scholarly journals Effects of Phenylalanine on the Liquid-Expanded and Liquid-Condensed States of Phosphatidylcholine Monolayers

2019 ◽  
Vol 12 ◽  
pp. 117863531882092 ◽  
Author(s):  
Andrea C Cutro ◽  
E Anibal Disalvo ◽  
María A Frías
Keyword(s):  
Cell Membranes ◽  
Membrane Surface ◽  
Membrane Properties ◽  
Lipid Phase ◽  
Water Molecules ◽  
Brewster Angle Microscopy ◽  
Cooperative Process ◽  
High Degree ◽  
New Phase ◽  
Lipid Interaction

Background: Phenylalanine (Phe) is involved in physiological and pathological processes in cell membranes in which expanded and condensed states coexist. In this direction, it was reported that surface hydration is important for the binding affinity of the amino acid which significantly perturbs 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) monolayer structure and morphology. A deeper insight showed that Phe inserts in DPPC monolayer defects as a monomer at pH 5 and forms aggregates that adsorb to the membrane surface generating a reconfiguration of the lipid arrangement in areas of higher packing. This new arrangement in the monolayer causes the reorientation of dipoles of lipid and water molecules which is congruent with the dehydration and surface tension changes reported above. With this background, this article studies the affinity of Phe in liquid-expanded 1,2-dimyristoyl- sn-glycero-3 phosphocholine (LE DMPC) and liquid-condensed 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (LC DPPC) monolayers and their effects on membrane properties. Results: The adsorption of Phe can be described by a cooperative process in non-independent sites suggesting that Phe/lipid systems reorganize to form new structures at a high degree of coverage. Compressibility modulus and Brewster angle microscopy (BAM) images allow to propose that Phe causes a new phase in 1,2-dimyristoyl- sn-glycero-3 phosphocholine (DMPC) and DPPC. Conclusions: Phe imposes new arrangements in the lipid phase to form new structures with different compressibility behavior than lipid binary mixtures of DMPC and DPPC. Phe interaction with the LC and LE phases gives place to a process in which a synergistic effect between non-independent sites can be produced. These features of Phe/lipid interaction would be of great importance to understand the multiple effects of Phe on cell membranes.

Patterns of non-electrolyte permeability

1969 ◽  
Vol 172 (1028) ◽  
pp. 227-271 ◽  
Keyword(s):  
Partition Coefficients ◽  
Cell Membranes ◽  
Membrane Lipids ◽  
Intermolecular Forces ◽  
Lipid Phase ◽  
Water Molecules ◽  
Polar Groups ◽  
Polar Solutes ◽  
In Transit ◽  
Coupling Phenomena

Reflexion coefficients (σ’s) for epithelial cells of rabbit gall-bladder for 206 non-electrolytes have been measured and analysed. In general, σ’s decrease from 1.0 to 0 with increasing lipid :water partition coefficients, so that the intermolecular forces governing permeation of most non-electrolytes are the same as those governing partition between a bulk lipid phase and water. The two classes of deviations to this pattern are related to the specific structure of cell membranes. First, highly branched molecules have higher σ’s (permeate more slowly) than expected from partition coefficients, an effect attributed to an isotropy of membrane lipids. Secondly, the smallest, most lipid-insoluble molecules have lower σ’s (permeate more readily) than expected, and are also anomalous in that: effects of changes in their structure on or disobey Overton’s rules; the inverse relation between or and temperature is less steep for them than for other so lutes; and their σ’s are little affected by decreases in pH which increase σ’s of other solutes. These anomalies are interpreted to mean that small polar solutes in transit through the membrane interact minimally or not at all with hydrocarbon tails of membrane lipids, but in stead follow a route formed by localized concentrations of membrane polar groups associated with ‘frozen’ water molecules, where the coupling phenomena between permeating water, ions, and small polar-electrolytes observed in cell membranes may also occur.

