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Socrier L, Steinem C. Pore-spanning membranes as a tool to investigate lateral lipid membrane heterogeneity. Methods Enzymol 2024; 700:455-483. [PMID: 38971610 DOI: 10.1016/bs.mie.2024.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2024]
Abstract
Over the years, it has become more and more obvious that lipid membranes show a very complex behavior. This behavior arises in part from the large number of different kinds of lipids and proteins and how they dynamically interact with each other. In vitro studies using artificial membrane systems have shed light on the heterogeneity based on lipid-lipid interactions in multicomponent bilayer mixtures. Inspired by the raft hypothesis, the coexistence of liquid-disordered (ld) and liquid-ordered (lo) phases has drawn much attention. It was shown that ternary lipid mixtures containing low- and high-melting temperature lipids and cholesterol can phase separate into a lo phase enriched in the high-melting lipids and cholesterol and a ld phase enriched in the low-melting lipids. Depending on the model membrane system under investigation, different domain sizes, shapes, and mobilities have been found. Here, we describe how to generate phase-separated lo/ld phases in model membrane systems termed pore-spanning membranes (PSMs). These PSMs are prepared on porous silicon substrates with pore sizes in the micrometer regime. A proper functionalization of the top surface of the substrates is required to achieve the spreading of giant unilamellar vesicles (GUVs) to obtain PSMs. Starting with lo/ld phase-separated GUVs lead to membrane heterogeneities in the PSMs. Depending on the functionalization strategy of the top surface of the silicon substrate, different membrane heterogeneities are observed in the PSMs employing fluorescence microscopy. A quantitative analysis of the heterogeneity as well as the dynamics of the lipid domains is described.
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Affiliation(s)
- Larissa Socrier
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Claudia Steinem
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany; Institute of Organic and Biomolecular Chemistry, Georg-August Universität, Göttingen, Germany.
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2
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Díaz-Rodríguez TG, Celaya CA, Muñiz J. First principles study on the potential of functionalized porous silicon to capture adverse agents to human health: The role played by the interface interactions. Biophys Chem 2023; 292:106910. [PMID: 36327692 DOI: 10.1016/j.bpc.2022.106910] [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: 08/23/2022] [Revised: 10/10/2022] [Accepted: 10/16/2022] [Indexed: 11/06/2022]
Abstract
Porous Silicon (PSi) is an ideal material to build biosensors due to its large surface area and biocompatibility. However, it lacks of selectivity. By adhering bilayer lipids, active sites are added for vital biochemical processes. Such processes are promoted by different proteins, which aid to detect pollutants and drugs, among other. The present work is a systematic theoretical study at the density functional theory level on PSi models, functionalized with H and OH. Several concentrations of such functional groups were assessed at the pores to elucidate the reactivity via Fukui indexes of electrophilic and nucleophilic attack. The 1,2-dimyristoyl-sn-glycero-3-phosphocholine(DMPC) lipid was used as a probe system to interact with the PSi. The attraction was evaluated as electrostatic with a van der Waals contribution. The adsorption was highly selective to the degree of functionalization at the pore. The PSi facets (100) and (001) showed different mechanisms of interaction with the DMPC lipid. The theoretical absorption spectra addressed that the DMPC lipid could be identified with intensity variations coming from the degree of functionalization at the pore, which may be further rationalized experimentally. The present methodology may aid to tailor novel materials to capture and identify adverse agents present in the environment.
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Affiliation(s)
- T G Díaz-Rodríguez
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Priv. Xochicalco s/n, Col. Centro, Temixco CP 62580, Morelos, Mexico.
| | - Christian A Celaya
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Priv. Xochicalco s/n, Col. Centro, Temixco CP 62580, Morelos, Mexico
| | - Jesús Muñiz
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Priv. Xochicalco s/n, Col. Centro, Temixco CP 62580, Morelos, Mexico.
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Bompard J, Maniti O, Aboukhachfe R, Ausserre D, Girard-Egrot A. BALM: Watching the Formation of Tethered Bilayer Lipid Membranes with Submicron Lateral Resolution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9457-9471. [PMID: 34324820 DOI: 10.1021/acs.langmuir.1c01184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Tethered bilayer lipid membranes (tBLMs) are artificial membranes largely used for the in situ study of biological membranes and membrane-associated proteins. To date, the formation of these membranes was essentially monitored by surface averaging techniques like surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D), which cannot provide both local and real-time information in a single approach. Here, we report an original application of backside absorbing layer microscopy (BALM), a novel white-light wide-field optical microscopy, to study tBLMs. Thanks to the combination of sensitivity and resolution, BALM not only allowed the real-time quantitative monitoring of tBLM formation but also enabled the high-resolution visualization of local fluxes and matter exchanges taking place at each step of the process. Quantitative BALM measurements of the final layer thickness, reproduced in parallel with SPR, were consistent with the achievement of a continuous lipid bilayer. This finding was confirmed by BALM imaging, which additionally revealed the heterogeneity of the bilayer during its formation. While established real-time techniques, like SPR or QCM-D, view the surface as homogeneous, BALM showed the presence of surface patterns appearing in the first step of the tBLM formation process and governing subsequent matter adsorption or desorption steps. Finally, matter fluxes persisting even after rinsing at the end of the tBLM formation demonstrated the lasting presence of dispersed vesicular pockets with laterally fluctuating positions over the final single and continuous lipid bilayer. These new mechanistic insights into the tBLM formation process demonstrate the great potential of BALM in the study of complex biological systems.
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Affiliation(s)
- J Bompard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR 5246, GEMBAS Team, Lederer building, 1 rue Victor Grignard, F-69622 Villeurbanne, France
| | - O Maniti
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR 5246, GEMBAS Team, Lederer building, 1 rue Victor Grignard, F-69622 Villeurbanne, France
| | - R Aboukhachfe
- Lebanese University, Faculty of Technology, Hisbe Street, Saida, Lebanon
| | - D Ausserre
- Institut Molecules & Matériaux du Mans, IMMM CNRS UMR 6283, Le Mans Université, Avenue Olivier Messiaen, 72085 Le Mans, France
| | - A Girard-Egrot
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR 5246, GEMBAS Team, Lederer building, 1 rue Victor Grignard, F-69622 Villeurbanne, France
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4
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Why Do Tethered-Bilayer Lipid Membranes Suit for Functional Membrane Protein Reincorporation? APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11114876] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Membrane proteins (MPs) are essential for cellular functions. Understanding the functions of MPs is crucial as they constitute an important class of drug targets. However, MPs are a challenging class of biomolecules to analyze because they cannot be studied outside their native environment. Their structure, function and activity are highly dependent on the local lipid environment, and these properties are compromised when the protein does not reside in the cell membrane. Mammalian cell membranes are complex and composed of different lipid species. Model membranes have been developed to provide an adequate environment to envisage MP reconstitution. Among them, tethered-Bilayer Lipid Membranes (tBLMs) appear as the best model because they allow the lipid bilayer to be decoupled from the support. Thus, they provide a sufficient aqueous space to envisage the proper accommodation of large extra-membranous domains of MPs, extending outside. Additionally, as the bilayer remains attached to tethers covalently fixed to the solid support, they can be investigated by a wide variety of surface-sensitive analytical techniques. This review provides an overview of the different approaches developed over the last two decades to achieve sophisticated tBLMs, with a more and more complex lipid composition and adapted for functional MP reconstitution.
