Development of a Whole-Cell Biocatalyst/Biosensor by Display of Multiple Heterologous Proteins on the Escherichia coli Cell Surface for the Detoxification and Detection of Organophosphates

This paper reports the codisplay of organophosphorus hydrolase (OPH) and methyl parathion hydrolase (MPH)–green fluorescent protein (GFP) fusion on the cell surface of Escherichia coli using the truncated ice nucleation protein (INPNC) and Lpp–OmpA as the anchoring motifs. The surface localization of both OPH and MPH–GFP was demonstrated by cell fractionation, Western blot analysis, protease accessibility experiment, and immunofluorescence microscopy. Anchorage of the foreign proteins on the outer membrane neither inhibits cell growth nor affects cell viability. The recombinant strain can be used as a whole-cell biocatalyst and showed a broader substrate range than strains expressing either OPH or MPH. A mixture of six organophosphorus pesticides (OPs) (0.2 mM each) could be degraded completely within 5 h. The broader substrate specificity in combination with the rapid degradation rate makes the recombinant strain a promising candidate for detoxification of OPs. The fluorescence of surface-displayed GFP is very sensitive to environmental pH change. Because hydrolysis of OPs by OPH or MPH generates protons, the recombinant <i>E. coli</i> could be used as a whole-cell biosensor for the rapid detection of OPs by evaluating fluorescence changes as a function of OP concentrations

Carbon Quantum Dot/NiFe Layered Double-Hydroxide Composite as a Highly Efficient Electrocatalyst for Water Oxidation

The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction is crucial to a variety of important energy conversion and storage processes. Here, we use carbon quantum dots (CQDs, ∼5 nm) to form hybrids with the ultrathin nickel–iron layered double-hydroxide (NiFe-LDH) nanoplates. The resulting CQD/NiFe-LDH complex exhibits high electrocatalytic activity (with an overpotential of ∼235 mV in 1 M KOH at a current density of 10 mA cm^–2) and stability for oxygen evolution, which almost exceed the values of all previously reported Ni-Fe compounds and were comparable to those of the most active perovskite-based catalyst

Metabolic Engineering of Pseudomonas putida KT2440 for Complete Mineralization of Methyl Parathion and γ‑Hexachlorocyclohexane

Agricultural soils are often cocontaminated with multiple pesticides. Unfortunately, microorganisms isolated from natural environments do not possess the ability to simultaneously degrade different classes of pesticides. Currently, we can use the approaches of synthetic biology to create a strain endowed with various catabolic pathways that do not exist in a natural microorganism. Here, we describe the metabolic engineering of a biosafety Pseudomonas putida strain KT2440 for complete mineralization of methyl parathion (MP) and γ-hexachlorocyclohexane (γ-HCH) by functional assembly of the MP and γ-HCH mineralization pathways. The engineered strain was genetically stable, and no growth inhibition was observed. Such a strain not only would reduce the toxicity of MP and γ-HCH but also would prevent the accumulation of potentially toxic intermediates in the environment. Furthermore, expression of <i>Vitreoscilla</i> hemoglobin improved the ability of the engineered strain to sequester O₂. The inoculation of the engineered strain to soils treated with MP and γ-HCH resulted in a higher degradation rate than in noninoculated soils. Moreover, introduced GFP may be used to monitor the activity of the engineered strain during bioremediation. The engineered strain may be a promising candidate for <i>in situ</i> bioremediation of soil cocontaminated with MP and γ-HCH

Metal Nanoparticle/Carbon Quantum Dot Composite as a Photocatalyst for High-Efficiency Cyclohexane Oxidation

