1
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Benaglia S, Read H, Fumagalli L. Atomic-scale structure of interfacial water on gel and liquid phase lipid membranes. Faraday Discuss 2024; 249:453-468. [PMID: 37781876 PMCID: PMC10845012 DOI: 10.1039/d3fd00094j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 06/19/2023] [Indexed: 10/03/2023]
Abstract
Hydration of biological membranes is essential to a wide range of biological processes. In particular, it is intrinsically linked to lipid thermodynamic properties, which in turn influence key cell functions such as ion permeation and protein mobility. Experimental and theoretical studies of the surface of biomembranes have revealed the presence of an interfacial repulsive force, which has been linked to hydration or steric effects. Here, we directly characterise the atomic-scale structure of water near supported lipid membranes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine in their gel and liquid phase through three-dimensional atomic force microscopy (3D AFM). First, we demonstrate the ability to probe the morphology of interfacial water of lipid bilayers in both phases with sub-molecular resolution by using ultrasharp tips. We then visualise the molecular arrangement of water at the lipid surface at different temperatures. Our experiments reveal that water is organised in multiple hydration layers on both the solid-ordered and liquid-disordered lipid phases. Furthermore, we observe a monotonic repulsive force, which becomes relevant only in the liquid phase. These results offer new insights into the water structuring near soft biological surfaces, and demonstrate the importance of investigating it with vertical and lateral sub-molecular resolution.
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Affiliation(s)
- Simone Benaglia
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.
- National Graphene Institute, University of Manchester, M13 9PL, UK
| | - Harriet Read
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.
- National Graphene Institute, University of Manchester, M13 9PL, UK
| | - Laura Fumagalli
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.
- National Graphene Institute, University of Manchester, M13 9PL, UK
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2
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Duncan KM, Trousdale RC, Gonzales CN, Steel WH, Walker RA. l-Phenylalanine Partitioning Mechanisms in Model Biological Membranes. J Phys Chem B 2023. [PMID: 37315336 DOI: 10.1021/acs.jpcb.2c08582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Time-resolved fluorescence spectroscopy in combination with differential scanning calorimetry (DSC) was used to study the chemical interactions that occur when l-phenylalanine is introduced to solutions containing phosphatidylcholine vesicles. Studies reported in this work address open questions about l-Phe's affinity for lipid vesicle bilayers, the effects of l-Phe partitioning on bilayer properties, l-Phe's solvation within a lipid bilayer, and the amount of l-Phe within that local solvation environment. DSC data show that l-Phe reduces the amount of heat necessary to melt saturated phosphatidylcholine bilayers from their gel to liquid-crystalline state but does not change the transition temperature (Tgel-lc). Time-resolved emission shows only a single l-Phe lifetime at low temperatures corresponding to l-Phe remaining solvated in aqueous solution. At temperatures close to Tgel-lc, a second, shorter lifetime appears that is assigned to l-Phe already embedded within the membrane that becomes hydrated as water starts to permeate the lipid bilayer. This new lifetime is attributed to a conformationally restricted rotamer in the bilayer's polar headgroup region and accounts for up to 30% of the emission amplitude. Results reported for dipalmitoylphosphatidylcholine (DPPC, 16:0) lipid vesicles prove to be general, with similar effects observed for dimyristoylphosphatidylcholine (DMPC, 14:0) and distearoylphosphatidylcholine (DSPC, 18:0) vesicles. Taken together, these results create a complete and compelling picture of how l-Phe associates with model biological membranes. Furthermore, this approach to examining amino acid partitioning into membranes and the resulting solvation forces points to new strategies for studying the structure and chemistry of membrane-soluble peptides and selected membrane proteins.
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Affiliation(s)
- Katelyn M Duncan
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Rhys C Trousdale
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Cristina N Gonzales
- Department of Chemistry, Reed College, Portland, Oregon 97202, United States
| | - William H Steel
- Department of Chemistry, York College of Pennsylvania, York, Pennsylvania 17403, United States
| | - Robert A Walker
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
- Montana Materials Science Program, Montana State University, Bozeman, Montana 59717, United States
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3
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Chattopadhyay M, Krok E, Orlikowska-Rzeznik H, Piatkowski L. Cooperativity between sodium ions and water molecules facilitates lipid mobility in model cell membranes. Chem Sci 2023; 14:4002-4011. [PMID: 37063804 PMCID: PMC10094088 DOI: 10.1039/d2sc06836b] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 03/21/2023] [Indexed: 03/29/2023] Open
Abstract
Cellular membranes are surrounded by an aqueous buffer solution containing various ions, which influence the hydration layer of the lipid head groups. At the same time, water molecules hydrating the lipids play a major role in facilitating the organisation and dynamics of membrane lipids. Employing fluorescence microscopy imaging and fluorescence recovery after photobleaching measurements, we demonstrate that the cooperativity between water and sodium (Na+) ions is crucial to maintain lipid mobility upon the removal of the outer hydration layer of the lipid membrane. Under similar hydration conditions, lipid diffusion ceases in the absence of Na+ ions. We find that Na+ ions (and similarly K+ ions) strengthen the water clathrate cage around the lipid phosphocholine headgroup and thus prevent its breaking upon removal of bulk water. Intriguingly, Ca2+ and Mg2+ do not show this effect. In this article, we provide a detailed molecular-level picture of ion specific dependence of lipid mobility and membrane hydration properties.
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Affiliation(s)
| | - Emilia Krok
- Institute of Physics, Poznan University of Technology Piotrowo 3 60-965 Poznan Poland
| | | | - Lukasz Piatkowski
- Institute of Physics, Poznan University of Technology Piotrowo 3 60-965 Poznan Poland
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4
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Alavizargar A, Keller F, Wedlich-Söldner R, Heuer A. Effect of Cholesterol Versus Ergosterol on DPPC Bilayer Properties: Insights from Atomistic Simulations. J Phys Chem B 2021; 125:7679-7690. [PMID: 34255501 DOI: 10.1021/acs.jpcb.1c03528] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Sterols have been ascribed a major role in the organization of biological membranes, in particular for the formation of liquid ordered domains in complex lipid mixtures. Here, we employed molecular dynamics simulations to compare the effects of cholesterol and ergosterol as the major sterol of mammalian and fungal cells, respectively, on binary mixtures with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) as a proxy for saturated lipids. In agreement with previous work, we observe that the addition of sterol molecules modifies the order of DPPC both in the gel phase and in the liquid phase. When disentangling the overall tilt angle and the structure of the tail imposed by trans/gauche configurations of torsion angles in the tail, respectively, a more detailed picture of the impact of sterols can be formulated, revealing, for example, an approximate temperature-concentration superposition ranging from the liquid to the gel phase. Furthermore, a new quantitative measure to identify the presence of collective sterol effects is discussed. Moreover, when comparing both types of sterols, addition of cholesterol has a noticeably stronger impact on phospholipid properties than that of ergosterol. The observed differences can be attributed to higher planarity of the cholesterol ring system. This planarity combined with an inherent asymmetry in its molecular interactions leads to better alignment and hence stronger interaction with saturated acyl chains. Our results suggest that the high order demonstrated for ergosterol in fungal plasma membranes must therefore be generated via additional mechanisms.
