1
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Manca M, Zhang C, Scheffold F, Salentinig S. Optical tweezer platform for the characterization of pH-triggered colloidal transformations in the oleic acid/water system. J Colloid Interface Sci 2022; 627:610-620. [PMID: 35872418 DOI: 10.1016/j.jcis.2022.07.028] [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: 04/29/2022] [Revised: 06/30/2022] [Accepted: 07/04/2022] [Indexed: 10/17/2022]
Abstract
HYPOTHESIS Soft colloidal particles that respond to their environment have innovative potential for many fields ranging from food and health to biotechnology and oil recovery. The in situ characterisation of colloidal transformations that triggers the functional response remain a challenge. EXPERIMENTS This study demonstrates the combination of an optical micromanipulation platform, polarized optical video microscopy and microfluidics in a comprehensive approach for the analysis of pH-driven structural transformations in emulsions. The new platform, together with synchrotron small angle X-ray scattering, was then applied to research the food-relevant, pH-responsive, oleic acid in water system. FINDINGS The experiments demonstrate structural transformations in individual oleic acid particles from micron-sized onion-type multilamellar oleic acid vesicles at pH 8.6, to nanostructured emulsions at pH < 8.0, and eventually oil droplets at pH < 6.5. The smooth particle-water interface of the onion-type vesicles at pH 8.6 was transformed into a rough particle surface at pH below 7.5. The pH-triggered changes of the interfacial tension at the droplet-water interface together with mass transport owing to structural transformations induced a self-propelled motion of the particle. The results of this study contribute to the fundamental understanding of the structure-property relationship in pH-responsive emulsions for nutrient and drug delivery applications.
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Affiliation(s)
- Marco Manca
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700 Fribourg, Switzerland
| | - Chi Zhang
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland
| | - Frank Scheffold
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland.
| | - Stefan Salentinig
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700 Fribourg, Switzerland.
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2
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Céspedes PF, Beckers D, Dustin ML, Sezgin E. Model membrane systems to reconstitute immune cell signaling. FEBS J 2020; 288:1070-1090. [DOI: 10.1111/febs.15488] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/26/2020] [Accepted: 07/14/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Pablo F. Céspedes
- Kennedy Institute of Rheumatology Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences University of Oxford UK
| | - Daniel Beckers
- MRC Human Immunology Unit MRC Weatherall Institute of Molecular Medicine University of Oxford UK
| | - Michael L. Dustin
- Kennedy Institute of Rheumatology Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences University of Oxford UK
| | - Erdinc Sezgin
- MRC Human Immunology Unit MRC Weatherall Institute of Molecular Medicine University of Oxford UK
- Science for Life Laboratory Department of Women's and Children's Health Karolinska Institutet Stockholm Sweden
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3
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Li Q, Tseng KF, King SJ, Qiu W, Xu J. A fluid membrane enhances the velocity of cargo transport by small teams of kinesin-1. J Chem Phys 2018; 148:123318. [PMID: 29604873 DOI: 10.1063/1.5006806] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Kinesin-1 (hereafter referred to as kinesin) is a major microtubule-based motor protein for plus-end-directed intracellular transport in live cells. While the single-molecule functions of kinesin are well characterized, the physiologically relevant transport of membranous cargos by small teams of kinesins remains poorly understood. A key experimental challenge remains in the quantitative control of the number of motors driving transport. Here we utilized "motile fraction" to overcome this challenge and experimentally accessed transport by a single kinesin through the physiologically relevant transport by a small team of kinesins. We used a fluid lipid bilayer to model the cellular membrane in vitro and employed optical trapping to quantify the transport of membrane-enclosed cargos versus traditional membrane-free cargos under identical conditions. We found that coupling motors via a fluid membrane significantly enhances the velocity of cargo transport by small teams of kinesins. Importantly, enclosing a cargo in a fluid lipid membrane did not impact single-kinesin transport, indicating that membrane-dependent velocity enhancement for team-based transport arises from altered interactions between kinesins. Our study demonstrates that membrane-based coupling between motors is a key determinant of kinesin-based transport. Enhanced velocity may be critical for fast delivery of cargos in live cells.
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Affiliation(s)
- Qiaochu Li
- Department of Physics, University of California, Merced, California 95343, USA
| | - Kuo-Fu Tseng
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Stephen J King
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, Florida 32827, USA
| | - Weihong Qiu
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jing Xu
- Department of Physics, University of California, Merced, California 95343, USA
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4
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Schreuer C, Vandewiele S, Strubbe F, Neyts K, Beunis F. Electric field induced charging of colloidal particles in a nonpolar liquid. J Colloid Interface Sci 2018; 515:248-254. [DOI: 10.1016/j.jcis.2018.01.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 01/09/2018] [Accepted: 01/10/2018] [Indexed: 10/18/2022]
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5
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Spherical Nanoparticle Supported Lipid Bilayers: A Tool for Modeling Protein Interactions with Curved Membranes. Methods Mol Biol 2017. [PMID: 29151206 DOI: 10.1007/978-1-4939-7386-6_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Mechanistic studies of protein-membrane interactions can be complicated by the limitations of the membrane model system chosen. Many of these limitations can be overcome by using a spherical silica nanoparticle to support the membrane. In this chapter, we present a detailed protocol for the construction of spherical nanoparticle supported lipid bilayers (SSLBs), with discussion of methods to improve production.
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6
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Fu R, Gill RL, Kim EY, Briley NE, Tyndall ER, Xu J, Li C, Ramamurthi KS, Flanagan JM, Tian F. Spherical nanoparticle supported lipid bilayers for the structural study of membrane geometry-sensitive molecules. J Am Chem Soc 2015; 137:14031-14034. [PMID: 26488086 DOI: 10.1021/jacs.5b08303] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many essential cellular processes including endocytosis and vesicle trafficking require alteration of membrane geometry. These changes are usually mediated by proteins that can sense and/or induce membrane curvature. Using spherical nanoparticle supported lipid bilayers (SSLBs), we characterize how SpoVM, a bacterial development factor, interacts with differently curved membranes by magic angle spinning solid-state NMR. Our results demonstrate that SSLBs are an effective system for structural and topological studies of membrane geometry-sensitive molecules.
