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Kurakin S, Badreeva D, Dushanov E, Shutikov A, Efimov S, Timerova A, Mukhametzyanov T, Murugova T, Ivankov O, Mamatkulov K, Arzumanyan G, Klochkov V, Kučerka N. Arrangement of lipid vesicles and bicelle-like structures formed in the presence of Aβ(25-35) peptide. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184237. [PMID: 37820938 DOI: 10.1016/j.bbamem.2023.184237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/31/2023] [Accepted: 10/03/2023] [Indexed: 10/13/2023]
Abstract
Our complementary experimental data and molecular dynamics (MD) simulations results reveal the structure of previously observed lipid bicelle-like structures (BLSs) formed in the presence of amyloid-beta peptide Aβ(25-35) below the main phase transition temperature (Tm) of saturated phosphatidylcholine lipids and small unilamellar vesicles (SUVs) above this temperature. First, we show by using solid-state 31P nuclear magnetic resonance (NMR) spectroscopy that our BLSs being in the lipid gel phase demonstrate magnetic alignment along the magnetic field of NMR spectrometer and undergo a transition to SUVs in the lipid fluid phase when heated through the Tm. Secondly, thanks to the BLS alignment we present their lipid structure. Lipids are found located not only in the flat bilayered part but also around its perimeter, which is corroborated by the results of coarse-grained (CG) MD simulations. Finally, peptides appear to mix randomly with lipids in SUVs while assuming predominantly unordered secondary structures revealed by circular dichroism (CD), Raman spectroscopy, and all-atom MD simulations. Importantly, the former is changing little when the system undergoes morphological transitions between BLSs and SUVs. Our structural results then offer a platform for studying and understanding mechanisms of morphological transformations caused by the disruptive effect of amyloid-beta peptides on the lipid bilayer.
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Affiliation(s)
- Sergei Kurakin
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia; Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia.
| | - Dina Badreeva
- Meshcheryakov Laboratory of Information Technologies, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Ermuhammad Dushanov
- Laboratory of Radiation Biology, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Artyom Shutikov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Sergey Efimov
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Ayzira Timerova
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Timur Mukhametzyanov
- Butlerov Chemistry Institute, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Tatiana Murugova
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Oleksandr Ivankov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Kahramon Mamatkulov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Grigory Arzumanyan
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Vladimir Klochkov
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Norbert Kučerka
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia; Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov 10, Bratislava 832 32, Slovakia.
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Koshiyama K, Nakata K. Effects of lipid saturation on bicelle to vesicle transition of a binary phospholipid mixture: a molecular dynamics simulation study. SOFT MATTER 2023; 19:7655-7662. [PMID: 37782209 DOI: 10.1039/d3sm00904a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Controlling the transition from lipid bicelles to vesicles is essential for producing engineered vesicles. We perform coarse-grained molecular dynamics (CGMD) simulations of unsaturated/saturated lipid mixtures to clarify the effects of lipid unsaturation on vesiculation at the molecular scale. The results demonstrate that vesiculation depends on the concentration of unsaturated lipids and the degree of unsaturation. The probability of vesiculation increases linearly with the apparent unsaturated lipid concentration at a low degree of unsaturation. Higher degrees of unsaturation lead to phase segregation within the binary bicelles, reducing the probability of vesiculation. A comparison between CGMD simulations and the conventional theory of vesiculation shows that the theoretical predictions of binary lipid systems must explicitly include phase segregation effects. Furthermore, simulations with biased lipid distributions reveal that vesiculation is facilitated by the preconcentration of unsaturated lipids in the core region of the bicelle but is then temporally limited as the unsaturated lipids move to the bicelle edges. These findings advance theoretical and experimental studies on binary lipid systems and promote the development of tailor-made vesicles.
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Affiliation(s)
- Kenichiro Koshiyama
- Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima, 770-8506, Japan.
| | - Kazuki Nakata
- Graduate School of Sciences and Technology for Innovation, Tokushima University, Tokushima 770-8506, Japan.
