A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples.
The novel laccase gene GwLac1 was cloned from Ganoderma weberianum TZC 1 by reverse tran scriptase PCR with degenerate primers on the basis of conserved copper binding regions of known laccases and the rapid amplification of cDNA ends technique. GwLac1 contains 9 introns and its open reading frame is 1566 bp long. The coding domain sequence of GwLac1 was cloned into the vector pPICZB and expressed in Pichia pastoris strain GS115, resulting in the highest yield of laccase, 2.26 U/mL, when the transformants had been cultivated at 20°C for 8 days. The molecular mass of recombinant GwLAC1 was a little more than 50 kDa as estimated by SDS-PAGE and exhibited catalytic properties with 2,2' azino bis(3 ethylbenzothi azoline 6 sulfonic acid) diammonium salt (ABTS) as a substrate. rGwLAC1 was stable at pH of 5.0-7.0 and at temperatures <45°C. The pH and temperature optima and K m of the enzyme for ABTS oxidation were 2.2, 35°C and 85.5 µM, respectively.
The degree of pollution and potential ecological risk of heavy metals (HMs) in the soil of plastic-covered sheds in Jiangxi Province were evaluated by the Nemerow index and potential ecological risk index. The bioconcentration factor and total target hazard quotient (TTHQ) were used to evaluate the enrichment ability and health risk of HMs in vegetables. The mean contents of arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg) and lead (Pb) in soil were 5.99, 0.373, 17.8, 5.94E-02, and 28.9 mg kg–1, respectively; Cd exceeded the background value and the maximum limit. Most soils had no extremely strong ecological risk. The concentration of Pb in root veg-etables was 0.204 mg kg-1, with the highest concentration of Cd (0.147 mg kg–1) in Ganzhou leafy vegetables. The Hg concentration of leafy vegetables in Jiujiang was 1.41E-02 mg kg–1, which exceeded the maximum limit. The bioconcentration factor of HMs was negatively correlated with pH (P ≤ 0.05). The migration ability of Cd in root vegetables was 1.7-fold to that of leafy vegetables, and was strongest. The TTHQ of all vegetables was less than 1.0, which indicated that there was no significant noncarcinogenic risk in adults. The TTHQ of root vegetables was highest, with Pb in vegetables being major health risk factors. In conclusion, fruit and solanaceous vegetables may be more suitable for planting in plastic-covered shed than root and leafy vegetables; Cd and Pb were identified as the priority control metals under plastic-covered sheds in Jiangxi Province.
A facile and selective fluorescence sensor for laccase determination has been proposed depending on the interaction between 3-azidocoumarin and trametes versicolor (Tv) laccase in this paper. The azido group of 3-azidocoumarin that is electron-rich α-nitrogen can directly interact with histidines that coordinate to three copper sites through hydrogen bonds and forms a new complex, which decreases the electron-donating ability of the azido group, leading to enhance the fluorescence intensity of the sensing system. Also, other common proteins have no significant interference for the proposed laccase sensor. Additionally, the proposed fluorescence sensor is extended to demonstrate the conformational flexibility of Tv laccase by the urea denaturant. A good consistency of the results obtained with the presented laccase sensor and CD spectra is performed. Furthermore, the relationship between the catalytic activity and the unfolding percentage of the unfolded Tv laccase through the proposed laccase sensor is also elucidated well.
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