Structural basis of the lipid transfer mechanism of phospholipid transfer protein (PLTP).

Human phospholipid transfer protein (PLTP) mediates the transfer of phospholipids among atheroprotective high-density lipoproteins (HDL) and atherogenic low-density lipoproteins (LDL) by an unknown mechanism. Delineating this mechanism would represent the first step towards understanding PLTP-mediated lipid transfers, which may be important for treating lipoprotein abnormalities and cardiovascular disease. Here, using various electron microscopy techniques, PLTP is revealed to have a banana-shaped structure similar to cholesteryl ester transfer protein (CETP). We provide evidence that PLTP penetrates into the HDL and LDL surfaces, respectively, and then forms a ternary complex with HDL and LDL. Insights into the interaction of PLTP with lipoproteins at the molecular level provide a basis to understand the PLTP-dependent lipid transfer mechanisms for dyslipidemia treatment.

Experimental Study on Mechanical Properties of Rebar in Steel Half-Grouted Sleeve Connections with Construction Defects.

A prefabricated concrete structure is a building structure designed for sustainability and low comprehensive carbon emission. The grouted sleeve splice is a major connection method for prefabricated concrete structures. However, construction defects occur easily in the grouted sleeve splice connection at construction sites because of complex construction environments and the high connection accuracy. To determine the influence of rebar in steel half-grouted sleeve connections with construction defects, investigations were conducted using four different test groups (rebar offset, rebar bended, insufficient fluidity of grout, and control group). The load-displacement curve and load-stress curve were analyzed on 24 different specimens through uniaxial tension experiments. The experimental results showed that rebar fracture was the failure of specimens. The load-displacement curves consisted of elastic, yield, strength, and tight stages. The curves were similar to rebar under uniaxial tension, except for the rebar bended group. The axial stress and circumferential stress on the sleeve surface consistently followed a linear response before the specimen yield, whereas the axial stress and circumferential stress showed a rebound response after the specimen yielded. Different finite element models were established based on the different defects. Compared with the experimental results, the finite element analysis results coincided with those of the experimental results, and the errors were within 8% to evaluate the performance of steel half-grouted sleeve connections in construction.

Membrane-directed molecular assembly of the neuronal SNARE complex.

Since the discovery and implication of N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptor (SNARE) proteins in membrane fusion almost two decades ago, there have been significant efforts to understand their involvement at the molecular level. In the current study, we report for the first time the molecular interaction between full-length recombinant t-SNAREs and v-SNARE present in opposing liposomes, leading to the assembly of a t-/v-SNARE ring complex. Using high-resolution electron microscopy, the electron density maps and 3D topography of the membrane-directed SNARE ring complex was determined at nanometre resolution. Similar to the t-/v-SNARE ring complex formed when 50 nm v-SNARE liposomes meet a t-SNARE-reconstituted planer membrane, SNARE rings are also formed when 50 nm diameter isolated synaptic vesicles (SVs) meet a t-SNARE-reconstituted planer lipid membrane. Furthermore, the mathematical prediction of the SNARE ring complex size with reasonable accuracy, and the possible mechanism of membrane-directed t-/v-SNARE ring complex assembly, was determined from the study. Therefore in the present study, using both lipososome-reconstituted recombinant t-/v-SNARE proteins, and native v-SNARE present in isolated SV membrane, the membrane-directed molecular assembly of the neuronal SNARE complex was determined for the first time and its size mathematically predicted. These results provide a new molecular understanding of the universal machinery and mechanism of membrane fusion in cells, having fundamental implications in human health and disease.

A carboxymethyl lentinan layer by layer self-assembly system as a promising drug chemotherapeutic platform.

