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Gurtovenko AA, Mukhamadiarov EI, Kostritskii AY, Karttunen M. Phospholipid–Cellulose Interactions: Insight from Atomistic Computer Simulations for Understanding the Impact of Cellulose-Based Materials on Plasma Membranes. J Phys Chem B 2018; 122:9973-9981. [DOI: 10.1021/acs.jpcb.8b07765] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Andrey A. Gurtovenko
- Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect V.O. 31, St. Petersburg, 199004 Russia
| | - Evgenii I. Mukhamadiarov
- Faculty of Physics, St. Petersburg State University, Ulyanovskaya str. 3, Petrodvorets, St. Petersburg, 198504 Russia
| | - Andrei Yu. Kostritskii
- Faculty of Physics, St. Petersburg State University, Ulyanovskaya str. 3, Petrodvorets, St. Petersburg, 198504 Russia
| | - Mikko Karttunen
- Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect V.O. 31, St. Petersburg, 199004 Russia
- Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario, Canada N6A 3K7
- Department of Applied Mathematics, The University of Western Ontario, 1151 Richmond Street, London, Ontario, Canada N6A 5B7
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Kostritskii AY, Tolmachev DA, Lukasheva NV, Gurtovenko AA. Molecular-Level Insight into the Interaction of Phospholipid Bilayers with Cellulose. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12793-12803. [PMID: 29040801 DOI: 10.1021/acs.langmuir.7b02297] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Molecular-level insight into the interactions of phospholipid molecules with cellulose is crucial for the development of novel cellulose-based materials for wound dressing. Here we employ the state-of-the-art computer simulations to unlock for the first time the molecular mechanisms behind such interactions. To this end, we performed a series of atomic-scale molecular dynamics simulations of phospholipid bilayers on a crystalline cellulose support at various hydration levels of the bilayer leaflets next to the cellulose surface. Our findings clearly demonstrate the existence of strong interactions between polar lipid head groups and the hydrophilic surface of a cellulose crystal. We identified two major types of interactions between phospholipid molecules and cellulose chains: (i) direct attractive interactions between lipid choline groups and oxygens of hydroxyl (hydroxymethyl) groups of cellulose and (ii) hydrogen bonding between phosphate groups of lipids and cellulose's hydroxymethyl/hydroxyl groups. When the hydration level of the interfacial bilayer/support region is low, these interactions lead to a pronounced asymmetry in the properties of the opposite bilayer leaflets. In particular, the mass density profiles of the proximal leaflets are split into two peaks and lipid head groups become more horizontally oriented with respect to the bilayer surface. Furthermore, the lateral mobility of lipids in the leaflets next to the cellulose surface is found to slow down considerably. Most of these cellulose-induced effects are likely due to hydrogen bonding between lipid phosphate groups and hydroxymethyl/hydroxyl groups of cellulose: the lipid phosphate groups are pulled toward the water/lipid interface due to the formation of hydrogen bonds. Overall, our findings shed light on the molecular details of the interactions between phospholipid bilayers and cellulose nanocrystals and can be used for identifying possible strategies for improving the properties of cellulose-based dressing materials via, e.g., chemical modification of their surface.
