201
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Al-Obeidi A, Ge C, Orosz KS, Saavedra SS. ITO/poly(aniline)/sol-gel glass: An optically transparent, pH-responsive substrate for supported lipid bilayers. JOURNAL OF MATERIALS 2013; 2013:676920. [PMID: 25328882 PMCID: PMC4201389 DOI: 10.1155/2013/676920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4-9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 μm2/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation, and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels.
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Affiliation(s)
- Ahmed Al-Obeidi
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041
| | - Chenhao Ge
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041
| | - Kristina S. Orosz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041
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202
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Gericke A, Leslie NR, Lösche M, Ross AH. PtdIns(4,5)P2-mediated cell signaling: emerging principles and PTEN as a paradigm for regulatory mechanism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 991:85-104. [PMID: 23775692 DOI: 10.1007/978-94-007-6331-9_6] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PtdIns(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) is a relatively common anionic lipid that regulates cellular functions by multiple mechanisms. Hydrolysis of PtdIns(4,5)P2 by phospholipase C yields inositol trisphosphate and diacylglycerol. Phosphorylation by phosphoinositide 3-kinase yields PtdIns(3,4,5)P3, which is a potent signal for survival and proliferation. Also, PtdIns(4,5)P2 can bind directly to integral and peripheral membrane proteins. As an example of regulation by PtdIns(4,5)P2, we discuss phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in detail. PTEN is an important tumor suppressor and hydrolyzes PtdIns(3,4,5)P3. PtdIns(4,5)P2 enhances PTEN association with the plasma membrane and activates its phosphatase activity. This is a critical regulatory mechanism, but a detailed description of this process from a structural point of view is lacking. The disordered lipid bilayer environment hinders structural determinations of membrane-bound PTEN. A new method to analyze membrane-bound protein measures neutron reflectivity for proteins bound to tethered phospholipid membranes. These methods allow determination of the orientation and shape of membrane-bound proteins. In combination with molecular dynamics simulations, these studies will provide crucial structural information that can serve as a foundation for our understanding of PTEN regulation in normal and pathological processes.
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Affiliation(s)
- Arne Gericke
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
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203
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Das S, Donaldson Jr. SH, Kaufman Y, Israelachvili JN. Interaction of adsorbed polymers with supported cationic bilayers. RSC Adv 2013. [DOI: 10.1039/c3ra43500h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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204
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Gu LQ, Wanunu M, Wang MX, McReynolds L, Wang Y. Detection of miRNAs with a nanopore single-molecule counter. Expert Rev Mol Diagn 2012; 12:573-84. [PMID: 22845478 DOI: 10.1586/erm.12.58] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
miRNAs are short noncoding RNA molecules that are important in regulating gene expression. Due to the correlation of their expression levels and various diseases, miRNAs are being investigated as potential biomarkers for molecular diagnostics. The fast-growing miRNA exploration demands rapid, accurate, low-cost miRNA detection technologies. This article will focus on two platforms of nanopore single-molecule approach that can quantitatively measure miRNA levels in samples from tissue and cancer patient plasma. Both nanopore methods are sensitive and specific, and do not need labeling, enzymatic reaction or amplification. In the next 5 years, the nanopore-based miRNA techniques will be improved and validated for noninvasive and early diagnosis of diseases.
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Affiliation(s)
- Li-Qun Gu
- Biological Engineering and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA.
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205
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Jackman JA, Knoll W, Cho NJ. Biotechnology Applications of Tethered Lipid Bilayer Membranes. MATERIALS 2012. [PMCID: PMC5449075 DOI: 10.3390/ma5122637] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Joshua A. Jackman
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; E-Mail:
- Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore; E-Mail:
| | - Wolfgang Knoll
- Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore; E-Mail:
- Austrian Institute of Technology (AIT) GmbH, Donau-City Str.1, Vienna 1220, Austria
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; E-Mail:
- Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +65-6790-4925; Fax: +65-6790-9081
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206
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Patchornik G, Namboothiri IN, Nair DK, Wachtel E, Cohen SR, Friedman N, Sheves M. Engineered-membranes: A novel concept for clustering of native lipid bilayers. J Colloid Interface Sci 2012; 388:300-5. [DOI: 10.1016/j.jcis.2012.08.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Revised: 08/09/2012] [Accepted: 08/13/2012] [Indexed: 10/28/2022]
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207
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Robertson JWF, Kasianowicz JJ, Banerjee S. Analytical Approaches for Studying Transporters, Channels and Porins. Chem Rev 2012; 112:6227-49. [DOI: 10.1021/cr300317z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Joseph W. F. Robertson
- Physical Measurement Laboratory,
National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - John J. Kasianowicz
- Physical Measurement Laboratory,
National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Soojay Banerjee
- National
Institute of Neurological
Disorders and Stroke, Bethesda, Maryland 20824, United States
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208
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Liu C, Faller R. Conformational, dynamical. and tensional study of tethered bilayer lipid membranes in coarse-grained molecular simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15907-15915. [PMID: 23092246 DOI: 10.1021/la303511p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Tethered bilayer lipid membranes (tBLMs) have attracted great interest recently due to their crucial roles in elucidating fundamental membrane characteristics and the implications in biochemical sensors and pharmaceutical drug carriers. Nevertheless, they have not yet been investigated computationally on the molecular scale. Here, we study tBLMs consisting of DOPCs (1,2-dioleoyl-sn-glycero-3-phosphocholine) as free lipids and pegylated DOPCs (on phosphate group) as tethers in water by a variation of the MARTINI model. By varying grafting densities and tether lengths, distinct conformational changes from planar to undulated bilayers are observed. Lateral diffusivities and lateral pressure profiles show that the dynamical and tensional states are specific to the system configurations. These results suggest that the conformations, fluidity, and elasticity of the tBLMs can be tuned and manipulated to conform to various requirements in theoretical investigations and technological applications.
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Affiliation(s)
- Chueh Liu
- Department of Chemical Engineering and Materials Science, University of California-Davis, Davis, California 95616, United States
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209
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Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets.
