Search results for "Branes"
showing 10 items of 525 documents
Cholesterol Dependence of Collagen and Echovirus 1 Trafficking along the Novel α2β1 Integrin Internalization Pathway
2013
We have previously shown that soluble collagen and a human pathogen, echovirus 1 (EV1) cluster α2β1 integrin on the plasma membrane and cause their internalization into cytoplasmic endosomes. Here we show that cholesterol plays a major role not only in the uptake of α2β1 integrin and its ligands but also in the formation of α2 integrin-specific multivesicular bodies (α2-MVBs) and virus infection. EV1 infection and α2β1 integrin internalization were totally halted by low amounts of the cholesterol-aggregating drugs filipin or nystatin. Inhibition of cholesterol synthesis and accumulation of lanosterol after ketoconazole treatment inhibited uptake of collagen, virus and clustered integrin, an…
Increased gene expression of a cytokine-related molecule and profilin after activation of Suberites domuncula cells with xenogeneic sponge molecule(s)
2000
Porifera (sponges) constitute the lowest metazoan phylum, Experiments examined whether sponges can recognize self/nonself molecules. Cells from the marine sponge Suberites domuncula were incubated with membranes from either S. domuncula or another marine sponge, Geodia cydonium, as well as with recombinant alpha-integrin from G. cydonium. The cells responded immediately with a rise of intracellular Ca2+ ([Ca-i(2+)]) if they were treated with membranes from G. cydonium but not after treatment by those from S. domuncula. This change of [Ca-i(2+)] was also recorded with G. cydonium alpha-integrin. In parallel, the expression of two genes was strongly upregulated; one codes for a cytokine-relat…
Donnan equilibrium of ionic drugs in pH-dependent fixed charge membranes: theoretical modeling.
2002
Abstract We have studied theoretically the partition equilibrium of a cationic drug between an electrolyte solution and a membrane with pH-dependent fixed charges using an extended Donnan formalism. The aqueous solution within the fixed charge membrane is assumed to be in equilibrium with an external aqueous solution containing six ionic species: the cationic drug (DH + ), the salt cations (Na + and Ca 2+ ), the salt anion (Cl − ), and the hydrogen and hydroxide ions. In addition to these mobile species, the membrane solution may also contain four fixed species attached to the membrane chains: strongly acid sulfonic groups (SO 3 − ), weakly acid carboxylic groups in dissociated (COO − ) a…
Pulmonary surfactant protein C containing lipid films at the air-water interface as a model for the surface of lung alveoli.
1995
The pulmonary surfactant lines as a complex monolayer of lipids and proteins the alveolar epithelial surface. The monolayer dynamically adapts the surface tension of this interface to the varying surface areas during inhalation and exhalation. Its presence in the alveoli is thus a prerequisite for a proper lung function. The lipid moiety represents about 90% of the surfactant and contains mainly dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG). The surfactant proteins involved in the surface tension adaption are called SP-A, SP-B and SP-C. The aim of the present investigation is to analyse the properties of monolayer films made from pure SP-C and from mixtures of DPPC, DP…
Polyoxometalate Monolayers in Langmuir-Blodgett Films
2005
Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB f…
Template electrosynthesis of La(OH)3 and Nd(OH)3 nanowires using porous anodic alumina membranes
2007
High quality arrays of Ln(OH)3 (Ln = La, Nd) nanowires have been successfully fabricated for the first time by an electrochemical process using anodic alumina membrane templates. A physico-chemical characterisation of electrodeposited hydroxides has been carried out by different techniques (XRD, SEM and EDX). The results show that the synthesized nanostructures are crystalline, dense, continuous, well aligned, and with high aspect ratio, suggesting further development of possible applications in the lanthanide family species. Keywords: Nanowires, Anodic alumina membranes, Hydroxide electrodeposition, Template, Lanthanide compounds
Comments on 'formation and characterization of nanotubes of La(OH) 3 obtained using porous alumina membranes'
2010
New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membranes by cathodic polarization in 0.05 M lanthanum nitrate solution is provided to further support the conclusions previously reached in our work (Bocchetta et al 2007 Electrochem. Commun. 9 683-8) and recently criticized by González-Rovira et al (Nanotechnology 2008 19 495305). Some unconvincing aspects of the paper of González-Rovira et al, according to which the same electrochemical process should lead to the formation of hydroxycarbonate nanotubes, are also discussed.
Tunable Strong Coupling of Mechanical Resonance between Spatially Separated FePS3 Nanodrums
2021
Coupled nanomechanical resonators made of two-dimensional materials are promising for processing information with mechanical modes. However, the challenge for these types of systems is to control the coupling. Here, we demonstrate strong coupling of motion between two suspended membranes of the magnetic 2D material FePS$_3$. We describe a tunable electromechanical mechanism for control over both the resonance frequency and the coupling strength using a gate voltage electrode under each membrane. We show that the coupling can be utilized for transferring data from one drum to the other by amplitude modulation. Finally, we also study the temperature dependence of the coupling, and in particul…
Insertion of light-harvesting chlorophyll a/b protein into the thylakoid
2000
The major light-harvesting chlorophyll a/b-binding protein (Lhcb1,2) of photosystem II is inserted into the thylakoid via the signal recognition particle dependent pathway. However, the mechanism by which the protein enters the membrane is at this time unknown. In order to define some topographical restrictions for this process, we constructed several recombinant derivatives of Lhcb1 carrying hexahistidine tags at either protein terminus or in the stromal loop domain. Additionally, green fluorescent protein (GFP) was fused to either terminus. None of the modifications significantly impair the pigment-binding properties of the protein in the in vitro reconstitution of LHCII. With the excepti…
Spectrophotometric evidence for the solubilization site of betalain pigments in membrane biomimetic systems.
2007
The solubilization site of two betalain pigments, namely, betanin and indicaxantin, into l-alpha-dipalmitoyl-phosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) vesicles was investigated by a spectrophotometric study. Pigment absorbance was monitored by varying phospholipid concentration, at a constant temperature that was varied in a range including the main phase transition temperature (Tm) of the relevant phospholipid bilayer. Maximum betanin absorption increased with the increase of DPPC concentration within the entire temperature range, reaching a plateau. The binding constant (Kb) of the pigment, calculated according to a pseudo-two-phase model, varied with the temper…