An anti-passivation ink for the preparation of electrodes for use in electrochemical immunoassays / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

p-Nitrophenylphosphate (PNPP) is usually employed as the substrate for enzyme-linked immunosorbent assays. p-Nitrophenol (PNP), the product of PNPP, with the catalyst alkaline phosphatase (ALP), will passivate an electrode, which limits applications in electrochemical analysis. A novel anti-passivation ink used in the preparation of a graphene/ionic liquid/chitosan composited (rGO/IL/Chi) electrode is proposed to solve the problem. The anti-passivation electrode was fabricated by directly writing the graphene-ionic liquid-chitosan composite on a single-side conductive gold strip. A glassy carbon electrode, a screen-printed electrode, and a graphene-chitosan composite-modified screen-printed electrode were investigated for comparison. Scanning electron microscopy was used to characterize the surface structure of the four different electrodes and cyclic voltammetry was carried out to compare their performance. The results showed that the rGO/IL/Chi electrode had the best performance according to its low peak potential and large peak current. Amperometric responses of the different electrodes to PNP proved that only the rGO/IL/Chi electrode was capable of anti-passivation. The detection of cardiac troponin I was used as a test example for electrochemical immunoassay. Differential pulse voltammetry was performed to detect cardiac troponin I and obtain a calibration curve. The limit of detection was 0.05 ng/ml.

In vivo assay to identify bacteria with ß-glucosidase activity

Background: ß-Glucosidase assay is performed with purified or semipurified enzymes extracted from cell lysis. However, in screening studies, to find bacteria with ß-glucosidase activity among many tested bacteria, a fast method without cell lysis is desirable. In that objective, we report an in vivo ß-glucosidase assay as a fast method to find a ß-glucosidase producer strain. Results: The method consists in growing the strains for testing in a medium supplemented with the artificial substrate p-nitrophenyl-ß-glucopyranoside (pNPG). The presence of ß-glucosidases converts the substrate to p-nitrophenol (pNP), a molecule that can be easily measured in the supernatant spectrophotometrically at 405 nm. The assay was evaluated using two Bifidobacterium strains: Bifidobacterium longum B7254 strain that lacks ß-glucosidase activity and Bifidobacterium pseudocatenulatum B7003 strain that shows ß-glucosidase activity. The addition of sodium carbonate during pNP measurement increases the sensitivity of pNP detection and avoids the masking of absorbance by the culture medium. Furthermore, we show that pNP is a stable enzymatic product, not metabolized by bacteria, but with an inhibitory effect on cell growth. The ß-glucosidase activity was measured as units of enzyme per gram per minute per dry cell weight. This method also allowed the identification of Lactobacillus strains with higher ß-glucosidase activity among several lactobacillus species. Conclusion: This in vivo ß-glucosidase assay can be used as an enzymatic test on living cells without cell disruption. The method is simple, quantitative, and recommended, especially in studies screening for bacteria not only with ß-glucosidase activity but also with high ß-glucosidase activity.

β-Cyclodextrin-cross-linked Polymer Coupled Ultraviolet-Visble Spectrophotometry for Separation and Analysis of p-Nitrophenol / 分析化学

The β-cyclodextrin cross-linked polymer(β-CDCP) was used as adsorbent to pre-concentrate/separate the trace p-nitrophenol and then the determination was carried by UV-Vis spectrophotometry. Under alkaline condition,the adsorption/elution behavior of p-nitrophenol was studied. In 0. 02 mol/L NaOH solution and at room temperature for 30 min,the resin could separate and pre-concentrate the p-nitrophenol effectively. Methanol solution(1:1,V/V) was used as eluent and the β-CDCP could be used repeatedly. The linear range and detection limit was 0.5 -90.0 mg/L and 3. 10 μg/L,respectively. The proposed method has been used to determine the p-nitrophenol in synthesized sample with satisfactory results.

Effects of Multiple Exposures to Pesticides on Plasma Cholinesterase Activity and p-nitrophenol Excretion in Rats / 예방의학회지

The effects of multiple exposures to pesticides on plasma cholinesterase(ChE) activities and urinary p-nitrophenol excretion were evaluated in rats. Rats were received single dose i.p. with LD50/100(mg/kg) of organophosphorous(OP), organophosphorous-organochroline(OP-OC), organophosphorous-carbamate(OP-CAB), organophosphorous-organoarsenate(OP-OA) pesticides for 4 consecutive days. In repeated administration of pesticides, plasma ChE activities were decreased, but urinary p-nitrophenol were increased after the first injection and then decreased gradually. The recovery rates of ChE activities and p-nitrophenol excretion at 48 hours after the fourth infection were delayed in comparison with the baseline value of 24 hours before the first injection. Statistical significances were found between OP and other groups except OP-OA group after the second injection in plasma ChE activities, but in urinary p-nitrophenol excretion there was statistical significance only between OP and OP-CAB.

Effect of p-nitrophenol Shock on Sludge Activity and Microbial Populations and in UASB Reactor / 微生物学通报

Effect of p-nitrophenol shock on microbial populations and sludge activity in UASB reactor was studied by DGGE-PCR of 16S rDNA fragments and detection of COD removing and biogas yield.The results showed that p-nitrophenol seriously inhibited the sludge activity,resulting in the drop of biogas and COD removing rate.The 40mg/L p-nitrophenol had more inhibition than 20mg/L p-nitrophenol.It would take 27 and 16 days respectively for reactor to recover after 40mg/L and 20mg/L p-nitrophenol shock.The diversity of eubacteria and methanogens were also effected by the p-nitrophenol shock.The variation of eubacteria was more than that of methanogens after p-nitrophenol shock.The drop of biogas was mainly related to the variation of Methanosaeta sp.and Methanomicrobia sp.after p-nitrophenol shock.Among the eubacteria the population of Chloroflexi sp.、Bacteroide sp.and Anaerovibrio sp.decreased greatly after p-nitrophenol shock.And more,the Rheinheimera sp disappeared after 40mg/L p-NP treatment.But the Flavobacteria sp.appeared after p-nitrophenol shock,which was probably related to the degradation of p-NP.

Isolation and Characterization of a Temperature-sensitive p-Nitrophenol Degradation Related Genes Mutant Strain / 微生物学通报

A temperature-sensitive mutant strain was isolated after transposon mutagenesis with Tn5 and named MT54.PCR was carried out with primers designed according to the sequence of transposon,the PCR products showed that the MT54 carried transposon in the genome. The mutant grew well at 30℃in minimal medium(MM)containing p-nitrophenol(PNP)as sole carbon source,while it cannot grow at 37℃in the same medium,NO_2.detection results also proved that.Comparing the degradation rate of PNP and hydroquinone of MT54 and DLL-E4 at different temperature,it was speculated that the mutant site locate in the PNP degradation related genes.