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210
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Design of peptide-membrane interactions to modulate single-file water transport through modified gramicidin channels. Biophys J 2012; 103:1698-705. [PMID: 23083713 DOI: 10.1016/j.bpj.2012.08.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 08/22/2012] [Accepted: 08/23/2012] [Indexed: 11/22/2022] Open
Abstract
Water permeability through single-file channels is affected by intrinsic factors such as their size and polarity and by external determinants like their lipid environment in the membrane. Previous computational studies revealed that the obstruction of the channel by lipid headgroups can be long-lived, in the range of nanoseconds, and that pore-length-matching membrane mimetics could speed up water permeability. To test the hypothesis of lipid-channel interactions modulating channel permeability, we designed different gramicidin A derivatives with attached acyl chains. By combining extensive molecular-dynamics simulations and single-channel water permeation measurements, we show that by tuning lipid-channel interactions, these modifications reduce the presence of lipid headgroups in the pore, which leads to a clear and selective increase in their water permeability.
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211
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Membrane association of the PTEN tumor suppressor: electrostatic interaction with phosphatidylserine-containing bilayers and regulatory role of the C-terminal tail. J Struct Biol 2012; 180:394-408. [PMID: 23073177 DOI: 10.1016/j.jsb.2012.10.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 10/03/2012] [Accepted: 10/05/2012] [Indexed: 01/23/2023]
Abstract
The phosphatidylinositolphosphate phosphatase PTEN is the second most frequently mutated protein in human tumors. Its membrane association, allosteric activation and membrane dissociation are poorly understood. We recently reported PTEN binding affinities to membranes of different compositions (Shenoy et al., 2012, PLoS ONE 7, e32591) and a preliminary investigation of the protein-membrane complex with neutron reflectometry (NR). Here we use NR to validate molecular dynamics (MD) simulations of the protein and study conformational differences of the protein in solution and on anionic membranes. NR shows that full-length PTEN binds to such membranes roughly in the conformation and orientation suggested by the crystal structure of a truncated PTEN protein, in contrast with a recently presented model which suggested that membrane binding depends critically on the SUMOylation of the CBR3 loop of PTEN's C2 domain. Our MD simulations confirm that PTEN is peripherally bound to the bilayer surface and show slight differences of the protein structure in solution and in the membrane-bound state, where the protein body flattens against the bilayer surface. PTEN's C2 domain binds phosphatidylserine (PS) tightly through its CBR3 loop, and its phosphatase domain also forms electrostatic interactions with PS. NR and MD results show consistently that PTEN's unstructured, anionic C-terminal tail is repelled from the bilayer surface. In contrast, this tail is tightly tugged against the C2 domain in solution, partially obstructing the membrane-binding interface of the protein. Arresting the C-terminal tail in this conformation by phosphorylation may provide a control mechanism for PTEN's membrane binding and activity.
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212
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Abstract
Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10(-11) M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon nanotube pores embedded in a silicon-nitride or other membrane, fluorofullerene-Fragment antigen-binding (Fab fragment) conjugates, and polymer beads with complementary Fab fragments. We show by using molecular and stochastic dynamics that conduction through the (9, 9) exohydrogenated carbon nanotubes is 20 times larger than through the Ion Channel Switch ICS(TM) biosensor, and fluorofullerenes block the nanotube entrance with a dissociation constant as low as 37 pM. Under normal operating conditions and in the absence of analyte, fluorofullerenes block the nanotube pores and the polymer beads float around in the reservoir. When analyte is injected into the reservoir the Fab fragments attached to the fluorofullerene and polymer bead crosslink to the analyte. The drag of the much larger polymer bead then acts to pull the fluorofullerene from the nanotube entrance, thereby allowing the flow of monovalent cations across the membrane. Assuming a tight seal is formed between the two reservoirs, such a biosensor would be able to detect one channel opening and thus one molecule of analyte making it a highly sensitive detection design.
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Affiliation(s)
- Tamsyn A. Hilder
- Computational Biophysics Group, Research School of Biology, Australian National University, Acton, ACT 0200, Australia; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +61-2-6125-4034; Fax: +61-2-6125-0739
| | - Ron J. Pace
- Biophysical Chemistry, Research School of Chemistry, Australian National University, Acton, ACT 0200, Australia; E-Mail:
| | - Shin-Ho Chung
- Computational Biophysics Group, Research School of Biology, Australian National University, Acton, ACT 0200, Australia; E-Mail:
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213
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Nanopore sensors: From hybrid to abiotic systems. Biosens Bioelectron 2012; 38:1-10. [DOI: 10.1016/j.bios.2012.05.013] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 05/02/2012] [Accepted: 05/12/2012] [Indexed: 11/22/2022]
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214
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On physical properties of tetraether lipid membranes: effects of cyclopentane rings. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2012; 2012:138439. [PMID: 23028246 PMCID: PMC3458407 DOI: 10.1155/2012/138439] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 08/08/2012] [Indexed: 01/25/2023]
Abstract
This paper reviews the recent findings related to the physical properties of tetraether lipid membranes, with special attention to the effects of the number, position, and configuration of cyclopentane rings on membrane properties. We discuss the findings obtained from liposomes and monolayers, composed of naturally occurring archaeal tetraether lipids and synthetic tetraethers as well as the results from computer simulations. It appears that the number, position, and stereochemistry of cyclopentane rings in the dibiphytanyl chains of tetraether lipids have significant influence on packing tightness, lipid conformation, membrane thickness and organization, and headgroup hydration/orientation.
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215
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Afanasenkau D, Offenhäusser A. Positively charged supported lipid bilayers as a biomimetic platform for neuronal cell culture. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:13387-13394. [PMID: 22920161 DOI: 10.1021/la302500r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The supported lipid bilayer (SLB) is a well-known system for studying the cell membrane and membrane proteins. It is also promising as a platform for studying cell processes: the cell adhesion, the cell membrane receptors, and the intercellular signaling processes. SLBs made of natural lipids appeared to be protein and cell repellent. Thus, to use the SLB as a substrate for cells, one should functionalize them to provide adhesion. In the present paper, we describe a simple approach to promote adhesion of neuronal cells to the SLB without using proteins or peptides, by introducing positively charged lipids 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) into the SLB made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). We show that neurons adhere to these bilayers and grow for at least 10 days. The SLBs themselves were found to degrade with time in cell culture conditions, but maintained fluidity (as revealed by fluorescence recovery after photobleaching), demonstrating the possibility of using SLBs for studying neuronal cells in culture.
