Stability of a Linear Plasma Crystal

Plasma Physics Reports - The stability of a linear chain of dust particles in an external confining force field is studied. It is assumed that the particles are located in a plasma with Maxwellian...     

Plasma Crystal as a Time Crystal

Plasma Physics Reports - The nonlinear development stage is studied of the instability of coupled waves in the planar plasma crystal in the external confining force field. It is assumed that the...     

Wetting of Planar Surfaces by a Gay-Berne Liquid Crystal

Molecular simulation of the wetting of an unstructured attractive wall by Gay-Berne liquid crystals are reported. Simulations are performed in the grand canonical ensemble on a wide pore at constant temperatures of T *=0.53 and 0.56, corresponding to temperatures below and above the nematic-isotropic-vapor triple point. Close to the coexistence chemical potential, a thick liquid film wets the solid surface. The film is composed of stratified layers of molecules parallel to the solid surface, which follow to a nematic domain at the lower temperature and an isotropic one at the higher temperature. In both cases, the film is in equilibrium with the corresponding vapor phase. Close to the liquid-vapor interface there is a manifest tendency for the molecules to orient themselves parallel to the interface. The adsorption on the wall varies continuously with the thermodynamic parameters considered and no evidence of a first order prewetting transition is observed.     

A Planar Source of Atmospheric-Pressure Plasma Jet

In a single-barrier discharge with voltage sharpening and low gas consumption (up to 1 L/min), plane atmospheric pressure plasma jets with a width of up to 3 cm and length of up to 4 cm in air are formed in the slit geometry of the discharge zone. The energy, temperature, and spectral characteristics of the obtained jets have been measured. The radiation spectrum contains intense maxima corresponding to vibrational transitions of the second positive system of molecular nitrogen N₂ (C³Π _u → B³Π _g ) and comparatively weak transition lines of the first positive system of the N ₂ ⁺ ion (B²Σ _u ⁺ → X²Σ _g ). By an example of inactivation of the Staphylococcus aureus culture (strain ATCC 209), it is shown that plasma is a source of chemically active particles providing the inactivation of microorganisms.     

Nonlinear Theory of Aperiodic Instabilities of a Plasma Crystal

Plasma Physics Reports - The nonlinear stage of aperiodic instabilities of a single-layer plasma crystal with a triangular lattice is studied theoretically. Depending on the parameters of the...     

Characterization of the Red Beet Plasma Membrane H+-ATPase Reconstituted in a Planar Bilayer System

The transport activity of the red beet (Beta vulgaris L.) plasma membrane H+-ATPase was examined following reconstitution into a planar bilayer membrane. Fusion of partially purified plasma membrane H+-ATPase with the bilayer membrane was accomplished by perfusion of proteoliposomes against the bilayer under hypoosmotic conditions. Following incorporation into the bilayer, an ATP-dependent current was measured that demonstrated properties consistent with those of the plasma membrane H+-ATPase. Current production was substrate specific for ATP, inhibited by orthovanadate, and insensitive to 200 nM erythrosin B but inhibited by 100 [mu]M erythrosin B. When current production was measured as a function of Mg:ATP concentration, a simple Michaelis-Menten relationship was observed and a Km of 0.62 mM was estimated. Current-voltage analysis of ATP-dependent current in the presence of 0.5 mM ATP, 20 mM ADP, 40 mM orthophosphate, and an opposing 2.5-unit [delta]pH revealed a reversal potential of about -149 mV. Based on the free energy available from ATP hydrolysis, this reversal potential is consistent with an H+/ATP stoichiometry of 1. This study demonstrates the usefulness of a planar bilayer system for investigation of energy coupling to H+ transport by the plasma membrane H+-ATPase.     

Effect of Nonreciprocal Forces on Brownian Motion of Plasma Crystal

Plasma Physics Reports - The effect is studied theoretically of nonreciprocity of interparticle forces on the Brownian motion of a single-layer plasma crystal with the hexagonal lattice. The...     

