1
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Nguyen MHL, Dziura D, DiPasquale M, Castillo SR, Kelley EG, Marquardt D. Investigating the cut-off effect of n-alcohols on lipid movement: a biophysical study. SOFT MATTER 2023. [PMID: 37357554 DOI: 10.1039/d2sm01583h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
Cellular membranes are responsible for absorbing the effects of external perturbants for the cell's survival. Such perturbants include small ubiquitous molecules like n-alcohols which were observed to exhibit anesthetic capabilities, with this effect tapering off at a cut-off alcohol chain length. To explain this cut-off effect and complement prior biochemical studies, we investigated a series of n-alcohols (with carbon lengths 2-18) and their impact on several bilayer properties, including lipid flip-flop, intervesicular exchange, diffusion, membrane bending rigidity and more. To this end, we employed an array of biophysical techniques such as time-resolved small angle neutron scattering (TR-SANS), small angle X-ray scattering (SAXS), all atomistic and coarse-grained molecular dynamics (MD) simulations, and calcein leakage assays. At an alcohol concentration of 30 mol% of the overall lipid content, TR-SANS showed 1-hexanol (C6OH) increased transverse lipid diffusion, i.e. flip-flop. As alcohol chain length increased from C6 to C10 and longer, lipid flip-flop slowed by factors of 5.6 to 32.2. Intervesicular lipid exchange contrasted these results with only a slight cut-off at alcohol concentrations of 30 mol% but not 10 mol%. SAXS, MD simulations, and leakage assays revealed changes to key bilayer properties, such as bilayer thickness and fluidity, that correlate well with the effects on lipid flip-flop rates. Finally, we tie our results to a defect-mediated pathway for alcohol-induced lipid flip-flop.
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Affiliation(s)
- Michael H L Nguyen
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
| | - Dominik Dziura
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
| | - Mitchell DiPasquale
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
| | - Stuart R Castillo
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
| | - Elizabeth G Kelley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
- Department of Physics, University of Windsor, Windsor, Ontario, Canada.
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2
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Dymond MK. A Membrane Biophysics Perspective on the Mechanism of Alcohol Toxicity. Chem Res Toxicol 2023. [PMID: 37186813 DOI: 10.1021/acs.chemrestox.3c00039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Motivations for understanding the underlying mechanisms of alcohol toxicity range from economical to toxicological and clinical. On the one hand, acute alcohol toxicity limits biofuel yields, and on the other hand, acute alcohol toxicity provides a vital defense mechanism to prevent the spread of disease. Herein the role that stored curvature elastic energy (SCE) in biological membranes might play in alcohol toxicity is discussed, for both short and long-chain alcohols. Structure-toxicity relationships for alcohols ranging from methanol to hexadecanol are collated, and estimates of alcohol toxicity per alcohol molecule in the cell membrane are made. The latter reveal a minimum toxicity value per molecule around butanol before alcohol toxicity per molecule increases to a maximum around decanol and subsequently decreases again. The impact of alcohol molecules on the lamellar to inverse hexagonal phase transition temperature (TH) is then presented and used as a metric to assess the impact of alcohol molecules on SCE. This approach suggests the nonmonotonic relationship between alcohol toxicity and chain length is consistent with SCE being a target of alcohol toxicity. Finally, in vivo evidence for SCE-driven adaptations to alcohol toxicity in the literature are discussed.
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Affiliation(s)
- Marcus K Dymond
- Chemistry Research and Enterprise Group, University of Brighton, Huxley Building, Lewes Road, Brighton BN2 4GJ, United Kingdom
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3
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Wang H, Qin H, Garab G, Gasanoff ES. Short-Chained Alcohols Make Membrane Surfaces Conducive for Melittin Action: Implication for the Physiological Role of Alcohols in Cells. Cells 2022; 11:cells11121928. [PMID: 35741057 PMCID: PMC9221640 DOI: 10.3390/cells11121928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/11/2022] [Accepted: 06/14/2022] [Indexed: 11/16/2022] Open
Abstract
Alcohols are a part of cellular metabolism, but their physiological roles are not well understood. We investigated the effects of short-chain alcohols on Daphnia pulex and model membranes mimicking the lipid composition of eukaryotic inner mitochondrial membranes. We also studied the synergistic effects of alcohols with the bee venom membrane-active peptide, melittin, which is structurally similar to endogenous membrane-active peptides. The alcohols, from ethanol to octanol, gradually decreased the heart rate and the mitochondrial ATP synthesis of daphnia; in contrast, in combination with melittin, which exerted no sizeable effect, they gradually increased both the heart rate and the ATP synthesis. Lipid packing and the order parameter of oriented films, monitored by EPR spectroscopy of the spin-labeled probe 5-doxylstrearic acid, revealed gradual alcohol-assisted bilayer to non-bilayer transitions in the presence of melittin; further, while the alcohols decreased, in combination with melittin they increased the order parameter of the film, which is attributed to the alcohol-facilitated association of melittin with the membrane. A 1H-NMR spectroscopy of the liposomes confirmed the enhanced induction of a non-bilayer lipid phase that formed around the melittin, without the permeabilization of the liposomal membrane. Our data suggest that short-chain alcohols, in combination with endogenous peptides, regulate protein functions via modulating the lipid polymorphism of membranes.
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Affiliation(s)
- Haoyu Wang
- STEM (Science, Technology, Engineering and Mathematics) Program, Science Department, Chaoyang KaiWen Academy, Beijing 100018, China; (H.W.); (H.Q.)
| | - Hao Qin
- STEM (Science, Technology, Engineering and Mathematics) Program, Science Department, Chaoyang KaiWen Academy, Beijing 100018, China; (H.W.); (H.Q.)
| | - Győző Garab
- Biological Research Centre, Eötvös Loránd Research Network, Temesvári krt. 62, H-6726 Szeged, Hungary
- Department of Physics, Faculty of Science, University of Ostrava, 710 00 Ostrava, Czech Republic
- Correspondence: (G.G.); (E.S.G.)
| | - Edward S. Gasanoff
- STEM (Science, Technology, Engineering and Mathematics) Program, Science Department, Chaoyang KaiWen Academy, Beijing 100018, China; (H.W.); (H.Q.)
- Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Correspondence: (G.G.); (E.S.G.)
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4
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Fan KK, Zhou YM, Wei Y, Han RM, Wang P, Skibsted LH, Zhang JP. Peroxyl radical induced membrane instability of giant unilamellar vesicles and anti-lipooxidation protection. Biophys Chem 2022; 285:106807. [DOI: 10.1016/j.bpc.2022.106807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/07/2022] [Accepted: 03/20/2022] [Indexed: 11/02/2022]
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5
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Klacsová M, Bóta A, Westh P, de Souza Funari S, Uhríková D, Balgavý P. Thermodynamic and structural study of DMPC-alkanol systems. Phys Chem Chem Phys 2021; 23:8598-8606. [PMID: 33876021 DOI: 10.1039/d0cp04991c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The thermodynamic and structural behaviors of lamellar dimyristoylphosphatidylcholine-alkanol (abbreviation DMPC-CnOH, n = 8-18 is the even number of carbons in the alkyl chain) systems were studied by using DSC and SAXD/WAXD methods at a 0-0.8 CnOH : DMPC molar ratio range. Up to n≤ 10 a significant biphasic effect depending on the main transition temperature tm on the CnOH concentration was observed. Two breakpoints were revealed: turning point (TP), corresponding to the minimum, and threshold concentration (cT), corresponding to the end of the biphasic tendency. These breakpoints were also observed in the alkanol concentration dependent change in the enthalpy of the main transition ΔHm. In the case of CnOHs with n > 10 we propose a marked shift of TP and cT to very low concentrations; consequently, only increase of tm is observed. A partial phase diagram was constructed for a pseudo-binary DMPC-C12OH system. We suggest a fluid-fluid immiscibility of the DMPC-C12OH system above cT with a consequent formation of domains with different C12OH contents. At a constant CnOH concentration, the effects of CnOHs on ΔHm and bilayer repeat distance were found to depend predominantly on the mismatch between CnOH and lipid chain lengths. Observed effects are suggested to be underlined by a counterbalancing effect of interchain van der Waals interactions and headgroup repulsion.
