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Jiao Q, Zhang Y, Xie J, Liu F, Peng C, Pan Q. The dyeing effect of acridine orange for multiple plasmid systems is sensitive to temperature. J Cell Biochem 2024; 125:e30499. [PMID: 38009594 DOI: 10.1002/jcb.30499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 10/24/2023] [Accepted: 11/06/2023] [Indexed: 11/29/2023]
Abstract
The Goldview dyeing of the natural multiplasmid system of Lactobacillus plantarum PC518 was affected by temperature. The article want to identify the specific molecules that cause temperature sensitivity, then experiment on the universality of temperature sensitivity, and finally preliminarily analyze the influencing factors. At 5°C and 25°C, single pDNA, multiplasmid system, and linear DNA samples were electrophoretic on agarose gel prestained by Goldview 1, 2, 3, and acridine orange (AO), respectively. Eighteen vectors of Escherichia coli and two vectors shortened by cloning were mixed into multiplasmid systems with different member numbers, and then electrophoresis with AO staining was performed within the range of 5°C-45°C, with a linearized multiplasmid system as the control. The lane profiles (peaks) were captured with Image Lab 5.1 software. After electrophoresis, the nine-plasmid-2 system was dyed with AO solutions of different ionic strengths to detect the effect of ionic strength on temperature sensitivity. It was measured that the UV-visible absorption spectra of the nine-plasmid-2 system dissolved in AO solutions with different ionic strengths and pH. Further, a response surface model was constructed using Design-Expert.V8.0.6 software. The electrophoresis result showed that the multiplasmid system from L. plantarum PC518 stained by AO staining showed a weak band at 5°C and five bands at 25°C, which was similar to the result of staining with Goldview 1, 2, and 3. The synthetic nine-plasmid-1 system and nine-plasmid-2 system displayed different band numbers on the electrophoresis gel in the electrophoresis temperature range of 5°C-45°C, namely 3, 4, 6, 4, and 2 bands, as well as 2, 6, 7, 8, and 5 bands. Using the 1× Tris-acetate-EDTA (TAE)-AO solution, the poststaining results of the nine-plasmid-2 system in the temperature range of 5°C-45°C were 4, 6, 9, 9, and 7 bands, respectively. Further, using 5×, 10×, or 25× TAE buffer, the AO poststaining results at 5°C were 4, 2, and 1 bands, respectively. The ultraviolet spectral results from 5°C to 25°C showed that there was a significant difference (3.5 times) in the fluctuation amplitude at the absorption peak of 261.2 nm between 0× and 1-10× TAE-AO solution containing the nine-plasmid-2 system. Specifically, the fluctuation amplitudes of 0×, 1×, 5×, and 10× samples were 0.032, 0.109, 0.112, and 0.110, respectively. At the same time, using 1× and 10× TAE buffer, the AO-stained linear nine-plasmid-2 system remained stable and did not display temperature sensitivity. The response surface models of the AO-stained nine-plasmid-2 system intuitively displayed that the absorbance of the 1× TAE samples increased significantly with increasing temperature compared to the 0× TAE samples, regardless of the pH value. The findings confirmed a temperature-dependent effect in AO staining of natural or synthetic multiplasmid systems, with the optimum staining result occurring at 25°C. Ion strength was a necessary condition for the temperature sensitivity mechanism. This study layed the groundwork for further investigation into the reasons or underlying mechanisms of temperature sensitivity in AO staining of multiplasmid systems.