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Affiliation(s)
- Dzmitry Afanasenkau
- Peter Grünberg Institute/Institute of Complex Systems Bioelectronics (PGI-8/ICS-8), Research Center Juelich, D-52425 Juelich, Germany
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216
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Synthesis of symmetrical, single-chain, phenylene/biphenylene-modified bolaamphiphiles. MONATSHEFTE FUR CHEMIE 2012. [DOI: 10.1007/s00706-012-0833-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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217
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Meissner R, Joris P, Eker B, Bertsch A, Renaud P. A microfluidic-based frequency-multiplexing impedance sensor (FMIS). LAB ON A CHIP 2012; 12:2712-2718. [PMID: 22627460 DOI: 10.1039/c2lc40236j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present a novel technology for the simultaneous and simple impedimetric screening of multiple microfluidic channels with only one electrode pair. We have exploited the frequency dimension to distinguish between up to three channels. Each 'sub-sensor' possesses its corresponding measurement frequency where the sample-specific dielectric properties can be probed. We have shown the validity of our frequency-multiplexing impedance sensor (FMIS) by comparison with conventional 'single sensors'. Our highly sensitive FMIS was proven suitable for life science applications through usage as a cell-based toxicology platform. We are confident that our technology might find great utility in parallelized cell-based analysis systems as well as in biomedical devices where size limitations and spatially distributed probing are important parameters.
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Affiliation(s)
- Robert Meissner
- Laboratoire de Microsystèmes LMIS4, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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218
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Kim YR, Jung S, Ryu H, Yoo YE, Kim SM, Jeon TJ. Synthetic biomimetic membranes and their sensor applications. SENSORS (BASEL, SWITZERLAND) 2012; 12:9530-50. [PMID: 23012557 PMCID: PMC3444115 DOI: 10.3390/s120709530] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 06/05/2012] [Accepted: 06/16/2012] [Indexed: 11/16/2022]
Abstract
Synthetic biomimetic membranes provide biological environments to membrane proteins. By exploiting the central roles of biological membranes, it is possible to devise biosensors, drug delivery systems, and nanocontainers using a biomimetic membrane system integrated with functional proteins. Biomimetic membranes can be created with synthetic lipids or block copolymers. These amphiphilic lipids and polymers self-assemble in an aqueous solution either into planar membranes or into vesicles. Using various techniques developed to date, both planar membranes and vesicles can provide versatile and robust platforms for a number of applications. In particular, biomimetic membranes with modified lipids or functional proteins are promising platforms for biosensors. We review recent technologies used to create synthetic biomimetic membranes and their engineered sensors applications.
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Affiliation(s)
- Young-Rok Kim
- Institute of Life Sciences and Resources & Department of Food Science and Biotechnology, Kyung Hee University, Yongin 446-701, Korea; E-Mail:
| | - Sungho Jung
- Department of Biological Engineering, Inha University, Incheon 402-751, Korea; E-Mails: (S.J.); (H.R.)
| | - Hyunil Ryu
- Department of Biological Engineering, Inha University, Incheon 402-751, Korea; E-Mails: (S.J.); (H.R.)
| | - Yeong-Eun Yoo
- Nano-Mechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343, Korea; E-Mail:
| | - Sun Min Kim
- Department of Mechanical Engineering, Inha University, Incheon 402-751, Korea; E-Mail:
- Biohybrid Systems Research Center, Inha University, Incheon 402-751, Korea
| | - Tae-Joon Jeon
- Department of Biological Engineering, Inha University, Incheon 402-751, Korea; E-Mails: (S.J.); (H.R.)
- Biohybrid Systems Research Center, Inha University, Incheon 402-751, Korea
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219
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Amphotericin B ion channel mimetic sensor: A new type of potassium-selective sensor based on electrode-supported hybrid bilayer membranes. Electrochim Acta 2012. [DOI: 10.1016/j.electacta.2012.03.096] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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220
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Petrov E, Rohde PR, Cornell B, Martinac B. The protective effect of osmoprotectant TMAO on bacterial mechanosensitive channels of small conductance MscS/MscK under high hydrostatic pressure. Channels (Austin) 2012; 6:262-71. [PMID: 22790324 PMCID: PMC3508905 DOI: 10.4161/chan.20833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Activity of the bacterial mechanosensitive channels of small conductance MscS/MscK of E. coli was investigated under high hydrostatic pressure (HHP) using the "flying-patch" patch-clamp technique. The channels were gated by negative pipette voltage and their open probability was measured at HHP of 0.1 to 80 MPa. The channel open probability decreased with increasing HHP. When the osmolyte methylamine N-oxide (TMAO) was applied to the cytoplasmic side of the inside-out excised membrane patches of E. coli giant spheroplasts the inhibitory effect of HHP on the channel activity was suppressed at pressures of up to 40 MPa. At 40 MPa and above the channel open probability decreased in a similar fashion with or without TMAO. Our study suggests that TMAO helps to counteract the effect of HHP up to 40 MPa on the MscS/MscK open state by "shielding" the cytoplasmic domain of the channels.
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Affiliation(s)
- Evgeny Petrov
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
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221
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Stava E, Siyoung Choi, Hyun-Seok Kim, Blick RH. On-Chip Stochastic Resonance of Ion Channel Systems With Variable Internal Noise. IEEE Trans Nanobioscience 2012; 11:169-75. [DOI: 10.1109/tnb.2012.2188539] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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222
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Fusion of single proteoliposomes with planar, cushioned bilayers in microfluidic flow cells. Nat Protoc 2012; 7:903-20. [PMID: 22517259 DOI: 10.1038/nprot.2012.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Many biological processes rely on membrane fusion, and therefore assays to study its mechanisms are necessary. Here we report an assay with sensitivity to single-vesicle, and even to single-molecule events using fluorescently labeled vesicle-associated v-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) liposomes and target-membrane-associated t-SNARE-reconstituted planar, supported bilayers (t-SBLs). Docking and fusion events can be detected using conventional far-field epifluorescence or total internal reflection fluorescence microscopy. In this assay, fusion is dependent on SNAP-25, one of the t-SNARE subunits that is required for fusion in vivo. The success of the assay is due to the use of: (i) bilayers covered with a thin layer of poly(ethylene glycol) (PEG) to control bilayer-bilayer and bilayer-substrate interactions, and (ii) microfluidic flow channels that present many advantages, such as the removal of nonspecifically bound liposomes by flow. The protocol takes 6-8 d to complete. Analysis can take up to 2 weeks.
