查看更多>>摘要：RhoGTPases are small molecules that control a wide variety of signal transduction pathways. Their profound function in regulating the actin cytoskeleton is well recognized. Stem cells are unique in their ability to self-renew and produce progenitor cells that can differentiate into specialized cells. RhoGTPases influence stem cell morphology and cell migration as well as stem cell self-renewal, proliferation, transplantation, homing and differentiation. In this review, the multiple roles of the RhoGTPases in stem cells are discussed.
Werner E G MUELLERWANG XiaoHongZENG LingSenHeinz C SCHROEDER...
3029-3040页
查看更多>>摘要：Sponges are the oldest and the simplest but not primitive multicellular animals. They represent the earliest evolutionary metazoan phylum still extant. It was a long and painful scientific process to position the most enigmatic and mysterious metazoan, the Porifera, into their correct phylogenetic place among the eukaryotes in general and multicellular animals in particular. As living fossils, sponges provide the best evidence for the early evolution of Metazoa. More recently, interest has been focused on the bionic applications of sponges' siliceous spicules, after the discovery of their unique structure and high fiber performance. In this review, the emergence of sponges, evolutionary novelties found in sponges, and the phylogenetic position of sponges in early metazoan evolution are highlighted. In addition, the present state of knowledge on silicatein-mediated "biosilica" formation in marine sponges, including the involvement of other molecules in silica metabolism and their potential application in nanobiotechnology and medicine, is given.
查看更多>>摘要：The low temperature thermodynamics of the stable phase of vanadium has been assessed by the polynomial and Debye models from the experimental data available in literature. By means of the constrained nonlinear least squares curve fitting arithmetic, two sets of parameter values have been determined. Expressions of the thermodynamic functions C_p(T) and G(T)-H (298.15 K) at 0—298.15 K are presented. The low temperature thermodynamics of the metastable phase of vanadium can only be extrapolated by the Debye model. The expression of the thermodynamic function C_p(T) at 0—298.15 K is presented.
查看更多>>摘要：In order to control group velocity, an annular chain of microring coupled-resonator optical waveguides was analyzed, and its transmission spectra were obtained using the transfer matrix method. The result showed that the curvature of the chain caused the dispersion curves to shift and the resonance frequency got fixed. It is therefore concluded that the group velocity of light in the annular chain of microring coupled-resonator optical waveguides can be controlled by adjusting the curvature of the chain. We believe that such an annular chain can be used as an optical buffer or signal retarder for optical communication.
查看更多>>摘要：The solubility parameters of cellulose acrylate substituted degree 2.12 (CEA) have been calculated from the measured retention data by inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvents at infinite dilution (Ω_1~∞), the Flory-Huggins thermodynamic interaction parameters between CEA and solvents (χ_(12)~∞), the excess molar heats of mixing (△H_1~S), the partial molar heats of mixing at infinite dilution (△H_1~∞), the solubility parameters of solvent (δ_1), and the solubility parameters of CEA (δ_2), were calculated at various temperatures. The δ_2 of the CEA was 17.32, 18.00,18.13,18.54,19.39 at 55, 60, 65, 70 and 75 ℃, respectively.
查看更多>>摘要：The short-lived reactive specimen nitrous acid HONO was generated in the gas phase by the heterogeneous reaction of gaseous HCI with AgNO_2 which can generate higher concentration of HONO than other methods. We investigated the process from generation to dissociation in the gas phase under different controlled temperatures, and discussed the ionization and reaction on the solid surface by combination of the photoelectron spectroscopy and photoionization mass spectroscopy (PES-PIMS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).