Patterns of non-electrolyte permeability

1969 ◽  
Vol 309 (1499) ◽  
pp. 578-578
Keyword(s):  
Partition Coefficients ◽  
Cell Membranes ◽  
Membrane Lipids ◽  
Intermolecular Forces ◽  
Lipid Phase ◽  
Water Molecules ◽  
Polar Groups ◽  
Polar Solutes ◽  
In Transit ◽  
Coupling Phenomena

Reflexion coefficients (σ’s) for epithelial cells of rabbit gall-bladder for 206 non-electrolytes have been measured and analysed. In general, σ’s decrease from 1.0 to 0 with increasing lipid:water partition coefficients, so that the intermolecular forces governing permeation of most non-electrolytes are the same as those governing partition between a bulk lipid phase and water. The two classes of deviations to this pattern are related to the specific structure of cell membranes. First, highly branched molecules have higher σ's (permeate more slowly) than expected from partition coefficients, an effect attributed to anisotropy of membrane lipids. Secondly, the smallest, most lipid-insoluble molecules have lower σ’s (permeate more readily) than expected, and are also anomalous in that: effects of changes in their structure on σ disobey Overton’s rules; the inverse relation between σ and temperature is less steep for them than for other solutes; and their σ’s are little affected by decreases in pH which increase σ’s of other solutes. These anomalies are interpreted to mean that small polar solutes in transit through the membrane interact minimally or not at all with hydrocarbon tails of membrane lipids, but instead follow a route formed by localized concentrations of membrane polar groups associated with ‘frozen’ water molecules, where the coupling phenomena between permeating water, ions, and small polar-electrolytes observed in cell membranes may also occur.

Surface modification of reverse osmosis membranes with zwitterionic polymer to reduce biofouling

2015 ◽  
Vol 15 (5) ◽  
pp. 999-1010 ◽  
Author(s):  
Ahmed E. Abdelhamid ◽  
Mahmoud M. Elawady ◽  
Mahmoud Ahmed Abd El-Ghaffar ◽  
Abdelgawad M. Rabie ◽  
Poul Larsen ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Tap Water ◽  
Membrane Surface ◽  
Salt Content ◽  
Cross Flow ◽  
Membrane Properties ◽  
Cleaning Efficiency ◽  
Bacteria Growth ◽  
Cross Flow Filtration

The zwitterionic homopolymer poly[2-(methacryloyloxy)ethyl-dimethyl-(3-sulfopropyl) ammonium hydroxide was coated onto the surface of commercial polyamide reverse osmosis (RO) membranes. Aqueous solutions of the polymer at different concentrations were applied to modify the polyamide membranes through an in situ surface coating procedure. After membrane modification, cross-flow filtration testing was used to test the antifouling potential of the modified membranes. The obtained data were compared with experimental data for unmodified membranes. Each test was done by cross-flow filtering tap water for 60 hours. Yeast extract was added as a nutrient source for the naturally occurring bacteria in tap water, to accelerate bacteria growth. Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, atomic force microscopy, and permeation tests were employed to characterize membrane properties. The results confirmed that modifying the membranes enhanced their antifouling properties and cleaning efficiency, the fouling resistance to bacteria improving due to the increased hydrophilicity of the membrane surface after coating. In addition, the water permeability and salt rejection improved. This in situ surface treatment approach for RO membranes could be very important for modifying membranes in their original module assemblies as it increases water production and reduces the salt content.

scholarly journals Study of interactions between polymer nanoparticles and cell membranes at atomistic levels

2015 ◽  
Vol 370 (1661) ◽  
pp. 20140036 ◽  
Author(s):  
Chin W. Yong
Keyword(s):  
Cell Membranes ◽  
Membrane Surface ◽  
Animal Health ◽  
Md Simulations ◽  
Industrial Applications ◽  
Polymer Nanoparticles ◽  
Head Groups ◽  
Structure Of Nanoparticles ◽  
Hydrocarbon Chains ◽  
Modelling Techniques