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Rybenkov VV, Zgurskaya HI, Ganguly C, Leus IV, Zhang Z, Moniruzzaman M. The Whole Is Bigger than the Sum of Its Parts: Drug Transport in the Context of Two Membranes with Active Efflux. Chem Rev 2021; 121:5597-5631. [PMID: 33596653 DOI: 10.1021/acs.chemrev.0c01137] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cell envelope plays a dual role in the life of bacteria by simultaneously protecting it from a hostile environment and facilitating access to beneficial molecules. At the heart of this ability lie the restrictive properties of the cellular membrane augmented by efflux transporters, which preclude intracellular penetration of most molecules except with the help of specialized uptake mediators. Recently, kinetic properties of the cell envelope came into focus driven on one hand by the urgent need in new antibiotics and, on the other hand, by experimental and theoretical advances in studies of transmembrane transport. A notable result from these studies is the development of a kinetic formalism that integrates the Michaelis-Menten behavior of individual transporters with transmembrane diffusion and offers a quantitative basis for the analysis of intracellular penetration of bioactive compounds. This review surveys key experimental and computational approaches to the investigation of transport by individual translocators and in whole cells, summarizes key findings from these studies and outlines implications for antibiotic discovery. Special emphasis is placed on Gram-negative bacteria, whose envelope contains two separate membranes. This feature sets these organisms apart from Gram-positive bacteria and eukaryotic cells by providing them with full benefits of the synergy between slow transmembrane diffusion and active efflux.
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Affiliation(s)
- Valentin V Rybenkov
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Chhandosee Ganguly
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Inga V Leus
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Zhen Zhang
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Mohammad Moniruzzaman
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
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Hossain M, Blanchard GJ. Ceramide-mediation of diffusion in supported lipid bilayers. Chem Phys Lipids 2021; 238:105090. [PMID: 33971138 DOI: 10.1016/j.chemphyslip.2021.105090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/09/2021] [Accepted: 05/05/2021] [Indexed: 11/30/2022]
Abstract
The fluidity and compositional heterogeneity of the mammalian plasma membrane play deterministic roles in a variety of membrane functions. Designing model bilayer systems allows for compositional control over these properties. Ceramide is a phospholipid capable of extensive headgroup-region hydrogen bonding, and we report here on the role of ceramide in planar model bilayers. We use fluorescence recovery after photobleaching (FRAP) to obtain translational diffusion constants of two chromophores in supported model bilayers composed of cholesterol, 1,2-dioleoyl-sn-phosphatidylcholine (DOPC), sphingomyelin, and ceramide. FRAP data for perylene report on the acyl chain region of the model bilayer and FRAP data for 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) sense diffusional dynamics in the bilayer headgroup region. Dynamics in the headgroup region exhibit anomalous diffusion behavior that is characteristic of spatially heterogeneous media.
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Affiliation(s)
- Masroor Hossain
- Michigan State University, Department of Chemistry, 578 S. Shaw Lane, East Lansing, MI, 48824, USA
| | - G J Blanchard
- Michigan State University, Department of Chemistry, 578 S. Shaw Lane, East Lansing, MI, 48824, USA.
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Mühlenbrock P, Sari M, Steinem C. In vitro single vesicle fusion assays based on pore-spanning membranes: merits and drawbacks. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:239-252. [PMID: 33320298 PMCID: PMC8071798 DOI: 10.1007/s00249-020-01479-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 12/22/2022]
Abstract
Neuronal fusion mediated by soluble N-ethylmaleimide-sensitive-factor attachment protein receptors (SNAREs) is a fundamental cellular process by which two initially distinct membranes merge resulting in one interconnected structure to release neurotransmitters into the presynaptic cleft. To get access to the different stages of the fusion process, several in vitro assays have been developed. In this review, we provide a short overview of the current in vitro single vesicle fusion assays. Among those assays, we developed a single vesicle assay based on pore-spanning membranes (PSMs) on micrometre-sized pores in silicon, which might overcome some of the drawbacks associated with the other membrane architectures used for investigating fusion processes. Prepared by spreading of giant unilamellar vesicles with reconstituted t-SNAREs, PSMs provide an alternative tool to supported lipid bilayers to measure single vesicle fusion events by means of fluorescence microscopy. Here, we discuss the diffusive behaviour of the reconstituted membrane components as well as that of the fusing synthetic vesicles with reconstituted synaptobrevin 2 (v-SNARE). We compare our results with those obtained if the synthetic vesicles are replaced by natural chromaffin granules under otherwise identical conditions. The fusion efficiency as well as the different fusion states observable in this assay by means of both lipid mixing and content release are illuminated.
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Affiliation(s)
- Peter Mühlenbrock
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Merve Sari
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Claudia Steinem
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany.
- Max-Planck-Institute for Dynamics and Self Organization, Am Faßberg 17, 37077, Göttingen, Germany.
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8
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Sun Y, Zang X, Sun Y, Wang L, Gao Z. Lipid membranes supported by planar porous substrates. Chem Phys Lipids 2020; 228:104893. [PMID: 32097619 DOI: 10.1016/j.chemphyslip.2020.104893] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 02/10/2020] [Indexed: 12/18/2022]
Abstract
Biological membranes play key roles in cell life, but their intrinsic complexity motivated the study and development of artificial lipid membranes with the primary aim to reconstitute and understand the natural functions in vitro. Porous-supported lipid membrane (pSLM) has emerged as a flexible platform for studying the surface chemistry of the cell due to their high stability and fluidity, and their ability to study the transmembrane process of the molecules. In this review, the pSLM, for the first time, to our knowledge, was divided into three types according to the way of the porous materials support the lipid membrane, containing the lipid membrane on the pores of the porous materials, the lipid membrane on both sides of the porous materials, the lipid membrane in the pores of the porous materials. All of these pSLMs were systematically elaborated from several aspects, including the substrates, formation, and characterization. Meanwhile, the advantages and disadvantages of each model membranes were summarized. Finally, suggestions for selecting appropriate pSLM and future directions in this area are discussed.
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Affiliation(s)
- Yanping Sun
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Xianghuan Zang
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Yongjun Sun
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Long Wang
- State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Department of Family and Consumer Sciences, California State University, Long Beach, CA, 90840, USA.
| | - Zibin Gao
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China.
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9
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Cao Y, Dong Y, Chou JJ. Structural and Functional Properties of Viral Membrane Proteins. ADVANCES IN MEMBRANE PROTEINS 2018. [PMCID: PMC7122571 DOI: 10.1007/978-981-13-0532-0_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Viruses have developed a large variety of transmembrane proteins to carry out their infectious cycles. Some of these proteins are simply anchored to membrane via transmembrane helices. Others, however, adopt more interesting structures to perform tasks such as mediating membrane fusion and forming ion-permeating channels. Due to the dynamic or plastic nature shown by many of the viral membrane proteins, structural and mechanistic understanding of these proteins has lagged behind their counterparts in prokaryotes and eukaryotes. This chapter provides an overview of the use of NMR spectroscopy to unveil the transmembrane and membrane-proximal regions of viral membrane proteins, as well as their interactions with potential therapeutics.