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Affiliation(s)
- Andrei Yu Kostritskii
- Faculty of Physics, St. Petersburg State University , Ulyanovskaya str. 3, Petrodvorets, St. Petersburg, 198504 Russia
| | - Dmitry A Tolmachev
- Institute of Macromolecular Compounds, Russian Academy of Sciences , Bolshoi Prospect V.O.31, St. Petersburg, 199004 Russia
| | - Natalia V Lukasheva
- Institute of Macromolecular Compounds, Russian Academy of Sciences , Bolshoi Prospect V.O.31, St. Petersburg, 199004 Russia
| | - Andrey A Gurtovenko
- Institute of Macromolecular Compounds, Russian Academy of Sciences , Bolshoi Prospect V.O.31, St. Petersburg, 199004 Russia
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Kalli AC, Rog T, Vattulainen I, Campbell ID, Sansom MSP. The Integrin Receptor in Biologically Relevant Bilayers: Insights from Molecular Dynamics Simulations. J Membr Biol 2016; 250:337-351. [PMID: 27465729 PMCID: PMC5579164 DOI: 10.1007/s00232-016-9908-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/25/2016] [Indexed: 11/27/2022]
Abstract
Integrins are heterodimeric (αβ) cell surface receptors that are potential therapeutic targets for a number of diseases. Despite the existence of structural data for all parts of integrins, the structure of the complete integrin receptor is still not available. We have used available structural data to construct a model of the complete integrin receptor in complex with talin F2-F3 domain. It has been shown that the interactions of integrins with their lipid environment are crucial for their function but details of the integrin/lipid interactions remain elusive. In this study an integrin/talin complex was inserted in biologically relevant bilayers that resemble the cell plasma membrane containing zwitterionic and charged phospholipids, cholesterol and sphingolipids to study the dynamics of the integrin receptor and its effect on bilayer structure and dynamics. The results of this study demonstrate the dynamic nature of the integrin receptor and suggest that the presence of the integrin receptor alters the lipid organization between the two leaflets of the bilayer. In particular, our results suggest elevated density of cholesterol and of phosphatidylserine lipids around the integrin/talin complex and a slowing down of lipids in an annulus of ~30 Å around the protein due to interactions between the lipids and the integrin/talin F2-F3 complex. This may in part regulate the interactions of integrins with other related proteins or integrin clustering thus facilitating signal transduction across cell membranes.
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Affiliation(s)
- Antreas C Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Tomasz Rog
- Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland
- MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark, 5230, Odense M, Denmark
| | - Iain D Campbell
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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Duro N, Gjika M, Siddiqui A, Scott HL, Varma S. POPC Bilayers Supported on Nanoporous Substrates: Specific Effects of Silica-Type Surface Hydroxylation and Charge Density. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6766-6774. [PMID: 27283467 DOI: 10.1021/acs.langmuir.6b01155] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Recent advances in nanotechnology bring to the forefront a new class of extrinsic constraints for remodeling lipid bilayers. In this next-generation technology, membranes are supported over nanoporous substrates. The nanometer-sized pores in the substrate are too small for bilayers to follow the substrate topology; consequently, the bilayers hang over the pores. Experiments demonstrate that nanoporous substrates remodel lipid bilayers differently from continuous substrates. The underlying molecular mechanisms, however, remain largely undetermined. Here we use molecular dynamics (MD) simulations to probe the effects of silica-type hydroxylation and charge densities on adsorbed palmitoyl-oleoylphosphatidylcholine (POPC) bilayers. We find that a 50% porous substrate decorated with a surface density of 4.6 hydroxyls/nm(2) adsorbs a POPC bilayer at a distance of 4.5 Å, a result consistent with neutron reflectivity experiments conducted on topologically similar silica constructs under highly acidic conditions. Although such an adsorption distance suggests that the interaction between the bilayer and the substrate will be buffered by water molecules, we find that the substrate does interact directly with the bilayer. The substrate modifies several properties of the bilayer-it dampens transverse lipid fluctuations, reduces lipid diffusion rates, and modifies transverse charge densities significantly. Additionally, it affects lipid properties differently in the two leaflets. Compared to substrates functionalized with sparser surface hydroxylation densities, this substrate adheres to bilayers at smaller distances and also remodels POPC more extensively, suggesting a direct correspondence between substrate hydrophilicity and membrane properties. A partial deprotonation of surface hydroxyls, as expected of a silica substrate under mildly acidic conditions, however, produces an inverse effect: it increases the substrate-bilayer distance, which we attribute to the formation of an electric double layer over the negatively charged substrate, and restores, at least partially, leaflet asymmetry and headgroup orientations. Overall, this study highlights the intrinsic complexity of lipid-substrate interactions and suggests the prospect of making two surface attributes-dipole densities and charge densities-work antagonistically toward remodeling lipid bilayer properties.
