Effects of Surface Microtopology and Membrane Stiffness on Kinetics of Selectin/Ligand interactions by a Modified BFP

More and more evidences come out to support that the functionality of adhesion molecules are influenced by the surface microtopology of cell carrier or substrate. Adhesive molecules usually express on the microvilli of a cell, providing a well-defined spatial configuration to mediate the adhesions to the counterpart molecules on the apposed surface.

Forced Dissociation of Selectin-ligand Complexes Using Steered Molecular Dynamics Simulation

Selectin-ligand interactions are crucial to such biological processes as inflammatory cascade or tumor metastasis. How transient formation and dissociation of selectin-ligand bonds in blood flow are coupled to molecular conformation at atomic level, however, has not been well understood. In this study, steered molecular dynamics (SMD) simulations were used to elucidate the intramolecular and intermolecular conformational evolutions involved in forced dissociation of three selectin-ligand systems: the construct consisting of P-selectin lectin (Lec) and epidermal growth factor (EGF)-like domains (P-LE) interacting with synthesized sulfoglycopeptide or SGP-3, P-LE with sialyl Lewis X (sLeX), and E-LE with sLeX. SMD simulations were based on newly built-up force field parameters including carbohydrate units and sulfated tyrosine(s) using an analogy approach. The simulations demonstrated that the complex dissociation was coupled to the molecular extension. While the intramolecular unraveling in P-LESGP-3 system mainly resulted from the destroy of the two anti-parallel sheets of EGF domain and the breakage of hydrogen-bond cluster at the Lec-EGF interface, the intermolecular dissociation was mainly determined by separation of fucose (FUC) from Ca2+ ion in all three systems. Conformational changes during forced dissociations depended on pulling velocities and forces, as well as on how the force was applied. This work provides an insight into better understanding of conformational changes and adhesive functionality of selectin-ligand interactions under external forces.

Membrane Deformability and Membrane Tension of Single Isolated Mitochondria

Mitochondria dynamics is crucial to many biological processes such as mitochondria fusion and fission, which is highly correlated to the mechanics of single mitochondria. However, the mechanobiological coupling of mitochondria has been poorly understood. Here membrane deformability and membrane tension of individual mitochondria isolated from MtDsRed labeled human embryonic T-Rex-293 kidney cells were measured using a micropipette aspiration assay. The results demonstrated that membrane deformation of isolated mitochondria exhibited an elastic transition phase followed by an equilibrium phase, and mitochondrial membrane tension was proportional to the area compressibility. It was also indicated that mitochondrial membrane deformability was significantly affected by physical chemical factors such as osmotic pressure or pH value, and was further correlated to mitochondrial functionality in different respiratory states and Ca2+ regulation. These findings provide a new insight into understanding the mechanical regulation of mitochondrial physiology.

Microstructural and compositional characteristics of GaN films grown on a ZnO-buffered Si(111) wafer

Polycrystalline GaN thin films have been deposited epitaxially on a ZnO-buffered (111)-oriented Si substrate by molecular beam epitaxy. The microstructural and compositional characteristics of the films were studied by analytical transmission electron microscopy (TEM). A SiO2 amorphous layer about 3.5 nm in thickness between the Si/ZnO interface has been identified by means of spatially resolved electron energy loss spectroscopy. Cross-sectional and plan-view TEM investigations reveal (GaN/ZnO/SiO2/Si) layers exhibiting definite a crystallographic relationship: [111](Si)//[111](ZnO)//[0001](GaN) along the epitaxy direction. GaN films are polycrystalline with nanoscale grains (similar to100 nm in size) grown along [0001] direction with about 20degrees between the (1 (1) over bar 00) planes of adjacent grains. A three-dimensional growth mode for the buffer layer and the film is proposed to explain the formation of the as-grown polycrystalline GaN films and the functionality of the buffer layer. (C) 2004 Elsevier Ltd. All rights reserved.