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Santos-Luna D, Sixto-López Y, Bravo-Alfaro D, Cano-Sarmiento C, García H, Correa-Basurto J. Design and simulation of a caprylic acid enzymatically modified phosphatidylcholine micelle using a coarse-grained molecular dynamics simulations approach. J Biomol Struct Dyn 2023; 41:13902-13913. [PMID: 36826442 DOI: 10.1080/07391102.2023.2180434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 02/08/2023] [Indexed: 02/25/2023]
Abstract
Computationally simulated micelle models provide useful structural information on the molecular and biological sciences. One strategy to study the self-aggregation process of surfactant molecules that make up a micelle is through molecular dynamics (MD) simulations. In this study, a theoretical approach with a coarse-grained MD simulation (CG-MD) was employed to evaluate the critical micellar concentration (CMC), the micellization process, building a tridimensional (3D) model system of a micelle using data from the experimentally enzymatically modified phospholipids (PL) by phospholipase A1 (PA1). This required enzymatic interesterification of soybean phosphatidylcholine (PC) with caprylic acid, along with purification and characterization by chromatographic techniques to measure the esterified fatty acids and the corresponding PL composition. The number of molecules used in the CG-MD simulation system was determined from the experimental CMC data which was 0.025%. The molecular composition of the system is: 1 C 18:2, 2 C 8:0/8:0, 3 C 8:0/18:3n-9, 4 C 8:0/18:0, 5 C8:0/18:2n-6, 6 C8:0/18:1n-9, and 7 C 8:0/16:0. According to our theoretical results, the micelle model is structurally stable with an average Rg of 3.64 ± 0.10 Å, and might have an elliptical form with a radius of 24.6 Å. Regarding CMC value there was a relationship between the experimental data of the modified PLs and the theoretical analysis by GC-MD, which suggest that the enzymatic modification of PLs does not affect their self-aggregation properties. Finally, the micellar system obtained in the current research can be used as a simple and useful model to design optimal biocompatible nanoemulsions as possible vehicles for bioactive small molecules.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Dalia Santos-Luna
- Unidad de Investigación y Desarrollo de Alimentos, Tecnológico Nacional de México/IT de Veracruz, Veracruz, México
| | - Yudibeth Sixto-López
- Departamento de Química Farmacéutica y Orgánica, Facultad de Farmacia, Universidad de Granada, Campus de Cartuja, Granada, Spain
- Laboratorio de Diseño y Desarrollo de Nuevos Fármacos e Innovación Biotecnológica (Laboratory for the Design and Development of New Drugs and Biotechnological Innovation) SEPI-ESM, Instituto Politécnico Nacional, México, Mexico City, Mexico
| | - Diego Bravo-Alfaro
- Unidad de Investigación y Desarrollo de Alimentos, Tecnológico Nacional de México/IT de Veracruz, Veracruz, México
| | - Cynthia Cano-Sarmiento
- CONACyT-Unidad de Investigación y Desarrollo de Alimentos, Tecnologico Nacional de México/IT de Veracruz, Veracruz, México
| | - Hugo García
- Unidad de Investigación y Desarrollo de Alimentos, Tecnológico Nacional de México/IT de Veracruz, Veracruz, México
| | - José Correa-Basurto
- Laboratorio de Diseño y Desarrollo de Nuevos Fármacos e Innovación Biotecnológica (Laboratory for the Design and Development of New Drugs and Biotechnological Innovation) SEPI-ESM, Instituto Politécnico Nacional, México, Mexico City, Mexico
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Parchekani J, Allahverdi A, Taghdir M, Naderi-Manesh H. Design and simulation of the liposomal model by using a coarse-grained molecular dynamics approach towards drug delivery goals. Sci Rep 2022; 12:2371. [PMID: 35149771 PMCID: PMC8837752 DOI: 10.1038/s41598-022-06380-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/27/2022] [Indexed: 12/19/2022] Open
Abstract
The simulated liposome models provide events in molecular biological science and cellular biology. These models may help to understand the cell membrane mechanisms, biological cell interactions, and drug delivery systems. In addition, the liposomes model may resolve specific issues such as membrane transports, ion channels, drug penetration in the membrane, vesicle formation, membrane fusion, and membrane protein function mechanism. One of the approaches to investigate the lipid membranes and the mechanism of their formation is by molecular dynamics (MD) simulations. In this study, we used the coarse-grained MD simulation approach and designed a liposome model system. To simulate the liposome model, we used phospholipids that are present in the structure of natural cell membranes (1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)). Simulation conditions such as temperature, ions, water, lipid concentration were performed based on experimental conditions. Our results showed a liposome model (ellipse vesicle structure) during the 2100 ns was formed. Moreover, the analysis confirmed that the stretched and ellipse structure is the best structure that could be formed. The eukaryotic and even the bacterial cells have elliptical and flexible structures. Usually, an elliptical structure is more stable than other assembled structures. The results indicated the assembly of the lipids is directed through short-range interactions (electrostatic interactions and, van der Waals interactions). Total energy (Van der Waals and electrostatic interaction energy) confirmed the designed elliptical liposome structure has suitable stability at the end of the simulation process. Our findings confirmed that phospholipids DOPC and DOPE have a good tendency to form bilayer membranes (liposomal structure) based on their geometric shapes and chemical-physical properties. Finally, we expected the simulated liposomal structure as a simple model to be useful in understanding the function and structure of biological cell membranes. Furthermore, it is useful to design optimal, suitable, and biocompatible liposomes as potential drug carriers.
