Semi-rational engineering of a novel halohydrin dehalogenase from Sneathiella limimaris for the enantioselective synthesis of (S)-5-phenoxymethyl-2-oxazolidinone.

Enantiomerically pure 2-oxazolidinones are widely used as chiral auxiliaries in organic synthesis, but there is an unmet need for more effective methods to access these compounds. Here we report the identification and semi-rational engineering of the halohydrin dehalogenase SlHHDH from Sneathiella limimaris for the highly enantioselective ring-opening of phenyl glycidyl ether (PGE) with cyanate to yield (S)-5-phenoxymethyl-2-oxazolidinone. After single and combinatorial mutagenesis, the best enantioselective triple mutant, F15W/A137T/N179L achieved an enantioselectivity of 97 %, with an E value of 154.

Fluorescence/colorimetric dual-signal sensor based on carbon dots and gold nanoparticles for visual quantification of Cr.

A convenient and sensitive dual-signal visualization method is constructed for detection of trivalent chromium ions (Cr) based on fluorescent carbon dots (CDs) and glutathione-modified gold nanoparticles (GSH-Au NPs). The fluorescence of CDs can be quenched by GSH-Au NPs due to the inner filter effect. Cr induces aggregation of GSH-Au NPs because of the coordination with GSH on the surface of Au NPs, leading to the red shift of surface plasmon resonance absorption of Au NPs that provides a "turn-on" fluorescence and colorimetric assay for Cr.

Integrating carbon dots and gold/silver core-shell nanoparticles to achieve sensitive detection of dopamine with fluorometric/colorimetric dual signal.

Dopamine (DA) is a potent neuromodulator in the brain that affects a wide range of motivated behaviors. Abnormal concentration of DA is related to a variety of diseases. Hence, it is imperative to establish a rapid and precise method for quantifying DA.

Proteomics reveals surface electrical property-dependent toxic mechanisms of silver nanoparticles in Chlorella vulgaris.

Silver nanoparticles (AgNPs) are known to exert adverse effects on both humans and aquatic organisms; however, the toxic mechanisms underlying these effects remain unclear. In this study, we investigated the toxic mechanisms of various AgNPs with different surface electrical properties in the freshwater algae Chlorella vulgaris using an advanced proteomics approach with Data-Independent Acquisition. Citrate-coated AgNPs (Cit-AgNPs) and polyethyleneimine-coated AgNPs (PEI-AgNPs) were selected as representatives of negatively and positively charged nanoparticles, respectively.

Surface charge-dependent bioaccumulation dynamics of silver nanoparticles in freshwater algae.

Silver nanoparticles (AgNPs) can gradually accumulate in algae to exert their toxicity; however, there is little knowledge about their bioaccumulation dynamics. For the first time, this study reports the effect of surface charge of AgNPs on their bioaccumulation dynamics in freshwater algae (Chlorella vulgaris) using biodynamic modeling. Polyethylene-coated AgNPs (PEI-AgNPs) and citrate-coated AgNPs (Cit-AgNPs) were selected as positively and negatively charged AgNPs, i.

An immunomagnetic separation and bifunctional Au nanoparticle probe-based multiamplification electrochemical strategy.

A novel electrochemical magnetoimmunosensor for the rapid and sensitive detection of carcinoembryonic antigen (CEA) was fabricated based on a combination of high-efficiency immunomagnetic separation, bifunctional Au-nanoparticle (bi-AuNP) probes, and enzyme catalytic amplification. The reaction carrier magnetic beads (MBs) effectively reduced the toxicity of the complex sample to the working electrode, and the signal carrier bi-AuNP probes loaded a large amount of signal molecules, both of which enhanced the signal-to-noise ratio and further improved the detection sensitivity. A detection limit as low as 0.

Determination of alkaline phosphatase activity and of carcinoembryonic antigen by using a multicolor liquid crystal biosensor based on the controlled growth of silver nanoparticles.