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Affiliation(s)
- Yu Cao
- Institute of Precision Medicine, The Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Rosilio V. How Can Artificial Lipid Models Mimic the Complexity of Molecule–Membrane Interactions? ACTA ACUST UNITED AC 2018. [DOI: 10.1016/bs.abl.2017.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Chadli M, Rebaud S, Maniti O, Tillier B, Cortès S, Girard-Egrot A. New Tethered Phospholipid Bilayers Integrating Functional G-Protein-Coupled Receptor Membrane Proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:10385-10401. [PMID: 28877444 DOI: 10.1021/acs.langmuir.7b01636] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Membrane proteins exhibiting extra- and intracellular domains require an adequate near-native lipid platform for their functional reconstitution. With this aim, we developed a new technology enabling the formation of a peptide-tethered bilayer lipid membrane (pep-tBLM), a lipid bilayer grafted onto peptide spacers, by way of a metal-chelate interaction. To this end, we designed an original peptide spacer derived from the natural α-laminin thiopeptide (P19) possessing a cysteine residue in the N-terminal extremity for grafting onto gold and a C-terminal extremity modified by four histidine residues (P19-4H). In the presence of nickel, the use of this anchor allowed us to bind liposomes of variable compositions containing a 2% molar ratio of a chelating lipid, 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl] so-called DOGS-NTA, and to form the planar bilayer by triggering liposome fusion by an α-helical (AH) peptide derived from the N-terminus of the hepatitis C virus NS5A protein. The formation of pep-tBLMs was characterized by surface plasmon resonance imaging (SPRi), and their continuity, fluidity, and homogeneity were demonstrated by fluorescence recovery after photobleaching (FRAP), with a diffusion coefficient of 2.5 × 10-7 cm2/s, and atomic force microscopy (AFM). By using variable lipid compositions including phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol 4,5-bisphosphate (PIP2), sphingomyelin (SM), phosphatidic acid (PA), and cholesterol (Chol) in various ratios, we show that the membrane can be formed independently from the lipid composition. We made the most of this advantage to reincorporate a transmembrane protein in an adapted complex lipid composition to ensure its functional reinsertion. For this purpose, a cell-free expression system was used to produce proteoliposomes expressing the functional C-X-C motif chemokine receptor 4 (CXCR4), a seven-transmembrane protein belonging to the large superfamily of G-protein-coupled receptors (GPCRs). We succeeded in reinserting CXCR4 in pep-tBLMs formed on P19-4H by the fusion of tethered proteoliposomes. AFM and FRAP characterization allowed us to show that pep-tBLMs inserting CXCR4 remained fluid, homogeneous, and continuous. The value of the diffusion coefficient determined in the presence of reinserted CXCR4 was 2 × 10-7 cm2/s. Ligand binding assays using a synthetic CXCR4 antagonist, T22 ([Tyr5,12, Lys7]-polyphemusin II), revealed that CXCR4 can be reinserted in pep-tBLMs with functional folding and orientation. This new approach represents a method of choice for investigating membrane protein reincorporation and a promising way of creating a new generation of membrane biochips adapted for screening agonists or antagonists of transmembrane proteins.
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Affiliation(s)
- Meriem Chadli
- Univ Lyon, Université Lyon 1 , Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR CNRS 5246, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne, France
- Synthelis, Biopolis, 5, Avenue du Grand Sablon, 38700 La Tronche, France
| | - Samuel Rebaud
- Univ Lyon, Université Lyon 1 , Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR CNRS 5246, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne, France
| | - Ofelia Maniti
- Univ Lyon, Université Lyon 1 , Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR CNRS 5246, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne, France
| | - Bruno Tillier
- Synthelis, Biopolis, 5, Avenue du Grand Sablon, 38700 La Tronche, France
| | - Sandra Cortès
- Synthelis, Biopolis, 5, Avenue du Grand Sablon, 38700 La Tronche, France
| | - Agnès Girard-Egrot
- Univ Lyon, Université Lyon 1 , Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, ICBMS, UMR CNRS 5246, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne, France
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12
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Lettieri R, Di Giorgio F, Colella A, Magnusson R, Bjorefors F, Placidi E, Palleschi A, Venanzi M, Gatto E. DPPTE Thiolipid Self-Assembled Monolayer: A Critical Assay. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:11560-11572. [PMID: 27689538 DOI: 10.1021/acs.langmuir.6b01912] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Supported lipid membranes represent an elegant way to design a fluid interface able to mimic the physicochemical properties of biological membranes, with potential biotechnological applications. In this work, a diacyl phospholipid, the 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE), functionalized with a thiol group, was immobilized on a gold surface. In this molecule, the thiol group, responsible for the Au-S bond (45 kJ/mol) is located on the phospholipid polar head, letting the hydrophobic chain protrude from the film. This system is widely used in the literature but is no less challenging, since its characterization is not complete, as several discordant data have been obtained. In this work, the film was characterized by cyclic voltammetry blocking experiments, to verify the SAM formation, and by reductive desorption measurements, to estimate the molecular density of DPPTE on the gold surface. This value has been compared to that obtained by quartz crystal microbalance measurements. Ellipsometry and impedance spectroscopy measurements have been performed to obtain information about the monolayer thickness and capacitance. The film morphology was investigated by atomic force microscopy. Finally, Monte Carlo simulations were carried out, in order to gain molecular information about the morphologies of the DPPTE SAM and compare them to the experimental results. We demonstrate that DPPTE molecules, incubated 18 h below the phase transition temperature (T = 41.1 ± 0.4 °C) in ethanol solution, are able to form a self-assembled monolayer on the gold surface, with domain structures of different order, which have never been reported before. Our results make possible rationalization of the scattered results so far obtained on this system, giving a new insight into the formation of phospholipids SAMs on a gold surface.
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Affiliation(s)
- Raffaella Lettieri
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Floriana Di Giorgio
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Alessandra Colella
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Roger Magnusson
- Department of Physics, Chemistry and Biology (IFM), University of Linköping , 581 83 Linköping, Sweden
| | - Fredrik Bjorefors
- Ångström Laboratory, Department of Chemistry, Uppsala University , Box 538, SE-75121 Uppsala, Sweden
| | - Ernesto Placidi
- Institute of Structure of Matter, CNR, Department of Physics, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Antonio Palleschi
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Mariano Venanzi
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
| | - Emanuela Gatto
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata , 00133 Rome, Italy
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13
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Ulmschneider JP, Ulmschneider MB. Folding Simulations of the Transmembrane Helix of Virus Protein U in an Implicit Membrane Model. J Chem Theory Comput 2015; 3:2335-46. [PMID: 26636223 DOI: 10.1021/ct700103k] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vpu is an 81-amino-acid auxiliary membrane protein encoded by human immunodeficiency virus type 1 (HIV-1). One of its roles is to amplify viral release by self-assembling in homo-oligomers to form functional water-filled pores enabling the flux of ions across the membrane. Various NMR and CD studies have shown that the transmembrane domain of Vpu has a helical conformation. With a recently developed implicit membrane model and an efficient Monte Carlo (MC) algorithm using concerted backbone rotations, we simulate the folding of the transmembrane domain of Vpu at atomic resolution. The implicit membrane environment is based on the generalized Born theory and enables very long time scale events, such as folding to be observed using detailed all-atom representation of the protein. Such studies are currently computationally unfeasible with fully explicit lipid bilayer molecular dynamics simulations. The correct helical transmembrane structure of Vpu is predicted from extended conformations and remains stably inserted. Tilt and kink angles agree well with experimental estimates from NMR measurements. The experimentally observed change in tilt angle in membranes of varying hydrophobic width is accurately reproduced. The extensive simulation of a pentamer of the Vpu transmembrane domain in the implicit membrane gives results similar to the ones reported previously for fully explicit bilayer simulations.