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Affiliation(s)
- Qiuxia Jiao
- Department of Pathogenic Biology, Chengdu Medical College, Chengdu, China
| | - Yumeng Zhang
- Department of Pathogenic Biology, Chengdu Medical College, Chengdu, China
| | - Juan Xie
- Department of Pathogenic Biology, Chengdu Medical College, Chengdu, China
| | - Fang Liu
- Department of Pathogenic Biology, Chengdu Medical College, Chengdu, China
| | - Chaoming Peng
- Department of General Practice, The First Affiliated Hospital, Chengdu Medical College, Chengdu, China
| | - Qu Pan
- Department of Pathogenic Biology, Chengdu Medical College, Chengdu, China
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2
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Eftaiha AF, Qaroush AK, Abo-Shunnar AS, Hammad SB, Assaf KI, Al-Qaisi FM, Paige MF. Interfacial Behavior of Modified Nicotinic Acid as Conventional/Gemini Surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:8524-8533. [PMID: 35775397 DOI: 10.1021/acs.langmuir.2c00596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report the synthesis and monolayer properties of conventional and gemini surfactants composed of nicotinic acid-based head groups with an emphasis on assessing how chemical structures affect the behavior of monolayers. A combination of Brewster angle microscopy and atomic force microscopy showed that pure hexadecyl nicotinate formed rippled strands in monolayers, and the gemini correspondents with either flexible or rigid organic linkers resulted in lobed-compact domains, which provides a simple method for patterning air-water and solid-air interfaces. The structural differences between conventional and gemini nicotinic acid-based surfactants could be explained by the interplay between line tension (that favors the formation of circular domains), balanced by dipole-dipole repulsion interaction between headgroups, which promotes extended domains. Miscibility and morphology studies of the modified nicotinic acid surfactants with palmitic acid demonstrated that the properties of mixed films can be controlled by the structure of the former. Excess Gibbs free energies of mixing indicated that the mixed films were less stable than the pure monolayers, and the positive deviations from ideality were the largest in the case of gemini surfactants.
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Affiliation(s)
- Ala'a F Eftaiha
- Department of Chemistry, Faculty of Science, The Hashemite University, P.O. Box 330127, Zarqa 13133, Jordan
| | - Abdussalam K Qaroush
- Department of Chemistry, Faculty of Science, The University of Jordan, Amman 11942, Jordan
| | - Ahmad S Abo-Shunnar
- Department of Chemistry, Faculty of Science, The Hashemite University, P.O. Box 330127, Zarqa 13133, Jordan
| | - Suhad B Hammad
- Department of Chemistry, Faculty of Science, The University of Jordan, Amman 11942, Jordan
| | - Khaleel I Assaf
- Department of Chemistry, Faculty of Science, Al-Balqa Applied University, Al-Salt 19117, Jordan
| | - Feda'a M Al-Qaisi
- Department of Chemistry, Faculty of Science, The Hashemite University, P.O. Box 330127, Zarqa 13133, Jordan
| | - Matthew F Paige
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada
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3
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Sharma B, Moghimianavval H, Hwang SW, Liu AP. Synthetic Cell as a Platform for Understanding Membrane-Membrane Interactions. MEMBRANES 2021; 11:912. [PMID: 34940413 PMCID: PMC8706075 DOI: 10.3390/membranes11120912] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/10/2021] [Accepted: 11/16/2021] [Indexed: 01/27/2023]
Abstract
In the pursuit of understanding life, model membranes made of phospholipids were envisaged decades ago as a platform for the bottom-up study of biological processes. Micron-sized lipid vesicles have gained great acceptance as their bilayer membrane resembles the natural cell membrane. Important biological events involving membranes, such as membrane protein insertion, membrane fusion, and intercellular communication, will be highlighted in this review with recent research updates. We will first review different lipid bilayer platforms used for incorporation of integral membrane proteins and challenges associated with their functional reconstitution. We next discuss different methods for reconstitution of membrane fusion and compare their fusion efficiency. Lastly, we will highlight the importance and challenges of intercellular communication between synthetic cells and synthetic cells-to-natural cells. We will summarize the review by highlighting the challenges and opportunities associated with studying membrane-membrane interactions and possible future research directions.
