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DiPasquale M, Marquardt D. Perceiving the functions of vitamin E through neutron and X-ray scattering. Adv Colloid Interface Sci 2024; 330:103189. [PMID: 38824717 DOI: 10.1016/j.cis.2024.103189] [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: 10/08/2023] [Revised: 05/14/2024] [Accepted: 05/17/2024] [Indexed: 06/04/2024]
Abstract
Take your vitamins, or don't? Vitamin E is one of the few lipophilic vitamins in the human diet and is considered an essential nutrient. Over the years it has proven to be a powerful antioxidant and is commercially used as such, but this association is far from linear in physiology. It is increasingly more likely that vitamin E has multiple legitimate biological roles. Here, we review past and current work using neutron and X-ray scattering to elucidate the influence of vitamin E on key features of model membranes that can translate to the biological function(s) of vitamin E. Although progress is being made, the hundred year-old mystery remains unsolved.
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Affiliation(s)
| | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada; Department of Physics, University of Windsor, Windsor, Ontario, Canada.
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2
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Biswas B, Shah D, Cox-Vázquez SJ, Vázquez RJ. Sensing cholesterol-induced rigidity in model membranes with time-resolved fluorescence spectroscopy and microscopy. J Mater Chem B 2024; 12:6570-6576. [PMID: 38899544 DOI: 10.1039/d4tb00872c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Here, we report the characterization of cholesterol levels on membrane fluidity with a twisted intramolecular charge transfer (TICT) membrane dye, namely DI-8-ANEPPS, using fluorescence lifetime techniques such as time-correlated single photon counting (TCSPC) and fluorescence lifetime imaging microscopy (FLIM). The characterized liposomes comprised a 3 : 1 ratio of POPC and POPG, respectively, 1% DI-8-ANEPPS, and increasing cholesterol levels from 0% to 50%. Fluorescence lifetime characterization revealed that increasing the cholesterol levels from 0% to 50% increases the fluorescence lifetime of DI-8-ANEPPS from 2.36 ns to 3.65 ns, a 55% increment. Such lengthening in the fluorescence lifetime is concomitant with reduced Stokes shifts and higher quantum yield, revealing that localized excitation (LE) dominates over TICT states with increased cholesterol levels. Fluorescence anisotropy measurements revealed a less isotropic environment in the membrane upon increasing cholesterol levels, suggesting a shift from liquid-disorder (Lα) to liquid-order (LO) upon adding cholesterol. Local electrostatic and dipole characterization experiments revealed that changes in the zeta-potential (ζ-potential) and transmembrane dipole potential (Ψd) induced by changes in cholesterol levels or the POPC : POPG ratio play a minimal role in the fluorescence lifetime outcome of DI-8-ANEPPS. Instead, these results indicate that the cholesterol's effect in restricting the degree of movement of DI-8-ANEPPS dominates its photophysics over the cholesterol effect on the local dipole strength. We envision that time-resolved spectroscopy and microscopy, coupled with TICT dyes, could be a convenient tool in exploring the complex interplay between membrane lipids, sterols, and proteins and provide novel insights into membrane fluidity, organization, and function.
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Affiliation(s)
- Bidisha Biswas
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
| | - Dhari Shah
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
| | - Sarah J Cox-Vázquez
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
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3
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Hamada T, Mizuno S, Kitahata H. Shear-Induced Nonequilibrium Patterns in Lipid Bilayer Membranes Exhibiting Phase Separation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:8843-8850. [PMID: 38634601 DOI: 10.1021/acs.langmuir.3c03970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/19/2024]
Abstract
The nonequilibrium dynamics of a fluid lipid membrane under external stimuli is an important issue that spans disciplines such as soft matter, biophysical chemistry, and interface science. This study investigated the dynamic response of lipid vesicles with order-disorder phase separation, which mimics a plasma membrane heterogeneity, to shear flow. Lipid vesicles were immobilized in a microfluidic chamber, and shear-induced nonequilibrium patterns on the membrane surface were observed by an optical microscope. We found that phase-separated membranes exhibit a dissipative structure of stripe patterns along the vortex flow on the membrane surface, and the number of stripes increased with the flow rate. At a high flow rate, the membrane exhibited a stripe-to-wave transition, where striped domains often migrated and the replacement of two different phases happened at vortex centers with time. We obtained a dynamic phase diagram of the shear-induced wave pattern by changing the flow rate, membrane components, and temperature. These findings could provide insight into the dissipative structures of lipid membranes out of equilibrium and flow-mediated mechanotransduction of biological membranes.
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Affiliation(s)
- Tsutomu Hamada
- School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi City, Ishikawa 923-1292, Japan
| | - Shino Mizuno
- School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi City, Ishikawa 923-1292, Japan
| | - Hiroyuki Kitahata
- Department of Physics, Graduate School of Science, Chiba University, Chiba 263-8522, Japan
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4
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Kashnik AS, Baranov DS, Dzuba SA. Spatial Arrangement of the Drug Ibuprofen in a Model Membrane in the Presence of Lipid Rafts. J Phys Chem B 2024; 128:3652-3661. [PMID: 38576273 DOI: 10.1021/acs.jpcb.4c01507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Many pharmaceutical drugs are known to interact with lipid membranes through nonspecific molecular interactions, which affect their therapeutic effect. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) and one of the most commonly prescribed. In the presence of cholesterol, lipid bilayers can separate into nanoscale liquid-disordered and liquid-ordered structures, the latter known as lipid rafts. Here, we study spin-labeled ibuprofen (ibuprofen-SL) in the model membrane consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol in the molar ratio of (0.5-0.5xchol)/(0.5-0.5xchol)/xchol. Electron paramagnetic resonance (EPR) spectroscopy is employed, along with its pulsed version of double electron-electron resonance (DEER, also known as PELDOR). The data obtained indicate lateral lipid-mediated clustering of ibuprofen-SL molecules with a local surface density noticeably larger than that expected for random lateral distribution. In the absence of cholesterol, the data can be interpreted as indicating alternating clustering in two opposing leaflets of the bilayer. In the presence of cholesterol, for xchol ≥ 20 mol %, the results show that ibuprofen-SL molecules have a quasi-regular lateral distribution, with a "superlattice" parameter of ∼3.0 nm. This regularity can be explained by the entrapment of ibuprofen-SL molecules by lipid rafts known to exist in this system with the additional assumption that lipid rafts have a nanoscale substructure.
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Affiliation(s)
- Anna S Kashnik
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Denis S Baranov
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Sergei A Dzuba
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
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5
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Park S, Pastor RW, Im W. Binary bilayer simulations for partitioning within membranes. Methods Enzymol 2024; 701:123-156. [PMID: 39025570 DOI: 10.1016/bs.mie.2024.03.007] [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] [Indexed: 07/20/2024]
Abstract
Membrane proteins (MPs) often show preference for one phase over the other, which is characterized by the partition coefficient, Kp. The physical mechanisms underlying Kp have been only inferred indirectly from experiments due to the unavailability of detailed structures and compositions of ordered phases. Molecular dynamics (MD) simulations can complement these details and thus, in principle, provide further insights into the partitioning of MPs between two phases. However, the application of MD has remained difficult due to long time scales required for equilibration and large system size for the phase stability, which have not been fully resolved even in free energy simulations. This chapter describes the recently developed binary bilayer simulation method, where the membrane is composed of two laterally attached membrane patches. The binary bilayer system (BBS) is designed to preserve the lateral packing of both phases in a significantly smaller size compared to that required for macroscopic phase separation. These characteristics are advantageous in partitioning simulations, as the length scale for diffusion across the system can be significantly smaller. Hence the BBS can be efficiently employed in both conventional MD and free energy simulations, though sampling in ordered phases remains difficult due to slow diffusion. Development of efficient lipid swapping methods and its combination with the BBS would be a useful approach for partitioning in coexisting phases.
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Affiliation(s)
- Soohyung Park
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, PA, United States
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - Wonpil Im
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, PA, United States.
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Collier CP, Bolmatov D, Elkins JG, Katsaras J. Nanoscopic lipid domains determined by microscopy and neutron scattering. Methods 2024; 223:127-135. [PMID: 38331125 DOI: 10.1016/j.ymeth.2024.01.020] [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: 11/07/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 02/10/2024] Open
Abstract
Biological membranes are highly complex supramolecular assemblies, which play central roles in biology. However, their complexity makes them challenging to study their nanoscale structures. To overcome this challenge, model membranes assembled using reduced sets of membrane-associated biomolecules have been found to be both excellent and tractable proxies for biological membranes. Due to their relative simplicity, they have been studied using a range of biophysical characterization techniques. In this review article, we will briefly detail the use of fluorescence and electron microscopies, and X-ray and neutron scattering techniques used over the past few decades to study the nanostructure of biological membranes.