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Affiliation(s)
- Jakob P Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
| | - Martin B Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
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15
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Schubert T, Römer W. How synthetic membrane systems contribute to the understanding of lipid-driven endocytosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015. [PMID: 26211452 DOI: 10.1016/j.bbamcr.2015.07.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Synthetic membrane systems, such as giant unilamellar vesicles and solid supported lipid bilayers, have widened our understanding of biological processes occurring at or through membranes. Artificial systems are particularly suited to study the inherent properties of membranes with regard to their components and characteristics. This review critically reflects the emerging molecular mechanism of lipid-driven endocytosis and the impact of model membrane systems in elucidating the complex interplay of biomolecules within this process. Lipid receptor clustering induced by binding of several toxins, viruses and bacteria to the plasma membrane leads to local membrane bending and formation of tubular membrane invaginations. Here, lipid shape, and protein structure and valency are the essential parameters in membrane deformation. Combining observations of complex cellular processes and their reconstitution on minimal systems seems to be a promising future approach to resolve basic underlying mechanisms. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Thomas Schubert
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Schänzlestraβe 18, 79104 Freiburg, Germany.
| | - Winfried Römer
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Schänzlestraβe 18, 79104 Freiburg, Germany.
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16
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Schwenen LLG, Hubrich R, Milovanovic D, Geil B, Yang J, Kros A, Jahn R, Steinem C. Resolving single membrane fusion events on planar pore-spanning membranes. Sci Rep 2015; 5:12006. [PMID: 26165860 PMCID: PMC4499801 DOI: 10.1038/srep12006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/15/2015] [Indexed: 12/15/2022] Open
Abstract
Even though a number of different in vitro fusion assays have been developed to analyze protein mediated fusion, they still only partially capture the essential features of the in vivo situation. Here we established an in vitro fusion assay that mimics the fluidity and planar geometry of the cellular plasma membrane to be able to monitor fusion of single protein-containing vesicles. As a proof of concept, planar pore-spanning membranes harboring SNARE-proteins were generated on highly ordered functionalized 1.2 μm-sized pore arrays in Si3N4. Full mobility of the membrane components was demonstrated by fluorescence correlation spectroscopy. Fusion was analyzed by two color confocal laser scanning fluorescence microscopy in a time resolved manner allowing to readily distinguish between vesicle docking, intermediate states such as hemifusion and full fusion. The importance of the membrane geometry on the fusion process was highlighted by comparing SNARE-mediated fusion with that of a minimal SNARE fusion mimetic.
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Affiliation(s)
- Lando L G Schwenen
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - Raphael Hubrich
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - Dragomir Milovanovic
- Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Burkhard Geil
- Institute for Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Jian Yang
- Leiden Institute of Chemistry - Supramolecular and Biomaterials Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Alexander Kros
- Leiden Institute of Chemistry - Supramolecular and Biomaterials Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Reinhard Jahn
- Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Claudia Steinem
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
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17
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Scott C, Griffin S. Viroporins: structure, function and potential as antiviral targets. J Gen Virol 2015; 96:2000-2027. [PMID: 26023149 DOI: 10.1099/vir.0.000201] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The channel-forming activity of a family of small, hydrophobic integral membrane proteins termed 'viroporins' is essential to the life cycles of an increasingly diverse range of RNA and DNA viruses, generating significant interest in targeting these proteins for antiviral development. Viroporins vary greatly in terms of their atomic structure and can perform multiple functions during the virus life cycle, including those distinct from their role as oligomeric membrane channels. Recent progress has seen an explosion in both the identification and understanding of many such proteins encoded by highly significant pathogens, yet the prototypic M2 proton channel of influenza A virus remains the only example of a viroporin with provenance as an antiviral drug target. This review attempts to summarize our current understanding of the channel-forming functions for key members of this growing family, including recent progress in structural studies and drug discovery research, as well as novel insights into the life cycles of many viruses revealed by a requirement for viroporin activity. Ultimately, given the successes of drugs targeting ion channels in other areas of medicine, unlocking the therapeutic potential of viroporins represents a valuable goal for many of the most significant viral challenges to human and animal health.
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Affiliation(s)
- Claire Scott
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
| | - Stephen Griffin
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
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18
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Janshoff A, Steinem C. Mechanics of lipid bilayers: What do we learn from pore-spanning membranes? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2977-83. [PMID: 26025679 DOI: 10.1016/j.bbamcr.2015.05.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 11/18/2022]
Abstract
The mechanical properties of biological membranes have become increasingly important not only from a biophysical viewpoint but also as they play a substantial role in the information transfer in cells and tissues. This minireview summarizes some of our recent understanding of the mechanical properties of artificial model membranes with particular emphasis on membranes suspending an array of pores, so called pore-spanning membranes. A theoretical description of the mechanical properties of these membranes might pave the way to biophysically describe and understand the complex behavior of native biological membranes. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Andreas Janshoff
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
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19
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Teng W, Ban C, Hahn JH. Formation of lipid bilayer membrane in a poly(dimethylsiloxane) microchip integrated with a stacked polycarbonate membrane support and an on-site nanoinjector. BIOMICROFLUIDICS 2015; 9:024120. [PMID: 26015832 PMCID: PMC4409621 DOI: 10.1063/1.4919066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/14/2015] [Indexed: 06/04/2023]
Abstract
This paper describes a new and facile approach for the formation of pore-spanning bilayer lipid membranes (BLMs) within a poly(dimethylsiloxane) (PDMS) microfluidic device. Commercially, readily available polycarbonate (PC) membranes are employed for the support of BLMs. PC sheets with 5 μm, 2 μm, and 0.4 μm pore diameters, respectively, are thermally bonded into a multilayer-stack, reducing the pore density of 0.4 μm-pore PC by a factor of 200. The BLMs on this support are considerably stable (a mean lifetime: 17 h). This multilayer-stack PC (MSPC) membrane is integrated into the PDMS chip by an epoxy bonding method developed to secure durable bonding under the use of organic solvents. The microchip has a special channel for guiding a micropipette in the proximity of the MSPC support. With this on-site injection technique, tens to hundreds of nanoliters of solutions can be directly dispensed to the support. Incorporating gramicidin ion channels into BLMs on the MSPC support has confirmed the formation of single BLMs, which is based on the observation from current signals of 20 pS conductance that is typical to single channel opening. Based on the bilayer capacitance (1.4 pF), about 15% of through pores across the MSPC membrane are estimated to be covered with BLMs.
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Affiliation(s)
- Wei Teng
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
| | - Changill Ban
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
| | - Jong Hoon Hahn
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
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20
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Wang X, Ma S, Su Y, Zhang Y, Bi H, Zhang L, Han X. High Impedance Droplet–Solid Interface Lipid Bilayer Membranes. Anal Chem 2015; 87:2094-9. [PMID: 25600185 DOI: 10.1021/ac502953v] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Xuejing Wang
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
| | - Shenghua Ma
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
| | - Yingchun Su
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
| | - Ying Zhang
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
| | - Hongmei Bi
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
| | - Lixue Zhang
- Qingdao
Key Lab of Solar Energy Utilization and Energy Storage Technology,
Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101, China
| | - Xiaojun Han
- State
Key Laboratory of Urban Water Resource and Environment, School of
Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001, China
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21
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Abstract
The current study deals with the self-assembly of phospholipids on flat supports using the Martini coarse grain model.
