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Krzyzanowski N, Porcar L, Perez-Salas U. A Small-Angle Neutron Scattering, Calorimetry and Densitometry Study to Detect Phase Boundaries and Nanoscale Domain Structure in a Binary Lipid Mixture. MEMBRANES 2023; 13:323. [PMID: 36984710 PMCID: PMC10051979 DOI: 10.3390/membranes13030323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/06/2023] [Accepted: 03/07/2023] [Indexed: 06/18/2023]
Abstract
Techniques that can probe nanometer length scales, such as small-angle neutron scattering (SANS), have become increasingly popular to detect phase separation in membranes. But to extract the phase composition and domain structure from the SANS traces, complementary information is needed. Here, we present a SANS, calorimetry and densitometry study of a mixture of two saturated lipids that exhibits solidus-liquidus phase coexistence: 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (dDPPC, tail-deuterated DPPC) and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). With calorimetry, we investigated the phase diagram for this system and found that the boundary traces for both multilamellar vesicles (MLVs) as well as 50 nm unilamellar vesicles overlap. Because the solidus boundary was mostly inaccessible by calorimetry, we investigated it by both SANS and molecular volume measurements for a 1:1 dDPPC:DLPC lipid mixture. From the temperature behavior of the molecular volume for the 1:1 dDPPC:DLPC mixture, as well as the individual molecular volume of each lipid species, we inferred that the liquidus phase consists of only fluid-state lipids while the solidus phase consists of lipids that are in gel-like states. Using this solidus-liquidus phase model, the SANS data were analyzed with an unrestricted shape model analysis software: MONSA. The resulting fits show irregular domains with dendrite-like features as those previously observed on giant unilamellar vesicles (GUVs). The surface pair correlation function describes a characteristic domain size for the minority phase that decreases with temperature, a behavior found to be consistent with a concomitant decrease in membrane mismatch between the liquidus and solidus phases.
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Affiliation(s)
- Natalie Krzyzanowski
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60608, USA
| | - Lionel Porcar
- Large Scale Structures Group, Institut Laue-Langevin, CEDEX 9, 38042 Grenoble, France
| | - Ursula Perez-Salas
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60608, USA
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2
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Tamai N, Matsuki H, Goto M. Phase Imaging of Phosphatidylcholine Bilayer Membranes by Prodan Fluorescence. MEMBRANES 2022; 12:1219. [PMID: 36557126 PMCID: PMC9784652 DOI: 10.3390/membranes12121219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 11/29/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
Prodan (6-propiponyl-2-(N,N-dimethylamino)naphthalene) is well known as a polarity-sensitive fluorescent probe and has a high capability of detecting structural changes occurring within phospholipid bilayer membranes. In this study, we carried out the fluorescence spectroscopic observation of bilayer phase behavior for a series of symmetric saturated diacylphosphatidylcholines (CnPCs) with different acyl-chain length n (n = 12-15 and 19-22) using Prodan as a membrane probe to confirm the availability of Prodan along with the previous results for the CnPC bilayer membranes (n = 16-18). The results were discussed by constructing spectral three-dimensional (3D) imaging plots for visualizing the change in bilayer phase states with temperature or pressure to verify the functionality of this 3D imaging plot. It was found that the Prodan fluorescence technique is applicable to the detection of the changes in the bilayer phase states of all CnPCs with a few exceptions. One of the most crucial exceptions was that Prodan cannot be used for the detection of the bilayer-gel state of the C21PC bilayer membrane. It was also found that it is only to the CnPC bilayer membranes with n = 15-18 that the 3D imaging plot is adequately and accurately applicable as a useful graphical tool for visually detecting the bilayer phase states. This is a disadvantageous feature of this technique brought about by the high sensitivity of Prodan as a membrane probe. Further detailed studies on the molecular behavior of Prodan will enable us to find a more useful way of utilizing this membrane probe.
