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Obiol DJ, Amundarain MJ, Zamarreño F, Vietri A, Antollini SS, Costabel MD. Oleic Acid Could Act as a Channel Blocker in the Inhibition of nAChR: Insights from Molecular Dynamics Simulations. J Phys Chem B 2024; 128:2398-2411. [PMID: 38445598 DOI: 10.1021/acs.jpcb.3c07067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
The activation of the muscular nicotinic acetylcholine receptor (nAChR) produces the opening of the channel, with the consequent increase in the permeability of cations, triggering an excitatory signal. Free fatty acids (FFA) are known to modulate the activity of the receptor as noncompetitive antagonists, acting at the membrane-AChR interface. We present molecular dynamics simulations of a model of nAChR in a desensitized closed state embedded in a lipid bilayer in which distinct membrane phospholipids were replaced by two different monounsaturated FFA that differ in the position of a double bond. This allowed us to detect and describe that the cis-18:1ω-9 FFA were located at the interface between the transmembrane segments of α2 and γ subunits diffused into the channel lumen with the consequent potential ability to block the channel to the passage of ions.
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Affiliation(s)
- Diego J Obiol
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Avenida Leandro N. Alem 1253, B8000CPB Bahía Blanca, Argentina
| | - María J Amundarain
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Avenida Leandro N. Alem 1253, B8000CPB Bahía Blanca, Argentina
- Department of Chemistry, Organic Chemistry III, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Fernando Zamarreño
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Avenida Leandro N. Alem 1253, B8000CPB Bahía Blanca, Argentina
| | - Agustín Vietri
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Avenida Leandro N. Alem 1253, B8000CPB Bahía Blanca, Argentina
| | - Silvia S Antollini
- Instituto de Investigaciones Bioquímicas de Bahía Blanca CONICET-UNS, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, B8000FWB Bahía Blanca, Argentina
| | - Marcelo D Costabel
- Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Avenida Leandro N. Alem 1253, B8000CPB Bahía Blanca, Argentina
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2
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Sakuma Y, Kayamori N, Tanaka J, Haga K, Imai M, Kawakatsu T. Effects of grafted polymers on the lipid membrane fluidity. Biophys J 2024; 123:489-501. [PMID: 38243595 PMCID: PMC10912922 DOI: 10.1016/j.bpj.2024.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 07/27/2023] [Accepted: 01/12/2024] [Indexed: 01/21/2024] Open
Abstract
Since the membrane fluidity controls the cellular functions, it is important to identify the factors that determine the cell membrane viscosity. Cell membranes are composed of not only lipids and proteins but also polysaccharide chain-anchored molecules, such as glycolipids. To reveal the effects of grafted polymers on the membrane fluidity, in this study, we measured the membrane viscosity of polymer-grafted giant unilamellar vesicles (GUVs), which were prepared by introducing the poly (ethylene glycol) (PEG)-anchored lipids to the ternary GUVs composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol. The membrane viscosity was obtained from the velocity field on the GUV generated by applying a point force, based on the hydrodynamic model proposed by Henle and Levine. The velocity field was visualized by a motion of the circular liquid ordered (Lo) domains formed by a phase separation. With increasing PEG density, the membrane viscosity of PEG-grafted GUVs increased gradually in the mushroom region and significantly in the brush region. We propose a hydrodynamic model that includes the excluded volume effect of PEG chains to explain the increase in membrane viscosity in the mushroom region. This work provides a basic understanding of how grafted polymers affect the membrane fluidity.
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Affiliation(s)
- Yuka Sakuma
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan.
| | - Nana Kayamori
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Julia Tanaka
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Kenya Haga
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Masayuki Imai
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Toshihiro Kawakatsu
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
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3
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Jain H, Karathanou K, Bondar AN. Graph-Based Analyses of Dynamic Water-Mediated Hydrogen-Bond Networks in Phosphatidylserine: Cholesterol Membranes. Biomolecules 2023; 13:1238. [PMID: 37627303 PMCID: PMC10452392 DOI: 10.3390/biom13081238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/03/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023] Open
Abstract
Phosphatidylserine lipids are anionic molecules present in eukaryotic plasma membranes, where they have essential physiological roles. The altered distribution of phosphatidylserine in cells such as apoptotic cancer cells, which, unlike healthy cells, expose phosphatidylserine, is of direct interest for the development of biomarkers. We present here applications of a recently implemented Depth-First-Search graph algorithm to dissect the dynamics of transient water-mediated lipid clusters at the interface of a model bilayer composed of 1-palmytoyl-2-oleoyl-sn-glycero-2-phosphatidylserine (POPS) and cholesterol. Relative to a reference POPS bilayer without cholesterol, in the POPS:cholesterol bilayer there is a somewhat less frequent sampling of relatively complex and extended water-mediated hydrogen-bond networks of POPS headgroups. The analysis protocol used here is more generally applicable to other lipid:cholesterol bilayers.
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Affiliation(s)
- Honey Jain
- Faculty of Physics, University of Bucharest, Atomiștilor 405, 077125 Măgurele, Romania
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | | | - Ana-Nicoleta Bondar
- Faculty of Physics, University of Bucharest, Atomiștilor 405, 077125 Măgurele, Romania
- IAS-5/INM-9, Forschungszentrum Jülich, Institute of Computational Biomedicine, Wilhelm-Johnen Straße, 52428 Jülich, Germany
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4
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Jabbari V, Sawczyk M, Amiri A, Král P, Shahbazian-Yassar R. Unveiling growth and dynamics of liposomes by graphene liquid cell-transmission electron microscopy. NANOSCALE 2023; 15:5011-5022. [PMID: 36790028 DOI: 10.1039/d2nr06147c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Liposome is a model system for biotechnological and biomedical purposes spanning from targeted drug delivery to modern vaccine research. Yet, the growth mechanism of liposomes is largely unknown. In this work, the formation and evolution of phosphatidylcholine-based liposomes are studied in real-time by graphene liquid cell-transmission electron microscopy (GLC-TEM). We reveal important steps in the growth, fusion and denaturation of phosphatidylcholine (PC) liposomes. We show that initially complex lipid aggregates resembling micelles start to form. These aggregates randomly merge while capturing water and forming small proto-liposomes. The nanoscopic containers continue sucking water until their membrane becomes convex and free of redundant phospholipids, giving stabilized PC liposomes of different sizes. In the initial stage, proto-liposomes grow at a rate of 10-15 nm s-1, which is followed by their growth rate of 2-5 nm s-1, limited by the lipid availability in the solution. Molecular dynamics (MD) simulations are used to understand the structure of micellar clusters, their evolution, and merging. The liposomes are also found to fuse through lipid bilayers docking followed by the formation of a hemifusion diaphragm and fusion pore opening. The liposomes denaturation can be described by initial structural destabilization and deformation of the membrane followed by the leakage of the encapsulated liquid. This study offers new insights on the formation and growth of lipid-based molecular assemblies which is applicable to a wide range of amphiphilic molecules.
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Affiliation(s)
- Vahid Jabbari
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL 60607, USA. rsyassar@uic
| | - Michal Sawczyk
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Azadeh Amiri
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL 60607, USA. rsyassar@uic
| | - Petr Král
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Physics, Pharmaceutical Sciences, and Chemical Engineering, University of Illinois at Chicago, Chicago, USA
| | - Reza Shahbazian-Yassar
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL 60607, USA. rsyassar@uic
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5
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Marcos X, Sixto-López Y, Pérez-Casas S, Correa-Basurto J. Computational study of DMPC liposomes loaded with the N-(2-Hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) and determination of its antiproliferative activity in vitro in NIH-3T3 cells. J Biomol Struct Dyn 2022; 40:11448-11459. [PMID: 34315332 DOI: 10.1080/07391102.2021.1955744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
N-(2-Hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) is a valproic acid (VPA) derivative that has shown promising antiproliferative effects in different cancer cell lines, such as A204, HeLa, and MDA-MB-231. However, its low water solubility could reduce its therapeutic effectiveness. To solve this problem, in this work, we incorporated HO-AAVPA into dimyristoyl-phosphatidylcholine (DMPC) liposomes in the presence or absence of cholesterol (CHOL). Using differential scanning calorimetry (DSC), we found that the transition enthalpy (ΔHtr) of DMPC liposomes is reduced in the presence of CHOL and/or HO-AAVPA, indicating the favorable interactions between CHOL and/or HO-AAVPA and DMPC. Further, by molecular dynamics simulations it was possible to observed that HO-AAVPA migrates from the center of the bilayer toward the water and lipid interface of the DPMC bilayer systems exposing the amine group to water and the aliphatic chain toward the interior of the bilayer. As a consequence, we observed an ordering of the lipid bilayer. Moreover, CHOL harbors into the inner bilayer membrane, increasing the order parameter of the system. The liposomal solutions loaded with HO-AAVPA were tested in the NIH3T3 cell line, showing a reduction in cell proliferation compared to those cells presented without liposomes.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Xelhua Marcos
- Laboratorio de Biofísica y Biocatálisis, Escuela Superior de Medicina, Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Yudibeth Sixto-López
- Laboratorio de Diseño y Desarrollo de Nuevos Fármacos e Innovación Biotecnológica (Laboratory for the Design and Development of New Drugs and Biotechnological Innovation) SEPI-ESM Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Silvia Pérez-Casas
- Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - José Correa-Basurto
- Laboratorio de Diseño y Desarrollo de Nuevos Fármacos e Innovación Biotecnológica (Laboratory for the Design and Development of New Drugs and Biotechnological Innovation) SEPI-ESM Instituto Politécnico Nacional, Ciudad de México, Mexico
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6
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Somjid S, Shinsuphan N, Temprom L, Krongsuk S. Effects of cholesterol and temperature on structural properties and dynamic behavior of niosome bilayers with melatonin Inclusion: A Coarse-Grained simulation study. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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7
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Min T, Xie X, Ren K, Sun T, Wang H, Dang C, Zhang H. Therapeutic Effects of Cold Atmospheric Plasma on Solid Tumor. Front Med (Lausanne) 2022; 9:884887. [PMID: 35646968 PMCID: PMC9139675 DOI: 10.3389/fmed.2022.884887] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 04/13/2022] [Indexed: 12/14/2022] Open
Abstract
Cancer is a devastating disease, and there is no particularly effective treatment at present. Recently, a new treatment, cold atmospheric plasma (CAP), has been proposed. At present, CAP is confirmed to have selective killing effect on tumor by many studies in vitro and in vivo. A targeted literature search was carried out on the study of cold atmospheric plasma. Through analysis and screening, a narrative review approach was selected to describe therapeutic effects of cold atmospheric plasma on solid tumor. According to the recent studies on plasma, some hypothetical therapeutic schemes of CAP are proposed in this paper. The killing mechanism of CAP on solid tumor is expounded in terms of the selectivity of CAP to tumor, the effects of CAP on cells, tumor microenvironment (TME) and immune system. CAP has many effects on solid tumors, and these effects are dose-dependent. The effects of optimal doses of CAP on solid tumors include killing tumor cells, inhibiting non-malignant cells and ECM in TME, affecting the communication between tumor cells, and inducing immunogenic death of tumor cells. In addition, several promising research directions of CAP are proposed in this review, which provide guidance for future research.