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Affiliation(s)
- Azadeh Alavizargar
- Institute of Physical Chemistry, University of Muenster, Corrensstr. 28/30, 48149 Muenster, Germany
| | - Fabian Keller
- Institute of Physical Chemistry, University of Muenster, Corrensstr. 28/30, 48149 Muenster, Germany
| | - Roland Wedlich-Söldner
- Institute of Cell Dynamics and Imaging, Centre for Molecular Biology of Inflammation and Cells-in-Motion Cluster of Excellence, University of Muenster, 48149 Muenster, Germany
| | - Andreas Heuer
- Institute of Physical Chemistry, University of Muenster, Corrensstr. 28/30, 48149 Muenster, Germany
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5
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Mahmoudzadeh M, Magarkar A, Koivuniemi A, Róg T, Bunker A. Mechanistic Insight into How PEGylation Reduces the Efficacy of pH-Sensitive Liposomes from Molecular Dynamics Simulations. Mol Pharm 2021; 18:2612-2621. [PMID: 34096310 PMCID: PMC8289284 DOI: 10.1021/acs.molpharmaceut.1c00122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Liposome-based drug
delivery systems composed of DOPE stabilized
with cholesteryl hemisuccinate (CHMS) have been proposed as a drug
delivery mechanism with pH-triggered release as the anionic form (CHSa)
is protonated (CHS) at reduced pH; PEGylation is known to decrease
this pH sensitivity. In this manuscript, we set out to use molecular
dynamics (MD) simulations with a model with all-atom resolution to
provide insight into why incorporation of poly(ethyleneglycol) (PEG)
into DOPE–CHMS liposomes reduces their pH sensitivity; we also
address two additional questions: (1) How CHSa stabilizes DOPE bilayers
into a lamellar conformation at a physiological pH of 7.4? and (2)
how the change from CHSa to CHS at acidic pH triggers the destabilization
of DOPE bilayers? We found that (A) CHSa stabilizes the DOPE lipid
membrane by increasing the hydrophilicity of the bilayer surface,
(B) when CHSa changes to CHS by pH reduction, DOPE bilayers are destabilized
due to a reduction in bilayer hydrophilicity and a reduction in the
area per lipid, and (C) PEG stabilizes DOPE bilayers into the lamellar
phase, thus reducing the pH sensitivity of the liposomes by increasing
the area per lipid through penetration into the bilayer, which is
our main focus.
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Affiliation(s)
- Mohammad Mahmoudzadeh
- Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, 00100 Helsinki, Finland
| | - Aniket Magarkar
- Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, D-88397 Biberach a.d. Riss, Germany
| | - Artturi Koivuniemi
- Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, 00100 Helsinki, Finland
| | - Tomasz Róg
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Viikinkaarie 5 E, FI-00014 Helsinki, Finland
| | - Alex Bunker
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Viikinkaarie 5 E, FI-00014 Helsinki, Finland
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6
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Complexity of seemingly simple lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183420. [DOI: 10.1016/j.bbamem.2020.183420] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/26/2020] [Accepted: 07/07/2020] [Indexed: 12/15/2022]
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7
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Szczelina R, Baczynski K, Markiewicz M, Pasenkiewicz-Gierula M. Network of lipid interconnections at the interfaces of galactolipid and phospholipid bilayers. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2019.112002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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8
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Zhang B, Wang F, Zhou H, Gao D, Yuan Z, Wu C, Zhang X. Polymer Dots Compartmentalized in Liposomes as a Photocatalyst for In Situ Hydrogen Therapy. Angew Chem Int Ed Engl 2019; 58:2744-2748. [DOI: 10.1002/anie.201813066] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Boyu Zhang
- Faculty of Health SciencesUniversity of Macau Macau SAR China
- College of Medical LaboratoryDalian Medical University Dalian Liaoning 116044 China
| | - Fei Wang
- Department of Biomedical EngineeringSouthern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Hua Zhou
- Faculty of Health SciencesUniversity of Macau Macau SAR China
| | - Duyang Gao
- Paul C. Lauterbur Research Center for Biomedical ImagingInstitute of Biomedical and Health EngineeringShenzhen Institute of Advanced TechnologyChinese Academy of Science Shenzhen 518055 China
| | - Zhen Yuan
- Faculty of Health SciencesUniversity of Macau Macau SAR China
| | - Changfeng Wu
- Department of Biomedical EngineeringSouthern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Xuanjun Zhang
- Faculty of Health SciencesUniversity of Macau Macau SAR China
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9
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Zhang B, Wang F, Zhou H, Gao D, Yuan Z, Wu C, Zhang X. Polymer Dots Compartmentalized in Liposomes as a Photocatalyst for In Situ Hydrogen Therapy. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813066] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Boyu Zhang
- Faculty of Health SciencesUniversity of Macau Macau SAR China
- College of Medical LaboratoryDalian Medical University Dalian Liaoning 116044 China
| | - Fei Wang
- Department of Biomedical EngineeringSouthern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Hua Zhou
- Faculty of Health SciencesUniversity of Macau Macau SAR China
| | - Duyang Gao
- Paul C. Lauterbur Research Center for Biomedical ImagingInstitute of Biomedical and Health EngineeringShenzhen Institute of Advanced TechnologyChinese Academy of Science Shenzhen 518055 China
| | - Zhen Yuan
- Faculty of Health SciencesUniversity of Macau Macau SAR China
| | - Changfeng Wu
- Department of Biomedical EngineeringSouthern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Xuanjun Zhang
- Faculty of Health SciencesUniversity of Macau Macau SAR China
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10
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Rezaei Sani SM, Akhavan M, Jalili S. Salt-induced effects on natural and inverse DPPC lipid membranes: Molecular dynamics simulation. Biophys Chem 2018; 239:7-15. [DOI: 10.1016/j.bpc.2018.04.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/22/2018] [Accepted: 04/22/2018] [Indexed: 11/29/2022]
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11
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Stereospecific Interactions of Cholesterol in a Model Cell Membrane: Implications for the Membrane Dipole Potential. J Membr Biol 2018; 251:507-519. [DOI: 10.1007/s00232-018-0016-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 01/25/2018] [Indexed: 12/11/2022]
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12
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Bakarić D, Petrov D, Mouvenchery YK, Heiβler S, Oostenbrink C, Schaumann GE. Ion-induced modification of the sucrose network and its impact on melting of freeze-dried liposomes. DSC and molecular dynamics study. Chem Phys Lipids 2017; 210:38-46. [PMID: 29179944 DOI: 10.1016/j.chemphyslip.2017.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/14/2017] [Accepted: 11/23/2017] [Indexed: 02/07/2023]
Abstract
Disaccharides play an important role in survival of anhydrobiotic organisms during extreme environmental conditions. A key protection feature is their capability to form the hydrogen bond (HB) network in a similar fashion as the one made by water. Since various ions also affect the HB network in completely hydrated systems, it is of a great interest to understand how they impact preservation when incorporated in a disaccharide network. To address this, we employ a combination of experimental and modeling techniques to study behavior of multilamellar 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes freeze-dried with sucrose in presence of NaCl or NaH2PO4·H2O at various concentrations (0.01-1M). Differential scanning calorimetry (DSC) was employed in order to determine the cooperative unit size (CUS), the number of lipid molecules that constitute a domain of cooperative motion in the liposome, and the melting temperature (Tm). In the absence of salt CUS was estimated to be 122±12, whereas in the presence of NaCl CUS increases more (347±34 for c=1M) than for NaH2PO4·H2O (193±26 for 1M). When it comes to Tm, the situation is reversed; NaCl induces increase by about 1K, while NaH2PO4·H2O by about 10K. These findings clearly demonstrate how different interaction forces-hydrogen bonding, charge pairing, and van der Waals interactions between acyl chains-affect CUS and Tm. Their interplay and contribution of particular interaction was further analyzed with molecular dynamics (MD) simulations. This analysis demonstrated that the HB network of DMPC and sucrose is partially disrupted in the presence of NaCl ions, and even to a greater extent in the case of NaH2PO4·H2O ions. Notably, H2PO4- ions outcompete and replace the sucrose molecules at the DMPC surface, which in turn alters the nature of the DMPC-surrounding interactions, from a weaker HB-dominated to a stronger CP-dominated interaction network.