Filamin-A Increases the Stability and Plasma Membrane Expression of Polycystin-2

Polycystin-2 (PC2), encoded by the PKD2 gene, is mutated in ~15% of autosomal dominant polycystic kidney disease. Filamins are actin-binding proteins implicated in scaffolding and membrane stabilization. Here we studied the effects of filamin on PC2 stability using filamin-deficient human melanoma M2, filamin-A (FLNA)-replete A7, HEK293 and IMCD cells together with FLNA siRNA/shRNA knockdown (KD). We found that the presence of FLNA is associated with higher total and plasma membrane PC2 protein expression. Western blotting analysis in combination with FLNA KD showed that FLNA in A7 cells represses PC2 degradation, prolonging the half-life from 2.3 to 4.4 hours. By co-immunoprecipitation and Far Western blotting we found that the FLNA C-terminus (FLNAC) reduces the FLNA-PC2 binding and PC2 expression, presumably through competing with FLNA for binding PC2. We further found that FLNA mediates PC2 binding with actin through forming complex PC2-FLNA-actin. FLNAC acted as a blocking peptide and disrupted the link of PC2 with actin through disrupting the PC2-FLNA-actin complex. Finally, we demonstrated that the physical interaction of PC2-FLNA is Ca-dependent. Taken together, our current study indicates that FLNA anchors PC2 to the actin cytoskeleton through complex PC2-FLNA-actin to reduce degradation and increase stability, and possibly regulate PC2 function in a Ca-dependent manner.     

Planar polarity

The clinical burden of both adult and neonatal lung disease worldwide is substantial; in the UK alone, respiratory disease kills one in four people. It is increasingly recognized that genes and pathways that regulate lung development, may be aberrantly activated in disease and/or reactivated as part of the lungs’ intrinsic repair mechanisms. Investigating the genes and signaling pathways that regulate lung growth has led to significant insights into the pathogenesis of congenital and adult lung disease. Recently, the planar cell polarity (PCP) pathway has been shown to be required for normal lung development, and data suggests that this signaling pathway is also involved in the pathogenesis of some lung diseases. In this review, we summarize current evidence indicating that the PCP pathway is required for both lung development and disease.     

Plasma Jet-Assisted Synthesis of Graphene Using a DC Plasma Torch

Plasma Physics Reports - Conditions of substrate-free syntheses of graphene and graphene-based systems based on conversion of liquid and gaseous carbon precursors in helium, nitrogen, and argon...     

Nonstationary Model of a Low-Density Plasma Jet Ejected from a Stationary Plasma Thruster

A time-dependent problem on finding the parameters of a low-density plasma jet ejected from a stationary plasma thruster is analyzed. In contrast to earlier works in which a stationary problem was solved using a Crook-type kinetic model, a set of kinetic equations is derived at the accuracy level accepted in the kinetic theory with allowance for resonant charge-exchange interaction between ions and neutrals. A method to solve the obtained set of equations is developed and used to perform test simulations, some results of which are presented.     

Planar polarity: photoreceptors on a high fat diet

Differential activity of Frizzled in the R3/R4 photo-receptors of Drosophila regulates the orientation of ommatidia. New evidence suggests that the cadherins Dachsous and Fat act upstream of Frizzled in this process.     

Crystal structure of a cocaine-binding antibody

Murine monoclonal antibody GNC92H2 was elicited by active immunization with a cocaine immunoconjugate and binds free cocaine with excellent specificity and moderate affinity. Improvement of affinity, as well as humanization of GNC92H2, would be advantageous in immunopharmacotherapy for cocaine addiction, and for emergency cases of drug overdose. Toward this end, the crystal structure of an engineered murine-human chimeric Fab of GNC92H2 complexed with cocaine was determined at 2.3 A resolution. Structural analysis reveals a binding pocket with high shape and charge complementarity to the cocaine framework, which explains the specificity for cocaine, as opposed to the pharmacologically inactive cocaine metabolites. Importantly, the structure provides a foundation for mutagenesis to enhance the binding affinity for cocaine and potent cocaine derivatives, such as cocaethylene, and for additional humanization of the antibody.     

