1
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Sasidharan S, Knepper L, Ankrom E, Cucé G, Kong L, Ratajczak A, Im W, Thévenin D, Honerkamp-Smith A. Microfluidic measurement of the size and shape of lipid-anchored proteins. Biophys J 2024; 123:3478-3489. [PMID: 39228123 DOI: 10.1016/j.bpj.2024.08.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 08/06/2024] [Accepted: 08/29/2024] [Indexed: 09/05/2024] Open
Abstract
The surface of a cell is crowded with membrane proteins. The size, shape, density, and mobility of extracellular surface proteins mediate cell surface accessibility to external molecules, viral particles, and other cells. However, predicting these qualities is not always straightforward, even when protein structures are known. We previously developed an experimental method for measuring flow-driven lateral transport of neutravidin bound to biotinylated lipids in supported lipid bilayers. Here, we use this method to detect hydrodynamic force applied to a series of lipid-anchored proteins with increasing size. We find that the measured force reflects both protein size and shape, making it possible to distinguish these features of intact, folded proteins in their undisturbed orientation and proximity to the lipid membrane. In addition, our results demonstrate that individual proteins are transported large distances by flow forces on the order of femtoNewtons, similar in magnitude to the shear forces resulting from blood circulation or from the swimming motion of microorganisms. Similar protein transport across living cells by hydrodynamic force may contribute to biological flow sensing.
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Affiliation(s)
| | - Leah Knepper
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania
| | - Emily Ankrom
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania
| | - Gabriel Cucé
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
| | - Lingyang Kong
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania
| | - Amanda Ratajczak
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
| | - Wonpil Im
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania
| | - Damien Thévenin
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania
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2
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Miller EJ, Phan MD, Shah J, Honerkamp-Smith AR. Passive and reversible area regulation of supported lipid bilayers in response to fluid flow. Biophys J 2023; 122:2242-2255. [PMID: 36639867 PMCID: PMC10257118 DOI: 10.1016/j.bpj.2023.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/21/2022] [Accepted: 01/09/2023] [Indexed: 01/14/2023] Open
Abstract
Biological and model membranes are frequently subjected to fluid shear stress. However, membrane mechanical responses to flow remain incompletely described. This is particularly true of membranes supported on a solid substrate, and the influences of membrane composition and substrate roughness on membrane flow responses remain poorly understood. Here, we combine microfluidics, fluorescence microscopy, and neutron reflectivity to explore how supported lipid bilayer patches respond to controlled shear stress. We demonstrate that lipid membranes undergo a significant, passive, and partially reversible increase in membrane area due to flow. We show that these fluctuations in membrane area can be constrained, but not prevented, by increasing substrate roughness. Similar flow-induced changes to membrane structure may contribute to the ability of living cells to sense and respond to flow.
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Affiliation(s)
| | - Minh D Phan
- Large-Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Center for Neutron Science, Department of Chemical & Biomolecular Engineering, University of Delaware, Newark, Delaware
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3
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Ratajczak AM, Sasidharan S, Rivera Gonzalez XI, Miller EJ, Socrier L, Anthony AA, Honerkamp-Smith AR. Measuring flow-mediated protein drift across stationary supported lipid bilayers. Biophys J 2023; 122:1720-1731. [PMID: 37020419 PMCID: PMC10183372 DOI: 10.1016/j.bpj.2023.03.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 03/13/2023] [Accepted: 03/29/2023] [Indexed: 04/07/2023] Open
Abstract
Fluid flow near biological membranes influences cell functions such as development, motility, and environmental sensing. Flow can laterally transport extracellular membrane proteins located at the cell-fluid interface. To determine whether this transport contributes to flow signaling in cells, quantitative knowledge of the forces acting on membrane proteins is required. Here, we demonstrate a method for measuring flow-mediated lateral transport of lipid-anchored proteins. We rupture giant unilamellar vesicles to form discrete patches of supported membrane inside rectangular microchannels and then allow proteins to bind to the upper surface of the membrane. While applying flow, we observe the formation of protein concentration gradients that span the membrane patch. By observing how these gradients dynamically respond to changes in applied shear stress, we determine the flow mobility of the lipid-anchored protein. We use simplified model membranes and proteins to demonstrate our method's sensitivity and reproducibility. Our intention was to design a quantitative, reliable method and analysis for protein mobility that we will use to compare flow transport for a variety of proteins, lipid anchors, and membranes in model systems and on living cells.