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Affiliation(s)
- Mária Klacsová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, 832 32 Bratislava, Slovakia.
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6
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Suryabrahmam B, Agrawal A, Raghunathan VA. Fluid-fluid coexistence in phospholipid membranes induced by decanol. SOFT MATTER 2020; 16:9002-9005. [PMID: 32975548 DOI: 10.1039/d0sm01417f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We have observed fluid-fluid coexistence in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane containing 1-decanol, using different experimental techniques and membrane morphologies. This phase behavior is reversible and occurs over a temperature range just above the chain melting transition temperature of the membrane. Although earlier experimental studies and computer simulations have shown the ability of decanol to enhance lipid chain ordering, its potential to induce fluid-fluid coexistence in membranes has not been hitherto recognized. Being the only binary membrane system known so far to exhibit fluid-fluid coexistence, the present system can serve as a simple model to gain a better understanding of mechanisms that drive this unusual phase behavior, which is believed to play an important role in the functioning of cell membranes.
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7
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Mironov KS, Kupriyanova EV, Shumskaya M, Los DA. Alcohol stress on cyanobacterial membranes: New insights revealed by transcriptomics. Gene 2020; 764:145055. [PMID: 32882332 DOI: 10.1016/j.gene.2020.145055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/22/2020] [Accepted: 08/12/2020] [Indexed: 11/18/2022]
Abstract
Cyanobacteria are model photosynthetic prokaryotic organisms often used in biotechnology to produce biofuels including alcohols. The effect of alcohols on cyanobacterial cell physiology and specifically on membrane fluidity is poorly understood. Previous research on various primary aliphatic alcohols found that alcohols with a short hydrocarbon chain (C1-C3) do not affect expression of genes related to membrane physical state. In addition, less water-soluble alcohols with a hydrocarbon chain longer than C8 are found to have a reduced ability to reach cellular membranes hence do not drastically change membrane physical state or induce expression of stress-responsive genes. Therefore, hexan-1-ol (C6) is suggested to have the most profound effect on cyanobacterial membrane physical state. Here, we studied the effects of hexan-1-ol on the cyanobacterium Synechocystis sp. PCC 6803 transcriptome. The transcriptome data obtained is compared to the previously reported analysis of gene expression induced by benzyl alcohol and butan-1-ol. The set of genes whose expression is induced after exposure to all three studied alcohols is identified. The expression under alcohol stress for several general stress response operons is analyzed, and examples of antisense interactions of RNA are investigated.
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Affiliation(s)
- Kirill S Mironov
- Department of Molecular Biosystems, K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Science, Botanicheskaya str., 35, Moscow 127276, Russian Federation.
| | - Elena V Kupriyanova
- Department of Molecular Biosystems, K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Science, Botanicheskaya str., 35, Moscow 127276, Russian Federation
| | - Maria Shumskaya
- Department of Biology, School of Natural Sciences, Kean University, 1000 Morris Ave, Union, NJ 07083, USA
| | - Dmitry A Los
- Department of Molecular Biosystems, K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Science, Botanicheskaya str., 35, Moscow 127276, Russian Federation
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8
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Yang A, Moore TC, Iacovella CR, Thompson M, Moore DJ, McCabe C. Examining Tail and Headgroup Effects on Binary and Ternary Gel-Phase Lipid Bilayer Structure. J Phys Chem B 2020; 124:3043-3053. [PMID: 32196346 DOI: 10.1021/acs.jpcb.0c00490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The structural properties of two- and three-component gel-phase bilayers were studied using molecular dynamics simulations. The bilayers contain distearoylphosphatidylcholine (DSPC) phospholipids mixed with alcohols and/or fatty acids of varying tail lengths, with carbon chain lengths of 12, 16, and 24 studied. Changes in both headgroup chemistry and tail length are found to affect the balance between steric repulsion and van der Waals attraction within the bilayers, manifesting in different bilayer structural properties. Lipid components are found to be located at different depths within the bilayer depending on both chain length and headgroup chemistry. The highest bilayer ordering and lowest area per tail are found in systems with medium-length tails. While longer tails can enhance van der Waals attractions, the increased tail-length asymmetry is found to induce disorder and reduce tail packing. Bulkier headgroups further increase steric repulsion, as reflected in increased component offsets and reduced tail packing. These findings help explain how bilayer composition affects the structure of gel-phase bilayers.
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Affiliation(s)
- Alexander Yang
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Timothy C Moore
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Christopher R Iacovella
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Michael Thompson
- GlaxoSmithKline Consumer Health Care, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - David J Moore
- GlaxoSmithKline Consumer Health Care, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - Clare McCabe
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States.,Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37212, United States
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9
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Susceptibility of biomembrane structure towards amphiphiles, ionic liquids, and deep eutectic solvents. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2020. [DOI: 10.1016/bs.abl.2020.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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10
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Neupane S, Cordoyiannis G, Renner FU, Losada-Pérez P. Real-Time Monitoring of Interactions between Solid-Supported Lipid Vesicle Layers and Short- and Medium-Chain Length Alcohols: Ethanol and 1-Pentanol. Biomimetics (Basel) 2019; 4:biomimetics4010008. [PMID: 31105194 PMCID: PMC6477617 DOI: 10.3390/biomimetics4010008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 01/10/2019] [Accepted: 01/16/2019] [Indexed: 11/21/2022] Open
Abstract
Lipid bilayers represent the interface between the cell and its environment, serving as model systems for the study of various biological processes. For instance, the addition of small molecules such as alcohols is a well-known process that modulates lipid bilayer properties, being considered as a reference for general anesthetic molecules. A plethora of experimental and simulation studies have focused on alcohol’s effect on lipid bilayers. Nevertheless, most studies have focused on lipid membranes formed in the presence of alcohols, while the effect of n-alcohols on preformed lipid membranes has received much less research interest. Here, we monitor the real-time interaction of short-chain alcohols with solid-supported vesicles of dipalmitoylphosphatidylcholine (DPPC) using quartz crystal microbalance with dissipation monitoring (QCM-D) as a label-free method. Results indicate that the addition of ethanol at different concentrations induces changes in the bilayer organization but preserves the stability of the supported vesicle layer. In turn, the addition of 1-pentanol induces not only changes in the bilayer organization, but also promotes vesicle rupture and inhomogeneous lipid layers at very high concentrations.
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Affiliation(s)
- Shova Neupane
- Institute for Materials Research (IMO), Hasselt University, 3590 Diepenbeek, Belgium.