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Affiliation(s)
- Riqiang Fu
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Richard L Gill
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
| | - Edward Y Kim
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Nicole E Briley
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
| | - Erin R Tyndall
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
| | - Jie Xu
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
| | - Conggang Li
- National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Kumaran S Ramamurthi
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - John M Flanagan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
| | - Fang Tian
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, Pennsylvania 17033, United States
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7
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Meyer RA, Sunshine JC, Green JJ. Biomimetic particles as therapeutics. Trends Biotechnol 2015; 33:514-524. [PMID: 26277289 DOI: 10.1016/j.tibtech.2015.07.001] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 07/03/2015] [Accepted: 07/07/2015] [Indexed: 11/28/2022]
Abstract
In recent years, there have been major advances in the development of novel nanoparticle- and microparticle-based therapeutics. An emerging paradigm is the incorporation of biomimetic features into these synthetic therapeutic constructs to enable them to better interface with biological systems. Through the control of size, shape, and material consistency, particle cores have been generated that better mimic natural cells and viruses. In addition, there have been significant advances in biomimetic surface functionalization of particles through the integration of bio-inspired artificial cell membranes and naturally derived cell membranes. Biomimetic technologies enable therapeutic particles to have increased potency to benefit human health.
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Affiliation(s)
- Randall A Meyer
- Department of Biomedical Engineering, Translational Tissue Engineering Center, and Institute for Nanobiotechnology, Johns Hopkins School of Medicine, 400 N Broadway, Smith 5017, Baltimore MD, 21231, USA
| | - Joel C Sunshine
- Department of Biomedical Engineering, Translational Tissue Engineering Center, and Institute for Nanobiotechnology, Johns Hopkins School of Medicine, 400 N Broadway, Smith 5017, Baltimore MD, 21231, USA
| | - Jordan J Green
- Department of Biomedical Engineering, Translational Tissue Engineering Center, and Institute for Nanobiotechnology, Johns Hopkins School of Medicine, 400 N Broadway, Smith 5017, Baltimore MD, 21231, USA.,Departments of Materials Science and Engineering, Oncology, Ophthalmology, and Neurosurgery, Johns Hopkins School of Medicine, 400 N Broadway, Smith 5017, Baltimore MD, 21231, USA
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8
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Label-free DNA sequencing using Millikan detection. Anal Biochem 2015; 487:1-7. [PMID: 26151683 DOI: 10.1016/j.ab.2015.06.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/22/2015] [Accepted: 06/30/2015] [Indexed: 11/20/2022]
Abstract
A label-free method for DNA sequencing based on the principle of the Millikan oil drop experiment was developed. This sequencing-by-synthesis approach sensed increases in bead charge as nucleotides were added by a polymerase to DNA templates attached to beads. The balance between an electrical force, which was dependent on the number of nucleotide charges on a bead, and opposing hydrodynamic drag and restoring tether forces resulted in a bead velocity that was a function of the number of nucleotides attached to the bead. The velocity of beads tethered via a polymer to a microfluidic channel and subjected to an oscillating electric field was measured using dark-field microscopy and used to determine how many nucleotides were incorporated during each sequencing-by-synthesis cycle. Increases in bead velocity of approximately 1% were reliably detected during DNA polymerization, allowing for sequencing of short DNA templates. The method could lead to a low-cost, high-throughput sequencing platform that could enable routine sequencing in medical applications.
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9
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Brans T, Strubbe F, Schreuer C, Vandewiele S, Neyts K, Beunis F. Joule heating monitoring in a microfluidic channel by observing the Brownian motion of an optically trapped microsphere. Electrophoresis 2015; 36:2102-9. [PMID: 25963750 DOI: 10.1002/elps.201500144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 04/23/2015] [Accepted: 04/24/2015] [Indexed: 12/11/2022]
Abstract
Electric fields offer a variety of functionalities to Lab-on-a-Chip devices. The use of these fields often results in significant Joule heating, affecting the overall performance of the system. Precise knowledge of the temperature profile inside a microfluidic device is necessary to evaluate the implications of heat dissipation. This article demonstrates how an optically trapped microsphere can be used as a temperature probe to monitor Joule heating in these devices. The Brownian motion of the bead at room temperature is compared with the motion when power is dissipated in the system. This gives an estimate of the temperature increase at a specific location in a microfluidic channel. We demonstrate this method with solutions of different ionic strengths, and establish a precision of 0.9 K and an accuracy of 15%. Furthermore, it is demonstrated that transient heating processes can be monitored with this technique, albeit with a limited time resolution.
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Affiliation(s)
- Toon Brans
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
| | - Filip Strubbe
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
| | - Caspar Schreuer
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
| | - Stijn Vandewiele
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
| | - Kristiaan Neyts
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
| | - Filip Beunis
- Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.,Center for Nano and Biophotonics (NB-photonics), Ghent University, Ghent, Belgium
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10
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Pesce G, Rusciano G, Zito G, Sasso A. Simultaneous measurements of electrophoretic and dielectrophoretic forces using optical tweezers. OPTICS EXPRESS 2015; 23:9363-9368. [PMID: 25968766 DOI: 10.1364/oe.23.009363] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Herein, charged microbeads handled with optical tweezers are used as a sensitive probe for simultaneous measurements of electrophoretic and dielectrophoretic forces. We first determine the electric charge carried by a single bead by keeping it in a predictable uniform electric field produced by two parallel planar electrodes, then, we examine same bead's response in proximity to a tip electrode. In this case, besides electric forces, the bead simultaneously experiences non-negligible dielectrophoretic forces produced by the strong electric field gradient. The stochastic and deterministic motions of the trapped bead are theoretically and experimentally analysed in terms of the autocorrelation function. By fitting the experimental data, we are able to extract simultaneously the spatial distribution of electrophoretic and dielectrophoretic forces around the tip. Our approach can be used for determining actual, total force components in the presence of high-curvature electrodes or metal scanning probe tips.