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Affiliation(s)
- Charles P Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Dima Bolmatov
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - James G Elkins
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - John Katsaras
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Neutron Scattering Division, Oak Ridge National Laboratorry, Oak Ridege, TN, USA
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7
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Dali P, Shende P. Interdigitation of lipids for vesosomal formulation of ergotamine tartrate with caffeine: a futuristic trend of intranasal route. Drug Dev Ind Pharm 2024; 50:124-134. [PMID: 38158799 DOI: 10.1080/03639045.2023.2301018] [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: 04/28/2023] [Accepted: 12/27/2023] [Indexed: 01/03/2024]
Abstract
OBJECTIVE This research work aimed to form vesosomes using combination of two drugs ergotamine (ERG) and caffeine for synergistic activity when given intranasally resulting in faster absorption, steric stability, and controlled release. SIGNIFICANCE The multicompartment vesicles viz., vesosomes of ERG tartrate proved to increase absorption of drugs post-intranasal administration, bypassing the blood-brain barrier via the olfactory pathway. METHODS The phospholipids like soya lecithin, cholesterol, and dipalmitoyl phosphatidylcholine (DPPC) were used to form a multicompartment structure called vesosomes using ethanol-induced interdigitation of lipids as the preparation method. RESULTS The formulation showed low particle size (PS) of 315.48 ± 14.27 nm with zeta potential (ZP) of -21.78 ± 4.72 mV, higher % EE of 91.13 ± 1.29%, and controlled release kinetics, when assessed for in-vitro and ex-vivo studies as 97.64 ± 5.13% and 82.25 ± 3.27% release, respectively. Vesosomes displayed several advantages over liposomes like improved stability against phospholipase-induced enzymatic degradation and higher brain uptake 3.41-fold increase of ERG via the olfactory pathway. CONCLUSIONS The stable vesosomes prepared using interdigitation of saturated phospholipids proved to be a viable option for ERG when administered intranasally for better absorption and bioavailability coupled with ease of administration gaining wider patient acceptance.
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Affiliation(s)
- Preeti Dali
- Shobhaben Pratapbhai Patel School of Pharmacy and Technology Management, SVKM's NMIMS, Mumbai, India
| | - Pravin Shende
- Shobhaben Pratapbhai Patel School of Pharmacy and Technology Management, SVKM's NMIMS, Mumbai, India
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8
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Semenenko OM, Lipson VV, Sadchenko AO, Vashchenko OV, Kasian NA, Sviechnikova LV, Lisetski LM, Babak ML, Vakula VM, Borysov OV, Holota YV, Zozulya SO, Borysko PO, Mazepa OV. Synthesis of methotrexate-betulonic acid hybrids and evaluation of their effect on artificial and Caco-2 cell membranes. Steroids 2024; 201:109332. [PMID: 37939980 DOI: 10.1016/j.steroids.2023.109332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 11/03/2023] [Accepted: 11/05/2023] [Indexed: 11/10/2023]
Abstract
An efficient protocol for the synthesis of novel methotrexate-betulonic acid hybrids with a (tert-butoxycarbonylamino)-3,6-dioxa-8-octanamine (Boc-DOOA) linkage has been developed. Reaction of N-(2-(2-(2-aminoethoxy)ethoxy)ethyl)-betulonamide with methotrexate resulted in a mixture of isomeric conjugates which were separated by column chromatography. Their structures and composition have been fully established by 1H NMR, 13C spectra, FAB mass spectrometry and elemental analysis. The identity of conjugates was confirmed by LC-MS data. Membranotropic properties of the new hybrids were assessed on the basis of their interactions with artificial lipid membranes by differential scanning calorimetry (DSC) method. The ability of the conjugates to penetrate Caco-2 cells is inferior to methotrexate. Probably, this is due to the increasing lipophilicity, the affinity of these hybrid molecules for the lipid bilayer increases, which is confirmed by experiments with artificial membranes.
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Affiliation(s)
- Olexander M Semenenko
- Department of Organic and Bioorganic Chemistry, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Victoria V Lipson
- Department of Organic and Bioorganic Chemistry, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine; Medicinal Chemistry Department, State Institution "V.Ya. Danilevsky Institute for Endocrine Pathology Problems" NAMS of Ukraine, Alchevskih St., 10, 61002 Kharkiv, Ukraine; Organic Chemistry Department, V.N. Karazin Kharkiv National University, Svobody Sq., 4, 61022 Kharkiv, Ukraine.
| | - Alina O Sadchenko
- Institute for Scintillation Materials, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Olga V Vashchenko
- Institute for Scintillation Materials, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Natalia A Kasian
- Institute for Scintillation Materials, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Liliia V Sviechnikova
- Institute for Scintillation Materials, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Longin M Lisetski
- Institute for Scintillation Materials, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Mykola L Babak
- Department of Organic and Bioorganic Chemistry, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine
| | - Volodymyr M Vakula
- Department of Organic and Bioorganic Chemistry, State Scientific Institution "Institute for Single Crystals" NAS of Ukraine, Nauky Ave., 60, 61072 Kharkiv, Ukraine; Medicinal Chemistry Department, State Institution "V.Ya. Danilevsky Institute for Endocrine Pathology Problems" NAMS of Ukraine, Alchevskih St., 10, 61002 Kharkiv, Ukraine
| | | | | | | | | | - Olexander V Mazepa
- A. V. Bogatsky Physico-Chemical Institute NAS of Ukraine, Lustdorfska Road, 86, 65080 Odesa, Ukraine
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9
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Sut TN, Jackman JA, Cho NJ. Cholesterol-Enriched Hybrid Lipid Bilayer Formation on Inverse Phosphocholine Lipid-Functionalized Titanium Oxide Surfaces. Biomimetics (Basel) 2023; 8:588. [PMID: 38132527 PMCID: PMC10741646 DOI: 10.3390/biomimetics8080588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/29/2023] [Accepted: 12/02/2023] [Indexed: 12/23/2023] Open
Abstract
Hybrid lipid bilayers (HLBs) are rugged biomimetic cell membrane interfaces that can form on inorganic surfaces and be designed to contain biologically important components like cholesterol. In general, HLBs are formed by depositing phospholipids on top of a hydrophobic self-assembled monolayer (SAM) composed of one-tail amphiphiles, while recent findings have shown that two-tail amphiphiles such as inverse phosphocholine (CP) lipids can have advantageous properties to promote zwitterionic HLB formation. Herein, we explored the feasibility of fabricating cholesterol-enriched HLBs on CP SAM-functionalized TiO2 surfaces with the solvent exchange and vesicle fusion methods. All stages of the HLB fabrication process were tracked by quartz crystal microbalance-dissipation (QCM-D) measurements and revealed important differences in fabrication outcome depending on the chosen method. With the solvent exchange method, it was possible to fabricate HLBs with well-controlled cholesterol fractions up to ~65 mol% in the upper leaflet as confirmed by a methyl-β-cyclodextrin (MβCD) extraction assay. In marked contrast, the vesicle fusion method was only effective at forming HLBs from precursor vesicles containing up to ~35 mol% cholesterol, but this performance was still superior to past results on hydrophilic SiO2. We discuss the contributing factors to the different efficiencies of the two methods as well as the general utility of two-tail CP SAMs as favorable interfaces to incorporate cholesterol into HLBs. Accordingly, our findings support that the solvent exchange method is a versatile tool to fabricate cholesterol-enriched HLBs on CP SAM-functionalized TiO2 surfaces.
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Affiliation(s)
- Tun Naw Sut
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;
- School of Chemical Engineering and Translational Nanobioscience Research Center, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Joshua A. Jackman
- School of Chemical Engineering and Translational Nanobioscience Research Center, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;
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10
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Schütz GJ, Pabst G. The asymmetric plasma membrane-A composite material combining different functionalities?: Balancing Barrier Function and Fluidity for Effective Signaling. Bioessays 2023; 45:e2300116. [PMID: 37712937 DOI: 10.1002/bies.202300116] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 08/31/2023] [Accepted: 09/06/2023] [Indexed: 09/16/2023]
Abstract
One persistent puzzle in the life sciences is the asymmetric lipid composition of the cellular plasma membrane: while the exoplasmic leaflet is enriched in lipids carrying predominantly saturated fatty acids, the cytoplasmic leaflet hosts preferentially lipids with (poly-)unsaturated fatty acids. Given the high energy requirements necessary for cells to maintain this asymmetry, the question naturally arises regarding its inherent benefits. In this paper, we propose asymmetry to represent a potential solution for harmonizing two conflicting requirements for the plasma membrane: first, the need to build a barrier for the uncontrolled influx or efflux of substances; and second, the need to form a fluid and dynamic two-dimensional substrate for signaling processes. We hence view here the plasma membrane as a composite material, where the exoplasmic leaflet is mainly responsible for the functional integrity of the barrier and the cytoplasmic leaflet for fluidity. We reinforce the validity of the proposed mechanism by presenting quantitative data from the literature, along with multiple examples that bolster our model.
