scholarly journals Electrically silent anion transport through lipid bilayer membranes containing a long-chain secondary amine.

1978 ◽  
Vol 71 (3) ◽  
pp. 269-284 ◽  
Author(s):  
J Gutknecht ◽  
J S Graves ◽  
D C Tosteson
Keyword(s):  
Lipid Bilayers ◽  
Secondary Amine ◽  
Membrane Conductance ◽  
Transference Number ◽  
Lipid Bilayer Membranes ◽  
Zero Current ◽  
Charged Carrier ◽  
Red Cell Membranes ◽  
Ph Range ◽  
Long Chain

The permeability properties of planar lipid bilayers made from egg lecithin, n-decane and a long-chain secondary amine (n-lauryl [trialkylmethyl]amine) are described. Membranes containing the secondary amine show halide selectivity and high conductance at pH less than 6, as estimated by measurements of zero-current potentials generated by NaBr activity gradients. In the absence of halide ions, the membranes show H+ selectivity, although the total membrane conductance is relatively low. In 0.1 M NaBr both the membrane conductance (Gm) and the Br- self-exchange flux (JBr) are proportional to H+ concentration over the pH range of 7 to 4, and both JBr and Gm saturate at pH less than 4. However, JBr is always more than 100 times the flux predicted from Gm and the transference number for Br-. Thus, greater than 99% of the observed (tracer) flux is electrically silent and is not a Br2 or HBrO flux because the reducing agent, S2O3=, has no effect on JBr. At pH 7, JBr is proportional to Br- concentration over the range of 1-340 mM, with no sign of saturation kinetics. Both urea and sulfate tracer permeabilities are low and are unaffected by pH. The results can be explained by a model in which the secondary amine behaves as a monovalent, titratable carrier which exists in three chemical forms (C, CH+, and CHBr). Br- crosses the membrane primarily as the neurtal complex (CHBr). The positively charged carrier (CH+) crosses the membrane slowly compared to CHBr, but CH+ is the principal charge carrier in the membrane. At neurtal pH greater than 99% of the amine is in the nonfunctional form (C), which can be converted to CH+ or CHBr by increasing the H+ or Br- concentrations. The permeability properties of these lipid bilayers resemble in many respects the permeability properties of red cell membranes.

scholarly journals Effect of Peptide PV on the Ionic Permeability of Lipid Bilayer Membranes

1974 ◽  
Vol 63 (4) ◽  
pp. 492-508 ◽  
Author(s):  
H. P. Ting-Beall ◽  
M. T. Tosteson ◽  
B. F. Gisin ◽  
D. C. Tosteson
Keyword(s):  
Lipid Bilayers ◽  
Membrane Conductance ◽  
Equilibrium Potential ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Membrane Surfaces ◽  
Zero Current ◽  
Wide Range ◽  
Current Flows ◽  
Calculated Equilibrium

This paper reports the effects of peptide PV (primary structure: cyclo-(D-val-L-pro-L-val-D-pro)δ) on the electrical properties of sheep red cell lipid bilayers. The membrane conductance (Gm) induced by PV in either Na+ or K+ medium is proportional to the concentration of PV in the aqueous phase. The PV concentration required to produce a comparable increase in Gm in K+ medium is about 104 times greater than for its analogue, valinomycin (val). Although the selectivity sequence for PV and val is similar, K+ ≳ Rb+ > Cs+ > NH4+ > TI+ > Na+ > Li+; the ratio of GGm in K+ to that in Na+ is about 10 for PV compared to > 103 for val. When equal concentrations of PV are added to both sides of a bilayer, the membrane current approaches a maximum value independent of voltage when the membrane potential exceeds 100 mV. When PV is added to only one side of a bilayer separating identical salt solutions of either Na+ or K+ salts, rectification occurs such that the positive current flows more easily away rather than toward the side containing the carrier. Under these conditions, a large, stable, zero-current potential (VVm) is also observed, with the side containing PV being negative. The magnitude of this VVm is about 90 mV and relatively independent of PV concentration when the latter is larger than 2 Times; 10–5 M. From a model which assumes that Vm equals the equilibrium potential for the PV-cation complexes (MS+) and that the reaction between PV and cations is at equilibrium on the two membrane surfaces, we compute the permeability of the membrane to free PV to be about 10–5 cm s–1, which is about 10–7 times the permeability of similar membranes to free val. This interpretation is supported by the fact that the observed values of Vm are in agreement with the calculated equilibrium potential for MS+ over a wide range of ratios of concentrations of total PV in the two bathing solutions, if the unstirred layers are taken into account in computing the MS+ concentrations at the membrane surfaces.