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Affiliation(s)
- Tianhao Min
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Xie
- Department of Nuclear Medicine, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Kaijie Ren
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Tuanhe Sun
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Haonan Wang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Chengxue Dang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
- *Correspondence: Chengxue Dang
| | - Hao Zhang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
- Hao Zhang
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8
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Surovtsev NV, Adichtchev SV. Dynamic response on a nanometer scale of binary phospholipid-cholesterol vesicles: Low-frequency Raman scattering insight. Phys Rev E 2021; 104:054406. [PMID: 34942765 DOI: 10.1103/physreve.104.054406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 10/18/2021] [Indexed: 11/07/2022]
Abstract
Low-frequency Raman spectroscopy was used to study the dynamic response on a nanometer scale of aqueous suspensions of two-component lipid vesicles. Binary mixtures of saturated phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC) and cholesterol are interesting for possible coexistence of solidlike and liquid-ordered phases, while the phase coexistence was not reported for unsaturated phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC) and cholesterol mixtures. The DOPC-DPPC mixtures represent the well-documented case of coexisting domains of solidlike and liquid-disordered phases. These three series of lipid mixtures are studied here. A broad peak with the maximum in the range of 30-50cm^{-1} and a narrow peak near 10cm^{-1} are observed in the Raman susceptibility of the binary mixtures and attributed to the acousticlike vibrational density of states and layer modes, respectively. Parameters of the broad and narrow peaks are sensitive to lateral and conformational hydrocarbon chain ordering. It was also demonstrated that the low-frequency Raman susceptibility of multicomponent lipid bilayers allows one to determine the phase state of lipid bilayers and distinguish the homogeneous distribution of molecular complexes from coexisting domains with sizes above several nanometers. Thus, the low-frequency Raman spectroscopy provides unique information in studying phase coexistence in lipid bilayers.
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Affiliation(s)
- N V Surovtsev
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - S V Adichtchev
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
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9
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Caparotta M, Puiatti M, Masone D. Artificial stabilization of the fusion pore by intra-organelle styrene-maleic acid copolymers. SOFT MATTER 2021; 17:8314-8321. [PMID: 34550159 DOI: 10.1039/d1sm00978h] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Styrene-maleic acid copolymers have become an advantageous detergent-free alternative for membrane protein isolation. Since their discovery, experimental membrane protein extraction and purification by keeping intact their lipid environment has become significantly easier. With the aim of identifying new applications of these interesting copolymers, their molecular binding and functioning mechanisms have recently become intense objects of study. In this work, we describe the use of styrene-maleic acid copolymers as an artificial tool to stabilize the fusion pore. We show that when these copolymers circumscribe the water channel that defines the fusion pore, they keep it from shrinking and closing. We describe how only intra-organelle copolymers have stabilizing capabilities while extra-organelle ones have negligible or even contrary effects on the fusion pore life-time.
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Affiliation(s)
- Marcelo Caparotta
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500, Mendoza, Argentina
| | - Marcelo Puiatti
- Instituto de Investigaciones en Físico-Química de Córdoba (INFIQC) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba (UNC), 5016, Córdoba, Argentina
| | - Diego Masone
- Facultad de Ingeniería, Universidad Nacional de Cuyo (UNCuyo), 5500, Mendoza, Argentina
- Instituto de Histología y Embriología de Mendoza (IHEM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500, Mendoza, Argentina.
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10
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Bouquiaux C, Castet F, Champagne B. Unravelling the Effects of Cholesterol on the Second-Order Nonlinear Optical Responses of Di-8-ANEPPS Dye Embedded in Phosphatidylcholine Lipid Bilayers. J Phys Chem B 2021; 125:10195-10212. [PMID: 34491062 DOI: 10.1021/acs.jpcb.1c05630] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cholesterol is known for its role in maintaining the correct fluidity and rigidity of the animals cell membranes and thus their functions. Assessing the content and the role of cholesterol in lipid bilayers is therefore of crucial importance for a deeper understanding and control of membrane functioning. In this computational work, we investigate bilayers built from three types of glycerophospholipid phosphatidylcholine (PC) lipids, namely dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and dioleoylphosphatidylcholine (DOPC), and containing different amounts of cholesterol by analyzing the second-harmonic generation (SHG) nonlinear optical (NLO) response of a probe molecule, di-8-ANEPPS, inserted into the membranes. This molecular property presents the advantage to be specific to interfacial regions such as lipid bilayers. To unravel these effects, Molecular Dynamics (MD) simulations have been performed on both DPPC and DOPC lipids by varying the cholesterol mole fraction (from 0 to 0.66), while POPC was only considered as a pure bilayer. In the case of the structural properties of the bilayers, all the analyses converge toward the same conclusion: as the mole fraction of cholesterol increases, the systems become more rigid, confirming the condensing effect of cholesterol. In addition, the chromophore is progressively more aligned with respect to the normal to the bilayer. On the contrary, addition of unsaturation disorders the lipid bilayers, with barely no impact on the alignment of the chromophore. Then, using the frames obtained from the MD simulations, the first hyperpolarizability β of the dye in its environment has been computed at the TDDFT level. On the one hand, the addition of cholesterol induces a progressive increase of the diagonal component the β tensor parallel to the bilayer normal. On the other hand, larger β values have been calculated for the unsaturated than for the saturated lipid systems. In summary, this study illustrates the relationship between the composition and structure of the bilayers and the NLO responses of the embedded dye.