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223
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Shenoy S, Shekhar P, Heinrich F, Daou MC, Gericke A, Ross AH, Lösche M. Membrane association of the PTEN tumor suppressor: molecular details of the protein-membrane complex from SPR binding studies and neutron reflection. PLoS One 2012; 7:e32591. [PMID: 22505997 PMCID: PMC3323581 DOI: 10.1371/journal.pone.0032591] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 01/29/2012] [Indexed: 12/03/2022] Open
Abstract
The structure and function of the PTEN phosphatase is investigated by studying its membrane affinity and localization on in-plane fluid, thermally disordered synthetic membrane models. The membrane association of the protein depends strongly on membrane composition, where phosphatidylserine (PS) and phosphatidylinositol diphosphate (PI(4,5)P2) act pronouncedly synergistic in pulling the enzyme to the membrane surface. The equilibrium dissociation constants for the binding of wild type (wt) PTEN to PS and PI(4,5)P2 were determined to be Kd∼12 µM and 0.4 µM, respectively, and Kd∼50 nM if both lipids are present. Membrane affinities depend critically on membrane fluidity, which suggests multiple binding sites on the protein for PI(4,5)P2. The PTEN mutations C124S and H93R show binding affinities that deviate strongly from those measured for the wt protein. Both mutants bind PS more strongly than wt PTEN. While C124S PTEN has at least the same affinity to PI(4,5)P2 and an increased apparent affinity to PI(3,4,5)P3, due to its lack of catalytic activity, H93R PTEN shows a decreased affinity to PI(4,5)P2 and no synergy in its binding with PS and PI(4,5)P2. Neutron reflection measurements show that the PTEN phosphatase “scoots" along the membrane surface (penetration <5 Å) but binds the membrane tightly with its two major domains, the C2 and phosphatase domains, as suggested by the crystal structure. The regulatory C-terminal tail is most likely displaced from the membrane and organized on the far side of the protein, ∼60 Å away from the bilayer surface, in a rather compact structure. The combination of binding studies and neutron reflection allows us to distinguish between PTEN mutant proteins and ultimately may identify the structural features required for membrane binding and activation of PTEN.
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Affiliation(s)
- Siddharth Shenoy
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Prabhanshu Shekhar
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Frank Heinrich
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States of America
| | - Marie-Claire Daou
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Arne Gericke
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, United States of America
| | - Alonzo H. Ross
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Mathias Lösche
- Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States of America
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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224
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A molecular machine biosensor: Construction, predictive models and experimental studies. Biosens Bioelectron 2012; 34:261-6. [DOI: 10.1016/j.bios.2012.02.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/03/2012] [Accepted: 02/10/2012] [Indexed: 11/20/2022]
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225
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Yang LM, Wray R, Parker J, Wilson D, Duran RS, Blount P. Three routes to modulate the pore size of the MscL channel/nanovalve. ACS NANO 2012; 6:1134-1141. [PMID: 22206349 PMCID: PMC3289768 DOI: 10.1021/nn203703j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
MscL is a bacterial mechanosensitive channel that protects cells from lysis upon acute decrease in external osmotic environment. It is one of the best characterized mechanosensors known, thus serving as a paradigm of how such molecules sense and respond to stimuli. In addition, the fact that it can be genetically modified, expressed, isolated, and manipulated has led to its proposed use as a triggered nanovalve for various functions including sensors within microelectronic array chips, as well as vesicular-based targeted drug release. X-ray crystallography reveals a homopentameric complex with each subunit containing two transmembrane α-helices (TM1 and TM2) and a single carboxyl terminal α-helix arranging within the complex to form a 5-fold cytoplasmic bundle (CB), whose function and stability remain unclear. In this study, we show three routes that throttle the open channel conductance. When the linker between the TM2 and CB domain is shortened by deletions or constrained by either cross-linking or heavy metal coordination, the conductance of the channel is reduced; in the later two cases, even reversibly. While they have implications for the stability of the CB, these data also provide routes for engineering MscL sensors that are more versatile for potential nanotech devices.
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Affiliation(s)
- Li-Min Yang
- Department of Physiology, University of Texas Medical Center at Dallas, Dallas, Texas, USA
| | - Robin Wray
- Department of Physiology, University of Texas Medical Center at Dallas, Dallas, Texas, USA
| | - Juandell Parker
- Department of Physiology, University of Texas Medical Center at Dallas, Dallas, Texas, USA
| | - Danyell Wilson
- Department of Chemistry, University of Florida, current address Moffitt Cancer Center, Tampa, FL
| | - Randolph S. Duran
- Department of Chemistry, Louisiana State University, Baton Rouge, LA
| | - Paul Blount
- Department of Physiology, University of Texas Medical Center at Dallas, Dallas, Texas, USA
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226
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Krishnamurthy V, Cornell B. Engineering aspects of biological ion channels--from biosensors to computational models for permeation. PROTOPLASMA 2012; 249 Suppl 1:S3-S9. [PMID: 22038117 DOI: 10.1007/s00709-011-0333-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/04/2011] [Indexed: 05/31/2023]
Abstract
This paper presents two important engineering aspects of biological ion channels-how to build sensors out of gramicidin channels and how to construct computational models for ion channel permeation. We describe our recent research in these areas, potential challenges and possible solutions.
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Affiliation(s)
- Vikram Krishnamurthy
- Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, V6T 1Z4, Canada.