Knowledge of how the structure of nanoparticles and the interactions with biological cell membranes is important not only for understanding nanotoxicological effects on human, animal health and the environment, but also for better understanding of nanoparticle fabrication for biomedical applications. In this work, we use molecular modelling techniques, namely molecular dynamics (MD) simulations, to explore how polymer nanoparticles interact with 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC) lipid cell membranes. Two different polymers have been considered: 100 monomer units of polyethylene (approx. 2.83 kDa) and polystyrene (approx. 10.4 kDa), both of which have wide industrial applications. We found that, despite the polar lipid head groups acting as an effective barrier to prevent the nanoparticles from interacting with the membrane surface, irreversible adhesion can be initiated by insertion of dangling chain ends from the polymer into the hydrophobic interior of the membrane. In addition, alignment of chain segments from the polymers with that of hydrocarbon chains in the interior of the membrane facilitates the complete immersion of the nanoparticles into the cell membrane. These findings highlight the importance of the surface and the topological structures of the polymer particles that dictate the absorption behaviour into the membrane and, subsequently, induce the possible translocation into the cell.

Polysulfone Activated Carbon Composite Membranes

2010 ◽  
Vol 660-661 ◽  
pp. 1081-1086 ◽  
Author(s):  
Priscila Anadão ◽  
Laís Fumie Sato ◽  
Hélio Wiebeck ◽  
Francisco Rolando Valenzuela-Díaz
Keyword(s):  
Activated Carbon ◽  
Membrane Surface ◽  
Composite Membranes ◽  
Carbon Composite ◽  
Van Der Waals Interactions ◽  
Membrane Properties ◽  
Mechanical Resistance ◽  
Scanning Electron Micrographs ◽  
Polysulfone Membrane ◽  
Hydrophilic Material

The addition of a fourth component in the system composed by polymer/ solvent/ non-solvent is a technique generally employed to enhance membrane properties. Since polysulfone presents low hydrophilicity, which can hamper filtration performance, the addition of a hydrophilic material can be an important technique to improve this property. Therefore, the main purpose of this work is to understand the influence of addition of the activated carbon in the system polysulfone/ NMP/ water in terms of membrane morphology, hydrophilicity, thermal and mechanical resistance. From scanning electron micrographs, it could be seen that membrane surface became denser with the addition of higher activated carbon contents and the cross-section morphology was not changed. Acid-base interactions were favored with the activated carbon addition and the availability of Lifshtiz-van Der Waals interactions was decreased, being these two properties very important to avoid fouling formation onto membrane surface. The glass transition temperatures of the polysulfone composite membranes with higher activated carbon contents were increased. However, all activated carbon contents brittled the composite membranes in relation to the pristine polysulfone membrane.

scholarly journals Synthesis and Characterization of a Novel Green Cationic Polyfluorene and Its Potential Use as a Fluorescent Membrane Probe

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 938 ◽  
Author(s):  
Rebeca Vázquez-Guilló ◽  
María Martínez-Tomé ◽  
Zehra Kahveci ◽  
Ivan Torres ◽  
Alberto Falco ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Membrane Surface ◽  
Aqueous Media ◽  
Coupling Reaction ◽  
Model Membranes ◽  
Lipid Phase ◽  
Fluorescent Properties ◽  
Membrane Probe ◽  
Fluorescence Efficiency ◽  
Potential Use