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Affiliation(s)
- Anil R. Mhashal
- Physical Chemistry Division
- National Chemical Laboratory
- Pune
- India
| | - Sudip Roy
- Physical Chemistry Division
- National Chemical Laboratory
- Pune
- India
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22
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Tethered bilayer lipid membranes (tBLMs): interest and applications for biological membrane investigations. Biochimie 2014; 107 Pt A:135-42. [PMID: 24998327 DOI: 10.1016/j.biochi.2014.06.021] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/25/2014] [Indexed: 01/19/2023]
Abstract
Biological membranes play a central role in the biology of the cell. They are not only the hydrophobic barrier allowing separation between two water soluble compartments but also a supra-molecular entity that has vital structural functions. Notably, they are involved in many exchange processes between the outside and inside cellular spaces. Accounting for the complexity of cell membranes, reliable models are needed to acquire current knowledge of the molecular processes occurring in membranes. To simplify the investigation of lipid/protein interactions, the use of biomimetic membranes is an approach that allows manipulation of the lipid composition of specific domains and/or the protein composition, and the evaluation of the reciprocal effects. Since the middle of the 80's, lipid bilayer membranes have been constantly developed as models of biological membranes with the ultimate goal to reincorporate membrane proteins for their functional investigation. In this review, after a brief description of the planar lipid bilayers as biomimetic membrane models, we will focus on the construction of the tethered Bilayer Lipid Membranes, the most promising model for efficient membrane protein reconstitution and investigation of molecular processes occurring in cell membranes.
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23
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Neubacher H, Mey I, Carnarius C, Lazzara TD, Steinem C. Permeabilization assay for antimicrobial peptides based on pore-spanning lipid membranes on nanoporous alumina. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4767-4774. [PMID: 24707859 DOI: 10.1021/la500358h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Screening tools to study antimicrobial peptides (AMPs) with the aim to optimize therapeutic delivery vectors require automated and parallelized sampling based on chip technology. Here, we present the development of a chip-based assay that allows for the investigation of the action of AMPs on planar lipid membranes in a time-resolved manner by fluorescence readout. Anodic aluminum oxide (AAO) composed of cylindrical pores with a diameter of 70 nm and a thickness of up to 10 μm was used as a support to generate pore-spanning lipid bilayers from giant unilamellar vesicle spreading, which resulted in large continuous membrane patches sealing the pores. Because AAO is optically transparent, fluid single lipid bilayers and the underlying pore cavities can be readily observed by three-dimensional confocal laser scanning microscopy (CLSM). To assay the membrane permeabilizing activity of the AMPs, the translocation of the water-soluble dyes into the AAO cavities and the fluorescence of the sulforhodamine 101 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanol-l-amine triethylammonium salt (Texas Red DHPE)-labeled lipid membrane were observed by CLSM in a time-resolved manner as a function of the AMP concentration. The effect of two different AMPs, magainin-2 and melittin, was investigated, showing that the concentrations required for membrane permeabilization and the kinetics of the dye entrance differ significantly. Our results are discussed in light of the proposed permeabilization models of the two AMPs. The presented data demonstrate the potential of this setup for the development of an on-chip screening platform for AMPs.
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Affiliation(s)
- Henrik Neubacher
- Institute of Organic and Biomolecular Chemistry , University of Göfttingen, Tammannstraße 2, 37077 Göttingen, Germany
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24
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OuYang B, Chou JJ. The minimalist architectures of viroporins and their therapeutic implications. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1838:1058-67. [PMID: 24055819 PMCID: PMC3943691 DOI: 10.1016/j.bbamem.2013.09.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 09/03/2013] [Accepted: 09/08/2013] [Indexed: 11/23/2022]
Abstract
Many viral genomes encode small, integral membrane proteins that form homo-oligomeric channels in membrane, and they transport protons, cations, and other molecules across the membrane barrier to aid various steps of viral entry and maturation. These viral proteins, collectively named viroporins, are crucial for viral pathogenicity. In the past five years, structures obtained by nuclear magnetic resonance (NMR), X-ray crystallography, and electron microscopy (EM) showed that viroporins often adopt minimalist architectures to achieve their functions. A number of small molecules have been identified to interfere with their channel activities and thereby inhibit viral infection, making viroporins potential drug targets for therapeutic intervention. The known architectures and inhibition mechanisms of viroporins differ significantly from each other, but some common principles are shared between them. This review article summarizes the recent developments in the structural investigation of viroporins and their inhibition by antiviral compounds. This article is part of a Special Issue entitled: Viral Membrane Proteins-Channels for Cellular Networking.
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Affiliation(s)
- Bo OuYang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China; National Center for Protein Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China
| | - James J Chou
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China; National Center for Protein Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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25
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Ramachandran S, Arce FT, Patel NR, Quist AP, Cohen DA, Lal R. Structure and permeability of ion-channels by integrated AFM and waveguide TIRF microscopy. Sci Rep 2014; 4:4424. [PMID: 24651823 PMCID: PMC3961736 DOI: 10.1038/srep04424] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 03/03/2014] [Indexed: 11/09/2022] Open
Abstract
Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal reflection fluorescence microscopy (TIRFM) for high resolution imaging and molecular transport measurement. Significantly, membranes over the nanopore were stable for repeated AFM imaging. We studied structure-activity relationship of gap junction hemichannels reconstituted in lipid bilayers. Individual hemichannels in the membrane overlying the nanopore were resolved and transport of hemichannel-permeant LY dye was visualized when the hemichannel was opened by lowering calcium in the medium. This integrated technique will allow direct structure-permeability relationship of many ion channels and receptors.
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Affiliation(s)
- Srinivasan Ramachandran
- 1] Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093 [2]
| | - Fernando Teran Arce
- 1] Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093 [2]
| | - Nirav R Patel
- Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
| | - Arjan P Quist
- RC Nano Corporation, 2210 Midwest Road, Oak Brook, IL 60523, USA. Current Address: Innovation and New Ventures Office, Northwestern University, 1800 Sherman Ave., Evanston IL 60201
| | - Daniel A Cohen
- Department of Materials, University of California Santa Barbara, CA 93106
| | - Ratnesh Lal
- Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
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26
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Prudovsky I, Kumar TKS, Sterling S, Neivandt D. Protein-phospholipid interactions in nonclassical protein secretion: problem and methods of study. Int J Mol Sci 2013; 14:3734-72. [PMID: 23396106 PMCID: PMC3588068 DOI: 10.3390/ijms14023734] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 12/30/2022] Open
Abstract
Extracellular proteins devoid of signal peptides use nonclassical secretion mechanisms for their export. These mechanisms are independent of the endoplasmic reticulum and Golgi. Some nonclassically released proteins, particularly fibroblast growth factors (FGF) 1 and 2, are exported as a result of their direct translocation through the cell membrane. This process requires specific interactions of released proteins with membrane phospholipids. In this review written by a cell biologist, a structural biologist and two membrane engineers, we discuss the following subjects: (i) Phenomenon of nonclassical protein release and its biological significance; (ii) Composition of the FGF1 multiprotein release complex (MRC); (iii) The relationship between FGF1 export and acidic phospholipid externalization; (iv) Interactions of FGF1 MRC components with acidic phospholipids; (v) Methods to study the transmembrane translocation of proteins; (vi) Membrane models to study nonclassical protein release.
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Affiliation(s)
- Igor Prudovsky
- Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME 04074, USA
| | | | - Sarah Sterling
- Department of Chemical and Biological Engineering, University of Maine, Orono, ME 04469, USA; E-Mails: (S.S.); (D.N.)
| | - David Neivandt
- Department of Chemical and Biological Engineering, University of Maine, Orono, ME 04469, USA; E-Mails: (S.S.); (D.N.)