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227
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Valincius G, Meškauskas T, Ivanauskas F. Electrochemical impedance spectroscopy of tethered bilayer membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:977-90. [PMID: 22126190 DOI: 10.1021/la204054g] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The electrochemical impedance spectra (EIS) of tethered bilayer membranes (tBLMs) were analyzed, and the analytical solution for the spectral response of membranes containing natural or artificially introduced defects was derived. The analysis carried out in this work shows that the EIS features of an individual membrane defect cannot be modeled by conventional electrical elements. The primary reason for this is the complex nature of impedance of the submembrane ionic reservoir separating the phospholipid layer and the solid support. We demonstrate that its EIS response, in the case of radially symmetric defects, is described by the Hankel functions of a complex variable. Therefore, neither the impedance of the submembrane reservoir nor the total impedance of tBLMs can be modeled using the conventional elements of the equivalent electrical circuits of interfaces. There are, however, some limiting cases in which the complexity of the EIS response of the submembrane space reduces. In the high frequency limit, the EIS response of a submembrane space that surrounds the defect transforms into a response of a constant phase element (CPE) with the exponent (α) value of 0.5. The onset of this transformation is, beside other parameters, dependent on the defect size. Large-sized defects push the frequency limit lower, therefore, the EIS spectra exhibiting CPE behavior with α ≈ 0.5, can serve as a diagnostic criterion for the presence of such defects. In the low frequency limit, the response is dependent on the density of the defects, and it transforms into the capacitive impedance if the area occupied by a defect is finite. The higher the defect density, the higher the frequency edge at which the onset of the capacitive behavior is observed. Consequently, the presented analysis provides practical tools to evaluate the defect density in tBLMs, which could be utilized in tBLM-based biosensor applications. Alternatively, if the parameters of the defects, e.g., ion channels, such as the diameter and the conductance are known, the EIS data analysis provides a possibility to estimate other physical parameters of the system, such as thickness of the submembrane reservoir and its conductance. Finally, current analysis demonstrates a possibility to discriminate between the situations, in which the membrane defects are evenly distributed or clustered on the surface of tBLMs. Such sensitivity of EIS could be used for elucidation of the mechanisms of interaction between the proteins and the membranes.
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Affiliation(s)
- Gintaras Valincius
- Vilnius University Institute of Biochemistry, Mokslininku 12, LT-08662 Vilnius, Lithuania.
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228
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Qin LX, Li Y, Li DW, Jing C, Chen BQ, Ma W, Heyman A, Shoseyov O, Willner I, Tian H, Long YT. Electrodeposition of Single-Metal Nanoparticles on Stable Protein 1 Membranes: Application of Plasmonic Sensing by Single Nanoparticles. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201106482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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229
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Zan GH, Tan C, Deserno M, Lanni F, Lösche M. Hemifusion of giant unilamellar vesicles with planar hydrophobic surfaces: a fluorescence microscopy study. SOFT MATTER 2012; 8:10877-10886. [PMID: 25383087 PMCID: PMC4222682 DOI: 10.1039/c2sm25702e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Vesicle adhesion and fusion to interfaces are frequently used for the construction of biomimetic surfaces in biosensors and drug delivery. Ubiquitous in cell biology, vesicle fusion involves the transformation of two separate membranes into one contiguous lipid bilayer. In distinction, the deposition of vesicle membranes to hydrophobic surfaces requires the transformation of a lipidic bilayer into a monomolecular layer - a topologically distinct process termed hemifusion. Here, we used hydrophobically terminated self-assembled monolayers (SAMs) on solid surfaces to track the hemifusion of fluorescently labeled giant unilamellar vesicles (GUVs) at the single vesicle level with video time resolution (≈53 ms). We observed that a dilute monolayer, consisting of lipid extracted from the outer GUV leaflet, spreads outward across the hydrophobic surface from the vesicle adhesion site. Subsequently, bilayer hemifusion occurs by vesicle rupture near the hydrophobic surface, followed by spreading of lipid in a dense monolayer. GUV lipids thus transfer to the SAM surface in two concentric zones: an outer hemifusion zone comprises lipids drawn from the outer GUV leaflet and an inner hemifusion zone comprises lipids from both the inner and outer GUV leaflets and grows at a rate of ≈1000 µm2 s-1 (dA/dt = 970 ± 430 µm2 s-1 in n = 22 independent experiments). This growth rate is quantitatively consistent with the assumption that the spreading of the monolayer is entirely driven by the difference in surface energies of the hydrophobic and the lipid-covered SAM surfaces, which is dissipated by friction of the spreading monolayer on the SAM. Lipid transfer between the inner and outer GUV leaflets occurs via a hemifusion pore that forms early in the process near the membrane contact site. This pore also permits expulsion of water from the GUV interior as the vesicle contracts onto the contact site.
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Affiliation(s)
- Goh Haw Zan
- Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
| | - Cheemeng Tan
- Ray and Stephanie Lane Center for Computational Biology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
| | - Frederick Lanni
- Department of Biological Sciences, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890, USA
- National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, MD 20899-6102, USA
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230
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Meister A, Blume A. Single-Chain Bolaphospholipids. ADVANCES IN PLANAR LIPID BILAYERS AND LIPOSOMES VOLUME 16 2012. [DOI: 10.1016/b978-0-12-396534-9.00004-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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231
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Ma Y, Jiang R, Zhang H, Gruzdys V, Sun XL. Chemoselectively surface funtionalizable tethered bilayer lipid membrane for versatile membrane mimetic systems fabrication. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm15858b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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232
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Drescher S, Becker S, Dobner B, Blume A. Bis-Sonogashira cross-coupling: an expeditious approach towards long-chain, phenylene-modified 1,ω-diols. RSC Adv 2012. [DOI: 10.1039/c2ra20411h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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233
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NISHIO M, SHOJI A, SUGAWARA M. Planar Lipid Bilayers Containing Gramicidin A as a Molecular Sensing System Based on an Integrated Current. ANAL SCI 2012; 28:661-7. [DOI: 10.2116/analsci.28.661] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Masato NISHIO
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Atsushi SHOJI
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Masao SUGAWARA
- Department of Chemistry, College of Humanities and Sciences, Nihon University
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234
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Basit H, Van der Heyden A, Gondran C, Nysten B, Dumy P, Labbé P. Tethered bilayer lipid membranes on mixed self-assembled monolayers of a novel anchoring thiol: impact of the anchoring thiol density on bilayer formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14317-14328. [PMID: 21962085 DOI: 10.1021/la202847r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Tethered bilayer lipid membranes (tBLMs) are designed on mixed self-assembled monolayers (SAMs) of a novel synthetic anchoring thiol, 2,3-di-o-palmitoylglycerol-1-tetraethylene glycol mercaptopropanoic acid ester (TEG-DP), and a new short dilution thiol molecule, tetraethylene glycol mercaptopropanoic acid ester (TEG). tBLM formation was accomplished by self-directed fusion of small unilamellar vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. The influence of the dilution of the anchoring thiol molecule in the SAM on the vesicle fusion process and on the properties of the resulting tBLMs is studied. It is observed by quartz crystal microbalance that vesicle fusion is a one-step process for a pure TEG-DP SAM as well as for mixed SAMs containing a high concentration of the anchoring thiol. However, upon dilution of the anchoring thiol to moderate concentrations, this process is decelerated and possibly follows a pathway different from that observed on a pure TEG-DP SAM. Electrochemical impedance spectroscopy is used to qualitatively correlate the composition of the SAM to the electrical properties of the tBLM. In this paper we also delineate the necessity of a critical concentration of this anchoring TEG-DP thiol as a requisite for inducing the fusion of vesicles to form a tBLM.
