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Walter V, Ruscher C, Gola A, Marques CM, Benzerara O, Thalmann F. Ripple-like instability in the simulated gel phase of finite size phosphocholine bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183714. [PMID: 34331947 DOI: 10.1016/j.bbamem.2021.183714] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 07/14/2021] [Accepted: 07/23/2021] [Indexed: 11/30/2022]
Abstract
Atomistic molecular dynamics simulations have reached a degree of maturity that makes it possible to investigate the lipid polymorphism of model bilayers over a wide range of temperatures. However if both the fluid Lα and tilted gel [Formula: see text] states are routinely obtained, the [Formula: see text] ripple phase of phosphatidylcholine lipid bilayers is still unsatifactorily described. Performing simulations of lipid bilayers made of different numbers of DPPC (1,2-dipalmitoylphosphatidylcholine) molecules ranging from 32 to 512, we demonstrate that the tilted gel phase [Formula: see text] expected below the pretransition cannot be obtained for large systems (equal or larger than 94 DPPC molecules) through common simulations settings or temperature treatments. Large systems are instead found in a disordered gel phase which display configurations, topography and energies reminiscent from the ripple phase [Formula: see text] observed between the pretransition and the main melting transition. We show how the state of the bilayers below the melting transition can be controlled and depends on thermal history and conditions of preparations. A mechanism for the observed topographic instability is suggested.
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Affiliation(s)
- Vivien Walter
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, SE1 1DB, London, United Kingdom.
| | - Céline Ruscher
- Institut Charles Sadron, CNRS and University of Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France
| | - Adrien Gola
- Institut Charles Sadron, CNRS and University of Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France
| | - Carlos M Marques
- Institut Charles Sadron, CNRS and University of Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France
| | - Olivier Benzerara
- Institut Charles Sadron, CNRS and University of Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France
| | - Fabrice Thalmann
- Institut Charles Sadron, CNRS and University of Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France.
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2
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Abstract
High resolution structure is presented for the ripple (Pβ') phase of the phospholipid dimyristoylphosphatidylcholine. Low angle X-ray scattering from oriented samples yielded 57 orders, more than twice as many as recorded previously. The determined electron density map has a sawtooth profile similar to the result from lower resolution data, but the features are sharper allowing better estimates for the modulated bilayer profile and the distribution of headgroups along the aqueous interface. Analysis of high resolution wide angle X-ray data shows that the hydrocarbon chains in the longer, major side of the asymmetric sawtooth are packed similarly to the LβF gel phase, with chains in both monolayers coupled and tilted by 18° in the same direction. The absence of Bragg rods that could be associated with the minor side is consistent with disordered chains, as often suggested in the literature. However, the new high resolution bilayer profile strongly suggests that the chains in the two monolayers in the minor side and the curved region are not in registry. This staggered monolayer modulated melting suggests a direction for improving theories of the ripple phase.
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Affiliation(s)
- Kiyotaka Akabori
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA. 15213, USA.
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3
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Barclay TG, Constantopoulos K, Matisons J. Nanotubes Self-Assembled from Amphiphilic Molecules via Helical Intermediates. Chem Rev 2014; 114:10217-91. [DOI: 10.1021/cr400085m] [Citation(s) in RCA: 185] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Thomas G. Barclay
- Flinders Centre for Nanoscale Science & Technology, School of Chemical and Physical Sciences, Flinders University, Adelaide, South Australia 5042, Australia
| | - Kristina Constantopoulos
- Flinders Centre for Nanoscale Science & Technology, School of Chemical and Physical Sciences, Flinders University, Adelaide, South Australia 5042, Australia
| | - Janis Matisons
- Flinders Centre for Nanoscale Science & Technology, School of Chemical and Physical Sciences, Flinders University, Adelaide, South Australia 5042, Australia
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4
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Kamal MA, Pal A, Raghunathan VA, Rao M. Phase behavior of two-component lipid membranes: theory and experiments. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:051701. [PMID: 23004773 DOI: 10.1103/physreve.85.051701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Indexed: 06/01/2023]
Abstract
The structure of the ripple phase of phospholipid membranes remains poorly understood in spite of a large number of theoretical studies, with many experimentally established structural features of this phase unaccounted for. In this article we present a phenomenological theory of phase transitions in single- and two-component achiral lipid membranes in terms of two coupled order parameters: a scalar order parameter describing lipid chain melting, and a vector order parameter describing the tilt of the hydrocarbon chains below the chain-melting transition. This model reproduces all the salient structural features of the ripple phase, providing a unified description of the phase diagram and microstructure. In addition, it predicts a variant of this phase that does not seem to have been experimentally observed. Using this model we have calculated generic phase diagrams of two-component membranes. We have also determined the phase diagram of a two-component lipid membrane from x-ray diffraction studies on aligned multilayers. This phase diagram is found to be in good agreement with that calculated from the model.