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Affiliation(s)
| | - Georg Pabst
- Biophysics, Institute of Molecular Bioscience (IMB), NAWI Graz, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth-University of Graz, Graz, Austria
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11
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Ramirez JM, Calderon-Zavala AC, Balaram A, Heldwein EE. In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger. mBio 2023; 14:e0208723. [PMID: 37874146 PMCID: PMC10746285 DOI: 10.1128/mbio.02087-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 09/11/2023] [Indexed: 10/25/2023] Open
Abstract
Membrane fusion mediated by herpes simplex virus 1 (HSV-1) is a complex, multi-protein process that is receptor triggered and can occur both at the cell surface and in endosomes. To deconvolute this complexity, we reconstituted HSV-1 fusion with synthetic lipid vesicles in vitro. Using this simplified, controllable system, we discovered that HSV-1 fusion required not only a cognate host receptor but also low pH. On the target membrane side, efficient fusion required cholesterol, negatively charged lipids found in the endosomal membranes, and an optimal balance of lipid order and disorder. On the virion side, the four HSV-1 entry glycoproteins-gB, gD, gH, and gL-were sufficient for fusion. We propose that low pH is a biologically relevant co-trigger for HSV-1 fusion. The dependence of fusion on low pH and endosomal lipids could explain why HSV-1 enters most cell types by endocytosis. We hypothesize that under neutral pH conditions, other, yet undefined, cellular factors may serve as fusion co-triggers. The in vitro fusion system established here can be employed to systematically investigate HSV-1-mediated membrane fusion.IMPORTANCEHSV-1 causes lifelong, incurable infections and diseases ranging from mucocutaneous lesions to fatal encephalitis. Fusion of viral and host membranes is a critical step in HSV-1 infection of target cells that requires multiple factors on both the viral and host sides. Due to this complexity, many fundamental questions remain unanswered, such as the identity of the viral and host factors that are necessary and sufficient for HSV-1-mediated membrane fusion and the nature of the fusion trigger. Here, we developed a simplified in vitro fusion assay to examine the fusion requirements and identified low pH as a co-trigger for virus-mediated fusion in vitro. We hypothesize that low pH has a critical role in cell entry and, potentially, pathogenesis.
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Affiliation(s)
- J. Martin Ramirez
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariana C. Calderon-Zavala
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariane Balaram
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
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12
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Sarkar T, Farago O. Characterizing the heterogeneity of membrane liquid-ordered domains. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:99. [PMID: 37847322 DOI: 10.1140/epje/s10189-023-00359-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 09/27/2023] [Indexed: 10/18/2023]
Abstract
We use a lattice model of a ternary mixture containing saturated and unsaturated lipids with cholesterol (Chol), to study the structural properties characterizing the coexistence between the liquid-disordered and liquid-ordered phases. Depending on the affinity of the saturated and unsaturated lipids, the system may exhibit macroscopic (thermodynamic) liquid-liquid phase separation or be divided into small-size liquid-ordered domains surrounded by a liquid-disordered matrix. In both cases, it is found that the nanoscale structure of the liquid-ordered regions is heterogeneous, and that they are partitioned into Chol-rich sub-domains and Chol-free, gel-like, nano-clusters. This emerges as a characteristic feature of the liquid-ordered state, which helps distinguishing between liquid-ordered domains in a two-phase mixture, and similar-looking domains in a one-phase mixture that are rich in saturated lipids and Chol, but are merely thermal density fluctuations. The nano-structure heterogeneity of the liquid-ordered phase can be detected by suitable experimental spectroscopic methods and is observed also in atomistic computer simulations.
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Affiliation(s)
- Tanmoy Sarkar
- Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
| | - Oded Farago
- Biomedical Engineering Department, Ben Gurion University of the Negev, 84105, Beer Sheva, Israel.
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13
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Park S, Levental I, Pastor RW, Im W. Unsaturated Lipids Facilitate Partitioning of Transmembrane Peptides into the Liquid Ordered Phase. J Chem Theory Comput 2023; 19:5303-5314. [PMID: 37417947 PMCID: PMC10413867 DOI: 10.1021/acs.jctc.3c00398] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Indexed: 07/08/2023]
Abstract
The affinity of single-pass transmembrane (TM) proteins for ordered membrane phases has been reported to depend on their lipidation, TM length, and lipid accessible surface area. In this work, the raft affinities of the TM domain of the linker for activation of T cells and its depalmitoylated variant are assessed using free energy simulations in a binary bilayer system composed of two laterally patched bilayers of ternary liquid ordered (Lo) and liquid disordered (Ld) phases. These phases are modeled by distinct compositions of distearoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine (POPC), and cholesterol, and the simulations were carried out for 4.5 μs/window. Both peptides are shown to preferentially partition into the Ld phase in agreement with model membrane experiments and previous simulations on ternary lipid mixtures but not with measurements on giant plasma membrane vesicles where the Lo is slightly preferred. However, the 500 ns average relaxation time of lipid rearrangement around the peptide precluded a quantitative analysis of free energy differences arising from peptide palmitoylation and two different lipid compositions. When in the Lo phase, peptides reside in regions rich in POPC and interact preferentially with its unsaturated tail. Hence, the detailed substructure of the Lo phase is an important modulator of peptide partitioning, in addition to the inherent properties of the peptide.
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Affiliation(s)
- Soohyung Park
- Departments
of Biological Sciences and Chemistry, Lehigh
University, Bethlehem, Pennsylvania 18015, United States
| | - Ilya Levental
- Department
of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22903-1738, United States
| | - Richard W. Pastor
- Laboratory
of Computational Biology, National Heart,
Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Wonpil Im
- Departments
of Biological Sciences and Chemistry, Lehigh
University, Bethlehem, Pennsylvania 18015, United States
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14
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Tripathy M, Srivastava A. Lipid packing in biological membranes governs protein localization and membrane permeability. Biophys J 2023; 122:2727-2743. [PMID: 37254482 PMCID: PMC10397809 DOI: 10.1016/j.bpj.2023.05.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/18/2023] [Accepted: 05/25/2023] [Indexed: 06/01/2023] Open
Abstract
Plasma membrane (PM) heterogeneity has long been implicated in various cellular functions. However, mechanistic principles governing functional regulations of lipid environment are not well understood due to the inherent complexities associated with the relevant length and timescales that limit both direct experimental measurements and their interpretation. In this context, computer simulations hold immense potential to investigate molecular-level interactions and mechanisms that lead to PM heterogeneity and its functions. Herein, we investigate spatial and dynamic heterogeneity in model membranes with coexisting liquid ordered and liquid disordered phases and characterize the membrane order in terms of the local topological changes in lipid environment using the nonaffine deformation framework. Furthermore, we probe the packing defects in these membranes, which can be considered as the conjugate of membrane order assessed in terms of the nonaffine parameter. In doing so, we formalize the connection between membrane packing and local membrane order and use that to explore the mechanistic principles behind their functions. Our observations suggest that heterogeneity in mixed phase membranes is a consequence of local lipid topology and its temporal evolution, which give rise to disparate lipid packing in ordered and disordered domains. This in turn governs the distinct nature of packing defects in these domains that can play a crucial role in preferential localization of proteins in mixed phase membranes. Furthermore, we observe that lipid packing also leads to contrasting distribution of free volume in the membrane core region in ordered and disordered membranes, which can lead to distinctive membrane permeability of small molecules. Our results, thus, indicate that heterogeneity in mixed phase membranes closely governs the membrane functions that may emerge from packing-related basic design principles.
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Affiliation(s)
- Madhusmita Tripathy
- Molecular Biophysics Unit, Indian Institute of Science Bangalore, Bangalore, Karnataka, India.
| | - Anand Srivastava
- Molecular Biophysics Unit, Indian Institute of Science Bangalore, Bangalore, Karnataka, India.
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15
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Polita A, Stancikaitė M, Žvirblis R, Maleckaitė K, Dodonova-Vaitkūnienė J, Tumkevičius S, Shivabalan AP, Valinčius G. Designing a green-emitting viscosity-sensitive 4,4-difluoro-4-bora-3a,4a-diaza- s-indacene (BODIPY) probe for plasma membrane viscosity imaging. RSC Adv 2023; 13:19257-19264. [PMID: 37377877 PMCID: PMC10291278 DOI: 10.1039/d3ra04126c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 06/29/2023] Open
Abstract
Viscosity is a key characteristic of lipid membranes - it governs the passive diffusion of solutes and affects the lipid raft formation and membrane fluidity. Precise determination of viscosity values in biological systems is of great interest and viscosity-sensitive fluorescent probes offer a convenient solution for this task. In this work we present a novel membrane-targeting and water-soluble viscosity probe BODIPY-PM, which is based on one of the most frequently used probes BODIPY-C10. Despite its regular use, BODIPY-C10 suffers from poor integration into liquid-ordered lipid phases and lack of water solubility. Here, we investigate the photophysical characteristics of BODIPY-PM and demonstrate that solvent polarity only slightly affects the viscosity-sensing qualities of BODIPY-PM. In addition, with fluorescence lifetime imaging microscopy (FLIM), we imaged microviscosity in complex biological systems - large unilamellar vesicles (LUVs), tethered bilayer membranes (tBLMs) and live lung cancer cells. Our study showcases that BODIPY-PM preferentially stains the plasma membranes of live cells, equally well partitions into both liquid-ordered and liquid-disordered phases and reliably distinguishes lipid phase separation in tBLMs and LUVs.
