Showing papers on "Membrane published in 1990"
TL;DR: A methacrylate monomer having the phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC) was prepared by an improved method with good yield as mentioned in this paper.
Abstract: A methacrylate monomer having the phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC) was prepared by an improved method with good yield. MPC was copolymerized with n-butyl methacrylate (BMA). The polymer membranes were prepared from the poly(MPC-co-BMA) by a solution casting method. The membrane adsorbed water well and became a hydrogel structure even MPC mole fraction in the copolymer was 0.04. The water content of the hydrogel membrane increased with increase of MPC units and rise of temperature. These properties of the hydrogel membrane were attributed to the highly hydrophilic phospholipid polar group in the copolymer. Water soluble organic compounds and proteins whose molecular weights were below 104 permeated through the hydrogel membrane. However, the protein could not permeate when the molecular weight was higher than 105.
948 citations
TL;DR: Despite the structural complexity of integral membrane proteins, it is interesting that in some respects their study be more straightforward, lacking as they do the elusive properties of melittin which limit the possibility of defining their interaction with membranes in terms of a single conformation, location, orientation and association state within the membrane.
813 citations
01 Jan 1990
TL;DR: It appears, this novel biomolecule, biodegradable, and biocompatible, find applications in substituting or regenerating the blood/tissue interfaces.
Abstract: Chitosan [a (1----4) 2-amino-2-deoxy-beta-D-Glucan] is a unique polysaccharide derived from chitin. Several attempts have been made to use this biopolymer in biomedical field. The use of this material in the development of hemodialysis membranes, artificial skin, drug targetting and other applications are discussed. It appears, this novel biomolecule, biodegradable, and biocompatible, find applications in substituting or regenerating the blood/tissue interfaces. This polysaccharide having structural characteristics similar to glycosaminoglycans, seems to mimic their functional behaviour.
728 citations
TL;DR: In this article, the dynamics of charge recombination following electron injection from the excited state of RuL{sub 3} into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane.
Abstract: Transparent titanium dioxide membranes (thickness 2.7 {mu}m) were prepared by sintering of 8-nm colloidal anatase particles on a conducting glass support. The dynamics of charge recombination following electron injection from the excited state of RuL{sub 3} (L = 2,2{prime}-bipyridine-4,4{prime}-dicarboxylic acid) into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane. Biasing the Fermi level of the TiO{sub 2} positive of the flat-band potential sharply reduced the recombination rate, a 1,000-fold decrease being associated with a potential change of only 300 mV. Photoelectrochemical experiments performed with the same RuL{sub 3}-loaded membrane in NaI-containing water show the onset of anodic photocurrent to occur in the same potential domain. Forward biasing of the membrane potential impairs photosensitized charge injection turning on the photoluminescence of the adsorbed sensitizer.
693 citations
TL;DR: In this article, the thermally-induced solid-liquid phase separation process is discussed in terms of the solution thermodynamics of the binary mixture and the crystallization kinetics, and poly(vinylidene fluoride) membranes are presented as examples.
668 citations
TL;DR: Monensin, a monovalent ion-selective ionophore, has gained wide-spread acceptance as a tool for studying Golgi apparatus function and for localizing and identifying the molecular pathways of subcellular vesicular traffic involving acid compartments.
591 citations
TL;DR: Rapid-freezing electron microscopy was used to examine human red blood cells which were exposed to a radio-frequency electric field, and the distribution of pore sizes and pore dynamics suggests that interactions between the membrane and the submembrane cytoskeleton may have an important role in the formation and resealing of pores.
506 citations
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TL;DR: It is shown that adhering (or bound) vesicles can exhibit a large variety of different shapes and the notion of a contact angle governed by tension is found to be applicable only for a restricted subset of these shapes.