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Affiliation(s)
| | | | | | - Ethan J Miller
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
| | - Larissa Socrier
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
| | - Autumn A Anthony
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
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4
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Wang Y, Gao Y, Song Y. Microfluidics-Based Urine Biopsy for Cancer Diagnosis: Recent Advances and Future Trends. ChemMedChem 2022; 17:e202200422. [PMID: 36040297 DOI: 10.1002/cmdc.202200422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 08/23/2022] [Indexed: 11/08/2022]
Abstract
Urine biopsy, allowing for the detection, analysis and monitoring of numerous cancer-associated urinary biomarkers to provide insights into cancer occurrence, progression and metastasis, has emerged as an attractive liquid biopsy strategy with enormous advantages over traditional tissue biopsy, such as noninvasiveness, large sample volume, and simple sampling operation. Microfluidics enables precise manipulation of fluids in a tiny chip and exhibits outstanding performance in urine biopsy owing to its minimization, low cost, high integration, high throughput and low sample consumption. Herein, we review recent advances in microfluidic techniques employed in urine biopsy for cancer detection. After briefly summarizing the major urinary biomarkers used for cancer diagnosis, we provide an overview of the typical microfluidic techniques utilized to develop urine biopsy devices. Some prospects along with the major challenges to be addressed for the future of microfluidic-based urine biopsy are also discussed.
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Affiliation(s)
- Yanping Wang
- Nanjing University of Science and Technology, Sino-French Engineer School, CHINA
| | - Yanfeng Gao
- Nanjing University, College of Engineering and Applied Sciences, CHINA
| | - Yujun Song
- Nanjing University, Biomedical Engineering, 22 Hankou Road, 210093, Nanjing, CHINA
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5
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Carlson CA, Udad XS, Owen Q, Amin-Patel AP, Chang WJ, Woehl JC. DC corral trapping of single nanoparticles and macromolecules in solution. J Chem Phys 2022; 156:164201. [PMID: 35489994 DOI: 10.1063/5.0087039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Progress in sorting, separating, and characterizing ever smaller amounts of chemical and biological material depends on the availability of methods for the controlled interaction with nanoscale and molecular-size objects. Here, we report on the reversible, tunable trapping of single DNA molecules and other charged micro- and nanoparticles in aqueous solution using a direct-current (DC) corral trap setup. The trap consists of a circular, non-conductive void in a metal-coated surface that, when charged, generates an electrostatic potential well in the proximate solution. Our results demonstrate that stable, nanoscale confinement of charged objects is achievable over extended periods of time, that trap stiffness is controlled by the applied voltage, and that simultaneous trapping of multiple objects is feasible. The approach shows great promise for lab-on-a-chip systems and biomedical applications due to its simplicity, scalability, selectivity, and the capability to manipulate single DNA molecules in standard buffer solutions.
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Affiliation(s)
- Christine A Carlson
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
| | - Xavier S Udad
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
| | - Quintus Owen
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
| | - Alaknanda P Amin-Patel
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
| | - Woo-Jin Chang
- Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
| | - Jörg C Woehl
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA
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6
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Taylor DP, Mathur P, Renaud P, Kaigala GV. Microscale hydrodynamic confinements: shaping liquids across length scales as a toolbox in life sciences. LAB ON A CHIP 2022; 22:1415-1437. [PMID: 35348555 DOI: 10.1039/d1lc01101d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Hydrodynamic phenomena can be leveraged to confine a range of biological and chemical species without needing physical walls. In this review, we list methods for the generation and manipulation of microfluidic hydrodynamic confinements in free-flowing liquids and near surfaces, and elucidate the associated underlying theory and discuss their utility in the emerging area of open space microfluidics applied to life-sciences. Microscale hydrodynamic confinements are already starting to transform approaches in fundamental and applied life-sciences research from precise separation and sorting of individual cells, allowing localized bio-printing to multiplexing for clinical diagnosis. Through the choice of specific flow regimes and geometrical boundary conditions, hydrodynamic confinements can confine species across different length scales from small molecules to large cells, and thus be applied to a wide range of functionalities. We here provide practical examples and implementations for the formation of these confinements in different boundary conditions - within closed channels, in between parallel plates and in an open liquid volume. Further, to enable non-microfluidics researchers to apply hydrodynamic flow confinements in their work, we provide simplified instructions pertaining to their design and modelling, as well as to the formation of hydrodynamic flow confinements in the form of step-by-step tutorials and analytical toolbox software. This review is written with the idea to lower the barrier towards the use of hydrodynamic flow confinements in life sciences research.
