1
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Kumar H, Mandal S, Yadav R, Gupta S, Meena H, Kadu M, Kudawla R, Sharma P, Kaur IP, Maiti S, Ipsen JH, Bhatia T. Bottom-up approach to explore alpha-amylase assisted membrane remodelling. Chem Phys Lipids 2024; 259:105374. [PMID: 38176612 DOI: 10.1016/j.chemphyslip.2023.105374] [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: 08/29/2023] [Revised: 12/19/2023] [Accepted: 12/27/2023] [Indexed: 01/06/2024]
Abstract
Soluble alpha-amylases play an important role in the catabolism of polysaccharides. In this work, we show that the malt α -amylase can interact with the lipid membrane and further alter its mechanical properties. Vesicle fluctuation spectroscopy is used for quantitative measurement of the membrane bending rigidity of phosphatidylcholines lipid vesicles from the shape fluctuation based on the whole contour of Giant Unilamellar Vesicles (GUVs). The bending rigidity of the 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipid vesicles in water increases significantly with the presence of 0.14 micromolar alpha-amylase (AA) in the exterior solution. It appears that the enzyme present in the external solution interacts with the outer layer of the bilayer membrane, leading to an asymmetry of the solution on either side of the bilayer membrane and altering its elasticity. At AA concentration of 1.5 micromolars and above, changes in the morphology of the GUV membrane are observed. The interaction between AA in the external solution and the external leaflet causes the bilayer membrane to curve spontaneously, leading to the formation of outbuds, giving a positive spontaneous curvature of C0 ≤ 0.05 μm-1 at ≈ 1 mg / ml of the AA concentration. We validate and characterize its concentration-dependent role in stabilizing the membrane curvature. Our findings indicate that the involvement of the enzyme, depending on the concentration, can have a considerable effect on the mechanical characteristics of the membrane.
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Affiliation(s)
- Harshit Kumar
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Sayar Mandal
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Reena Yadav
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Suhasi Gupta
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Hemraj Meena
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Mayur Kadu
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Rajni Kudawla
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Pratibha Sharma
- University Institute of Pharmaceutical Sciences, Punjab University, Sector 14, Chandigarh 160014, Punjab, India
| | - Indu Pal Kaur
- University Institute of Pharmaceutical Sciences, Punjab University, Sector 14, Chandigarh 160014, Punjab, India
| | - Subhabrata Maiti
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - John H Ipsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej, Odense, 5230 M, Denmark.
| | - Tripta Bhatia
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India.
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2
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Granek R, Hoffmann I, Kelley EG, Nagao M, Vlahovska PM, Zilman A. Dynamic structure factor of undulating vesicles: finite-size and spherical geometry effects with application to neutron spin echo experiments. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:12. [PMID: 38355850 DOI: 10.1140/epje/s10189-023-00400-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 12/11/2023] [Indexed: 02/16/2024]
Abstract
We consider the dynamic structure factor (DSF) of quasi-spherical vesicles and present a generalization of an expression that was originally formulated by Zilman and Granek (ZG) for scattering from isotropically oriented quasi-flat membrane plaquettes. The expression is obtained in the form of a multi-dimensional integral over the undulating membrane surface. The new expression reduces to the original stretched exponential form in the limit of sufficiently large vesicles, i.e., in the micron range or larger. For much smaller unilamellar vesicles, deviations from the asymptotic, stretched exponential equation are noticeable even if one assumes that the Seifert-Langer leaflet density mode is completely relaxed and membrane viscosity is neglected. To avoid the need for an exhaustive numerical integration while fitting to neutron spin echo (NSE) data, we provide a useful approximation for polydisperse systems that tests well against the numerical integration of the complete expression. To validate the new expression, we performed NSE experiments on variable-size vesicles made of a POPC/POPS lipid mixture and demonstrate an advantage over the original stretched exponential form or other manipulations of the original ZG expression that have been deployed over the years to fit the NSE data. In particular, values of the membrane bending rigidity extracted from the NSE data using the new approximations were insensitive to the vesicle radii and scattering wavenumber and compared very well with expected values of the effective bending modulus ([Formula: see text]) calculated from results in the literature. Moreover, the generalized scattering theory presented here for an undulating quasi-spherical shell can be easily extended to other models for the membrane undulation dynamics beyond the Helfrich Hamiltonian and thereby provides the foundation for the study of the nanoscale dynamics in more complex and biologically relevant model membrane systems.
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Affiliation(s)
- Rony Granek
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel.
| | - Ingo Hoffmann
- Institut Laue-Langevin (ILL), 71 Avenue des Martys, 38042, Grenoble, CEDEX 9, France.
| | - Elizabeth G Kelley
- Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899, USA.
| | - Michihiro Nagao
- Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA
- Department of Physics and Astronomy, University of Delaware, Newark, DE, 19716, USA
| | - Petia M Vlahovska
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL, 60208, USA
| | - Anton Zilman
- Department of Physics, University of Toronto, 60 St George St, Toronto, ON, M5S 1A7, Canada
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3
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Miller EJ, Phan MD, Shah J, Honerkamp-Smith AR. Passive and reversible area regulation of supported lipid bilayers in response to fluid flow. Biophys J 2023; 122:2242-2255. [PMID: 36639867 PMCID: PMC10257118 DOI: 10.1016/j.bpj.2023.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/21/2022] [Accepted: 01/09/2023] [Indexed: 01/14/2023] Open
Abstract
Biological and model membranes are frequently subjected to fluid shear stress. However, membrane mechanical responses to flow remain incompletely described. This is particularly true of membranes supported on a solid substrate, and the influences of membrane composition and substrate roughness on membrane flow responses remain poorly understood. Here, we combine microfluidics, fluorescence microscopy, and neutron reflectivity to explore how supported lipid bilayer patches respond to controlled shear stress. We demonstrate that lipid membranes undergo a significant, passive, and partially reversible increase in membrane area due to flow. We show that these fluctuations in membrane area can be constrained, but not prevented, by increasing substrate roughness. Similar flow-induced changes to membrane structure may contribute to the ability of living cells to sense and respond to flow.
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Affiliation(s)
| | - Minh D Phan
- Large-Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Center for Neutron Science, Department of Chemical & Biomolecular Engineering, University of Delaware, Newark, Delaware
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4
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Mura M, Humphreys B, Gilbert J, Salis A, Nylander T. Cation and buffer specific effects on the DNA-lipid interaction. Colloids Surf B Biointerfaces 2023; 223:113187. [PMID: 36739672 DOI: 10.1016/j.colsurfb.2023.113187] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/26/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023]
Abstract
Knowledge of DNA - lipid layer interactions is key for the development of biosensors, synthetic nanopores, scaffolds, and gene-delivery systems. These interactions are strongly affected by the ionic composition of the solvent. We have combined quartz crystal microbalance (QCM) and ellipsometry measurements to reveal how pH, buffers and alkali metal chloride salts affect the interaction of DNA with lipid bilayers (DOTAP/DOPC 30:70 in moles). We found that the thickness of the DNA layer adsorbed onto the lipid bilayer decreased in the order citrate > phosphate > Tris > HEPES. The effect of cations on the thickness of the DNA layer decreased in the order (K+ > Na+ > Cs+ ∼ Li+). Rationalization of the experimental results requires that adsorption, due to cation specific charge screening, is driven by the simultaneous action of two mechanisms namely, the law of matching water affinities for kosmotropes (Li+) and ion dispersion forces for chaotropes (Cs+). The outcome of these two opposing mechanisms is a "bell-shaped" specific cations sequence. Moreover, a superimposed buffer specificity, which goes beyond the simple effect of pH regulation, further modulated cation specificity. In summary, DNA-lipid bilayer interactions are maximized if citrate buffer (50 mM, pH 7.4) and KCl (100 mM) are used.
