PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 2765552

Changes in surface capacitance and conductance parallel to phospholipid membranes associated with phase transition: effects of halothane.

T Yoshida·K Taga·H Okabayashi·H Kamaya·I Ueda
View original source ↗Export metadata ↓

Abstract

The effects of phase transition on the surface capacitance and conductance parallel to dipalmitoyl- (DPPC) and dimyristoyl-phosphatidylcholine (DMPC) membranes were studied by impedance dispersion. The phospholipid aggregates were embedded into pores of a polycarbonate filter and the impedance dispersions were measured at a frequency range from 30 Hz to 1.0 MHz. When the frequency was below 120 kHz, the capacitance showed a peak at the pretransition temperature and a steep rise at the main-transition temperature. In this system, the observed capacitance consists of frequency-dependent and -independent parts. The frequency-dependent part is a surface phenomenon and arises from the lateral motion of counterions at the membrane/water interface. The frequency-independent part represents mainly the properties of the bulk lipid phase. Addition of halothane decreased the total capacitance of the DPPC aggregates at the low frequency range to 1/2 to 1/8 of the control depending upon the temperature. The surface component was solely responsible for this capacitance decrease, because the non-surface component was slightly increased instead. The data suggest that halothane inhibited the lateral ionic flow parallel to the interface.

Explore related subjects

1,2-DipalmitoylphosphatidylcholineDimyristoylphosphatidylcholineElectric ConductivityHalothaneLiposomesMathematicsModels, TheoreticalMolecular ConformationSurface PropertiesThermodynamicsJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

T Yoshida, K Taga, H Okabayashi, H Kamaya, I Ueda. 1989-09-04. Changes in surface capacitance and conductance parallel to phospholipid membranes associated with phase transition: effects of halothane.. https://doi.org/10.1016/0005-2736(89)90224-1

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Fluorescent probes alter miscibility phase boundaries in ternary vesicles.

We use 2H NMR to study the effects of probes on the miscibility transition in multilamellar vesicles of di(18:1) phosphatidylcholine (PC; DOPC), chain perdeuterated di(16:0)PC (DPPCd62), and cholesterol both with and without 0.5 mol % of the fluorescent probes DiIC12 and DiOC18. Both probes raise the miscibility transition temperature in dispersions of 1:1 DOPC/DPPCd62 + 30% cholesterol but to differing extents. In membranes containing the popular probe DiIC12, the fraction of DPPCd62 lipids in the liquid disordered phase is increased, and the ordering of that phase is reduced even at low temperatures. All findings are consistent with a probe-induced expansion of the entire miscibility phase boundary. We examine membranes with smaller DiIC12 fractions and find a significant increase in transition temperature for samples with 0.05 mol % DiIC12, demonstrating that trace components can dramatically alter membrane phase behavior.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2007

Vesicle fission of giant unilamellar vesicles of liquid-ordered-phase membranes induced by amphiphiles with a single long hydrocarbon chain.

Vesicle fissions are very important processes of biomembranes in cells, but their mechanisms are not clear and are controversial. Using the single giant unilamellar vesicle (GUV) method, we recently found that low concentrations (less than the critical micelle concentration (CMC)) of lysophosphatidylcholine (lyso-PC) induced the vesicle fission of GUVs of dipalmitoylphosphatidylcholine/cholesterol(6/4) (DPPC/chol(6/4)) membranes and sphingomyelin/cholesterol membranes (6/4) in the liquid-ordered (lo) phase. In this report, to elucidate its mechanism, we have investigated the effect of low concentrations (much less than their CMC) of other amphiphiles with a single long hydrocarbon chain (i.e., single long chain amphiphiles) on DPPC/chol(6/4) GUVs as well as the effect of the membrane composition on the lyso-PC-induced vesicle fission. We found that low concentrations of single long chain amphiphiles (lyosophosphatidic acid, octylglucoside, and sodium dodecyl sulfate) induced the shape change from a prolate to two spheres connected by a very narrow neck, indicating that the single long chain amphiphiles can be partitioned into the external monolayer in the lo phase of the GUV from the aqueous solution. As the single long chain amphiphile concentrations were increased, all of them induced vesicle fission of DPPC/chol(6/4) GUVs above their threshold concentrations. To elucidate the role of cholesterol in the single long chain amphiphile-induced vesicle fission, we investigated the effect of lyso-PC on GUVs of dioleoyl-PC (DOPC)/chol(6/4) membranes in the Lalpha phase; no vesicle fission occurred, indicating that cholesterol in itself did not play an important role in the vesicle fission. Finally, to elucidate the effect of the inclusion of DOPC in the lo-phase membrane of GUVs on the lyso-PC-induced vesicle fission of the DPPC/chol(6/4) GUV, we investigated the effect of low concentrations of lyso-PC on GUVs of DPPC/DOPC/chol membranes. With an increase in DOPC concentration in the membrane, the threshold concentration of lyso-PC increased. At and above 30 mol % DOPC, no vesicle fission occurred. On the basis of these results, we have proposed a hypothesis of the mechanism of the single long chain amphiphile-induced vesicle fission of a GUV of a lo-phase membrane.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2007

How alcohol chain-length and concentration modulate hydrogen bond formation in a lipid bilayer.

Molecular dynamics simulations are used to measure the change in properties of a hydrated dipalmitoylphosphatidylcholine bilayer when solvated with ethanol, propanol, and butanol solutions. There are eight oxygen atoms in dipalmitoylphosphatidylcholine that serve as hydrogen bond acceptors, and two of the oxygen atoms participate in hydrogen bonds that exist for significantly longer time spans than the hydrogen bonds at the other six oxygen atoms for the ethanol and propanol simulations. We conclude that this is caused by the lipid head group conformation, where the two favored hydrogen-bonding sites are partially protected between the head group choline and the sn-2 carbonyl oxygen. We find that the concentration of the alcohol in the ethanol and propanol simulations does not have a significant influence on the locations of the alcohol/lipid hydrogen bonds, whereas the concentration does impact the locations of the butanol/lipid hydrogen bonds. The concentration is important for all three alcohol types when the lipid chain order is examined, where, with the exception of the high-concentration butanol simulation, the alcohol molecules having the longest hydrogen-bonding relaxation times at the favored carbonyl oxygen acceptor sites also have the largest order in the upper chain region. The lipid behavior in the high-concentration butanol simulation differs significantly from that of the other alcohol concentrations in the order parameter, head group rotational relaxation time, and alcohol/lipid hydrogen-bonding location and relaxation time. This appears to be the result of the system being very near to a phase transition, and one occurrence of lipid flip-flop is seen at this concentration.

1,2-Dipalmitoylphosphatidylcholine↗