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Affiliation(s)
- Artūras Polita
- Institute of Biochemistry, Life Sciences Center, Vilnius University Saulėtekio Av. 7 Vilnius LT-10257 Lithuania
| | - Milda Stancikaitė
- Center of Physical Sciences and Technology Saulėtekio Av. 3 Vilnius LT-10257 Lithuania
| | - Rokas Žvirblis
- Life Sciences Center, Institute of Biotechnology, Vilnius University Saulėtekio Av. 7 Vilnius LT-10257 Lithuania
| | - Karolina Maleckaitė
- Center of Physical Sciences and Technology Saulėtekio Av. 3 Vilnius LT-10257 Lithuania
| | - Jelena Dodonova-Vaitkūnienė
- Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University Naugarduko St. 24 Vilnius LT-03225 Lithuania
| | - Sigitas Tumkevičius
- Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University Naugarduko St. 24 Vilnius LT-03225 Lithuania
| | - Arun Prabha Shivabalan
- Institute of Biochemistry, Life Sciences Center, Vilnius University Saulėtekio Av. 7 Vilnius LT-10257 Lithuania
| | - Gintaras Valinčius
- Institute of Biochemistry, Life Sciences Center, Vilnius University Saulėtekio Av. 7 Vilnius LT-10257 Lithuania
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16
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Aghaaminiha M, Farnoud AM, Sharma S. Interdependence of cholesterol distribution and conformational order in lipid bilayers. Biointerphases 2023; 18:2887740. [PMID: 37125848 DOI: 10.1116/6.0002489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 04/11/2023] [Indexed: 05/02/2023] Open
Abstract
We show, via molecular simulations, that not only does cholesterol induce a lipid order, but the lipid order also enhances cholesterol localization within the lipid leaflets. Therefore, there is a strong interdependence between these two phenomena. In the ordered phase, cholesterol molecules are predominantly present in the bilayer leaflets and orient themselves parallel to the bilayer normal. In the disordered phase, cholesterol molecules are mainly present near the center of the bilayer at the midplane region and are oriented orthogonal to the bilayer normal. At the melting temperature of the lipid bilayers, cholesterol concentration in the leaflets and the bilayer midplane is equal. This result suggests that the localization of cholesterol in the lipid bilayers is mainly dictated by the degree of ordering of the lipid bilayer. We validate our findings on 18 different lipid bilayer systems, obtained from three different phospholipid bilayers with varying concentrations of cholesterol. To cover a large temperature range in simulations, we employ the Dry Martini force field. We demonstrate that the Dry and the Wet Martini (with polarizable water) force fields produce comparable results.
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Affiliation(s)
| | - Amir M Farnoud
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio 45701
| | - Sumit Sharma
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio 45701
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17
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Feng S, Park S, Choi YK, Im W. CHARMM-GUI Membrane Builder: Past, Current, and Future Developments and Applications. J Chem Theory Comput 2023; 19:2161-2185. [PMID: 37014931 PMCID: PMC10174225 DOI: 10.1021/acs.jctc.2c01246] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2023]
Abstract
Molecular dynamics simulations of membranes and membrane proteins serve as computational microscopes, revealing coordinated events at the membrane interface. As G protein-coupled receptors, ion channels, transporters, and membrane-bound enzymes are important drug targets, understanding their drug binding and action mechanisms in a realistic membrane becomes critical. Advances in materials science and physical chemistry further demand an atomistic understanding of lipid domains and interactions between materials and membranes. Despite a wide range of membrane simulation studies, generating a complex membrane assembly remains challenging. Here, we review the capability of CHARMM-GUI Membrane Builder in the context of emerging research demands, as well as the application examples from the CHARMM-GUI user community, including membrane biophysics, membrane protein drug-binding and dynamics, protein-lipid interactions, and nano-bio interface. We also provide our perspective on future Membrane Builder development.
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Affiliation(s)
- Shasha Feng
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Soohyung Park
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Yeol Kyo Choi
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Wonpil Im
- Departments of Biological Sciences and Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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18
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Sarkar T, Farago O. A lattice model of ternary mixtures of lipids and cholesterol with tunable domain sizes. SOFT MATTER 2023; 19:2417-2429. [PMID: 36930060 DOI: 10.1039/d2sm01025a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Much of our understanding of the physical properties of raft domains in biological membranes, and some insight into the mechanisms underlying their formation stem from atomistic simulations of simple model systems, especially ternary mixtures consisting of saturated and unsaturated lipids, and cholesterol (Chol). To explore the properties of such systems at large spatial scales, we here present a simple ternary mixture lattice model, involving a small number of nearest neighbor interaction terms. Monte Carlo simulations of mixtures with different compositions show excellent agreement with experimental and atomistic simulation observations across multiple scales, ranging from the local distributions of lipids to the phase diagram of the system. The simplicity of the model allows us to identify the roles played by the different interactions between components, and the interplay between them. Importantly, by changing the value of one of the model parameters, we can tune the size of the liquid-ordered domains, thereby simulating both Type II mixtures exhibiting macroscopic phase separation and Type I mixtures with nanoscopic domains. The Type II mixture simulation results fit well to the experimentally determined phase diagram of mixtures containing saturated DPPC/unsaturated DOPC/Chol. When the tunable parameter is changed, we obtain the Type I version of DPPC/DOPC/Chol, i.e., a mixture not showing thermodynamic phase transitions but one that may be fitted to the same phase diagram if local measures are used to distinguish between the different states. Our model results suggest that short range packing is likely to be a key regulator of the stability and size distribution of biological rafts.
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Affiliation(s)
- Tanmoy Sarkar
- Department of Biomedical Engineering, Ben Gurion University of the Negev, Be'er Sheva 84105, Israel.
| | - Oded Farago
- Department of Biomedical Engineering, Ben Gurion University of the Negev, Be'er Sheva 84105, Israel.
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19
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Ho TH, Nguyen TT, Huynh LK. Formation of lipid raft nanodomains in homogeneous ternary lipid mixture of POPC/DPSM/cholesterol: Theoretical insights. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184027. [PMID: 35995208 DOI: 10.1016/j.bbamem.2022.184027] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/16/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
Lipid rafts, in biological membranes, are cholesterol-rich nanodomains that regulate many protein activities and cellular processes. Understanding the formation of the lipid-raft nanodomains helps us elucidate many complex interactions in the cell. In this study, the formation of lipid-raft nanodomains in a ternary palmitoyl-oleoyl-phosphatidylcholine/stearoyl-sphingomyelin/cholesterol (POPC/DPSM/Chol) lipid mixture, the most realistic surrogate model for biological membranes, has been successfully observed for the first time in-silico using microsecond timescale molecular dynamics simulations. The model reveals the formation of cholesterol-induced nanodomains with raft-like characteristics and their underlying mechanism: the cholesterol molecules segregate themselves into cholesterol nanodomains and then enrich the cholesterol-rich domain with sphingomyelin molecules to form a lipid raft thanks to the weak bonding of cholesterol with sphingomyelin. Besides, it is found that the increase in cholesterol concentration enhances the biophysical properties (e.g., bilayer thickness, area per lipid headgroup, and order parameter) of the lipid raft nanodomains. Such findings suggest that the POPC/DPSM/Chol bilayer is a suitable model to fundamentally extend the nanodomain evolution to investigate their lifetime and kinetics as well as to study protein-lipid interaction, protein-protein interaction, and selection of therapeutic molecules in the presence of lipid rafts.
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Affiliation(s)
- Tho H Ho
- Vietnam National University, Ho Chi Minh, Vietnam; Chemical Engineering Department, School of Biotechnology, International University, Quarter 6, Linh Trung Ward, Thu Duc City, Ho Chi Minh City 700000, Vietnam
| | - Trang T Nguyen
- Vietnam National University, Ho Chi Minh, Vietnam; Chemical Engineering Department, School of Biotechnology, International University, Quarter 6, Linh Trung Ward, Thu Duc City, Ho Chi Minh City 700000, Vietnam.
| | - Lam K Huynh
- Vietnam National University, Ho Chi Minh, Vietnam; Chemical Engineering Department, School of Biotechnology, International University, Quarter 6, Linh Trung Ward, Thu Duc City, Ho Chi Minh City 700000, Vietnam.
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20
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Heterogeneity and deformation behavior of lipid vesicles. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2022.101646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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21
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Zaytseva YV, Zaytseva IV, Surovtsev NV. Conformational state diagram of DOPC/DPPC d62/cholesterol mixtures. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183869. [PMID: 35063400 DOI: 10.1016/j.bbamem.2022.183869] [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: 11/18/2021] [Revised: 01/09/2022] [Accepted: 01/12/2022] [Indexed: 06/14/2023]
Abstract
Raman spectra of aqueous suspensions of vesicles composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), deuterated 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (DPPCd62), and cholesterol (Chol) were studied at room temperature to determine the conformational states of the phospholipid hydrocarbon chains. Deuteration of DPPCd62 allowed us to characterize the conformational states of DOPC and DPPCd62 independently. The parameters of Raman peaks, which are sensitive to the conformational order, were studied in a wide range of compositions. It was found that the DOPC molecules are conformationally disordered for all compositions. The conformational state of the DPPCd62 molecules changes with composition. Their conformational state is influenced by cholesterol-induced partial disordering and DOPC solvation, transforming the DPPC molecules into the disordered state. The conformational state diagram from the Raman experiment was compared with outcomes from the differential scanning calorimetry (DSC) experiment. The Raman spectra also revealed that the DPPC molecules coexist in the disordered and all-trans ordered states for the DOPC/DPPCd62/Chol mixtures except for the pure liquid-disordered phase.
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Affiliation(s)
- Yu V Zaytseva
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - I V Zaytseva
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - N V Surovtsev
- Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk 630090, Russia.
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22
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Identifying Membrane Lateral Organization by Contrast-Matched Small Angle Neutron Scattering. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2022; 2402:163-177. [PMID: 34854044 DOI: 10.1007/978-1-0716-1843-1_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Lipid domains in model membranes are routinely studied to provide insight into the physical interactions that drive raft formation in cellular membranes. Using small angle neutron scattering, contrast-matching techniques enable the detection of lipid domains ranging from tens to hundreds of nanometers which are not accessible to other techniques without the use of extrinsic probes. Here, we describe a probe-free experimental approach and model-free analysis to identify lipid domains in freely floating vesicles of ternary phase separating lipid mixtures.