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Affiliation(s)
- David P Taylor
- IBM Research - Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
- Microsystems Laboratory 4, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Prerit Mathur
- IBM Research - Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
- Dept. of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule (ETH), Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
| | - Philippe Renaud
- Microsystems Laboratory 4, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Govind V Kaigala
- IBM Research - Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
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7
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Ma VPY, Hu Y, Kellner AV, Brockman JM, Velusamy A, Blanchard AT, Evavold BD, Alon R, Salaita K. The magnitude of LFA-1/ICAM-1 forces fine-tune TCR-triggered T cell activation. SCIENCE ADVANCES 2022; 8:eabg4485. [PMID: 35213231 PMCID: PMC8880789 DOI: 10.1126/sciadv.abg4485] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 12/15/2021] [Indexed: 05/15/2023]
Abstract
T cells defend against cancer and viral infections by rapidly scanning the surface of target cells seeking specific peptide antigens. This key process in adaptive immunity is sparked upon T cell receptor (TCR) binding of antigens within cell-cell junctions stabilized by integrin (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) complexes. A long-standing question in this area is whether the forces transmitted through the LFA-1/ICAM-1 complex tune T cell signaling. Here, we use spectrally encoded DNA tension probes to reveal the first maps of LFA-1 and TCR forces generated by the T cell cytoskeleton upon antigen recognition. DNA probes that control the magnitude of LFA-1 force show that F>12 pN potentiates antigen-dependent T cell activation by enhancing T cell-substrate engagement. LFA-1/ICAM-1 mechanical events with F>12 pN also enhance the discriminatory power of the TCR when presented with near cognate antigens. Overall, our results show that T cells integrate multiple channels of mechanical information through different ligand-receptor pairs to tune function.
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Affiliation(s)
| | - Yuesong Hu
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Anna V. Kellner
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332, USA
| | - Joshua M. Brockman
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332, USA
| | - Arventh Velusamy
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Aaron T. Blanchard
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332, USA
| | - Brian D. Evavold
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Ronen Alon
- Department of Immunology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Khalid Salaita
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332, USA
- Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA
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8
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Abstract
Scanning ion conductance microscopy (SICM) has emerged as a versatile tool for studies of interfaces in biology and materials science with notable utility in biophysical and electrochemical measurements. The heart of the SICM is a nanometer-scale electrolyte filled glass pipette that serves as a scanning probe. In the initial conception, manipulations of ion currents through the tip of the pipette and appropriate positioning hardware provided a route to recording micro- and nanoscopic mapping of the topography of surfaces. Subsequent advances in instrumentation, probe design, and methods significantly increased opportunities for SICM beyond recording topography. Hybridization of SICM with coincident characterization techniques such as optical microscopy and faradaic electrodes have brought SICM to the forefront as a tool for nanoscale chemical measurement for a wide range of applications. Modern approaches to SICM realize an important tool in analytical, bioanalytical, biophysical, and materials measurements, where significant opportunities remain for further exploration. In this review, we chronicle the development of SICM from the perspective of both the development of instrumentation and methods and the breadth of measurements performed.
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Affiliation(s)
- Cheng Zhu
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Kaixiang Huang
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Natasha P Siepser
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Lane A Baker
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, United States
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9
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Clarke RW. Theory of cell membrane interaction with glass. Phys Rev E 2021; 103:032401. [PMID: 33862714 DOI: 10.1103/physreve.103.032401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 01/19/2021] [Indexed: 11/07/2022]
Abstract
There are three regimes of cell membrane interaction with glass: Tight and loose adhesion, separated by repulsion. Explicitly including hydration, this paper evaluates the pressure between the surfaces as functions of distance for ion correlation and ion-screened electrostatics and electromagnetic fluctuations. The results agree with data for tight adhesion energy (0.5-3 vs 0.4-4 mJ/m^{2}), detachment pressure (7.9 vs. 9 MPa), and peak repulsion (3.4-7.5 vs. 5-10 kPa), also matching the repulsion's distance dependence on renormalization by steric pressure mainly from undulations.
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Affiliation(s)
- Richard W Clarke
- National Physical Laboratory, Teddington, TW11 0LW, United Kingdom
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10
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Junghans V, Santos AM, Lui Y, Davis SJ, Jönsson P. Dimensions and Interactions of Large T-Cell Surface Proteins. Front Immunol 2018; 9:2215. [PMID: 30319654 PMCID: PMC6170634 DOI: 10.3389/fimmu.2018.02215] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/06/2018] [Indexed: 11/23/2022] Open
Abstract
The first step of the adaptive immune response involves the interaction of T cells that express T-cell receptors (TCRs) with peptide-loaded major histocompatibility complexes expressed by antigen-presenting cells (APCs). Exactly how this leads to activation of the TCR and to downstream signaling is uncertain, however. Recent findings suggest that one of the key events is the exclusion of the large receptor-type tyrosine phosphatase CD45, from close contacts formed at sites of T-cell/APC interaction. If this is true, a full understanding of how close contact formation leads to signaling would require insights into the structures of, and interactions between, large membrane proteins like CD45 and other proteins forming the glycocalyx, such as CD43. Structural insights into the overall dimensions of these proteins using crystallographic methods are hard to obtain, and their conformations on the cell surface are also unknown. Several imaging-based optical microscopy techniques have however been developed for analyzing protein dimensions and orientation on model cell surfaces with nanometer precision. Here we review some of these methods with a focus on the use of hydrodynamic trapping, which relies on liquid flow from a micropipette to move and trap membrane-associated fluorescently labeled molecules. Important insights that have been obtained include (i) how protein flexibility and coverage might affect the effective heights of these molecules, (ii) the height of proteins on the membrane as a key parameter determining how they will distribute in cell-cell contacts, and (iii) how repulsive interactions between the extracellular parts of the proteins influences protein aggregation and distribution.