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Affiliation(s)
- Md Arif Kamal
- Raman Research Institute, C. V. Raman Avenue, Bangalore 560 080, India
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5
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Abstract
Highly aligned, substrate supported membranes have made it possible for physical techniques to extract unambiguous structural information previously not accessible from commonly available membrane dispersions, or so-called powder samples. This review will highlight some of the major breakthroughs in model membrane research that have taken place as a result of substrate supported samples.
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6
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Jeong HS, Tanaka S, Yoon DK, Choi SW, Kim YH, Kawauchi S, Araoka F, Takezoe H, Jung HT. Spontaneous Chirality Induction and Enantiomer Separation in Liquid Crystals Composed of Achiral Rod-Shaped 4-Arylbenzoate Esters. J Am Chem Soc 2009; 131:15055-60. [DOI: 10.1021/ja905785d] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hyeon Su Jeong
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Shingo Tanaka
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Dong Ki Yoon
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Suk-Won Choi
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Yun Ho Kim
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Susumu Kawauchi
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Fumito Araoka
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Hideo Takezoe
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Hee-Tae Jung
- Department of Chemical and Biomolecular Engineering (BK-21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-42 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
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7
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Jin S, Jeong KU, Tu Y, Graham MJ, Wang J, Harris FW, Cheng SZD. Structure of Macroscopic Monodomains and Its Soft Confinements of Chiral Smectic Phases on Crystallization in a Main-Chain Nonracemic Liquid Crystalline Polyester. Macromolecules 2007. [DOI: 10.1021/ma070821p] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shi Jin
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Kwang-Un Jeong
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Yingfeng Tu
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Matthew J. Graham
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Jing Wang
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Frank W. Harris
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
| | - Stephen Z. D. Cheng
- Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
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8
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Eisenblätter J, Winter R. Pressure effects on the structure and phase behavior of DMPC-gramicidin lipid bilayers: a synchrotron SAXS and 2H-NMR spectroscopy study. Biophys J 2005; 90:956-66. [PMID: 16299078 PMCID: PMC1367120 DOI: 10.1529/biophysj.105.069799] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The influence of Gramicidin D (GD) incorporation on the structure and phase behavior of aqueous dispersions of DMPC lipid bilayers has been studied using small-angle x-ray scattering (SAXS) and (2)H-NMR spectroscopy. The experiments covered a temperature range from -10 degrees C to 60 degrees C and a pressure range of 0.001-4 kbar. Pressure was used to be able to tune the lipid bilayer conformational order and phase state and because high pressure is an important feature of certain natural biotopes. The data show that, depending on the GD concentration, the structure of the temperature- and pressure-dependent lipid phases is significantly altered by the insertion of the polypeptide, and a p,T-phase diagram could be obtained for intermediate GD concentrations. Upon gramicidin insertion, a rather narrow fluid-gel coexistence regions is formed. Two gel phases are induced which are different from those of the pure lipid bilayer system and which separate at low temperatures/high pressures. For both the temperature- and pressure-induced fluid-to-gel transition, a similar pseudocritical transitional behavior is observed, which is even more pronounced upon incorporation of the peptide.
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Affiliation(s)
- J Eisenblätter
- Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, University of Dortmund, D-44227 Dortmund, Germany
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9
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Katsaras J, Harroun TA, Pencer J, Nieh MP. “Bicellar” Lipid Mixtures as used in Biochemical and Biophysical Studies. Naturwissenschaften 2005; 92:355-66. [PMID: 16021408 DOI: 10.1007/s00114-005-0641-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Over the past decade "bicellar" lipid mixtures composed of the long-chain dimyristoyl phosphatidylcholine (DMPC) and the short-chain dihexanoyl PC (DHPC) molecules have emerged as a powerful medium for studying membrane associated, biologically relevant macromolecules and assemblies. Depending on temperature, lipid concentration and composition these lipid mixtures can assume a variety of morphologies, some of them alignable in the presence of a magnetic field. This article will examine the biophysical studies that have elucidated the various morphologies assumed by these lipid mixtures, and their use in the biochemical studies of biomolecules.
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Affiliation(s)
- John Katsaras
- National Research Council, Chalk River Laboratories, Chalk River, Ontario, Canada.