Crystal Structure of a Full-Length Autotransporter

The autotransporter (AT) secretion mechanism is the most common mechanism for the secretion of virulence factors across the outer membrane (OM) from pathogenic Gram-negative bacteria. In addition, ATs have attracted biotechnological and biomedical interest for protein display on bacterial cell surfaces. Despite their importance, the mechanism by which passenger domains of ATs pass the OM is still unclear. The classical view is that the β-barrel domain provides the conduit through which the unfolded passenger moves, with the energy provided by vectorial folding of the β-strand-rich passenger on the extracellular side of the OM. We present here the first structure of a full-length AT, the esterase EstA from Pseudomonas aeruginosa, at a resolution of 2.5 Å. EstA has a relatively narrow, 12-stranded β-barrel that is covalently attached to the passenger domain via a long, curved helix that occupies the lumen of the β-barrel. The passenger has a structure that is dramatically different from that of other known passengers, with a globular fold that is dominated by α-helices and loops. The arrangement of secondary-structure elements suggests that the passenger can fold sequentially, providing the driving force for passenger translocation. The esterase active-site residues are located at the apical surface of the passenger, at the entrance of a large hydrophobic pocket that contains a bound detergent molecule that likely mimics substrate. The EstA structure provides insight into AT mechanism and will facilitate the design of fusion proteins for cell surface display.     

Crystal structures of a quorum-quenching antibody

A large number of Gram-negative bacteria employ N-acyl homoserine lactones (AHLs) as signaling molecules in quorum sensing, which is a population density-dependent mechanism to coordinate gene expression. Antibody RS2-1G9 was elicited against a lactam mimetic of the N-acyl homoserine lactone and represents the only reported monoclonal antibody that recognizes the naturally-occuring N-acyl homoserine lactone with high affinity. Due to its high cross-reactivity, RS2-1G9 showed remarkable inhibition of quorum sensing signaling in Pseudomonas aeruginosa, a common opportunistic pathogen in humans. The crystal structure of Fab RS2-1G9 in complex with a lactam analog revealed complete encapsulation of the polar lactam moiety in the antibody-combining site. This mode of recognition provides an elegant immunological solution for tight binding to an aliphatic, lipid-like ligand with a small head group lacking typical haptenic features, such as aromaticity or charge, which are often incorporated into hapten design to generate high-affinity antibodies. The ability of RS2-1G9 to discriminate between closely related AHLs is conferred by six hydrogen bonds to the ligand. Conversely, cross-reactivity of RS2-1G9 towards the lactone is likely to originate from conservation of these hydrogen bonds as well as an additional hydrogen bond to the oxygen of the lactone ring. A short, narrow tunnel exiting at the protein surface harbors a portion of the acyl chain and would not allow entry of the head group. The crystal structure of the antibody without its cognate lactam or lactone ligands revealed a considerably altered antibody-combining site with a closed binding pocket. Curiously, a completely buried ethylene glycol molecule mimics the lactam ring and, thus, serves as a surrogate ligand. The detailed structural delineation of this quorum-quenching antibody will aid further development of an antibody-based therapy against bacterial pathogens by interference with quorum sensing.     

Propagation of a Plasma Flow Generated in a Plasma-Focus Discharge in the Background Plasma

Plasma Physics Reports - The results of studying the propagation of plasma flows in the surrounding medium performed on the PF-3 plasma focus facility in the laboratory simulation of astrophysical...     

Studying How Plasma Jets are Generated in a Plasma Focus

Plasma Physics Reports - Plasma bunches with the characteristic size of approximately 1 mm and electron density larger than 1019 cm–3 are registered by the laser sounding methods on a...     

Planar polarity of ependymal cilia

Ependymal cells, epithelial cells that line the cerebral ventricles of the adult brain in various animals, extend multiple motile cilia from their apical surface into the ventricles. These cilia move rapidly, beating in a direction determined by the ependymal planar cell polarity (PCP). Ciliary dysfunction interferes with cerebrospinal fluid circulation and alters neuronal migration. In this review, we summarize recent studies on the cellular and molecular mechanisms underlying two distinct types of ependymal PCP. Ciliary beating in the direction of fluid flow is established by a combination of hydrodynamic forces and intracellular planar polarity signaling. The ciliary basal bodies' anterior position on the apical surface of the cell is determined in the embryonic radial glial cells, inherited by ependymal cells, and established by non-muscle myosin II in early postnatal development.