Genetically Engineered Pores as Metal Ion Biosensors

1993 ◽  
Vol 330 ◽  
Author(s):  
John Kasianowicz ◽  
Barbara Walker ◽  
Musti Krishnasastry ◽  
Hagan Bayley
Keyword(s):  
Response Time ◽  
Lipid Bilayers ◽  
Metal Ion ◽  
Dynamic Range ◽  
Divalent Cations ◽  
High Sensitivity ◽  
Genetically Engineered ◽  
Great Promise ◽  
Lipid Bilayer Membranes ◽  
Time Dynamic

ABSTRACTWe are adapting proteins that form pores in lipid bilayers for use as components of biosensors. Specifically, we have produced genetically engineered variants of the α hemolysin (αHL) fromStaphylococcusaureus with properties that are sensitive to low concentrations of divalent cations. For example, the pore-forming activity of one mutant (αHL-H5: residues 130–134 inclusive replaced with histidine) is inhibited by Zn2+at concentrations as low as 1 μM, as judged by the reduction in its ability to lyse rabbit red blood cells and to increase the conductance of planar lipid bilayer membranes. When αHL-H5 is added to the aqueous phase bathing one side of a planar membrane, the subsequent addition of 100 μM Zn2+to either side blocks the pores that form. This result suggests that at least part of the mutated region lines the channel lumen. Ca2+and Mg2+do not block the channel and therefore the H5 mutation confers a degree of analyte specificity to the αHL pore. The results suggest that genetically engineered pores have great promise for the rapid and sensitive detection of metal cations and we discuss the merits and potential limitations for their use in this application. Specifically, we examine the issues of selectivity, sensitivity, response time, dynamic range and longevity. Some of these properties are interdependent. For example, the goals of high sensitivity and rapid response time can be in conflict.

Stilbene disulfonate blockade of colonic secretory Cl- channels in planar lipid bilayers

1989 ◽  
Vol 256 (4) ◽  
pp. C902-C912 ◽  
Author(s):  
R. J. Bridges ◽  
R. T. Worrell ◽  
R. A. Frizzell ◽  
D. J. Benos
Keyword(s):  
Lipid Bilayers ◽  
Single Channel ◽  
Membrane Vesicles ◽  
Kinetic Scheme ◽  
Disulfonic Acid ◽  
Lipid Bilayer Membranes ◽  
Plasma Membrane Vesicles ◽  
Open Probability ◽  
Cl Channel ◽  
Cl Channels

We studied blockade by 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS) of a secretory Cl- channel from colonic enterocyte plasma membrane vesicles incorporated into planar lipid bilayer membranes. Except for intermittent long-lived closed periods (100 ms to several min), the control channel open probability (Po) was greater than 90%. DNDS, added to the cis or vesicle-containing side, which corresponds to the outer membrane side of the channel, caused a dramatic increase in the number of current transitions from the open-to-closed state. DNDS caused a concentration-dependent decrease in Po with a maximum inhibition of 95 +/- 2.0% and a half-maximal inhibitory concentration of 3.3 +/- 1.4 microM. DNDS added to the trans side of the channel had no effect on either the single-channel conductance or kinetic behavior of the channel. Kinetic analysis revealed that DNDS blockade from the cis side could be explained by a linear, closed-open-blocked, kinetic scheme. The estimated DNDS block rate constants were kon = 3.2 X 10(7) M-1.s-1 and koff = 52 s-1, yielding an equilibrium dissociation constant (KD) of 2.1 +/- 0.38 microM, similar to the Ki for inhibition of Po. The effects of DNDS were fully reversible after perfusion of the cis compartment with DNDS-free solution. In contrast, the covalently reactive 4,4'-diisothiocyano-substituted stilbene disulfonate caused an irreversible blockade of the Cl- channel.

Membrane Disruption by Very Long Chain Fatty Acids During Necroptosis

2019 ◽  
Author(s):  
Laura Parisi ◽  
Shahin Sowlati-Hashjin ◽  
Ilyas Berhane ◽  
Kevin Carter ◽  
Jonathan Lovell ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Cell Death ◽  
Lipid Bilayers ◽  
Membrane Permeabilization ◽  
Long Chain Fatty Acids ◽  
Fatty Acid Elongase ◽  
Fatty Acylation ◽  
Dynamics Simulations ◽  
Long Chain ◽  
Chain Fatty Acids

In this work we investigate the mechanisms by which very long chain fatty acids (VLCFA) contribute to membrane permeabilization during necroptosis, a form of highly regulated necrotic cell death. We show that inactivating fatty acid elongase ELOVL7 prevents VLCFA accumulation and necroptotic cell death, while it's overexpression causes membrane permeabilization. We show that VLCFA can directly permeabilize lipid bilayers and investigate the basis of these effects by molecular dynamics simulations. Finally, we show that VLCFA can be used as substrates for protein fatty acylation during necroptosis, suggesting another potential mechanism by which VLCFA may mediate membrane permeabilization.

scholarly journals Fengycin induces ion channels in lipid bilayers mimicking target fungal cell membranes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Anastasiia A. Zakharova ◽  
Svetlana S. Efimova ◽  
Valery V. Malev ◽  
Olga S. Ostroumova
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Cell Membranes ◽  
Membrane Lipids ◽  
Electrical Potential ◽  
Membrane Conductance ◽  
Pressure Profile ◽  
Molecular Shape ◽  
Bathing Solution ◽  
Fungal Cell