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Affiliation(s)
- Danijela Bakarić
- University of Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstraße 7, D-76829 Landau, Germany.
| | - Dražen Petrov
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna, Muthgasse 18, A-1190 Vienna, Austria
| | - Yamuna Kunhi Mouvenchery
- University of Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstraße 7, D-76829 Landau, Germany
| | - Stefan Heiβler
- Institute for Functional Interfaces, Karlsruhe Institute for Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Chris Oostenbrink
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna, Muthgasse 18, A-1190 Vienna, Austria
| | - Gabriele E Schaumann
- University of Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstraße 7, D-76829 Landau, Germany.
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13
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Smistad G, Nyström B, Zhu K, Grønvold MK, Røv-Johnsen A, Hiorth M. Liposomes coated with hydrophobically modified hydroxyethyl cellulose: Influence of hydrophobic chain length and degree of modification. Colloids Surf B Biointerfaces 2017; 156:79-86. [DOI: 10.1016/j.colsurfb.2017.04.061] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/29/2017] [Accepted: 04/29/2017] [Indexed: 12/20/2022]
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14
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Hartkamp R, Moore TC, Iacovella CR, Thompson MA, Bulsara PA, Moore DJ, McCabe C. Investigating the Structure of Multicomponent Gel-Phase Lipid Bilayers. Biophys J 2017; 111:813-823. [PMID: 27558724 DOI: 10.1016/j.bpj.2016.07.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 07/07/2016] [Accepted: 07/11/2016] [Indexed: 11/30/2022] Open
Abstract
Single- and multicomponent lipid bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC), isostearyl isostearate, and heptadecanoyl heptadecanoate in the gel phase are studied via molecular dynamics simulations. It is shown that the structural properties of multicomponent bilayers can deviate strongly from the structures of their single-component counterparts. Specifically, the lipid mixtures are shown to adopt a compact packing by offsetting the positioning depths at which different lipid species are located in the bilayer. This packing mechanism affects the area per lipid, the bilayer height, and the chain tilt angles and has important consequences for other bilayer properties, such as interfacial hydrogen bonding and bilayer permeability. In particular, the simulations suggest that bilayers containing isostearyl isostearate or heptadecanoyl heptadecanoate are less permeable than pure 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine or DSPC bilayers. Furthermore, hydrogen-bond analysis shows that the residence times of lipid-water hydrogen bonds depend strongly on the bilayer composition, with longer residence times for bilayers that have a higher DSPC content. The findings illustrate and explain the fundamental differences between the properties of single- and multicomponent bilayers.
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Affiliation(s)
- Remco Hartkamp
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee; Multiscale Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee
| | - Timothy C Moore
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee; Multiscale Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee
| | - Christopher R Iacovella
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee; Multiscale Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee
| | | | | | - David J Moore
- GlaxoSmithKline Consumer Healthcare, Warren, New Jersey
| | - Clare McCabe
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee; Multiscale Modeling and Simulation (MuMS) Center, Vanderbilt University, Nashville, Tennessee; Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
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15
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Mokkila S, Postila PA, Rissanen S, Juhola H, Vattulainen I, Róg T. Calcium Assists Dopamine Release by Preventing Aggregation on the Inner Leaflet of Presynaptic Vesicles. ACS Chem Neurosci 2017; 8:1242-1250. [PMID: 28165217 DOI: 10.1021/acschemneuro.6b00395] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In this study, the dopamine-lipid bilayer interactions were probed with three physiologically relevant ion compositions using atomistic molecular dynamics simulations and free energy calculations. The in silico results indicate that calcium is able to decrease significantly the binding of dopamine to a neutral (zwitterionic) phosphatidylcholine lipid bilayer model mimicking the inner leaflet of a presynaptic vesicle. We argue that the observed calcium-induced effect is likely in crucial role in the neurotransmitter release from the presynaptic vesicles docked in the active zone of nerve terminals. The inner leaflets of presynaptic vesicles, which are responsible for releasing neurotransmitters into the synaptic cleft, are mainly composed of neutral lipids such as phosphatidylcholine and phosphatidylethanolamine. The neutrality of the lipid head group region, enhanced by a low pH level, should limit membrane aggregation of transmitters. In addition, the simulations suggest that the high calcium levels inside presynaptic vesicles prevent even the most lipophilic transmitters such as dopamine from adhering to the inner leaflet surface, thus rendering unhindered neurotransmitter release feasible.