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11
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Strubbe F, Vandewiele S, Schreuer C, Beunis F, Drobchak O, Brans T, Neyts K. Characterizing and tracking individual colloidal particles using Fourier-Bessel image decomposition. OPTICS EXPRESS 2014; 22:24635-24645. [PMID: 25322038 DOI: 10.1364/oe.22.024635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We use Fourier-Bessel Image Decomposition (FBID) of microscopy images to investigate the size, refractive index and 3-dimensional position of individual colloidal microspheres. With measurements of monodisperse polystyrene and poly(methyl methacrylate) particles we achieve a resolution of 1% in size and 0.2% in refractive index for a single image which is sufficient for accurate in situ characterization of polydisperse colloids. Also the binding of avidin molecules to individual biotinylated polystyrene particles is resolved. Finally, the FBID method offers a straightforward approach to 3-dimensional out-of-focus tracking. Here, the z-position of a freely diffusing particle is calculated by applying the statistics of Brownian motion to its set of Fourier-Bessel coefficients.
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12
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Leiske DL, Chow A, Dettloff R, Farinas J. Single-molecule enzymology based on the principle of the Millikan oil drop experiment. Anal Biochem 2013; 448:30-7. [PMID: 24291542 DOI: 10.1016/j.ab.2013.11.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 11/09/2013] [Accepted: 11/15/2013] [Indexed: 10/26/2022]
Abstract
The ability to monitor the progress of single-molecule enzyme reactions is often limited by the need to use fluorogenic substrates. A method based on the principle of the Millikan oil drop experiment was developed to monitor the change in charge of substrates bound to a nanoparticle and offers a means of detecting single-enzyme reactions without fluorescence detection. As a proof of principle of the ability to monitor reactions that result in a change in substrate charge, polymerization on a single DNA template was detected. A custom oligonucleotide was synthesized that allowed for the attachment of single DNA templates to gold nanoparticles with a single polymer tether. The nanoparticles were then tethered to the surface of a microfluidic channel where the positions of the nanoparticles, subjected to an oscillating electric field, were monitored using dark field microscopy. With short averaging times, the signal-to-noise level was low enough to discriminate changes in charge of less than 1.2%. Polymerization of a long DNA template demonstrated the ability to use the system to monitor single-molecule enzymatic activity. Finally, nanoparticle surfaces were modified with thiolated moieties to reduce and/or shield the number of unproductive charges and allow for improved sensitivity.
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Affiliation(s)
| | - Andrea Chow
- Promega BioSystems, Sunnyvale, CA 94085, USA
| | - Roger Dettloff
- Caerus Molecular Diagnostics, Mountain View, CA 94043, USA
| | - Javier Farinas
- Caerus Molecular Diagnostics, Mountain View, CA 94043, USA.
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13
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Pesce G, Lisbino V, Rusciano G, Sasso A. Optical manipulation of charged microparticles in polar fluids. Electrophoresis 2013; 34:3141-9. [DOI: 10.1002/elps.201300214] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 07/17/2013] [Accepted: 08/22/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Giuseppe Pesce
- Dipartimento di Fisica, Università degli Studi di Napoli; Complesso Universitario Monte S. Angelo; Napoli Italy
| | - Vincenzo Lisbino
- Dipartimento di Fisica, Università degli Studi di Napoli; Complesso Universitario Monte S. Angelo; Napoli Italy
| | - Giulia Rusciano
- Dipartimento di Fisica, Università degli Studi di Napoli; Complesso Universitario Monte S. Angelo; Napoli Italy
| | - Antonio Sasso
- Dipartimento di Fisica, Università degli Studi di Napoli; Complesso Universitario Monte S. Angelo; Napoli Italy
- Consiglio Nazionale delle Ricerche (CNR); Istituto Nazionale di Ottica - Sezione di Napoli; Pozzuoli Italy
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14
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Pyrpassopoulos S, Shuman H, Ostap EM. Method for measuring single-molecule adhesion forces and attachment lifetimes of protein-membrane interactions. Methods Mol Biol 2013; 1046:389-403. [PMID: 23868602 DOI: 10.1007/978-1-62703-538-5_24] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Many proteins that reside in the cytoplasm bind directly to cell membranes and play roles in signaling, adhesion, metabolism, cell structure, and cell motility. Several of these membrane-binding proteins, especially cytoskeletal proteins, have mechanical functions that result in the transmission of forces to the plasma membrane and organelle-membranes. Despite the importance of these interactions, remarkably little is known about the mechanical properties of the bonds between membranes and proteins. In this chapter, we describe a single-molecule, optical-trapping method for the measurement of protein-membrane adhesion forces and force-dependent attachment-lifetimes.
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Affiliation(s)
- Serapion Pyrpassopoulos
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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15
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Smith GN, Eastoe J. Controlling colloid charge in nonpolar liquids with surfactants. Phys Chem Chem Phys 2013. [DOI: 10.1039/c2cp42625k] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Todd BA, Cohen JA. Separability of electrostatic and hydrodynamic forces in particle electrophoresis. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:032401. [PMID: 22060435 DOI: 10.1103/physreve.84.032401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Indexed: 05/31/2023]
Abstract
By use of optical tweezers we explicitly measure the electrostatic and hydrodynamic forces that determine the electrophoretic mobility of a charged colloidal particle. We test the ansatz of O'Brien and White [J. Chem. Soc. Faraday II 74, 1607 (1978)] that the electrostatically and hydrodynamically coupled electrophoresis problem is separable into two simpler problems: (1) a particle held fixed in an applied electric field with no flow field and (2) a particle held fixed in a flow field with no applied electric field. For a system in the Helmholtz-Smoluchowski and Debye-Hückel regimes, we find that the electrostatic and hydrodynamic forces measured independently accurately predict the electrophoretic mobility within our measurement precision of 7%; the O'Brien and White ansatz holds under the conditions of our experiment.