Surface functionalization of mesoporous silica nanoparticles (MSNs) has been proposed as an efficient strategy for enhancing the biocompatibility and efficiency of an MSN-based carrier platform. Herein, natural polyelectrolyte multilayers composed of poly-l-ornithine (PLO) and carboxymethyl lentinan (LC) were coated on the surface of MSNs through a layer-by-layer (LbL) self-assembly technique, and were characterized by ζ-potential, FTIR, 13C NMR, SEM, TEM, XRD, and TG. The prepared carrier presented alternating positive and negative potentials when coated with the polyelectrolytes, and the surface of MSN-PLO/LC was rougher compared to the naked MSNs. The biocompatibility tests, including cytocompatibility, hemocompatibility, and histocompatibility, showed that MSNs biocompatibility could be improved by modifying LC. A high loading and sustained release drug delivery system was constructed after loading doxorubicin (DOX) into the prepared MSN-PLO/LC, which exhibited significant anti-proliferative efficiency in human cervical cancer cell lines (Hela). Therefore, the PLO/LC LbL NPs (layer-by-layer self-assembled nanoparticles coated with PLO/LC layers) based on MSNs, which is easily prepared by electrostatic interactions, can be considered a promising drug chemotherapeutic platform and delivery technique for future human cervical cancer therapy.

[Studies on technology optimization for extraction and purification of total flavones from root bark of Artocarpus styracifolius].

OBJECTIVE: To study the technology optimization for extraction and purification of total flavones from root bark of Artocarpus styracifolius. METHODS: The optimum extraction conditions were investigated by the contents of the total flavones, using orthogonal test; Static adsorption capacity and desorption rate were employed as examine items for the screening of optimum macroporous resin and optimum technology for the purification of total flavones with selected macroporous were also investigated. RESULTS: The optimum extraction conditions were as follows: using 60% alcohol of seven times than amounts of original material soaking 12 hours,extracting once with hot reflux method at 50 degrees C. HPD-500 type macroporous resin showed better adsorption and desorption property. The optimum purification conditions were as follows: the sample solution was prepared at the concentration of 50.0 mg/mL, subjected to HPD-500 type macroporous resin column chromatography with a load ratio of 22.0 mg total flavones per gram of resin. After standing for 1 hour, the column was eluted with 4 BV water before being eluted with 4 BV 80% alcohol. The purity of the product was 86.4%, which enhanced the content of total flavones by 533%. CONCLUSION: The optimum conditions for extraction and purification of total flavones from root bark of Artocarpus styractifolius are convenient and practical, and could be used as a reference for industrial production.

Antiviral activity of sophoridine against enterovirus 71 in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Enterovirus 71 (EV71) has a propensity to cause hand-foot-and-mouth disease (HFMD) epidemics associated with neurological sequelae. Unfortunately, no drugs are currently available for the clinical treatment of EV71 infections. Sophoridine (SRI) is one of the most abundant alkaloids in Sophora flavescens Aiton (Leguminosae), which has been used to treat fever, throat inflammation, cancer, and other diseases. MATERIALS AND METHODS: In this study, we found that SRI inhibits EV71 infection in Vero cells. To study the antiviral activity of SRI, Vero cells were divided into 3 treatment groups based on the timing of SRI dosing: prior to viral adsorption (Group A), during viral adsorption (Group B), and after viral adsorption (Group C). We further revealed the antiviral activity of SRI with the attachment assay and the penetration assay. For Group A, 50% viability of Vero cells was observed at a SRI concentration of 61.39 µg/mL, whereas for Groups B, 50% viability was observed at SRI concentrations of 196.86 µg/mL. Furthermore, 29.7% cell viability was observed even at a SRI concentration of 1000 µg/mL in Groups C. The results show that SRI was highly effective against EV71 when Vero cells were pretreated with SRI for 2 h (Group A). Further researches indicate SRI was highly effective at inhibiting EV71 attachment when the SRI concentrations over 250 µg/mL (P < 0.001). CONCLUSIONS: We have shown that Vero cell viability increases when SRI is administered prior to viral adsorption. This suggests that SRI has the considerable potential as an antiviral for EV71 disease prevention.