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Affiliation(s)
- Monica Mura
- Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden; Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, SS 554 bivio Sestu, 09042 Monserrato (CA), Italy; Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Via della Lastruccia 3, Sesto Fiorentino (FI), I-50019, Italy
| | - Ben Humphreys
- Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Jennifer Gilbert
- Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Andrea Salis
- Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, SS 554 bivio Sestu, 09042 Monserrato (CA), Italy; Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Via della Lastruccia 3, Sesto Fiorentino (FI), I-50019, Italy.
| | - Tommy Nylander
- Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
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5
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Huang X, Hürlimann D, Spanke HT, Wu D, Skowicki M, Dinu IA, Dufresne ER, Palivan CG. Cell-Derived Vesicles with Increased Stability and On-Demand Functionality by Equipping Their Membrane with a Cross-Linkable Copolymer. Adv Healthc Mater 2022; 11:e2202100. [PMID: 36208079 DOI: 10.1002/adhm.202202100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Indexed: 01/28/2023]
Abstract
Cell-derived vesicles retain the cytoplasm and much of the native cell membrane composition. Therefore, they are attractive for investigations of membrane biophysics, drug delivery systems, and complex molecular factories. However, their fragility and aggregation limit their applications. Here, the mechanical properties and stability of giant plasma membrane vesicles (GPMVs) are enhanced by decorating them with a specifically designed diblock copolymer, cholesteryl-poly[2-aminoethyl methacrylate-b-poly(ethylene glycol) methyl ether acrylate]. When cross-linked, this polymer brush enhances the stability of the GPMVs. Furthermore, the pH-responsiveness of the copolymer layer allows for a controlled cargo loading/release, which may enable various bioapplications. Importantly, the cross-linked-copolymer GPMVs are not cytotoxic and preserve in vitro membrane integrity and functionality. This effective strategy to equip the cell-derived vesicles with stimuli-responsive cross-linkable copolymers is expected to open a new route to the stabilization of natural membrane systems and overcome barriers to biomedical applications.
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Affiliation(s)
- Xinan Huang
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland
| | - Dimitri Hürlimann
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland.,NCCR-Molecular Systems Engineering, BPR1095, Mattenstrasse 24a, Basel, 4058, Switzerland
| | - Hendrik T Spanke
- Laboratory for Soft and Living Materials, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, Zurich, 8093, Switzerland
| | - Dalin Wu
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland
| | - Michal Skowicki
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland.,NCCR-Molecular Systems Engineering, BPR1095, Mattenstrasse 24a, Basel, 4058, Switzerland
| | - Ionel Adrian Dinu
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland.,NCCR-Molecular Systems Engineering, BPR1095, Mattenstrasse 24a, Basel, 4058, Switzerland
| | - Eric R Dufresne
- Laboratory for Soft and Living Materials, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, Zurich, 8093, Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel, BPR1096, Mattenstrasse 24a, Basel, 4058, Switzerland.,NCCR-Molecular Systems Engineering, BPR1095, Mattenstrasse 24a, Basel, 4058, Switzerland
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6
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Zhu J, McDargh ZA, Li F, Krishnakumar SS, Rothman JE, O’Shaughnessy B. Synaptotagmin rings as high-sensitivity regulators of synaptic vesicle docking and fusion. Proc Natl Acad Sci U S A 2022; 119:e2208337119. [PMID: 36103579 PMCID: PMC9499556 DOI: 10.1073/pnas.2208337119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
Synchronous release at neuronal synapses is accomplished by a machinery that senses calcium influx and fuses the synaptic vesicle and plasma membranes to release neurotransmitters. Previous studies suggested the calcium sensor synaptotagmin (Syt) is a facilitator of vesicle docking and both a facilitator and inhibitor of fusion. On phospholipid monolayers, the Syt C2AB domain spontaneously oligomerized into rings that are disassembled by Ca2+, suggesting Syt rings may clamp fusion as membrane-separating "washers" until Ca2+-mediated disassembly triggers fusion and release [J. Wang et al., Proc. Natl. Acad. Sci. U.S.A. 111, 13966-13971 (2014)].). Here, we combined mathematical modeling with experiment to measure the mechanical properties of Syt rings and to test this mechanism. Consistent with experimental results, the model quantitatively recapitulates observed Syt ring-induced dome and volcano shapes on phospholipid monolayers and predicts rings are stabilized by anionic phospholipid bilayers or bulk solution with ATP. The selected ring conformation is highly sensitive to membrane composition and bulk ATP levels, a property that may regulate vesicle docking and fusion in ATP-rich synaptic terminals. We find the Syt molecules hosted by a synaptic vesicle oligomerize into a halo, unbound from the vesicle, but in proximity to sufficiently phosphatidylinositol 4,5-bisphosphate (PIP2)-rich plasma membrane (PM) domains, the PM-bound trans Syt ring conformation is preferred. Thus, the Syt halo serves as landing gear for spatially directed docking at PIP2-rich sites that define the active zones of exocytotic release, positioning the Syt ring to clamp fusion and await calcium. Our results suggest the Syt ring is both a Ca2+-sensitive fusion clamp and a high-fidelity sensor for directed docking.