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Affiliation(s)
- Charlotte Bouquiaux
- Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, rue de Bruxelles, 61, B-5000 Namur, Belgium
| | - Frédéric Castet
- , Institut des Sciences Moléculaires, UMR 5255 CNRS, University of Bordeaux, cours de la Libération 351, F-33405 Talence Cedex, France
| | - Benoît Champagne
- Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, rue de Bruxelles, 61, B-5000 Namur, Belgium
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11
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Wood MH, Milan DC, Nichols RJ, Casford MTL, Horswell SL. A quantitative determination of lipid bilayer deposition efficiency using AFM. RSC Adv 2021; 11:19768-19778. [PMID: 35479201 PMCID: PMC9033767 DOI: 10.1039/d1ra01920a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 05/26/2021] [Indexed: 12/14/2022] Open
Abstract
The efficacy of a number of different methods for depositing a dimyristoylphosphatidylcholine (DMPC) lipid bilayer or DMPC–cholesterol (3 : 1) mixed bilayer onto a silicon substrate has been investigated in a quantitative manner using atomic force microscopy (AFM) image analysis to extract surface coverage. Complementary AFM-IR measurements were used to confirm the presence of the lipids. For the Langmuir–Blodgett/Schaefer deposition method at temperatures below the chain-melting transition temperature (Tm), a large number of bilayer defects resulted when DMPC was deposited from a water subphase. Addition of calcium ions to the trough led to smaller, more frequent defects, whereas addition of cholesterol to the lipid mixture led to a vast improvement in bilayer coverage. Poor coverage was achieved for deposition at temperatures above Tm. Formation of the deposited bilayer from vesicle fusion proved a more reliable method for all systems, with formation of near-complete bilayers within 60 seconds at temperatures above Tm, although this method led to a higher probability of multilayer formation and rougher bilayer surfaces. The efficacy of different methods for depositing a DMPC or mixed DMPC–cholesterol (3 : 1) lipid bilayer onto a silicon substrate has been investigated in a quantitative manner using atomic force microscopy image analysis to extract surface coverage.![]()
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Affiliation(s)
- Mary H Wood
- School of Chemistry, University of Birmingham Birmingham B15 2TT UK
| | - David C Milan
- Department of Chemistry, University of Liverpool Liverpool L69 7ZD UK
| | - Richard J Nichols
- Department of Chemistry, University of Liverpool Liverpool L69 7ZD UK
| | - Michael T L Casford
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Sarah L Horswell
- School of Chemistry, University of Birmingham Birmingham B15 2TT UK
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12
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Martí J, Lu H. Microscopic Interactions of Melatonin, Serotonin and Tryptophan with Zwitterionic Phospholipid Membranes. Int J Mol Sci 2021; 22:2842. [PMID: 33799606 PMCID: PMC8001758 DOI: 10.3390/ijms22062842] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/05/2021] [Accepted: 03/08/2021] [Indexed: 12/15/2022] Open
Abstract
The interactions at the atomic level between small molecules and the main components of cellular plasma membranes are crucial for elucidating the mechanisms allowing for the entrance of such small species inside the cell. We have performed molecular dynamics and metadynamics simulations of tryptophan, serotonin, and melatonin at the interface of zwitterionic phospholipid bilayers. In this work, we will review recent computer simulation developments and report microscopic properties, such as the area per lipid and thickness of the membranes, atomic radial distribution functions, angular orientations, and free energy landscapes of small molecule binding to the membrane. Cholesterol affects the behaviour of the small molecules, which are mainly buried in the interfacial regions. We have observed a competition between the binding of small molecules to phospholipids and cholesterol through lipidic hydrogen-bonds. Free energy barriers that are associated to translational and orientational changes of melatonin have been found to be between 10-20 kJ/mol for distances of 1 nm between melatonin and the center of the membrane. Corresponding barriers for tryptophan and serotonin that are obtained from reversible work methods are of the order of 10 kJ/mol and reveal strong hydrogen bonding between such species and specific phospholipid sites. The diffusion of tryptophan and melatonin is of the order of 10-7 cm2/s for the cholesterol-free and cholesterol-rich setups.
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Affiliation(s)
- Jordi Martí
- Department of Physics, Technical University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain
| | - Huixia Lu
- School of Pharmacy, Shanghai Jiaotong University, Shanghai 200240, China;
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13
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Sanver D, Sadeghpour A, Rappolt M, Di Meo F, Trouillas P. Structure and Dynamics of Dioleoyl-Phosphatidylcholine Bilayers under the Influence of Quercetin and Rutin. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:11776-11786. [PMID: 32911935 DOI: 10.1021/acs.langmuir.0c01484] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Quercetin and rutin, two widely studied flavonoids with applications foreseen in the sectors of pharmaceutical and cosmetic industries, have been chosen as model compounds for a detailed structural and dynamical investigation onto their influence on fluid lipid bilayers. Combining global small angle X-ray scattering analysis with molecular dynamics, various changes in the properties of dioleoyl-phosphatidylcholine (DOPC) bilayers have been determined. The solubility of quercetin in DOPC membranes is assured up to 12 mol %, whereas rutin, with additional glucose and rhamnose groups, are fully soluble only up to 6 mol %. Both flavonoids induce an increase in membrane undulations and thin the bilayers slightly (<1 Å) in a concentration dependent manner, wherein quercetin shows a stronger effect. Concomitantly, in the order of 2-4%, the adjacent bilayer distance increases with the flavonoid's concentration. Partial molecular areas of quercetin and rutin are determined to be 26 and 51 Å2, respectively. Simulated averaged areas per molecule confirm these estimates. A 60° tilted orientation of quercetin is observed with respect to the bilayer normal, whereas the flavonoid moiety of rutin is oriented more perpendicular (α-angle 30°) to the membrane surface. Both flavonoid moieties are located at a depth of 12 and 16 Å for quercetin and rutin, respectively, while their anionic forms display a location closer to the polar interface. Finally, at both simulated concentrations (1.5 and 12 mol %), DOPC-rutin systems induce a stronger packing of the pure DOPC lipid bilayer, mainly due to stronger attractive electrostatic interactions in the polar lipid head region.
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Affiliation(s)
- Didem Sanver
- Faculty of Engineering and Architecture, Department of Food Engineering, Necmettin Erbakan University, Konya 42050, Turkey
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, U.K
| | - Amin Sadeghpour
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, U.K
- Biomaterials Science Center, Department of Biomedical Engineering, University of Basel, Allschwil 4123, Switzerland
| | - Michael Rappolt
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, U.K
| | - Florent Di Meo
- INSERM U1248 IPPRITT, University of Limoges, 2 rue du Prof. Descottes, Limoges 87000, France
| | - Patrick Trouillas
- INSERM U1248 IPPRITT, University of Limoges, 2 rue du Prof. Descottes, Limoges 87000, France
- RCPTM, Department of Physical Chemistry, Faculty of Sciences, Palacký University, Olomouc 771 47, Czech Republic
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14
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Shen Z, Ge J, Ye H, Tang S, Li Y. Cholesterol-like Condensing Effect of Perfluoroalkyl Substances on a Phospholipid Bilayer. J Phys Chem B 2020; 124:5415-5425. [PMID: 32515593 DOI: 10.1021/acs.jpcb.0c00980] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
To understand the potential cytotoxicity of perfluoroalkyl substances (PFAS), we study their interactions with a model phospholipid bilayer membrane using molecular dynamics (MD) simulations. Four typical PFAS molecules are investigated, including perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctanesulfonic acid (PFOS), and perfluorohexane sulfonate (PFHxS). All of these PFAS molecules are found to spontaneously penetrate the lipid bilayer within a short simulation time (a few nanoseconds). During the penetration process, further free-energy analysis reveals that a PFAS molecule encounters an energy barrier at the bilayer/water interface. To overcome this free-energy barrier, the PFAS molecule flips itself at the interface. We further investigate the influence of embedded PFAS molecules on the membrane properties. All of the embedded PFAS molecules are found to produce a cholesterol-like condensing effect on the lipid bilayer, which includes increases of the order parameters of lipid tails and the thickness of the lipid bilayer and a decrease of area per lipid. Moreover, the PFAS molecules are found to form hydrogen bonds with oxygen atoms at three different positions of a lipid molecule. Our work reveals the penetration pathway of PFAS molecules entering into a lipid bilayer. In addition, the cholesterol-like condensing effect induced by embedded PFAS molecules on model membranes is systematically investigated and discussed. Our simulations can help understand the physical mechanisms of PFAS cytotoxicity.
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Affiliation(s)
- Zhiqiang Shen
- Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Jeffrey Ge
- Department of Materials Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Huilin Ye
- Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Shan Tang
- State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, and International Research Center for Computational Mechanics, Dalian University of Technology, Dalian 116023, P. R. China
| | - Ying Li
- Department of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States
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15
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Cellular absorption of small molecules: free energy landscapes of melatonin binding at phospholipid membranes. Sci Rep 2020; 10:9235. [PMID: 32513935 PMCID: PMC7280225 DOI: 10.1038/s41598-020-65753-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 05/05/2020] [Indexed: 12/28/2022] Open
Abstract
Free energy calculations are essential to unveil mechanisms at the atomic scale such as binding of small solutes and their translocation across cell membranes, eventually producing cellular absorption. Melatonin regulates biological rhythms and is directly related to carcinogenesis and neurodegenerative disorders. Free energy landscapes obtained from well-tempered metadynamics simulations precisely describe the characteristics of melatonin binding to specific sites in the membrane and reveal the role of cholesterol in free energy barrier crossing. A specific molecular torsional angle and the distance between melatonin and the center of the membrane along the normal to the membrane Z-axis have been considered as suitable reaction coordinates. Free energy barriers between two particular orientations of the molecular structure (folded and extended) have been found to be of about 18 kJ/mol for z-distances of about 1–2 nm. The ability of cholesterol to expel melatonin out of the internal regions of the membrane towards the interface and the external solvent is explained from a free energy perspective. The calculations reported here offer detailed free energy landscapes of melatonin embedded in model cell membranes and reveal microscopic information on its transition between free energy minima, including the location of relevant transition states, and provide clues on the role of cholesterol in the cellular absorption of small molecules.
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16
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Ou L, Corradi V, Tieleman DP, Liang Q. Atomistic Simulations on Interactions between Amphiphilic Janus Nanoparticles and Lipid Bilayers: Effects of Lipid Ordering and Leaflet Asymmetry. J Phys Chem B 2020; 124:4466-4475. [DOI: 10.1021/acs.jpcb.9b11989] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Luping Ou
- Center for Statistical and Theoretical Condensed Matter Physics and Department of Physics, Zhejiang Normal University, Jinhua 321004, P. R. China
| | - Valentina Corradi
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - D. Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - Qing Liang
- Center for Statistical and Theoretical Condensed Matter Physics and Department of Physics, Zhejiang Normal University, Jinhua 321004, P. R. China
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17
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Liu Z, Cui J, Zhan W. Dipolar Janus liposomes: formation, electrokinetic motion and self-assembly. SOFT MATTER 2020; 16:2177-2184. [PMID: 31998919 DOI: 10.1039/c9sm02254f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Presented herein is the first report on dipolar Janus liposomes-liposomes that contain opposite surface charges decorating the two hemispheres of the same colloidal body. Such heterogeneous organization of surface charge is achieved through cholesterol-modulated lipid phase separation, which sorts anionic/cationic lipids into coexisting liquid-ordered/liquid-disordered domains. We present optimized experimental conditions to produce these liposomes in high yields, based on the gel-assisted hydration of ternary lipid systems consisting of cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, and 1,2-dioleoyl-sn-glycero-3-phosphocholine. The size/charge distribution and domain configuration of these liposomes are characterized in detail by confocal fluorescence microscopy, nanosphere binding and zeta potential measurements. Using confocal fluorescence microscopy, we also follow the electrokinetic motion as well as the electrostatic self-assembly of these new dipolar Janus particles.