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Affiliation(s)
| | - Ana Mafalda Santos
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Yuan Lui
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Simon J. Davis
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Peter Jönsson
- Department of Chemistry, Lund University, Lund, Sweden
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11
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Junghans V, Hladilkova J, Santos AM, Lund M, Davis SJ, Jönsson P. Hydrodynamic trapping measures the interaction between membrane-associated molecules. Sci Rep 2018; 8:12479. [PMID: 30127338 PMCID: PMC6102267 DOI: 10.1038/s41598-018-30285-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 07/27/2018] [Indexed: 11/27/2022] Open
Abstract
How membrane proteins distribute and behave on the surface of cells depends on the molecules' chemical potential. However, measuring this potential, and how it varies with protein-to-protein distance, has been challenging. Here, we present a method we call hydrodynamic trapping that can achieve this. Our method uses the focused liquid flow from a micropipette to locally accumulate molecules protruding above a lipid membrane. The chemical potential, as well as information about the dimensions of the studied molecule, are obtained by relating the degree of accumulation to the strength of the trap. We have used this method to study four representative proteins, with different height-to-width ratios and molecular properties; from globular streptavidin, to the rod-like immune cell proteins CD2, CD4 and CD45. The data we obtain illustrates how protein shape, glycosylation and flexibility influence the behaviour of membrane proteins, as well as underlining the general applicability of the method.
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Affiliation(s)
| | - Jana Hladilkova
- Department of Chemistry, Lund University, SE-22100, Lund, Sweden
| | - Ana Mafalda Santos
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Mikael Lund
- Department of Chemistry, Lund University, SE-22100, Lund, Sweden
| | - Simon J Davis
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Peter Jönsson
- Department of Chemistry, Lund University, SE-22100, Lund, Sweden.
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12
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Abstract
Exploiting a femtoliter liquid meniscus formed on a nanopipet is a powerful approach to spatially control mass transfer or chemical reaction at the nanoscale. However, the insufficient reliability of techniques for the meniscus formation still restricts its practical use. We report on a noncontact, programmable method to produce a femtoliter liquid meniscus that is utilized for parallel three-dimensional (3D) nanoprinting. The method based on electrohydrodynamic dispensing enables one to create an ink meniscus at a pipet-substrate gap without physical contact and positional feedback. By guiding the meniscus under rapid evaporation of solvent in air, we successfully fabricate freestanding polymer 3D nanostructures. After a quantitative characterization of the experimental conditions, we show that we can use a multibarrel pipet to achieve parallel fabrication process of clustered nanowires with precise placement. We expect this technique to advance productivity in nanoscale 3D printing.
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Affiliation(s)
- Mojun Chen
- Department of Mechanical Engineering , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - Zhaoyi Xu
- Department of Mechanical Engineering , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - Jung Hyun Kim
- Nano Hybrid Technology Research Center , Korea Electrotechnology Research Institute (KERI) , Changwon-si , Gyeongsangnam-do 51543 , Republic of Korea
- Electrical Functional Material Engineering , Korea University of Science and Technology (UST) , Changwon-si , Gyeongsangnam-do 51543 , Republic of Korea
| | - Seung Kwon Seol
- Nano Hybrid Technology Research Center , Korea Electrotechnology Research Institute (KERI) , Changwon-si , Gyeongsangnam-do 51543 , Republic of Korea
- Electrical Functional Material Engineering , Korea University of Science and Technology (UST) , Changwon-si , Gyeongsangnam-do 51543 , Republic of Korea
| | - Ji Tae Kim
- Department of Mechanical Engineering , The University of Hong Kong , Pokfulam Road , Hong Kong , China
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13
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Bao P, Cartron ML, Sheikh KH, Johnson BRG, Hunter CN, Evans SD. Controlling transmembrane protein concentration and orientation in supported lipid bilayers. Chem Commun (Camb) 2018; 53:4250-4253. [PMID: 28361139 DOI: 10.1039/c7cc01023k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The trans-membrane protein - proteorhodopsin (pR) has been incorporated into supported lipid bilayers (SLB). In-plane electric fields have been used to manipulate the orientation and concentration of these proteins, within the SLB, through electrophoresis leading to a 25-fold increase concentration of pR.