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Affiliation(s)
- Jalil Parchekani
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, 14115-154, Iran
| | - Abdollah Allahverdi
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, 14115-154, Iran
| | - Majid Taghdir
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, 14115-154, Iran.
| | - Hossein Naderi-Manesh
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, 14115-154, Iran. .,Department of Nanobiotechnology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, 14115-154, Iran.
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Smith P, Lorenz CD. LiPyphilic: A Python Toolkit for the Analysis of Lipid Membrane Simulations. J Chem Theory Comput 2021; 17:5907-5919. [PMID: 34450002 DOI: 10.1021/acs.jctc.1c00447] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations are now widely used to study emergent phenomena in lipid membranes with complex compositions. Here, we present LiPyphilic-a fast, fully tested, and easy-to-install Python package for analyzing such simulations. Analysis tools in LiPyphilic include the identification of cholesterol flip-flop events, the classification of local lipid environments, and the degree of interleaflet registration. LiPyphilic is both force field- and resolution-agnostic, and by using the powerful atom selection language of MDAnalysis, it can handle membranes with highly complex compositions. LiPyphilic also offers two on-the-fly trajectory transformations to (i) fix membranes split across periodic boundaries and (ii) perform nojump coordinate unwrapping. Our implementation of nojump unwrapping accounts for fluctuations in the box volume under the NPT ensemble-an issue that most current implementations have overlooked. The full documentation of LiPyphilic, including installation instructions and links to interactive online tutorials, is available at https://lipyphilic.readthedocs.io/en/latest.
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Affiliation(s)
- Paul Smith
- Department of Physics, King's College London, London WC2R 2LS, U.K
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Banerjee A, Tam A, Dutt M. Dendronized vesicles: formation, self-organization of dendron-grafted amphiphiles and stability. NANOSCALE ADVANCES 2021; 3:725-737. [PMID: 36133832 PMCID: PMC9419559 DOI: 10.1039/d0na00773k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/19/2020] [Indexed: 06/12/2023]
Abstract
Fundamental bacterial functions like quorum sensing can be targeted to replace conventional antibiotic therapies. Nanoparticles or vesicles that bind interfacially to charged biomolecules could be used to block quorum sensing pathways in bacteria. Towards this goal, dendronized vesicles (DVs) encompassing polyamidoamine dendron-grafted amphiphiles (PDAs) and dipalmitoyl-sn-glycero-3-phosphocholine lipids are investigated using the molecular dynamics simulation technique in conjunction with an explicit solvent coarse-grained force field. The key physical factors determining the stability of DVs as a function of the dendron generation and relative concentration are identified. The threshold concentration of each dendron generation that yields stable DVs is determined. Dendrons with lower generations rupture the DVs at high relative concentrations due to the electrostatic repulsions between the terminally protonated amines. Whereas, dendrons with intermediate generations demonstrate a mushroom-to-brush transition. Conformational changes in the dendrons expand the outer DV surface, resulting in instability in the DV bilayer. DVs encompassing dendrons with higher generations incur stresses on the bilayer due to their high charge density and spontaneous curvature. The self-organization of PDAs on the DV surface are examined to understand how the asymmetric stresses are minimized across the bilayer. A set of conditions are determined to be conducive for the formation of a single cluster of PDAs that decorates the DV surface like a mesh. Results from this study can potentially guide the design and synthesis of nanoparticles which target quorum sensing pathways in bacteria towards the prevention and treatment of bacterial infections. Furthermore, these nanoparticles can be used in diverse applications in biomedicine, energy or electronics that require synthetic dendronized cells or the adsorption and transport of charged species.