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Affiliation(s)
- Zening Liu
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
| | - Jinyan Cui
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
| | - Wei Zhan
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
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18
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Kumar S, Rana R, Yadav DK. Atomic-scale modeling of the effect of lipid peroxidation on the permeability of reactive species. J Biomol Struct Dyn 2020; 39:1284-1294. [PMID: 32072880 DOI: 10.1080/07391102.2020.1730971] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Biomembranes and lipid systems are rich in unsaturated lipid components and are subject to photo-induced lipid peroxidation. The peroxidized lipid products in cellular systems are known to affect the structural organization and function of the biomembrane. We employed molecular dynamics simulations to study the effects of phospholipid peroxidation on membrane properties and the permeability of different reactive species. The results suggest that when the lipids are peroxidized, the peroxide group moves toward the membrane surface, which causes the membrane system to expand laterally and increase in area. The permeability profile revealed that nitrogen species can easily permeate through the native and peroxidized system in comparison to oxygen species, suggesting its importance in plasma-based treatment. Thus, by breaching the energy barrier with lower energy, they can traverse the cell membrane and induce oxidative stress, which leads to apoptosis.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Surendra Kumar
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, Incheon, South Korea
| | - Rashmi Rana
- Department of Research, Sir Ganga Ram Hospital, New Delhi, India
| | - Dharmendra K Yadav
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, Incheon, South Korea
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19
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Semmler ML, Bekeschus S, Schäfer M, Bernhardt T, Fischer T, Witzke K, Seebauer C, Rebl H, Grambow E, Vollmar B, Nebe JB, Metelmann HR, von Woedtke T, Emmert S, Boeckmann L. Molecular Mechanisms of the Efficacy of Cold Atmospheric Pressure Plasma (CAP) in Cancer Treatment. Cancers (Basel) 2020; 12:cancers12020269. [PMID: 31979114 PMCID: PMC7072164 DOI: 10.3390/cancers12020269] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 12/30/2022] Open
Abstract
Recently, the potential use of cold atmospheric pressure plasma (CAP) in cancer treatment has gained increasing interest. Especially the enhanced selective killing of tumor cells compared to normal cells has prompted researchers to elucidate the molecular mechanisms for the efficacy of CAP in cancer treatment. This review summarizes the current understanding of how CAP triggers intracellular pathways that induce growth inhibition or cell death. We discuss what factors may contribute to the potential selectivity of CAP towards cancer cells compared to their non-malignant counterparts. Furthermore, the potential of CAP to trigger an immune response is briefly discussed. Finally, this overview demonstrates how these concepts bear first fruits in clinical applications applying CAP treatment in head and neck squamous cell cancer as well as actinic keratosis. Although significant progress towards understanding the underlying mechanisms regarding the efficacy of CAP in cancer treatment has been made, much still needs to be done with respect to different treatment conditions and comparison of malignant and non-malignant cells of the same cell type and same donor. Furthermore, clinical pilot studies and the assessment of systemic effects will be of tremendous importance towards bringing this innovative technology into clinical practice.
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Affiliation(s)
- Marie Luise Semmler
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
| | - Sander Bekeschus
- ZIK plasmatis, Leibniz-Institute for Plasma Science and Technology (INP Greifswald), 17489 Greifswald, Germany; (S.B.); (T.v.W.)
| | - Mirijam Schäfer
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
| | - Thoralf Bernhardt
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
| | - Tobias Fischer
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
| | - Katharina Witzke
- Oral & Maxillofacial Surgery/Plastic Surgery, University Medicine Greifswald, 17489 Greifswald, Germany; (K.W.); (C.S.)
| | - Christian Seebauer
- Oral & Maxillofacial Surgery/Plastic Surgery, University Medicine Greifswald, 17489 Greifswald, Germany; (K.W.); (C.S.)
| | - Henrike Rebl
- Department of Cell Biology, University Medical Center Rostock, 18057 Rostock, Germany; (H.R.); (J.B.N.)
| | - Eberhard Grambow
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany; (E.G.); (B.V.)
| | - Brigitte Vollmar
- Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany; (E.G.); (B.V.)
| | - J. Barbara Nebe
- Department of Cell Biology, University Medical Center Rostock, 18057 Rostock, Germany; (H.R.); (J.B.N.)
| | - Hans-Robert Metelmann
- Oral & Maxillofacial Surgery/Plastic Surgery, University Medicine Greifswald, 17489 Greifswald, Germany; (K.W.); (C.S.)
| | - Thomas von Woedtke
- ZIK plasmatis, Leibniz-Institute for Plasma Science and Technology (INP Greifswald), 17489 Greifswald, Germany; (S.B.); (T.v.W.)
| | - Steffen Emmert
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
| | - Lars Boeckmann
- Clinic and Polyclinic for Dermatology and Venereology, University Medical Center Rostock, 18057 Rostock, Germany; (M.L.S.); (M.S.); (T.B.); (T.F.); (S.E.)
- Correspondence: ; Tel.: +49-381-494-9760
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20
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Usuda H, Hishida M, Kelley EG, Yamamura Y, Nagao M, Saito K. Interleaflet coupling of n-alkane incorporated bilayers. Phys Chem Chem Phys 2020; 22:5418-5426. [PMID: 31904060 DOI: 10.1039/c9cp06059f] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The relationship between the membrane bending modulus (κ) and compressibility modulus (KA) depends on the extent of coupling between the two monolayers (leaflets). Using neutron spin echo (NSE) spectroscopy, we investigate the effects of n-alkanes on the interleaflet coupling of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers. Structural studies with small-angle X-ray and neutron scattering (SAXS and SANS) showed that the bilayer thickness increased with increasing n-alkane length, while NSE suggested that the bilayers became softer. Additional measurements of the membrane thickness fluctuations with NSE suggested that the changes in elastic moduli were due to a decrease in coupling between the leaflets upon addition of the longer n-alkanes. The decreased coupling with elongating n-alkane length was explained based on the n-alkane distribution within the bilayers characterized by SANS measurement of bilayers composed of protiated DPPC and deuterated n-alkanes. A higher fraction of the incorporated long n-alkanes were concentrated at the central plane of the bilayers and decreased the physical interaction between the leaflets. Using NSE and SANS, we successfully correlated changes in the mesoscopic collective dynamics and microscopic membrane structure upon incorporation of n-alkanes.
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Affiliation(s)
- Hatsuho Usuda
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
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21
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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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22
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Interaction of cholesterol with artificial bilayer lipid membrane system and development of an electrochemical sensor. ARAB J CHEM 2020. [DOI: 10.1016/j.arabjc.2017.05.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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23
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Melcrová A, Pokorna S, Vošahlíková M, Sýkora J, Svoboda P, Hof M, Cwiklik L, Jurkiewicz P. Concurrent Compression of Phospholipid Membranes by Calcium and Cholesterol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:11358-11368. [PMID: 31393734 DOI: 10.1021/acs.langmuir.9b00477] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Regulation of cell metabolism, membrane fusion, association of proteins with cellular membranes, and cellular signaling altogether would not be possible without Ca2+ ions. The distribution of calcium within the cell is uneven with the negatively charged inner leaflet of the plasma membrane being one of the primary targets of its accumulation. Therefore, we decided to map the influence of Ca2+ on the properties of lipid bilayers closely resembling natural lipid membranes. We combined fluorescence spectroscopy (analysis of time-resolved emission spectra of Laurdan probe and derived parameters: integrated relaxation time related to local lipid mobility, and total emission shift reflecting membrane polarity and hydration) with molecular dynamics simulations to determine the effect of the increasing CaCl2 concentration on model lipid membranes containing POPC, POPS, and cholesterol. On top of that, the impact of calcium on the plasma membranes isolated from HEK293 cells was investigated using the steady-state fluorescence of Laurdan. We found that calcium increases rigidity of all the model lipid membranes used, elevates their thickness, increases lipid packing and ordering, and impedes the local lipid mobility. All these effects were to a great extent similar to those elicited by cholesterol. However, the changes of the membrane properties induced by calcium and cholesterol seem largely independent from each other. At sufficiently high concentrations of calcium or cholesterol, the steric effects hindered a further alteration of membrane organization, i.e., the compressibility limit of membrane structures was reached. We found no indication for mutual interaction between Ca2+ and cholesterol, nor competition of Ca2+ ions and hydroxyl groups of cholesterol for binding to phospholipids. Fluorescence measurements indicated that Ca2+ adsorption decreases mobility within the carbonyl region of model bilayers more efficiently than monovalent ions do (Ca2+ ≫ Li+ > Na+ > K+ > Cs+). The effects of calcium ions were to a great extent mitigated in the plasma membranes isolated from HEK293 cells when compared to the model lipid membranes. Noticeably, the plasma membranes showed remarkably higher resistance toward rigidification induced by calcium ions even when compared with the model membranes containing cholesterol.