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Affiliation(s)
- Sini Mokkila
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Pekka A. Postila
- Structural Bioinformatics Laboratory, Biochemistry,
Faculty of Science and Engineering, Åbo Akademi University, 20500 Turku, Finland
| | - Sami Rissanen
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Hanna Juhola
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
- MEMPHYS − Center for Biomembrane
Physics, University of Southern Denmark, 5230 Odense, Denmark
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
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16
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Magarkar A, Róg T, Bunker A. A computational study suggests that replacing PEG with PMOZ may increase exposure of hydrophobic targeting moiety. Eur J Pharm Sci 2017; 103:128-135. [PMID: 28285174 DOI: 10.1016/j.ejps.2017.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 02/28/2017] [Accepted: 03/07/2017] [Indexed: 12/18/2022]
Abstract
In a previous study we showed that the cause of failure of a new, proposed, targeting ligand, the AETP moiety, when attached to a PEGylated liposome, was occlusion by the poly(ethylene glycol) (PEG) layer due to its hydrophobic nature, given that PEG is not entirely hydrophilic. At the time we proposed that possible replacement with a more hydrophilic protective polymer could alleviate this problem. In this study we have used computational molecular dynamics modelling, using a model with all atom resolution, to suggest that a specific alternative protective polymer, poly(2-methyloxazoline) (PMOZ), would perform exactly this function. Our results show that when PEG is replaced by PMOZ the relative exposure to the solvent of AETP is increased to a level even greater than that we found in previous simulations for the RGD peptide, a targeting moiety that has previously been used successfully in PEGylated liposome based therapies. While the AETP moiety itself is no longer under consideration, the results of this computational study have broader significance: the use of PMOZ as an alternative polymer coating to PEG could be efficacious in the context of more hydrophobic targeting ligands. In addition to PMOZ we studied another polyoxazoline, poly(2-ethyloxazoline) (PEOZ), that has also been mooted as a possible alternate protective polymer. It was also found that the RDG peptide occlusion was significantly greater for the case of both oxazolines as opposed to PEG and that, unlike PEG, neither oxazoline entered the membrane. As far as we are aware this is the first time that polyoxazolines have been studied using molecular dynamics simulation with all atom resolution.
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Affiliation(s)
- Aniket Magarkar
- Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland; Institute of Organic Chemistry and Biochemistry, Academy of the Sciences of the Czech Republic Prague, Czech Republic
| | - Tomasz Róg
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Alex Bunker
- Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland.
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17
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Gonzalez MA, Barriga HMG, Richens JL, Law RV, O'Shea P, Bresme F. How does ytterbium chloride interact with DMPC bilayers? A computational and experimental study. Phys Chem Chem Phys 2017; 19:9199-9209. [DOI: 10.1039/c7cp01400g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Lanthanide salts have been studied for many years, primarily in Nuclear Magnetic Resonance (NMR) experiments of mixed lipid–protein systems and more recently to study lipid flip-flop in model membrane systems.
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Affiliation(s)
| | | | | | - Robert V. Law
- Department of Chemistry
- Imperial College London
- London
- UK
| | - Paul O'Shea
- Department of Chemistry
- Imperial College London
- London
- UK
- School of Life Sciences
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18
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Jay AG, Hamilton JA. Disorder Amidst Membrane Order: Standardizing Laurdan Generalized Polarization and Membrane Fluidity Terms. J Fluoresc 2016; 27:243-249. [DOI: 10.1007/s10895-016-1951-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 10/03/2016] [Indexed: 12/01/2022]
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19
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Bunker A, Magarkar A, Viitala T. Rational design of liposomal drug delivery systems, a review: Combined experimental and computational studies of lipid membranes, liposomes and their PEGylation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2334-2352. [DOI: 10.1016/j.bbamem.2016.02.025] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 01/22/2023]
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20
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Alarcón LM, de Los Angeles Frías M, Morini MA, Belén Sierra M, Appignanesi GA, Anibal Disalvo E. Water populations in restricted environments of lipid membrane interphases. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:94. [PMID: 27761781 DOI: 10.1140/epje/i2016-16094-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 09/20/2016] [Indexed: 06/06/2023]
Abstract
We employ molecular dynamics simulations to study the hydration properties of Dipalmitoylphosphatidylcholine (DPPC) bilayers, both in the gel and the liquid crystalline states. We show that while the tight hydration centers (PO and CO moieties) are significantly hydrated in both phases, the gel-fluid transition involves significant changes at the second hydration shell, particularly at the buried region between the hydrocarbon tails. Thus, while almost no buried water population exists in the gel state below the carbonyls, this hydrophobic region becomes partially water accesible in the liquid crystalline state. We shall also show that such water molecules present a lower H-bond coordination as compared to the molecules at the primary hydration shell. This means that, while the latter are arranged in relatively compact nanoclusters (as already proposed), the buried water molecules tend to organize themselves in less compact structures, typically strings or branched strings, with a scarce population of isolated molecules. This behavior is similar to that observed in other hydration contexts, like water penetrating carbon nanotubes or model hydrophobic channels or pores, and reflects the reluctance of water to sacrifice HB coordination.
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Affiliation(s)
- Laureano M Alarcón
- Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina
| | - M de Los Angeles Frías
- Laboratorio de Biointerfases y Sistemas Biomiméticos, Laboratorios Centrales, CITSE-UNSE, Santiago del Estero, Argentina
| | - Marcela A Morini
- Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina
| | - M Belén Sierra
- Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina
| | - Gustavo A Appignanesi
- Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina.
| | - E Anibal Disalvo
- Laboratorio de Biointerfases y Sistemas Biomiméticos, Laboratorios Centrales, CITSE-UNSE, Santiago del Estero, Argentina
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21
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Nie GX, Huang JY, Huang JP. Melting–Freezing Transition of Monolayer Water Confined by Phosphorene Plates. J Phys Chem B 2016; 120:9011-8. [DOI: 10.1021/acs.jpcb.6b02473] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- G. X. Nie
- Department
of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - J. Y. Huang
- Department
of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - J. P. Huang
- Department
of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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22
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Róg T, Orłowski A, Llorente A, Skotland T, Sylvänne T, Kauhanen D, Ekroos K, Sandvig K, Vattulainen I. Interdigitation of long-chain sphingomyelin induces coupling of membrane leaflets in a cholesterol dependent manner. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:281-8. [DOI: 10.1016/j.bbamem.2015.12.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 11/16/2015] [Accepted: 12/01/2015] [Indexed: 12/15/2022]
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23
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Pasenkiewicz-Gierula M, Baczynski K, Markiewicz M, Murzyn K. Computer modelling studies of the bilayer/water interface. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2305-2321. [PMID: 26825705 DOI: 10.1016/j.bbamem.2016.01.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/18/2016] [Accepted: 01/21/2016] [Indexed: 01/24/2023]
Abstract
This review summarises high resolution studies on the interface of lamellar lipid bilayers composed of the most typical lipid molecules which constitute the lipid matrix of biomembranes. The presented results were obtained predominantly by computer modelling methods. Whenever possible, the results were compared with experimental results obtained for similar systems. The first and main section of the review is concerned with the bilayer-water interface and is divided into four subsections. The first describes the simplest case, where the interface consists only of lipid head groups and water molecules and focuses on interactions between the lipid heads and water molecules; the second describes the interface containing also mono- and divalent ions and concentrates on lipid-ion interactions; the third describes direct inter-lipid interactions. These three subsections are followed by a discussion on the network of direct and indirect inter-lipid interactions at the bilayer interface. The second section summarises recent computer simulation studies on the interactions of antibacterial membrane active compounds with various models of the bacterial outer membrane. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
| | - Krzysztof Baczynski
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Michal Markiewicz
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Krzysztof Murzyn
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
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24
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Boţan A, Joly L, Fillot N, Loison C. Mixed Mechanism of Lubrication by Lipid Bilayer Stacks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12197-12202. [PMID: 26381720 DOI: 10.1021/acs.langmuir.5b02786] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Although the key role of lipid bilayer stacks in biological lubrication is generally accepted, the mechanisms underlying their extreme efficiency remain elusive. In this article, we report molecular dynamics simulations of lipid bilayer stacks undergoing load and shear. When the hydration level is reduced, the velocity accommodation mechanism changes from viscous shear in hydration water to interlayer sliding in the bilayers. This enables stacks of hydrated lipid bilayers to act as efficient boundary lubricants for various hydration conditions, structures, and mechanical loads. We also propose an estimation for the friction coefficient; thanks to the strong hydration forces between lipid bilayers, the high local viscosity is not in contradiction with low friction coefficients.