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Affiliation(s)
- Brian A Todd
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA.
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17
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Ren W, Liu J, Guo S, Wang E. SERS imaging for label-free detection of the phospholipids distribution in hybrid lipid membrane. Sci China Chem 2011. [DOI: 10.1007/s11426-011-4312-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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18
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Gutsche C, Elmahdy MM, Kegler K, Semenov I, Stangner T, Otto O, Ueberschär O, Keyser UF, Krueger M, Rauscher M, Weeber R, Harting J, Kim YW, Lobaskin V, Netz RR, Kremer F. Micro-rheology on (polymer-grafted) colloids using optical tweezers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:184114. [PMID: 21508470 DOI: 10.1088/0953-8984/23/18/184114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.
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Affiliation(s)
- C Gutsche
- Institute of Experimental Physics I, Leipzig University, Linnéstrasse 5, D-04103, Leipzig, Germany
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19
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Pyrpassopoulos S, Shuman H, Ostap EM. Single-molecule adhesion forces and attachment lifetimes of myosin-I phosphoinositide interactions. Biophys J 2011; 99:3916-22. [PMID: 21156133 DOI: 10.1016/j.bpj.2010.10.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 10/10/2010] [Accepted: 10/27/2010] [Indexed: 11/19/2022] Open
Abstract
Phosphoinositides regulate the activities and localization of many cytoskeletal proteins involved in crucial biological processes, including membrane-cytoskeleton adhesion. Yet little is known about the mechanics of protein-phosphoinositide interactions, or about the membrane-attachment mechanics of any peripheral membrane proteins. Myosin-Ic (myo1c) is a molecular motor that links membranes to the cytoskeleton via phosphoinositide binding, so it is particularly important to understand the mechanics of its membrane attachment. We used optical tweezers to measure the strength and attachment lifetime of single myo1c molecules as they bind beads coated with a bilayer of 2% phosphatidylinositol 4,5-bisphosphate and 98% phosphatidylcholine. Adhesion forces measured under ramp-load ranged between 5.5 and 16 pN at loading rates between 250 and 1800 pN/s. Dissociation rates increased linearly with constant force (0.3-2.5 pN), with rates exceeding 360 s(-1) at 2.5 pN. Attachment lifetimes calculated from adhesion force measurements were loading-rate-dependent, suggesting nonadiabatic behavior during pulling. The adhesion forces of myo1c with phosphoinositides are greater than the motors stall forces and are within twofold of the force required to extract a lipid molecule from the membrane. However, attachment durations are short-lived, suggesting that phosphoinositides alone do not provide the mechanical stability required to anchor myo1c to membranes during multiple ATPase cycles.
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Affiliation(s)
- Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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20
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van Heiningen JA, Hill RJ. Polymer adsorption onto a micro-sphere from optical tweezers electrophoresis. LAB ON A CHIP 2011; 11:152-162. [PMID: 20957244 DOI: 10.1039/c005217p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We explore the design and operation of an optical-tweezers electrophoresis apparatus to resolve polymer adsorption dynamics onto a single micro-sphere in a micro-fluidic environment. Our model system represents a broader class of micro-fluidic electrophoresis experiments for biosensing and fundamental colloid and surface science diagnostics. We track the adsorption of 100 kDa poly(ethylene oxide) homopolymer onto a colloidal silica sphere that is optically trapped in a crossed parallel-plate micro-channel. The adsorption dynamics are probed on the ∼1 μm particle length scale with ∼1 s temporal resolution. Because the particle electrophoretic mobility and channel electro-osmotic flow are exquisitely sensitive to the polymer layer hydrodynamic thickness, particle dynamics can be complicated by polymer adsorption onto the micro-channel walls. Nevertheless, using experiments and a theoretical model of electro-osmotic flow in channels with non-uniform wall ζ-potentials, we show that such influences can be mitigated by adopting a symmetrical flow configuration. The equilibrium hydrodynamic layer thickness of 100 kDa poly(ethylene oxide) on colloidal silica is ∼10 nm at polymer concentrations ≳10 ppm (weight percent), with the dynamics reflecting polymer solution concentration, flow rate, and polydispersity.
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Affiliation(s)
- Jan A van Heiningen
- Department of Chemical Engineering, McGill University, Montreal, Quebec H3A 2B2, Canada
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van Heiningen JA, Mohammadi A, Hill RJ. Dynamic electrical response of colloidal micro-spheres in compliant micro-channels from optical tweezers velocimetry. LAB ON A CHIP 2010; 10:1907-1921. [PMID: 20508875 DOI: 10.1039/c002646h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report the dynamic response of colloidal silica in aqueous electrolytes to oscillatory electric fields at frequencies up to approximately 50 kHz. Particles were optically trapped at various positions across the gap of straight and crossed parallel-plate micro-channels. Using back-focal-plane interferometry, we measured the apparent electrophoretic mobility in NaCl and CaCl(2) electrolytes over a wide range of salt concentrations. The mobility has a strikingly complex dependence on channel position and forcing frequency that cannot be understood on the basis of standard electrokinetic theory for rigid micro-channels. We ascribe the anomalous dynamics to coupling of electro-osmotic flow and elastic modes of the micro-channel and auxiliary hardware. By integrating into the classical theory a complex-valued channel-compliance parameter--that modulates the phase and amplitude of the dynamic electro-osmotic flow--theoretical interpretation of the frequency-dependent mobility furnishes robust measurements of the intrinsic particle electrophoretic mobility and the upper and lower channel-wall zeta-potentials. Together, the single-particle experiments and accompanying theoretical interpretation highlight--for the first time--how spatially and temporally resolved particle dynamics are exquisitely sensitive to channel compliance. Accordingly, specially designed compliant micro-fluidic channels and flexible tube connections might be tailored for dynamic electrical micro-fluidic diagnostic applications.