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Affiliation(s)
- Adéla Melcrová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
| | - Sarka Pokorna
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
| | - Miroslava Vošahlíková
- Institute of Physiology of the Czech Academy of Sciences , Vídeňská 1083 , 14220 Prague 4 , Czech Republic
| | - Jan Sýkora
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
| | - Petr Svoboda
- Institute of Physiology of the Czech Academy of Sciences , Vídeňská 1083 , 14220 Prague 4 , Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences , 166 10 Prague 6 , Czech Republic
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , 182 23 Prague 8 , Czech Republic
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24
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Lemma T, Marques Ruiz GC, Oliveira ON, Constantino CJ. The pesticide picloram affects biomembrane models made with Langmuir monolayers. Colloids Surf B Biointerfaces 2019; 181:953-958. [DOI: 10.1016/j.colsurfb.2019.06.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 06/18/2019] [Accepted: 06/25/2019] [Indexed: 11/15/2022]
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25
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Yadav DK, Kumar S, Choi EH, Chaudhary S, Kim MH. Molecular dynamic simulations of oxidized skin lipid bilayer and permeability of reactive oxygen species. Sci Rep 2019; 9:4496. [PMID: 30872693 PMCID: PMC6418262 DOI: 10.1038/s41598-019-40913-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 02/26/2019] [Indexed: 12/30/2022] Open
Abstract
Lipid peroxidation by reactive oxygen species (ROS) during oxidative stress is non-enzymatic damage that affects the integrity of biological membrane, and alters the fluidity and permeability. We conducted molecular dynamic simulation studies to evaluate the structural properties of the bilayer after lipid peroxidation and to measure the permeability of distinct ROS. The oxidized membrane contains free fatty acid, ceramide, cholesterol, and 5α-hydroperoxycholesterol (5α-CH). The result of unconstrained molecular dynamic simulations revealed that lipid peroxidation causes area-per-lipid of the bilayer to increase and bilayer thickness to decrease. The simulations also revealed that the oxidized group of 5α-CH (-OOH) moves towards the aqueous layer and its backbone tilts causing lateral expansion of the bilayer membrane. These changes are detrimental to structural and functional properties of the membrane. The measured free energy profile for different ROS (H2O2, HO2, HO, and O2) across the peroxidized lipid bilayer showed that the increase in lipid peroxidation resulted in breaching barrier decrease for all species, allowing easy traversal of the membrane. Thus, lipid peroxidation perturbs the membrane barrier and imposes oxidative stress resulting into apoptosis. The collective insights increase the understanding of oxidation stress at the atomic level.
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Affiliation(s)
- Dharmendra Kumar Yadav
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, Incheon, 406-799, South Korea.
| | - Surendra Kumar
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, Incheon, 406-799, South Korea
| | - Eun-Ha Choi
- Plasma Bioscience Research Center/PDP Research Center, Kwangwoon University, Nowon-Gu, Seoul, 139-791, Korea
| | - Sandeep Chaudhary
- Laboratory of Organic and Medicinal Chemistry, Department of Chemistry, Malaviya National Institute of Technology, Jaipur, 302017, India
| | - Mi-Hyun Kim
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, Incheon, 406-799, South Korea.
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26
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Kheyfets B, Galimzyanov T, Mukhin S. Lipid lateral self-diffusion drop at liquid-gel phase transition. Phys Rev E 2019; 99:012414. [PMID: 30780230 DOI: 10.1103/physreve.99.012414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Indexed: 11/06/2022]
Abstract
A drop of lipid lateral self-diffusion coefficient at the liquid-gel phase transition in lipid membranes is calculated. So far this drop was missing theoretical description. Our microscopic model captures so-called subdiffusion regime, which takes place on 1 ps-100 ns timescale and reveals a jump of self-diffusion coefficient. Calculation of the jump is based on our recent study of liquid-gel phase transition. Subdiffusive regime is described within the free volume theory. Calculated values of self-diffusion coefficient are in agreement with quasielastic neutron scattering measurements. Self-diffusion coefficient is found to be composed of two factors: one is related to an area per lipid change at the phase transition, and the other one is due to an order of magnitude change in the stiffness of entropic repulsive potential.
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Affiliation(s)
- Boris Kheyfets
- National University of Science and Technology MISIS, Moscow, Russia
| | - Timur Galimzyanov
- A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Moscow, Russia
| | - Sergei Mukhin
- National University of Science and Technology MISIS, Moscow, Russia
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27
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Ermilova I, Lyubartsev AP. Cholesterol in phospholipid bilayers: positions and orientations inside membranes with different unsaturation degrees. SOFT MATTER 2018; 15:78-93. [PMID: 30520494 DOI: 10.1039/c8sm01937a] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Cholesterol is an essential component of all animal cell membranes and plays an important role in maintaining the membrane structure and physical-chemical properties necessary for correct cell functioning. The presence of cholesterol is believed to be responsible for domain formation (lipid rafts) due to different interactions of cholesterol with saturated and unsaturated lipids. In order to get detailed atomistic insight into the behaviour of cholesterol in bilayers composed of lipids with varying degrees of unsaturation, we have carried out a series of molecular dynamics simulations of saturated and polyunsaturated lipid bilayers with different contents of cholesterol, as well as well-tempered metadynamics simulations with a single cholesterol molecule in these bilayers. From these simulations we have determined distributions of cholesterol across the bilayer, its orientational properties, free energy profiles, and specific interactions of molecular groups able to form hydrogen bonds. Both molecular dynamics and metadynamics simulations showed that the most unsaturated bilayer with 22:6 fatty acid chains shows behaviour which is most different from other lipids. In this bilayer, cholesterol is relatively often found in a "flipped" configuration with the hydroxyl group oriented towards the membrane middle plane. This bilayer has also the highest (least negative) binding free energy among liquid phase bilayers, and the lowest reorientation barrier. Furthermore, cholesterol molecules in this bilayer are often found to form head-to-tail contacts which may lead to specific clustering behaviour. Overall, our simulations support ideas that there can be a subtle interconnection between the contents of highly unsaturated fatty acids and cholesterol, deficiency or excess of each of them is related to many human afflictions and diseases.
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Affiliation(s)
- Inna Ermilova
- Department of Materials and Environmental Chemistry, Stockholm Universtity, Stockholm, Sweden.
| | - Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry, Stockholm Universtity, Stockholm, Sweden.
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28
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Hantal G, Fábián B, Sega M, Jójárt B, Jedlovszky P. Effect of general anesthetics on the properties of lipid membranes of various compositions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:594-609. [PMID: 30571949 DOI: 10.1016/j.bbamem.2018.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/05/2018] [Accepted: 12/13/2018] [Indexed: 10/27/2022]
Abstract
Computer simulations of four lipid membranes of different compositions, namely neat DPPC and PSM, and equimolar DPPC-cholesterol and PSM-cholesterol mixtures, are performed in the presence and absence of the general anesthetics diethylether and sevoflurane both at 1 and 600 bar. The results are analyzed in order to identify membrane properties that are potentially related to the molecular mechanism of anesthesia, namely that change in the same way in any membrane with any anesthetics, and change oppositely with increasing pressure. We find that the lateral lipid density satisfies both criteria: it is decreased by anesthetics and increased by pressure. This anesthetic-induced swelling is attributed to only those anesthetic molecules that are located close to the boundary of the apolar phase. This lateral expansion is found to lead to increased lateral mobility of the lipids, an effect often thought to be related to general anesthesia; to an increased fraction of the free volume around the outer preferred position of anesthetics; and to the decrease of the lateral pressure in the nearby range of the ester and amide groups, a region into which anesthetic molecules already cannot penetrate. All these changes are reverted by the increase of pressure. Another important finding of this study is that cholesterol has an opposite effect on the membrane properties than anesthetics, and, correspondingly, these changes are less marked in the presence of cholesterol. Therefore, changes in the membrane that can lead to general anesthesia are expected to occur in the membrane domains of low cholesterol content.
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Affiliation(s)
- György Hantal
- Faculty of Physics, University of Vienna, Sensengasse 8/9, A-1090 Vienna, Austria
| | - Balázs Fábián
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellért tér 4, H-1111 Budapest, Hungary; Institut UTINAM (CNRS UMR 6213), Université Bourgogne Franche-Comté, 16 route de Gray, F-25030 Besançon, France
| | - Marcello Sega
- Faculty of Physics, University of Vienna, Sensengasse 8/9, A-1090 Vienna, Austria
| | - Balázs Jójárt
- Institute of Food Engineering, University of Szeged, Moszkvai krt 5-7, H-6725 Szeged, Hungary
| | - Pál Jedlovszky
- Department of Chemistry, Eszterházy Károly University, Leányka utca 6, H-3300 Eger, Hungary.