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27
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Frese D, Steltenkamp S, Schmitz S, Steinem C. In situ generation of electrochemical gradients across pore-spanning membranes. RSC Adv 2013. [DOI: 10.1039/c3ra42723d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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28
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Lee YK, Nam JM. Electrofluidic lipid membrane biosensor. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:832-837. [PMID: 22271621 DOI: 10.1002/smll.201102093] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Young Kwang Lee
- Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-747, South Korea
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29
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Zagnoni M. Miniaturised technologies for the development of artificial lipid bilayer systems. LAB ON A CHIP 2012; 12:1026-1039. [PMID: 22301684 DOI: 10.1039/c2lc20991h] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Artificially reproducing cellular environments is a key aim of synthetic biology, which has the potential to greatly enhance our understanding of cellular mechanisms. Microfluidic and lab-on-a-chip (LOC) techniques, which enable the controlled handling of sub-microlitre volumes of fluids in an automated and high-throughput manner, can play a major role in achieving this by offering alternative and powerful methodologies in an on-chip format. Such techniques have been successfully employed over the last twenty years to provide innovative solutions for chemical analysis and cell-, molecular- and synthetic- biology. In the context of the latter, the formation of artificial cell membranes (or artificial lipid bilayers) that incorporate membrane proteins within miniaturised LOC architectures offers huge potential for the development of highly sensitive molecular sensors and drug screening applications. The aim of this review is to give a comprehensive and critical overview of the field of microsystems for creating and exploiting artificial lipid bilayers. Advantages and limitations of three of the most popular approaches, namely suspended, supported and droplet-based lipid bilayers, are discussed. Examples are reported that show how artificial cell membrane microsystems, by combining together biological procedures and engineering techniques, can provide novel methodologies for basic biological and biophysical research and for the development of biotechnology tools.
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Affiliation(s)
- Michele Zagnoni
- Centre for Microsystems and Photonics, University of Strathclyde, Glasgow, UK.
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30
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Lipid Bilayer Membrane Arrays: Fabrication and Applications. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2012; 131:121-52. [DOI: 10.1007/10_2012_135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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31
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Fischer WB, Wang YT, Schindler C, Chen CP. Mechanism of function of viral channel proteins and implications for drug development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:259-321. [PMID: 22364876 PMCID: PMC7149447 DOI: 10.1016/b978-0-12-394305-7.00006-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Viral channel-forming proteins comprise a class of viral proteins which, similar to their host companions, are made to alter electrochemical or substrate gradients across lipid membranes. These proteins are active during all stages of the cellular life cycle of viruses. An increasing number of proteins are identified as channel proteins, but the precise role in the viral life cycle is yet unknown for the majority of them. This review presents an overview about these proteins with an emphasis on those with available structural information. A concept is introduced which aligns the transmembrane domains of viral channel proteins with those of host channels and toxins to give insights into the mechanism of function of the viral proteins from potential sequence identities. A summary of to date investigations on drugs targeting these proteins is given and discussed in respect of their mode of action in vivo.
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Affiliation(s)
- Wolfgang B. Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Yi-Ting Wang
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Christina Schindler
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Chin-Pei Chen
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
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32
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Sumitomo K, McAllister A, Tamba Y, Kashimura Y, Tanaka A, Shinozaki Y, Torimitsu K. Ca2+ ion transport through channels formed by α-hemolysin analyzed using a microwell array on a Si substrate. Biosens Bioelectron 2011; 31:445-50. [PMID: 22152991 DOI: 10.1016/j.bios.2011.11.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 11/06/2011] [Indexed: 10/15/2022]
Abstract
For the functional analysis of ion channel activity, an artificial lipid bilayer suspended over microwells was formed that ruptured giant unilamellar vesicles on a Si substrate. Ca(2+) ion indicators (fluo-4) were confined in the microwells by sealing the microwells with a lipid bilayer. An overhang formed at the microwells prevented the lipid membrane from falling into them and allowed the stable confinement of the fluorescent probes. The transport of Ca(2+) ions through the channels formed by α-hemolysin inserted in a lipid membrane was analyzed by employing the fluorescence intensity change of fluo-4 in the microwells. The microwell volume was very small (1-100 fl), so a highly sensitive monitor could be realized. The detection limit is several tens of ions/s/μm(2), and this is much smaller than the ion current in a standard electrophysiological measurement. Smaller microwells will make it possible to mimic a local ion concentration change in the cells, although the signal to noise ratio must be further improved for the functional analysis of a single channel. We demonstrated that a microwell array with confined fluorescent probes sealed by a lipid bilayer could constitute a basic component of a highly sensitive biosensor array that works with functional membrane proteins. This array will allow us to realize high throughput and parallel testing devices.
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Affiliation(s)
- Koji Sumitomo
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
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Lundgren A, Hedlund J, Andersson O, Brändén M, Kunze A, Elwing H, Höök F. Resonance-Mode Electrochemical Impedance Measurements of Silicon Dioxide Supported Lipid Bilayer Formation and Ion Channel Mediated Charge Transport. Anal Chem 2011; 83:7800-6. [DOI: 10.1021/ac201273t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Anders Lundgren
- Department of Cell and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Julia Hedlund
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
| | - Olof Andersson
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
| | - Magnus Brändén
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Angelika Kunze
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Hans Elwing
- Department of Cell and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Fredrik Höök
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
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Kocun M, Lazzara TD, Steinem C, Janshoff A. Preparation of solvent-free, pore-spanning lipid bilayers: modeling the low tension of plasma membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7672-7680. [PMID: 21619014 DOI: 10.1021/la2003172] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Plasma membrane tension, produced by the underlying cytoskeleton, governs many dynamic processes such as fusion, blebbing, exo- and endocytosis, cell migration, and adhesion. Here, a new protocol is introduced to model this intricate and often overlooked aspect of the plasma membrane. Lipid bilayers spanning pores of 600 nm radius were prepared by adsorption and spreading of giant unilamellar vesicles (GUVs) on moderately hydrophilic porous substrates prepared by gold-coating and subsequent self-assembly of a mercaptoethanol monolayer. Rupture of GUVs formed tens of micrometer sized pore-spanning membrane patches displaying low tension of σ ≤ 3.5 mN m(-1) and lateral diffusion constants of about 8 μm(2) s(-1). Site-specific force indentation experiments were performed to determine membrane tension as a function of lipid composition: for pure DOPC bilayers, a tension of 1.018 ± 0.014 mN m(-1) was measured, which was increased by the addition of cholesterol to 3.50 ± 0.15 mN m(-1). Compared to DOPC, POPC bilayers displayed a larger tension of 2.00 ± 0.09 mN m(-1). Addition and subsequent partitioning of 2-propanol was shown to significantly reduce the membrane tension as a function of its concentration.
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Affiliation(s)
- Marta Kocun
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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35
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Bhattacharya J, Kisner A, Offenhäusser A, Wolfrum B. Microfluidic anodization of aluminum films for the fabrication of nanoporous lipid bilayer support structures. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2011; 2:104-109. [PMID: 21977420 PMCID: PMC3148057 DOI: 10.3762/bjnano.2.12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 02/04/2011] [Indexed: 05/31/2023]
Abstract
Solid state nanoporous membranes show great potential as support structures for biointerfaces. In this paper, we present a technique for fabricating nanoporous alumina membranes under constant-flow conditions in a microfluidic environment. This approach allows the direct integration of the fabrication process into a microfluidic setup for performing biological experiments without the need to transfer the brittle nanoporous material. We demonstrate this technique by using the same microfluidic system for membrane fabrication and subsequent liposome fusion onto the nanoporous support structure. The resulting bilayer formation is monitored by impedance spectroscopy across the nanoporous alumina membrane in real-time. Our approach offers a simple and efficient methodology to investigate the activity of transmembrane proteins or ion diffusion across membrane bilayers.