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Affiliation(s)
| | | | - Masaki Goto
- Correspondence: ; Tel.: +81-88-656-7520; Fax: +81-88-655-3162
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3
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Matsuki H, Goto M, Motohashi M, Kiguchi A, Nakao T, Tamai N. Formation of intermediate gel-liquid crystalline phase on medium-chain phosphatidylcholine bilayers: Phase transitions depending on the bilayer packing. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183197. [PMID: 31958435 DOI: 10.1016/j.bbamem.2020.183197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 12/27/2019] [Accepted: 01/15/2020] [Indexed: 11/28/2022]
Abstract
The bilayer phase transitions of medium-chain phosphatidylcholines with linear saturated acyl chains (Cn = 12, 13 and 14) were measured by high-pressure light-transmittance measurements and differential scanning calorimetry to investigate the formation of intermediate gel-liquid crystalline phase called Lx phase. The constructed phase diagrams showed that there existed a distinct region of the Lx phase between ripple gel (Pβ') and liquid crystalline (Lα) phase for multilamellar vesicle bilayers of C12PC and C13PC. The Lx phase of the C12PC bilayer was metastable at all pressures and disappeared at a higher pressure. In the C13PC bilayer, the Lx phase was stable and also disappeared at a higher pressure but its region markedly shrunk. By contrast, the Lx phase was not detected for the C14PC bilayer. Effects of other factors such as vesicle size and solvent substitution on the Lx phase of the C13PC bilayer were also examined. A decrease in vesicle size and solvent substitution from water to 50 wt% ethylene glycol solution promoted the Lx-phase formation as opposed to the effects of acyl-chain elongation and pressurization. The fluorescence data of the C13PC bilayer with different vesicle sizes showed that the Lx phase is caused by the difference of local packing in the bilayer. Considering these facts, we concluded that the Lx phase is an intermediate gel-Lα phase that has gel-phase monolayers with negative curvature and Lα-phase monolayers with positive curvature. The formation mechanism of the Lx-phase in stacked bilayers and dispersed vesicles is also explainable by this difference in packing state.
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Affiliation(s)
- Hitoshi Matsuki
- Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan.
| | - Masaki Goto
- Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan
| | - Makiko Motohashi
- Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan
| | - Aoi Kiguchi
- Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan
| | - Toshiki Nakao
- Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan
| | - Nobutake Tamai
- Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan
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4
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Matsuki H, Goto M, Tada K, Tamai N. Thermotropic and barotropic phase behavior of phosphatidylcholine bilayers. Int J Mol Sci 2013; 14:2282-302. [PMID: 23348926 PMCID: PMC3587988 DOI: 10.3390/ijms14022282] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 01/11/2013] [Accepted: 01/15/2013] [Indexed: 11/17/2022] Open
Abstract
Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of some major phospholipids contained in biological membranes, phosphatidylcholines (PCs), depending on temperature and pressure. Bilayers of dipalmitoylphosphatidylcholine (DPPC), which is the most representative lipid in model membrane studies, will first be explained. Then, the bilayer phase behavior of various kinds of PCs with different molecular structures is revealed from the temperature-pressure phase diagrams, and the difference in phase stability among these PC bilayers is discussed in connection with the molecular structure of the PC molecules. Furthermore, the solvent effect on the phase behavior is also described briefly.
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Affiliation(s)
- Hitoshi Matsuki
- Department of Life System, Institute of Technology and Science, The University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan; E-Mails: (M.G.); (N.T.)
| | - Masaki Goto
- Department of Life System, Institute of Technology and Science, The University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan; E-Mails: (M.G.); (N.T.)
| | - Kaori Tada
- Department of Material Science and Technology, Kochi National College of Technology, 200-1 Monobe-otsu, Nankoku, Kochi 783-8508, Japan; E-Mail:
| | - Nobutake Tamai
- Department of Life System, Institute of Technology and Science, The University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan; E-Mails: (M.G.); (N.T.)
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5
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Recent Progress in Density Functional Methodology for Biomolecular Modeling. STRUCTURE AND BONDING 2013. [DOI: 10.1007/978-3-642-32750-6_1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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6
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Thermotropic and barotropic phase transitions of dilauroylphosphatidylcholine bilayer. Chem Phys Lipids 2008; 153:138-43. [DOI: 10.1016/j.chemphyslip.2008.03.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 02/15/2008] [Accepted: 03/03/2008] [Indexed: 11/17/2022]
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7
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Brocca P, Cantù L, Corti M, Del Favero E, Motta S, Nodari MC. DC13PC bilayers from anomalous swelling to main transition: An X-ray scattering investigation. J Colloid Interface Sci 2007; 312:34-41. [PMID: 17258762 DOI: 10.1016/j.jcis.2006.12.067] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 12/18/2006] [Accepted: 12/29/2006] [Indexed: 10/23/2022]
Abstract
We have performed small-angle (SAXS) and wide-angle X-ray scattering (WAXS) measurements on the lamellar phase and on large unilamellar vesicles (LUVs) of DC(13)PC in the temperature range corresponding to the anomalous swelling regime of multibilayer systems, adjacent to the chain melting transition, and across the transition. Our SAXS measurements indicate that on cooling from the L(alpha) phase, a uniform progressive swelling of the lamellar system to anomalous distances, starting approximately 2 degrees C above the main transition, is followed by a region of coexistence, covering the width of the transition ( approximately 0.6 degrees C). Across the transition region, a progressively increasing volume fraction of gel phase with a constant P (beta') interlamellar distance coexists with a decreasing amount of nongel phase that keeps on swelling to longer distances. Along both the swelling and the transition regions, anomalies in the specific heat are observed revealing a two-step process. Simultaneous WAXS experiments show a progressive "density" increase along the swelling region, constituting a direct spectroscopic evidence of an "evolving membrane" approaching the transition in a bulk real system. Calorimetric and densitometric measurements on LUVs are also presented, together with WAXS results, that show the existence of a double step main transition in a single component nanosized closed bilayer.