High-efficiency and high-selectivity catalytic oxidation of alkanes under mild conditions is a major objective of current catalysis chemistry and chemical production. Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes still suffer from low conversion, poor selectivity, and excessive production of waste. We demonstrate the design and synthesis of composites made from metal nanoparticles and carbon quantum dots (CQDs) for high-efficiency and high-selectivity photocatalyst systems for the green oxidation of cyclohexane. Remarkably, the present Au nanoparticles/CQDs composite photocatalyst yields 63.8% conversion efficiency and 99.9% selectivity for the green oxidation of cyclohexane to cyclohexanone, using H₂O₂ under visible light at room temperature. Given its diversity and versatility of structural and composition design, metal nanoparticles/CQDs composites may provide a powerful pathway for the development of high-performance catalysts and production processes for green chemical industry

Tunable Metal/Silicon Hybrid Dots Catalysts for Hydrocarbon Selective Oxidation

Metal (Au, Ag, and Pt)/silicon hybrid dots were facially prepared by a one-step reaction between Si quantum dots (SiQDs) and metal salts at room temperature without any templates and surfactants. The obtained Au/SiQDs were demonstrated to be a superior catalyst for selective oxidation of cyclohexene. By altering the composition of Au/SiQDs catalysts, the selectivity of main products can be tuned step-by-step

MOESM1 of Discovery of new cellulases from the metagenome by a metagenomics-guided strategy

Additional file 1: Figure S1. The nucleotide sequences of 23 glycoside hydrolases. Three target sequences selected in this study are colored in red. Figure S2. Resistance of the recombinant cel7482 to high concentrations of ILs. The recombinant cel7482 was incubated with CMC at 37 °C for 30 min in 50 mM citrate–phosphate buffer (pH 7.0) supplemented with 20 % of [Emim]Cl, [Bmim]Cl or [Amim]Cl. The activity in reaction without ILs was set as 100 %. Figure S3. Alignment of cel7482 and cel3623 proteins. The amino acid sequences of cel7482 and cel3623 were aligned with ClustalX2.0.12. The identity or similarity of the residues is represented by (*), (:), and (.). The residues in the active site are colored in red. The different residues in the entryway of active site between cel7482 and cel3623 are colored in green and underline. Figure S4. Alignment of cel36 and 3PZT proteins. The amino acid sequences of cel36 and 3PZT were aligned with ClustalX2.0.12. The identity or similarity of the residues is represented by (*), (:), and (.). The residues in the active site are colored in red

Representative immunohistochemical staining of <i>Sohlh1</i> and <i>Sohlh2</i> in brain cortex (A-C).

<p>Arrows show positive cells and arrows in different color indicate different cell types. Bars indicate 20μm.</p

Representative immunohistochemical staining of <i>Sohlh1</i> and <i>Sohlh2</i> in epithelia of respiratory and digestive system (A-H).

<p>A and B show <i>Sohlh1</i> and <i>Sohlh2</i> expressions in esophagus epithelia respectively. C and D show <i>Sohlh1</i> and <i>Sohlh</i>2 expressions in alveolar cells respectively. E and F show <i>Sohlh1</i> and <i>Sohlh</i>2 expressions in liver respectively. G and H show <i>Sohlh1</i> and <i>Sohlh</i>2 expressions in pancreas. Arrows show positive cells and arrows in different color indicate different cell types. Bars indicate 20μm.</p

A Safe and Facile Route to Imidazole-1-sulfonyl Azide as a Diazotransfer Reagent

A facile approach to the diazotransfer reagent of imidazole-1-sulfonyl azide was reported. The procedure was well optimized to clarify potential explosion risks. A high production yield as well as small batch variation was achieved even without careful pretreatment of reagents and solvents. HPLC and NMR methods to monitor the process were provided. These features made this protocol suitable for large scale preparation in academia and industry as well

Optimized Ratiometric Fluorescent Probes by Peptide Self-Assembly

We report in this study on optimized ratiometric fluorescent probes by peptide self-assembly. The resulting self-assembled nanoprobes show extraordinary stability in aqueous solutions and extremely low background fluorescence in buffer solutions. Our optimized probes with much bigger ratiometric fluorescence ratios also show an enhanced cellular uptake, lower background noise, and much brighter fluorescence signal in the cell experiment. Our study provides a versatile and very useful strategy to design and produce fluorescent probes with better performance