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10
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Sengupta K, Raghunathan VA, Katsaras J. Structure of the ripple phase of phospholipid multibilayers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2003; 68:031710. [PMID: 14524791 DOI: 10.1103/physreve.68.031710] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2003] [Indexed: 05/24/2023]
Abstract
We present electron density maps (EDMs) of the ripple phase formed by phosphorylcholine lipids such as dimyristoyl phosphatidylcholine (DMPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dihexadecyl phosphatidylcholine, and dilauroyl phosphatidylcholine (DLPC). With the exception of DLPC, the rippled bilayers have a sawtooth shape in all the systems, with one arm being almost twice as long as the other. For DMPC and POPC bilayers, EDMs have been obtained at different temperatures at a fixed relative humidity, and the overall shape of the ripples and the ratio of the lengths of the two arms are found to be insensitive to temperature. EDMs of all the systems with saturated hydrocarbon chains suggest the existence of a mean chain tilt along the ripple wave vector. In the literature it is generally assumed that the asymmetry of the rippled bilayers (absence of a mirror plane normal to the ripple wave vector) arises from a sawtoothlike height profile. However, in the case of DLPC, the height profile is found to be almost symmetric and the asymmetry results mainly from different bilayer thicknesses in the two arms of the ripple. We also present EDMs of the metastable ripple phase of dipalmitoyl phosphatidylcholine, formed on cooling from the L(alpha) phase.
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11
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Raudino A, Castelli F, Briganti G, Cametti C. Anomalous dielectric behavior of undulated lipid membranes. Theoretical model and dielectric spectroscopy measurements of the ripple phase of phosphatidylcholine. J Chem Phys 2001. [DOI: 10.1063/1.1403685] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Sengupta K, Raghunathan VA, Hatwalne Y. Role of tilt order in the asymmetric ripple phase of phospholipid bilayers. PHYSICAL REVIEW LETTERS 2001; 87:055705. [PMID: 11497787 DOI: 10.1103/physrevlett.87.055705] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2000] [Indexed: 05/23/2023]
Abstract
We present the electron density map of the asymmetric ripple phase of dilauroylphosphatidylcholine. We find that the primary feature characterizing the "asymmetry" of the rippled bilayers is the difference in the bilayer thickness in the two arms, and not the asymmetry of the bilayer height profile as is generally assumed. This difference in the bilayer thickness can be attributed to a mean tilt of the hydrocarbon chains of the lipid molecules along the direction of the ripple wave vector. We propose a Landau theory for this phase which takes into account the anisotropic elastic properties of a bilayer with tilt order.
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Affiliation(s)
- K Sengupta
- Raman Research Institute, Bangalore-560 080, India
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13
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Mason PC, Nagle JF, Epand RM, Katsaras J. Anomalous swelling in phospholipid bilayers is not coupled to the formation of a ripple phase. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:030902. [PMID: 11308623 DOI: 10.1103/physreve.63.030902] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2000] [Indexed: 05/23/2023]
Abstract
Aligned stacks of monomethyl and dimethyl dimyristoyl phosphatidylethanolamine (DMPE) lipid bilayers, like the much studied dimyristoyl PC (DMPC) bilayers, swell anomalously in a critical fashion as the temperature is decreased within the fluid phase towards the main transition temperature, T(M). Unlike DMPC bilayers, both monomethyl and dimethyl DMPE undergo transitions into a gel phase rather than a rippled phase below T(M). Although it is not fully understood why there is anomalous swelling, our present results should facilitate theory by showing that the formation of the phase below T(M) is not related to critical phenomena above T(M).
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Affiliation(s)
- P C Mason
- National Research Council, Steacie Institute for Molecular Sciences, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1J0
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14
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Katsaras J, Tristram-Nagle S, Liu Y, Headrick RL, Fontes E, Mason PC, Nagle JF. Clarification of the ripple phase of lecithin bilayers using fully hydrated, aligned samples. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:5668-77. [PMID: 11031625 DOI: 10.1103/physreve.61.5668] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/1999] [Indexed: 11/07/2022]
Abstract
Aligned samples of lipid bilayers have been fully hydrated from water vapor in a different type of x-ray chamber. Our use of aligned samples resolves issues concerning the ripple phase that were ambiguous from previous powder studies. In particular, our x-ray diffraction data conclusively demonstrate that, on cooling from the L alpha to the P beta' phase, both chiral and racemic samples of dipalmitoyl phosphatidylcholine (DPPC) exhibit phase coexistence of long and short ripples with a ripple wavelength ratio lambda L/lambda S approximately 1.8. Moreover, the long ripple always forms an orthorhombic unit cell (gamma L = 90 degrees), strongly supporting the possibility that these ripples are symmetric. In contrast, gamma S for short ripples was consistently different from 90 degrees, implying asymmetric ripples. We continue to find no evidence that chirality affects the structure of rippled bilayers. The relative thermodynamic stability of the two types of ripples was investigated and a qualitative free energy diagram is given in which the long ripple phase is metastable. Finally, we suggest a kinetic mechanism, involving loss of water, that promotes formation of the metastable long ripple phase for special thermal protocols.
