scholarly journals Surface Characterization of Lipid Biomimetic Systems

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 821
Author(s):  
Anibal Disalvo ◽  
Maria A. Frias
Keyword(s):  
Zeta Potential ◽  
Surface Characterization ◽  
Binding Constants ◽  
Model Systems ◽  
Permeability Barrier ◽  
Dipole Potential ◽  
Interphase Region ◽  
Selective Permeability ◽  
Neutral Compounds ◽  
A Cell

Zeta potential and dipole potential measures are direct operational methodologies to determine the adsorption, insertion and penetration of ions, amphipathic and neutral compounds into the membranes of cells and model systems. From these results, the contribution of charged and dipole groups can be deduced. However, although each method may give apparent affinity or binding constants, care should be taken to interpret them in terms of physical meaning because they are not independent properties. On the base of a recent model in which the lipid bilayer is considered as composed by two interphase regions at each side of the hydrocarbon core, this review describes how dipole potential and zeta potential are correlated due to water reorganization. From this analysis, considering that in a cell the interphase region the membrane extends to the cell interior or overlaps with the interphase region of another supramolecular structure, the correlation of dipole and electrostatic forces can be taken as responsible of the propagation of perturbations between membrane and cytoplasm and vice versa. Thus, this picture gives the membrane a responsive character in addition to that of a selective permeability barrier when integrated to a complex system.

scholarly journals Permeabilization of rat hepatocytes with Staphylococcus aureus alpha-toxin.

1985 ◽  
Vol 100 (6) ◽  
pp. 1922-1929 ◽  
Author(s):  
B F McEwen ◽  
W J Arion
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Alpha Toxin ◽  
Cellular Functions ◽  
Transmembrane Channel ◽  
Selective Permeability ◽  
Treatment Conditions ◽  
Transmission Electron ◽  
A Cell

Pathogenic staphylococci secrete a number of exotoxins, including alpha-toxin. alpha-Toxin induces lysis of erythrocytes and liposomes when its 3S protein monomers associate with the lipid bilayer and form a hexomeric transmembrane channel 3 nm in diameter. We have used alpha-toxin to render rat hepatocytes 93-100% permeable to trypan blue with a lactate dehydrogenase leakage less than or equal to 22%. Treatment conditions included incubation for 5-10 min at 37 degrees C and pH 7.0 with an alpha-toxin concentration of 4-35 human hemolytic U/ml and a cell concentration of 13-21 mg dry wt/ml. Scanning electron microscopy revealed signs of swelling in the treated hepatocytes, but there were no large lesions or gross damage to the cell surface. Transmission electron microscopy indicated that the nucleus, mitochondria, and cytoplasm were similar in control and treated cells and both had large regions of well-defined lamellar rough endoplasmic reticulum. Comparisons of the mannose-6-phosphatase and glucose-6-phosphatase activities demonstrated that 5-10 U/ml alpha-toxin rendered cells freely permeable to glucose-6-phosphate, while substantially preserving the selective permeability of the membranes of the endoplasmic reticulum and the functionality of the glucose-6-phosphatase system. Thus, alpha-toxin appears to have significant potential as a means to induce selective permeability to small ions. It should make possible the study of a variety of cellular functions in situ.

Effect of Different Anions on 22Na Permeability of Liposomes

1973 ◽  
Vol 51 (11) ◽  
pp. 779-784 ◽  
Author(s):  
M. A. Singer
Keyword(s):  
Zeta Potential ◽  
Dipole Potential ◽  
Sodium Permeability ◽  
Phosphatidylcholine Liposomes ◽  
Solution Interface ◽  
Cation Permeability ◽  
Na Efflux ◽  
Negative Zeta Potential

The 22Na efflux from phosphatidylcholine liposomes was measured in the presence of different anions. Only salicylate significantly increases sodium permeability. Although this anion adsorbs onto the liposomal surface creating a negative zeta potential, evidence is presented that this is not the sole mechanism underlying the enhanced cation permeability. It is proposed that salicylate also alters the dipole potential at the membrane–solution interface.

scholarly journals Controlled Construction of Stable Network Structure Composed of Honeycomb-Shaped Microhydrogels

Life ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 38 ◽  
Author(s):  
Masayuki Hayakawa ◽  
Satoshi Umeyama ◽  
Ken Nagai ◽  
Hiroaki Onoe ◽  
Masahiro Takinoue
Keyword(s):  
Cell Communication ◽  
Model Systems ◽  
Stable Component ◽  
Photosensitive Polymer ◽  
A Cell ◽  
External Stimuli ◽  
Structural Instabilities ◽  
Insight Into ◽  
Stable Network ◽  
Microfluidic Technique