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Affiliation(s)
- P Bao
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
| | - M L Cartron
- Department of Molecular Biology & Biotechnology, University of Sheffield, S10 2TH, UK
| | - K H Sheikh
- School of Biomedical Science, University of Leeds, LS2 9JT, UK
| | - B R G Johnson
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
| | - C N Hunter
- Department of Molecular Biology & Biotechnology, University of Sheffield, S10 2TH, UK
| | - S D Evans
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
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14
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Lundgren A, Fast BJ, Block S, Agnarsson B, Reimhult E, Gunnarsson A, Höök F. Affinity Purification and Single-Molecule Analysis of Integral Membrane Proteins from Crude Cell-Membrane Preparations. NANO LETTERS 2018; 18:381-385. [PMID: 29231738 DOI: 10.1021/acs.nanolett.7b04227] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The function of integral membrane proteins is critically dependent on their naturally surrounding lipid membrane. Detergent-solubilized and purified membrane proteins are therefore often reconstituted into cell-membrane mimics and analyzed for their function with single-molecule microscopy. Expansion of this approach toward a broad range of pharmaceutically interesting drug targets and biomarkers however remains hampered by the fact that these proteins have low expression levels, and that detergent solubilization and reconstitution often cause protein conformational changes and loss of membrane-specific cofactors, which may impair protein function. To overcome this limitation, we here demonstrate how antibody-modified nanoparticles can be used to achieve affinity purification and enrichment of selected integral membrane proteins directly from cell membrane preparations. Nanoparticles were first bound to the ectodomain of β-secretase 1 (BACE1) contained in cell-derived membrane vesicles. In a subsequent step, these were merged into a continuous supported membrane in a microfluidic channel. Through the extended nanoparticle tag, a weak (∼fN) hydrodynamic force could be applied, inducing directed in-membrane movement of targeted BACE1 exclusively. This enabled selective thousand-fold enrichment of the targeted membrane protein while preserving a natural lipid environment. In addition, nanoparticle-targeting also enabled simultaneous tracking analysis of each individual manipulated protein, revealing how their mobility changed when moved from one lipid environment to another. We therefore believe this approach will be particularly useful for separation in-line with single-molecule analysis, eventually opening up for membrane-protein sorting devices analogous to fluorescence-activated cell sorting.
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Affiliation(s)
- Anders Lundgren
- Department of Physics, Chalmers University of Technology , 41296 Göteborg, Sweden
- Department of Nanobiotechnology, University of Natural Resources and Life Sciences , 1190 Vienna, Austria
| | - Björn Johansson Fast
- Department of Physics, Chalmers University of Technology , 41296 Göteborg, Sweden
| | - Stephan Block
- Department of Physics, Chalmers University of Technology , 41296 Göteborg, Sweden
| | - Björn Agnarsson
- Department of Physics, Chalmers University of Technology , 41296 Göteborg, Sweden
| | - Erik Reimhult
- Department of Nanobiotechnology, University of Natural Resources and Life Sciences , 1190 Vienna, Austria
| | - Anders Gunnarsson
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit, AstraZeneca , 43183 Mölndal, Sweden
| | - Fredrik Höök
- Department of Physics, Chalmers University of Technology , 41296 Göteborg, Sweden
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15
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Abstract
Isolated microfluidic stagnation points – formed within microfluidic interfaces – have come a long way as a tool for characterizing materials, manipulating micro particles, and generating confined flows and localized chemistries.
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Affiliation(s)
- Ayoola T. Brimmo
- Division of Engineering
- New York University Abu Dhabi
- Abu Dhabi
- UAE
- Tandon School of Engineering
| | - Mohammad A. Qasaimeh
- Division of Engineering
- New York University Abu Dhabi
- Abu Dhabi
- UAE
- Tandon School of Engineering
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16
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Dustin ML, Choudhuri K. Signaling and Polarized Communication Across the T Cell Immunological Synapse. Annu Rev Cell Dev Biol 2016; 32:303-325. [PMID: 27501450 DOI: 10.1146/annurev-cellbio-100814-125330] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
T cells express a somatically recombined antigen receptor (αβTCR) that is calibrated during development to respond to changes in peptides displayed by major histocompatibility complex proteins (pMHC) on the surface of antigen-presenting cells (APC). A key characteristic of pMHC for adaptive immunity is the ability to sample internal states of cells and tissues to sensitively detect changes associated with infection, cell derangement, or tissue injury. Physical T cell-APC contact sets up an axis for polarization of TCR, adhesion molecules, kinases, cytoskeletal elements, and organelles inherent in this mode of juxtacrine signaling. The discovery of further lateral organization of the TCR and adhesion molecules into radially symmetric compartments, the immunological synapse, revealed an intersecting plane of symmetry and potential for regulated symmetry breaking to control duration of T cell-APC interactions. In addition to organizing signaling machinery, the immunological synapse directs the polarized transport and secretion of cytokines and cytolytic agents across the synaptic cleft and is a site for the generation and exocytic release of bioactive microvesicles that can functionally affect recipient APC and other cells in the environment. This machinery is coopted by retroviruses, and human immune deficiency virus-1 may even use antigen-specific synapses for infection of healthy T cells. Here, we discuss recent advances in the molecular and cell biological mechanisms of immunological synapse assembly and signaling and its role in intercellular communication across the synaptic cleft.