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Affiliation(s)
- Bineet Sharma
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
| | - Hossein Moghimianavval
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
| | - Sung-Won Hwang
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Allen P. Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48105, USA
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4
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Bibissidis N, Betlem K, Cordoyiannis G, Bonhorst FPV, Goole J, Raval J, Daniel M, Góźdź W, Iglič A, Losada-Pérez P. Correlation between adhesion strength and phase behaviour in solid-supported lipid membranes. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114492] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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5
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Majewska M, Mrdenovic D, Pieta I, Nowakowski R, Pieta P. Nanomechanical characterization of single phospholipid bilayer in ripple phase with PF-QNM AFM. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183347. [DOI: 10.1016/j.bbamem.2020.183347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/16/2020] [Accepted: 05/07/2020] [Indexed: 12/31/2022]
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6
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Galván-Hernández A, Kobayashi N, Hernández-Cobos J, Antillón A, Nakabayashi S, Ortega-Blake I. Morphology and dynamics of domains in ergosterol or cholesterol containing membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183101. [DOI: 10.1016/j.bbamem.2019.183101] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/02/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022]
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7
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Meingast C, Heldt CL. Arginine‐enveloped virus inactivation and potential mechanisms. Biotechnol Prog 2019; 36:e2931. [DOI: 10.1002/btpr.2931] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 10/09/2019] [Accepted: 10/14/2019] [Indexed: 11/06/2022]
Affiliation(s)
- Christa Meingast
- Department of Civil and Environmental Engineering Michigan Technological University Houghton Michigan
| | - Caryn L. Heldt
- Department of Chemical Engineering Michigan Technological University Houghton Michigan
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8
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Favela-Rosales F, Galván-Hernández A, Hernández-Cobos J, Kobayashi N, Carbajal-Tinoco MD, Nakabayashi S, Ortega-Blake I. A molecular dynamics study proposing the existence of statistical structural heterogeneity due to chain orientation in the POPC-cholesterol bilayer. Biophys Chem 2019; 257:106275. [PMID: 31790909 DOI: 10.1016/j.bpc.2019.106275] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/02/2019] [Accepted: 10/21/2019] [Indexed: 01/08/2023]
Abstract
We performed molecular dynamics simulations of a lipid bilayer consisting of POPC and cholesterol at temperatures from 283 to 308K and cholesterol concentrations from 0 to 50% mol/mol. The purpose of this study was to look for the existence of structural differences in the region delimited by these parameters and, in particular, in a region where coexistence of liquid disordered and liquid ordered phases has been proposed. Our interest in this range of concentration and temperature responds to the fact that polyene ionophore activity varies considerably along it. Two force fields, CHARMM36 and Slipids, were compared in order to determine the most suitable. Both force fields predict non-monotonic behaviors consistent with the existence of phase transitions. We found the presence of lateral structural heterogeneity, statistical in nature, in some of the bilayers occurring in this range of temperatures and sterol concentrations. This heterogeneity was produced by correlated ordering of the POPC tails and not due to cholesterol enrichment, and lasts for tens of nanoseconds. We relate these observations to the action of polyenes in these membranes.
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Affiliation(s)
- Fernando Favela-Rosales
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico; Tecnológico Nacional de México, Campus Zacatecas Occidente, Ave. Tecnológico No. 2000, Col. Loma la Perla, Sombrerete, Zacatecas, 99102, Mexico
| | - Arturo Galván-Hernández
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico
| | - Jorge Hernández-Cobos
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México Av. Universidad s/n Cuernavaca, Morelos, 62251, Mexico
| | - Naritaka Kobayashi
- Department of Chemistry, Faculty of Science, Saitama University, Shimo-Ohkubo 255, Sakura-Ku, Saitama City, 338-8570, Japan
| | - Mauricio D Carbajal-Tinoco
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico
| | - Seiichiro Nakabayashi
- Department of Chemistry, Faculty of Science, Saitama University, Shimo-Ohkubo 255, Sakura-Ku, Saitama City, 338-8570, Japan
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México Av. Universidad s/n Cuernavaca, Morelos, 62251, Mexico.
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9
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Liang X, Huang B, Wang Y, Li C, Liu X, Huang M, Li H. Photoelectrocatalytic oxidation of ascorbate promoted by glucose and tris-(hydroxylmethyl)-amino methane on cadmium sulfide/titanium dioxide electrodes for efficient visible light-enhanced fuel cells. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.05.128] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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Poursoroush A, Sperotto MM, Laradji M. Phase behavior of supported lipid bilayers: A systematic study by coarse-grained molecular dynamics simulations. J Chem Phys 2018; 146:154902. [PMID: 28433014 DOI: 10.1063/1.4981008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Solid-supported lipid bilayers are utilized by experimental scientists as models for biological membranes because of their stability. However, compared to free standing bilayers, their close proximity to the substrate may affect their phase behavior. As this is still poorly understood, and few computational studies have been performed on such systems thus far, here we present the results from a systematic study based on molecular dynamics simulations of an implicit-solvent model for solid-supported lipid bilayers with varying lipid-substrate interactions. The attractive interaction between the substrate and the lipid head groups that are closest to the substrate leads to an increased translocation of the lipids from the distal to the proximal bilayer-leaflet. This thereby leads to a transbilayer imbalance of the lipid density, with the lipid density of the proximal leaflet higher than that of the distal leaflet. Consequently, the order parameter of the proximal leaflet is found to be higher than that of the distal leaflet, the higher the strength of lipid interaction is, the stronger the effect. The proximal leaflet exhibits gel and fluid phases with an abrupt melting transition between the two phases. In contrast, below the melting temperature of the proximal leaflet, the distal leaflet is inhomogeneous with coexisting gel and fluid domains. The size of the fluid domains increases with increasing the strength of the lipid interaction. At low temperatures, the inhomogeneity of the distal leaflet is due to its reduced lipid density.