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Affiliation(s)
- Jie Zhu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Zachary A. McDargh
- Department of Chemical Engineering, Columbia University, New York, NY 10027
| | - Feng Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | | | - James E. Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Ben O’Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027
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7
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Faizi HA, Tsui A, Dimova R, Vlahovska PM. Bending Rigidity, Capacitance, and Shear Viscosity of Giant Vesicle Membranes Prepared by Spontaneous Swelling, Electroformation, Gel-Assisted, and Phase Transfer Methods: A Comparative Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:10548-10557. [PMID: 35993569 PMCID: PMC9671160 DOI: 10.1021/acs.langmuir.2c01402] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Closed lipid bilayers in the form of giant unilamellar vesicles (GUVs) are commonly used membrane models. Various methods have been developed to prepare GUVs, however it is unknown if all approaches yield membranes with the same elastic, electric, and rheological properties. Here, we combine flickering spectroscopy and electrodefomation of GUVs to measure, at identical conditions, membrane capacitance, bending rigidity and shear surface viscosity of palmitoyloleoylphosphatidylcholine (POPC) membranes formed by several commonly used preparation methods: thin film hydration (spontaneous swelling), electroformation, gel-assisted swelling using poly(vinyl alcohol) (PVA) or agarose, and phase-transfer. We find relatively similar bending rigidity value across all the methods except for the agarose hydration method. In addition, the capacitance values are similar except for vesicles prepared via PVA gel hydration. Intriguingly, membranes prepared by the gel-assisted and phase-transfer methods exhibit much higher shear viscosity compared to electroformation and spontaneous swelling, likely due to remnants of polymers (PVA and agarose) and oils (hexadecane and mineral) in the lipid bilayer structure.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
| | - Annie Tsui
- Department of Industrial Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany
| | - Petia M Vlahovska
- Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
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8
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Dolder N, Müller P, von Ballmoos C. Experimental platform for the functional investigation of membrane proteins in giant unilamellar vesicles. SOFT MATTER 2022; 18:5877-5893. [PMID: 35916307 PMCID: PMC9364335 DOI: 10.1039/d2sm00551d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Giant unilamellar vesicles (GUVs) are micrometer-sized model membrane systems that can be viewed directly under the microscope. They serve as scaffolds for the bottom-up creation of synthetic cells, targeted drug delivery and have been widely used to study membrane related phenomena in vitro. GUVs are also of interest for the functional investigation of membrane proteins that carry out many key cellular functions. A major hurdle to a wider application of GUVs in this field is the diversity of existing protocols that are optimized for individual proteins. Here, we compare PVA assisted and electroformation techniques for GUV formation under physiologically relevant conditions, and analyze the effect of immobilization on vesicle structure and membrane tightness towards small substrates and protons. There, differences in terms of yield, size, and leakage of GUVs produced by PVA assisted swelling and electroformation were found, dependent on salt and buffer composition. Using fusion of oppositely charged membranes to reconstitute a model membrane protein, we find that empty vesicles and proteoliposomes show similar fusion behavior, which allows for a rapid estimation of protein incorporation using fluorescent lipids.
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Affiliation(s)
- Nicolas Dolder
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Philipp Müller
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Christoph von Ballmoos
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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9
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Biocatalytic self-assembled synthetic vesicles and coacervates: From single compartment to artificial cells. Adv Colloid Interface Sci 2022; 299:102566. [PMID: 34864354 DOI: 10.1016/j.cis.2021.102566] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 11/15/2021] [Accepted: 11/19/2021] [Indexed: 12/18/2022]
Abstract
Compartmentalization is an intrinsic feature of living cells that allows spatiotemporal control over the biochemical pathways expressed in them. Over the years, a library of compartmentalized systems has been generated, which includes nano to micrometer sized biomimetic vesicles derived from lipids, amphiphilic block copolymers, peptides, and nanoparticles. Biocatalytic vesicles have been developed using a simple bag containing enzyme design of liposomes to multienzymes immobilized multi-vesicular compartments for artificial cell generation. Additionally, enzymes were also entrapped in membrane-less coacervate droplets to mimic the cytoplasmic macromolecular crowding mechanisms. Here, we have discussed different types of single and multicompartment systems, emphasizing their recent developments as biocatalytic self-assembled structures using recent examples. Importantly, we have summarized the strategies in the development of the self-assembled structure to improvise their adaptivity and flexibility for enzyme immobilization. Finally, we have presented the use of biocatalytic assemblies in mimicking different aspects of living cells, which further carves the path for the engineering of a minimal cell.
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10
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Gupta M, Weaver DF. Microsecond molecular dynamics studies of cholesterol-mediated myelin sheath degeneration in early Alzheimer's disease. Phys Chem Chem Phys 2021; 24:222-239. [PMID: 34878462 DOI: 10.1039/d1cp03844c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cholesterol-mediated perturbations of membrane structural integrity are key early events in the molecular pathogenesis of Alzheimer's disease (AD). In AD, protein misfolding (proteopathy) and pro-inflammatory conditions (immunopathy) culminate in neuronal death, a process enabled by altered membrane biophysical properties which render neurons more susceptible to proteopathic and immunopathic cytotoxicities. Since cholesterol is a principal neuronal membrane lipid, normal cholesterol homeostasis is central to membrane health; also, since increased cholesterol composition is especially present in neuronal myelin sheath (i.e. brain "white matter"), recent studies have not surprisingly revealed that white matter atrophy precedes the conventional biomarkers of AD (amyloid plaques, tau tangles). Employing extensive microsecond all-atom molecular dynamics simulations, we investigated biophysical and mechanical properties of myelin sheath membrane as a function of cholesterol mole fraction (χCHL). Impaired χCHL modulates multiple bilayer properties, including surface area per lipid (APL), chain order, number and mass density profiles, area compressibility and bending moduli, bilayer thickness, lipid tilt angles, H-bonding interactions and tail interdigitation. The increased orientational ordering of both palmitoyl and oleoyl chains in model healthy myelin sheath (HMS) membranes illustrates the condensing effect of cholesterol. With an increase in χCHL, number density profiles of water tend to attain bulk water number density more quickly, indicating shrinkage in the interfacial region with increasing χCHL. The average tilt value is 11.5° for the C10-C13 angle in cholesterol and 64.2° for the P-N angle in POPC lipids in HMS. These calculations provide a molecular-level understanding of myelin sheath susceptibility to pathology as an early event in the pathogenesis of AD.
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Affiliation(s)
- Mayuri Gupta
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, M5T 0S8, Canada.
| | - Donald F Weaver
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, M5T 0S8, Canada. .,Departments of Chemistry, Medicine and Pharmaceutical Sciences, University of Toronto, Toronto, ON, M55 3H6, Canada
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11
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Marušič N, Zhao Z, Otrin L, Dimova R, Ivanov I, Sundmacher K. Fusion-Induced Growth of Biomimetic Polymersomes: Behavior of Poly(dimethylsiloxane)-Poly(ethylene oxide) Vesicles in Saline Solutions Under High Agitation. Macromol Rapid Commun 2021; 43:e2100712. [PMID: 34820929 DOI: 10.1002/marc.202100712] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Indexed: 12/16/2022]
Abstract
Giant unilamellar vesicles serve as membrane models and primitive mockups of natural cells. With respect to the latter use, amphiphilic polymers can be used to replace phospholipids in order to introduce certain favorable properties, ultimately allowing for the creation of truly synthetic cells. These new properties also enable the employment of new preparation procedures that are incompatible with the natural amphiphiles. Whereas the growth of lipid compartments to micrometer dimensions has been well established, growth of their synthetic analogs remains underexplored. Here, the influence of experimental parameters like salt type/concentration and magnitude of agitation on the fusion of nanometer-sized vesicles made of poly(dimethylsiloxane)-poly(ethylene oxide) graft copolymer (PDMS-g-PEO) is investigated in detail. To this end, dynamic light scattering, microscopy, and membrane mixing assays are employed, and the process at different time and length scales is analyzed. This optimized method is used as an easy tool to obtain giant vesicles, equipped with membrane and cytosolic biomachinery, in the presence of salts at physiological concentrations.