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Affiliation(s)
- P Brocca
- Department of Chemistry, Biochemistry and Biotechnologies for Medicine, University of Milan, LITA, Via F.lli Cervi, 93 Segrate, Milan, Italy
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Brocca P, Cantù L, Corti M, Del Favero E, Motta S, Nodari M. Curved single-bilayers in the region of the anomalous swelling: Effect of curvature and chain length. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2006.08.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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9
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Dahbi L, Arbel-Haddad M, Lesieur P, Bourgaux C, Ollivon M. A long ripple phase in DLPC–decylglucoside mixture evidenced by synchrotron SAXS coupled to DSC. Chem Phys Lipids 2006; 139:43-53. [PMID: 16303121 DOI: 10.1016/j.chemphyslip.2005.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Revised: 09/16/2005] [Accepted: 10/04/2005] [Indexed: 11/23/2022]
Abstract
For the first time, the secondary ripple phase in a system containing dilauroyl phosphatidylcholine (DLPC) is observed by small-angle X-ray diffraction (SAXS). The SAXS profile exhibits many well-resolved peaks. The fast formation of this phase upon cooling from the liquid crystalline lamellar phase L(alpha) is induced by addition of C10G with molar ratio 0.17< or = R = [C10G]/[DLPC]< or = 0.49. For R < 0.17, the primary P(beta') ripple phase is observed. In contrast to the P(beta') phase, which shows a sawtooth shape, the secondary ripple structure is thought to be symmetric. The ripple length (190 angstroms) and the bilayer spacing (74 angstroms) are larger than in the primary ripple phase. Lattice parameters of the new long ripple phase, which are quite insensitive to temperature, vary slightly linearly with R. In this study, structural and thermodynamic changes within the samples were followed as a function of temperature by time-resolved X-ray diffraction coupled to DSC.
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Affiliation(s)
- Louisa Dahbi
- LURE, Université Paris-Sud, Bâtiment 209D, 91405 Orsay Cedex, France
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10
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Enders O, Ngezahayo A, Wiechmann M, Leisten F, Kolb HA. Structural calorimetry of main transition of supported DMPC bilayers by temperature-controlled AFM. Biophys J 2004; 87:2522-31. [PMID: 15454447 PMCID: PMC1304671 DOI: 10.1529/biophysj.104.040105] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Accepted: 06/21/2004] [Indexed: 11/18/2022] Open
Abstract
Atomic force microscopy at high temperature resolution (DeltaT < or approximately 0.1 K) provided a quantitative structural calorimetry of the transition from the fluid (Lalpha)- to the gel (Pbeta')-phase of supported dimyristoylphosphatidylcholine bilayers. Besides a determination of the main transition temperature (T0) and the van't Hoff transition enthalpy (DeltaHvH), the structural analysis in the nm-scale at T close to T0 of the ripple phase allowed an experimental estimation of the area of cooperative units from small lipid domains. Thereby, the corresponding transition enthalpy (DeltaH) of single molecules could be determined. The lipid organization and the corresponding parameters T0 and DeltaHvH (DeltaH) were modulated by heptanol or external Ca2+ and compared with physiological findings. The size of the cooperative unit was not significantly affected by the presence of 1 mM heptanol. The observed linear relationship of DeltaHvH and T0 was discussed in terms of a change in heat capacity.