Photovoltaic and electroluminescence characters in hybrid ZnO and conjugated polymer bulk heterojunction devices

We report electroluminescence in hybrid ZnO and conjugated polymer poly[2-methoxy-5-(3', 7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) bulk heterojuriction photovoltaic cells. Photolummescence quenching experimental results indicate that the ultra,fast photoinduced electron transfer occurs from MDMO-PPV to ZnO under illumination. The ultrafast photoinduced electron transfer effect is induced because ZnO has an electron affinity about 1.2 eV greater than that of MDMO-PPV. Electron 'back transfer' can occur if the interfacial barrier between ZnO and MDMO-PPV can be overcome by applying a substantial electric field. Therefore, electroluminescence action due to the fact that the back transfer effect can be observed in the ZnO:MDMO-PPV devices since a forward bias is applied. The photovoltaic and electroluminescence actions in the same ZnO:MDMO-PPV device can be induced by different injection ways: photoinjection and electrical injection. The devices are expected to provide an opportunity for dual functionality devices with photovoltaic effect and electroluminescence character.

Wavelength tunable distributed Bragg reflector laser integrated with electro-absorption modulator by a combined method of selective area growth and quantum well intermixing - art. no. 68240N

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10(-10) after 44.4 km standard fiber transmission.

Novel compact SOI-based reconfigurable optical add/drop multiplexer using microring resonators - art. no. 60190L

Novel compact design for 4-channel SOI-based reconfigurable optical add/drop multiplexer using microring resonators is presented and analyzed. Microring resonators have two important attributes as a key new technology for future optical communications, namely functionality and compactness. Functionality refers to the fact that a wide range of desirable filter characteristics can be synthesized by coupling multiple rings. Compactness refers the fact that ring resonators with radii about 30 mu m can lead to large scale integration of devices with densities on the order of 10(4) similar to 10(5) devices per square centimeter. A 4-channel reconfigurable optical add/drop multiplexer comprises a grid-like array of ridge waveguides which perpendicularly cross through each other. SOI-based resonators consisted of multiple rings at each of the cross-grid nodes serve as the wavelength selective switch, and they can switch an optical signal between two ports by means of tuning refractive index of one of the rings. The thermo-optic coefficient of silicon is 1.86x 10(-4) /K. Thus a temperature rise of 27K will increase the refractive index by 5 x 10(-3), which is enough to cause the switching of our designed microring resonators. The thermo-optic effect is used to suppress the resonator power transfer, rather than to promote loss. Thus, the input signal only suffers small attenuation and simultaneously low crosstalk can be achieved by using multiple rings.

Microstructural and compositional characteristics of GaN films grown on a ZnO-buffered Si(111) wafer

Polycrystalline GaN thin films have been deposited epitaxially on a ZnO-buffered (111)-oriented Si substrate by molecular beam epitaxy. The microstructural and compositional characteristics of the films were studied by analytical transmission electron microscopy (TEM). A SiO2 amorphous layer about 3.5 nm in thickness between the Si/ZnO interface has been identified by means of spatially resolved electron energy loss spectroscopy. Cross-sectional and plan-view TEM investigations reveal (GaN/ZnO/SiO2/Si) layers exhibiting definite a crystallographic relationship: [111](Si)//[111](ZnO)//[0001](GaN) along the epitaxy direction. GaN films are polycrystalline with nanoscale grains (similar to100 nm in size) grown along [0001] direction with about 20degrees between the (1 (1) over bar 00) planes of adjacent grains. A three-dimensional growth mode for the buffer layer and the film is proposed to explain the formation of the as-grown polycrystalline GaN films and the functionality of the buffer layer. (C) 2004 Elsevier Ltd. All rights reserved.

Silicon: the promising material for phontonic integrated circuits platform

The development of optical network demands integrated arid multiple functionality modules to lowing cost and acquire highly reliability. Among the various contender materials to be photonic integrated circuits platform, silicon exhibits dominant characteristics and is the most promising platform materials. The paper compares the characteristics of some candidate materials with silicon and reviews recent progress in silicon based photonic integration technology. Tile challenges to silicon for optical integration for optical networking application arc also indicated.