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Affiliation(s)
- Michael L Dustin
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford OX3 7FY, United Kingdom;
| | - Kaushik Choudhuri
- Department of Microbiology & Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5620;
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Sturzenegger F, Robinson T, Hess D, Dittrich PS. Membranes under shear stress: visualization of non-equilibrium domain patterns and domain fusion in a microfluidic device. SOFT MATTER 2016; 12:5072-5076. [PMID: 27241894 DOI: 10.1039/c6sm00049e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this study we investigate the effect of shear force on lipid membranes induced by external fluid flow. We use giant unilamellar vesicles (GUVs) as simple cell models and chose a ternary lipid mixture that exhibits liquid-ordered and liquid-disordered domains. These domains are stained with different dyes to allow visualization of changes within the membrane after the application of flow. A microfluidic device served as a valuable platform to immobilize the vesicles and apply shear forces of a defined strength. Moreover, integration of valves allowed us to stop the flow instantaneously and visualize the relaxing domain patterns by means of high-resolution fluorescence microscopy. We observed the formation of transient, non-deterministic patterns of the formerly round domains during application of flow. When the flow is stopped, round domains are formed again on a time scale of ms to s. At longer time scales of several seconds to minutes, the domains fuse into larger domains until they reach equilibrium. These processes are accelerated with increasing temperature and vesicles with budding domains do not fuse unless the temperature is elevated. Our results show the strong effect of the flow on the lipid membrane and we believe that this phenomenon plays a crucial role in the processes of mechanotransduction in living cells.
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18
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Chang VT, Fernandes RA, Ganzinger KA, Lee SF, Siebold C, McColl J, Jönsson P, Palayret M, Harlos K, Coles CH, Jones EY, Lui Y, Huang E, Gilbert RJC, Klenerman D, Aricescu AR, Davis SJ. Initiation of T cell signaling by CD45 segregation at 'close contacts'. Nat Immunol 2016; 17:574-582. [PMID: 26998761 PMCID: PMC4839504 DOI: 10.1038/ni.3392] [Citation(s) in RCA: 207] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/29/2015] [Indexed: 12/14/2022]
Abstract
It has been proposed that the local segregation of kinases and the tyrosine phosphatase CD45 underpins T cell antigen receptor (TCR) triggering, but how such segregation occurs and whether it can initiate signaling is unclear. Using structural and biophysical analysis, we show that the extracellular region of CD45 is rigid and extends beyond the distance spanned by TCR-ligand complexes, implying that sites of TCR-ligand engagement would sterically exclude CD45. We also show that the formation of 'close contacts', new structures characterized by spontaneous CD45 and kinase segregation at the submicron-scale, initiates signaling even when TCR ligands are absent. Our work reveals the structural basis for, and the potent signaling effects of, local CD45 and kinase segregation. TCR ligands have the potential to heighten signaling simply by holding receptors in close contacts.
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Affiliation(s)
- Veronica T Chang
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Ricardo A Fernandes
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
| | | | - Steven F Lee
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW
| | - Christian Siebold
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - James McColl
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW
| | - Peter Jönsson
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW
| | - Matthieu Palayret
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW
| | - Karl Harlos
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - Charlotte H Coles
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - E Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - Yuan Lui
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Elizabeth Huang
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Robert J C Gilbert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW
| | - A Radu Aricescu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN
| | - Simon J Davis
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
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19
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Jönsson P, Jönsson B. Hydrodynamic Forces on Macromolecules Protruding from Lipid Bilayers Due to External Liquid Flows. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12708-12718. [PMID: 26523331 DOI: 10.1021/acs.langmuir.5b03421] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
It has previously been observed that an externally applied hydrodynamic shear flow above a fluid lipid bilayer can change the local concentration of macromolecules that are associated with the lipid bilayer. The external liquid flow results in a hydrodynamic force on molecules protruding from the lipid bilayer, causing them to move in the direction of the flow. However, there has been no quantitative study about the magnitude of these forces. We here use finite element simulations to investigate how the magnitude of the external hydrodynamic forces varies with the size and shape of the studied macromolecule. The simulations show that the hydrodynamic force is proportional to the effective hydrodynamic area of the studied molecule, Ahydro, multiplied by the mean hydrodynamic shear stress acting on the membrane surface, σhydro. The parameter Ahydro depends on the size and shape of the studied macromolecule above the lipid bilayer and scales with the cross-sectional area of the molecule. We also investigate how hydrodynamic shielding from other surrounding macromolecules decreases Ahydro when the surface coverage of the shielding macromolecules increases. Experiments where the protein streptavidin is anchored to a supported lipid bilayer on the floor of a microfluidic channel were finally performed at three different surface concentrations, Φ = 1%, 6%, and 10%, where the protein is being moved relative to the lipid bilayer by a liquid flow through the channel. From photobleaching measurements of fluorescently labeled streptavidin we found the experimental drift data to be within good accuracy of the simulated results, less than 12% difference, indicating the validity of the results obtained from the simulations. In addition to giving a deeper insight into how a liquid flow can affect membrane-associated molecules in a lipid bilayer, we also see an interesting potential of using hydrodynamic flow experiments together with the obtained results to study the size and the intermolecular forces between macromolecules in membranes and lipid bilayers.