查看更多>>摘要：Nanosized TiO_2 particles were prepared by solvothermal method using tetrabutyl titanate as precursor, ethanol and water as solvents, and a facile immobilization method of nanosized TiO_2 particles on woven glass fabric was developed. The samples obtained under various preparation conditions were characterized by means of thermo gravimetric analysis (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), and Brunauer-Emmett-Teller (BET). The results show that the cube-shape of TiO_2 prepared by solvothermal method has good crystallinity of (101) surface, higher thermal stability and large specific surface area. Scanning electron microscopy (SEM) images confirmed that the immobilized TiO_2 film was uniformly distributed and clung to the substrate firmly. The photocatalytic activity of the catalysts was tested using photocatalytic oxidation of gaseous benzene. The results show that the TiO_2 calcined after solvothermal treatment suffers from lower specific surface area, and hence decreases its photocatalytic activity. The photocatalytic activities of the TiO_2 by solvothermal treatment with or without calcination in degradation 400 mg/m~3 benzene are 3.7 and 4.1 times as high as catalyst without solvothermal treatment, respectively.
查看更多>>摘要：Metabonomics analysis of the urine of rats with Qi deficiency and blood stasis syndrome has been performed by comparison with those of normal rats based on NMR techniques. The relative contents of formate, creatinine, 2-oxoglutarate (2-OG), citrate, taurine, trimethylamine-N-oxide(TMAO), succinate and hippurate in the urine of the rats with Qi deficiency and blood stasis syndrome have been changed. These results have provided evidence for understanding the mechanism and the therapy of Qi deficiency and blood stasis syndrome.
查看更多>>摘要：The HIV-1 gp120 exterior envelope glycoprotein undergoes a series of conformational rearrangements while sequentially interacting with the receptor CD4 and coreceptor CCR5 or CXCR4 on the surface of host cells to initiate virus entry. Both the crystal structures of the HIV-1 gp120 core bound by the CD4 and antigen 17b and the SIV gp120 core pre-bound by CD4 are known. Despite the wealth of knowledge on these static snapshots of molecular conformations, the details of molecular motions involved in conformational transition that are crucial to intervention remain elusive. We presented comprehensive comparative analyses of the dynamics behaviors of the gp120 in its CD4-complexed, CD4-free and CD4-unliganded states based on the homology models with modeled V3 and V4 loops by means of CONCOORD computer simulation to generate ensembles of feasible protein structures that were subsequently analysed by essential dynamics analyses to identify preferred concerted motions. The revealed collective fluctuations are dominated by complex modes of combinational motions of the rotation/twisting, flexing/closure, and shortness/elongation between or within the inner, outer, and bridging-sheet domains, and these modes are related to the CD4 association and HIV neutralization avoidance. Further essential subspace overlap analyses were performed to quantitatively distinguish the preference for conformational transitions between the three states, revealing that the unliganded gp120 has a greater potential to translate its conformation into the conformational state adopted by the CD4-complexed gp120 than by the CD4-free gp120, whereas the CD4-free gp120 has a greater potential to translate its conformation into the unliganded state than the CD4-complexed gp120 does. These dynamics data of gp120 in its different conformations are helpful in understanding the relationship between the molecular motion/conformational transition and the function of gp120, and in gp120-structure-based subunit vaccine design.
查看更多>>摘要：Neurotransmitters are released by the fusion of synaptic vesicles with presynaptic membrane, which has been extensively studied. The analysis of single vesicle fusion kinetics reveals that there exist fusion modes of "kiss and run" and "kiss and stay" which may be favored by neurons especially during strong firing beside full fusion. Pre-fusion steps of translocation, docking and priming along the exo-cytotic pathway play important roles in neurotransmitter release and its regulation. In the present report, we used dual-color imaging of VAMP2-pHluorin and VAChT-TDimer2 under total internal reflection fluorescence microscope (TIRFM) to monitor the docking and fusion of synaptic-like microvesicles (SLMVs) in PC12 cells stimulated by high K~+. Our results show that "kiss and run" is a dominative fusion mode in PC12 cells under high K~+-challenge, and the dwell time of SLMVs is prolonged by the high K~+ stimulation that suggests an enhancement of vesicle priming.
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