Synthesis and Characterization of Urea Bridged Hybrid Periodic Mesoporous Organosilica Materials

Urea bridged organic-inorganic hybrid mesoporous SiO2 materials (U-BSQMs) were synthesized through a sol-gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of Si-29 (Si-29, CP-MAS NMR) and C-13 (C-13 CP NMR) indicated that most of the Si-C bonds are unbroken during the synthesis process.

Microarray-based Raman spectroscopic assay for kinase inhibition by gold nanoparticle probes

In this paper, a microarray-based surface-enhanced Raman spectroscopic (SERS) assay for detection of kinase functionality and inhibition has been reported. Biotinylated anti-phosphoserinen antibodies mark the phosphorylation and inhibition events and gold nanoparticles are attached to the antibodies by standard avidin-biotin chemistry, followed by silver deposition for SERS signal enhancement. The avidin conjugated fluorescein is used as SERS probe. The alpha-catalytic subunit of cyclic adenosine 5'-monophosphate (cAMP) dependent protein kinase (PKA), its well known substrate, kemptide, and three inhibitors, H89, HA1077, and KN62 have been chosen here to establish the SERS assay. As expected, highly selective inhibition of PKA is demonstrated with the inhibitor H89 and the inhibition assay enable to detect kinase inhibition as well as derive IC50 (half maximal inhibitory concentration) plots.

Study on the lifetime of M-intermediate of bacteriorhodopsin film chemically modified with CeO2 nanoparticles

The characteristics of intermediates of bacteriorhodopsin (bR) can be verified by chemical modification of its surroundings. CeO2 nanoparticles, which were obtained using water-in-oil (W/O) microemulsion and calcined at various temperatures, were used as chemical additive for the modification of bR. X-ray diffraction (XRD) shows that the mean particle sizes for the samples calcined at 500 and 800 degrees C are approximately 10 and 30 nm, respectively. We prepared CeO2 nanoparticle modified poly(vinyl alcohol) (bR-PVA) films with an optical density of about 1.5 at the ground state. It is observed that the lifetime of the Wintermediate for the modified films is prolonged compared with that of the unmodified ones, and the lifetime increases with decreasing particle size. A probable mechanism, which is likely to involve effective molecular interactions between the CeO2 nanoparticles and the bR molecules, is discussed. The hydroxyl groups, which might arise from the interaction between the nanoparticles and the surrounding water molecules, help to lower the ability of the Schiff base of uptaking protons in the Wintermediate. The results indicate that controlling the interactions between biomolecules and various nanomaterials would enlarge the functionality and the range of the application of nanoparticles.

Colloidal crystal heterostructures by a two-step vertical deposition method

A two-step template-induced vertical deposition technique was introduced to fabricate the colloidal crystal heterostructures due to wettability differences and spatial confinement of the templates structured with microchannels. The heterostructures exhibited a bi-frequency Bragg diffraction whose position was determined by the microsphere diameter of the opals. It was demonstrated that the channel width had an influence on the optical properties of the colloidal crystal heterostructures. The strategy proposed is suited for fabrication of different micron-sized opal architectures with complex form and designed optical functionality.

2-cyanoprop-2-yl dithiobenzoate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2-cyanoprop-2-yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANS were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. H-1 NMR analysis confirmed the high chain-end functionality of the resultant polymers.

Dibenzyl trithiocarbonate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile

Reversible addition-fragmentation chain transfer polymerization has been successfully applied to polymerize acrylonitrile with dibenzyl trithiocarbonate as the chain-transfer agent. The key to success is ascribed to the improvement of the interchange frequency between dormant and active species through the reduction of the activation energy for the fragmentation of the intermediate. The influence of several experimental parameters, such as the molar ratio of the chain-transfer agent to the initiator [azobis(isobutyronitrile)], the molar ratio of the monomer to the chain-transfer agent, and the monomer concentration, on the polymerization kinetics and the molecular weight as well as the polydispersity has been investigated in detail. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and H-1 NMR analyses have confirmed the chain-end functionality of the resultant polymer.