- IMEC vzw. Division IMOMEC, 3590 Diepenbeek, Belgium.
| | - George Cordoyiannis
- Faculty for Industrial Engineering, 8000 Novo Mesto, Slovenia.
- Biomolecular Physics Laboratory, National Centre for Scientific Research "Demokritos", 15310 Aghia Paraskevi, Greece.
| | - Frank Uwe Renner
- Institute for Materials Research (IMO), Hasselt University, 3590 Diepenbeek, Belgium.
- IMEC vzw. Division IMOMEC, 3590 Diepenbeek, Belgium.
| | - Patricia Losada-Pérez
- Soft Matter Physics Laboratory, Physics Department, Université Libre de Bruxelles (ULB), Campus de La Plaine, CP223, Boulevard du Triomphe, 1050 Brussels, Belgium.
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11
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Difference in molecular mechanisms governing changes in membrane properties of phospholipid bilayers induced by addition of nonionic and zwitterionic surfactants. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.09.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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12
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Vaňousová K, Beranová J, Fišer R, Jemioła-Rzemińska M, Matyska Lišková P, Cybulski L, Strzałka K, Konopásek I. Membrane fluidization by alcohols inhibits DesK-DesR signalling in Bacillus subtilis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:718-727. [DOI: 10.1016/j.bbamem.2017.12.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 12/13/2017] [Accepted: 12/15/2017] [Indexed: 11/24/2022]
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13
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Raškevičius V, Jotautis V, Rimkutė L, Marandykina A, Kazokaitė M, Kairys V, Skeberdis VA. Molecular basis for potentiation of Cx36 gap junction channel conductance by n-alcohols and general anesthetics. Biosci Rep 2018; 38:BSR20171323. [PMID: 29298877 PMCID: PMC5803492 DOI: 10.1042/bsr20171323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/22/2017] [Accepted: 01/01/2018] [Indexed: 01/01/2023] Open
Abstract
In our recent study, we have demonstrated that short carbon chain n-alcohols (up to octanol) stimulated while long carbon chain n-alcohols inhibited the conductance of connexin (Cx) 36 (Cx36) gap junction (GJ) channels. In contrast, GJ channels composed of other types of Cxs all were inhibited by n-alcohols independent of their carbon chain length. To identify the putative structural domains of Cx36, responsible for the dual effect of n-alcohols, we performed structural modeling of Cx36 protein docking with hexanol and isoflurane that stimulated as well as nonanol and carbenoxolone that inhibited the conductance of Cx36 GJs and revealed their multiple common docking sites and a single pocket accessible only to hexanol and isoflurane. The pocket is located in the vicinity of three unique cysteine residues, namely C264 in the fourth, and C92 and C87 in the second transmembrane domain of the neighboring Cx36 subunits. To examine the hypothesis that disulphide bonding might be involved in the stimulatory effect of hexanol and isoflurane, we generated cysteine substitutions in Cx36 and demonstrated by a dual whole-cell patch-clamp technique that in HeLa (human cervix carcinoma cell line) and N2A (mouse neuroblastoma cell line) cells these mutations reversed the stimulatory effect of hexanol and isoflurane to inhibitory one, typical of other Cxs that lack respective cysteines and a specific docking pocket for these compounds. Our findings suggest that the stimulatory effect of hexanol and isoflurane on Cx36 GJ conductance could be achieved by re-shuffling of the inter-subunit disulphide bond between C264 and C92 to the intra-subunit one between C264 and C87.
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Affiliation(s)
- Vytautas Raškevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Vaidas Jotautis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Lina Rimkutė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Alina Marandykina
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Mintautė Kazokaitė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Visvaldas Kairys
- Institute of Biotechnology, Vilnius University, Vilnius LT-10257, Lithuania
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14
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Melo M, Arnarez C, Sikkema H, Kumar N, Walko M, Berendsen HJC, Kocer A, Marrink SJ, Ingólfsson HI. High-Throughput Simulations Reveal Membrane-Mediated Effects of Alcohols on MscL Gating. J Am Chem Soc 2017; 139:2664-2671. [PMID: 28122455 PMCID: PMC5343553 DOI: 10.1021/jacs.6b11091] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Indexed: 12/18/2022]
Abstract
The mechanosensitive channels of large conductance (MscL) are bacterial membrane proteins that serve as last resort emergency release valves in case of severe osmotic downshock. Sensing bilayer tension, MscL channels are sensitive to changes in the bilayer environment and are, therefore, an ideal test case for exploring membrane protein coupling. Here, we use high-throughput coarse-grained molecular dynamics simulations to characterize MscL gating kinetics in different bilayer environments under the influence of alcohols. We performed over five hundred simulations to obtain sufficient statistics to reveal the subtle effects of changes in the membrane environment on MscL gating. MscL opening times were found to increase with the addition of the straight-chain alcohols ethanol, octanol, and to some extent dodecanol but not with hexadecanol. Increasing concentration of octanol increased the impeding effect, but only up to 10-20 mol %. Our in silico predictions were experimentally confirmed using reconstituted MscL in a liposomal fluorescent efflux assay. Our combined data reveal that the effect of alcohols on MscL gating arises not through specific binding sites but through a combination of the alcohol-induced changes to a number of bilayer properties and their alteration of the MscL-bilayer interface. Our work provides a key example of how extensive molecular simulations can be used to predict the functional modification of membrane proteins by subtle changes in their bilayer environment.
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Affiliation(s)
- Manuel
N. Melo
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
| | - Clément Arnarez
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
| | - Hendrik Sikkema
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
| | - Neeraj Kumar
- Groningen
Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Martin Walko
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Herman J. C. Berendsen
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
| | - Armagan Kocer
- Department
of Neuroscience, University Medical Center
Groningen, University of Groningen, Antonius Deusinglaan 1, 99713 AV, Groningen, The
Netherlands
| | - Siewert J. Marrink
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
| | - Helgi I. Ingólfsson
- Groningen
Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, 9747 AG, Groningen, The Netherlands
- Biosciences
and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California
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15
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Hartkamp R, Moore TC, Iacovella CR, Thompson MA, Bulsara PA, Moore DJ, McCabe C. Structural Properties of Phospholipid-based Bilayers with Long-Chain Alcohol Molecules in the Gel Phase. J Phys Chem B 2016; 120:12863-12871. [DOI: 10.1021/acs.jpcb.6b10192] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Remco Hartkamp
- Department
of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States
- Multiscale
Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Timothy C. Moore
- Department
of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States
- Multiscale
Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Christopher R. Iacovella
- Department
of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States
- Multiscale
Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Michael A. Thompson
- GlaxoSmithKline Consumer Healthcare, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - Pallav A. Bulsara
- GlaxoSmithKline Consumer Healthcare, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - David J. Moore
- GlaxoSmithKline Consumer Healthcare, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - Clare McCabe
- Department
of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States
- Multiscale
Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee 37212, United States
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37212, United States
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16
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Gallo V, Stano P, Luisi PL. Protein Synthesis in Sub-Micrometer Water-in-Oil Droplets. Chembiochem 2016; 16:2073-9. [PMID: 26376303 DOI: 10.1002/cbic.201500274] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 11/07/2022]
Abstract
Water-in-oil (w/o) emulsions are used as a cellular model because of their unique cell-like architecture. Previous works showed the capability of eukaryotic-cell-sized w/o droplets (5-50 μm) to support protein synthesis efficiently; however data about smaller w/o compartments (<1 μm) are lacking. This work focuses on the biosynthesis of the enhanced green fluorescent protein (EGFP) inside sub-micrometric lecithin-based w/o droplets (0.8-1 μm) and on its dependence on the compartments' dynamic properties in terms of solute exchange mechanisms. We demonstrated that protein synthesis is strongly affected by the nature of the lipid interface. These findings could be of value and interest for both basic and applied research.