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Affiliation(s)
- Jaydeep Bhattacharya
- Peter Grünberg Institute, PGI-8/ICS-8, Forschungszentrum Jülich GmbH, Leo-Brandt-Str., 52425 Jülich, Germany and Jülich - Aachen Research Alliance (JARA - FIT), Germany
| | - Alexandre Kisner
- Peter Grünberg Institute, PGI-8/ICS-8, Forschungszentrum Jülich GmbH, Leo-Brandt-Str., 52425 Jülich, Germany and Jülich - Aachen Research Alliance (JARA - FIT), Germany
| | - Andreas Offenhäusser
- Peter Grünberg Institute, PGI-8/ICS-8, Forschungszentrum Jülich GmbH, Leo-Brandt-Str., 52425 Jülich, Germany and Jülich - Aachen Research Alliance (JARA - FIT), Germany
| | - Bernhard Wolfrum
- Peter Grünberg Institute, PGI-8/ICS-8, Forschungszentrum Jülich GmbH, Leo-Brandt-Str., 52425 Jülich, Germany and Jülich - Aachen Research Alliance (JARA - FIT), Germany
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36
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Fischer WB, Hsu HJ. Viral channel forming proteins - modeling the target. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1808:561-71. [PMID: 20546700 PMCID: PMC7094444 DOI: 10.1016/j.bbamem.2010.05.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 05/11/2010] [Accepted: 05/14/2010] [Indexed: 01/02/2023]
Abstract
The cellular and subcellular membranes encounter an important playground for the activity of membrane proteins encoded by viruses. Viral membrane proteins, similar to their host companions, can be integral or attached to the membrane. They are involved in directing the cellular and viral reproduction, the fusion and budding processes. This review focuses especially on those integral viral membrane proteins which form channels or pores, the classification to be so, modeling by in silico methods and potential drug candidates. The sequence of an isolate of Vpu from HIV-1 is aligned with host ion channels and a toxin. The focus is on the alignment of the transmembrane domains. The results of the alignment are mapped onto the 3D structures of the respective channels and toxin. The results of the mapping support the idea of a 'channel-pore dualism' for Vpu.
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Affiliation(s)
- Wolfgang B Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan.
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37
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Phung T, Zhang Y, Dunlop J, Dalziel JE. Porous Materials to Support Bilayer Lipid Membranes for Ion Channel Biosensors. INTERNATIONAL JOURNAL OF ELECTROCHEMISTRY 2011. [DOI: 10.4061/2011/213107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To identify materials suitable as membrane supports for ion channel biosensors, six filter materials of varying hydrophobicity, tortuosity, and thickness were examined for their ability to support bilayer lipid membranes as determined by electrical impedance spectroscopy. Bilayers supported by hydrophobic materials (PTFE, polycarbonate, nylon, and silanised silver) had optimal resistance (14–19 GΩ) and capacitance (0.8–1.6 μF) values whereas those with low hydrophobicity did not form BLMs (PVDF) or were short-lived (unsilanised silver). The ability of ion channels to function in BLMs was assessed using a method recently reported to improve the efficiency of proteoliposome incorporation into PTFE-supported bilayers. Voltage-gated sodium channel activation by veratridine and inhibition by saxitoxin showed activity for PTFE, nylon, and silanised silver, but not polycarbonate. Bilayers on thicker, more tortuous, and hydrophobic materials produced higher current levels. Bilayers that self-assembled on PTFE filters were the longest lived and produced the most channel activity using this method.
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Affiliation(s)
- Thai Phung
- AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
| | - Yanli Zhang
- AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
| | - James Dunlop
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand
| | - Julie E. Dalziel
- AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
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38
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Bally M, Bailey K, Sugihara K, Grieshaber D, Vörös J, Städler B. Liposome and lipid bilayer arrays towards biosensing applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:2481-97. [PMID: 20925039 DOI: 10.1002/smll.201000644] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Sensitive and selective biosensors for high-throughput screening are having an increasing impact in modern medical care. The establishment of robust protein biosensing platforms however remains challenging, especially when membrane proteins are involved. Although this type of proteins is of enormous relevance since they are considered in >60% of the pharmaceutical drug targets, their fragile nature (i.e., the requirement to preserve their natural lipid environment to avoid denaturation and loss of function) puts strong additional prerequisites onto a successful biochip. In this review, the leading approaches to create lipid membrane-based arrays towards the creation of membrane protein biosensing platforms are described. Liposomes assembled in micro- and nanoarrays and the successful set-ups containing functional membrane proteins, as well as the use of liposomes in networks, are discussed in the first part. Then, the complementary approaches to create cell-mimicking supported membrane patches on a substrate in an array format will be addressed. Finally, the progress in assembling free-standing (functional) lipid bilayers over nanopore arrays for ion channel sensing will be reported. This review illustrates the rapid pace by which advances are being made towards the creation of a heterogeneous biochip for the high-throughput screening of membrane proteins for diagnostics, drug screening, or drug discovery purposes.
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Affiliation(s)
- Marta Bally
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Zurich, 8092, Switzerland
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39
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Cook GA, Zhang H, Park SH, Wang Y, Opella SJ. Comparative NMR studies demonstrate profound differences between two viroporins: p7 of HCV and Vpu of HIV-1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:554-60. [PMID: 20727848 DOI: 10.1016/j.bbamem.2010.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 08/03/2010] [Accepted: 08/05/2010] [Indexed: 10/19/2022]
Abstract
The p7 protein from hepatitis C virus and the Vpu protein from HIV-1 are members of the viroporin family of small viral membrane proteins. It is essential to determine their structures in order to obtain an understanding of their molecular mechanisms and to develop new classes of anti-viral drugs. Because they are membrane proteins, it is challenging to study them in their native phospholipid bilayer environments by most experimental methods. Here we describe applications of NMR spectroscopy to both p7 and Vpu. Isotopically labeled p7 and Vpu samples were prepared by heterologous expression in bacteria, initial isolation as fusion proteins, and final purification by chromatography. The purified proteins were studied in the model membrane environments of micelles by solution NMR spectroscopy and in aligned phospholipid bilayers by solid-state NMR spectroscopy. The resulting structural findings enable comparisons to be made between the two proteins, demonstrating that they have quite different architectures. Most notably, Vpu has one trans-membrane helix and p7 has two trans-membrane helices; in addition, there are significant differences in the structures and dynamics of their internal loop and terminal regions.
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Affiliation(s)
- Gabriel A Cook
- Department of Chemistry and Biochemistry, University of California, San Diego, Lajolla, CA 92093, USA
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40
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Patargias G, Ewart G, Luscombe C, Fischer WB. Ligand-protein docking studies of potential HIV-1 drug compounds using the algorithm FlexX. Anal Bioanal Chem 2010; 396:2559-63. [PMID: 20165836 DOI: 10.1007/s00216-010-3498-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Revised: 01/19/2010] [Accepted: 01/20/2010] [Indexed: 10/19/2022]
Abstract
Four compounds are docked to a pentameric bundle representing the transmembrane part of the Vpu protein from HIV-1. Employing the docking algorithm FlexX, their free energy of binding is estimated leading to the conclusion that potential drug candidates need to form H-bonds either with neighbouring or with n + 2 helices at the site of the serines within the bundle.