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Affiliation(s)
- Hajra Basit
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France.
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235
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Gooding JJ, Darwish N. The rise of self-assembled monolayers for fabricating electrochemical biosensors-an interfacial perspective. CHEM REC 2011; 12:92-105. [DOI: 10.1002/tcr.201100013] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Indexed: 11/08/2022]
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236
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Qin LX, Li Y, Li DW, Jing C, Chen BQ, Ma W, Heyman A, Shoseyov O, Willner I, Tian H, Long YT. Electrodeposition of Single-Metal Nanoparticles on Stable Protein 1 Membranes: Application of Plasmonic Sensing by Single Nanoparticles. Angew Chem Int Ed Engl 2011; 51:140-4. [DOI: 10.1002/anie.201106482] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 10/31/2011] [Indexed: 11/09/2022]
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237
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Steller L, Kreir M, Salzer R. Natural and artificial ion channels for biosensing platforms. Anal Bioanal Chem 2011; 402:209-30. [PMID: 22080413 DOI: 10.1007/s00216-011-5517-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 10/14/2011] [Accepted: 10/18/2011] [Indexed: 10/15/2022]
Abstract
The single-molecule selectivity and specificity of the binding process together with the expected intrinsic gain factor obtained when utilizing flow through a channel have attracted the attention of analytical chemists for two decades. Sensitive and selective ion channel biosensors for high-throughput screening are having an increasing impact on modern medical care, drug screening, environmental monitoring, food safety, and biowarefare control. Even virus antigens can be detected by ion channel biosensors. The study of ion channels and other transmembrane proteins is expected to lead to the development of new medications and therapies for a wide range of illnesses. From the first attempts to use membrane proteins as the receptive part of a sensor, ion channels have been engineered as chemical sensors. Several other types of peptidic or nonpeptidic channels have been investigated. Various gating mechanisms have been implemented in their pores. Three technical problems had to be solved to achieve practical biosensors based on ion channels: the fabrication of stable lipid bilayer membranes, the incorporation of a receptor into such a structure, and the marriage of the modified membrane to a transducer. The current status of these three areas of research, together with typical applications of ion-channel biosensors, are discussed in this review.
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Affiliation(s)
- L Steller
- Department of Magnetic and Acoustic Resonances, Leibniz Institute for Solid State and Materials Research, Dresden, Germany.
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238
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Folliet N, Roiland C, Bégu S, Aubert A, Mineva T, Goursot A, Selvaraj K, Duma L, Tielens F, Mauri F, Laurent G, Bonhomme C, Gervais C, Babonneau F, Azaïs T. Investigation of the interface in silica-encapsulated liposomes by combining solid state NMR and first principles calculations. J Am Chem Soc 2011; 133:16815-27. [PMID: 21899369 DOI: 10.1021/ja201002r] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the context of nanomedicine, liposils (liposomes and silica) have a strong potential for drug storage and release schemes: such materials combine the intrinsic properties of liposome (encapsulation) and silica (increased rigidity, protective coating, pH degradability). In this work, an original approach combining solid state NMR, molecular dynamics, first principles geometry optimization, and NMR parameters calculation allows the building of a precise representation of the organic/inorganic interface in liposils. {(1)H-(29)Si}(1)H and {(1)H-(31)P}(1)H Double Cross-Polarization (CP) MAS NMR experiments were implemented in order to explore the proton chemical environments around the silica and the phospholipids, respectively. Using VASP (Vienna Ab Initio Simulation Package), DFT calculations including molecular dynamics, and geometry optimization lead to the determination of energetically favorable configurations of a DPPC (dipalmitoylphosphatidylcholine) headgroup adsorbed onto a hydroxylated silica surface that corresponds to a realistic model of an amorphous silica slab. These data combined with first principles NMR parameters calculations by GIPAW (Gauge Included Projected Augmented Wave) show that the phosphate moieties are not directly interacting with silanols. The stabilization of the interface is achieved through the presence of water molecules located in-between the head groups of the phospholipids and the silica surface forming an interfacial H-bonded water layer. A detailed study of the (31)P chemical shift anisotropy (CSA) parameters allows us to interpret the local dynamics of DPPC in liposils. Finally, the VASP/solid state NMR/GIPAW combined approach can be extended to a large variety of organic-inorganic hybrid interfaces.
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Affiliation(s)
- Nicolas Folliet
- UPMC Univ Paris 06 & CNRS, UMR 7574, Chimie de la Matière Condensée de Paris, Collège de France, 11, place Marcelin Berthelot, F-75005, Paris, France
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239
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Strulson MK, Maurer JA. Microcontact printing for creation of patterned lipid bilayers on tetraethylene glycol self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:12052-12057. [PMID: 21866896 PMCID: PMC3188422 DOI: 10.1021/la201839w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Supported lipid bilayers (SLBs) formed on many different substrates have been widely used in the study of lipid bilayers. However, most SLBs suffer from inhomogeneities due to interactions between the lipid bilayer and the substrate. In order to avoid this problem, we have used microcontact printing to create patterned SLBs on top of ethylene-glycol-terminated self-assembled monolayers (SAMs). Glycol-terminated SAMs have previously been shown to resist absorbance of biomolecules including lipid vesicles. In our system, patterned lipid bilayer regions are separated by lipid monolayers, which form over the patterned hexadecanethiol portions of the surface. Furthermore, we demonstrate that α-hemolysin, a large transmembrane protein, inserts preferentially into the lipid bilayer regions of the substrate.