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Affiliation(s)
- Valentina Gallo
- Science Department, Roma Tre University, Viale Guglielmo Marconi 446, 00146, Rome, Italy
| | - Pasquale Stano
- Science Department, Roma Tre University, Viale Guglielmo Marconi 446, 00146, Rome, Italy
| | - Pier Luigi Luisi
- Science Department, Roma Tre University, Viale Guglielmo Marconi 446, 00146, Rome, Italy.
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17
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Meulenberg CJW, de Groot A, Westerink RHS, Vijverberg HPM. Organic solvent-induced changes in membrane geometry in human SH-SY5Y neuroblastoma cells - a common narcotic effect? Neurotoxicology 2016; 55:74-82. [PMID: 27235192 DOI: 10.1016/j.neuro.2016.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 05/11/2016] [Accepted: 05/20/2016] [Indexed: 10/21/2022]
Abstract
Exposure to organic solvents may cause narcotic effects. At the cellular level, these narcotic effects have been associated with a reduction in neuronal excitability caused by changes in membrane structure and function. In order to critically test whether changes in membrane geometry contribute to these narcotic effects, cultured human SH-SY5Y neuroblastoma cells have been exposed to selected organic solvents. The solvent-induced changes in cell membrane capacitance were investigated using the whole-cell patch clamp technique for real-time capacitance measurements. Exposure of SH-SY5Y cells to the cyclic hydrocarbons m-xylene, toluene, and cyclohexane caused a rapid and reversible increase of membrane capacitance. The aliphatic, nonpolar n-hexane did not cause a detectable change of whole-cell membrane capacitance, whereas the amphiphiles n-hexanol and n-hexylamine caused an increase of membrane capacitance and a concomitant reduction in membrane resistance. Despite a large difference in dielectric properties, the chlorinated hydrocarbons 1,1,2,2-tetrachoroethane and tetrachloroethylene caused a similar magnitude increase in membrane capacitance. The theory on membrane capacitance has been applied to deduce changes in membrane geometry caused by solvent partitioning. Although classical observations have shown that solvents increase the membrane capacitance per unit area of membrane, i.e., increase membrane thickness, the present results demonstrate that solvent partitioning predominantly leads to an increase in membrane surface area and to a lesser degree to an increase in membrane thickness. Moreover, the present results indicate that the physicochemical properties of each solvent are important determinants for its specific effects on membrane geometry. This implies that the hypothesis that solvent partitioning is associated with a common perturbation of membrane structure needs to be revisited and cannot account for the commonly observed narcotic effects of different organic solvents.
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Affiliation(s)
- Cécil J W Meulenberg
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, PO Box 80.177, NL 3508 TD Utrecht, The Netherlands.
| | - Aart de Groot
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, PO Box 80.177, NL 3508 TD Utrecht, The Netherlands
| | - Remco H S Westerink
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, PO Box 80.177, NL 3508 TD Utrecht, The Netherlands
| | - Henk P M Vijverberg
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, PO Box 80.177, NL 3508 TD Utrecht, The Netherlands
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18
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Musgrove A, Bizzotto D. Potential Controls the Interaction of Liposomes with Octadecanol-Modified Au Electrodes: An in Situ AFM Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12797-12806. [PMID: 26528884 DOI: 10.1021/acs.langmuir.5b03605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The formation of supported lipid bilayers using liposomes requires interaction with the solid surface, rupture of the liposome, and spreading to cover the surface with a lipid bilayer. This can result in a less-than-uniform coating of the solid surface. Presented is a method that uses the electrochemical poration of an adsorbed lipid-like layer on a Au electrode to control the interaction of 100 nm DOPC liposomes. An octadecanol-coated Au-on-mica surface was imaged using tapping-mode AFM during the application of potential in the presence or absence of liposomes. When the substrate potential was made negative enough, defects formed in the adsorbed layer and new taller features were observed. More features were observed and existing features increased in size with time spent at this negative poration potential. The new features were 1.8-2.0 nm higher than the octadecanol-coated gold surface, half the thickness of a DOPC bilayer. These features were not observed in the absence of liposomes when undergoing the same potential perturbation. In the presence of liposomes, the application of a poration potential was needed to initiate the formation of these taller features. Once the applied potential was removed, the features stopped growing and no new regions were observed. The size of these new regions was consistent with the footprint of a flattened 100 nm liposome. It is speculated that the DOPC liposomes were able to interact with the defects and became soluble in the octadecanol, creating a taller region that was limited in size to the liposome that adsorbed and became incorporated. This AFM study confirms previous in situ fluorescence measurements of the same system and illustrates the use of a potential perturbation to control the formation of these regions of increased DOPC content.
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Affiliation(s)
- Amanda Musgrove
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
| | - Dan Bizzotto
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
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19
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Hishida M, Endo A, Nakazawa K, Yamamura Y, Saito K. Effect of n-alkanes on lipid bilayers depending on headgroups. Chem Phys Lipids 2015; 188:61-7. [PMID: 25957868 DOI: 10.1016/j.chemphyslip.2015.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 04/28/2015] [Accepted: 05/04/2015] [Indexed: 10/23/2022]
Abstract
Phase behavior and structural properties were examined for phospholipid bilayers having different headgroups (DMPC, DMPS and DMPE) with added n-alkanes to study effect of flexible additives. Change in the temperatures of main transition of the lipid/alkane mixtures against the length of added alkanes depends largely on the headgroup. Theoretical analysis of the change of the temperature of transition indicates that the headgroup dependence is dominantly originated in the strong dependence of total enthalpy on the headgroups. The results of X-ray diffraction show that the enthalpic stabilization due to enhanced packing of acyl chains of the lipid by alkanes in the gel phase causes the headgroup-dependent change in the phase transition behavior. The enhanced packing in the gel phase also leads to easy emergence of the subgel phase with very short relaxation time at room temperature in the DMPE-based bilayers.