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Affiliation(s)
- Nika Marušič
- Process Systems Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106, Magdeburg, Germany
| | - Ziliang Zhao
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424, Potsdam, Germany.,Leibniz Institute of Photonic Technology e.V., 07745, Jena, Germany.,Faculty of Physics and Astronomy, Institute of Applied Optics and Biophysics, Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Lado Otrin
- Process Systems Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106, Magdeburg, Germany
| | - Rumiana Dimova
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424, Potsdam, Germany
| | - Ivan Ivanov
- Process Systems Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106, Magdeburg, Germany
| | - Kai Sundmacher
- Process Systems Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106, Magdeburg, Germany
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12
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Demartis S, Rassu G, Murgia S, Casula L, Giunchedi P, Gavini E. Improving Dermal Delivery of Rose Bengal by Deformable Lipid Nanovesicles for Topical Treatment of Melanoma. Mol Pharm 2021; 18:4046-4057. [PMID: 34554752 PMCID: PMC8564756 DOI: 10.1021/acs.molpharmaceut.1c00468] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Cutaneous melanoma
is one of the most aggressive and metastatic
forms of skin cancer. However, current therapeutic options present
several limitations, and the annual death rate due to melanoma increases
every year. Dermal delivery of nanomedicines can effectively eradicate
primary melanoma lesions, avoid the metastatic process, and improve
survival. Rose Bengal (RB) is a sono-photosensitizer drug with intrinsic
cytotoxicity toward melanoma without external stimuli but the biopharmaceutical
profile limits its clinical use. Here, we propose deformable lipid
nanovesicles, also known as transfersomes (TF), for the targeted dermal
delivery of RB to melanoma lesions to eradicate them in the absence
of external stimuli. Considering RB’s poor ability to cross
the stratum corneum and its photosensitizer nature, transfersomal
carriers were selected simultaneously to enhance RB penetration to
the deepest skin layers and protect RB from undesired photodegradation.
RB-loaded TF dispersion (RB-TF), prepared by a modified reverse-phase
evaporation method, were nanosized with a ζ-potential value
below −30 mV. The spectrophotometric and fluorimetric analysis
revealed that RB efficiently interacted with the lipid phase. The
morphological investigations (transmission electron microscopy and
small-angle X-ray scattering) proved that RB intercalated within the
phospholipid bilayer of TF originating unilamellar and deformable
vesicles, in contrast to the rigid multilamellar unloaded ones. Such
outcomes agree with the results of the in vitro permeation study,
where the lack of a burst RB permeation peak for RB-TF, observed instead
for the free drug, suggests that a significant amount of RB interacted
with lipid nanovesicles. Also, RB-TF proved to protect RB from undesired
photodegradation over 24 h of direct light exposure. The ex vivo epidermis
permeation study proved that RB-TF significantly increased RB’s
amount permeating the epidermis compared to the free drug (78.31 vs
38.31%). Finally, the antiproliferative assays on melanoma cells suggested
that RB-TF effectively reduced cell growth compared to free RB at
the concentrations tested (25 and 50 μM). RB-TF could potentially
increase selectivity toward cancer cells. Considering the outcomes
of the characterization and cytotoxicity studies performed on RB-TF,
we conclude that RB-TF represents a valid potential alternative tool
to fight against primary melanoma lesions via dermal delivery in the
absence of light.
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Affiliation(s)
- Sara Demartis
- Department of Chemistry and Pharmacy, University of Sassari, 07100 Sassari, Italy
| | - Giovanna Rassu
- Department of Chemistry and Pharmacy, University of Sassari, 07100 Sassari, Italy
| | - Sergio Murgia
- Department of Life and Environmental Sciences, University of Cagliari, 09042 Monserrato, Cagliari, Italy.,CSGI, Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, 50019 Sesto Fiorentino, Florence, Italy
| | - Luca Casula
- Department of Life and Environmental Sciences, University of Cagliari, 09042 Monserrato, Cagliari, Italy
| | - Paolo Giunchedi
- Department of Chemistry and Pharmacy, University of Sassari, 07100 Sassari, Italy
| | - Elisabetta Gavini
- Department of Chemistry and Pharmacy, University of Sassari, 07100 Sassari, Italy
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13
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The Effect of the Osmotically Active Compound Concentration Difference on the Passive Water and Proton Fluxes across a Lipid Bilayer. Int J Mol Sci 2021; 22:ijms222011099. [PMID: 34681757 PMCID: PMC8540289 DOI: 10.3390/ijms222011099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 11/16/2022] Open
Abstract
The molecular details of the passive water flux across the hydrophobic membrane interior are still a matter of debate. One of the postulated mechanisms is the spontaneous, water-filled pore opening, which facilitates the hydrophilic connection between aqueous phases separated by the membrane. In the paper, we provide experimental evidence showing that the spontaneous lipid pore formation correlates with the membrane mechanics; hence, it depends on the composition of the lipid bilayer and the concentration of the osmotically active compound. Using liposomes as an experimental membrane model, osmotically induced water efflux was measured with the stopped-flow technique. Shapes of kinetic curves obtained at low osmotic pressure differences are interpreted in terms of two events: the lipid pore opening and water flow across the aqueous channel. The biological significance of the dependence of the lipid pore formation on the concentration difference of an osmotically active compound was illustrated by the demonstration that osmotically driven water flow can be accompanied by the dissipation of the pH gradient. The application of the Helfrich model to describe the probability of lipid pore opening was validated by demonstrating that the probability of pore opening correlates with the membrane bending rigidity. The correlation was determined by experimentally derived bending rigidity coefficients and probabilities of lipid pores opening.
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14
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Scanavachi G, Coutinho A, Fedorov AA, Prieto M, Melo AM, Itri R. Lipid Hydroperoxide Compromises the Membrane Structure Organization and Softens Bending Rigidity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9952-9963. [PMID: 34374545 DOI: 10.1021/acs.langmuir.1c00830] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Lipid hydroperoxides are key mediators of diseases and cell death. In this work, the structural and dynamic perturbations induced by the hydroperoxidized POPC lipid (POPC-OOH) in fluid POPC membranes, at both 23 and 37 °C, were addressed using advanced small-angle X-ray scattering (SAXS) and fluorescence methodologies. Notably, SAXS reveals that the hydroperoxide group decreases the lipid bilayer bending rigidity. This alteration disfavors the bilayer stacking and increases the swelling in-between stacked bilayers. We further investigated the changes in the apolar/polar interface of hydroperoxide-containing membranes through time-resolved fluorescence/anisotropy experiments of the probe TMA-DPH and time-dependent fluorescence shifts of Laurdan. A shorter mean fluorescence lifetime for TMA-DPH was obtained in enriched POPC-OOH membranes, revealing a higher degree of hydration near the membrane interface. Moreover, a higher microviscosity near TMA-DPH and lower order are predicted for these oxidized membranes, at variance with the usual trend of variation of these two parameters. Finally, the complex relaxation process of Laurdan in pure POPC-OOH membranes also indicates a higher membrane hydration and viscosity in the close vicinity of the -OOH moiety. Altogether, our combined approach reveals that the hydroperoxide group promotes alterations in the membrane structure organization, namely, at the level of membrane order, viscosity, and bending rigidity.