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Affiliation(s)
- Jan A van Heiningen
- Department of Chemical Engineering, McGill University, Montreal, Quebec H3A 2B2, Canada
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22
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Chemburu S, Fenton K, Lopez GP, Zeineldin R. Biomimetic silica microspheres in biosensing. Molecules 2010; 15:1932-57. [PMID: 20336023 PMCID: PMC6257317 DOI: 10.3390/molecules15031932] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 03/16/2010] [Accepted: 03/17/2010] [Indexed: 11/16/2022] Open
Abstract
Lipid vesicles spontaneously fuse and assemble into a lipid bilayer on planar or spherical silica surfaces and other substrates. The supported lipid bilayers (SLBs) maintain characteristics of biological membranes, and are thus considered to be biomembrane mimetic systems that are stable because of the underlying substrate. Examples of their shared characteristics with biomembranes include lateral fluidity, barrier formation to ions and molecules, and their ability to incorporate membrane proteins into them. Biomimetic silica microspheres consisting of SLBs on solid or porous silica microspheres have been utilized for different biosensing applications. The advantages of such biomimetic microspheres for biosensing include their increased surface area to volume ratio which improves the detection limits of analytes, and their amenability for miniaturization, multiplexing and high throughput screening. This review presents examples and formats of using such biomimetic solid or porous silica microspheres in biosensing.
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Affiliation(s)
- Sireesha Chemburu
- Center for Biomedical Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Kyle Fenton
- Center for Biomedical Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Gabriel P. Lopez
- Center for Biomedical Engineering, University of New Mexico, Albuquerque, NM 87131, USA
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
- Department of Mechanical Engineering & Materials Science, Duke University, Durham, NC 27708, USA
| | - Reema Zeineldin
- Department of Pharmaceutical Sciences, Massachusetts College of Pharmacy and Health Sciences, 19 Foster Street, Worcester, MA 01608, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-508-373-5762; Fax: +1- 508-890-5618
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23
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Controlled solvent-exchange deposition of phospholipid membranes onto solid surfaces. Biointerphases 2010; 5:1-8. [DOI: 10.1116/1.3319326] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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24
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Kahl V, Gansen A, Galneder R, Rädler JO. Microelectrophoresis in a laser trap: a platform for measuring electrokinetic interactions and flow properties within microstructures. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2009; 80:073704. [PMID: 19655953 DOI: 10.1063/1.3169511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We describe a combination of microelectrophoresis and laser-trap methodology to accurately measure the electric force acting on a charged microsphere which is trapped in an optical tweezer. This field/trap apparatus allows measuring of the zeta potential with submillivolt accuracy and high temporal resolution. The combination with stop-flow techniques in principle provides a mean to observe adsorption or enzyme kinetics with single molecule sensitivity. We show that it is possible to accurately profile the position and frequency dependent hydrodynamic and electro-osmotic flow inside a microchannel structure of dimensions typically used in microfluidic applications without the need of fluorescent markers. We found good agreement to the theory of electrophoretic flow when retardation effects for rapidly alternating electric fields are included.
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Affiliation(s)
- V Kahl
- ibidi GmbH, Am Klopferspitz 19, 82152 München, Germany
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25
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Pucadyil TJ, Schmid SL. Real-time visualization of dynamin-catalyzed membrane fission and vesicle release. Cell 2008; 135:1263-75. [PMID: 19084268 DOI: 10.1016/j.cell.2008.11.020] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 09/02/2008] [Accepted: 11/18/2008] [Indexed: 01/27/2023]
Abstract
The GTPase dynamin assembles at the necks of budded vesicles in vivo and functions in membrane fission. We have developed fluid supported bilayers with excess membrane reservoir, (SUPER) templates, to assay vesicle formation and membrane fission. Consistent with previous studies, in the absence of GTP, dynamin assembles in spirals, forming long membrane tubules. GTP addition triggers disassembly, but not membrane fission, arguing against models in which fission is mediated by concerted and global GTP-driven conformational changes. In contrast, under physiological conditions in the constant presence of GTP, dynamin mediates membrane fission. Under these conditions, fluorescently labeled dynamin cooperatively organizes into self-limited assemblies that continuously cycle at the membrane and drive vesicle release. When visualized at the necks of emergent vesicles, self-limited dynamin assemblies display intensity fluctuations and persist for variable time periods before fission. Thus, self-limited assemblies of dynamin generated in the constant presence of GTP catalyze membrane fission.
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Affiliation(s)
- Thomas J Pucadyil
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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26
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27
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Biosensors based on release of compounds upon disruption of lipid bilayers supported on porous microspheres. Biointerphases 2008; 3:38. [DOI: 10.1116/1.2918743] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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28
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Strubbe F, Beunis F, Neyts K. Detection of elementary charges on colloidal particles. PHYSICAL REVIEW LETTERS 2008; 100:218301. [PMID: 18518642 DOI: 10.1103/physrevlett.100.218301] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Indexed: 05/26/2023]
Abstract
We have succeeded in determining the charge of individual colloidal particles with resolution higher than the elementary charge. The number of elementary charges on a particle is obtained from the analysis of optical tracking data of weakly charged silica spheres in an electric field in a nonpolar medium. The analysis also yields an accurate value of the particle size. Measurement of the charge as a function of time reveals events in which the particle loses or gains an elementary charge due to ionization or recombination processes at the surface.