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Affiliation(s)
- Mafumi Hishida
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Asami Endo
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Koyomi Nakazawa
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Yasuhisa Yamamura
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Kazuya Saito
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
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20
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Permeability of the Blood–Brain Barrier: Molecular Mechanism of Transport of Drugs and Physiologically Important Compounds. J Membr Biol 2015; 248:651-69. [DOI: 10.1007/s00232-015-9778-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 01/23/2015] [Indexed: 01/08/2023]
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21
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Herold KF, Sanford RL, Lee W, Schultz MF, Ingólfsson HI, Andersen OS, Hemmings HC. Volatile anesthetics inhibit sodium channels without altering bulk lipid bilayer properties. J Gen Physiol 2014; 144:545-60. [PMID: 25385786 PMCID: PMC4242807 DOI: 10.1085/jgp.201411172] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023] Open
Abstract
Although general anesthetics are clinically important and widely used, their molecular mechanisms of action remain poorly understood. Volatile anesthetics such as isoflurane (ISO) are thought to alter neuronal function by depressing excitatory and facilitating inhibitory neurotransmission through direct interactions with specific protein targets, including voltage-gated sodium channels (Na(v)). Many anesthetics alter lipid bilayer properties, suggesting that ion channel function might also be altered indirectly through effects on the lipid bilayer. We compared the effects of ISO and of a series of fluorobenzene (FB) model volatile anesthetics on Na(v) function and lipid bilayer properties. We examined the effects of these agents on Na(v) in neuronal cells using whole-cell electrophysiology, and on lipid bilayer properties using a gramicidin-based fluorescence assay, which is a functional assay for detecting changes in lipid bilayer properties sensed by a bilayer-spanning ion channel. At clinically relevant concentrations (defined by the minimum alveolar concentration), both the FBs and ISO produced prepulse-dependent inhibition of Na(v) and shifted the voltage dependence of inactivation toward more hyperpolarized potentials without affecting lipid bilayer properties, as sensed by gramicidin channels. Only at supra-anesthetic (toxic) concentrations did ISO alter lipid bilayer properties. These results suggest that clinically relevant concentrations of volatile anesthetics alter Na(v) function through direct interactions with the channel protein with little, if any, contribution from changes in bulk lipid bilayer properties. Our findings further suggest that changes in lipid bilayer properties are not involved in clinical anesthesia.
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Affiliation(s)
- Karl F Herold
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - R Lea Sanford
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - William Lee
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Margaret F Schultz
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Helgi I Ingólfsson
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Olaf S Andersen
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Hugh C Hemmings
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065 Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
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22
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Ngo AT, Jakubek ZJ, Lu Z, Joós B, Morris CE, Johnston LJ. Membrane order parameters for interdigitated lipid bilayers measured via polarized total-internal-reflection fluorescence microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2861-9. [PMID: 25073072 DOI: 10.1016/j.bbamem.2014.07.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/03/2014] [Accepted: 07/21/2014] [Indexed: 12/25/2022]
Abstract
Incorporating ethanol in lipid membranes leads to changes in bilayer structure, including the formation of an interdigitated phase. We have used polarized total-internal-reflection fluorescence microscopy (pTIRFM) to measure the order parameter for Texas Red DHPE incorporated in the ethanol-induced interdigitated phase (LβI) formed from ternary lipid mixtures comprising dioleoylphosphatidylcholine, cholesterol and egg sphingomyelin or dipalmitoylphosphatidylcholine. These lipid mixtures have 3 co-existing phases in the presence of ethanol: liquid-ordered, liquid-disordered and LβI. pTIRFM using Texas Red DHPE shows a reversal in fluorescence contrast between the LβI phase and the surrounding disordered phase with changes in the polarization angle. The contrast reversal is due to changes in the orientation of the dye, and provides a rapid method to identify the LβI phase. The measured order parameters for the LβI phase are consistent with a highly ordered membrane environment, similar to a gel phase. An acyl-chain labeled BODIPY-FL-PC was also tested for pTIRFM studies of ethanol-treated bilayers; however, this probe is less useful since the order parameters of the interdigitated phase are consistent with orientations that are close to random, either due to local membrane disorder or to a mixture of extended and looping conformations in which the fluorophore is localized in the polar headgroup region of the bilayer. In summary, we demonstrate that order parameter measurements via pTIRFM using Texas Red-DHPE can rapidly identify the interdigitated phase in supported bilayers. We anticipate that this technique will aid further research in the effects of alcohols and other additives on membranes.
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Affiliation(s)
- An T Ngo
- Measurement Science and Standards, National Research Council Canada, Ottawa, ON K1A 0R6, Canada; Department of Physics, University of Ottawa Ottawa, ON K1N 6N5, Canada
| | - Zygmunt J Jakubek
- Measurement Science and Standards, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | - Zhengfang Lu
- Measurement Science and Standards, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | - Béla Joós
- Department of Physics, University of Ottawa Ottawa, ON K1N 6N5, Canada
| | | | - Linda J Johnston
- Measurement Science and Standards, National Research Council Canada, Ottawa, ON K1A 0R6, Canada.
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23
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Belička M, Klacsová M, Karlovská J, Westh P, Devínsky F, Balgavý P. Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers. Chem Phys Lipids 2014; 180:1-6. [DOI: 10.1016/j.chemphyslip.2014.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Revised: 02/19/2014] [Accepted: 02/21/2014] [Indexed: 11/28/2022]
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24
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Murugova TN, Balgavý P. Molecular volumes of DOPC and DOPS in mixed bilayers of multilamellar vesicles. Phys Chem Chem Phys 2014; 16:18211-6. [DOI: 10.1039/c4cp01980f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Specific volume of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phospho-l-serine mixtures in bilayers linearly depends on the molar fraction of the constituents, indicating an ideal volume mixing.
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Affiliation(s)
- T. N. Murugova
- Frank Laboratory of Neutron Physics
- Joint Institute for Nuclear Research
- 141980 Dubna, Russia
- Moscow Institute of Physics and Technology
- 141700 Dolgoprudny, Russia
| | - P. Balgavý
- Department of Physical Chemistry of Drugs
- Faculty of Pharmacy
- Comenius University
- 832 32 Bratislava, Slovakia
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25
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Rusinova R, Hobart EA, Koeppe RE, Andersen OS. Phosphoinositides alter lipid bilayer properties. ACTA ACUST UNITED AC 2013; 141:673-90. [PMID: 23712549 PMCID: PMC3664701 DOI: 10.1085/jgp.201310960] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Phosphatidylinositol-4,5-bisphosphate (PIP2), which constitutes ∼1% of the plasma membrane phospholipid, plays a key role in membrane-delimited signaling. PIP2 regulates structurally and functionally diverse membrane proteins, including voltage- and ligand-gated ion channels, inwardly rectifying ion channels, transporters, and receptors. In some cases, the regulation is known to involve specific lipid–protein interactions, but the mechanisms by which PIP2 regulates many of its various targets remain to be fully elucidated. Because many PIP2 targets are membrane-spanning proteins, we explored whether the phosphoinositides might alter bilayer physical properties such as curvature and elasticity, which would alter the equilibrium between membrane protein conformational states—and thereby protein function. Taking advantage of the gramicidin A (gA) channels’ sensitivity to changes in lipid bilayer properties, we used gA-based fluorescence quenching and single-channel assays to examine the effects of long-chain PIP2s (brain PIP2, which is predominantly 1-stearyl-2-arachidonyl-PIP2, and dioleoyl-PIP2) on bilayer properties. When premixed with dioleoyl-phosphocholine at 2 mol %, both long-chain PIP2s produced similar changes in gA channel function (bilayer properties); when applied through the aqueous solution, however, brain PIP2 was a more potent modifier than dioleoyl-PIP2. Given the widespread use of short-chain dioctanoyl-phosphoinositides, we also examined the effects of diC8-phosphoinositol (PI), PI(4,5)P2, PI(3,5)P2, PI(3,4)P2, and PI(3,4,5)P3. The diC8 phosphoinositides, except for PI(3,5)P2, altered bilayer properties with potencies that decreased with increasing head group charge. Nonphosphoinositide diC8 phospholipids generally were more potent bilayer modifiers than the polyphosphoinositides. These results show that physiological increases or decreases in plasma membrane PIP2 levels, as a result of activation of PI kinases or phosphatases, are likely to alter lipid bilayer properties, in addition to any other effects they may have. The results further show that exogenous PIP2, as well as structural analogues that differ in acyl chain length or phosphorylation state, alters lipid bilayer properties at the concentrations used in many cell physiological experiments.