Electron Tomography: A Three-Dimensional Analytic Tool for Hard and Soft Materials Research.

Three-dimensional (3D) structural analysis is essential to understand the relationship between the structure and function of an object. Many analytical techniques, such as X-ray diffraction, neutron spectroscopy, and electron microscopy imaging, are used to provide structural information. Transmission electron microscopy (TEM), one of the most popular analytic tools, has been widely used for structural analysis in both physical and biological sciences for many decades, in which 3D objects are projected into two-dimensional (2D) images. In many cases, 2D-projection images are insufficient to understand the relationship between the 3D structure and the function of nanoscale objects. Electron tomography (ET) is a technique that retrieves 3D structural information from a tilt series of 2D projections, and is gradually becoming a mature technology with sub-nanometer resolution. Distinct methods to overcome sample-based limitations have been separately developed in both physical and biological science, although they share some basic concepts of ET. This review discusses the common basis for 3D characterization, and specifies difficulties and solutions regarding both hard and soft materials research. It is hoped that novel solutions based on current state-of-the-art techniques for advanced applications in hybrid matter systems can be motivated.

HDL surface lipids mediate CETP binding as revealed by electron microscopy and molecular dynamics simulation.

Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesterol esters (CE) from atheroprotective high-density lipoproteins (HDL) to atherogenic low-density lipoproteins (LDL). CETP inhibition has been regarded as a promising strategy for increasing HDL levels and subsequently reducing the risk of cardiovascular diseases (CVD). Although the crystal structure of CETP is known, little is known regarding how CETP binds to HDL. Here, we investigated how various HDL-like particles interact with CETP by electron microscopy and molecular dynamics simulations. Results showed that CETP binds to HDL via hydrophobic interactions rather than protein-protein interactions. The HDL surface lipid curvature generates a hydrophobic environment, leading to CETP hydrophobic distal end interaction. This interaction is independent of other HDL components, such as apolipoproteins, cholesteryl esters and triglycerides. Thus, disrupting these hydrophobic interactions could be a new therapeutic strategy for attenuating the interaction of CETP with HDL.

Affibody-based nanoprobes for HER2-expressing cell and tumor imaging.

This article reports the affibody-based nanoprobes specifically target and image human epidermal growth factor receptor type 2 (HER2)-expressing cells and tumors. The affibody molecules are a promising class of targeting ligands with simple, robust, and precise structure and high affinity. Using near-infrared (NIR) quantum dots (QDs) and iron oxide (IO) nanoparticles as two representative nanomaterials, we designed anti-HER2 affibody molecules with a N-terminus cysteine residue (Cysteine-Z(HER2:342)) and precisely conjugated with maleimide-functionalized nanoparticles to make nanoparticle-affibody conjugates. The in vitro and in vivo study showed the conjugates are highly specific to target and image HER2-expressing cells and tumors. This work indicated the nanoparticle-affibody conjugates may be excellent candidates as targeting probes for molecular imaging and diagnosis.

Molecular optical imaging with radioactive probes.

BACKGROUND: Optical imaging (OI) techniques such as bioluminescence and fluorescence imaging have been widely used to track diseases in a non-invasive manner within living subjects. These techniques generally require bioluminescent and fluorescent probes. Here we demonstrate the feasibility of using radioactive probes for in vivo molecular OI. METHODOLOGY/PRINCIPAL FINDINGS: By taking the advantages of low energy window of light (1.2-3.1 eV, 400-1000 nm) resulting from radiation, radionuclides that emit charged particles such as beta(+) and beta(-) can be successfully imaged with an OI instrument. In vivo optical images can be obtained for several radioactive probes including 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG), Na(18)F, Na(131)I, (90)YCl(3) and a (90)Y labeled peptide that specifically target tumors. CONCLUSIONS/SIGNIFICANCE: These studies demonstrate generalizability of radioactive OI technique. It provides a new molecular imaging strategy and will likely have significant impact on both small animal and clinical imaging.