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Affiliation(s)
- O Enders
- Institute of Biophysics, University Hannover, Hannover, Germany
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11
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Harroun TA, Nieh MP, Watson MJ, Raghunathan VA, Pabst G, Morrow MR, Katsaras J. Relationship between the unbinding and main transition temperatures of phospholipid bilayers under pressure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 69:031906. [PMID: 15089321 DOI: 10.1103/physreve.69.031906] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Indexed: 05/24/2023]
Abstract
Using neutron diffraction and a specially constructed high pressure cell suitable for aligned multibilayer systems, we have studied, as a function of pressure, the much observed anomalous swelling regime in dimyristoyl- and dilauroyl-phosphatidylcholine bilayers, DMPC and DLPC, respectively. We have also reanalyzed data from a number of previously published experiments and have arrived at the following conclusions. (a). The power law behavior describing anomalous swelling is preserved in all PC bilayers up to a hydrostatic pressure of 240 MPa. (b). As a function of increasing pressure there is a concomitant decrease in the anomalous swelling of DMPC bilayers. (c). For PC lipids with hydrocarbon chains >or=13 carbons the theoretical unbinding transition temperature T small star, filled is coupled to the main gel-to-liquid crystalline transition temperature T(M). (d). DLPC is intrinsically different from the other lipids studied in that its T small star, filled is not coupled to T(M). (e). For DLPC bilayers we predict a hydrostatic pressure (>290 MPa) where unbinding may occur.
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Affiliation(s)
- T A Harroun
- National Research Council, Steacie Institute for Molecular Sciences, Chalk River, Ontario, Canada K0J 1J0
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12
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Uhríková D, Rapp G, Balgavý P. Condensed lamellar phase in ternary DNA-DLPC-cationic gemini surfactant system: a small-angle synchrotron X-ray diffraction study. Bioelectrochemistry 2002; 58:87-95. [PMID: 12401574 DOI: 10.1016/s1567-5394(02)00122-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We report on a small-angle synchrotron X-ray diffraction study of dilauroylphosphatidylcholine (DLPC) liposomes aggregated with high molecular DNA in the presence of 1,4-butanediammonium-N,N'-dilauryl-N,N,N',N'-tetramethyl gemini surfactant cations (C12GS). The aggregates prepared at the DLPC/C12GS/DNA phosphate group=2:1:1.6 molar ratio in 0.0015 mol x l(-1) NaCl aqueous solution exhibit Bragg reflections due to lamellar lipid bilayer stacking and the Bragg reflection typical of one-dimensional DNA lattice with parallel strands intercalated between lipid bilayers. In this condensed fluid lamellar L(alpha)(c) phase, the interactions between DNA and charged bilayers damp the thermally induced bilayer undulations. The diffraction data obtained with the mixture of DLPC liposomes and DNA (at DNA phosphate group/DLPC=0.8:1 molar ratio) indicate a DNA-lipid interaction in the absence of C12GS.
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Affiliation(s)
- Daniela Uhríková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, J A Comenius University, Odbojárov 10, SK-832 32, Bratislava, Slovak Republic
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Takahashi H, Ohta N, Hatta I. X-ray diffraction study on interdigitated structure of phosphatidylcholines in glycerol. Chem Phys Lipids 2001; 112:93-7. [PMID: 11518576 DOI: 10.1016/s0009-3084(01)00169-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
X-ray diffraction was used to study the interdigitated structure of phosphatidylcholines (PCs) in glycerol. In this study, we investigated five different saturated diacyl PCs with carbon number from 14 to 18 in their acyl chains. It was found that lamellar spacings increase linearly as increasing the carbon number in the chains and that the increment is 0.10+/-0.01 nm per one carbon atom. The lamellar diffraction intensity data were analyzed, by applying a method proposed by Adachi [Chem. Phys. Lipids 107 (2000) 93]. The results indicate that the moiety around polar headgroup regions is almost unchanged, being independent of the carbon number.
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Affiliation(s)
- H Takahashi
- Department of Physics, Gunma University, 4-2 Aramaki, Maebashi 371-8510, Japan.
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Koynova R, Caffrey M. Phases and phase transitions of the phosphatidylcholines. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1376:91-145. [PMID: 9666088 DOI: 10.1016/s0304-4157(98)00006-9] [Citation(s) in RCA: 786] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
LIPIDAT (http://www.lipidat.chemistry.ohio-state.edu) is an Internet accessible, computerized relational database providing access to the wealth of information scattered throughout the literature concerning synthetic and biologically derived polar lipid polymorphic and mesomorphic phase behavior and molecular structures. Here, a review of the data subset referring to phosphatidylcholines is presented together with an analysis of these data. This subset represents ca. 60% of all LIPIDAT records. It includes data collected over a 43-year period and consists of 12,208 records obtained from 1573 articles in 106 different journals. An analysis of the data in the subset identifies trends in phosphatidylcholine phase behavior reflecting changes in lipid chain length, unsaturation (number, isomeric type and position of double bonds), asymmetry and branching, type of chain-glycerol linkage (ester, ether, amide), position of chain attachment to the glycerol backbone (1,2- vs. 1,3-) and head group modification. Also included is a summary of the data concerning the effect of pressure, pH, stereochemical purity, and different additives such as salts, saccharides, amino acids and alcohols, on phosphatidylcholine phase behavior. Information on the phase behavior of biologically derived phosphatidylcholines is also presented. This review includes 651 references.