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Affiliation(s)
- Radda Rusinova
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA.
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26
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Soto-Arriaza M, Olivares-Ortega C, Lissi E. Effect of the addition of alkanols of different topology to dipalmitoyl-phosphatidylcholine vesicles in the presence of gramicidin. J Colloid Interface Sci 2012; 385:48-57. [DOI: 10.1016/j.jcis.2012.07.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 07/06/2012] [Accepted: 07/07/2012] [Indexed: 11/29/2022]
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27
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Ingólfsson HI, Andersen OS. Alcohol's effects on lipid bilayer properties. Biophys J 2011; 101:847-55. [PMID: 21843475 DOI: 10.1016/j.bpj.2011.07.013] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 07/13/2011] [Accepted: 07/15/2011] [Indexed: 11/26/2022] Open
Abstract
Alcohols are known modulators of lipid bilayer properties. Their biological effects have long been attributed to their bilayer-modifying effects, but alcohols can also alter protein function through direct protein interactions. This raises the question: Do alcohol's biological actions result predominantly from direct protein-alcohol interactions or from general changes in the membrane properties? The efficacy of alcohols of various chain lengths tends to exhibit a so-called cutoff effect (i.e., increasing potency with increased chain length, which that eventually levels off). The cutoff varies depending on the assay, and numerous mechanisms have been proposed such as: limited size of the alcohol-protein interaction site, limited alcohol solubility, and a chain-length-dependent lipid bilayer-alcohol interaction. To address these issues, we determined the bilayer-modifying potency of 27 aliphatic alcohols using a gramicidin-based fluorescence assay. All of the alcohols tested (with chain lengths of 1-16 carbons) alter the bilayer properties, as sensed by a bilayer-spanning channel. The bilayer-modifying potency of the short-chain alcohols scales linearly with their bilayer partitioning; the potency tapers off at higher chain lengths, and eventually changes sign for the longest-chain alcohols, demonstrating an alcohol cutoff effect in a system that has no alcohol-binding pocket.
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Affiliation(s)
- Helgi I Ingólfsson
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, USA.
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28
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Klacsová M, Bulacu M, Kučerka N, Uhríková D, Teixeira J, Marrink S, Balgavý P. The effect of aliphatic alcohols on fluid bilayers in unilamellar DOPC vesicles — A small-angle neutron scattering and molecular dynamics study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2136-46. [DOI: 10.1016/j.bbamem.2011.04.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/30/2011] [Accepted: 04/21/2011] [Indexed: 10/18/2022]
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29
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Wang C, Ge Y, Mortensen J, Westh P. Interaction Free Energies of Eight Sodium Salts and a Phosphatidylcholine Membrane. J Phys Chem B 2011; 115:9955-61. [DOI: 10.1021/jp112203p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chunhua Wang
- Research Unit for Functional Biomaterials, Roskilde University NSM, 1 Universitetsvej DK-4000 Roskilde, Denmark
- MEMPHYS — Center for Biomembrane Physics, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Ying Ge
- Research Unit for Functional Biomaterials, Roskilde University NSM, 1 Universitetsvej DK-4000 Roskilde, Denmark
| | - John Mortensen
- Research Unit for Functional Biomaterials, Roskilde University NSM, 1 Universitetsvej DK-4000 Roskilde, Denmark
| | - Peter Westh
- Research Unit for Functional Biomaterials, Roskilde University NSM, 1 Universitetsvej DK-4000 Roskilde, Denmark
- MEMPHYS — Center for Biomembrane Physics, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
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30
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Rasch MR, Rossinyol E, Hueso JL, Goodfellow BW, Arbiol J, Korgel BA. Hydrophobic gold nanoparticle self-assembly with phosphatidylcholine lipid: membrane-loaded and janus vesicles. NANO LETTERS 2010; 10:3733-9. [PMID: 20731366 DOI: 10.1021/nl102387n] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hybrids of hydrophobic sub-2-nm-diameter dodecanethiol-coated Au nanoparticles and phosphatidylcholine (PC) lipid vesicles made by extrusion were examined by cryogenic transmission electron microscopy (cryoTEM). The nanoparticles loaded the vesicles as a dense monolayer in the hydrophobic core of the lipid bilayer, without disrupting their structure. Nanoparticle-vesicle hybrids could also be made by a dialysis process, mixing preformed vesicles with detergent-stabilized nanoparticles, but this approach led to vesicles only partially loaded with nanoparticles that segregated into hemispherical domains, forming a Janus vesicle-nanoparticle hybrid structure.
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Affiliation(s)
- Michael R Rasch
- Department of Chemical Engineering, Texas Materials Institute, and Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712-1062, USA
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31
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Meier M, Seelig J. Lipid and peptide dynamics in membranes upon insertion of n-alkyl-beta-D-glucopyranosides. Biophys J 2010; 98:1529-38. [PMID: 20409472 DOI: 10.1016/j.bpj.2009.12.4286] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 11/23/2009] [Accepted: 12/08/2009] [Indexed: 11/16/2022] Open
Abstract
The effect of nonionic detergents of the n-alkyl-beta-D-glucopyranoside class on the ordering of lipid bilayers and the dynamics of membrane-embedded peptides were investigated with 2H- and 31P-NMR. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was selectively deuterated at methylene segments C-2, C-7, and C-16 of the two fatty acyl chains. Two trans-membrane helices, WALP-19 and glycophorin A(71-98), were synthesized with Ala-d3 in the central region of the alpha-helix. n-Alkyl-beta-D-glucopyranosides with alkyl chains with 6, 7, 8, and 10 carbon atoms were added at increasing concentrations to the lipid membrane. The bilayer structure is retained up to a detergent/lipid molar ratio of 1:1. The insertion of the detergents leads to a selective disordering of the lipids. The headgroup region remains largely unaffected; the fatty acyl chain segments parallel to the detergent alkyl chain are only modestly disordered (10-20%), whereas lipid segments beyond the methyl terminus of the detergent show a decrease of up to 50%. The change in the bilayer order profile corresponds to an increase in bilayer entropy. Insertion of detergents into the lipid bilayers is completely entropy-driven. The entropy change accompanying lipid disorder is equivalent in magnitude to the hydrophobic effect. Ala-d3 deuterated WALP-19 and GlycA(71-97) were incorporated into bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine at a peptide/lipid molar ratio of 1:100 and measured above the 1,2-dimyristoyl-sn-glycero-3-phosphocholine gel/liquid-crystal phase transition. Well-resolved 2H-NMR quadrupole splittings were observed for the two trans-membrane helices, revealing a rapid rotation of the CD3 methyl rotor superimposed on an additional rotation of the whole peptide around the bilayer normal. The presence of detergent fluidizes the membrane and produces magnetic alignment of bilayer domains but does not produce essential changes in the peptide conformation or dynamics.