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Affiliation(s)
- Alexandru Boţan
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Laurent Joly
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Nicolas Fillot
- LaMCoS, UMR5259 INSA-Lyon-CNRS, Université de Lyon , 69622 Villeurbanne, France
| | - Claire Loison
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon , 69622 Villeurbanne, France
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25
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Kwolek U, Kulig W, Wydro P, Nowakowska M, Róg T, Kepczynski M. Effect of Phosphatidic Acid on Biomembrane: Experimental and Molecular Dynamics Simulations Study. J Phys Chem B 2015; 119:10042-51. [DOI: 10.1021/acs.jpcb.5b03604] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Urszula Kwolek
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Waldemar Kulig
- Department
of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Paweł Wydro
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Maria Nowakowska
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Tomasz Róg
- Department
of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Mariusz Kepczynski
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
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26
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Murzyn K, Pasenkiewicz-Gierula M. Structural Properties of the Water/Membrane Interface of a Bilayer Built of the E. coli Lipid A. J Phys Chem B 2015; 119:5846-56. [DOI: 10.1021/jp5119629] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Krzysztof Murzyn
- Department
of Computational
Biophysics and Bioinformatics, Faculty of Biochemistry,
Biophysics, and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Marta Pasenkiewicz-Gierula
- Department
of Computational
Biophysics and Bioinformatics, Faculty of Biochemistry,
Biophysics, and Biotechnology, Jagiellonian University, Kraków, Poland
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27
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Abstract
It is commonly assumed that the structure of water at a lipid-water interface is influenced mostly in the first hydration layer. However, recent results from different experimental methods show that perturbation extends through several hydration layers. Due to its low light penetration depth, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is specifically suited to study interlamellar water structure in multibilayers. Results obtained by this technique confirm the long-range water structure disturbance. Consequently, in confined membrane environments nearly all water molecules can be perturbed. It is important to note that the behavior of confined water molecules differs significantly in samples prepared in excess water and in partially hydrated samples. We show in what manner the interlamellar water perturbation is influenced by the hydration level and how it is sequentially modified with a step-by-step dehydration of samples either by water evaporation or by osmotic pressure. Our results also indicate that besides different levels of hydration the lipid-water interaction is modulated by different lipid headgroups and different lipid phases as well. Therefore, modification of interlamellar water properties may clarify the role of water-mediated effects in biological processes.
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Affiliation(s)
- Zoran Arsov
- Laboratory of Biophysics, Department of Solid State Physics, "Jozef Stefan" Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
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28
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Vierros S, Sammalkorpi M. Role of hydration in phosphatidylcholine reverse micelle structure and gelation in cyclohexane: a molecular dynamics study. Phys Chem Chem Phys 2015; 17:14951-60. [DOI: 10.1039/c5cp01799h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Molecular simulations reveal lipid headgroup hydration is at key role in organogel transition in lecithin–water–cyclohexane systems.
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Affiliation(s)
- S. Vierros
- Department of Chemistry
- Aalto University
- 00076 Aalto
- Finland
| | - M. Sammalkorpi
- Department of Chemistry
- Aalto University
- 00076 Aalto
- Finland
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29
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Ogata K, Uchida W, Nakamura S. Understanding Thermal Phases in Atomic Detail by All-Atom Molecular-Dynamics Simulation of a Phospholipid Bilayer. J Phys Chem B 2014; 118:14353-65. [DOI: 10.1021/jp504684h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Koji Ogata
- Nakamura
Laboratory, RIKEN Innovation Center, 2-1 Hirosa-wa, Wako, Saitama, Japan 351-0198
| | - Waka Uchida
- Nakamura
Laboratory, RIKEN Innovation Center, 2-1 Hirosa-wa, Wako, Saitama, Japan 351-0198
- Department
of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa Japan, 226-8503
| | - Shinichiro Nakamura
- Nakamura
Laboratory, RIKEN Innovation Center, 2-1 Hirosa-wa, Wako, Saitama, Japan 351-0198
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30
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Róg T, Vattulainen I. Cholesterol, sphingolipids, and glycolipids: what do we know about their role in raft-like membranes? Chem Phys Lipids 2014; 184:82-104. [PMID: 25444976 DOI: 10.1016/j.chemphyslip.2014.10.004] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Revised: 10/24/2014] [Accepted: 10/25/2014] [Indexed: 12/14/2022]
Abstract
Lipids rafts are considered to be functional nanoscale membrane domains enriched in cholesterol and sphingolipids, characteristic in particular of the external leaflet of cell membranes. Lipids, together with membrane-associated proteins, are therefore considered to form nanoscale units with potential specific functions. Although the understanding of the structure of rafts in living cells is quite limited, the possible functions of rafts are widely discussed in the literature, highlighting their importance in cellular functions. In this review, we discuss the understanding of rafts that has emerged based on recent atomistic and coarse-grained molecular dynamics simulation studies on the key lipid raft components, which include cholesterol, sphingolipids, glycolipids, and the proteins interacting with these classes of lipids. The simulation results are compared to experiments when possible.