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Affiliation(s)
- Akash Banerjee
- Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey Piscataway NJ 08854 USA
| | - Acacia Tam
- Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey Piscataway NJ 08854 USA
| | - Meenakshi Dutt
- Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey Piscataway NJ 08854 USA
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Dufourc EJ. Bicelles and nanodiscs for biophysical chemistry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183478. [PMID: 32971065 DOI: 10.1016/j.bbamem.2020.183478] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 01/14/2023]
Abstract
Membrane nanoobjects are very important tools to study biomembrane properties. Two types are described herein: Bicelles and Nanodiscs. Bicelles are obtained by thorough water mixing of long chain and short chain lipids and may take the form of membranous discs of 10-50 nm. Temperature-composition-hydration diagrams have been established for Phosphatidylcholines and show limited domains of existence. Bicelles can be doped with charged lipids, surfactants or with cholesterol and offer a wide variety of membranous platforms for structural biology. Internal dynamics as measured by solid-state NMR is very similar to that of liposomes in their fluid phase. Because of the magnetic susceptibility anisotropy of the lipid chains, discs may be aligned along or perpendicular to the magnetic field. They may serve as weak orienting media to provide distance information in determining the 3D structure of soluble proteins. In different conditions they show strong orienting properties which may be used to study the 3D structure, topology and dynamics of membrane proteins. Lipid Bicelles with biphenyl chains or doped with lanthanides show long lasting remnant orientation after removing the magnetic field due to smectic-like properties. An alternative to pure lipid Bicelles is provided by nanodiscs where the half torus composed by short chain lipids is replaced by proteins. This renders the nano-objects less fragile as they can be used to stabilize membrane protein assemblies to be studied by electron microscopy. Internal dynamics is again similar to liposomes except that the phase transition is abolished, possibly due to lateral constrain imposed by the toroidal proteins limiting the disc size. Advantages and drawbacks of both nanoplatforms are discussed.
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Affiliation(s)
- Erick J Dufourc
- Institute of Chemistry and Biology of membranes and Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, Allée Geoffroy Saint Hilaire, 33600 Pessac, France.
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Shigematsu T, Koshiyama K, Wada S. Kelvin-Helmholtz-like instability of phospholipid bilayers under shear flow: System-size dependence. Phys Rev E 2020; 102:022408. [PMID: 32942508 DOI: 10.1103/physreve.102.022408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 08/03/2020] [Indexed: 11/07/2022]
Abstract
We performed a series of molecular dynamics (MD) simulations of phospholipid bilayers under shear flow to estimate the effect of the system size on Kelvin-Helmholtz (KH)-like instability of the bilayer at the molecular scale. To extend the estimation by the MD simulations to the microscale, we introduced linear stability analysis for the fluid-fluid interface consisting of a thin membrane. For both the MD simulations and theoretical model, the critical velocity difference across the bilayer, where instability occurs, decreased with increasing wavelength of the bilayer undulation λ, which corresponds to the system size. When λ was more than about ten times larger than the bilayer thickness, the critical velocity difference in the MD simulations was in quantitative agreement with that obtained by the theoretical model. This means that the theoretical model is applicable for the shear-induced KH-like instability of the bilayer for large λ. The theoretical model showed that the critical velocity difference for the KH-like instability was proportional to λ^{-3/2}. Based on these results, we discuss the implications of the shear-induced bilayer instability in the shear-induced cell damage observed in experiments.