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240
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Lundgren A, Hedlund J, Andersson O, Brändén M, Kunze A, Elwing H, Höök F. Resonance-Mode Electrochemical Impedance Measurements of Silicon Dioxide Supported Lipid Bilayer Formation and Ion Channel Mediated Charge Transport. Anal Chem 2011; 83:7800-6. [DOI: 10.1021/ac201273t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Anders Lundgren
- Department of Cell and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Julia Hedlund
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
| | - Olof Andersson
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
| | - Magnus Brändén
- Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Angelika Kunze
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Hans Elwing
- Department of Cell and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Fredrik Höök
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
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241
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Jung SH, Choi S, Kim YR, Jeon TJ. Storable droplet interface lipid bilayers for cell-free ion channel studies. Bioprocess Biosyst Eng 2011; 35:241-6. [PMID: 21909672 DOI: 10.1007/s00449-011-0602-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 07/16/2011] [Indexed: 11/24/2022]
Abstract
An artificially created lipid bilayer is an important platform in studying ion channels and engineered biosensor applications. However, a lipid bilayer created using conventional techniques is fragile and short-lived, and the measurement of ion channels requires expertise and laborious procedures, precluding practical applications. Here, we demonstrate a storable droplet lipid bilayer precursor frozen with ion channels, resulting in a droplet interface bilayer upon thawing. A small vial with an aqueous droplet in organic solution was flash frozen in -80 °C methanol immediately after an aqueous droplet was introduced into the organic solution and gravity draws the droplet down to the interface upon thawing. A lipid bilayer created along the interface using this method had giga-ohm resistance and typical specific capacitance values. The noise level of this system is favorably comparable to the conventional system. The subsequent incorporation of ion channels, alpha-hemolysin and gramicidin A, showed typical conductance values consistent with those in previous literatures. This novel system to create a lipid bilayer as a whole can be automated from its manufacture to use and indefinitely stored when frozen. As a result, ion channel measurements can be carried out in any place, increasing the accessibility of ion channel studies as well as a number of applications, such as biosensors, ion channel drug screening, and biophysical studies.
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Affiliation(s)
- Sung-Ho Jung
- Department of Biological Engineering, Inha University, Incheon, Korea
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242
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Prangkio P, Rao DK, Lance KD, Rubinshtein M, Yang J, Mayer M. Self-assembled, cation-selective ion channels from an oligo(ethylene glycol) derivative of benzothiazole aniline. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2877-85. [PMID: 21889925 DOI: 10.1016/j.bbamem.2011.08.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 07/22/2011] [Accepted: 08/18/2011] [Indexed: 01/01/2023]
Abstract
This paper describes the spontaneous formation of well-defined pores in planar lipid bilayers from the self-assembly of a small synthetic molecule that contains a benzothiazole aniline (BTA) group attached to a tetra-ethylene glycol (EG4) moiety. Macroscopic and single-channel current recordings suggest that these pores are formed by the assembly of four BTA-EG4 monomers with an open pore diameter that appears similar to the one of gramicidin pores (~0.4 nm). The single-channel conductance of these pores is modulated by the pH of the electrolyte and has a minimum at pH~3. Self-assembled pores from BTA-EG4 are selective for monovalent cations and have long open channel lifetimes on the order of seconds. BTA-EG4 monomers in these pores appear to be arranged symmetrically across both leaflets of the bilayer, and spectroscopy studies suggest that the fluorescent BTA group is localized inside the lipid bilayers. In terms of biological activity, BTA-EG4 molecules inhibited growth of gram-positive Bacillus subtilis bacteria (IC50~50 μM) and human neuroblastoma SH-SY5Y cells (IC50~60 μM), while they were not toxic to gram-negative Escherichia coli bacteria at a concentration up to 500 μM. Based on these properties, this drug-like, synthetic, pore-forming molecule with a molecular weight below 500 g mol(-1) might be appealing as a starting material for development of antibiotics or membrane-permeating moieties for drug delivery. From a biophysical point of view, long-lived, well-defined ion-selective pores from BTA-EG4 molecules offer an example of a self-assembled synthetic supramolecule with biological function.
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Affiliation(s)
- Panchika Prangkio
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, Michigan 48109-2110, USA
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243
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Markowski T, Drescher S, Meister A, Hause G, Blume A, Dobner B. Synthesis of Optically Pure Diglycerol Tetraether Model Lipids with Non-Natural Branching Pattern. European J Org Chem 2011. [DOI: 10.1002/ejoc.201100758] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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244
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Laredo T, Dutcher JR, Lipkowski J. Electric field driven changes of a gramicidin containing lipid bilayer supported on a Au(111) surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10072-10087. [PMID: 21707110 DOI: 10.1021/la201625c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Langmuir-Blodgett and Langmuir-Schaeffer methods were employed to deposit a mixed bilayer consisting of 90% of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 10% of gramicidin (GD), a short 15 residue ion channel forming peptide, onto a Au(111) electrode surface. This architecture allowed us to investigate the effect of the electrostatic potential applied to the electrode on the orientation and conformation of DMPC molecules in the bilayer containing the ion channel. The charge density data were determined from chronocoulometry experiments. The electric field and the potential across the membrane were determined through the use of charge density curves. The magnitudes of potentials across the gold-supported biomimetic membrane were comparable to the transmembrane potential acting on a natural membrane. The information regarding the orientation and conformation of DMPC and GD molecules in the bilayer was obtained from photon polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) measurements. The results show that the bilayer is adsorbed, in direct contact with the metal surface, when the potential across the interface is more positive than -0.4 V and is lifted from the gold surface when the potential across the interface is more negative than -0.4 V. This change in the state of the bilayer has a significant impact on the orientation and conformation of the phospholipid and gramicidin molecules. The potential induced changes in the membrane containing peptide were compared to the changes in the structure of the pure DMPC bilayer determined in earlier studies.