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Affiliation(s)
- George Patargias
- Biomembrane Structure Unit, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, UK
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41
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Zhang X, Zhu Z, Sun C, Zhu F, Luo Z, Yan J, Mao B. Colloidal lithography-based fabrication of suspended nanoporous silicon nitride membranes. Mikrochim Acta 2009. [DOI: 10.1007/s00604-009-0216-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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42
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Gassmann O, Kreir M, Ambrosi C, Pranskevich J, Oshima A, Röling C, Sosinsky G, Fertig N, Steinem C. The M34A mutant of Connexin26 reveals active conductance states in pore-suspending membranes. J Struct Biol 2009; 168:168-76. [PMID: 19236918 PMCID: PMC2785080 DOI: 10.1016/j.jsb.2009.02.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 02/09/2009] [Accepted: 02/11/2009] [Indexed: 11/20/2022]
Abstract
Connexin26 (Cx26) is a member of the connexin family, the building blocks for gap junction intercellular channels. These dodecameric assemblies are involved in gap junction-mediated cell-cell communication allowing the passage of ions and small molecules between two neighboring cells. Mutations in Cx26 lead to the disruption of gap junction-mediated intercellular communication with consequences such as hearing loss and skin disorders. We show here that a mutant of Cx26, M34A, forms an active hemichannel in lipid bilayer experiments. A comparison with the Cx26 wild-type is presented. Two different techniques using micro/nano-structured substrates for the formation of pore-suspending lipid membranes are used. We reconstituted the Cx26 wild-type and Cx26M34A into artificial lipid bilayers and observed single channel activity for each technique, with conductance levels of around 35, 70 and 165 pS for the wild-type. The conductance levels of Cx26M34A were found at around 45 and 70 pS.
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Affiliation(s)
- Oliver Gassmann
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Germany
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43
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Nussio MR, Oncins G, Ridelis I, Szili E, Shapter JG, Sanz F, Voelcker NH. Nanomechanical Characterization of Phospholipid Bilayer Islands on Flat and Porous Substrates: A Force Spectroscopy Study. J Phys Chem B 2009; 113:10339-47. [DOI: 10.1021/jp811035g] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthew R. Nussio
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Gerard Oncins
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Ingrid Ridelis
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Endre Szili
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Joseph G. Shapter
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Fausto Sanz
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
| | - Nicolas H. Voelcker
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia, Scientific-Technical Services, Nanometric Techniques Unit, University of Barcelona, Soler i Sabaris 1, 08028 Barcelona, Spain, Nanoprobes and Nanoswitches, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 13,08028 Barcelona, Spain, Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, and CIBER
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Mey I, Stephan M, Schmitt EK, Müller MM, Ben Amar M, Steinem C, Janshoff A. Local Membrane Mechanics of Pore-Spanning Bilayers. J Am Chem Soc 2009; 131:7031-9. [DOI: 10.1021/ja809165h] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ingo Mey
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Milena Stephan
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Eva K. Schmitt
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Martin Michael Müller
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Martine Ben Amar
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Claudia Steinem
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
| | - Andreas Janshoff
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany, Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany, and Laboratoire de Physique Statistique de l’Ecole Normale Supérieure (UMR 8550), associé aux Universités Paris 6 et Paris 7 et au CNRS; 24, rue Lhomond, 75005 Paris, France
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Böcker M, Muschter S, Schmitt EK, Steinem C, Schäffer TE. Imaging and patterning of pore-suspending membranes with scanning ion conductance microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:3022-3028. [PMID: 19437710 DOI: 10.1021/la8034227] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Nano-BLMs (black lipid membranes) suspending the pores of highly ordered porous silicon substrates have been proven useful for functional investigations of ion channel proteins by electrical readouts. With the aim to monitor the resistive behavior of nano-BLMs spatially resolved in a contact-free manner, we report here on the visualization of nano-BLMs by means of scanning ion conductance microscopy (SICM). Silicon surfaces with highly ordered pore arrays were coated with a gold layer and functionalized with octadecanethiol before a droplet of 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) (2% w/v) dissolved in n-decane was applied. The topography of DPhPC membranes suspending the pores was stably imaged for hours without mechanical contact using SICM. This suggests that SICM provides a significant advantage over atomic force microscopy, where mechanical interactions occur that easily damage the suspended membranes. Dynamic processes such as spreading and rupturing of membranes were spatially and temporally resolved. Furthermore, SICM was used to individually manipulate membranes suspending single pores, thereby writing lithographic patterns into the lipid. The process of local membrane manipulation was correlated to a characteristic signature in the simultaneously recorded ion current. The results show that SICM is well-suited both for contact-free imaging of soft suspended membranes and for local membrane manipulation.
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Affiliation(s)
- Matthias Böcker
- Institute of Applied Physics, University of Erlangen-Nuremberg, Staudtstr. 7, Bldg. A3, 91058 Erlangen, Germany
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46
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Nano for bio: Nanopore arrays for stable and functional lipid bilayer membranes (Mini Review). Biointerphases 2008; 3:FA74. [DOI: 10.1116/1.2912932] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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47
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Cubic phases in biosensing systems. Anal Bioanal Chem 2008; 391:1569-78. [DOI: 10.1007/s00216-008-2149-y] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 04/16/2008] [Accepted: 04/18/2008] [Indexed: 10/22/2022]
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48
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Pilz CS, Steinem C. Modulation of the conductance of a 2,2'-bipyridine-functionalized peptidic ion channel by Ni2+. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:1065-71. [PMID: 18347789 PMCID: PMC2480505 DOI: 10.1007/s00249-008-0298-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 02/22/2008] [Accepted: 02/26/2008] [Indexed: 12/01/2022]
Abstract
An α-helical amphipathic peptide with the sequence H2N-(LSSLLSL)3-CONH2 was obtained by solid phase synthesis and a 2,2′-bipyridine was coupled to its N-terminus, which allows complexation of Ni2+. Complexation of the 2,2′-bipyridine residues was proven by UV/Vis spectroscopy. The peptide helices were inserted into lipid bilayers (nano black lipid membranes, nano-BLMs) that suspend the pores of porous alumina substrates with a pore diameter of 60 nm by applying a potential difference. From single channel recordings, we were able to distinguish four distinct conductance states, which we attribute to an increasing number of peptide helices participating in the conducting helix bundle. Addition of Ni2+ in micromolar concentrations altered the conductance behaviour of the formed ion channels in nano-BLMs considerably. The first two conductance states appear much more prominent demonstrating that the complexation of bipyridine by Ni2+ results in a considerable confinement of the observed multiple conductance states. However, the conductance levels were independent of the presence of Ni2+. Moreover, from a detailed analysis of the open lifetimes of the channels, we conclude that the complexation of Ni2+ diminishes the frequency of channel events with larger open times.
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Affiliation(s)
- Claudia S Pilz
- Institut für Organische und Biomolekulare Chemie, Georg-August Universität, Tammannstr. 2, 37077, Göttingen, Germany
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Grieshaber D, MacKenzie R, Vörös J, Reimhult E. Electrochemical Biosensors - Sensor Principles and Architectures. SENSORS (BASEL, SWITZERLAND) 2008; 8:1400-1458. [PMID: 27879772 PMCID: PMC3663003 DOI: 10.3390/s80314000] [Citation(s) in RCA: 770] [Impact Index Per Article: 48.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 01/28/2008] [Indexed: 11/16/2022]
Abstract
Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response.
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Affiliation(s)
- Dorothee Grieshaber
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Robert MacKenzie
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Janos Vörös
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Erik Reimhult
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland.
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