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Affiliation(s)
- Gustavo Scanavachi
- Institute of Physics, University of São Paulo, São Paulo 05508-090, Brazil
| | - Ana Coutinho
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
- Dep. Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa 1749-016, Portugal
- Associate Laboratory i4HB-Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
| | - Alexander Andreevich Fedorov
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
- Associate Laboratory i4HB-Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
| | - Manuel Prieto
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
- Associate Laboratory i4HB-Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
| | - Ana M Melo
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
- Associate Laboratory i4HB-Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
| | - Rosangela Itri
- Institute of Physics, University of São Paulo, São Paulo 05508-090, Brazil
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15
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The Elucidation of the Molecular Mechanism of the Extrusion Process. MATERIALS 2021; 14:ma14154278. [PMID: 34361472 PMCID: PMC8348501 DOI: 10.3390/ma14154278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 02/02/2023]
Abstract
Extrusion is a popular method for producing homogenous population of unilamellar liposomes. The technique relies on forcing a lipid suspension through cylindrical pores in a polycarbonate membrane. The quantification of the extrusion and/or recalibration processes make possible the acquisition of experimental data, which can be correlated with the mechanical properties of the lipid bilayer. In this work, the force needed for the extrusion process was correlated with the mechanical properties of a lipid bilayer derived from other experiments. Measurements were performed using a home-made dedicated device capable of maintaining a stable volumetric flux of a liposome suspension through well-defined pores and to continuously measure the extrusion force. Based on the obtained results, the correlation between the lipid bilayer bending rigidity and extrusion force was derived. Specifically, it was found that the bending rigidity of liposomes formed from well-defined lipid mixtures agrees with data obtained by others using flicker-noise spectroscopy or micromanipulation. The other issue addressed in the presented studies was the identification of molecular mechanisms leading to the formation of unilamellar vesicles in the extrusion process. Finally, it was demonstrated that during the extrusion, lipids are not exchanged between vesicles, i.e., vesicles can divide but no membrane fusion or lipid exchange between bilayers was detected.
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16
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Bagatolli LA, Stock RP. Lipids, membranes, colloids and cells: A long view. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183684. [PMID: 34166642 DOI: 10.1016/j.bbamem.2021.183684] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 06/01/2021] [Accepted: 06/16/2021] [Indexed: 12/13/2022]
Abstract
This paper revisits long-standing ideas about biological membranes in the context of an equally long-standing, but hitherto largely unappreciated, perspective of the cell based on concepts derived from the physics and chemistry of colloids. Specifically, we discuss important biophysical aspects of lipid supramolecular structure to understand how the intracellular milieu may constrain lipid self-assembly. To this end we will develop four lines of thought: first, we will look at the historical development of the current view of cellular structure and physiology, considering also the plurality of approaches that influenced its formative period. Second, we will review recent basic research on the structural and dynamical properties of lipid aggregates as well as the role of phase transitions in biophysical chemistry and cell biology. Third, we will present a general overview of contemporary studies into cellular compartmentalization in the context of a very rich and mostly forgotten general theory of cell physiology called the Association-Induction Hypothesis, which was developed around the time that the current view of cells congealed into its present form. Fourth, we will examine some recent developments in cellular studies, mostly from our laboratory, that raise interesting issues about the dynamical aspects of cell structure and compartmentalization. We will conclude by suggesting what we consider are relevant questions about the nature of cellular processes as emergent phenomena.
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Affiliation(s)
- Luis A Bagatolli
- Instituto de Investigación Médica Mercedes y Martín Ferreyra - INIMEC (CONICET)-Universidad Nacional de Córdoba, Friuli 2434, 5016 Córdoba, Argentina; Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; MEMPHYS - International and Interdisciplinary research network, Denmark.
| | - Roberto P Stock
- MEMPHYS - International and Interdisciplinary research network, Denmark
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17
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Affiliation(s)
- Chandra Has
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
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18
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Armstrong M, Vahey MD, Hunt TP, Fletcher DA. Forming and loading giant unilamellar vesicles with acoustic jetting. BIOMICROFLUIDICS 2020; 14:064105. [PMID: 33269034 PMCID: PMC7679179 DOI: 10.1063/5.0021742] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 10/15/2020] [Indexed: 05/04/2023]
Abstract
Giant unilamellar vesicles (GUVs) are a useful platform for reconstituting and studying membrane-bound biological systems, offering reduced complexity compared to living cells. Several techniques exist to form GUVs and populate them with biomolecules of interest. However, a persistent challenge is the ability to efficiently and reliably load solutions of biological macromolecules, organelle-like membranes, and/or micrometer-scale particles with controlled stoichiometry in the encapsulated volume of GUVs. Here, we demonstrate the use of acoustic streaming from high-intensity focused ultrasound to make and load GUVs from bulk solutions, without the need for nozzles that can become clogged or otherwise alter the solution composition. In this method, a compact acoustic lens is focused on a planar lipid bilayer formed between two aqueous solutions. The actuation of a planar piezoelectric material coupled to the lens accelerates a small volume of liquid, deforming the bilayer and forming a GUV containing the solution on the transducer side of the bilayer. As demonstrated here, acoustic jetting offers an alternative method for the generation of GUVs for biological and biophysical studies.
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Affiliation(s)
- Maxim Armstrong
- Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720, USA
| | - Michael D. Vahey
- Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720, USA
| | - Thomas P. Hunt
- Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720, USA
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19
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Faizi HA, Reeves CJ, Georgiev VN, Vlahovska PM, Dimova R. Fluctuation spectroscopy of giant unilamellar vesicles using confocal and phase contrast microscopy. SOFT MATTER 2020; 16:8996-9001. [PMID: 32966528 DOI: 10.1039/d0sm00943a] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A widely used method to measure the bending rigidity of bilayer membranes is fluctuation spectroscopy, which analyses the thermally-driven membrane undulations of giant unilamellar vesicles recorded with either phase-contrast or confocal microscopy. Here, we analyze the fluctuations of the same vesicle using both techniques and obtain consistent values for the bending modulus. We discuss the factors that may lead to discrepancies.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA. and Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
| | - Cody J Reeves
- Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA
| | - Vasil N Georgiev
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
| | - Petia M Vlahovska
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA. and Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
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20
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De Mel JU, Gupta S, Perera RM, Ngo L, Zolnierczuk P, Bleuel M, Pingali SV, Schneider GJ. Influence of External NaCl Salt on Membrane Rigidity of Neutral DOPC Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9356-9367. [PMID: 32672981 DOI: 10.1021/acs.langmuir.0c01004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Sodium chloride (NaCl) is a very common molecule in biotic and abiotic aqueous environments. In both cases, variation of ionic strength is inevitable. In addition to the osmotic variation posed by such perturbations, the question of whether the interactions of monovalent ions Na+ and Cl-, especially with the neutral head groups of phospholipid membranes are impactful enough to change the membrane rigidity, is still not entirely understood. We investigated the dynamics of 1,2-di-(octadecenoyl)-sn-glycero-3-phosphocholine (DOPC) vesicles with zwitterionic neutral head groups in the fluid phase with increasing external salt concentration. At higher salt concentrations, we observe an increase in bending rigidity from neutron spin echo (NSE) spectroscopy and an increase in bilayer thickness from small-angle X-ray scattering (SAXS). We compared different models to distinguish membrane undulations, lipid tail motions, and the translational diffusion of the vesicles. All of the models indicate an increase in bending rigidity by a factor of 1.3-3.6. We demonstrate that even down to t > 10 ns and for Q > 0.07 Å-1, the observed NSE relaxation spectra are influenced by translational diffusion of the vesicles. For t < 5 ns, the lipid tail motion dominates the intermediate dynamic structure factor. As the salt concentration increases, this contribution diminishes. We introduced a time-dependent analysis for the bending rigidity that highlights only a limited Zilman-Granek time window in which the rigidity is physically meaningful.