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Affiliation(s)
- Matthias Meier
- Department of Bioengineering, Stanford University, Stanford, California, USA
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32
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Niikura K, Nambara K, Okajima T, Matsuo Y, Ijiro K. Influence of hydrophobic structures on the plasma membrane permeability of lipidlike molecules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:9170-9175. [PMID: 20465219 DOI: 10.1021/la101039w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A series of FITC-labeled hydrophobic molecules (1-8) were prepared, and their cellular uptakes have been investigated using cell-cycle-synchronized HeLa cells. The cellular membrane permeability of compounds strongly depended on both the chemical structure and the cell-cycle phase. In the G1/S phase, branched hydrocarbon-containing 3 and cis-olefin-containing 2 and 8 were efficiently internalized into cells by passive diffusion. In contrast, linear alkyl chain-containing 1 and 7 were retained on the membrane without rapid internalization. In the M phase, rapid permeation was suppressed for all molecules.
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Affiliation(s)
- Kenichi Niikura
- Research Institute for Electronic Science, Hokkaido University, Kita21, Nishi10, Kita-Ku, Sapporo 001-0021, Japan.
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Klacsová M, Westh P, Balgavý P. Molecular and component volumes of saturated n-alkanols in DOPC+DOPS bilayers. Chem Phys Lipids 2010; 163:498-505. [DOI: 10.1016/j.chemphyslip.2010.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 04/07/2010] [Accepted: 04/08/2010] [Indexed: 10/19/2022]
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34
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Finol-Urdaneta RK, McArthur JR, Juranka PF, French RJ, Morris CE. Modulation of KvAP unitary conductance and gating by 1-alkanols and other surface active agents. Biophys J 2010; 98:762-72. [PMID: 20197029 DOI: 10.1016/j.bpj.2009.10.053] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 11/18/2022] Open
Abstract
The actions of alcohols and anesthetics on ion channels are poorly understood. Controversy continues about whether bilayer restructuring is relevant to the modulatory effects of these surface active agents (SAAs). Some voltage-gated K channels (Kv), but not KvAP, have putative low affinity alcohol-binding sites, and because KvAP structures have been determined in bilayers, KvAP could offer insights into the contribution of bilayer mechanics to SAA actions. We monitored KvAP unitary conductance and macroscopic activation and inactivation kinetics in PE:PG/decane bilayers with and without exposure to classic SAAs (short-chain 1-alkanols, cholesterol, and selected anesthetics: halothane, isoflurane, chloroform). At levels that did not measurably alter membrane specific capacitance, alkanols caused functional changes in KvAP behavior including lowered unitary conductance, modified kinetics, and shifted voltage dependence for activation. A simple explanation is that the site of SAA action on KvAP is its entire lateral interface with the PE:PG/decane bilayer, with SAA-induced changes in surface tension and bilayer packing order combining to modulate the shape and stability of various conformations. The KvAP structural adjustment to diverse bilayer pressure profiles has implications for understanding desirable and undesirable actions of SAA-like drugs and, broadly, predicts that channel gating, conductance and pharmacology may differ when membrane packing order differs, as in raft versus nonraft domains.
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Affiliation(s)
- Rocio K Finol-Urdaneta
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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35
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Martín-Rapún R, Byelov D, Palmans ARA, de Jeu WH, Meijer EW. Lyomesophases of C3-symmetrical bipyridine-based discs in alkanes: an X-ray diffraction study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:8794-8801. [PMID: 20050050 DOI: 10.1021/la9003017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The importance of the role of alkane solvents in the self-assembly process of pi-conjugated molecules is well recognized but hardly understood. Here we present our results on the X-ray diffraction studies that we conducted to gain insight into the supramolecular structure of mixtures of a bipyridine-based molecule (1) with alkanes. Independent of the alkane used (linear or branched), above x(w) > 0.06 (with x(w) being the weight fraction of 1) the mixtures show lyotropic liquid-crystalline behavior. The nature of the lyomesophase depends only on x(w) and not on the nature of the alkane (linear or branched). A columnar rectangular phase is present when x(w) > 0.66. Upon dilution of 1, a columnar hexagonal phase is assigned first (0.50 < x(w) < 0.65), and finally a columnar nematic phase is observed when x(w) < 0.50. Concentration-dependent SAXD measurements revealed that the dilution of 1 can be viewed as a swelling process. First, solvent molecules occupy space between the columns formed by 1, which are not disrupted. This process can quantitatively be described by a 2D swelling model. Only at lower concentrations does 3D swelling start as the columns start breaking into shorter fragments.
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Affiliation(s)
- Rafael Martín-Rapún
- Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Peters GH, Hansen FY, Møller MS, Westh P. Effects of Fatty Acid Inclusion in a DMPC Bilayer Membrane. J Phys Chem B 2008; 113:92-102. [DOI: 10.1021/jp806205m] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Günther H. Peters
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Flemming Y. Hansen
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Martin S. Møller
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Peter Westh
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
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37
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Terama E, Ollila OHS, Salonen E, Rowat AC, Trandum C, Westh P, Patra M, Karttunen M, Vattulainen I. Influence of ethanol on lipid membranes: from lateral pressure profiles to dynamics and partitioning. J Phys Chem B 2008; 112:4131-9. [PMID: 18341314 DOI: 10.1021/jp0750811] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have combined experiments with atomic-scale molecular dynamics simulations to consider the influence of ethanol on a variety of lipid membrane properties. We first employed isothermal titration calorimetry together with the solvent-null method to study the partitioning of ethanol molecules into saturated and unsaturated membrane systems. The results show that ethanol partitioning is considerably more favorable in unsaturated bilayers, which are characterized by their more disordered nature compared to their saturated counterparts. Simulation studies at varying ethanol concentrations propose that the partitioning of ethanol depends on its concentration, implying that the partitioning is a nonideal process. To gain further insight into the permeation of alcohols and their influence on lipid dynamics, we also employed molecular dynamics simulations to quantify kinetic events associated with the permeation of alcohols across a membrane, and to characterize the rotational and lateral diffusion of lipids and alcohols in these systems. The simulation results are in agreement with available experimental data and further show that alcohols have a small but non-vanishing effect on the dynamics of lipids in a membrane. The influence of ethanol on the lateral pressure profile of a lipid bilayer is found to be prominent: ethanol reduces the tension at the membrane-water interface and reduces the peaks in the lateral pressure profile close to the membrane-water interface. The changes in the lateral pressure profile are several hundred atmospheres. This supports the hypothesis that anesthetics may act by changing the lateral pressure profile exerted on proteins embedded in membranes.
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Affiliation(s)
- Emma Terama
- International Institute for Applied Systems Analysis, Schlossplatz 1, A-2361 Laxenburg, Austria
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38
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Takajo Y, Matsuki H, Kaneshina S, Aratono M, Yamanaka M. Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles. Colloids Surf B Biointerfaces 2007; 59:52-8. [PMID: 17560093 DOI: 10.1016/j.colsurfb.2007.04.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2007] [Revised: 04/09/2007] [Accepted: 04/12/2007] [Indexed: 10/23/2022]
Abstract
The miscibility and interaction of 1-hexanol (C6OH) and 1-heptanol (C7OH) with 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in the adsorbed films and micelles were investigated by measuring the surface tension of aqueous C6OH-DHPC and aqueous C7OH-DHPC solutions. The surface density, the mean molecular area, the composition of the adsorbed film, and the excess Gibbs energy of adsorption g(H,E), were estimated. Further, the critical micelle concentration of the mixtures was determined from the surface tension versus molality curves; the micellar composition was calculated. The miscibility of the 1-alkanols and DHPC molecules in the adsorbed film and micelles was examined using the phase diagram of adsorption (PDA) and that of micellization (PDM). The PDA and the composition dependence of g(H,E) indicated the non-ideal mixing of the 1-alkanols and DHPC molecules due to the attractive interaction between the molecules in the adsorbed film, while the PDM indicated that the 1-alkanol molecules were not incorporated in the micelles within DHPC rich region. The dependence of the mean molecular area of the mixtures on the surface composition suggested that the packing property of the adsorbed film depends on the chain length of 1-alkanol: C6OH expands the DHPC adsorbed film more than C7OH.