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23
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Hitaishi P, Mandal P, Ghosh SK. Partitioning of a Hybrid Lipid in Domains of Saturated and Unsaturated Lipids in a Model Cellular Membrane. ACS OMEGA 2021; 6:34546-34554. [PMID: 34963939 PMCID: PMC8697375 DOI: 10.1021/acsomega.1c04835] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
The cellular membranes are composed of hundreds of components such as lipids, proteins, and sterols that are chemically and physically distinct from each other. The lipid-lipid and lipid-protein interactions form domains in this membrane, which play vital roles in membrane physiology. The hybrid lipids (HLs) with one saturated and one unsaturated chain can control the shape and size of these domains, ensuring the thermodynamic stability of a membrane. In this study, the thermodynamics of mixing of a HL and its structural effects on the phase separated domains in a model membrane composed of a saturated and an unsaturated lipid have been investigated. The HL is observed to mix into an unsaturated lipid reducing the Gibbs free energy, whereas the mixing is unfavorable in a saturated lipid. The presence of an HL in an unsaturated lipid tends to increase its area fraction, which is reflected in the enhanced correlation length across the bilayers in a multilayered sample. There is a feeble effect on the domain structure of the saturated lipid due to the presence of the HLs at the phase boundary. This study concludes that the HLs preferentially participate in the unsaturated lipid regions compared to that of a saturated lipid.
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24
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Tran N, Oh Y, Sutherland M, Cui Q, Hong M. Cholesterol-Mediated Clustering of the HIV Fusion Protein gp41 in Lipid Bilayers. J Mol Biol 2021; 434:167345. [PMID: 34762895 DOI: 10.1016/j.jmb.2021.167345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 10/26/2021] [Accepted: 10/31/2021] [Indexed: 11/16/2022]
Abstract
The envelope glycoprotein (Env) of the human immunodeficient virus (HIV-1) is known to cluster on the viral membrane surface to attach to target cells and cause membrane fusion for HIV-1 infection. However, the molecular structural mechanisms that drive Env clustering remain opaque. Here, we use solid-state NMR spectroscopy and molecular dynamics (MD) simulations to investigate nanometer-scale clustering of the membrane-proximal external region (MPER) and transmembrane domain (TMD) of gp41, the fusion protein component of Env. Using 19F solid-state NMR experiments of mixed fluorinated peptides, we show that MPER-TMD trimers form clusters with interdigitated MPER helices in cholesterol-containing membranes. Inter-trimer 19F-19F cross peaks, which are indicative of spatial contacts within ∼2 nm, are observed in cholesterol-rich virus-mimetic membranes but are suppressed in cholesterol-free model membranes. Water-peptide and lipid-peptide cross peaks in 2D 1H-19F correlation spectra indicate that the MPER is well embedded in model phosphocholine membranes but is more exposed to the surface of the virus-mimetic membrane. These experimental results are reproduced in coarse-grained and atomistic molecular dynamics simulations, which suggest that the effects of cholesterol on gp41 clustering is likely via indirect modulation of the MPER orientation. Cholesterol binding to the helix-turn-helix region of the MPER-TMD causes a parallel orientation of the MPER with the membrane surface, thus allowing MPERs of neighboring trimers to interact with each other to cause clustering. These solid-state NMR data and molecular dynamics simulations suggest that MPER and cholesterol cooperatively govern the clustering of gp41 trimers during virus-cell membrane fusion.
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Affiliation(s)
- Nhi Tran
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States
| | - Younghoon Oh
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States
| | - Madeleine Sutherland
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States; Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States; Department of Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States.
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States. https://twitter.com/MeiHongLab
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25
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Palmina NP, Sazhina NN, Bogdanova NG, Antipova AS, Martirosova EI, Plashchina IG, Kasparov VV, Semenova MG. The Physico-Chemical Properties of Liposomes Made from Lipids of the Liver and Brain of Mice Receiving Nanolipid Complexes. Biophysics (Nagoya-shi) 2021. [DOI: 10.1134/s0006350921050171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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26
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Guo J, Ito H, Higuchi Y, Bohinc K, Shimokawa N, Takagi M. Three-Phase Coexistence in Binary Charged Lipid Membranes in a Hypotonic Solution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9683-9693. [PMID: 34288679 DOI: 10.1021/acs.langmuir.1c00967] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigated the phase separation of dioleoylphosphatidylserine (DOPS) and dipalmitoylphosphatidylcholine (DPPC) in giant unilamellar vesicles in a hypotonic solution using fluorescence and confocal laser scanning microscopy. Although phase separation in charged lipid membranes is generally suppressed by the electrostatic repulsion between the charged headgroups, osmotic stress can promote the formation of charged lipid domains. Interestingly, we observed a three-phase coexistence even in the DOPS/DPPC binary lipid mixtures. The three phases were DPPC-rich, dissociated DOPS-rich, and nondissociated DOPS-rich phases. The two forms of DOPS were found to coexist owing to the ionization of the DOPS headgroup, such that the system could be regarded as quasi-ternary. The three formed phases with differently ionized DOPS domains were successfully identified experimentally by monitoring the adsorption of positively charged particles. In addition, coarse-grained molecular dynamics simulations confirmed the stability of the three-phase coexistence. Attraction mediated by hydrogen bonding between protonated DOPS molecules and reduction of the electrostatic interactions at the domain boundaries stabilized the three-phase coexistence.
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Affiliation(s)
- Jingyu Guo
- School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa 923-1292, Japan
| | - Hiroaki Ito
- Department of Physics, Chiba University, Chiba 263-8522, Japan
| | - Yuji Higuchi
- Institute for Solid State Physics, The University of Tokyo, Chiba 227-8581, Japan
| | - Klemen Bohinc
- Faculty of Health Sciences, University of Ljubljana, Ljubljana SI-1000, Slovenia
| | - Naofumi Shimokawa
- School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa 923-1292, Japan
| | - Masahiro Takagi
- School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa 923-1292, Japan
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27
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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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28
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Majewska M, Khan F, Pieta IS, Wróblewska A, Szmigielski R, Pieta P. Toxicity of selected airborne nitrophenols on eukaryotic cell membrane models. CHEMOSPHERE 2021; 266:128996. [PMID: 33288286 DOI: 10.1016/j.chemosphere.2020.128996] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 10/26/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Nitroaromatics belong to the group of toxic components of aerosol particles and atmospheric hydrometeors that enter the atmosphere through biomass burning and fuel combustion. In the present work, we report on the cytotoxic effects of a 2-, 3- and 4-nitrophenol mixture on a model eukaryotic-like cell membrane and compared it with in vitro cellular models BEAS-2B (immortalized bronchial epithelial cells) and A549 (cancerous alveolar epithelial cells). A selected model biomembrane comprised of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) was studied. The electrochemical-based method, combined with atomic force microscopy (AFM) and phase-contrast microscopy imaging, allowed to get insights into the mechanism of cellular function disruption caused by airborne nitrophenols. The efficacy of the method is supported by the data obtained from in vitro experiments performed on cell models. The nitrophenol mixture exhibited cytotoxic effects at concentrations above 100 μg mL-1, as demonstrated by phase-contrast microscopy in real lung cell lines. Electrochemical impedance spectroscopy (EIS) revealed the formation of membrane defects at a nitrophenol concentration of 200 μg mL-1. AFM imaging confirmed the model membrane disintegration and phospholipids rearrangement in the presence of nitrophenols. These observations indicate that particle-bound nitrophenols induce substantial changes in cell membranes and make them more permeable to aerosol, resulting in major cellular damage in the lungs when inhaled. The study provides initial evidence of cellular membrane damage induced by three important nitrated phenols present in the environment.
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Affiliation(s)
- Marta Majewska
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Faria Khan
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Izabela S Pieta
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Aleksandra Wróblewska
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Rafal Szmigielski
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland.
| | - Piotr Pieta
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland.
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29
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Giuliano CB, Cvjetan N, Ayache J, Walde P. Multivesicular Vesicles: Preparation and Applications. CHEMSYSTEMSCHEM 2021. [DOI: 10.1002/syst.202000049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Camila Betterelli Giuliano
- Elvesys – Microfluidics Innovation Center 172 Rue de Charonne 75011 Paris France
- University of Strasbourg CNRS ISIS UMR 7006 67000 Strasbourg France
| | - Nemanja Cvjetan
- ETH Zürich Department of Materials Laboratory for Multifunctional Materials Vladimir-Prelog-Weg 5 8093 Zürich Switzerland
| | - Jessica Ayache
- Elvesys – Microfluidics Innovation Center 172 Rue de Charonne 75011 Paris France
| | - Peter Walde
- ETH Zürich Department of Materials Laboratory for Multifunctional Materials Vladimir-Prelog-Weg 5 8093 Zürich Switzerland
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30
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Abstract
Recent experiments have shown that certain molecular agents can selectively penetrate and aggregate in bacterial lipid membranes, leading to their permeability and rupture. To help reveal and understand the underlying mechanisms, here we establish a theory to show that the deformation energy of the membrane tends to limit the growth of molecular domains on a lipid membrane, resulting in a characteristic domain size, and that the domain aggregation significantly reduces the energy barrier to pore growth. Coarse-grained molecular dynamics simulations are performed to validate such domain aggregation and associated pore formation. This study sheds light on how lipid membranes can be damaged through molecular domain aggregation and contributes to establish a theoretical foundation for the next-generation membrane-targeting nanomedicine.