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Affiliation(s)
- Judith U De Mel
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudipta Gupta
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Rasangi M Perera
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Ly Ngo
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Piotr Zolnierczuk
- Jülich Centre for Neutron Science (JCNS), Outstation at SNS, POB 2008, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Markus Bleuel
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, United States
| | - Sai Venkatesh Pingali
- Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), POB 2008, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Gerald J Schneider
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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21
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Huang M, Liang X, Zhang Z, Wang J, Fei Y, Ma J, Qu S, Mi L. Carbon Dots for Intracellular pH Sensing with Fluorescence Lifetime Imaging Microscopy. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E604. [PMID: 32218205 PMCID: PMC7221822 DOI: 10.3390/nano10040604] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 03/11/2020] [Accepted: 03/24/2020] [Indexed: 12/11/2022]
Abstract
The monitoring of intracellular pH is of great importance for understanding intracellular trafficking and functions. It has various limitations for biosensing based on the fluorescence intensity or spectra study. In this research, pH-sensitive carbon dots (CDs) were employed for intracellular pH sensing with fluorescence lifetime imaging microscopy (FLIM) for the first time. FLIM is a highly sensitive method that is used to detect a microenvironment and it can overcome the limitations of biosensing methods based on fluorescence intensity. The different groups on the CDs surfaces changing with pH environments led to different fluorescence lifetime values. The CDs aqueous solution had a gradual change from 1.6 ns to 3.7 ns in the fluorescence lifetime with a pH range of 2.6-8.6. Similar fluorescence lifetime changes were found in pH buffer-treated living cells. The detection of lysosomes, cytoplasm, and nuclei in living cells was achieved by measuring the fluorescence lifetime of CDs. In particular, a phasor FLIM analysis was used to improve the pH imaging. Moreover, the effects of the coenzymes, amino acids, and proteins on the fluorescence lifetime of CDs were examined in order to mimic the complex microenvironment inside the cells.
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Affiliation(s)
- Maojia Huang
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
| | - Xinyue Liang
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
| | - Zixiao Zhang
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
| | - Jing Wang
- State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China;
| | - Yiyan Fei
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
| | - Jiong Ma
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
- Institute of Biomedical Engineering and Technology, Academy for Engineer and Technology, Fudan University, Shanghai 200433, China
- The Multiscale Research Institute of Complex Systems (MRICS), School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Songnan Qu
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
| | - Lan Mi
- Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Green Photoelectron Platform, Fudan University, Shanghai 200433, China; (M.H.); (X.L.); (Z.Z.); (Y.F.)
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22
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23
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Dimova R. Giant Vesicles and Their Use in Assays for Assessing Membrane Phase State, Curvature, Mechanics, and Electrical Properties. Annu Rev Biophys 2019; 48:93-119. [DOI: 10.1146/annurev-biophys-052118-115342] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Giant unilamellar vesicles represent a promising and extremely useful model biomembrane system for systematic measurements of mechanical, thermodynamic, electrical, and rheological properties of lipid bilayers as a function of membrane composition, surrounding media, and temperature. The most important advantage of giant vesicles over other model membrane systems is that the membrane responses to external factors such as ions, (macro)molecules, hydrodynamic flows, or electromagnetic fields can be directly observed under the microscope. Here, we briefly review approaches for giant vesicle preparation and describe several assays used for deducing the membrane phase state and measuring a number of material properties, with further emphasis on membrane reshaping and curvature.
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Affiliation(s)
- Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
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24
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Rideau E, Wurm FR, Landfester K. Self‐Assembly of Giant Unilamellar Vesicles by Film Hydration Methodologies. ACTA ACUST UNITED AC 2019; 3:e1800324. [DOI: 10.1002/adbi.201800324] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/01/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Emeline Rideau
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Frederik R. Wurm
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
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25
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Ramakrishnan N, Bradley RP, Tourdot RW, Radhakrishnan R. Biophysics of membrane curvature remodeling at molecular and mesoscopic lengthscales. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:273001. [PMID: 29786613 PMCID: PMC6066392 DOI: 10.1088/1361-648x/aac702] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
At the micron scale, where cell organelles display an amazing complexity in their shape and organization, the physical properties of a biological membrane can be better-understood using continuum models subject to thermal (stochastic) undulations. Yet, the chief orchestrators of these complex and intriguing shapes are a specialized class of membrane associating often peripheral proteins called curvature remodeling proteins (CRPs) that operate at the molecular level through specific protein-lipid interactions. We review multiscale methodologies to model these systems at the molecular as well as at the mesoscopic and cellular scales, and also present a free energy perspective of membrane remodeling through the organization and assembly of CRPs. We discuss the morphological space of nearly planar to highly curved membranes, methods to include thermal fluctuations, and review studies that model such proteins as curvature fields to describe the emergent curved morphologies. We also discuss several mesoscale models applied to a variety of cellular processes, where the phenomenological parameters (such as curvature field strength) are often mapped to models of real systems based on molecular simulations. Much insight can be gained from the calculation of free energies of membranes states with protein fields, which enable accurate mapping of the state and parameter values at which the membrane undergoes morphological transformations such as vesiculation or tubulation. By tuning the strength, anisotropy, and spatial organization of the curvature-field, one can generate a rich array of membrane morphologies that are highly relevant to shapes of several cellular organelles. We review applications of these models to budding of vesicles commonly seen in cellular signaling and trafficking processes such as clathrin mediated endocytosis, sorting by the ESCRT protein complexes, and cellular exocytosis regulated by the exocyst complex. We discuss future prospects where such models can be combined with other models for cytoskeletal assembly, and discuss their role in understanding the effects of cell membrane tension and the mechanics of the extracellular microenvironment on cellular processes.