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Affiliation(s)
- Nalvi Duro
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States
| | - Marion Gjika
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States
| | - Ahnaf Siddiqui
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States
| | - H Larry Scott
- Department of Physics, Illinois Institute of Technology , Chicago, Illinois 60616, United States
| | - Sameer Varma
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States
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Varma S, Botlani M, Hammond JR, Scott HL, Orgel JPRO, Schieber JD. Effect of intrinsic and extrinsic factors on the simulated D-band length of type I collagen. Proteins 2015. [PMID: 26214145 DOI: 10.1002/prot.24864] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A signature feature of collagen is its axial periodicity visible in TEM as alternating dark and light bands. In mature, type I collagen, this repeating unit, D, is 67 nm long. This periodicity reflects an underlying packing of constituent triple-helix polypeptide monomers wherein the dark bands represent gaps between axially adjacent monomers. This organization is visible distinctly in the microfibrillar model of collagen obtained from fiber diffraction. However, to date, no atomistic simulations of this diffraction model under zero-stress conditions have reported a preservation of this structural feature. Such a demonstration is important as it provides the baseline to infer response functions of physiological stimuli. In contrast, simulations predict a considerable shrinkage of the D-band (11-19%). Here we evaluate systemically the effect of several factors on D-band shrinkage. Using force fields employed in previous studies we find that irrespective of the temperature/pressure coupling algorithms, assumed salt concentration or hydration level, and whether or not the monomers are cross-linked, the D-band shrinks considerably. This shrinkage is associated with the bending and widening of individual monomers, but employing a force field whose backbone dihedral energy landscape matches more closely with our computed CCSD(T) values produces a small D-band shrinkage of < 3%. Since this force field also performs better against other experimental data, it appears that the large shrinkage observed in earlier simulations is a force-field artifact. The residual shrinkage could be due to the absence of certain atomic-level details, such as glycosylation sites, for which we do not yet have suitable data.
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Affiliation(s)
- Sameer Varma
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida, 33620
| | - Mohsen Botlani
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida, 33620
| | | | - H Larry Scott
- Department of Physics, Illinois Institute of Technology, Chicago, Illinois, 60616
| | - Joseph P R O Orgel
- Department of Physics, Illinois Institute of Technology, Chicago, Illinois, 60616.,Department of Biology, Illinois Institute of Technology, Chicago, Illinois, 60616.,Department of Bioengineering, Illinois Institute of Technology, Chicago, Illinois, 60616
| | - Jay D Schieber
- Department of Physics, Illinois Institute of Technology, Chicago, Illinois, 60616.,Department of Chemical and Biological Engineering, Illinois Institute of Technology, Chicago, Ilinois, 60616
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Sun J, Jakobsson E, Wang Y, Brinker CJ. Nanoporous silica-based protocells at multiple scales for designs of life and nanomedicine. Life (Basel) 2015; 5:214-29. [PMID: 25607812 PMCID: PMC4390849 DOI: 10.3390/life5010214] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/29/2014] [Accepted: 01/06/2015] [Indexed: 11/16/2022] Open
Abstract
Various protocell models have been constructed de novo with the bottom-up approach. Here we describe a silica-based protocell composed of a nanoporous amorphous silica core encapsulated within a lipid bilayer built by self-assembly that provides for independent definition of cell interior and the surface membrane. In this review, we will first describe the essential features of this architecture and then summarize the current development of silica-based protocells at both micro- and nanoscale with diverse functionalities. As the structure of the silica is relatively static, silica-core protocells do not have the ability to change shape, but their interior structure provides a highly crowded and, in some cases, authentic scaffold upon which biomolecular components and systems could be reconstituted. In basic research, the larger protocells based on precise silica replicas of cells could be developed into geometrically realistic bioreactor platforms to enable cellular functions like coupled biochemical reactions, while in translational research smaller protocells based on mesoporous silica nanoparticles are being developed for targeted nanomedicine. Ultimately we see two different motivations for protocell research and development: (1) to emulate life in order to understand it; and (2) to use biomimicry to engineer desired cellular interactions.
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Affiliation(s)
- Jie Sun
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Eric Jakobsson
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Yingxiao Wang
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA.
| | - C Jeffrey Brinker
- Department of Chemical and Nuclear Engineering, Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NW 87106, USA.