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29
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Lu H, Martí J. Effects of cholesterol on the binding of the precursor neurotransmitter tryptophan to zwitterionic membranes. J Chem Phys 2018; 149:164906. [PMID: 30384712 DOI: 10.1063/1.5029430] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The characterization of the microscopical forces between the essential α-amino-acid tryptophan, precursor of the neurotransmitter serotonin and of the hormone melatonin, and the basic components of cell membranes and their environments (phospholipids, cholesterol, ionic species, and water) is of central importance to elucidate their local structure and dynamics as well as the mechanisms responsible for the access of tryptophan to the interior of the cell. We have performed nanosecond molecular dynamics simulations of tryptophan embedded in model zwitterionic bilayer membranes made by di-palmitoyl-phosphatidyl-choline and cholesterol inside aqueous sodium-chloride solution in order to systematically examine tryptophan-lipid, tryptophan-cholesterol, and tryptophan-water interactions under liquid-crystalline phase conditions. Microscopic properties such as the area per lipid, lipid thickness, radial distribution functions, hydrogen-bonding lengths, atomic spectral densities, and self-diffusion coefficients have been evaluated. Our results show that the presence of tryptophan significantly affects the structure and dynamics of the membrane. Tryptophan spends long periods of time at the water-membrane interface, and it plays a central role by bridging a few lipids and cholesterol chains by means of hydrogen-bonds. The computed spectral densities, in excellent agreement with experimental infrared and Raman data, revealed the participation of each atomic site of tryptophan to the complete spectrum of the molecule. Tryptophan self-diffusion coefficients have been found to be in between 10-7 and 10-6 cm2/s and strongly depending of the concentration of cholesterol in the system.
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Affiliation(s)
- Huixia Lu
- Department of Physics, Technical University of Catalonia-Barcelona Tech, B4-210 Northern Campus UPC, 08034 Barcelona, Catalonia, Spain
| | - Jordi Martí
- Department of Physics, Technical University of Catalonia-Barcelona Tech, B5-209 Northern Campus UPC, 08034 Barcelona, Catalonia, Spain
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30
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Kimchi O, Veatch SL, Machta BB. Ion channels can be allosterically regulated by membrane domains near a de-mixing critical point. J Gen Physiol 2018; 150:1769-1777. [PMID: 30455180 PMCID: PMC6279359 DOI: 10.1085/jgp.201711900] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 08/24/2018] [Accepted: 10/25/2018] [Indexed: 12/17/2022] Open
Abstract
Ion channels are embedded in the plasma membrane, a compositionally diverse two-dimensional liquid that has the potential to exert profound influence on their function. Recent experiments suggest that this membrane is poised close to an Ising critical point, below which cell-derived plasma membrane vesicles phase separate into coexisting liquid phases. Related critical points have long been the focus of study in simplified physical systems, but their potential roles in biological function have been underexplored. Here we apply both exact and stochastic techniques to the lattice Ising model to study several ramifications of proximity to criticality for idealized lattice channels, whose function is coupled through boundary interactions to critical fluctuations of membrane composition. Because of diverging susceptibilities of system properties to thermodynamic parameters near a critical point, such a lattice channel's activity becomes strongly influenced by perturbations that affect the critical temperature of the underlying Ising model. In addition, its kinetics acquire a range of time scales from its surrounding membrane, naturally leading to non-Markovian dynamics. Our model may help to unify existing experimental results relating the effects of small-molecule perturbations on membrane properties and ion channel function. We also suggest ways in which the role of this mechanism in regulating real ion channels and other membrane-bound proteins could be tested in the future.
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Affiliation(s)
- Ofer Kimchi
- Department of Physics, Princeton University, Princeton, NJ.,Harvard Graduate Program in Biophysics, Harvard University, Cambridge, MA
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, MI
| | - Benjamin B Machta
- Department of Physics, Princeton University, Princeton, NJ .,Lewis-Sigler Institute, Princeton University, Princeton, NJ.,Department of Physics, Yale University, New Haven, CT.,Systems Biology Institute, Yale University, West Haven, CT
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31
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Srivastava SR, Zadafiya P, Mahalakshmi R. Hydrophobic Mismatch Modulates Stability and Plasticity of Human Mitochondrial VDAC2. Biophys J 2018; 115:2386-2394. [PMID: 30503532 PMCID: PMC6301912 DOI: 10.1016/j.bpj.2018.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 10/15/2018] [Accepted: 11/01/2018] [Indexed: 01/13/2023] Open
Abstract
The human mitochondrial outer membrane protein voltage-dependent anion channel isoform 2 (hVDAC2) is a β-barrel metabolite flux channel that is indispensable for cell survival. It is well established that physical forces imposed on a transmembrane protein by its surrounding lipid environment decide protein structure and stability. Yet, how the mitochondrial membrane and protein-lipid interplay together regulate hVDAC2 stability is unknown. Here, we combine experimental biophysical investigations of protein stability with all-atom molecular dynamics simulations to study the effect of the most abundant mitochondrial phosphocholine (PC) lipids on hVDAC2. We demonstrate experimentally that increasing the PC lipid acyl chain length from diC14:0 to diC18:0-PC has a nonlinear effect on the β-barrel. We show that protein stability is highest in diC16:0-PC, which exhibits a negative mismatch with the hVDAC2 barrel. Our simulations also reveal that structural rigidity of hVDAC2 is highest under optimal negative mismatch provided by diC16:0-PC bilayers. Further, we validate our observations by altering the physical properties of PC membranes indirectly using cholesterol. We propose that VDAC plasticity and stability in the mitochondrial outer membrane are modulated by physical properties of the bilayer.
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Affiliation(s)
- Shashank Ranjan Srivastava
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Punit Zadafiya
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India.
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32
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Leeb F, Maibaum L. Spatially Resolving the Condensing Effect of Cholesterol in Lipid Bilayers. Biophys J 2018; 115:2179-2188. [PMID: 30447996 DOI: 10.1016/j.bpj.2018.10.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 10/15/2018] [Accepted: 10/24/2018] [Indexed: 11/15/2022] Open
Abstract
We study the effect of cholesterol on the structure of dipalmitoylphosphatidylcholine phospholipid bilayers. Using extensive molecular dynamics computer simulations at atomistic resolution, we observe and quantify several structural changes upon increasing cholesterol content that are collectively known as the condensing effect: a thickening of the bilayer, an increase in lipid tail order, and a decrease in lateral area. We also observe a change in leaflet interdigitation and a lack thereof in the distributions of dipalmitoylphosphatidylcholine headgroup orientations. These results, obtained over a wide range of cholesterol mole fractions, are then used to calibrate the analysis of phospholipid properties in bilayers containing a single cholesterol molecule per leaflet, which we perform in a spatially resolved way. We find that a single cholesterol molecule affects phospholipids in its first and second solvation shells, which puts the range of this effective interaction to be on the order of 1-2 nm. We also observe a tendency of phospholipids to orient their polar headgroups toward the cholesterol, which provides additional support for the umbrella model of bilayer organization.
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Affiliation(s)
- Felix Leeb
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Lutz Maibaum
- Department of Chemistry, University of Washington, Seattle, Washington.
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33
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Lu H, Marti J. Binding free energies of small-molecules in phospholipid membranes: Aminoacids, serotonin and melatonin. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Atkovska K, Klingler J, Oberwinkler J, Keller S, Hub JS. Rationalizing Steroid Interactions with Lipid Membranes: Conformations, Partitioning, and Kinetics. ACS CENTRAL SCIENCE 2018; 4:1155-1165. [PMID: 30276248 PMCID: PMC6161064 DOI: 10.1021/acscentsci.8b00332] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Indexed: 05/18/2023]
Abstract
Steroids have numerous physiological functions associated with cellular signaling or modulation of the lipid membrane structure and dynamics, and as such, they have found broad pharmacological applications. Steroid-membrane interactions are relevant to multiple steps of steroid biosynthesis and action, as steroids are known to interact with neurotransmitter or membrane steroid receptors, and steroids must cross lipid membranes to exert their physiological functions. Therefore, rationalizing steroid function requires understanding of steroid-membrane interactions. We combined molecular dynamics simulations and isothermal titration calorimetry to characterize the conformations and the energetics of partitioning, in addition to the kinetics of flip-flop transitions and membrane exit, of 26 representative steroid compounds in a model lipid membrane. The steroid classes covered in this study include birth control and anabolic drugs, sex and corticosteroid hormones, neuroactive steroids, as well as steroids modulating the lipid membrane structure. We found that the conformational ensembles adopted by different steroids vary greatly, as quantified by their distributions of tilt angles and insertion depths into the membrane, ranging from well-defined steroid conformations with orientations either parallel or normal to the membrane, to wide conformational distributions. Surprisingly, despite their chemical diversity, the membrane/water partition coefficient is similar among most steroids, except for structural steroids such as cholesterol, leading to similar rates for exiting the membrane. By contrast, the rates of steroid flip-flop vary by at least 9 orders of magnitude, revealing that flip-flop is the rate-limiting step during cellular uptake of polar steroids. This study lays the ground for a quantitative understanding of steroid-membrane interactions, and it will hence be of use for studies of steroid biosynthesis and function as well as for the development and usage of steroids in a pharmacological context.