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Affiliation(s)
- Filip Strubbe
- Ghent University, Electronics and Information Systems, Sint-Pietersnieuwstraat 41, Ghent B-9000, Belgium
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29
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Otto O, Gutsche C, Kremer F, Keyser UF. Optical tweezers with 2.5 kHz bandwidth video detection for single-colloid electrophoresis. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:023710. [PMID: 18315308 DOI: 10.1063/1.2884147] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We developed an optical tweezers setup to study the electrophoretic motion of colloids in an external electric field. The setup is based on standard components for illumination and video detection. Our video based optical tracking of the colloid motion has a time resolution of 0.2 ms, resulting in a bandwidth of 2.5 kHz. This enables calibration of the optical tweezers by Brownian motion without applying a quadrant photodetector. We demonstrate that our system has a spatial resolution of 0.5 nm and a force sensitivity of 20 fN using a Fourier algorithm to detect periodic oscillations of the trapped colloid caused by an external ac field. The electrophoretic mobility and zeta potential of a single colloid can be extracted in aqueous solution avoiding screening effects common for usual bulk measurements.
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Affiliation(s)
- Oliver Otto
- Institute of Experimental Physics I, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany
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30
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Gutsche C, Keyser UF, Kegler K, Kremer F, Linse P. Forces between single pairs of charged colloids in aqueous salt solutions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:031403. [PMID: 17930243 DOI: 10.1103/physreve.76.031403] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 06/29/2007] [Indexed: 05/25/2023]
Abstract
Forces between single pairs of negatively charged micrometer-sized colloids in aqueous solutions of monovalent, divalent, or trivalent counter-ions at varying concentrations have been measured by employing optical tweezers. The experimental data have been analyzed by using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and a numerical solution of the Poisson-Boltzmann (PB) equation. With monovalent counterions, the data are well described by the DLVO and PB theories, suggesting that the DLVO theory is adequate to describe the colloidal forces at these conditions. At higher counter-ion valence, the approximations within the two theories become evident.
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Affiliation(s)
- C Gutsche
- Institut für Experimentelle Physik I der Universität Leipzig, Germany
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31
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Tong L, Lu Y, Lee RJ, Cheng JX. Imaging Receptor-Mediated Endocytosis with a Polymeric Nanoparticle-Based Coherent Anti-Stokes Raman Scattering Probe. J Phys Chem B 2007; 111:9980-5. [PMID: 17663581 DOI: 10.1021/jp073478z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Coherent anti-Stokes Raman scattering (CARS) microscopy was used to visualize receptor-mediated endocytosis and intracellular trafficking with the aid of a CARS probe. The probe was made of 200-nm polystyrene particles encapsulated in folate-targeted liposomes. By tuning (omega(p) - omega(s)) to 3045 cm(-1), which corresponds to the aromatic C-H stretching vibration, the polystyrene nanoparticles with a high density of aromatic C-H bonds were detected with a high signal-to-noise ratio, while the epi-detected CARS signal from cellular organelles was cancelled by the destructive interference between the resonant contribution from the aliphatic C-H vibration and the nonresonant contribution. Without any photobleaching, the CARS probe allowed single-particle tracking analysis of intracellular endosome transport. No photodamage to cells was observed under the current experimental conditions. These results show the advantages and potential of using a CARS probe to study cellular processes.
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Affiliation(s)
- Ling Tong
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, USA
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32
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Seth Roberts G, Wood TA, Frith WJ, Bartlett P. Direct measurement of the effective charge in nonpolar suspensions by optical tracking of single particles. J Chem Phys 2007; 126:194503. [PMID: 17523818 DOI: 10.1063/1.2734968] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The authors develop an ultrasensitive method for the measurement of the charge carried by a colloidal particle in a nonpolar suspension. The technique uses the phenomenon of the resonance of a particle held in an optical tweezer trap and driven by a sinusoidal electric field. The trapped particle forms a strongly damped harmonic oscillator whose fluctuations are a function of gamma, the ratio of the root-mean-square average of the electric and thermal forces on the particle. At low applied fields (gamma<<1) the particle is confined to the optical axis, while at high fields (gamma>>1) the probability distribution of the particle is double peaked. The periodically modulated thermal fluctuations are measured with nanometer sensitivity using an interferometric position detector. Charges, as low as a few elementary charges, can be measured with an uncertainty of about 0.25 e. This is significantly better than previous techniques and opens up new possibilities for the study of nonpolar suspensions.
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Affiliation(s)
- G Seth Roberts
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
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33
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Tanaka M, Hermann J, Haase I, Fischer M, Boxer SG. Frictional drag and electrical manipulation of recombinant proteins in polymer-supported membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:5638-44. [PMID: 17408291 DOI: 10.1021/la0628219] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We establish a lipid monolayer supported by a polymer interface that offers advantages over conventional solid-supported membranes for determining the frictional drag at the membrane-protein interface as well as for electric field manipulation of membrane-anchored proteins. Polymer-supported monolayers with functional lipid anchors allow for the specific docking of His-tagged green fluorescent protein variants (His-EGFP and His-DsRed tetramer) onto the membrane surface at a defined surface density. In the first part, we measure the lateral diffusion coefficients of lipids and proteins and calculate the frictional drag at the protein-membrane interface. The second part deals with the electric field-induced accumulation of recombinant proteins on a patterned surface. The mean drift velocity of proteins, which can be obtained analytically from the shape of the steady-state concentration gradient, can be controlled by tuning the interplay of electrophoresis and electroosmosis. The results demonstrate the potential of such molecular constructs for the local functionalization of solid substrates with membrane-associated proteins.
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Affiliation(s)
- Motomu Tanaka
- Department of Physics, Technical University of Munich, D-85748 Garching, Germany.
