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Investigation of Ion Channel Activities of Gramicidin A in the Presence of Ionic Liquids Using Model Cell Membranes.

Ryu H, Lee H, Iwata S, Choi S, Kim MK, Kim YR, Maruta S, Kim SM, Jeon TJ - Sci Rep (2015)

Bottom Line: The former effect, which increased the rate of ion flux, was dominant at high salt concentrations, whereas the latter, which decreased the rate of ion flux, was dominant at low salt concentrations.The effects of ILs increased with increasing concentration and alkyl chain length.The experimental results were further studied using molecular dynamics simulations.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Biological Engineering, Inha University, Incheon 402-751, South Korea [2] Biohybrid Systems Research Center (BSRC), Inha University, Incheon 402-751, South Korea.

ABSTRACT
Ionic liquids (ILs) are considered to be green solvents because of their non-volatility. Although ILs are relatively safe in the atmospheric environment, they may be toxic in other environments. Our previous research showed that the cytotoxicity of ILs to biological organisms is attributable to interference with cell membranes by IL insertion. However, the effects of ILs on ion channels, which play important roles in cell homeostasis, have not been comprehensively studied to date. In this work, we studied the interactions between ILs and lipid bilayer membranes with gramicidin A ion channels. We used two methods, namely electrical and fluorescence measurements of ions that permeate the membrane. The lifetimes of channels were increased by all the ILs tested in this work via stabilizing the compressed structure of the lipid bilayer and the rate of ion flux through gA channels was decreased by changing the membrane surface charge. The former effect, which increased the rate of ion flux, was dominant at high salt concentrations, whereas the latter, which decreased the rate of ion flux, was dominant at low salt concentrations. The effects of ILs increased with increasing concentration and alkyl chain length. The experimental results were further studied using molecular dynamics simulations.

No MeSH data available.


Lifetimes of gA dimer.(A) Effect of IL on gA channel reconstituted with DPhPC/n-decane lipid bilayer. Each current trace represents events prior to and after addition of 300 μM [C10 mim]Cl (applied voltage 200 mV). (B) Lifetime distribution of gA dimer depending on presence of IL. N(t) is the number of channels with lifetimes longer than time t. Blue line: C10 mim 300 μM; navy line: control. (C) Conductance transition amplitude histograms depending on presence of IL. Red: C10mim 300 μM; wine: control.
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f1: Lifetimes of gA dimer.(A) Effect of IL on gA channel reconstituted with DPhPC/n-decane lipid bilayer. Each current trace represents events prior to and after addition of 300 μM [C10 mim]Cl (applied voltage 200 mV). (B) Lifetime distribution of gA dimer depending on presence of IL. N(t) is the number of channels with lifetimes longer than time t. Blue line: C10 mim 300 μM; navy line: control. (C) Conductance transition amplitude histograms depending on presence of IL. Red: C10mim 300 μM; wine: control.

Mentions: As described previously, ILs are incorporated into the lipid bilayer16, and therefore affect the deformation free energy of the bilayer membrane, thereby altering the lifetimes of gA dimers. We used an electrical assay to measure lifetime changes of gA ion channels. Typically, gA channels have a conductance of ~14 pS in 1 M NaCl; the ion channel conductance represents the amount of ions crossing the channel per unit time for a given applied voltage, and the duration of the conductance signal represents the gA dimer lifetime. We investigated the influence of ILs on the gA dimer lifetime by measuring the signal duration when ILs at various concentrations and with different alkyl-chain lengths were added. The membrane surface charge also changes when an IL is incorporated into the membrane, because of positive charges on the IL, creating an electrostatic barrier on the membrane surface (Fig. 1A). As membrane surface charge affects ion pearmeability of gA2028, we measured the conductance of gA channels to determine the effects of surface charge to gA channels.


Investigation of Ion Channel Activities of Gramicidin A in the Presence of Ionic Liquids Using Model Cell Membranes.

Ryu H, Lee H, Iwata S, Choi S, Kim MK, Kim YR, Maruta S, Kim SM, Jeon TJ - Sci Rep (2015)

Lifetimes of gA dimer.(A) Effect of IL on gA channel reconstituted with DPhPC/n-decane lipid bilayer. Each current trace represents events prior to and after addition of 300 μM [C10 mim]Cl (applied voltage 200 mV). (B) Lifetime distribution of gA dimer depending on presence of IL. N(t) is the number of channels with lifetimes longer than time t. Blue line: C10 mim 300 μM; navy line: control. (C) Conductance transition amplitude histograms depending on presence of IL. Red: C10mim 300 μM; wine: control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507142&req=5

f1: Lifetimes of gA dimer.(A) Effect of IL on gA channel reconstituted with DPhPC/n-decane lipid bilayer. Each current trace represents events prior to and after addition of 300 μM [C10 mim]Cl (applied voltage 200 mV). (B) Lifetime distribution of gA dimer depending on presence of IL. N(t) is the number of channels with lifetimes longer than time t. Blue line: C10 mim 300 μM; navy line: control. (C) Conductance transition amplitude histograms depending on presence of IL. Red: C10mim 300 μM; wine: control.
Mentions: As described previously, ILs are incorporated into the lipid bilayer16, and therefore affect the deformation free energy of the bilayer membrane, thereby altering the lifetimes of gA dimers. We used an electrical assay to measure lifetime changes of gA ion channels. Typically, gA channels have a conductance of ~14 pS in 1 M NaCl; the ion channel conductance represents the amount of ions crossing the channel per unit time for a given applied voltage, and the duration of the conductance signal represents the gA dimer lifetime. We investigated the influence of ILs on the gA dimer lifetime by measuring the signal duration when ILs at various concentrations and with different alkyl-chain lengths were added. The membrane surface charge also changes when an IL is incorporated into the membrane, because of positive charges on the IL, creating an electrostatic barrier on the membrane surface (Fig. 1A). As membrane surface charge affects ion pearmeability of gA2028, we measured the conductance of gA channels to determine the effects of surface charge to gA channels.

Bottom Line: The former effect, which increased the rate of ion flux, was dominant at high salt concentrations, whereas the latter, which decreased the rate of ion flux, was dominant at low salt concentrations.The effects of ILs increased with increasing concentration and alkyl chain length.The experimental results were further studied using molecular dynamics simulations.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Biological Engineering, Inha University, Incheon 402-751, South Korea [2] Biohybrid Systems Research Center (BSRC), Inha University, Incheon 402-751, South Korea.

ABSTRACT
Ionic liquids (ILs) are considered to be green solvents because of their non-volatility. Although ILs are relatively safe in the atmospheric environment, they may be toxic in other environments. Our previous research showed that the cytotoxicity of ILs to biological organisms is attributable to interference with cell membranes by IL insertion. However, the effects of ILs on ion channels, which play important roles in cell homeostasis, have not been comprehensively studied to date. In this work, we studied the interactions between ILs and lipid bilayer membranes with gramicidin A ion channels. We used two methods, namely electrical and fluorescence measurements of ions that permeate the membrane. The lifetimes of channels were increased by all the ILs tested in this work via stabilizing the compressed structure of the lipid bilayer and the rate of ion flux through gA channels was decreased by changing the membrane surface charge. The former effect, which increased the rate of ion flux, was dominant at high salt concentrations, whereas the latter, which decreased the rate of ion flux, was dominant at low salt concentrations. The effects of ILs increased with increasing concentration and alkyl chain length. The experimental results were further studied using molecular dynamics simulations.

No MeSH data available.