Embigin facilitates monocarboxylate transporter 1 localization to the plasma membrane and transition to a decoupling state.

Cell-surface ancillary glycoproteins basigin or embigin form heterodimeric complexes with proton-coupled monocarboxylate transporters (MCTs), facilitating the membrane trafficking of MCTs and regulating their transport activities. Here, we determine the cryoelectron microscopy (cryo-EM) structure of the human MCT1-embigin complex and observe that embigin forms extensive interactions with MCT1 to facilitate its localization to the plasma membrane. In addition, the formation of the heterodimer effectively blocks MCT1 from forming a homodimer through a steric hindrance effect, releasing the coupling between two signature motifs and driving a significant conformation change in transmembrane helix 5 (TM5) of MCTs. Consequently, the substrate-binding pocket alternates between states of homodimeric coupling and heterodimeric decoupling states and exhibits differences in substrate-binding affinity, supporting the hypothesis that the substrate-induced motion originating in one subunit of the MCT dimer could be transmitted to the adjacent subunit to alter its substrate-binding affinity.

Reconstituting redox active centers of heme-containing proteins with biomineralized gold toward peroxidase mimics with strong intrinsic catalysis and electrocatalysis for H2O2 detection.

A facile and efficient enzymatic reconstitution methodology has been proposed for high-catalysis peroxidase mimics by remolding the redox active centers of heme-containing proteins with the in-site biomineralized gold using hemoglobin (Hb) as a model. Catalytic hemin (Hem) was extracted from the active centers of Hb for the gold biomineralization and then reconstituted into apoHb to yield the Hem-Au@apoHb nanocomposites showing dramatically improved intrinsic catalysis and electrocatalysis over natural Hb and Hem. The biomineralized gold, on the one hand, would act as "nanowires" to promote the electron transferring of the nanocomposites. On the other hand, it would create a reactivity pathway to pre-organize and accumulate more substrates towards the active sites of the peroxidase mimics. Steady-state kinetics studies indicate that Hem-Au@apoHb could present much higher substrate affinity (lower Michaelis constants) and intrinsic catalysis even than some natural peroxidases. Moreover, the application feasibility of the prepared artificial enzymes was demonstrated by colorimetric assays and direct electrocatalysis for H2O2 sensing, showing a detection limitation low as 0.45µM. Importantly, such a catalysis active-center reconstitution protocol may circumvent the substantial improvement of the intrinsic catalysis and electrocatalysis of diverse heme-containing proteins or enyzmes toward the extensive applications in the chemical, enviromental, and biomedical catalysis fields.

ZnO nanocomposites modified by hydrophobic and hydrophilic silanes with dramatically enhanced tunable fluorescence and aqueous ultrastability toward biological imaging applications.

Multicolor ZnO quantum dots (QDs) were synthesized and further modified with hydrophobic hexadecyltrimethoxysilane (HDS) and then hydrophilic aminopropyltriethoxysilane (APS) bilayers, resulting in amine-functionalized ZnO@HDS@APS nanocomposites with tunable fluorescence from blue to green yellow. Systematic investigations verify that the resulting ZnO@HDS@APS could display extremely high stability in aqueous media and unexpectedly, dramatically-enhanced fluorescence intensities, which are about 10-fold higher than those of bare ZnO QDs. The feasibility of the as-prepared ZnO nanocomposites for blood, cell, and tissue imaging was preliminarily demonstrated, promising the wide bio-applications for cell or tissue imaging, proteome analysis, drug delivery, and molecular labeling.

A fluorometric microarray with ZnO substrate-enhanced fluorescence and suppressed "coffee-ring" effects for fluorescence immunoassays.

A glass slide was first patterned with hydrophobic hexadecyltrimethoxysilane (HDS) and then microspotted with hydrophilic ZnO nanoparticles in an aminopropyltriethoxysilane (APS) matrix. The resulting HDS-ZnO-APS microarray could present the capability of suppressing the undesirable "coffee-ring" effects through its hydrophobic pattern so as to allow the fabrication of ZnO-APS testing microspots with a highly dense and uniform distribution. The lotus-like "self-cleaning" function could also be expected to effectively curb the cross contamination of multiple sample droplets. More importantly, the introduction of ZnO nanoparticles could endow the testing microspots with substrate-enhanced fluorescence leading to signal-amplification microarray fluorometry. The practical application of the developed HDS-ZnO-APS microarray was investigated by the sandwiched fluorometric immunoassays of human IgG, showing a linear detection range from 0.010 to 10.0 ng mL(-1). Such a throughput-improved fluorometric microarray could be tailored for probing multiple biomarkers in complicated media like serum or blood.

A highly specific and sensitive electroanalytical strategy for microRNAs based on amplified silver deposition by the synergic TiO2 photocatalysis and guanine photoreduction using charge-neutral probes.

TiO2 photocatalysis and guanine photoreduction were synergically combined for amplifying silver deposition for the electroanalysis of short-chain microRNAs with guanine bases using charge-neutral probes. It could allow for the highly specific and sensitive detection of microRNAs in the blood as well as the identification of their mutant levels.