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Affiliation(s)
- Yue Liu
- School of Engineering, Brown University, Providence, Rhode Island 02912, United States
| | - Guijin Zou
- Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island 02912, United States
- Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore
- School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, 70 Nanyang Drive, Singapore 639798, Singapore
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31
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Staneva G, Watanabe C, Puff N, Yordanova V, Seigneuret M, Angelova MI. Amyloid-β Interactions with Lipid Rafts in Biomimetic Systems: A Review of Laboratory Methods. Methods Mol Biol 2021; 2187:47-86. [PMID: 32770501 DOI: 10.1007/978-1-0716-0814-2_4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Biomimetic lipid bilayer systems are a useful tool for modeling specific properties of cellular membranes in order to answer key questions about their structure and functions. This approach has prompted scientists from all over the world to create more and more sophisticated model systems in order to decipher the complex lateral and transverse organization of cellular plasma membranes. Among a variety of existing biomembrane domains, lipid rafts are defined as small, dynamic, and ordered assemblies of lipids and proteins, enriched in cholesterol and sphingolipids. Lipid rafts appear to be involved in the development of Alzheimer's disease (AD) by affecting the aggregation of the amyloid-β (Aβ) peptide at neuronal membranes thereby forming toxic oligomeric species. In this review, we summarize the laboratory methods which allow to study the interaction of Aβ with lipid rafts. We describe step by step protocols to form giant (GUVs) and large unilamellar vesicles (LUVs) containing raft-mimicking domains surrounded by membrane nonraft regions. Using fluorescence microscopy GUV imaging protocols, one can design experiments to visualize micron-scale raft-like domains, to determine the micron-scale demixing temperature of a given lipid mixture, construct phase diagram, and photogenerate domains in order to assess the dynamics of raft formation and raft size distribution. LUV fluorescence spectroscopy protocols with proper data analysis can be used to measure molecular packing of raft/nonraft regions of the membrane, to report on nanoscale raft formation and determine nanoscale demixing temperature. Because handling of the Aβ requires dedicated laboratory experience, we present illustrated protocols for Aβ-stock aliquoting, Aβ aqueous solubilization, oligomer preparation, determination of the Aβ concentration before and after filtration. Thioflavin binding, dynamic light scattering, and transmission electron microscopy protocols are described as complementary methods to detect Aβ aggregation kinetics, aggregate sizes, and morphologies of observed aggregates.
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Affiliation(s)
- Galya Staneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
| | - Chiho Watanabe
- Komaba Institute for Science, The University of Tokyo, Tokyo, Japan
| | - Nicolas Puff
- Faculty of Science and Engineering, UFR 925 Physics, Sorbonne Université, Paris, France
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
| | - Vesela Yordanova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Michel Seigneuret
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
| | - Miglena I Angelova
- Faculty of Science and Engineering, UFR 925 Physics, Sorbonne Université, Paris, France
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
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32
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Yang J, Jin J, Li S. Role of polyunsaturated phospholipids in liquid-ordered and liquid-disordered phases. RSC Adv 2021; 11:27115-27120. [PMID: 35480686 PMCID: PMC9037819 DOI: 10.1039/d1ra02692e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/30/2021] [Indexed: 11/21/2022] Open
Abstract
Polyunsaturated phospholipids play a strong repulsive role in the liquid-disordered phase but a weak role in the liquid-ordered phase.
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Affiliation(s)
- Jing Yang
- College of Education, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Jianyu Jin
- College of Education, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Shiben Li
- Department of Physics, Wenzhou University, Wenzhou, Zhejiang 325035, China
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33
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Low-flux scanning electron diffraction reveals substructures inside the ordered membrane domain. Sci Rep 2020; 10:22188. [PMID: 33349660 PMCID: PMC7752913 DOI: 10.1038/s41598-020-79083-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/23/2020] [Indexed: 01/19/2023] Open
Abstract
Ordered/disordered phase separation occurring in bio-membranes has piqued researchers’ interest because these ordered domains, called lipid rafts, regulate important biological functions. The structure of the ordered domain has been examined with artificial membranes, which undergo macroscopic ordered/disordered phase separation. However, owing to technical difficulties, the local structure inside ordered domains remains unknown. In this study, we employed electron diffraction to examine the packing structure of the lipid carbon chains in the ordered domain. First, we prepared dehydrated monolayer samples using a rapid-freezing and sublimation protocol, which attenuates the shrinkage of the chain-packing lattice in the dehydration process. Then, we optimised the electron flux to minimise beam damage to the monolayer sample. Finally, we developed low-flux scanning electron diffraction and assessed the chain packing structure inside the ordered domain formed in a distearoylphosphatidylcholine/dioleoylphosphatidylcholine binary monolayer. Consequently, we discovered that the ordered domain contains multiple subdomains with different crystallographic axes. Moreover, the size of the subdomain is larger in the domain centre than that near the phase boundary. To our knowledge, this is the first study to reveal the chain packing structures inside an ordered domain.
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34
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Woodward X, Kelly CV. Single-lipid dynamics in phase-separated supported lipid bilayers. Chem Phys Lipids 2020; 233:104991. [PMID: 33121937 DOI: 10.1016/j.chemphyslip.2020.104991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/02/2020] [Accepted: 10/06/2020] [Indexed: 11/26/2022]
Abstract
Phase separation is a fundamental organizing mechanism on cellular membranes. Lipid phases have complex dependencies on the membrane composition, curvature, tension, and temperature. Lipid diffusion rates vary by up to ten-fold between liquid-disordered (Ld) and liquid-ordered (Lo) phases depending on the membrane composition, measurement technique, and the surrounding environment. This manuscript reports the lipid diffusion on phase-separated supported lipid bilayers (SLBs) with varying temperature, composition, and lipid phase. Lipid diffusion is measured by single-particle tracking (SPT) and fluorescence correlation spectroscopy (FCS) via custom data acquisition and analysis protocols that apply to diverse membranes systems. Traditionally, SPT is sensitive to diffuser aggregation, whereas the diffusion rates reported by FCS are unaffected by the presence of immobile aggregates. Within this manuscript, we report (1) improved single-particle tracking analysis of lipid diffusion, (2) comparison and consistency between diffusion measurement methods for non-Brownian diffusers, and (3) the application of these methods to measure the phase, temperature, and composition dependencies in lipid diffusion. We demonstrate improved SPT analysis methods that yield consistent FCS and SPT diffusion results even when most fluorescent lipids are frequently confined within aggregates within the membrane. With varying membrane composition and temperature, we demonstrate differences in diffusion between the Ld and Lo phases of SLBs.
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Affiliation(s)
- Xinxin Woodward
- Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States
| | - Christopher V Kelly
- Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States.
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35
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Aghaaminiha M, Ghanadian SA, Ahmadi E, Farnoud AM. A machine learning approach to estimation of phase diagrams for three-component lipid mixtures. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183350. [PMID: 32407774 DOI: 10.1016/j.bbamem.2020.183350] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 04/24/2020] [Accepted: 05/07/2020] [Indexed: 12/27/2022]
Abstract
The plasma membrane of eukaryotic cells is commonly believed to contain ordered lipid domains. The interest in understanding the origin of such domains has led to extensive studies on the phase behavior of mixed lipid systems. Three-component phase diagrams, composed of a high melting temperature (Tm) lipid, cholesterol, and a low Tm lipid have been valuable in studying lipid phase behavior. However, developing phase diagrams over the entire composition space and with precise tie-lines requires significant experimental effort. In this study, a machine learning approach was used to predict the Tm of lipids and generate phase diagrams from lipid mixtures. First, artificial neural network (ANN) was used for the prediction of Tm. The network was trained using available Tm data and was able to generate Tm values that closely matched literature results for its testing dataset. This model was then used to predict the Tm for lipids that have not yet been experimentally tested. Then, random forests (RF) and support vector machines (SVM) were trained and tested for their ability to predict a test three-component phase diagram. The model from the RF algorithm was able to generate a diagram that closely matched published results. This model was then used to generate phase diagrams for lipid mixtures at various temperatures and various degrees of unsaturation. This machine learning approach to the generation of lipid phase diagrams has the potential to save significant time and resources in studies of lipid phase behavior.
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Affiliation(s)
- Mohammadreza Aghaaminiha
- Department of Chemical and Biomolecular Engineering, Russ College of Engineering and Technology, Ohio University, Athens, OH 45701, USA
| | - Sara Akbar Ghanadian
- Department of Industrial and Systems Engineering, Russ College of Engineering and Technology, Ohio University, Athens, OH 45701, USA
| | - Ehsan Ahmadi
- Department of Business, School of Business and Leadership, Our Lady of the Lake University, San Antonio, TX 78207, USA.
| | - Amir M Farnoud
- Department of Chemical and Biomolecular Engineering, Russ College of Engineering and Technology, Ohio University, Athens, OH 45701, USA.