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Affiliation(s)
- R Koynova
- Institute of Biophysics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Koynova R, Tenchov B, Rapp G. Mixing behavior of saturated short-chain phosphatidylcholines and fatty acids. Chem Phys Lipids 1997. [DOI: 10.1016/s0009-3084(97)00043-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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17
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Milhaud J, Berrehar J, Lancelin JM, Michels B, Raffard G, Dufourc EJ. Association of polyene antibiotics with sterol-free lipid membranes. II. Hydrophobic binding of nystatin to dilauroylphosphatidylcholine bilayers. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1326:54-66. [PMID: 9188800 DOI: 10.1016/s0005-2736(97)00008-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Interaction of nystatin A1 with multilamellar vesicles (MLV) of dilauroylphosphatidylcholine (DLPC), observed either by adding nystatin to preformed MLV (mixtures I) or by incorporating it during the formation of vesicles (mixtures II, inner lamellas of MLV in contact with nystatin) was investigated for 0.002 < or = nystatin/DLPC = R(A) < or = 0.20, by four complementary methods. The main results were: (i) Ultraviolet absorption and circular dichroism (CD) spectra of mixtures I revealed the occurrence of a saturable association with a stoichiometry (R(A) = 0.007 +/- 0.002) constant between 3 and 33 degrees C. (ii) By differential scanning calorimetry, thermograms of the two types of mixtures were similar only when water was in great excess. In the opposite (e.g., (H2O)/(DLPC) = R(W) < or = 300), mixture II thermograms displayed two features, upshifted by about 6.5 degrees C with respect to the sharp peak observed with mixture I, resembling those obtained for pure DLPC when the low-temperature phase was the subgel phase. For this R(W), the nystatin absolute concentrations were those for which nystatin form superaggregates as revealed by the nystatin CD spectra. It is proposed that these superaggregates are excluded from the interlamellar spacings of MLV and exert a pumping action on the interlamellar water. The subsequent dehydration of the inner lamellas is thought to convert them into the subgel state. (iii) 2H-NMR spectra of sn-2-perdeuterated DLPC MLV + nystatin mixtures II, confirmed such a temperature shift of the main transition. They showed, in addition, an ordering of the aliphatic chains immediately above the transition temperature, equivalent to a bilayer thickening of 2 A.
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Affiliation(s)
- J Milhaud
- Laboratoire de Physicochimie biomoléculaire et cellulaire (UA CNRS 2056), Université Paris VI, France
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18
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Bonev B, Morrow MR. Effects of hydrostatic pressure on bilayer phase behavior and dynamics of dilauroylphosphatidylcholine. Biophys J 1996; 70:2727-35. [PMID: 8744310 PMCID: PMC1225252 DOI: 10.1016/s0006-3495(96)79842-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Deuterium nuclear magnetic resonance spectroscopy was used to study the thermotropic phase behavior of dilauroylphosphatidylcholine (DLPC) bilayers at pressures up to 221 MPa. Pressure was found to separate the liquid crystal to gel transition from the gel to ordered crystalline phase transition. The jump in chain order observed on cooling through the transition into the gel phase was found to be small and thus consistent with the trend in longer chain saturated diacyl phosphatidylcholines. On cooling, DLPC was observed to enter an unusual state above the transition into the gel phase. This unusual state displayed fluid-like conformational order but short transverse relaxation times. It was found to be much better pronounced and to span a broader temperature range at elevated pressure than at lower pressures. Transverse relaxation measurements of deuterons on the chain alpha-carbons revealed a substantial slowing of molecular motions within the temperature range of the unusual fluid phase. The observation of such a phase at high pressure appears to be consistent with recent reports of an unusual fluid phase, Lx, in DLPC at ambient pressure.
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Affiliation(s)
- B Bonev
- Department of Physics, Memorial University of Newfoundland, St. John's, Canada
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