Single-molecule motions of oligoarginine transporter conjugates on the plasma membrane of Chinese hamster ovary cells

To explore the real-time dynamic behavior of molecular transporters of the cell-penetrating-peptide (CPP) type on a biological membrane, single fluorescently labeled oligoarginine conjugates were imaged interacting with the plasma membrane of Chinese hamster ovary (CHO) cells. The diffusional motion on the membrane, characterized by single-molecule diffusion coefficient and residence time (tau R), defined as the time from the initial appearance of a single-molecule spot on the membrane (from the solution) to the time the single molecule disappears from the imaging focal plane, was observed for a fluorophore-labeled octaarginine (a model guanidinium-rich CPP) and compared with the corresponding values observed for a tetraarginine conjugate (negative control), a lipid analogue, and a fluorescently labeled protein conjugate (transferrin-Alexa594) known to enter the cell through endocytosis. Imaging of the oligoarginine conjugates was enabled by the use of a new high-contrast fluorophore in the dicyanomethylenedihydrofuran family, which brightens upon interaction with the membrane at normal oxygen concentrations. Taken as a whole, the motions of the octaarginine conjugate single molecules are highly heterogeneous and cannot be described as Brownian motion with a single diffusion coefficient. The observed behavior is also different from that of lipids, known to penetrate cellular membranes through passive diffusion, conventionally involving lateral diffusion followed by membrane bilayer flip-flop. Furthermore, while the octaarginine conjugate behavior shares some common features with transferrin uptake (endocytotic) processes, the two systems also exhibit dissimilar traits when diffusional motions and residence times of single constructs are compared. Additionally, pretreatment of cells with cytochalasin D, a known actin filament disruptor, produces no significant effect, which further rules out unimodal endocytosis as the mechanism of uptake. Also, the involvement of membrane potential in octaarginine-membrane interaction is supported by significant changes in the motion with high [K(+)] treatment. In sum, this first study of single transporter motion on the membrane of a living cell indicates that the mode by which the octaarginine transporter penetrates the cell membrane appears to either be a multimechanism uptake process or a mechanism different from unimodal passive diffusion or endocytosis.     

Site-selective catalytic surface activation via aerosol nanoparticles for use in metal micropatterning

There is great interest in the fabrication of micro- and nanopatterned metallic structures on substrates for a wide range of electronic, photonic, and magnetic devices. One of the most widely used techniques is the electroless deposition (ELD) of metal, which requires the surface activation of the substrates with a metal catalyst. This paper introduces a method of catalytic surface activation by producing platinum aerosol nanoparticles via spark generation and then thermophoretically depositing the particles onto a flexible polyimide (PI) substrate through the pattern hole of a mask. After annealing, the catalytically activated substrate is placed into a solution for electroless silver deposition. The silver is then formed only on the activated regions of the substrate. Silver line patterns having a width of 18 microm and a height of 1 microm are created with the ability to be effectively reproduced. The average value of the resistivities is approximately 6.8 mu Omega.cm, which is almost comparable to the theoretical resistivity of bulk silver (1.6 mu Omega.cm). Other silver micropatterns containing square dot array, line, line array, Y-branched line, and tapered line using different pattern masks are also demonstrated.     

In vitro biocompatibility of three‐dimensional chitosan scaffolds immobilized with chondroitin‐6‐sulfate

Cellular‐compatible scaffolds were prepared using a three‐dimensional micro‐porous chitosan (CS) non‐woven fabric immobilized by glutaraldehyde (GA), followed by the immobilization of chondroitin‐6‐sulfate (ChS). To characterize the immobilizing process, tensile analysis, and scanning electron microscopy (SEM) were performed. The cell seeding efficiency and proliferation test were evaluated using L929 fibroblasts. The chitosan scaffolds showed high water vapor transmission rate and antibacterial activity. In addition, ChS‐immobilized scaffolds exhibited higher cell seeding efficiency and fibroblasts proliferation. These results demonstrated that the CS non‐woven fabrics grafted with GA and immobilized with ChS could be an appropriate candidate for wound healing and artificial scaffolds in the clinical applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of a palm portable mass spectrometer

A palm portable mass spectrometer (PPMS) has been developed with a weight of 1. 48 kg (3 lb) and a size of 1.54 L (8.2 × 7.7 × 24.5 cm³) that can be operated with an average battery power of 5 W. A miniaturized ion trap has been used as a mass analyzer that consists of four parallel disks with coaxial holes. A rf voltage of 1500 V _p-p at 3.9 MHz has been used for scanning ion mass of up to m/z 300. An ion-getter pump serves for high vacuum of the PPMS. Sample gas was introduced in pulse mode. An embedded microcomputer has been developed for system control. Detection of organic gases diluted in the air has been demonstrated up to 6 ppm for toluene and 22 ppm for dimethyl methylphosphonate (DMMP). Performance results suggest usefulness of the PPMS as a personal mobile device for detection/identification of chemical warfare agents in the field.     

