Development of a catalase based biosensor for alcohol determination in beer samples

An amperometric biosensor based on catalase enzyme for alcohol determination was developed. To construct the biosensor catalase was immobilized by using gelatin and glutaraldehyde on a Clark type dissolved oxygen (DO) probe covered with a teflon membrane which is sensitive for oxygen. The working principle of the biosensor depends on two reactions, which one is related to another, catalyzed by catalase enzyme. In the first reaction catalase catalyzes the degradation of hydrogen peroxide and oxygen is produced and also a steady-state DO concentration occurs in a few minutes. When ethanol added to the medium catalase catalyzes the degradation of both hydrogen peroxide and ethanol and this results in a new steady-state DO concentration. Difference for first and the last steady-state DO concentration occurred in the interval surface of DO probe membrane, which related to ethanol concentration, are detected by the biosensor. The biosensor response depends linearly on ethanol concentration between 0.05 and 1.0 mM with a detection limit of 0.05 mM and a response time of 3 min. In the optimization studies of the biosensor phosphate buffer (pH 7.0; 50 mM) and 35 °C were established as providing the optimum working conditions. In the characterization studies of the biosensor some parameters such as reproducibility, substrate specificity, operational and storage stability were carried out. Finally, by using the biosensor developed and enzimatic-spectrophotometric method alcohol concentration of some alcoholic drinks were determined and results were compared.     

Uranyl ion uptake capacity of poly (N-isopropylacrylamide/maleic acid) copolymeric hydrogels prepared by gamma rays

The effect of gel composition, absorbed dose and pH of the solution on the uranyl ion uptake capacity of N-isopropylacrylamide/maleic acid copolymeric hydrogels containing 0–3 mol% of maleic acid at 48 kGy have been investigated. Uranyl uptake capacity of hydrogels are found to increase from 18.5 to 94.8 mg [UO₂²⁺]/g dry gel as the mole % of maleic acid content in the gel structure increased from 0 to 3. The percent swelling, equilibrium swelling and diffusion coefficient values have been evaluated for poly(N-isopropylacrylamide/maleic acid) hydrogels at 500 ppm of uranyl nitrate solution.     

硼氢化钠还原樟脑制备异冰片——国外本科生实验的介绍与讨论

冰片作为一种自然界广泛存在的次级代谢产物,可以通过樟脑的还原反应制备。但由于冰片极易氧化为樟脑,实验室中常使用硼氢化钠还原樟脑制备冰片的方法。该法可能生成2种冰片异构体,可以通过动力学控制获得其中一个异冰片从而使其成为不可逆反应。该有机化学实验设计在美国与欧洲国家均有涉及,但在国内教材中只是单纯设计为环己酮等单分子的还原反应,缺乏体现化学在解决实际问题中的实用性以及课堂的趣味性。该实验的引进不失为改进国内有机化学实验设计的良好素材。     

Preparation of poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes and their application in wastewater treatment

In this study, new poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes were prepared firstly and then characterized. Then they were used in the removal of Fe(III) and Co(II) ions from wastewater with a stirred ultrafiltration cell. Also, alginic acid polymer was used as complexing agent to enhance the retention. In the filtration of Fe(III) and Co(II) solutions, the effects of pH, concentration of solutions, and pressure on the retention percentage were examined. Aqueous solutions of Fe(III) and Co(II) were filtrated at the stirred velocity of 400?rpm. The maximum retention percentage was found as 78.66% for Fe(III) solution at the pH of 3.3, concentration of 0.3?×?10^?4 M Fe(III) solution, pressure of 40?psi by using 2.5 (w/v)% Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes. For Co(II) solutions the maximum retention percentage was found as 77% at the pH of 6, concentration of 0.3?×?10^?4 M Co(II) solution, pressure of 50?psi by using 2.5 (w/v)%Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes.     

Correlative Cellular Mass Spectrometry Imaging and Amperometry Show Dose Dependent Changes in Lipid Composition and Exocytosis

Aberrant functioning of the proteasome has been associated with crucial pathologic conditions including neurodegeneration. Yet, the complex underlying causes at the cellular level remain unclear and there are conflicting reports of neuroprotective to neurodegenerative effects of proteasomal inhibitors such as lactacystin that are utilised as models for neurodegenerative diseases. The conflicting results may be associated with different dose regimes of lactacystin and hence we have performed a dose dependent study of the effects of lactacystin to identify concurrent changes in the cell membrane lipid profile and the dynamics of exocytosis using a combination of surface sensitive mass spectrometry and single cell amperometry. Significant changes of negatively charged lipids were associated with different lactacystin doses that showed a weak correlation with exocytosis while changes in PE and PE−O lipids showed dose dependent changes correlated with initial pore formation and total release of vesicle content respectively.