) impedance sensor has been applied for in situ monitoring of the whole process of DNA oxidative damage induced by the vitamin C (Vc)-Fe (III) system, based on its real-time responses to the density-viscosity change of the tested solution due to the damages occurring on the DNA molecules. The results showed that Vc exhibited two conflicting effects, i.e., pro-oxidation and anti-oxidation on the DNA at different Vc concentrations in the damage system, and the "threshold" concentration of Vc for these two effects was estimated to be about 100 micromol/L. The end-point frequency change of the sensor (Deltaf(m)) was found to be linearly related to the initial concentration of the soybean DNA (C(DNA)) in the range of 40-1000 microg/mL, and the exponential relationship between the frequency change (Deltaf(0)) vs damaging time suggested that the Fe (III)-mediated DNA damage by Vc could be described as a first-order kinetics reaction. The effects of variations in concentrations of Vc and Fe3+ on the DNA oxidative damage were discussed, and based on investigations for the enhancing influence of H2O2 and inhibiting influence of HO* scavengers on the DNA damage, the nature and physiological toxicity of the damage in biological system were also examined. In addition, UV-vis spectra and electrophoresis analysis were also used, and the experimental observations were in good agreement with the above results.