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Affiliation(s)
- Peter Jönsson
- Division of Physical Chemistry and ‡Division of Biophysical Chemistry, Lund University , SE-22100 Lund, Sweden
| | - Bengt Jönsson
- Division of Physical Chemistry and ‡Division of Biophysical Chemistry, Lund University , SE-22100 Lund, Sweden
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20
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Depoil D, Dustin ML. Force and affinity in ligand discrimination by the TCR. Trends Immunol 2014; 35:597-603. [PMID: 25466309 DOI: 10.1016/j.it.2014.10.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/24/2014] [Accepted: 10/24/2014] [Indexed: 01/30/2023]
Abstract
T cell recognition of antigen is a physical process that requires formation of a cell-cell junction that is rich in active force generation. Recently a biomolecular force probe was used to examine how the T cell receptor (TCR)-pMHC interaction responds to force and the consequences of force-dependent interactions for T cell activation. While adhesion and costimulatory molecules in the immunological synapse impact upon the overall force of the interaction, these results suggest that the TCR uses a force-dependent bond - a catch bond - and that it may therefore be important to consider the TCR-pMHC interaction in isolation in the early phases of the decision process. We discuss here these findings in the context of other work on the impact of forces on the TCR and the quantification of interaction in interfaces.
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Affiliation(s)
- David Depoil
- The Kennedy Institute of Rheumatology, Nuffield Department of Orthopedics and Musculosceletal Sciences, The University of Oxford, Roosevelt Drive, Headington, OX3 7FY, United Kingdom; Helene and Martin Kimmel Center for Biology and Medicine of the Skirball Institute of Biomolecular Medicine, Department of Pathology, New York University School of Medicine, 540 First Avenue, New York, NY 10012, USA
| | - Michael L Dustin
- The Kennedy Institute of Rheumatology, Nuffield Department of Orthopedics and Musculosceletal Sciences, The University of Oxford, Roosevelt Drive, Headington, OX3 7FY, United Kingdom; Helene and Martin Kimmel Center for Biology and Medicine of the Skirball Institute of Biomolecular Medicine, Department of Pathology, New York University School of Medicine, 540 First Avenue, New York, NY 10012, USA.
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21
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Scanning-aperture trapping and manipulation of single charged nanoparticles. Nat Commun 2014; 5:3380. [DOI: 10.1038/ncomms4380] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Accepted: 02/04/2014] [Indexed: 11/08/2022] Open
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22
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Actis P, Maalouf M, Kim HJ, Lohith A, Vilozny B, Seger RA, Pourmand N. Compartmental genomics in living cells revealed by single-cell nanobiopsy. ACS NANO 2014; 8:546-53. [PMID: 24279711 PMCID: PMC3946819 DOI: 10.1021/nn405097u] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The ability to study the molecular biology of living single cells in heterogeneous cell populations is essential for next generation analysis of cellular circuitry and function. Here, we developed a single-cell nanobiopsy platform based on scanning ion conductance microscopy (SICM) for continuous sampling of intracellular content from individual cells. The nanobiopsy platform uses electrowetting within a nanopipette to extract cellular material from living cells with minimal disruption of the cellular milieu. We demonstrate the subcellular resolution of the nanobiopsy platform by isolating small subpopulations of mitochondria from single living cells, and quantify mutant mitochondrial genomes in those single cells with high throughput sequencing technology. These findings may provide the foundation for dynamic subcellular genomic analysis.
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Affiliation(s)
| | | | | | | | | | | | - Nader Pourmand
- Corresponding Author: Department of Biomolecular Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA , +1 (831) 502-7315
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23
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Johansson B, Höök F, Klenerman D, Jönsson P. Label-free measurements of the diffusivity of molecules in lipid membranes. Chemphyschem 2014; 15:486-91. [PMID: 24402971 DOI: 10.1002/cphc.201301136] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Indexed: 11/05/2022]
Abstract
An important and characteristic property of a cell membrane is the lateral mobility of protein molecules in the lipid bilayer. This has conventionally been measured by labeling the molecules with fluorescent markers and monitoring their mobility by different fluorescence-based techniques. However, adding the label to the studied molecule may affect the system, so it is an assumption in almost all experiments that the measured mobility of the biomolecule with its label is the same as that of the unlabeled molecule. However, this assumption is rarely tested due to a lack of suitable methods. In this work, a new technique to perform label-free diffusivity measurements is developed and used to measure the effect of the label for two common protein-lipid systems: 1) streptavidin (SA) coupled to a supported lipid bilayer (SLB) through biotinylated lipids and 2) the extracellular part of the T-cell adhesion protein CD2, coupled to an SLB through histidine tags to nickel-chelating lipids. A measurable (≈12%) decrease in diffusivity is found for both labeled proteins, even though the molecular mass of the label is almost 100 times smaller than those of the proteins (≈50 kDa). The results illustrate the importance of being able to study different biophysical properties of cell membranes and their mimics without relying on fluorescent labels, especially if fluorescent labeling is difficult or is expected to affect the nature of the intermolecular interactions being studied.