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7
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Dutta P, Botlani M, Varma S. Water Dynamics at Protein–Protein Interfaces: Molecular Dynamics Study of Virus–Host Receptor Complexes. J Phys Chem B 2014; 118:14795-807. [DOI: 10.1021/jp5089096] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Kendall EL, Ngassam VN, Gilmore SF, Brinker CJ, Parikh AN. Lithographically defined macroscale modulation of lateral fluidity and phase separation realized via patterned nanoporous silica-supported phospholipid bilayers. J Am Chem Soc 2013; 135:15718-21. [PMID: 24111800 DOI: 10.1021/ja408434r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Using lithographically defined surfaces consisting of hydrophilic patterns of nanoporous and nonporous (bulk) amorphous silica, we show that fusion of small, unilamellar lipid vesicles produces a single, contiguous, fluid bilayer phase experiencing a predetermined pattern of interfacial interactions. Although long-range lateral fluidity of the bilayer, characterized by fluorescence recovery after photobleaching, indicates a nominally single average diffusion constant, fluorescence microscopy-based measurements of temperature-dependent onset of fluidity reveals a locally enhanced fluidity for bilayer regions supported on nanoporous silica in the vicinity of the fluid-gel transition temperature. Furthermore, thermally quenching lipid bilayers composed of a binary lipid mixture below its apparent miscibility transition temperature induces qualitatively different lateral phase separation in each region of the supported bilayer: The nanoporous substrate produces large, microscopic domains (and domain-aggregates), whereas surface texture characterized by much smaller domains and devoid of any domain-aggregates appears on bulk glass-supported regions of the single-lipid bilayer. Interestingly, lateral distribution of the constituent molecules also reveals an enrichment of gel-phase lipids over nanoporous regions, presumably as a consequence of differential mobilities of constituent lipids across the topographic bulk/nanoporous boundary. Together, these results reveal that subtle local variations in constraints imposed at the bilayer interface, such as by spatial variations in roughness and substrate adhesion, can give rise to significant differences in macroscale biophysical properties of phospholipid bilayers even within a single, contiguous phase.
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Affiliation(s)
- Eric L Kendall
- Departments of Chemical Engineering and Materials Science, ‡Biomedical Engineering, and §Applied Science, University of California , Davis, California 95616, United States
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Hardy GJ, Nayak R, Zauscher S. Model cell membranes: Techniques to form complex biomimetic supported lipid bilayers via vesicle fusion. Curr Opin Colloid Interface Sci 2013; 18:448-458. [PMID: 24031164 DOI: 10.1016/j.cocis.2013.06.004] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vesicle fusion has long provided an easy and reliable method to form supported lipid bilayers (SLBs) from simple, zwitterionic vesicles on siliceous substrates. However, for complex compositions, such as vesicles with high cholesterol content and multiple lipid types, the energy barrier for the vesicle-to-bilayer transition is increased or the required vesicle-vesicle and vesicle-substrate interactions are insufficient for vesicle fusion. Thus, for vesicle compositions that more accurately mimic native membranes, vesicle fusion often fails to form SLBs. In this paper, we review three approaches to overcome these barriers to form complex, biomimetic SLBs via vesicle fusion: (i) optimization of experimental conditions (e.g., temperature, buffer ionic strength, osmotic stress, cation valency, and buffer pH), (ii) α-helical (AH) peptide-induced vesicle fusion, and (iii) bilayer edge-induced vesicle fusion. AH peptide-induced vesicle fusion can form complex SLBs on multiple substrate types without the use of additional equipment. Bilayer edge-induced vesicle fusion uses microfluidics to form SLBs from vesicles with complex composition, including vesicles derived from native cell membranes. Collectively, this review introduces vesicle fusion techniques that can be generalized for many biomimetic vesicle compositions and many substrate types, and thus will aid efforts to reliably create complex SLB platforms on a range of substrates.
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Affiliation(s)
- Gregory J Hardy
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, NC 27708, USA. ; Tel: +1 (919) 660-5360
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Leighty RE, Varma S. Quantifying Changes in Intrinsic Molecular Motion Using Support Vector Machines. J Chem Theory Comput 2013; 9:868-75. [DOI: 10.1021/ct300694e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Ralph E Leighty
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States
| | - Sameer Varma
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida , Tampa, Florida 33620, United States.,Department of Physics, University of South Florida , Tampa, Florida 33620, United States.,Institute of Pure and Applied Mathematics, University of California at Los Angeles , Los Angeles, California 90095, United States
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