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Affiliation(s)
- Asma Poursoroush
- Department of Physics and Materials Science, The University of Memphis, Memphis, Tennessee 38152, USA
| | - Maria Maddalena Sperotto
- DTU Bioinformatics, Department of Bio and Health Informatics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Mohamed Laradji
- Department of Physics and Materials Science, The University of Memphis, Memphis, Tennessee 38152, USA
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11
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Isabettini S, Massabni S, Hodzic A, Durovic D, Kohlbrecher J, Ishikawa T, Fischer P, Windhab EJ, Walde P, Kuster S. Molecular engineering of lanthanide ion chelating phospholipids generating assemblies with a switched magnetic susceptibility. Phys Chem Chem Phys 2018; 19:20991-21002. [PMID: 28745755 DOI: 10.1039/c7cp03994h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lanthanide ion (Ln3+) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln3+ deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln3+ chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of nanometers in size were achieved presenting unprecedented magnetic alignments. The DMPE-Glu-DTPA/Ln3+ complex switched the Δχ, achieving perpendicular alignment of assemblies containing Dy3+ and parallel alignment of those containing Tm3+. Moreover, samples with chelated Yb3+ were more alignable than the Tm3+ chelating counterparts. Such a possibility has never been demonstrated for planar Ln3+ chelating polymolecular assemblies. The physico-chemical properties of these novel assemblies were further studied by monitoring the alignment behavior at different temperatures and by including 16 mol% of cholesterol (Chol-OH) in the phospholipid bilayer. The DMPE-Glu-DTPA/Ln3+ complex and the resulting assemblies are promising candidates for applications in numerous fields including pharmaceutical technologies, structural characterization of membrane biomolecules by NMR spectroscopy, as contrasting agents for magnetic resonance imaging, and for the development of smart optical gels.
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Affiliation(s)
- Stéphane Isabettini
- Laboratory of Food Process Engineering, ETH Zürich, Schmelzbergstrasse 7, 8092 Zürich, Switzerland.
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12
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Villeneuve M, Tanaka M, Saito N, Sakamoto H, Hayami Y. Uptake of iron (III)-ethylenediamine-N,N,N',N'-tetraacetic acid complex by phosphatidylcholine lipid film: Part I. Effect of bulk pH. Chem Phys Lipids 2017; 210:1-13. [PMID: 29223576 DOI: 10.1016/j.chemphyslip.2017.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/04/2017] [Accepted: 12/04/2017] [Indexed: 11/19/2022]
Abstract
We studied a ternary solutes aqueous solution of NaOH, iron (III)-ethylenediamine-N,N,N',N'-tetraacetic acid complex (Fe-edta), and 1,2-diheptanoyl-sn-glycero-3-phosphatidylcholine (DHPC)/air interface system to clarify the interactions between iron complexes and lipids with a phosphatidylcholine head group. The solution surface tension and pH were measured as functions of the total molality of NaOH, Fe-edta and DHPC, and the mole fractions of NaOH and DHPC. Rigorous thermodynamic equations were derived, in which the overall proton dissociation equilibria of Fe-edta and DHPC were taken into consideration, and applied to experimental data to obtain phase diagram of adsorption. It was found that (1) adsorption of Fe-edta at the solution/air interface with a DHPC monolayer was about 50-130 times higher than that without a DHPC monolayer and (2) when the bulk mole fraction of NaOH was high, Fe-edta tended to be expelled from the adsorbed film. The last finding suggests that the ambient pH significantly affects passive transport of the iron complex through a phospholipid-containing membrane into the cell interior.