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Affiliation(s)
- Björn Johansson
- Department of Applied Physics, Chalmers University of Technology, 41296 Gothenburg (Sweden)
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24
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Ainla A, Gözen I, Hakonen B, Jesorka A. Lab on a Biomembrane: rapid prototyping and manipulation of 2D fluidic lipid bilayers circuits. Sci Rep 2013; 3:2743. [PMID: 24067786 PMCID: PMC3783038 DOI: 10.1038/srep02743] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 08/28/2013] [Indexed: 11/11/2022] Open
Abstract
Lipid bilayer membranes are among the most ubiquitous structures in the living world, with intricate structural features and a multitude of biological functions. It is attractive to recreate these structures in the laboratory, as this allows mimicking and studying the properties of biomembranes and their constituents, and to specifically exploit the intrinsic two-dimensional fluidity. Even though diverse strategies for membrane fabrication have been reported, the development of related applications and technologies has been hindered by the unavailability of both versatile and simple methods. Here we report a rapid prototyping technology for two-dimensional fluidic devices, based on in-situ generated circuits of phospholipid films. In this "lab on a molecularly thin membrane", various chemical and physical operations, such as writing, erasing, functionalization, and molecular transport, can be applied to user-defined regions of a membrane circuit. This concept is an enabling technology for research on molecular membranes and their technological use.
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Affiliation(s)
- Alar Ainla
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 41296 Göteborg, Sweden
| | - Irep Gözen
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 41296 Göteborg, Sweden
- Current address: Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Center for Bioengineering, Department of Medicine, Brigham and Women′s Hospital, Harvard Medical School, Boston, MA, USA
| | - Bodil Hakonen
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 41296 Göteborg, Sweden
| | - Aldo Jesorka
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 41296 Göteborg, Sweden
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25
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Babakinejad B, Jönsson P, López Córdoba A, Actis P, Novak P, Takahashi Y, Shevchuk A, Anand U, Anand P, Drews A, Ferrer-Montiel A, Klenerman D, Korchev YE. Local delivery of molecules from a nanopipette for quantitative receptor mapping on live cells. Anal Chem 2013; 85:9333-42. [PMID: 24004146 DOI: 10.1021/ac4021769] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Using nanopipettes to locally deliver molecules to the surface of living cells could potentially open up studies of biological processes down to the level of single molecules. However, in order to achieve precise and quantitative local delivery it is essential to be able to determine the amount and distribution of the molecules being delivered. In this work, we investigate how the size of the nanopipette, the magnitude of the applied pressure or voltage, which drives the delivery, and the distance to the underlying surface influences the number and spatial distribution of the delivered molecules. Analytical expressions describing the delivery are derived and compared with the results from finite element simulations and experiments on delivery from a 100 nm nanopipette in bulk solution and to the surface of sensory neurons. We then developed a setup for rapid and quantitative delivery to multiple subcellular areas, delivering the molecule capsaicin to stimulate opening of Transient Receptor Potential Vanilloid subfamily member 1 (TRPV1) channels, membrane receptors involved in pain sensation. Overall, precise and quantitative delivery of molecules from nanopipettes has been demonstrated, opening up many applications in biology such as locally stimulating and mapping receptors on the surface of live cells.
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26
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Schäffer TE. Nanomechanics of molecules and living cells with scanning ion conductance microscopy. Anal Chem 2013; 85:6988-94. [PMID: 23692368 DOI: 10.1021/ac400686k] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Hydrodynamic flow through a nanopipet in a scanning ion conductance microscope (SICM) can exert localized forces on a sample surface. These forces can be used for trapping of molecules in lipid bilayers and for mapping the mechanical properties of living cells.
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Affiliation(s)
- Tilman E Schäffer
- University of Tübingen, Department of Physics and LISA+, Tübingen, Germany
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27
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Bao P, Cheetham MR, Roth JS, Blakeston AC, Bushby RJ, Evans SD. On-Chip Alternating Current Electrophoresis in Supported Lipid Bilayer Membranes. Anal Chem 2012; 84:10702-7. [DOI: 10.1021/ac302446w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Peng Bao
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Matthew R. Cheetham
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Johannes S. Roth
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Anita C. Blakeston
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Richard J. Bushby
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Stephen D. Evans
- School of Physics and
Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
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