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Affiliation(s)
- Tomasz Róg
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, Tampere, Finland; MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
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31
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. III. Water clustering and vibrational energy transfer. J Chem Phys 2014; 139:175103. [PMID: 24206336 DOI: 10.1063/1.4827018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Water clustering and connectivity around lipid bilayers strongly influences the properties of membranes and is important for functions such as proton and ion transport. Vibrational anisotropic pump-probe spectroscopy is a powerful tool for understanding such clustering, as the measured anisotropy depends upon the time-scale and degree of intra- and intermolecular vibrational energy transfer. In this article, we use molecular dynamics simulations and theoretical vibrational spectroscopy to help interpret recent experimental measurements of the anisotropy of water in lipid multi-bilayers as a function of both lipid hydration level and isotopic substitution. Our calculations are in satisfactory agreement with the experiments of Piatkowski, Heij, and Bakker, and from our simulations we can directly probe water clustering and connectivity. We find that at low hydration levels, many water molecules are in fact isolated, although up to 70% of hydration water forms small water clusters or chains. At intermediate hydration levels, water forms a wide range of cluster sizes, while at higher hydration levels, the majority of water molecules are part of a large, percolating water cluster. Therefore, the size, number, and nature of water clusters are strongly dependent on lipid hydration level, and the measured anisotropy reflects this through its dependence on intermolecular energy transfer.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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32
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Magarkar A, Dhawan V, Kallinteri P, Viitala T, Elmowafy M, Róg T, Bunker A. Cholesterol level affects surface charge of lipid membranes in saline solution. Sci Rep 2014; 4:5005. [PMID: 24845659 PMCID: PMC4028897 DOI: 10.1038/srep05005] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 05/01/2014] [Indexed: 12/19/2022] Open
Abstract
Cholesterol is an important component of all biological membranes as well as drug delivery liposomes. We show here that increasing the level of cholesterol in a phospholipid membrane decreases surface charge in the physiological environment. Through molecular dynamics simulation we have shown that increasing the level of cholesterol decreases Na+ ion binding. Complementary experimental ζ--potential measurements have shown a decreased ζ--potential with increasing cholesterol content, indicative of reduced surface charge. Both experiments and simulations have been carried out on both saturated 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and monounsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. This result is particularly important because membrane surface charge plays an important role in the interactions of biomembranes with peripheral membrane proteins and drug delivery liposomes with the immune system.
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Affiliation(s)
- Aniket Magarkar
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Vivek Dhawan
- Bombay College of Pharmacy, University of Mumbai, Mumbai, India
| | - Paraskevi Kallinteri
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Tapani Viitala
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Mohammed Elmowafy
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Alex Bunker
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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33
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Khandelia H, Loubet B, Olzyńska A, Jurkiewicz P, Hof M. Pairing of cholesterol with oxidized phospholipid species in lipid bilayers. SOFT MATTER 2014; 10:639-647. [PMID: 24795978 DOI: 10.1039/c3sm52310a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We claim that (1) cholesterol protects bilayers from disruption caused by lipid oxidation by sequestering conical shaped oxidized lipid species such as 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PZPC) away from phospholipid, because cholesterol and the oxidized lipid have complementary shapes and (2) mixtures of cholesterol and oxidized lipids can self-assemble into bilayers much like lysolipid–cholesterol mixtures. The evidence for bilayer protection comes from molecular dynamics (MD) simulations and dynamic light scattering (DLS) measurements. Unimodal size distributions of extruded vesicles (LUVETs) made up of a mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and PZPC containing high amounts of PZPC are only obtained when cholesterol is present in high concentrations. In simulations, bilayers containing high amounts of PZPC become porous, unless cholesterol is also present. The protective effect of cholesterol on oxidized lipids has been observed previously using electron paramagnetic resonance (EPR) and electron microscopy imaging of vesicles. The evidence for the pairing of cholesterol and PZPC comes mainly from correlated 2-D density and thickness plots from simulations, which show that these two molecules co-localize in bilayers. Further evidence that the two molecules can cohabitate comes from self-assembly simulations, where we show that cholesterol-oxidized lipid mixtures can form lamellar phases at specific concentrations, reminiscent of lysolipid–cholesterol mixtures. The additivity of the packing parameters of cholesterol and PZPC explains their cohabitation in a planar bilayer. Oxidized lipids are ubiquitously present in significant amounts in high- and low-density lipoprotein (HDL and LDL) particles, diseased tissues, and in model phospholipid mixtures containing polyunsaturated lipids. Therefore, our hypothesis has important consequences for cellular cholesterol trafficking; diseases related to oxidized lipids, and to biophysical studies of phase behaviour of cholesterol-containing phospholipid mixtures.
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34
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Rissanen S, Kumorek M, Martinez-Seara H, Li YC, Jamróz D, Bunker A, Nowakowska M, Vattulainen I, Kepczynski M, Róg T. Effect of PEGylation on Drug Entry into Lipid Bilayer. J Phys Chem B 2013; 118:144-51. [DOI: 10.1021/jp4105745] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sami Rissanen
- Department
of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland
| | - Marta Kumorek
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Hector Martinez-Seara
- Department
of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland
| | - Yen-Chin Li
- Centre
for Drug Research, Faculty of Pharmacy, University of Helsinki, FI-00014 Helsinki, Finland
| | - Dorota Jamróz
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Alex Bunker
- Centre
for Drug Research, Faculty of Pharmacy, University of Helsinki, FI-00014 Helsinki, Finland
| | - Maria Nowakowska
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Ilpo Vattulainen
- Department
of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland
- MEMPHYS—Center
for Biomembrane Physics, University of Southern Denmark, DK-5230 Odense, Denmark
| | - Mariusz Kepczynski
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Tomasz Róg
- Department
of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland
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35
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Bacalum M, Zorilă B, Radu M. Fluorescence spectra decomposition by asymmetric functions: Laurdan spectrum revisited. Anal Biochem 2013; 440:123-9. [DOI: 10.1016/j.ab.2013.05.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/17/2013] [Accepted: 05/22/2013] [Indexed: 10/26/2022]
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36
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Qiao BF, Olvera de la Cruz M. Driving Force for Crystallization of Anionic Lipid Membranes Revealed by Atomistic Simulations. J Phys Chem B 2013; 117:5073-80. [DOI: 10.1021/jp401767c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bao Fu Qiao
- Department
of Materials Science and Engineering, and ‡Department of Chemistry, Northwestern University, Evanston, Illinois
60208, United States
| | - Monica Olvera de la Cruz
- Department
of Materials Science and Engineering, and ‡Department of Chemistry, Northwestern University, Evanston, Illinois
60208, United States
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37
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Tsai HHG, Lai WX, Lin HD, Lee JB, Juang WF, Tseng WH. Molecular dynamics simulation of cation–phospholipid clustering in phospholipid bilayers: Possible role in stalk formation during membrane fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2742-55. [DOI: 10.1016/j.bbamem.2012.05.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 05/11/2012] [Accepted: 05/29/2012] [Indexed: 10/28/2022]
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38
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Orłowski A, Grzybek M, Bunker A, Pasenkiewicz-Gierula M, Vattulainen I, Männistö PT, Róg T. Strong preferences of dopamine and l-dopa towards lipid head group: importance of lipid composition and implication for neurotransmitter metabolism. J Neurochem 2012; 122:681-90. [DOI: 10.1111/j.1471-4159.2012.07813.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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39