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Affiliation(s)
- Thamara Laredo
- Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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245
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Potential analytical applications of lysenin channels for detection of multivalent ions. Anal Bioanal Chem 2011; 401:1871-9. [PMID: 21818682 DOI: 10.1007/s00216-011-5277-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 07/13/2011] [Accepted: 07/21/2011] [Indexed: 11/27/2022]
Abstract
Transmembrane protein transporters possessing binding sites for ions, toxins, pharmaceutical drugs, and other molecules constitute excellent candidates for developing sensitive and selective biosensing devices. Their attractiveness for analytical purposes is enhanced by the intrinsic amplification capabilities shown when the binding event leads to major changes in the transportation of ions or molecules other than the analyte itself. The large-scale implementation of such transmembrane proteins in biosensing devices is limited by the difficulties encountered in inserting functional transporters into artificial bilayer lipid membranes and by the limitations in understanding and exploiting the changes induced by the interaction with the analyte for sensing purposes. Here, we show that lysenin, a pore-forming toxin extracted from earthworm Eisenia foetida, which inserts stable and large conductance channels into artificial bilayer lipid membranes, functions as a multivalent ion-sensing device. The analytical response consists of concentration and ionic-species-dependent macroscopic conductance inhibition most probably linked to a ligand-induced gating mechanism. Multivalent ion removal by chelation or precipitation restores, in most cases, the initial conductance and demonstrates reversibility. Changes in lipid bilayer membrane compositions leading to the absence of voltage-induced gating do not affect the analytical response to multivalent ions. Microscopic current analysis performed on individual lysenin channels in the presence of Cu(2+) revealed complex open-closed transitions characterized by unstable intermediate sub-conducting states. Lysenin channels provide an analytical tool with a built-in sensing mechanism for inorganic and organic multivalent ions, and the excellent stability in an artificial environment recommend lysenin as a potential candidate for single-molecule detection and analysis.
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246
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Xiao X, Montaño GA, Allen A, Achyuthan KE, Wheeler DR, Brozik SM. Lipid bilayer templated gold nanoparticles nanoring formation using zirconium ion coordination chemistry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:9484-9489. [PMID: 21699157 DOI: 10.1021/la2014754] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We used positively charged lipids to prepare lipid bilayer assemblies (LBAs) upon which we assembled negatively charged gold nanoparticles (AuNPs). Treatment of the assembly with zirconium chloride resulted in the formation of nanorings of the diameters inversely related to the zirconium ion concentration. The nanorings were attributed to the zirconium ion coordinated AuNPs formed during the lipid bilayer budding process promoted by the acid effect of zirconium chloride. Nanoring organization was also dependent on the fluidity of lipid bilayers, an indication of LBA-assisted nanomaterials organization. We suggest that such bioorganic-inorganic hybrid assemblies coupled to unique topological and morphological variations might be useful as stimuli-responsive sensors or storage compartments for proteins or drugs.
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Affiliation(s)
- Xiaoyin Xiao
- Biosensors and Nanomaterials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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247
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Macrae MX, Schlamadinger D, Kim JE, Mayer M, Yang J. Using charge to control the functional properties of self-assembled nanopores in membranes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2011; 7:2016-2020. [PMID: 21626687 DOI: 10.1002/smll.201100394] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Indexed: 05/30/2023]
Affiliation(s)
- Michael X Macrae
- University of California-San Diego, Department of Chemistry and Biochemistry, La Jolla, CA 92093-0358, USA
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248
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Niu Y, Jin G. Protein microarray biosensors based on imaging ellipsometry techniques and their applications. Protein Cell 2011; 2:445-55. [PMID: 21748594 PMCID: PMC4875174 DOI: 10.1007/s13238-011-1054-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 05/12/2011] [Indexed: 11/06/2022] Open
Abstract
After years of development, biosensors based on imaging ellipsometry and biosensors based on total internal reflection imaging ellipsometry have been successfully implemented in various engineering systems. Their experimental setups, detection principles, and biological and clinical applications are briefly reviewed.
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Affiliation(s)
- Yu Niu
- NML, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China
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249
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Ge C, Orosz KS, Armstrong NR, Saavedra SS. Poly(aniline) nanowires in sol-gel coated ITO: a pH-responsive substrate for planar supported lipid bilayers. ACS APPLIED MATERIALS & INTERFACES 2011; 3:2677-85. [PMID: 21707069 PMCID: PMC3145051 DOI: 10.1021/am2004637] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Facilitated ion transport across an artificial lipid bilayer coupled to a solid substrate is a function common to several types of bioelectronic devices based on supported membranes, including biomimetic fuel cells and ion channel biosensors. Described here is fabrication of a pH-sensitive transducer composed of a porous sol-gel layer derivatized with poly(aniline) (PANI) nanowires grown from an underlying planar indium-tin oxide (ITO) electrode. The upper sol-gel surface is hydrophilic, smooth, and compatible with deposition of a planar supported lipid bilayer (PSLB) formed via vesicle fusion. Conducting tip AFM was used to show that the PANI wires are connected to the ITO, which convert this electrode into a potentiometric pH sensor. The response to changes in the pH of the buffer contacting the PANI nanowire/sol-gel/ITO electrode is blocked by the very low ion permeability of the overlying fluid PSLB. The feasibility of using this assembly to monitor facilitated proton transport across the PSLB was demonstrated by doping the membrane with lipophilic ionophores that respond to a transmembrane pH gradient, which produced an apparent proton permeability several orders of magnitude greater than values measured for undoped lipid bilayers.
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Affiliation(s)
- Chenhao Ge
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - Kristina S. Orosz
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - Neal R. Armstrong
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
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250
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Gervais L, de Rooij N, Delamarche E. Microfluidic chips for point-of-care immunodiagnostics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:H151-76. [PMID: 21567479 DOI: 10.1002/adma.201100464] [Citation(s) in RCA: 266] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Indexed: 05/03/2023]
Abstract
We might be at the turning point where research in microfluidics undertaken in academia and industrial research laboratories, and substantially sponsored by public grants, may provide a range of portable and networked diagnostic devices. In this Progress Report, an overview on microfluidic devices that may become the next generation of point-of-care (POC) diagnostics is provided. First, we describe gaps and opportunities in medical diagnostics and how microfluidics can address these gaps using the example of immunodiagnostics. Next, we conceptualize how different technologies are converging into working microfluidic POC diagnostics devices. Technologies are explained from the perspective of sample interaction with components of a device. Specifically, we detail materials, surface treatment, sample processing, microfluidic elements (such as valves, pumps, and mixers), receptors, and analytes in the light of various biosensing concepts. Finally, we discuss the integration of components into accurate and reliable devices.
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Affiliation(s)
- Luc Gervais
- IBM Research-Zurich, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland
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