Temperature-triggered gate opening for gas adsorption in microporous manganese formate

Microporous manganese formate shows temperature-triggered gate opening for nitrogen and argon adsorption, which is not due to a structural change of the framework but due to dynamic opening of the pore aperture and/or sufficient kinetic energy of the adsorbates to overcome a diffusion barrier above a critical temperature.     

Mesoporous Titania Thin Film with Highly Ordered and Fully Accessible Vertical Pores and Crystalline Walls

We report the preparation of mesoporous titania thin films with the R m pore structure derived from the Im m self‐assembled ordering of the titania species and an EO₁₀₆PO₇₀EO₁₀₆ triblock copolymer. The films were spin‐cast and then aged at 18 °C at a relative humidity of 70 %, which led to the orientation of the Im m structure with the [111] direction perpendicular to the substrates. The [111] body‐diagonal channels became vertical channels upon calcination at 400 °C, thus leading to thin films with vertical channels. The pores are ordered over a large area of up to 1 μm². The titania films can be formed on various types of substrates. By using a titania film formed on a Pt‐coated Si wafer as a template, we produced by an electrochemical‐deposition technique arrays of gold nanowires, whose morphology suggests that most of the pores of the titania thin films are accessible. The pore structure of vertical channels is stable up to 600 °C, at which temperature the wall materials crystallize into anatase.     

A Mesoporous Silica Thin Film as Uptake Host for Guest Molecules with Retarded Release Kinetics

Uptake and release processes of various fluorescent rhodamine dyes and antitumor drugs to/from an ordered mesoporous silica film are investigated by means of UV/Vis absorption and fluorescence spectroscopies. The pores in the 160 nm‐thick silica film strongly withdraw the dyes from water, thus allowing the storage of several micrograms of guest molecules per square centimeter of film. The binding equilibrium of the dyes follows a Langmuir‐type adsorption. The dissociation constant, K_d, and the maximum binding amount to the film, , are determined by fitting the binding curves. The release kinetics of the guests from the film to a simulated body fluid (SBF) solution follows a bimodal first‐order exponential behavior. The release kinetics from the mesoporous thin film is remarkably retarded relative to that from mesoporous powders. Among all the studied dyes, rhodamine 101 is released most slowly, which implies that the release rate depends not only on the interactions between the guests and the silica surface, but also on intermolecular interactions between the guest molecules. Comparison of the release kinetics of different antitumor drugs, such as actinomycin D and mitoxantrone, into an SBF solution shows that mitoxantrone is released much slowly. This slower release is attributed to the positive molecular charge and the formation of dimers in the pores.     

Stereoselective total synthesis of (-)-perrottetinene and assignment of its absolute configuration

The first stereoselective total synthesis of the bibenzyl tetrahydrocannabinol, (-)-perrottetinene, has been achieved from readily available starting materials. The absolute stereochemistry is derived from a chiral gamma-hydroxy vinylstannane. The key reaction is the synthesis of the cis-disubstituted cyclohexene ring of perrottetinene by diastereoselective Ireland-Claisen rearrangement and a ring-closing metathesis reaction. The absolute configuration of (-)-perrottetinene is proposed.     

Efficiency of bulky protic solvent for SN2 reaction

We calculate and compare the effects of aprotic vs protic solvent on the rate of SN2 reaction [F- + C3H7OMs--> C3H7F + OMs-]. We find that aprotic solvent acetonitrile is more efficient than a small protic solvent such as methanol. Bulky protic solvent (tert-butyl alcohol) is predicted to be quite efficient, giving the rate constant that is similar to that in CH3CN. Our calculated relative activation barriers of the SN2 reaction in methanol, tert-butyl alcohol, and CH3CN are in good agreement with experimental observations.     

Guaiacol as an Organic Superoxide Dismutase Mimics for Anti-ageing a Ru-based Li-rich Layered Oxide Cathode

High-capacity Li-rich layered oxides using oxygen redox as well as transition metal redox suffer from its structural instability due to lattice oxygen escaped from its structure during oxygen redox and the following electrolyte decomposition by the reactive oxygen species. Herein, we rescued a Li-rich layered oxide based on 4d transition metal by employing an organic superoxide dismutase mimics as a homogeneous electrolyte additive. Guaiacol scavenged superoxide radicals via dismutation or disproportionation to convert two superoxide molecules to peroxide and dioxygen after absorbing lithium superoxide on its partially negative oxygen of methoxy and hydroxyl groups. Additionally, guaiacol was decomposed to form a thin and stable cathode-electrolyte interphase (CEI) layer, endowing the cathode with the interfacial stability.