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34
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Davis RW, Flores A, Barrick TA, Cox JM, Brozik SM, Lopez GP, Brozik JA. Nanoporous microbead supported bilayers: stability, physical characterization, and incorporation of functional transmembrane proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:3864-72. [PMID: 17315891 DOI: 10.1021/la062576t] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The introduction of functional transmembrane proteins into supported bilayer-based biomimetic systems presents a significant challenge for biophysics. Among the various methods for producing supported bilayers, liposomal fusion offers a versatile method for the introduction of membrane proteins into supported bilayers on a variety of substrates. In this study, the properties of protein containing unilamellar phosphocholine lipid bilayers on nanoporous silica microspheres are investigated. The effects of the silica substrate, pore structure, and the substrate curvature on the stability of the membrane and the functionality of the membrane protein are determined. Supported bilayers on porous silica microspheres show a significant increase in surface area on surfaces with structures in excess of 10 nm as well as an overall decrease in stability resulting from increasing pore size and curvature. Comparison of the liposomal and detergent-mediated introduction of purified bacteriorhodopsin (bR) and the human type 3 serotonin receptor (5HT3R) are investigated focusing on the resulting protein function, diffusion, orientation, and incorporation efficiency. In both cases, functional proteins are observed; however, the reconstitution efficiency and orientation selectivity are significantly enhanced through detergent-mediated protein reconstitution. The results of these experiments provide a basis for bulk ionic and fluorescent dye-based compartmentalization assays as well as single-molecule optical and single-channel electrochemical interrogation of transmembrane proteins in a biomimetic platform.
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Affiliation(s)
- Ryan W Davis
- Department of Chemistry, The University of New Mexico, Albuquerque, New Mexico 87131, USA
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35
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Abstract
Lipid-bilayer membranes supported on solid substrates are widely used as cell-surface models that connect biological and artificial materials. They can be placed either directly on solids or on ultrathin polymer supports that mimic the generic role of the extracellular matrix. The tools of modern genetic engineering and bioorganic chemistry make it possible to couple many types of biomolecule to supported membranes. This results in sophisticated interfaces that can be used to control, organize and study the properties and function of membranes and membrane-associated proteins. Particularly exciting opportunities arise when these systems are coupled with advanced semiconductor technology.
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Affiliation(s)
- Motomu Tanaka
- Department of Physics, Technical University of Munich, D-85748 Garching, Germany.
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36
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Katagiri K, Caruso F. Functionalization of Colloids with Robust Inorganic-Based Lipid Coatings. Macromolecules 2004. [DOI: 10.1021/ma048706r] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kiyofumi Katagiri
- Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia
| | - Frank Caruso
- Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia
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37
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Katagiri K, Hashizume M, Kikuchi JI, Taketani Y, Murakami M. Creation of asymmetric bilayer membrane on monodispersed colloidal silica particles. Colloids Surf B Biointerfaces 2004; 38:149-53. [PMID: 15542317 DOI: 10.1016/j.colsurfb.2004.05.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2003] [Accepted: 05/19/2004] [Indexed: 10/26/2022]
Abstract
Novel organic-inorganic nanohybrids, each having an inorganic core covered with an asymmetric lipid-bilayer membrane, were prepared through two-step self-assembling of a Cerasome-forming organoalkoxysilane lipid, N-[N-(3-triethoxysilyl)propylsuccinamoyl]dihexadecylamine (1), as the inner layer with an appropriate bilayer-forming amphiphile, N,N-dihexadecyl-N alpha-[6-(trimethylammonio)hexanoyl]alaninamide bromide (2), sodium N,N-dihexadecyl-N alpha-(6-sulfohexanoyl)alaninamide (3), or dimyristoylphosphatidylcholine (DMPC; 4), as the outer layer on a monodispersed colloidal silica particle. The particle thus obtained was characterized by various physical measurements, such as FT-IR spectroscopy, transmission electron microscopy, differential scanning calorimetry, and zeta-potential measurements. These data strongly supported the successful formation of the asymmetric bilayer structure on the surface of the silica particle. The current method is widely applicable to various kinds of hybrids of inorganic particles with lipid membrane components.
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Affiliation(s)
- Kiyofumi Katagiri
- Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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38
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Hill RJ. Hydrodynamics and electrokinetics of spherical liposomes with coatings of terminally anchored poly(ethylene glycol): numerically exact electrokinetics with self-consistent mean-field polymer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:051406. [PMID: 15600617 DOI: 10.1103/physreve.70.051406] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Revised: 07/08/2004] [Indexed: 05/07/2023]
Abstract
A detailed theoretical model is presented to interpret electrokinetic experiments performed on colloids with uncharged polymer layers. The methodology removes many of the degrees of freedom that otherwise have to be accounted for by adopting multiple empirical fitting parameters. Furthermore, the level of detail provides a firm basis for future studies examining liposome surface chemistry and charge, surface-charge mobility, and the dynamics of adsorbed polymer on fluidlike membranes. The model predictions are compared with experimental measurements of the electrophoretic mobility of stealth liposomes with molecular weights of terminally anchored poly(ethylene glycol) (PEG) in the range 0.35-10 kg mol(-1) [J.A. Cohen and V.A. Khorosheva, Colloids Surf. A 195, 113 (2001)]. The experimental data are interpreted by drawing upon self-consistent mean-field calculations of the polymer segment density distributions and numerically exact solutions of the governing transport equations [R.J. Hill, D.A. Saville, and W.B. Russel, J. Colloid Interface Sci. 258, 56 (2003)]. The approach leads to excellent agreement between theory and experiment with one adjustable parameter--the hydrodynamic size (Stokes radius) a(s) approximately equal to 0.175 A of the statistical PEG segments with (Kuhn) length l=7.1 A . The remarkably small Stokes radius is demonstrated to be consistent with other applications of the well-known Debye-Brinkman model and, consequently, this work reveals important limitations of the mean-field hydrodynamic model. Despite such limitations, the "full" electrokinetic model is robust in its predictive capacity. The molecular weights of the terminally anchored PEG span the range where the coatings undergo a transition from mushroomlike to brushlike conformations, and the hydrodynamic size and electrophoretic mobility of the liposomes are demonstrated to be sensitive to the PEG chain length and the effects of double-layer polarization.