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Affiliation(s)
- Taiki Shigematsu
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - Kenichiro Koshiyama
- Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima 770-8506, Japan
| | - Shigeo Wada
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
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Sarkis J, Vié V. Biomimetic Models to Investigate Membrane Biophysics Affecting Lipid-Protein Interaction. Front Bioeng Biotechnol 2020; 8:270. [PMID: 32373596 PMCID: PMC7179690 DOI: 10.3389/fbioe.2020.00270] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/16/2020] [Indexed: 12/16/2022] Open
Abstract
Biological membranes are highly dynamic in their ability to orchestrate vital mechanisms including cellular protection, organelle compartmentalization, cellular biomechanics, nutrient transport, molecular/enzymatic recognition, and membrane fusion. Controlling lipid composition of different membranes allows cells to regulate their membrane characteristics, thus modifying their physical properties to permit specific protein interactions and drive structural function (membrane deformation facilitates vesicle budding and fusion) and signal transduction. Yet, how lipids control protein structure and function is still poorly understood and needs systematic investigation. In this review, we explore different in vitro membrane models and summarize our current understanding of the interplay between membrane biophysical properties and lipid-protein interaction, taken as example few proteins involved in muscular activity (dystrophin), digestion and Legionella pneumophila effector protein DrrA. The monolayer model with its movable barriers aims to mimic any membrane deformation while surface pressure modulation imitates lipid packing and membrane curvature changes. It is frequently used to investigate peripheral protein binding to the lipid headgroups. Examples of how lipid lateral pressure modifies protein interaction and organization within the membrane are presented using various biophysical techniques. Interestingly, the shear elasticity and surface viscosity of the monolayer will increase upon specific protein(s) binding, supporting the importance of such mechanical link for membrane stability. The lipid bilayer models such as vesicles are not only used to investigate direct protein binding based on the lipid nature, but more importantly to assess how local membrane curvature (vesicles with different size) influence the binding properties of a protein. Also, supported lipid bilayer model has been used widely to characterize diffusion law of lipids within the bilayer and/or protein/biomolecule binding and diffusion on the membrane. These membrane models continue to elucidate important advances regarding the dynamic properties harmonizing lipid-protein interaction.
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Affiliation(s)
- Joe Sarkis
- Department of Cell Biology, Harvard Medical School and Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA, United States
- Univ Rennes, CNRS, IPR-UMR 6251, Rennes, France
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Suga K, Kitagawa K, Taguchi S, Okamoto Y, Umakoshi H. Evaluation of Molecular Ordering in Bicelle Bilayer Membranes Based on Induced Circular Dichroism Spectra. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:3242-3250. [PMID: 32163713 DOI: 10.1021/acs.langmuir.9b03710] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bicelles are submicrometer-sized disc-shaped molecular self-assemblies that can be obtained in aqueous solution by dispersing mixtures of certain amphiphiles. Although phospholipid bicelle and phospholipid vesicle assemblies adopt similar lipid bilayer structures, the differences in bilayer characteristics, especially physicochemical properties such as bilayer fluidity, are not clearly understood. Herein, we report the lipid ordering properties of bicelle bilayer membranes based on induced circular dichroism (ICD) and fluorescence polarization analyses using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. Bicelles were prepared by using 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), while pure DMPC vesicles and pure DHPC micelles were used as references. At temperatures below the phase transition temperature of DMPC, the bicelles showed lower membrane fluidities, whereas DHPC micelles showed higher membrane fluidity, suggesting no significant differences in bilayer fluidity between the bicelle and vesicle assemblies. The ICD signals of DPH were induced only when the membrane was in ordered (solid-ordered or ripple-gel) phases. In the bicelle systems, the ICD of DPH was more significant than that of the DMPC vesicle. The induced chirality of DPH was dependent on the chirality of the bilayer lipid. Compared to that of the DMPC/DHPC bicelle, the ICD of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/DHPC bicelle was higher, while that of the bovine sphingomyelin/DHPC bicelle was lower. Because the lipids are tightly packed in the ordered phase, the ICD intensity reflects the molecular ordering state of the lipids in the bicelle bilayer.
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Affiliation(s)
- Keishi Suga
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 5608531, Japan
| | - Kazuki Kitagawa
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 5608531, Japan
| | - Shogo Taguchi
- Department of Chemical Engineering and Materials Science, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 6712280, Japan
| | - Yukihiro Okamoto
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 5608531, Japan
| | - Hiroshi Umakoshi
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 5608531, Japan
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