Abstract: A simple model for the adhesion of vesicles to interfaces and membranes is introduced and theoretically studied. It is shown that adhering (or bound) vesicles can exhibit a large variety of different shapes. The notion of a contact angle governed by tension is found to be applicable only for a restricted subset of these shapes. Furthermore, the vesicle undergoes a nontrivial adhesion transition from a free to a bound state. This transition is governed by the balance between the overall bending and adhesion energies, and occurs even in the absence of shape fluctuations.
467 citations
Journal Article•
TL;DR: Results indicated that net cellular uptake and retention of Tc-MIBI in fibroblasts were determined by both mitochondrial and plasma membrane potentials, which may raise the possibility of monitoring membrane potential in vivo.
Abstract: Hexakis(2-methoxyisobutylisonitrile) technetium(I) (Tc-MIBI) is representative of a class of 99mTc-based lipophilic cationic myocardial perfusion imaging agents. To test the hypothesis that the mechanism of cellular uptake may involve distribution across biologic membranes in response to membrane potential, Tc-MIBI net uptake and retention were determined in cultured mouse BALB/c 3T3, NIH 3T3, and v-src transformed NIH 3T3 fibroblasts as well as in cultured chick embryo heart cells. Isovolumic depolarization of plasma membrane potentials with 130 mM K 20 mM Cl buffer decreased Tc-MIBI net cell uptake in all preparations. In BALB/c 3T3 cells, depolarizing mitochondrial membrane potential with valinomycin in high K buffer or with the protonophore CCCP inhibited net uptake and retention of Tc-MIBI while hyperpolarizing mitochondrial and plasma membrane potentials with the K+/H+ exchanger nigericin increased Tc-MIBI net uptake. These results indicated that net cellular uptake and retention of Tc-MIBI in fibroblasts were determined by both mitochondrial and plasma membrane potentials; the gamma-emitting properties of Tc-MIBI may therefore raise the possibility of monitoring membrane potential in vivo.
446 citations
TL;DR: The spectroscopic measurements confirm the biochemical results, leading to the idea that the two populations of contact sites have different physicochemical properties, which are probably mainly determined by the membrane from which they are derived.
425 citations
TL;DR: Cross sections of NMJs showed that Ca2+ channels are clustered on the presynaptic membrane adjacent to the postsynaptic membrane, indicating that groups of Ca2- channels are localized exclusively at the active zones of the frog NMJ.
TL;DR: In this article, 1 mm thick membranes from macroporous methacrylate polymer provided with functional groups were synthetized and used for protein separation and the results show that the separation is fully comparable with that experienced on a filled column but the advantage of a membrane is up to two orders of magnitude lower pressure during the process and very high loading reaching up to 40 g/m2.
Abstract: Basing on the fact that only short layers of a chromatographic column contribute to the separation in the interaction chromatography, 1 mm thick membranes from macroporous methacrylate polymer provided with functional groups were synthetized and used for protein separation. The chromatograms show that the separation is fully comparable with that experienced on a filled column but the advantage of a membrane is up to two orders of magnitude lower pressure during the process and very high loading reaching up to 40 g/m2. This recommends the high performance membrane chromatography also for large scale preparative separations.
TL;DR: A physicochemical model based on the modified classical heterogeneous nucleation theory was proposed to analyze the ice formation inside biological cells during freezing, and a method to estimate the nucleation frequency from the observed probability of nucleation was suggested.
Abstract: A physicochemical model based on the modified classical heterogeneous nucleation theory was proposed to analyze the ice formation inside biological cells during freezing. According to this model, intracellular ice formation (IIF) may be catalyzed either by the plasma membrane via the effects of the external ice on the plasma membrane, called surface‐catalyzed nucleation (SCN), or by the intracellular particles, called volume‐catalyzed nucleation (VCN), depending on the freezing conditions. The model for IIF was coupled with the model describing the kinetics of water transport to predict the thermodynamic state of the cytoplasm.A method to estimate the nucleation frequency from the observed probability of nucleation was suggested. This method was based on the assumption that each cell has the same heteronucleating particles with identical properties to alter the nucleation kinetics in an identical way. This allowed the correlation of the experimental probability of IIF with the nucleation rate. It was sugg...