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Affiliation(s)
- Reghan J Hill
- Department of Chemical Engineering, McGill University Montreal, Quebec, Canada H3A 2B2.
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39
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Riske KA, Döbereiner HG. Diacylglycerol-rich domain formation in giant stearoyl-oleoyl phosphatidylcholine vesicles driven by phospholipase C activity. Biophys J 2004; 85:2351-62. [PMID: 14507699 PMCID: PMC1303460 DOI: 10.1016/s0006-3495(03)74659-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We have studied the effect of phospholipase C from Bacillus cereus and Clostridium perfringens (alpha-toxin) on giant stearoyl-oleoyl phosphatidylcholine (SOPC) vesicles. Enzyme activity leads to a binary mixture of SOPC and the diacylglycerol SOG, which phase separates into a SOPC-rich bilayer phase and a SOG-rich isotropic bulk-like domain embedded within the membrane, as seen directly by phase contrast microscopy. After prolonged enzymatic attack, all bilayer membranes are transformed into an isotropic pure SOG phase as characterized by fluorescence microscopy, differential scanning calorimetry, fluorescence anisotropy measurements, and small angle x-ray scattering. These domains may have biological relevance, serving as storage compartments for hydrophobic molecules and/or catalyzing cellular signaling events at their boundaries. Furthermore, in the early stages of asymmetric enzymatic attack to the external monolayer of giant vesicles, we observe a transient coupling of the second-messenger diacylglycerol to membrane spontaneous curvature, which decreases due to enzyme activity, before domain formation and final vesicle collapse occurs.
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Affiliation(s)
- Karin A Riske
- Max-Planck-Institut für Kolloidund Grenzflächenforschung, 14476 Golm, Germany
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40
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Coakley WT, Bazou D, Morgan J, Foster GA, Archer CW, Powell K, Borthwick KAJ, Twomey C, Bishop J. Cell–cell contact and membrane spreading in an ultrasound trap. Colloids Surf B Biointerfaces 2004; 34:221-30. [PMID: 15261061 DOI: 10.1016/j.colsurfb.2004.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Revised: 11/05/2003] [Accepted: 01/12/2004] [Indexed: 11/28/2022]
Abstract
An ultrasonic standing wave trap [Langmuir 19 (2003) 3635] in which the morphologies of 2-D latex-microparticle aggregates, forming a pressure node plane, were characterised has been applied here to different cell suspensions with increasing order of specificity of cross-linking molecule, i.e. polylysine with chondrocytes; wheat germ agglutinin (WGA) with erythrocytes and surface receptors on neural cells. The outcome of initial cell-cell contact, i.e. whether the cells stuck at the point of contact (collision efficiency = 1) or rolled around each other (collision efficiency = 0), was monitored in situ by video-microscopy. The perimeter fractal dimensions (FD) of 2-D hexagonally symmetric, closely packed aggregates of control erythrocytes and chondrocytes were 1.16 and 1.18, respectively while those for the dendrititc aggregates formed initially by erythrocytes in 0.5microg/ml WGA and chondrocytes in 20 microg/ml polylysine were 1.49 and 1.66. The FDs for control and molecularly cross-linked cells were typical of reaction-limited aggregation (RLA) and transport diffusion-limited aggregation (DLA), respectively. The FDs of the aggregates of cross-linked cells decreased with time to give more closely packed aggregates without clear hexagonal symmetry. Suspensions of neural cells formed dendritic aggregates. Spreading of inter-cellular membrane contact area occurred over 15 min for both erythrocyte and neural cell dendritic aggregates. The potential of the technique to characterise and control the progression of cell adhesion in suspension away from solid substrata is discussed.
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Affiliation(s)
- W T Coakley
- School of Biosciences, Main Building, Cardiff University, Cardiff CF10 3TL, UK.
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41
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Lang MJ, Block SM. Resource Letter: LBOT-1: Laser-based optical tweezers. AMERICAN JOURNAL OF PHYSICS 2003; 71:201-215. [PMID: 16971965 PMCID: PMC1564163 DOI: 10.1119/1.1532323] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
This Resource Letter provides a guide to the literature on optical tweezers, also known as laser-based, gradient-force optical traps. Journal articles and books are cited for the following main topics: general papers on optical tweezers, trapping instrument design, optical detection methods, optical trapping theory, mechanical measurements, single molecule studies, and sections on biological motors, cellular measurements and additional applications of optical tweezers.
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Affiliation(s)
- Matthew J Lang
- Department of Biological Sciences and Department of Applied Physics, Stanford University, Stanford, California 94305-5020
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42
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McLaughlin S, Wang J, Gambhir A, Murray D. PIP(2) and proteins: interactions, organization, and information flow. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2002; 31:151-75. [PMID: 11988466 DOI: 10.1146/annurev.biophys.31.082901.134259] [Citation(s) in RCA: 690] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We review the physical properties of phosphatidylinositol 4,5-bisphosphate (PIP2) that determine both its specific interactions with protein domains of known structure and its nonspecific electrostatic sequestration by unstructured domains. Several investigators have postulated the existence of distinct pools of PIP2 within the cell to account for the myriad functions of this lipid. Recent experimental work indicates certain regions of the plasma membrane-membrane ruffles and nascent phagosomes-do indeed concentrate PIP2. We consider two mechanisms that could account for this phenomenon: local synthesis and electrostatic sequestration. We conclude by considering the hypothesis that proteins such as MARCKS bind a significant fraction of the PIP2 in a cell, helping to sequester it in lateral membrane domains, then release this lipid in response to local signals such as an increased concentration of Ca(++)/calmodulin or activation of protein kinase C.
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Affiliation(s)
- Stuart McLaughlin
- Department of Physiology and Biophysics, HSC, SUNY Stony Brook, NY 11794-8661, USA.
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