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36
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DiPasquale M, Nguyen MHL, Rickeard BW, Cesca N, Tannous C, Castillo SR, Katsaras J, Kelley EG, Heberle FA, Marquardt D. The antioxidant vitamin E as a membrane raft modulator: Tocopherols do not abolish lipid domains. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183189. [PMID: 31954106 PMCID: PMC10443432 DOI: 10.1016/j.bbamem.2020.183189] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 01/07/2020] [Accepted: 01/09/2020] [Indexed: 01/06/2023]
Abstract
The antioxidant vitamin E is a commonly used vitamin supplement. Although the multi-billion dollar vitamin and nutritional supplement industry encourages the use of vitamin E, there is very little evidence supporting its actual health benefits. Moreover, vitamin E is now marketed as a lipid raft destabilizing anti-cancer agent, in addition to its antioxidant behaviour. Here, we studied the influence of vitamin E and some of its vitamers on membrane raft stability using phase separating unilamellar lipid vesicles in conjunction with small-angle scattering techniques and fluorescence microscopy. We find that lipid phase behaviour remains unperturbed well beyond physiological concentrations of vitamin E (up to a mole fraction of 0.10). Our results are consistent with a proposed line active role of vitamin E at the domain boundary. We discuss the implications of these findings as they pertain to lipid raft modification in native membranes, and propose a new hypothesis for the antioxidant mechanism of vitamin E.
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Affiliation(s)
- Mitchell DiPasquale
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - Michael H L Nguyen
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - Brett W Rickeard
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - Nicole Cesca
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - Christopher Tannous
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - Stuart R Castillo
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada
| | - John Katsaras
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA
| | - Elizabeth G Kelley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | | | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario,Canada; Department of Physics, University of Windsor, Windsor, Ontario, Canada.
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37
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Engberg O, Lin KL, Hautala V, Slotte JP, Nyholm TKM. Sphingomyelin Acyl Chains Influence the Formation of Sphingomyelin- and Cholesterol-Enriched Domains. Biophys J 2020; 119:913-923. [PMID: 32755561 DOI: 10.1016/j.bpj.2020.07.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 07/01/2020] [Accepted: 07/06/2020] [Indexed: 12/19/2022] Open
Abstract
The segregation of lipids into lateral membrane domains has been extensively studied. It is well established that the structural differences between phospholipids play an important role in lateral membrane organization. When a high enough cholesterol concentration is present in the bilayer, liquid-ordered (Lo) domains, which are enriched in cholesterol and saturated phospholipids such as sphingomyelin (SM), may form. We have recently shown that such a formation of domains can be facilitated by the affinity differences of cholesterol for the saturated and unsaturated phospholipids present in the bilayer. In mammalian membranes, the saturated phospholipids are usually SMs with different acyl chains, the abundance of which vary with cell type. In this study, we investigated how the acyl chain structure of SMs affects the formation of SM- and cholesterol-enriched domains. From the analysis of trans-parinaric acid fluorescence emission lifetimes, we could determine that cholesterol facilitated lateral segregation most with the SMs that had 16 carbon-long acyl chains. Using differential scanning calorimetry and Förster resonance energy transfer techniques, we observed that the SM- and cholesterol-enriched domains with 16 carbon-long SMs were most thermally stabilized by cholesterol. The Förster resonance energy transfer technique also suggested that the same SMs also form the largest Lo domains. In agreement with our previously published data, the extent of influence that cholesterol had on the propensity of lateral segregation and the properties of Lo domains correlated with the relative affinity of cholesterol for the phospholipids present in the bilayers. Therefore, the specific SM species present in the membranes, together with unsaturated phospholipids and cholesterol, can be used by the cell to fine-tune the lateral structure of the membranes.
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Affiliation(s)
- Oskar Engberg
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku, Finland
| | - Kai-Lan Lin
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku, Finland
| | - Victor Hautala
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku, Finland
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku, Finland
| | - Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku, Finland.
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38
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Huang J, Hiraki S, Feigenson GW. Calculation of Liquid-Disordered/Liquid-Ordered Line Tension from Pairwise Lipid Interactions. J Phys Chem B 2020; 124:4949-4959. [DOI: 10.1021/acs.jpcb.0c03329] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- J. Huang
- Department of Physics and Astronomy, Texas Tech University, Box 41051, Lubbock, Texas 79409, United States
| | - S. Hiraki
- Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan
| | - G. W. Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States
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39
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Sankaran J, Wohland T. Fluorescence strategies for mapping cell membrane dynamics and structures. APL Bioeng 2020; 4:020901. [PMID: 32478279 PMCID: PMC7228782 DOI: 10.1063/1.5143945] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 04/17/2020] [Indexed: 12/20/2022] Open
Abstract
Fluorescence spectroscopy has been a cornerstone of research in membrane dynamics and organization. Technological advances in fluorescence spectroscopy went hand in hand with discovery of various physicochemical properties of membranes at nanometric spatial and microsecond timescales. In this perspective, we discuss the various challenges associated with quantification of physicochemical properties of membranes and how various modes of fluorescence spectroscopy have overcome these challenges to shed light on the structure and organization of membranes. Finally, we discuss newer measurement strategies and data analysis tools to investigate the structure, dynamics, and organization of membranes.
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40
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Differential impact of synthetic antitumor lipid drugs on the membrane organization of phosphatidic acid and diacylglycerol monolayers. Chem Phys Lipids 2020; 229:104896. [PMID: 32184083 DOI: 10.1016/j.chemphyslip.2020.104896] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 02/19/2020] [Accepted: 03/11/2020] [Indexed: 12/16/2022]
Abstract
Anti-tumour lipids are synthetic analogues of lysophosphatidylcholine. These drugs are both cytotoxic and cytostatic, and more interestingly, exert these effects preferentially in tumour cells. While the exact mechanism of action isn't fully elucidated, these drugs appear to preferentially partition into rigid lipid domains in cell membranes. Upon insertion, the compounds alter membrane domain organization, disrupt normal signal transduction, and cause cell death. Recently, it has been reported that these drugs induce accumulation of diacylglycerol in yeast cells which in turn sensitizes cells to the drugs. Conversely, phosphatidic acid accumulation appears to protect cells against the drugs. In the current work, the aim was to compare the biophysical effects of the drugs edelfosine, miltefosine and perifosine on monolayers of dimyristoyl phosphatidic acid, dimyristoyl glycerol and an equimolar mixture, to understand how these lipids modulate the mode of action. Surface pressure - area isotherms, compression moduli and Brewster angle microscopy were used to compare drug effects on lipid packing, monolayer compressibility and lateral domain organization of these films. Results suggest that edelfosine and miltefosine have stabilizing effects on all of the monolayers, while perifosine destabilizes dimyristoyl glycerol and the equimolar mixture. Additionally, all three drugs change the morphology of the domains observed. Based on these results the stabilization of diacylgylcerol by edelfosine and miltefosine may contribute to the mode of action as diacylglycerol is a known disruptor of bilayers. Perifosine however does not stabilize diacylglycerol, and therefore cell death may occur through a more direct inhibition of specific signal transduction. These results suggest that perifosine may illicit cytotoxicity through a different mechanism compared to the other antitumor lipid drugs.
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41
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Gu RX, Baoukina S, Tieleman DP. Phase Separation in Atomistic Simulations of Model Membranes. J Am Chem Soc 2020; 142:2844-2856. [DOI: 10.1021/jacs.9b11057] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ruo-Xu Gu
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive, N.W., Calgary, Alberta T2N 1N4, Canada
| | - Svetlana Baoukina
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive, N.W., Calgary, Alberta T2N 1N4, Canada
| | - D. Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive, N.W., Calgary, Alberta T2N 1N4, Canada
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42
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Sibold J, Tewaag VE, Vagedes T, Mey I, Steinem C. Phase separation in pore-spanning membranes induced by differences in surface adhesion. Phys Chem Chem Phys 2020; 22:9308-9315. [DOI: 10.1039/d0cp00335b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A porous scaffold providing different adhesion energies alters the behaviour of coexisting phases in lipid membranes considerably.
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Affiliation(s)
- Jeremias Sibold
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Vera E. Tewaag
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Thomas Vagedes
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Ingo Mey
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry
- University of Göttingen
- 37077 Göttingen
- Germany
- Max Planck Institute for Dynamics and Self-Organization
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43
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Sut TN, Park S, Choe Y, Cho NJ. Characterizing the Supported Lipid Membrane Formation from Cholesterol-Rich Bicelles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15063-15070. [PMID: 31670521 DOI: 10.1021/acs.langmuir.9b02851] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Supported lipid bilayers (SLBs) are simplified model membrane systems that mimic the fundamental properties of biological cell membranes and allow the surface-sensitive tools to be used in numerous sensing applications. SLBs can be prepared by various methods including vesicle fusion, solvent-assisted lipid bilayer (SALB), and bicelle adsorption and are generally composed of phospholipids. Incorporating other biologically relevant molecules, such as cholesterol (Chol), into SLBs has been reported with the vesicle fusion and SALB methods, whereas it remains unexplored with the bicelle absorption method. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and fluorescence microscopy techniques, we explored the possibility of forming SLBs from Chol-containing bicelles and discovered that Chol-enriched SLBs can be fabricated with bicelles. We also compared the Chol-enriched SLB formation of the bicelle method to that of vesicle fusion and SALB and discussed how the differences in lipid assembly properties can cause the differences in the adsorption kinetics and final results of SLB formation. Collectively, our findings demonstrate that the vesicle fusion method is least favorable for forming Chol-enriched SLBs, whereas the SALB and bicelle methods are more favorable, highlighting the need to consider the application requirements when choosing a suitable method for the formation of Chol-enriched SLBs.