TL;DR: Analysis of the phospholipid composition of the intact mitochondria and all subfractions showed that the inner membrane was virtually devoid of phosphatidylinositol and -serine, while the outer membrane contained 23% of the total mitochondrial cardiolipin, which did not originate from inner membrane contamination and therefore is a true component of the outer membranes.
TL;DR: Use of NBD-labeled lipids as analogues of natural lipids is critically evaluated and synthetic routes for preparing the lipids, and spectroscopic and ionization properties of these probes are reviewed in this report.
TL;DR: A calcium diffusion model for a spherical neuron which incorporates calcium influx and extrusion through the plasma membrane as well as three calcium buffer systems with different capacities, mobilities, and kinetics is developed.
TL;DR: A water-insoluble silk fibroin membrane was prepared by immersing it in 50 vol% aqueous methanol solution for different periods of time at 25 degrees C to use as a biomaterial, oxygen permeability, transparency, mechanical property and enzymatic degradation behaviour in vitro of the membrane in the wet state were investigated.
TL;DR: Of the known second-messenger molecules that act within the cytosolic compartment of mammalian cells, it appears that only Ca2+ is transferred into the mitochondrial matrix.
Abstract: Many hormones and other external stimuli influence intramitochondrial metabolism (25). The mechanisms by which this occurs involve not only signal transmission across the plasma membrane but also across the inner membrane of mitochondria. This latter membrane is essentially impermeable to all charged molecules unless a specific carrier or transport system is present in the membrane. Of the known second-messenger molecules that act within the cytosolic compartment of mammalian cells, it appears that only Ca2+ is transferred into the mitochondrial matrix. The Ca2+ -transport system in the inner membrane of mitochondria (Figure 1) has separate uptake and efflux components (for reviews see 9, 14, 70). Uptake of Ca2+ occurs via an electrophoretic uniporter driven by the large electrical potential across the inner membrane. This process is inhibited by the dye ruthenium red and also by Mg2+ at concentrations likely to be present in the cytoplasm of cells (i.e. about 1 mM). The transfer of Ca2+ out of the mitochondria in heart and many other tissues occurs mainly via an e1ec-
TL;DR: In this article, a model of the direct contact membrane distillation (MD) process is presented, and flux reduction for salt is largely due to vapour pressure reduction, and for sucrose is due to increased viscosity.
TL;DR: A microscopic interaction model for a fully hydrated lipid bilayer membrane containing cholesterol is used to calculate the membrane area, the membrane hydrophobic thickness, and the average acyl-chain orientational order parameter, S, and it is pointed out that S under certain circumstances may be useful for estimating thehydrophobic membrane thickness.
TL;DR: In this paper, a novel material for separations has been developed in which efficient chromatographic particles are enmeshed in a network of PTFE fibrils to form a strong, porous sheet or "membrane".
TL;DR: Summary of the transfert of proteins across the two mitochondrial membranes and proposition a hypothesis about the physical pathway and energetics by which polypeptide chains cross the membranes.
TL;DR: Analysis of tectal membranes by two-dimensional gel electrophoresis and immunoblotting reveals a 33 kd glycoprotein that has a higher concentration in posterior than in anterior tectum, and its expression is developmentally regulated and sensitive to phosphatidylinositol-specific phospholipase C.
01 Jan 1990
TL;DR: Calcium-dependent, phosphOlipid-activated protein kinase in plants, and Auxin-resistant mutants of Arabidopsis thaliana with an altered morphology.