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Affiliation(s)
- N Ramakrishnan
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, United States of America
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26
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Petrova AB, Herold C, Petrov EP. Conformations and membrane-driven self-organization of rodlike fd virus particles on freestanding lipid membranes. SOFT MATTER 2017; 13:7172-7187. [PMID: 28930355 DOI: 10.1039/c7sm00829e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Membrane-mediated interactions and aggregation of colloidal particles adsorbed to responsive elastic membranes are challenging problems relevant for understanding the microscopic organization and dynamics of biological membranes. We experimentally study the behavior of rodlike semiflexible fd virus particles electrostatically adsorbed to freestanding cationic lipid membranes and find that their behavior can be controlled by tuning the membrane charge and ionic strength of the surrounding medium. Three distinct interaction regimes of rodlike virus particles with responsive elastic membranes can be observed. (i) A weakly charged freestanding cationic lipid bilayer in a low ionic strength medium represents a gentle quasi-2D substrate preserving the integrity, structure, and mechanical properties of the membrane-bound semiflexible fd virus, which under these conditions is characterized by a monomer length of 884 ± 4 nm and a persistence length of 2.5 ± 0.2 μm, in perfect agreement with its properties in bulk media. (ii) An increase in the membrane charge leads to the membrane-driven collapse of fd virus particles on freestanding lipid bilayers and lipid nanotubes into compact globules. (iii) When the membrane charge is low, and the mutual electrostatic repulsion of membrane-bound virus particles is screened to a considerable degree, membrane-driven self-organization of membrane-bound fd virus particles into long linear tip-to-tip aggregates showing dynamic self-assembly/disassembly and quasi-semiflexible behavior takes place. These observations are in perfect agreement with the results of recent theoretical and simulation studies predicting that membrane-mediated interactions can control the behavior of colloidal particles adsorbed on responsive elastic membranes.
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Affiliation(s)
- Anastasiia B Petrova
- Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, 82152 Martinsried, Germany.
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27
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Dynamical regimes of lipids in additivated liposomes with enhanced elasticity: A field-cycling NMR relaxometry approach. Biophys Chem 2017; 228:38-46. [DOI: 10.1016/j.bpc.2017.06.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 06/14/2017] [Accepted: 06/20/2017] [Indexed: 11/22/2022]
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28
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Piantanida L, Bolt HL, Rozatian N, Cobb SL, Voïtchovsky K. Ions Modulate Stress-Induced Nanotexture in Supported Fluid Lipid Bilayers. Biophys J 2017; 113:426-439. [PMID: 28746853 PMCID: PMC5529180 DOI: 10.1016/j.bpj.2017.05.049] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 05/22/2017] [Accepted: 05/30/2017] [Indexed: 12/13/2022] Open
Abstract
Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of ∼20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membrane’s properties on a length scale of ∼20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton.
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Affiliation(s)
- Luca Piantanida
- Department of Physics, Durham University, Durham, United Kingdom
| | - Hannah L Bolt
- Department of Chemistry, Durham University, Durham, United Kingdom
| | - Neshat Rozatian
- Department of Chemistry, Durham University, Durham, United Kingdom
| | - Steven L Cobb
- Department of Chemistry, Durham University, Durham, United Kingdom
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29
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Sodt AJ, Beaven AH, Andersen OS, Im W, Pastor RW. Gramicidin A Channel Formation Induces Local Lipid Redistribution II: A 3D Continuum Elastic Model. Biophys J 2017; 112:1198-1213. [PMID: 28355547 DOI: 10.1016/j.bpj.2017.01.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 01/11/2017] [Accepted: 01/30/2017] [Indexed: 12/20/2022] Open
Abstract
To change conformation, a protein must deform the surrounding bilayer. In this work, a three-dimensional continuum elastic model for gramicidin A in a lipid bilayer is shown to describe the sensitivity to thickness, curvature stress, and the mechanical properties of the lipid bilayer. A method is demonstrated to extract the gramicidin-lipid boundary condition from all-atom simulations that can be used in the three-dimensional continuum model. The boundary condition affects the deformation dramatically, potentially much more than typical variations in the material stiffness do as lipid composition is changed. Moreover, it directly controls the sensitivity to curvature stress. The curvature stress and hydrophobic surfaces of the all-atom and continuum models are found to be in excellent agreement. The continuum model is applied to estimate the enrichment of hydrophobically matched lipids near the channel in a mixture, and the results agree with single-channel experiments and extended molecular dynamics simulations from the companion article by Beaven et al. in this issue of Biophysical Journal.
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Affiliation(s)
- Alexander J Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
| | - Andrew H Beaven
- Department of Chemistry, The University of Kansas, Lawrence, Kansas
| | - Olaf S Andersen
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - Wonpil Im
- Department of Biological Sciences and Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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30
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Kurniawan N, van Kempen THS, Sonneveld S, Rosalina TT, Vos BE, Jansen KA, Peters GWM, van de Vosse FN, Koenderink GH. Buffers Strongly Modulate Fibrin Self-Assembly into Fibrous Networks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:6342-6352. [PMID: 28558246 PMCID: PMC5489959 DOI: 10.1021/acs.langmuir.7b00527] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/27/2017] [Indexed: 05/20/2023]
Abstract
Fibrin is a plasma protein with a central role in blood clotting and wound repair. Upon vascular injury, fibrin forms resilient fibrillar networks (clots) via a multistep self-assembly process, from monomers, to double-stranded protofibrils, to a branched network of thick fibers. In vitro, fibrin self-assembly is sensitive to physicochemical conditions like the solution pH and ionic strength, which tune the strength of the noncovalent driving forces. Here we report a surprising finding that the buffer-which is necessary to control the pH and is typically considered to be inert-also significantly influences fibrin self-assembly. We show by confocal microscopy and quantitative light scattering that various common buffering agents have no effect on the initial assembly of fibrin monomers into protofibrils but strongly hamper the subsequent lateral association of protofibrils into thicker fibers. We further find that the structural changes are independent of the molecular structure of the buffering agents as well as of the activation mechanism and even occur in fibrin networks formed from platelet-poor plasma. This buffer-mediated decrease in protofibril bundling results in a marked reduction in the permeability of fibrin networks but only weakly influences the elastic modulus of fibrin networks, providing a useful tuning parameter to independently control the elastic properties and the permeability of fibrin networks. Our work raises the possibility that fibrin assembly in vivo may be regulated by variations in the acute-phase levels of bicarbonate and phosphate, which act as physiological buffering agents of blood pH. Moreover, our findings add a new example of buffer-induced effects on biomolecular self-assembly to recent findings for a range of proteins and lipids.