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Li YC, Rissanen S, Stepniewski M, Cramariuc O, Róg T, Mirza S, Xhaard H, Wytrwal M, Kepczynski M, Bunker A. Study of Interaction Between PEG Carrier and Three Relevant Drug Molecules: Piroxicam, Paclitaxel, and Hematoporphyrin. J Phys Chem B 2012; 116:7334-41. [DOI: 10.1021/jp300301z] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yen-Chin Li
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Sami Rissanen
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Michał Stepniewski
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Oana Cramariuc
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Sabir Mirza
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Henri Xhaard
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | | | | | - Alex Bunker
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
- Department of Chemistry, Aalto University, Espoo, Finland
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40
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Lehtinen J, Magarkar A, Stepniewski M, Hakola S, Bergman M, Róg T, Yliperttula M, Urtti A, Bunker A. Analysis of cause of failure of new targeting peptide in PEGylated liposome: Molecular modeling as rational design tool for nanomedicine. Eur J Pharm Sci 2012; 46:121-30. [DOI: 10.1016/j.ejps.2012.02.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 02/02/2012] [Accepted: 02/12/2012] [Indexed: 10/28/2022]
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41
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Stępniewski M, Kepczynski M, Jamróz D, Nowakowska M, Rissanen S, Vattulainen I, Róg T. Interaction of Hematoporphyrin with Lipid Membranes. J Phys Chem B 2012; 116:4889-97. [DOI: 10.1021/jp300899b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Michał Stępniewski
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków,
Poland
| | - Mariusz Kepczynski
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków,
Poland
| | - Dorota Jamróz
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków,
Poland
| | - Maria Nowakowska
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków,
Poland
| | - Sami Rissanen
- Department of Physics, Tampere University of Technology, PO Box 692, FI-33101
Tampere, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, PO Box 692, FI-33101
Tampere, Finland
- MEMPHYS-Center
for Biomembrane
Physics, University of Southern Denmark, Odense, Denmark
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, PO Box 692, FI-33101
Tampere, Finland
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42
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Magarkar A, Karakas E, Stepniewski M, Róg T, Bunker A. Molecular Dynamics Simulation of PEGylated Bilayer Interacting with Salt Ions: A Model of the Liposome Surface in the Bloodstream. J Phys Chem B 2012; 116:4212-9. [DOI: 10.1021/jp300184z] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Aniket Magarkar
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Esra Karakas
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Michał Stepniewski
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Alex Bunker
- Centre for Drug Research,
Faculty
of Pharmacy, University of Helsinki, Helsinki,
Finland
- Department of Chemistry, Aalto University, Espoo, Finland
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43
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St-Pierre JF, Bunker A, Róg T, Karttunen M, Mousseau N. Molecular dynamics simulations of the bacterial ABC transporter SAV1866 in the closed form. J Phys Chem B 2012; 116:2934-42. [PMID: 22339391 DOI: 10.1021/jp209126c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ATP binding cassette (ABC) transporter family of proteins contains members involved in ATP-mediated import or export of ligands at the cell membrane. For the case of exporters, the translocation mechanism involves a large-scale conformational change that involves a clothespin-like motion from an inward-facing open state, able to bind ligands and adenosine triphosphate (ATP), to an outward-facing closed state. Our work focuses on SAV1866, a bacterial member of the ABC transporter family for which the structure is known for the closed state. To evaluate the ability of this protein to undergo conformational changes at physiological temperature, we first performed conventional molecular dynamics (MD) on the cocrystallized adenosine diphosphate (ADP)-bound structure and on a nucleotide-free structure. With this assessment of SAV1866's stability, conformational changes were induced by steered molecular dynamics (SMD), in which the nucleotide binding domains (NBD) were pushed apart, simulating the ATP hydrolysis energy expenditure. We found that the transmembrane domain is not easily perturbed by large-scale motions of the NBDs.
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Affiliation(s)
- Jean-François St-Pierre
- Département de Physique and Regroupement Québécois sur les Matériaux de Pointe, Université de Montréal, C.P. 6128, succursale centre-ville, Montréal (Québec), Canada H3C 3J7
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44
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Gruenbaum SM, Pieniazek PA, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. II. Two-dimensional infrared and peak shift observables within different theoretical approximations. J Chem Phys 2012; 135:164506. [PMID: 22047251 DOI: 10.1063/1.3655671] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In a previous report, we calculated the infrared absorption spectrum and both the isotropic and anisotropic pump-probe signals for the OD stretch of isotopically dilute water in dilauroylphosphatidylcholine (DLPC) multi-bilayers as a function of the lipid hydration level. These results were then compared to recent experimental measurements and are in generally good agreement. In this paper, we will further investigate the structure and dynamics of hydration water using molecular dynamics simulations and calculations of the two-dimensional infrared and vibrational echo peak shift observables for hydration water in DLPC membranes. These observables have not yet been measured experimentally, but future comparisons may provide insight into spectral diffusion processes and hydration water heterogeneity. We find that at low hydration levels the motion of water molecules inside the lipid membrane is significantly arrested, resulting in very slow spectral diffusion. At higher hydration levels, spectral diffusion is more rapid, but still slower than in bulk water. We also investigate the effects of several common approximations on the calculation of spectroscopic observables by computing these observables within multiple levels of theory. The impact of these approximations on the resulting spectra affects our interpretation of these measurements and reveals that, for example, the cumulant approximation, which may be valid for certain systems, is not a good approximation for a highly heterogeneous environment such as hydration water in lipid multi-bilayers.
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Affiliation(s)
- Scott M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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45
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Bunker A. Poly(Ethylene Glycol) in Drug Delivery, Why Does it Work, and Can We do Better? All Atom Molecular Dynamics Simulation Provides Some Answers. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.phpro.2012.05.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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46
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Orsi M, Essex JW. The ELBA force field for coarse-grain modeling of lipid membranes. PLoS One 2011; 6:e28637. [PMID: 22194874 PMCID: PMC3241685 DOI: 10.1371/journal.pone.0028637] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 11/11/2011] [Indexed: 02/05/2023] Open
Abstract
A new coarse-grain model for molecular dynamics simulation of lipid membranes is presented. Following a simple and conventional approach, lipid molecules are modeled by spherical sites, each representing a group of several atoms. In contrast to common coarse-grain methods, two original (interdependent) features are here adopted. First, the main electrostatics are modeled explicitly by charges and dipoles, which interact realistically through a relative dielectric constant of unity (ε(r) = 1). Second, water molecules are represented individually through a new parametrization of the simple Stockmayer potential for polar fluids; each water molecule is therefore described by a single spherical site embedded with a point dipole. The force field is shown to accurately reproduce the main physical properties of single-species phospholipid bilayers comprising dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE) in the liquid crystal phase, as well as distearoylphosphatidylcholine (DSPC) in the liquid crystal and gel phases. Insights are presented into fundamental properties and phenomena that can be difficult or impossible to study with alternative computational or experimental methods. For example, we investigate the internal pressure distribution, dipole potential, lipid diffusion, and spontaneous self-assembly. Simulations lasting up to 1.5 microseconds were conducted for systems of different sizes (128, 512 and 1058 lipids); this also allowed us to identify size-dependent artifacts that are expected to affect membrane simulations in general. Future extensions and applications are discussed, particularly in relation to the methodology's inherent multiscale capabilities.