Abstract The one-sided addition of fengycin (FE) to planar lipid bilayers mimicking target fungal cell membranes up to 0.1 to 0.5 μM in the membrane bathing solution leads to the formation of well-defined and well-reproducible single-ion channels of various conductances in the picosiemens range. FE channels were characterized by asymmetric conductance-voltage characteristic. Membranes treated with FE showed nonideal cationic selectivity in potassium chloride bathing solutions. The membrane conductance induced by FE increased with the second power of the lipopeptide aqueous concentration, suggesting that at least FE dimers are involved in the formation of conductive subunits. The pore formation ability of FE was not distinctly affected by the molecular shape of membrane lipids but strongly depended on the presence of negatively charged species in the bilayer. FE channels were characterized by weakly pronounced voltage gating. Small molecules known to modify the transmembrane distribution of electrical potential and the lateral pressure profile were used to modulate the channel-forming activity of FE. The observed effects of membrane modifiers were attributed to changes in lipid packing and lipopeptide oligomerization in the membrane.

Mammalian urinary bladder permeability is altered by cationic proteins: modulation by divalent cations

1994 ◽  
Vol 267 (4) ◽  
pp. C1013-C1026 ◽  
Author(s):  
C. J. Tzan ◽  
J. R. Berg ◽  
S. A. Lewis
Keyword(s):  
Urinary Bladder ◽  
Binding Site ◽  
Lipid Bilayers ◽  
Apical Membrane ◽  
Membrane Lipids ◽  
Divalent Cations ◽  
Membrane Conductance ◽  
Bladder Epithelium ◽  
Voltage Dependent ◽  
Phosphate Groups

It was previously demonstrated that protamine sulfate (PS, a cationic polypeptide) as well as synthetic cationic polypeptides (CpP, e.g., polylysine and polyarginine) caused an increase in the apical membrane conductance of the mammalian urinary bladder epithelium that was voltage dependent. The membrane conductance induced by these CpP was mediated by a saturable binding site and was partially blocked by CpP (self-inhibition). The PS-induced membrane conductance can be modified by polyvalent cations at three sites. The first site was to competitively inhibit the interaction of PS with an apical membrane binding site. The second site was to reversibly block the conductance induced by PS. The relative binding affinity (block of PS-induced conductance) sequence was as follows: UO2(2+) > La3+ > Mn2+ > Ba2+ > or = Ca2+ > Sr2+. Although La3+, Mn2+, Ba2+, Ca2+, and Sr2+ inhibited > or = 81% of the PS-induced conductance, UO2(2+) inhibited only 51% and Mg2+ was without effect. The third site was to increase the rate of loss of the PS-induced conductance from the apical membrane. Although neither carbodiimides (carboxyl group reactive reagents) nor neuraminidase (cleaves sialic acid residues) altered the effect of PS on the urinary bladder conductance, PS increased the conductance of lipid bilayers composed of negatively charged phospholipids. A candidate for the binding site might be the negatively charged phosphate groups of membrane lipids.

scholarly journals Nature of the water permeability increase induced by antidiuretic hormone (ADH) in toad urinary bladder and related tissues.

1976 ◽  
Vol 68 (2) ◽  
pp. 137-143 ◽  
Author(s):  
A Finkelstein
Keyword(s):  
Urinary Bladder ◽  
Cell Membrane ◽  
Antidiuretic Hormone ◽  
Lipid Bilayers ◽  
Water Permeability ◽  
Permeability Coefficient ◽  
Diffusion Mechanism ◽  
Toad Urinary Bladder ◽  
Lipid Bilayer Membranes ◽  
Water Permeability Coefficient

In artificial lipid bilayer membranes, the ratio of the water permeability coefficient (Pd(water)) to the permeability coefficient of an arbitrary nonelectrolyte such as n-butyramide (Pd(n-butyramide)) remains relatively constant with changes in lipid composition and temperature, even though the individual Pd's increase more than 100-fold. I propose that this is a general rule that also holds for the lipid bilayers of cells and tissues, and that therefore if Pd(water)/Pd(solute greatly exceeds the value found for artifical lipid bilayers (where "solute" is a molecule, such as 1,6 hexanediol or n-butyramide, that crosses the cell membrane by a solubility-diffusion mechanism without the aid of a special transporting system), then water crosses the cell membrane via aqueous pores. Applying this criterion to the toad urinary bladder, we find that even in the unstimulated bladder, water probably crosses the luminal membrane primarily through small aqueous pores, and that this almost certainly the case after antidiuretic hormone (ADH) stimulation. I suggest that ADH stimulation ultimately leads either to formation (or enlargement) of pores, by the rearrangement of preexisting subunits, or to an unplugging of these pores.

Sign in / Sign up

Export Citation Format

Share Document