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Affiliation(s)
- Tun Naw Sut
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Soohyun Park
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Younghwan Choe
- Department of Chemistry , Columbia University , 3000 Broadway , New York 10027 , United States
| | - Nam-Joon Cho
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
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44
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Oliveira MC, Yusupov M, Bogaerts A, Cordeiro RM. Molecular dynamics simulations of mechanical stress on oxidized membranes. Biophys Chem 2019; 254:106266. [PMID: 31629220 DOI: 10.1016/j.bpc.2019.106266] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 09/09/2019] [Accepted: 09/12/2019] [Indexed: 12/27/2022]
Abstract
Biomembranes are under constant attack of free radicals that may lead to lipid oxidation in conditions of oxidative stress. The products generated during lipid oxidation are responsible for structural and dynamical changes which may jeopardize the membrane function. For instance, the local rearrangements of oxidized lipid molecules may induce membrane rupture. In this study, we investigated the effects of mechanical stress on oxidized phospholipid bilayers (PLBs). Model bilayers were stretched until pore formation (or poration) using non-equilibrium molecular dynamics simulations. We studied single-component homogeneous membranes composed of lipid oxidation products, as well as two-component heterogeneous membranes with coexisting native and oxidized domains. In homogeneous membranes, the oxidation products with -OH and -OOH groups reduced the areal strain required for pore formation, whereas the oxidation product with O group behaved similarly to the native membrane. In heterogeneous membranes composed of oxidized and non-oxidized domains, we tested the hypothesis according to which poration may be facilitated at the domain interface region. However, results were inconclusive due to their large statistical variance and sensitivity to simulation setup parameters. We pointed out important technical issues that need to be considered in future simulations of mechanically-induced poration of heterogeneous membranes. This research is of interest for photodynamic therapy and plasma medicine, because ruptured and intact plasma membranes are experimentally considered hallmarks of necrotic and apoptotic cell death.
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Affiliation(s)
- Maria C Oliveira
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Avenida dos Estados 5001, CEP 09210-580 Santo André, SP, Brazil
| | - Maksudbek Yusupov
- Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
| | - Annemie Bogaerts
- Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
| | - Rodrigo M Cordeiro
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Avenida dos Estados 5001, CEP 09210-580 Santo André, SP, Brazil.
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45
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Sah BK, Das K, Kundu S. pH-dependent structure, pattern and hysteresis behaviour of lipid (DMPA)-protein (BSA) monolayer complex. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.123663] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Nyholm TKM, Engberg O, Hautala V, Tsuchikawa H, Lin KL, Murata M, Slotte JP. Impact of Acyl Chain Mismatch on the Formation and Properties of Sphingomyelin-Cholesterol Domains. Biophys J 2019; 117:1577-1588. [PMID: 31610877 DOI: 10.1016/j.bpj.2019.09.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 11/30/2022] Open
Abstract
Lateral segregation and the formation of lateral domains are well-known phenomena in ternary lipid bilayers composed of an unsaturated (low gel-to-liquid phase transition temperature (Tm)) phospholipid, a saturated (high-Tm) phospholipid, and cholesterol. The formation of lateral domains has been shown to be influenced by differences in phospholipid acyl chain unsaturation and length. Recently, we also showed that differential interactions of cholesterol with low- and high-Tm phospholipids in the bilayer can facilitate phospholipid segregation. Now, we have investigated phospholipid-cholesterol interactions and their role in lateral segregation in ternary bilayers composed of different unsaturated phosphatidylcholines (PCs) with varying acyl chain lengths, N-palmitoyl-D-erythro-sphingomyelin (PSM), and cholesterol. Using deuterium NMR spectroscopy, we determined how PSM was influenced by the acyl chain composition in surrounding PC environments and correlated this with the affinity of cholestatrienol (a fluorescent cholesterol analog) for PSM in the different PC environments. Results from a combination of time-resolved fluorescence measurements of trans-parinaric acid and Förster resonance energy transfer experiments showed that the relative affinity of cholesterol for phospholipids determined the degree to which the sterol promoted domain formation. From Förster resonance energy transfer, deuterium NMR, and differential scanning calorimetry results, it was clear that cholesterol also influenced both the thermostability of the domains and the degree of order in and outside the PSM-rich domains. The results of this study have shown that the affinity of cholesterol for both low-Tm and high-Tm phospholipids and the effects of low- and high-Tm phospholipids on each other influence both lateral structure and domain properties in complex bilayers. We envision that similar effects also contribute to lateral heterogeneity in even more complex biological membranes.
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Affiliation(s)
- Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland.
| | - Oskar Engberg
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Victor Hautala
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Kai-Lan Lin
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
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Heberle FA. With Lipid Rafts, Context Is Everything. Biophys J 2019; 117:1549-1551. [PMID: 31604521 DOI: 10.1016/j.bpj.2019.07.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 07/31/2019] [Indexed: 12/18/2022] Open
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Scott HL, Skinkle A, Kelley EG, Waxham MN, Levental I, Heberle FA. On the Mechanism of Bilayer Separation by Extrusion, or Why Your LUVs Are Not Really Unilamellar. Biophys J 2019; 117:1381-1386. [PMID: 31586522 DOI: 10.1016/j.bpj.2019.09.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/18/2019] [Accepted: 09/10/2019] [Indexed: 11/18/2022] Open
Abstract
Extrusion through porous filters is a widely used method for preparing biomimetic model membranes. Of primary importance in this approach is the efficient production of single bilayer (unilamellar) vesicles that eliminate the influence of interlamellar interactions and strictly define the bilayer surface area available to external reagents such as proteins. Submicroscopic vesicles produced using extrusion are widely assumed to be unilamellar, and large deviations from this assumption would impact interpretations from many model membrane experiments. Using three probe-free methods-small angle X-ray and neutron scattering and cryogenic electron microscopy-we report unambiguous evidence of extensive multilamellarity in extruded vesicles composed of neutral phosphatidylcholine lipids, including for the common case of neutral lipids dispersed in physiological buffer and extruded through 100-nm diameter pores. In such preparations, only ∼35% of lipids are externally accessible and this fraction is highly dependent on preparation conditions. Charged lipids promote unilamellarity as does decreasing solvent ionic strength, indicating the importance of electrostatic interactions in determining the lamellarity of extruded vesicles. Smaller extrusion pore sizes also robustly increase the fraction of unilamellar vesicles, suggesting a role for membrane bending. Taken together, these observations suggest a mechanistic model for extrusion, wherein the formation of unilamellar vesicles involves competition between bilayer bending and adhesion energies. The findings presented here have wide-ranging implications for the design and interpretation of model membrane studies, especially ensemble-averaged observations relying on the assumption of unilamellarity.
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Affiliation(s)
- Haden L Scott
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Allison Skinkle
- Department of Biosciences, Rice University, Houston, Texas; Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas
| | - Elizabeth G Kelley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland
| | - M Neal Waxham
- Department of Neurobiology and Anatomy, University of Texas Health Science Center, Houston, Texas
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas.
| | - Frederick A Heberle
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee; Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas.
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Fonda P, Rinaldin M, Kraft DJ, Giomi L. Thermodynamic equilibrium of binary mixtures on curved surfaces. Phys Rev E 2019; 100:032604. [PMID: 31639923 DOI: 10.1103/physreve.100.032604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Indexed: 06/10/2023]
Abstract
We study the global influence of curvature on the free energy landscape of two-dimensional binary mixtures confined on closed surfaces. Starting from a generic effective free energy, constructed on the basis of symmetry considerations and conservation laws, we identify several model-independent phenomena, such as a curvature-dependent line tension and local shifts in the binodal concentrations. To shed light on the origin of the phenomenological parameters appearing in the effective free energy, we further construct a lattice-gas model of binary mixtures on nontrivial substrates, based on the curved-space generalization of the two-dimensional Ising model. This allows us to decompose the interaction between the local concentration of the mixture and the substrate curvature into four distinct contributions, as a result of which the phase diagram splits into critical subdiagrams. The resulting free energy landscape can admit, as stable equilibria, strongly inhomogeneous mixed phases, which we refer to as "antimixed" states below the critical temperature. We corroborate our semianalytical findings with phase-field numerical simulations on realistic curved lattices. Despite this work being primarily motivated by recent experimental observations of multicomponent lipid vesicles supported by colloidal scaffolds, our results are applicable to any binary mixture confined on closed surfaces of arbitrary geometry.
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Affiliation(s)
- Piermarco Fonda
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - Melissa Rinaldin
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
- Huygens-Kamerlingh Onnes Laboratory, Universiteit Leiden, P.O. Box 9504, 2300 RA Leiden, Netherlands
| | - Daniela J Kraft
- Huygens-Kamerlingh Onnes Laboratory, Universiteit Leiden, P.O. Box 9504, 2300 RA Leiden, Netherlands
| | - Luca Giomi
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
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Et-Thakafy O, Guyomarc'h F, Lopez C. Young modulus of supported lipid membranes containing milk sphingomyelin in the gel, fluid or liquid-ordered phase, determined using AFM force spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1523-1532. [DOI: 10.1016/j.bbamem.2019.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/12/2019] [Accepted: 07/04/2019] [Indexed: 10/26/2022]
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