In the present work, we have synthesized a novel green-emitter conjugated polyelectrolyte Copoly-{[9,9-bis(6′-N,N,N-trimethylammonium)hexyl]-2,7-(fluorene)-alt-4,7-(2-(phenyl) benzo[d] [1,2,3] triazole)} bromide (HTMA-PFBT) by microwave-assisted Suzuki coupling reaction. Its fluorescent properties have been studied in aqueous media and in presence of model membranes of different composition, in order to explore its ability to be used as a green fluorescent membrane probe. The polyelectrolyte was bound with high affinity to the membrane surface, where it exhibited high fluorescence efficiency and stability. HTMA-PFBT showed lower affinity to zwitterionic membranes as compared to anionic ones, as well as a more external location, near the membrane-aqueous interface. Fluorescence microscopy studies confirmed the interaction of HTMA-PFBT with the model membranes, labelling the lipid bilayer without perturbing its morphology and showing a clear preference towards anionic systems. In addition, the polyelectrolyte was able to label the membrane of bacteria and living mammalian cells, separately. Finally, we explored if the polyelectrolyte can function also as a sensitive probe able of detecting lipid-phase transitions. All these results suggest the potential use of HTMA-PFBT as a green membrane marker for bioimaging and selective recognition of bacteria cell over mammalian ones and as a tool to monitor changes in physical state of lipid membranes.

scholarly journals Oil Deposition on Polymer Brush-Coated NF Membranes

Membranes ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 168 ◽  
Author(s):  
Anh Vu ◽  
Naama Segev Mark ◽  
Guy Z. Ramon ◽  
Xianghong Qian ◽  
Arijit Sengupta ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Polymer Brush ◽  
Operating Mode ◽  
Feed Solution ◽  
Polymer Chains ◽  
Membrane Properties ◽  
Solution Temperature ◽  
Oil Droplets ◽  
Grafted Polymer

Membrane-based processes are attractive for treating oily wastewaters. However, membrane fouling due to the deposition of oil droplets on the membrane surface compromises performance. Here, real-time observation of the deposition of oil droplets by direct confocal microscopy was conducted. Experiments were conducted in dead-end and crossflow modes. Base NF 270 nanofiltration membranes as well as membranes modified by grafting poly(N-isopropylacrylamide) chains from the membrane surface using atom transfer radical polymerization were investigated. By using feed streams containing low and high NaCl concentrations, the grafted polymer chains could be induced to switch conformation from a hydrated to a dehydrated state, as the lower critical solution temperature for the grafted polymer chains moved above and below the room temperature, respectively. For the modified membrane, it was shown that switching conformation of the grafted polymer chains led to the partial release of adsorbed oil. The results also indicate that, unlike particles such as polystyrene beads, adsorption of oil droplets can lead to coalescence of the adsorbed oil droplets on the membrane surface. The results provide further evidence of the importance of membrane properties, feed solution characteristics, and operating mode and conditions on membrane fouling.

Room temperature conversion of X0.3V2O5· nH2O phase into X2V6O16· nH2O phase Influence of the nature of the cation X+

2004 ◽  
Vol 848 ◽  
Author(s):  
Olivier Durupthy ◽  
Saïd Es-salhi ◽  
Nathalie Steunou ◽  
Thibaud Coradin ◽  
Jacques Livage
Keyword(s):  
Vanadium Oxide ◽  
Room Temperature ◽  
Interlayer Space ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Phases ◽  
New Phase ◽  
Supernatant Solution ◽  
Scanning Electron

ABSTRACTVarious cations (Li+, Na+, K+, NH4+, Cs+, Mg2+, Ca2+, Ba2+) were introduced during the formation of a V2O5. nH2O gel. Cation intercalated Xy V2O5. nH2O (y = 0.3 for X = Li+, Na+, K+, NH4+ or y = 0.15 for Mg2+, Ca2+, Ba2+) were first obtained at room temperature but some of them evolve upon ageing into a new phase: XV3O8. nH2O for X = Na+, K+, NH4+ and Cs+ or XV6O16. nH2O for X = Mg2+, Ca2+, Ba2+. All the vanadium oxide phases were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR); the supernatant solutions were analysed by 51V NMR spectroscopy. These vanadium oxide phases exhibit a layered structure with cations and water molecules intercalated within the interlayer space. The formation of the different phases depends mainly on the pH of the supernatant solution and on the nature of the cation.

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