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Affiliation(s)
- Nicholas
A. Kurniawan
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Thomas H. S. van Kempen
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Stijn Sonneveld
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Tilaï T. Rosalina
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Bart E. Vos
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Karin A. Jansen
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Gerrit W. M. Peters
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Frans N. van de Vosse
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Gijsje H. Koenderink
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
- E-mail:
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31
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 PMCID: PMC5303729 DOI: 10.3389/fphys.2017.00063] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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32
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 DOI: 10.3389/fphys.2017.00063/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 05/27/2023] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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33
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Measurement of the bending elastic modulus in unilamellar vesicles membranes by fast field cycling NMR relaxometry. Chem Phys Lipids 2016; 201:21-27. [DOI: 10.1016/j.chemphyslip.2016.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 09/22/2016] [Accepted: 10/31/2016] [Indexed: 01/01/2023]
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34
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Solution Asymmetry and Salt Expand Fluid-Fluid Coexistence Regions of Charged Membranes. Biophys J 2016; 110:2581-2584. [PMID: 27288275 PMCID: PMC4919722 DOI: 10.1016/j.bpj.2016.05.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 04/26/2016] [Accepted: 05/16/2016] [Indexed: 01/08/2023] Open
Abstract
Liquid-liquid phase separation in giant unilamellar vesicles (GUVs) leads to the formation of intramembrane domains. To mimic charged biological membranes, we studied phase separation and domain formation in GUVs of ternary lipid mixtures composed of egg sphingomyelin, cholesterol, and the negatively charged lipid dioleoylphosphatidylglycerol. The GUVs were exposed to solutions of sucrose and high-saline buffer. The phase diagram was determined using epifluorescence microscopy for vesicle populations with symmetric and asymmetric solution compositions across the membranes. Trans-membrane solution asymmetry was found to affect the membrane phase state. Furthermore, compared to the case of salt-free conditions, the phase diagram in the presence of high-saline buffer (both symmetrically or asymmetrically present across the membrane) was found to exhibit a significantly extended region of liquid-ordered and liquid-disordered coexistence. These observations were confirmed on single GUVs using microfluidics and confocal microscopy. Moreover, we found that the miscibility temperatures markedly increased for vesicles in the presence of symmetric and asymmetric salt solutions. Our results demonstrate a substantial effect of salt and solution asymmetry on the phase behavior of charged membranes, which has direct implications for protein adsorption onto these membranes and for the repartitioning of proteins within the membrane domains.
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35
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Maity P, Saha B, Kumar GS, Karmakar S. Effect of counterions on the binding affinity of Na+ ions with phospholipid membranes. RSC Adv 2016. [DOI: 10.1039/c6ra17056k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We have systematically investigated the effect of counterions on the interaction of the Na+ ion with phospholipid membranes using dynamic light scattering, zeta potential, isothermal titration calorimetry and fluorescence spectroscopy techniques.
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Affiliation(s)
- Pabitra Maity
- Department of Physics
- Jadavpur University
- Kolkata 700032
- India
| | - Baishakhi Saha
- Biophysical Chemistry Laboratory
- Organic and Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032
- India
| | - Gopinatha Suresh Kumar
- Biophysical Chemistry Laboratory
- Organic and Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032
- India
| | - Sanat Karmakar
- Department of Physics
- Jadavpur University
- Kolkata 700032
- India
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36
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Exploring physical stability characteristics of positively charged catanionic vesicle/DNA complexes. Colloid Polym Sci 2015. [DOI: 10.1007/s00396-015-3608-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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37
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Barriga HMG, Bazin R, Templer RH, Law RV, Ces O. Buffer-induced swelling and vesicle budding in binary lipid mixtures of dioleoylphosphatidylcholine:dioleoylphosphatidylethanolamine and dioleoylphosphatidylcholine:lysophosphatidylcholine using small-angle X-ray scattering and ³¹P static NMR. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2979-2987. [PMID: 25738977 DOI: 10.1021/la5047996] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A large variety of data exists on lipid phase behavior; however, it is mostly in nonbuffered systems over nonbiological temperature ranges. We present biophysical data on lipid mixtures of dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidylethanolamine (DOPE), and lysophosphatidylcholine (LysoPC) examining their behaviors in excess water and buffer systems over the temperature range 4-34 °C. These mixtures are commonly used to investigate the effects of spontaneous curvature on integral membrane proteins. Using small-angle X-ray scattering (SAXS) and (31)P NMR, we observed lamellar and vesicle phases, with the buffer causing an increase in the layer spacing. Increasing amounts of DOPE in a DOPC bilayer decreased the layer spacing of the mesophase, while the opposite trend was observed for increasing amounts of LysoPC. (31)P static NMR was used to analyze the DOPC:LysoPC samples to investigate the vesicle sizes present, with evidence of vesicle budding observed at LysoPC concentrations above 30 mol %. NMR line shapes were fitted using an adapted program accounting for the distortion of the lipids within the magnetic field. The distortion of the vesicle, because of magnetic susceptibility, varied with LysoPC content, and a discontinuity was found in both the water and buffer samples. Generally, the distortion increased with LysoPC content; however, at a ratio of DOPC:LysoPC 60:40, the sample showed a level of distortion of the vesicle similar to that of pure DOPC. This implies an increased flexibility in the membrane at this point. Commonly, the assumption is that for increasing LysoPC concentration there is a reduction in membrane tension, implying that estimations of membrane tension based on spontaneous curvature assumptions may not be accurate.
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Affiliation(s)
- Hanna M G Barriga
- †Department of Chemistry, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Richard Bazin
- ‡Pfizer Global Research and Development, Sandwich, Kent CT13 9NJ, United Kingdom
| | - Richard H Templer
- †Department of Chemistry, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Robert V Law
- †Department of Chemistry, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Oscar Ces
- †Department of Chemistry, Imperial College London, London, SW7 2AZ, United Kingdom
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38
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Johnson M, Seifert S, Petrache HI, Kimble-Hill AC. Phase coexistence in single-lipid membranes induced by buffering agents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9880-9885. [PMID: 25102340 PMCID: PMC4148158 DOI: 10.1021/la5018938] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 07/29/2014] [Indexed: 05/28/2023]
Abstract
Recent literature has shown that buffers affect the interaction between lipid bilayers through a mechanism that involves van der Waals forces, electrostatics, hydration forces and membrane bending rigidity. This letter shows an additional peculiar effect of buffers on the mixed chain 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayers, namely phase coexistence similar to what was reported by Rappolt et al. for alkali chlorides. The data presented suggest that one phase appears to dehydrate below the value in pure water, while the other phase swells as the concentration of buffer is increased. However, since the two phases must be in osmotic equilibrium with one another, this behavior challenges theoretical models of lipid interactions.
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Affiliation(s)
- Merrell
A. Johnson
- Department
of Physics, Indiana University−Purdue
University Indianapolis, LD 154, 402 North Blackford Street, Indianapolis, Indiana 46202, United States
| | - Soenke Seifert
- X-ray
Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Horia I. Petrache
- Department
of Physics, Indiana University−Purdue
University Indianapolis, LD 154, 402 North Blackford Street, Indianapolis, Indiana 46202, United States
| | - Ann C. Kimble-Hill
- Department
of Biochemistry and Molecular Biology, Indiana
University School of Medicine, MS 4053, 635 Barnhill Drive, Indianapolis, Indiana 46202, United States
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39
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Dimova R. Recent developments in the field of bending rigidity measurements on membranes. Adv Colloid Interface Sci 2014; 208:225-34. [PMID: 24666592 DOI: 10.1016/j.cis.2014.03.003] [Citation(s) in RCA: 326] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/28/2014] [Accepted: 03/02/2014] [Indexed: 12/19/2022]
Abstract
This review gives a brief overview of experimental approaches used to assess the bending rigidity of membranes. Emphasis is placed on techniques based on the use of giant unilamellar vesicles. We summarize the effect on the bending rigidity of membranes as a function of membrane composition, presence of various inclusions in the bilayer and molecules and ions in the bathing solutions. Examples for the impact of temperature, cholesterol, some peptides and proteins, sugars and salts are provided and the literature data are discussed critically. Future directions, open questions and possible developments in this research field are also included.
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Affiliation(s)
- Rumiana Dimova
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
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