An ultrasensitive liquid crystal biosensor is described for multicolor visualization of the activity of alkaline phosphatase (ALP) based on the controlled growth of silver nanoparticles. The enzymatic product is accumulated on the surface of the LC sensing film by means of silver deposition, and the birefringent signal (observed with a polarizing microscope) is strongly enhanced as a result. The presence of AuNPs also enhances the sensitivity by about 4 orders of magnitude.

Reliable Digital Single Molecule Electrochemistry for Ultrasensitive Alkaline Phosphatase Detection.

Single molecule electrochemistry (SME) has gained much progress in fundamental studies, but it is difficult to use in practice due to its less reliability. We have solved the reliability of single molecule electrochemical detection by integration of digital analysis with efficient signal amplification of enzyme-induced metallization (EIM) together with high-throughput parallelism of microelectrode array (MA), establishing a digital single molecule electrochemical detection method (dSMED). Our dSMED has been successfully used for alkaline phosphatase (ALP) detection in the complex sample of liver cancer cells.

Biometallization-Based Electrochemical Magnetoimmunosensing Strategy for Avian Influenza A (H7N9) Virus Particle Detection.

A highly sensitive electrochemical immunosensor for avian influenza A (H7N9) virus (H7N9 AIV) detection was proposed by using electrochemical magnetoimmunoassay coupled with biometallization and anodic stripping voltammetry. This strategy could accumulate the enzyme-generated product on the surface of the magneto electrode by means of silver deposition, which amplified the detection signal about 80 times. The use of magnetic beads (MBs) and the magneto electrode could also amplify the detection signal.

Bifunctional magnetic nanobeads for sensitive detection of avian influenza A (H7N9) virus based on immunomagnetic separation and enzyme-induced metallization.

Bifunctional magnetic nanobeads (bi-MBs) were fabricated by co-immobilizing target recognition molecules and signal molecules on a magnetic nanobead surface, which were used as both separation and enrichment carriers and signal carriers. The bi-MBs could capture and separate avian influenza A (H7N9) virus (H7N9 AIV) from complex samples efficiently based on the specific reaction between antigen-antibody and their good magnetic response, which simplified sample pretreatment and saved the detection time. Taking advantages of their high surface to volume ratio and rich surface functional groups, multiple alkaline phosphatase (ALP) signal molecules were tethered on the surface of bi-MBs which greatly amplified the detection signal.

Enzyme-induced metallization as a signal amplification strategy for highly sensitive colorimetric detection of avian influenza virus particles.

A novel colorimetric assay method based on enzyme-induced metallization has been proposed for detection of alkaline phosphatase (ALP), and it was further applied to highly sensitive detection of avian influenza virus particles coupled with immunomagnetic separation. The enzyme-induced metallization-based color change strategy combined the amplification of the enzymatic reaction with the unique optical properties of metal nanoparticles (NPs), which could lead to a great enhancement in optical signal. The detection limit for ALP detection was 0.

[Molecular cloning and characterization of a N-acetylneuraminate lyase gene from Staphylococcus hominis].

A N-acetylneuraminate lyase gene (shnal) from Staphylococcus hominis was cloned into pET-28a and expressed in Escherichia coli BL21 (DE3) host cells. The recombinant enzyme was purified and characterized. It is a homotetrameric enzyme with the optimum pH at 8.

Electrochemical magnetoimmunosensing approach for the sensitive detection of H9N2 avian influenza virus particles.

A novel electrochemical magnetoimmunosensor for fast and ultrasensitive detection of H9N2 avian influenza virus particles (H9N2 AIV) was designed based on the combination of high-efficiency immunomagnetic separation, enzyme catalytic amplification, and the biotin-streptavidin system. The reusable, homemade magneto Au electrode (M-AuE) was designed and used for the direct sensing. Immunocomplex-coated magnetic beads (IMBs) were easily accumulated on the surface of the M-AuE to obtain the catalytically reduced electrochemical signal of H2 O2 after the immunoreaction.