Recently, the construction of models for multicellular systems such as tissues has been attracting great interest. These model systems are expected to reproduce a cell communication network and provide insight into complicated functions in living systems./Such network structures have mainly been modelled using a droplet and a vesicle. However, in the droplet and vesicle network, there are difficulties attributed to structural instabilities due to external stimuli and perturbations. Thus, the fabrication of a network composed of a stable component such as hydrogel is desired. In this article, the construction of a stable network composed of honeycomb-shaped microhydrogels is described. We produced the microhydrogel network using a centrifugal microfluidic technique and a photosensitive polymer. In the network, densely packed honeycomb-shaped microhydrogels were observed. Additionally, we successfully controlled the degree of packing of microhydrogels in the network by changing the centrifugal force. We believe that our stable network will contribute to the study of cell communication in multicellular systems.

scholarly journals The inner membrane protein YhdP modulates the rate of anterograde phospholipid flow in Escherichia coli

2020 ◽  
Vol 117 (43) ◽  
pp. 26907-26914 ◽  
Author(s):  
Jacqueline Grimm ◽  
Handuo Shi ◽  
Wei Wang ◽  
Angela M. Mitchell ◽  
Ned S. Wingreen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Permeability Barrier ◽  
High Flux ◽  
Inner Membrane ◽  
Selective Permeability ◽  
Diffusive Flow ◽  
Molecular Machinery ◽  
Inner Membrane Protein ◽  
Uptake Of Nutrients

The outer membrane (OM) of Gram-negative bacteria is a selective permeability barrier that allows uptake of nutrients while simultaneously protecting the cell from harmful compounds. The basic pathways and molecular machinery responsible for transporting lipopolysaccharides (LPS), lipoproteins, and β-barrel proteins to the OM have been identified, but very little is known about phospholipid (PL) transport. To identify genes capable of affecting PL transport, we screened for genetic interactions with mlaA*, a mutant in which anterograde PL transport causes the inner membrane (IM) to shrink and eventually rupture; characterization of mlaA*-mediated lysis suggested that PL transport can occur via a high-flux diffusive flow mechanism. We found that YhdP, an IM protein involved in maintaining the OM permeability barrier, modulates the rate of PL transport during mlaA*-mediated lysis. Deletion of yhdP from mlaA* reduced the rate of IM transport to the OM by 50%, slowing shrinkage of the IM and delaying lysis. As a result, the weakened OM of ∆yhdP cells was further compromised and ruptured before the IM during mlaA*-mediated death. These findings demonstrate the existence of a high-flux diffusive pathway for PL flow in Escherichia coli that is modulated by YhdP.

The effect of intracellular geometry on auxin transport. I. Centrifugation experiments

1981 ◽  
Vol 214 (1194) ◽  
pp. 53-67 ◽  
Keyword(s):  
Thin Layer ◽  
High Velocity ◽  
Plant Hormone ◽  
Auxin Transport ◽  
The Other ◽  
Permeability Barrier ◽  
Cell Geometry ◽  
Internal Cell ◽  
A Cell ◽  
High Concentrations

When coleoptiles are centrifuged, the velocity of transport of the plant hormone auxin is dramatically altered. I show here that this may be due to changes in internal cell geometry. The tonoplast, the membrane surrounding the vacuole, may present a substantial permeability barrier for the diffusion of auxin. After centrifugation, the cytoplasm sediments to one end of the cell, displacing the vacuole to the other. If auxin, on entering the cell, must first accumulate in a mass of cytoplasm before crossing the tonoplast, the velocity will be lowered. If, on the other hand, there is only a thin layer of cytoplasm where auxin enters, high concentrations will quickly build up and enable auxin to cross the tonoplast, giving a high velocity. This would explain why centrifugation in a basal direction increases velocity, while apical centrifugation de­creases it. If this explanation is correct, and if the tonoplast constitutes an appreciable permeability barrier, then the position of the vacuole may strongly influence the flux of auxin inside a cell. I show in the adjoining paper that this can explain the changed transport pattern seen during the geotropic response.