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Affiliation(s)
- J Katsaras
- National Research Council, Chalk River Laboratories, Ontario, Canada
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15
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Checchetti A, Chidichimo G, Golemme A, Grasso D, Imbardelli D, La Rosa C, Nicoletta F, Westerman P. On the stability of the ripple phase in the DPPC/PLPC/water ternary system. Chem Phys Lipids 1997. [DOI: 10.1016/s0009-3084(97)00086-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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16
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MacKintosh FC. Internal structures in membranes: Ripples, hats, saddles, and egg cartons. Curr Opin Colloid Interface Sci 1997. [DOI: 10.1016/s1359-0294(97)80080-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Woodward JT, Zasadzinski JA. High-resolution scanning tunneling microscopy of fully hydrated ripple-phase bilayers. Biophys J 1997; 72:964-76. [PMID: 9017222 PMCID: PMC1185620 DOI: 10.1016/s0006-3495(97)78731-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A modified freeze-fracture replication technique for use with the scanning tunneling microscope (STM) has provided a quantitative, high-resolution description of the waveform and amplitude of rippled bilayers in the P beta' phase of dimyristoylphosphatidylcholine (DMPC) in excess water. The ripples are uniaxial and asymmetrical, with a temperature-dependent amplitude of 2.4 nm near the chain melting temperature that decreases to zero at the chain crystallization temperature. The wavelength of 11 nm does not change with temperature. The observed ripple shape and the temperature-induced structural changes are not predicted by any current theory. Calibration and reproducibility of the STM/replica technique were tested with replicas of well-characterized bilayers of cadmium arachidate on mica that provide regular 5.5-nm steps. STM images were analyzed using a cross-correlation averaging program to eliminate the effects of noise and the finite size and shapes of the metal grains that make up the replica. The correlation averaging allowed us to develop a composite ripple profile averaged over hundreds of individual ripples measured on different samples with different STM tips. The STM/replica technique avoids many of the previous artifacts of biological STM imaging and can be used to examine a variety of periodic hydrated lipid and protein samples at a lateral resolution of about 1 nm and a vertical resolution of about 0.3 nm. This resolution is superior to conventional and tapping mode AFM to soft biological materials; the technique is substrate-free, and the conductive and chemically uniform replicas make image interpretation simple and direct.
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Affiliation(s)
- J T Woodward
- Department of Physics, University of California, Santa Barbara 93106-5080, USA
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18
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Seifert U, Shillcock J, Nelson P. Role of Bilayer Tilt Difference in Equilibrium Membrane Shapes. PHYSICAL REVIEW LETTERS 1996; 77:5237-5240. [PMID: 10062750 DOI: 10.1103/physrevlett.77.5237] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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19
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Sun WJ, Tristram-Nagle S, Suter RM, Nagle JF. Structure of the ripple phase in lecithin bilayers. Proc Natl Acad Sci U S A 1996; 93:7008-12. [PMID: 8692934 PMCID: PMC38925 DOI: 10.1073/pnas.93.14.7008] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The phases of the x-ray form factors are derived for the ripple (Pbeta') thermodynamic phase in the lecithin bilayer system. By combining these phases with experimental intensity data, the electron density map of the ripple phase of dimyristoyl-phosphatidylcholine is constructed. The phases are derived by fitting the intensity data to two-dimensional electron density models, which are created by convolving an asymmetric triangular ripple profile with a transbilayer electron density profile. The robustness of the model method is indicated by the result that many different models of the transbilayer profile yield essentially the same phases, except for the weaker, purely ripple (0,k) peaks. Even with this residual ambiguity, the ripple profile is well determined, resulting in 19 angstroms for the ripple amplitude and 10 degrees and 26 degrees for the slopes of the major and the minor sides, respectively. Estimates for the bilayer head-head spacings show that the major side of the ripple is consistent with gel-like structure, and the minor side appears to be thinner with lower electron density.
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Affiliation(s)
- W J Sun
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
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20
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Woodward JT, Zasadzinski JA. Amplitude, wave form, and temperature dependence of bilayer ripples in the P beta ' phase. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 53:R3044-R3047. [PMID: 9964762 DOI: 10.1103/physreve.53.r3044] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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