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Affiliation(s)
- Yuichi Takajo
- Department of Chemistry, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-Ku, 810-8560 Fukuoka, Japan
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Griepernau B, Leis S, Schneider MF, Sikor M, Steppich D, Böckmann RA. 1-Alkanols and membranes: a story of attraction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2899-913. [PMID: 17916322 DOI: 10.1016/j.bbamem.2007.08.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 06/22/2007] [Accepted: 08/03/2007] [Indexed: 10/22/2022]
Abstract
Although 1-alkanols have long been known to act as penetration enhancers and anesthetics, the mode of operation is not yet understood. In this study, long-time molecular dynamics simulations have been performed to investigate the effect of 1-alkanols of various carbon chain lengths onto the structure and dynamics of dimyristoylphosphatidylcholine bilayers. The simulations were complemented by microcalorimetry, continuous bleaching and film balance experiments. In the simulations, all investigated 1-alkanols assembled inside the lipid bilayer within tens of nanoseconds. Their hydroxyl groups bound preferentially to the lipid carbonyl group and the hydrocarbon chains stretched into the hydrophobic core of the bilayer. Both molecular dynamics simulations and experiments showed that all 1-alkanols drastically affected the bilayer properties. Insertion of long-chain 1-alkanols decreased the area per lipid while increasing the thickness of the bilayer and the order of the lipids. The bilayer elasticity was reduced and the diffusive motion of the lipids within the bilayer plane was suppressed. On the other hand, integration of ethanol into the bilayer enlarged the area per lipid. The bilayer became softer and lipid diffusion was enhanced.
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Affiliation(s)
- Beate Griepernau
- Theoretical and Computational Membrane Biology, Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
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Uhríková D, Rybár P, Hianik T, Balgavý P. Component volumes of unsaturated phosphatidylcholines in fluid bilayers: a densitometric study. Chem Phys Lipids 2007; 145:97-105. [PMID: 17196953 DOI: 10.1016/j.chemphyslip.2006.11.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 10/26/2006] [Accepted: 11/13/2006] [Indexed: 10/23/2022]
Abstract
The specific volumes of six 1,2-diacylphosphatidylcholines with monounsaturated acyl chains (diCn:1PC, n=14-24 is the even number of acyl chain carbons) in fluid bilayers in multilamellar vesicles dispersed in H(2)O were determined by the vibrating tube densitometry as a function of temperature. From the data obtained with diCn:1PC (n=14-22) vesicles in combination with the densitometric data from Tristram-Nagle et al. [Tristram-Nagle, S., Petrache, H.I., Nagle, J.F., 1998. Structure and interactions of fully hydrated dioleoylphosphatidylcholine bilayers. Biophys. J. 75, 917-925.] and Koenig and Gawrisch [Koenig, B.W., Gawrisch, K., 2005. Specific volumes of unsaturated phosphatidylcholines in the liquid crystalline lamellar phase. Biochim. Biophys. Acta 1715, 65-70.], the component volumes of phosphatidylcholines in fully hydrated fluid bilayers at 30 degrees C were obtained. The volume of the acyl chain CH and CH(2) group is V(CH)=22.30 A(3) and V(CH2) =A(3), respectively. The volume of the headgroup including the glyceryl and acyl carbonyls, V(H), and the ratio of acyl chain methyl and methylene group volumes, r=V(CH3):V(CH2) are linearly interdependent: V(H)=a-br, where a=434.41 A(3) and b=-55.36 A(3) at 30 degrees C. From the temperature dependencies of component volumes, their isobaric thermal expansivities (alpha(X)=V(X)(-1)(partial differential V(X)/ partial differential T) where X=CH(2), CH, or H were calculated: alpha(CH2)=118.4x10(-5)K(-1), alpha(CH)=71.0x10(-5)K(-1), alpha(H)=7.9x10(-5)K(-1) (for r=2) and alpha(H)=9.6x10(-5)K(-1) (for r=1.9). The specific volume of diC24:1PC changes at the main gel-fluid phase transition temperature, t(m)=26.7 degrees C, by 0.0621 ml/g, its specific volume is 0.9561 and 1.02634 ml/g at 20 and 30 degrees C, respectively, and its isobaric thermal expansivity alpha=68.7x10(-5) and 109.2x10(-5)K(-1) below and above t(m), respectively. The component volumes and thermal expansivities obtained can be used for the interpretation of X-ray and neutron scattering and diffraction experiments and for the guiding and testing molecular dynamics simulations of phosphatidylcholine bilayers in the fluid state.
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Affiliation(s)
- Daniela Uhríková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia
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Pedersen UR, Peters GH, Westh P. Molecular packing in 1-hexanol–DMPC bilayers studied by molecular dynamics simulation. Biophys Chem 2007; 125:104-11. [PMID: 16887254 DOI: 10.1016/j.bpc.2006.07.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Accepted: 07/12/2006] [Indexed: 12/20/2022]
Abstract
The structure and molecular packing density of a "mismatched" solute, 1-hexanol, in lipid membranes of dimyristoyl phosphatidylcholine (DMPC) was studied by molecular dynamics simulations. We found that the average location and orientation of the hexanol molecules matched earlier experimental data on comparable systems. The local density or molecular packing in DMPC-hexanol was elucidated through the average Voronoi volumes of all heavy (non-hydrogen) atoms. Analogous analysis was conducted on trajectories from simulations of pure 1-hexanol and pure (hydrated) DMPC bilayers. The results suggested a positive volume change, DeltaV(m), of 4 cm(3) mol(-1) hexanol partitioned at 310 K in good accordance with experimental values. Analysis of the apparent volumes of each component in the pure and mixed states further showed that DeltaV(m) reflects a balance between a substantial increase in the packing density of the alcohol upon partitioning and an even stronger loosening in the packing of the lipid. Furthermore, analysis of Voronoi volumes along the membrane normal identifies a distinctive depth dependence of the changes in molecular packing. The outer (interfacial) part of the lipid acyl chains (up to C8) is stretched by about 4%. Concomitantly, the average lateral area per chain decreases and these two effects compensate so that the overall packing density in the outer region, where the hexanol molecules are located, remains practically constant. The core of the bilayer (C9-C13) is slightly thinned. The average lateral area per chain in this region expands, resulting in a looser packing density. The net effect in the core is a 2-3% decrease in density corresponding to a total volume increase of approximately 14 cm(3) mol(-1) hexanol partitioned.
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Affiliation(s)
- Ulf R Pedersen
- Department of Life Sciences and Chemistry and MEMPHYS, Center for Biomembrane Physics, Roskilde University, 1 Universitetsvej, PO Box 260, DK-4000 Roskilde, Denmark
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