Abstract: s, 3rd International Meeting on Arabidopsis, p 56 Cone KC, Burr FA, Burr B (1986) Molecular analysis of the maize anthocyanin regulatory locus C I. Proc Nat! Acad Sci USA 83:9631-9635 Cosio EG, Popperl H, Schmidt WE, Ebel J (1988) High-affinity binding of fungal fJ-glucan fragments to soybean (Glycine max L.) microsomal fractions and protoplasts. Eur J Biochem 175:309-315 Damon S, Hewitt J, Neider M, Bennett AB (1988) Sink metabolism in tomato fruit. II. Phloem unloading and sugar uptake. Plant PhysioI87:731-736 Das R, Sopory SK (1985) Evidence of regulation of calcium uptake by phytochrome in maize protoplasts. Biochem Biophys Res Commun 128: 1455-1460 de Boer AH, Watson BA, Cleland RE (1989) Purification and identification ofthe fusicoccin binding protein from oat root plasma membrane. Plant PhysioI89:250-259 Delmer DP (1987) Cellulose biosynthesis. Annu Rev Plant PhysioI38:259-290 Dhugga KS, Waines JG, Leonard RT (1988) Correlated induction of nitrate uptake and membrane polypeptides in com roots. Plant PhysioI87.:120-125 Dr0bak BK, Ferguson IB (1985) Release of Ca'+ from plant hypocotyl microsomes by inositol1,4,5-triphosphate. Biochem Biophys Res Commun 130: 1241-1246 Dr0bak BK, Allan EF, Comerford JG, Roberts K, Dawson AP (1988) Presence of guanine nucleotide-binding proteins in a plant hypocotyl microsomal fraction. Biochem Biophys Res Commun 150:899-903 Elliott DC, Skinner JD (1986) Calcium-dependent, phosphOlipid-activated protein kinase in plants. Phytochemistry 25:39-44 Espie GS, Miller AG, Birch DG, Canvin DT (1988) Simultaneous transport of CO, and HCO; by the cyanobacterium Synechococcus UTEX 625. Plant PhysioI87:551-554 Estelle MA, Somerville CR (1987) Auxin-resistant mutants of Arabidopsis thaliana with an altered morphology. Mol Gen Genet 206:200-206 Ettlinger C, Lehle L (1988) Auxin induces rapid changes in phosphatidylinositol metabolites.
TL;DR: In this paper, the development of anion-exchange membranes with low electrical resistance, high selectivity and good long-term stability in strong acid or alkaline solutions is described, and the results show that these membranes are suitable for use in electrodialysis in the chemical and biochemical process industry and for the treatment of industrial waste waters.
TL;DR: The data indicate that the reticulocyte lipoxygenase can oxygenate polyenoic fatty acids in various types of biological membrane and that the oxidative modifications are not restricted to the membrane lipids.
TL;DR: A model that incorporates information about TonB‐dependent energy transduction modulated by ExbB protein, which stabilizes TonB, and possibly by several other proteins including ExbC, ExbD, and TolQ is presented.
Abstract: TonB protein serves as an energy transducer to couple cytoplasmic membrane energy to high-affinity active transport of iron siderophores and vitamin B12 across the outer membranes of Gram-negative bacteria. The biochemical mechanism of the energy transduction remains to be determined, but important details are already known. TonB is targeted to and anchored in the cytoplasmic membrane by a single membrane-spanning domain and spans the periplasm to physically interact with outer-membrane receptors of the transport ligands. TonB-dependent energy transduction is modulated by ExbB protein, which stabilizes TonB, and possibly by several other proteins including ExbC, ExbD, and TolQ. TonB has a relatively short functional half-life that is accelerated when rates of active transport across the outer membrane are increased. A model that incorporates this information, as well as some tempered speculation, is presented.
TL;DR: The structural features suggest that annexin V attaches with its convex face to membranes by specified calcium mediated interactions with at least three phospholipids, and the adjacent membrane bilayer may thus become locally disordered and permeable to allow calcium inflow through the central polar channel of the molecule.
TL;DR: In this article, improved correlations are described to correlate data on diffusivities D and the related energies of activation, and solubilities S and related heats of solution of gases in polymers.