Surface characterization of polymer foils

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Zdenka Kolská ◽  
Alena Řezníčková ◽  
Václav Švorčík
Keyword(s):  
Zeta Potential ◽  
Surface Characterization ◽  
Streaming Potential ◽  
Electrolyte Solutions ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Atomic Force ◽  
Contact Angle Measurements ◽  
Polymer Foils

AbstractElectrokinetic potential (zeta potential) for selected 21 polymer foils was studied. The results on zeta potential are supplemented with contact angle measurements (goniometry) and with the results on surface roughness measured by atomic force microscopy (AFM). Zeta potential was determined using two approaches: streaming current and streaming potential at pH=6.0-6.2. Two electrolyte solutions with KCl (concentrations 0.001 and 0.005 mol/dm3) and KNO3 (0.001 mol/dm3) were used in the experiments. Zeta potential was shown to depend on surface chemistry, polarity, roughness and morphology of the polymer foils.

scholarly journals A cell-based platform for oxidative stress monitoring in motor neurons using genetically encoded biosensors of H2O2

2021 ◽  
Author(s):  
Elizaveta I. Ustyantseva ◽  
Suren M. Zakian ◽  
Sergey P. Medvedev
Keyword(s):  
Oxidative Stress ◽  
Amyotrophic Lateral Sclerosis ◽  
Neurodegenerative Diseases ◽  
Motor Neurons ◽  
Model Systems ◽  
Patient Specific ◽  
Ipsc Line ◽  
Stress Monitoring ◽  
A Cell ◽  
Lateral Sclerosis

ABSTRACTBackgroundOxidative stress plays an important role in the development of neurodegenerative diseases: it either can be the initiator or part of a pathological cascade leading to the neuron’s death. Although a lot of methods are known for oxidative stress study, most of them operate on non-native cellular substrates or interfere with the cell functioning. Genetically encoded (GE) biosensors of oxidative stress demonstrated their general functionality and overall safety in various live systems. However, there is still insufficient data regarding their use for research of disease-related phenotypes in relevant model systems, such as human cells.MethodsWe applied CRISPR/Cas9 genome editing to introduce mutations (c.272A>C and c.382G>C) in the associated with amyotrophic lateral sclerosis SOD1 gene of induced pluripotent stem cells (iPSC) obtained from a healthy individual. Using CRISPR/Cas9, we modified these mutant iPSC lines, as well as the parental iPSC line, and a patient-specific SOD1D91A/D91A iPSC line with ratiometric GE biosensors of cytoplasmic (Cyto-roGFP2-Orp1) and mitochondrial (Mito-roGFP2-Orp1) H2O2. The biosensors sequences along with a specific transactivator for doxycycline-controllable expression were inserted in the “safe harbor” AAVS1 (adeno-associated virus site 1) locus. We differentiated these transgenic iPSCs into motor neurons and investigated the functionality of the biosensors in such a system. We measured relative oxidation in the cultured motor neurons and its dependence on culture conditions, age, and genotype, as well as kinetics of H2O2 elimination in real-time.ResultsWe developed a cell-based platform consisting of isogenic iPSC lines with different genotypes associated with amyotrophic lateral sclerosis. The iPSC lines were modified with GE biosensors of cytoplasmic and mitochondrial H2O2. We provide proof-of-principle data showing that this approach may be suitable for monitoring oxidative stress in cell models of various neurodegenerative diseases as the biosensors reflect the redox state of neurons.ConclusionWe found that the GE biosensors inserted in the AAVS1 locus remain functional in motor neurons and reflect pathological features of mutant motor neurons, although the readout largely depends on the severity of the mutation.

scholarly journals Codon bias determines sorting of ion channel protein

2020 ◽  
Author(s):  
Marina Kithil ◽  
Anja Jeannine Engel ◽  
Markus Langhans ◽  
Oliver Rauh ◽  
Matea Cartolano ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Secretory Pathway ◽  
Model Systems ◽  
Dependent Manner ◽  
Intracellular Proteins ◽  
Polypeptide Folding ◽  
A Cell ◽  
Identical Amino Acid Sequence ◽  
Cycle Dependent ◽  
The Impact

AbstractThe choice of codons can influence local translation kinetics during protein synthesis. The question of whether the modulation of polypeptide folding and binding to chaperons influences sorting of nascent membrane proteins remains unclear. Here, we use two similar K+ channels as model systems to examine the impact of codon choice on protein sorting. By monitoring transient expression of GFP tagged proteins in mammalian cells we find that targeting of one channel to the secretory pathway is insensitive to codon optimization. In contrast, sorting of the second channel to the mitochondria is very sensitive to codon choice. The protein with an identical amino acid sequence is sorted in a codon and cell cycle dependent manner either to mitochondria or the secretory pathway. The data establish that a gene with either rare or frequent codons serves together with a cell-state depending decoding mechanism as a secondary code for sorting intracellular proteins.

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