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Affiliation(s)
- Mario Orsi
- School of Chemistry, University of Southampton, Southampton, United Kingdom.
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47
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Orłowski A, St-Pierre JF, Magarkar A, Bunker A, Pasenkiewicz-Gierula M, Vattulainen I, Róg T. Properties of the Membrane Binding Component of Catechol-O-methyltransferase Revealed by Atomistic Molecular Dynamics Simulations. J Phys Chem B 2011; 115:13541-50. [DOI: 10.1021/jp207177p] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Adam Orłowski
- Department of Computational Biophysics and Bioinformatics, Faculty of Biotechnology, Biochemistry and Biophysics, Jagiellonian University, Gronostajowa 7, Poland
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Jean-François St-Pierre
- Departement de Physique and Regroupement Quebecois sur les Materiaux de Pointe, Universite de Montreal, C.P. 6128, Succursale Centre-ville, Montreal (Quebec), Canada
| | - Aniket Magarkar
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014, University of Helsinki, Finland
| | - Alex Bunker
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014, University of Helsinki, Finland
- Department of Chemistry, Aalto University School of Science, P.O. Box 6100, FI-02015, AALTO, Espoo, Finland
| | - Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, Faculty of Biotechnology, Biochemistry and Biophysics, Jagiellonian University, Gronostajowa 7, Poland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
- Department of Applied Physics, Aalto University School of Science, Finland
- MEMPHYS−Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
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48
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Levinger NE, Costard R, Nibbering ETJ, Elsaesser T. Ultrafast energy migration pathways in self-assembled phospholipids interacting with confined water. J Phys Chem A 2011; 115:11952-9. [PMID: 21928826 DOI: 10.1021/jp206099a] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phospholipids self-assembled into reverse micelles in benzene are introduced as a new model system to study elementary processes relevant for energy transport in hydrated biological membranes. Femtosecond vibrational spectroscopy gives insight into the dynamics of the antisymmetric phosphate stretching vibration ν(AS)(PO(2))(-), a sensitive probe of local phosphate-water interactions and energy transport. The decay of the ν(AS)(PO(2))(-) mode with a 300-fs lifetime transfers excess energy to a subgroup of phospholipid low-frequency modes, followed by redistribution among phospholipid vibrations within a few picoseconds. The latter relaxation is accelerated by adding a confined water pool, an efficient heat sink in which the excess energy induces weakening or breaking of water-water and water-phospholipid hydrogen bonds. In parallel to vibrational relaxation, resonant energy transfer between ν(AS)(PO(2))(-) oscillators delocalizes the initial excitation.
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Affiliation(s)
- Nancy E Levinger
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany.
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49
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. I. Infrared spectra and ultrafast pump-probe observables. J Chem Phys 2011; 135:075101. [PMID: 21861584 PMCID: PMC3172989 DOI: 10.1063/1.3615717] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 07/02/2011] [Indexed: 11/15/2022] Open
Abstract
The vibrational spectroscopy of hydration water in dilauroylphosphatidylcholine lipid multi-bilayers is investigated using molecular dynamics simulations and a mixed quantum/classical model for the OD stretch spectroscopy of dilute HDO in H(2)O. FTIR absorption spectra, and isotropic and anisotropic pump-probe decay curves have been measured experimentally as a function of the hydration level of the lipid multi-bilayer, and our goal is to make connection with these experiments. To this end, we use third-order response functions, which allow us to include non-Gaussian frequency fluctuations, non-Condon effects, molecular rotations, and a fluctuating vibrational lifetime, all of which we believe are important for this system. We calculate the response functions using existing transition frequency and dipole maps. From the experiments it appears that there are two distinct vibrational lifetimes corresponding to HDO molecules in different molecular environments. In order to obtain these lifetimes, we consider a simple two-population model for hydration water hydrogen bonds. Assuming a different lifetime for each population, we then calculate the isotropic pump-probe decay, fitting to experiment to obtain the two lifetimes for each hydration level. With these lifetimes in hand, we then calculate FTIR spectra and pump-probe anisotropy decay as a function of hydration. This approach, therefore, permits a consistent calculation of all observables within a unified computational scheme. Our theoretical results are all in qualitative agreement with experiment. The vibrational lifetime of lipid-associated OD groups is found to be systematically shorter than that of the water-associated population, and the lifetimes of each population increase with decreasing hydration, in agreement with previous analysis. Our theoretical FTIR absorption spectra successfully reproduce the experimentally observed red-shift with decreasing lipid hydration, and we confirm a previous interpretation that this shift results from the hydrogen bonding of water to the lipid phosphate group. From the pump-probe anisotropy decay, we confirm that the reorientational motions of water molecules slow significantly as hydration decreases, with water bound in the lipid carbonyl region undergoing the slowest rotations.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave. University of Wisconsin, Madison, Wisconsin 53706, USA
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50
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Stepniewski M, Pasenkiewicz-Gierula M, Róg T, Danne R, Orlowski A, Karttunen M, Urtti A, Yliperttula M, Vuorimaa E, Bunker A. Study of PEGylated lipid layers as a model for PEGylated liposome surfaces: molecular dynamics simulation and Langmuir monolayer studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7788-7798. [PMID: 21604684 DOI: 10.1021/la200003n] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have combined Langmuir monolayer film experiments and all-atom molecular dynamics (MD) simulation of a bilayer to study the surface structure of a PEGylated liposome and its interaction with the ionic environment present under physiological conditions. Lipids that form both gel and liquid-crystalline membranes have been used in our study. By varying the salt concentration in the Langmuir film experiment and including salt at the physiological level in the simulation, we have studied the effect of salt ions present in the blood plasma on the structure of the poly(ethylene glycol) (PEG) layer. We have also studied the interaction between the PEG layer and the lipid bilayer in both the liquid-crystalline and gel states. The MD simulation shows two clear results: (a) The Na(+) ions form close interactions with the PEG oxygens, with the PEG chains forming loops around them and (b) PEG penetrates the lipid core of the membrane for the case of a liquid-crystalline membrane but is excluded from the tighter structure of the gel membrane. The Langmuir monolayer results indicate that the salt concentration affects the PEGylated lipid system, and these results can be interpreted in a fashion that is in agreement with the results of our MD simulation. We conclude that the currently accepted picture of the PEG surface layer acting as a generic neutral hydrophilic polymer entirely outside the membrane, with its effect explained through steric interactions, is not sufficient. The phenomena we have observed may affect both the interaction between the liposome and bloodstream proteins and the liquid-crystalline-gel transition and is thus relevant to nanotechnological drug delivery device design.
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Affiliation(s)
- Michał Stepniewski
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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