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Affiliation(s)
- Kalina Atkovska
- Institute
for Microbiology and Genetics and Goettingen Center for Molecular
Biosciences, University of Goettingen, 37077 Göttingen, Germany
| | - Johannes Klingler
- Molecular
Biophysics, Technische Universität
Kaiserslautern (TUK), 67663 Kaiserslautern, Germany
| | - Johannes Oberwinkler
- Institut
für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Sandro Keller
- Molecular
Biophysics, Technische Universität
Kaiserslautern (TUK), 67663 Kaiserslautern, Germany
| | - Jochen S. Hub
- Institute
for Microbiology and Genetics and Goettingen Center for Molecular
Biosciences, University of Goettingen, 37077 Göttingen, Germany
- Theoretical
Physics, Saarland University, 66123 Saarbrücken, Germany
- E-mail:
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35
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Parameterization of a coarse-grained model of cholesterol with point-dipole electrostatics. J Comput Aided Mol Des 2018; 32:1259-1271. [DOI: 10.1007/s10822-018-0164-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 09/12/2018] [Indexed: 12/14/2022]
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36
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Kumar S, Yadav DK, Choi EH, Kim MH. Insight from Molecular dynamic simulation of reactive oxygen species in oxidized skin membrane. Sci Rep 2018; 8:13271. [PMID: 30185881 PMCID: PMC6125594 DOI: 10.1038/s41598-018-31609-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 08/10/2018] [Indexed: 11/08/2022] Open
Abstract
Non-enzymatic lipid peroxidation of the skin-lipid bilayer causes perturbations that affect the biomembrane structure, function, and permeability of reactive oxygen species (ROS). In the present study, we employed molecular dynamics simulations to study the effect of lipid peroxidation on the bilayer structural properties and permeability of various ROS. The oxidized skin-lipid bilayer was composed of ceramide, cholesterol, free fatty acid, and 5α-hydroperoxycholesterol (5α-CH). The simulation showed that, upon oxidation, the oxidized group (-OOH) of 5α-CH migrates towards the aqueous phase and the backbone of 5α-CH tilts, which causes the membrane to expand laterally. Measurements of the permeability of all ROS along the oxidized skin-lipid bilayer revealed a decreased breaching barrier for all the species as the degree of peroxidation increased, with a resulting easy passage across the membrane. The insights from the simulations indicate that lipid peroxidation might perturb the membrane barrier, thereby inflicting oxidative stress that leads to apoptosis. This study helps to understand oxidative stress at the atomic level. To our knowledge, this is the first reported molecular dynamics simulation study on oxidized skin-lipid bilayer and permeability of ROS.
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Affiliation(s)
- Surendra Kumar
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, 191, Hambakmoeiro, Yeonsu-gu, Incheon, 406-799, Korea
| | - Dharmendra Kumar Yadav
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, 191, Hambakmoeiro, Yeonsu-gu, Incheon, 406-799, Korea.
| | - Eun-Ha Choi
- Plasma Bioscience Research Center/PDP Research Center, Kwangwoon University, Nowon-Gu, Seoul, 139-791, Korea
| | - Mi-Hyun Kim
- Gachon Institute of Pharmaceutical Science & Department of Pharmacy, College of Pharmacy, Gachon University, 191, Hambakmoeiro, Yeonsu-gu, Incheon, 406-799, Korea.
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37
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Skalová Š, Vyskočil V, Barek J, Navrátil T. Model Biological Membranes and Possibilities of Application of Electrochemical Impedance Spectroscopy for their Characterization. ELECTROANAL 2017. [DOI: 10.1002/elan.201700649] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Štěpánka Skalová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences; Dolejškova 3 182 23 Prague 8 Czech Republic
- Charles University; Faculty of Science, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Vlastimil Vyskočil
- Charles University; Faculty of Science, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Jiří Barek
- Charles University; Faculty of Science, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Tomáš Navrátil
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences; Dolejškova 3 182 23 Prague 8 Czech Republic
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38
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Barragán Vidal IA, Müller M. Generalization of the swelling method to measure the intrinsic curvature of lipids. J Chem Phys 2017; 147:224902. [PMID: 29246037 DOI: 10.1063/1.5001858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Via computer simulation of a coarse-grained model of two-component lipid bilayers, we compare two methods of measuring the intrinsic curvatures of the constituting monolayers. The first one is a generalization of the swelling method that, in addition to the assumption that the spontaneous curvature linearly depends on the composition of the lipid mixture, incorporates contributions from its elastic energy. The second method measures the effective curvature-composition coupling between the apposing leaflets of bilayer structures (planar bilayers or cylindrical tethers) to extract the spontaneous curvature. Our findings demonstrate that both methods yield consistent results. However, we highlight that the two-leaflet structure inherent to the latter method has the advantage of allowing measurements for mixed lipid systems up to their critical point of demixing as well as in the regime of high concentration (of either species).
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Affiliation(s)
- I A Barragán Vidal
- Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - M Müller
- Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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39
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Van der Paal J, Verheyen C, Neyts EC, Bogaerts A. Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity. Sci Rep 2017; 7:39526. [PMID: 28059085 PMCID: PMC5216346 DOI: 10.1038/srep39526] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 11/23/2016] [Indexed: 11/08/2022] Open
Abstract
In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane.
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Affiliation(s)
- Jonas Van der Paal
- Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp, Belgium
| | - Claudia Verheyen
- Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp, Belgium
| | - Erik C. Neyts
- Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp, Belgium
| | - Annemie Bogaerts
- Research group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp, Belgium
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40
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Parikh N, Klimov DK. Inclusion of lipopeptides into the DMPC lipid bilayers prevents Aβ peptide insertion. Phys Chem Chem Phys 2017; 19:10087-10098. [DOI: 10.1039/c7cp01003f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lipopeptides prevent penetration of Alzheimer's Aβ peptides into lipid bilayers.
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Affiliation(s)
- Niyati Parikh
- School of Systems Biology
- George Mason University
- Manassas
- USA
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41
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Marquardt D, Kučerka N, Wassall SR, Harroun TA, Katsaras J. Cholesterol's location in lipid bilayers. Chem Phys Lipids 2016; 199:17-25. [DOI: 10.1016/j.chemphyslip.2016.04.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 04/01/2016] [Accepted: 04/02/2016] [Indexed: 02/07/2023]
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42
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Wang Y, Gkeka P, Fuchs JE, Liedl KR, Cournia Z. DPPC-cholesterol phase diagram using coarse-grained Molecular Dynamics simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2846-2857. [PMID: 27526680 DOI: 10.1016/j.bbamem.2016.08.005] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 08/06/2016] [Accepted: 08/11/2016] [Indexed: 12/30/2022]
Abstract
Cholesterol-phospholipid bilayers continue to be the current state of the art in membrane models and serve as representative systems for studying the effect of cholesterol on the cell membrane. As the mixing of different lipid species requires long spatio-temporal scales, coarse-grained models have gained increasing popularity in modeling such membrane systems. In this paper, a systematic study of the MARTINI coarse-grained model for the DPPC-cholesterol binary system has been performed. We construct the phase diagram of DPPC lipid bilayers in the presence of different cholesterol concentrations and at different temperatures using coarse-grained Molecular Dynamics (MD) simulations with the MARTINI force field. The phase diagram based on the condensation effect is directly comparable to available experimental data and demonstrates qualitative agreement over all cholesterol concentrations. Self-assembled bilayers quantitatively reproduce experimental observables, such as lateral diffusion of lipids, electron density, area per lipid and lipid order parameters. The phase diagram of the DPPC-cholesterol binary system also reveals the profound effect of cholesterol on the physical properties of phospholipid bilayers such lipid order, diffusion, and fluidity. Cholesterol induces the liquid-ordered phase, which increases the fluidity of the phospholipid hydrocarbon chains above the gel to liquid-crystalline phase transition temperature and decreases it below the phase transition. The present study suggests that the MARTINI force field can be successfully used to obtain molecular level insights into cholesterol-DPPC model membranes.
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Affiliation(s)
- Yin Wang
- Department of Theoretical Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Paraskevi Gkeka
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527, Athens, Greece
| | - Julian E Fuchs
- Department of Theoretical Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Klaus R Liedl
- Department of Theoretical Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria.
| | - Zoe Cournia
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527, Athens, Greece.
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43
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Wang M, Chen J, Lian T, Zhan W. Mimicking Photosynthesis with Supercomplexed Lipid Nanoassemblies: Design, Performance, and Enhancement Role of Cholesterol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7326-7338. [PMID: 27352779 DOI: 10.1021/acs.langmuir.6b01608] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report here a new approach to mimicking photosynthesis that relies on supercomplexed lipid nanoassemblies to organize small organic species for coordinated light harvesting, energy/electron transfer, and photo-to-electrochemical energy conversion. Specifically, we demonstrate efficient photoinduced electron transfer (PeT) between rhodamine and fullerene assembled together via electrostatically bound liposome and lipid bilayer hosts. The remarkable impact of the lipid matrix on the photoconversion efficiency is further revealed by cholesterol, whose addition is found to modify the distribution and organization of the coassembled rhodamine dyes and thus their photodynamics. This significantly expedites the energy transfer (ET) among rhodamine dyes, as well as the PeT between rhodamines and fullerenes. A respectable 14% photon-to-electron conversion efficiency was achieved for this supercomplexed system containing 5% rhodamines, 5% fullerenes, and 30% cholesterol. The morphology, photodynamics, and photoelectrochemical behavior of these lipid supercomplexes were thoroughly characterized using atomic force microscopy (AFM), fluorescence microscopy, steady-state and time-resolved fluorescence spectroscopy, and transient absorption (TA) and photoaction spectroscopy. A detailed discussion on enhancement mechanisms of cholesterol in this lipid-complexed photosynthesis-mimicking system is provided at the end.
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Affiliation(s)
- Mingming Wang
- Department of Chemistry and Biochemistry, Auburn University , Auburn, Alabama 36849, United States
| | - Jinquan Chen
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| | - Tianquan Lian
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| | - Wei Zhan
- Department of Chemistry and Biochemistry, Auburn University , Auburn, Alabama 36849, United States
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44
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Barriga HMG, Law RV, Seddon JM, Ces O, Brooks NJ. The effect of hydrostatic pressure on model membrane domain composition and lateral compressibility. Phys Chem Chem Phys 2016; 18:149-55. [DOI: 10.1039/c5cp04239a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We distinguish the liquid ordered and liquid disordered phases in diffraction patterns of biphasic mixtures, comparing their lateral compressibility and report the variations in the two phase region with increasing hydrostatic pressure.
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Affiliation(s)
| | - R. V. Law
- Department of Chemistry
- Imperial College London
- UK
| | - J. M. Seddon
- Department of Chemistry
- Imperial College London
- UK
| | - O. Ces
- Department of Chemistry
- Imperial College London
- UK
| | - N. J. Brooks
- Department of Chemistry
- Imperial College London
- UK
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45
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Van der Paal J, Neyts EC, Verlackt CCW, Bogaerts A. Effect of lipid peroxidation on membrane permeability of cancer and normal cells subjected to oxidative stress. Chem Sci 2016; 7:489-498. [PMID: 28791102 PMCID: PMC5518669 DOI: 10.1039/c5sc02311d] [Citation(s) in RCA: 220] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/14/2015] [Indexed: 12/19/2022] Open
Abstract
We performed molecular dynamics simulations to investigate the effect of lipid peroxidation products on the structural and dynamic properties of the cell membrane. Our simulations predict that the lipid order in a phospholipid bilayer, as a model system for the cell membrane, decreases upon addition of lipid peroxidation products. Eventually, when all phospholipids are oxidized, pore formation can occur. This will allow reactive species, such as reactive oxygen and nitrogen species (RONS), to enter the cell and cause oxidative damage to intracellular macromolecules, such as DNA or proteins. On the other hand, upon increasing the cholesterol fraction of lipid bilayers, the cell membrane order increases, eventually reaching a certain threshold, from which cholesterol is able to protect the membrane against pore formation. This finding is crucial for cancer treatment by plasma technology, producing a large number of RONS, as well as for other cancer treatment methods that cause an increase in the concentration of extracellular RONS. Indeed, cancer cells contain less cholesterol than their healthy counterparts. Thus, they will be more vulnerable to the consequences of lipid peroxidation, eventually enabling the penetration of RONS into the interior of the cell, giving rise to oxidative stress, inducing pro-apoptotic factors. This provides, for the first time, molecular level insight why plasma can selectively treat cancer cells, while leaving their healthy counterparts undamaged, as is indeed experimentally demonstrated.
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Affiliation(s)
- Jonas Van der Paal
- Research Group PLASMANT , Department of Chemistry , University of Antwerp , Universiteitsplein 1 , B-2610 Wilrijk , Antwerp , Belgium .
| | - Erik C Neyts
- Research Group PLASMANT , Department of Chemistry , University of Antwerp , Universiteitsplein 1 , B-2610 Wilrijk , Antwerp , Belgium .
| | - Christof C W Verlackt
- Research Group PLASMANT , Department of Chemistry , University of Antwerp , Universiteitsplein 1 , B-2610 Wilrijk , Antwerp , Belgium .
| | - Annemie Bogaerts
- Research Group PLASMANT , Department of Chemistry , University of Antwerp , Universiteitsplein 1 , B-2610 Wilrijk , Antwerp , Belgium .
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46
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Hane FT, Drolle E, Leonenko Z. Amyloid-β (1-40) restores adhesion properties of pulmonary surfactant, counteracting the effect of cholesterol. Phys Chem Chem Phys 2015; 16:15430-6. [PMID: 24947303 DOI: 10.1039/c4cp00040d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A pulmonary surfactant (PS) is a thin lipid-protein film covering the surface of the lung alveoli at the air/liquid interface. The primary purpose of a PS is to control the surface tension of the air/liquid interface and to reduce the work of breathing. High levels of cholesterol in a PS are associated with life-threatening acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Finding therapeutics to counteract the effect of cholesterol in a PS is a matter of contemporary research. In our earlier work, we showed that the addition of amyloid-β (1-40) (Aβ40), the protein implicated in Alzheimer's disease, can reverse the detrimental effects of cholesterol in surfactants by improving multilayer formation and restoring PS surface active properties. We hypothesized that this phenomenon was due to Aβ40 improving adhesion properties of a surfactant. In this work we used atomic force spectroscopy to demonstrate that Aβ40 counteracts the adhesive properties of a PS compromised by high levels of cholesterol in a PS and helps to restore the functionality of a PS.
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Affiliation(s)
- F T Hane
- Department of Biology, University of Waterloo, 200 University Ave, Waterloo, ON N2L 3G1, Canada
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Taylor GJ, Venkatesan GA, Collier CP, Sarles SA. Direct in situ measurement of specific capacitance, monolayer tension, and bilayer tension in a droplet interface bilayer. SOFT MATTER 2015; 11:7592-605. [PMID: 26289743 DOI: 10.1039/c5sm01005e] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow for determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance.
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Affiliation(s)
- Graham J Taylor
- Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, 1512 Middle Drive, 414 Dougherty Engineering Building, Knoxville, TN 37996, USA.
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Gupta R, Rai B. Molecular Dynamics Simulation Study of Skin Lipids: Effects of the Molar Ratio of Individual Components over a Wide Temperature Range. J Phys Chem B 2015; 119:11643-55. [DOI: 10.1021/acs.jpcb.5b02093] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rakesh Gupta
- Tata Research Development
and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune - 411013, India
| | - Beena Rai
- Tata Research Development
and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune - 411013, India
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Jurak M, Golabek M, Holysz L, Chibowski E. Properties of Langmuir and solid supported lipid films with sphingomyelin. Adv Colloid Interface Sci 2015; 222:385-97. [PMID: 24725646 DOI: 10.1016/j.cis.2014.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 12/11/2022]
Abstract
Biological cell membranes play a crucial role in various biological processes and their functionality to some extent is determined by the hydrophilic/hydrophobic balance. A significant progress in understanding the membrane structure was the discovery of laterally segregated lipid domains, called the lipid rafts. These raft domains are of ordered lamellar liquid-crystalline phase, while rest of the membrane exists in a relatively disordered lamellar liquid-crystalline phase. Moreover, the chemical constitution of the lipid rafts consists of a higher content (up to 50%) of cholesterol (Chol) and sphingomyelin (SM). Sphingomyelin also plays a significant role in the red cells of blood and nerves, in some diseases, as a precursor to ceramides, and other sphingolipid metabolites. In this paper properties of Langmuir and solid supported mixed lipid films of DPPC/SM, DOPC/SM, and Chol/SM are described. Special attention has been paid to wetting properties (hydrophobic/hydrophilic balance) of these films transferred onto a hydrophilic glass surface. To our knowledge such results have not yet been published in the literature. The properties were determined via contact angle measurements and then calculation of the films' apparent surface free energy. The films' wettability and their apparent surface free energy strongly depend on their composition. The energy is affected by both the structure of hydrocarbon chains of glycerophospholipids (DPPC and DOPC) and their interactions with SM. Properties of mixed Chol/SM monolayer depend also on the film stoichiometry. At a low Chol content (XChol=0.25) the interactions between SM and Chol are strong and hence the formation of binary complex is possible. This is accompanied by a decrease in the film surface free energy in comparison to that of pure SM monolayer, contrary to a higher Chol content where the monolayer energy increases. This suggests that cholesterol is excluded from the membrane thus increasing the film hydrophilicity. These results are consistent with the literature data and somehow confirm the hypothesis of lipid raft formation. The roughness of the investigated monolayer surfaces was also determined using optical profilometry. The roughness parameters of the DPPC, SM, and mixed DPPC/SM generally correlate with the changes of their apparent surface free energy, i.e. with the decreasing roughness the apparent surface free energy also decreases. However, this is not the case for mixed DOPC/SM monolayers. Although the roughness increases with SM content the apparent surface free energy decreases. Therefore some other factors, like the presence of unsaturated bonds in the DOPC molecule, influence the film phase state and the energy too. More experiments are needed to explain this hypothesis.
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Issack BB, Peslherbe GH. Effects of Cholesterol on the Thermodynamics and Kinetics of Passive Transport of Water through Lipid Membranes. J Phys Chem B 2015; 119:9391-400. [DOI: 10.1021/jp510497r] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bilkiss B. Issack
- Centre for Research in Molecular
Modeling and Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, Québec H4B 1R6, Canada
| | - Gilles H. Peslherbe
- Centre for Research in Molecular
Modeling and Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, Québec H4B 1R6, Canada
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