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Affiliation(s)
- Masumi Villeneuve
- Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
| | - Mihoko Tanaka
- Division of Material Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
| | - Natsumi Saito
- Division of Material Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
| | - Hiroyasu Sakamoto
- Graduate School of Design, Kyushu University, 4-9-1 Shiobaru, Minami-ku, Fukuoka 815-8540, Japan
| | - Yoshiteru Hayami
- Department of Contemporary Social Studies, Faculty of Contemporary Social Studies, Chikushi Jogakuen University, 2-12-1 Ishizaka, Dazaifu, Fukuoka 818-0192, Japan
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13
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Kurniawan N, van Kempen THS, Sonneveld S, Rosalina TT, Vos BE, Jansen KA, Peters GWM, van de Vosse FN, Koenderink GH. Buffers Strongly Modulate Fibrin Self-Assembly into Fibrous Networks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:6342-6352. [PMID: 28558246 PMCID: PMC5489959 DOI: 10.1021/acs.langmuir.7b00527] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/27/2017] [Indexed: 05/20/2023]
Abstract
Fibrin is a plasma protein with a central role in blood clotting and wound repair. Upon vascular injury, fibrin forms resilient fibrillar networks (clots) via a multistep self-assembly process, from monomers, to double-stranded protofibrils, to a branched network of thick fibers. In vitro, fibrin self-assembly is sensitive to physicochemical conditions like the solution pH and ionic strength, which tune the strength of the noncovalent driving forces. Here we report a surprising finding that the buffer-which is necessary to control the pH and is typically considered to be inert-also significantly influences fibrin self-assembly. We show by confocal microscopy and quantitative light scattering that various common buffering agents have no effect on the initial assembly of fibrin monomers into protofibrils but strongly hamper the subsequent lateral association of protofibrils into thicker fibers. We further find that the structural changes are independent of the molecular structure of the buffering agents as well as of the activation mechanism and even occur in fibrin networks formed from platelet-poor plasma. This buffer-mediated decrease in protofibril bundling results in a marked reduction in the permeability of fibrin networks but only weakly influences the elastic modulus of fibrin networks, providing a useful tuning parameter to independently control the elastic properties and the permeability of fibrin networks. Our work raises the possibility that fibrin assembly in vivo may be regulated by variations in the acute-phase levels of bicarbonate and phosphate, which act as physiological buffering agents of blood pH. Moreover, our findings add a new example of buffer-induced effects on biomolecular self-assembly to recent findings for a range of proteins and lipids.
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Affiliation(s)
- Nicholas
A. Kurniawan
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Thomas H. S. van Kempen
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Stijn Sonneveld
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Tilaï T. Rosalina
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Bart E. Vos
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Karin A. Jansen
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
| | - Gerrit W. M. Peters
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Frans N. van de Vosse
- Department of Biomedical
Engineering & Institute for Complex
Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Gijsje H. Koenderink
- Department
of Systems Biophysics, AMOLF, Amsterdam 1009 DB, The Netherlands
- E-mail:
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Trewby W, Livesey D, Voïtchovsky K. Buffering agents modify the hydration landscape at charged interfaces. SOFT MATTER 2016; 12:2642-51. [PMID: 26837938 DOI: 10.1039/c5sm02445e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Buffering agents are widely used to stabilise the pH of solutions in soft matter and biological sciences. They are typically composed of weak acids and bases mixed in an aqueous solution, and can interact electrostatically with charged surfaces such as biomembranes. Buffers can induce protein aggregation and structural modification of soft interfaces, but a molecular-level picture is still lacking. Here we use high-resolution atomic force microscopy to investigate the effect of five commonly used buffers, namely 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 2-(N-morpholino)ethanesulfonic acid (MES), monosodium phosphate, saline sodium citrate (SSC) and tris(hydroxymethyl)aminomethane (Tris) on the hydration landscape of Muscovite mica in solution. Mica is an ideal model substrate due to its negative surface charge and identical lattice parameter when compared with gel-phase lipid bilayers. We show that buffer molecules can produce cohesive aggregates spanning over tens of nanometres of the interface. SSC, Tris and monosodium phosphate tend to create an amorphous mesh layer several molecules thick and with no preferential ordering. In contrast, MES and HEPES adopt epitaxial arrangements commensurate with the underlying mica lattice, suggesting that they offer the most suitable solution for high-resolution studies. To confirm that this effect persisted in biologically-relevant interfaces, the experiments were repeated on a silica-supported lipid bilayer. Similar trends were observed for this system using atomic force microscopy as well as ellipsometry. The effect of the buffering agents can be mitigated by the inclusion of salt which helps displace them from the interface.
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15
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Assemblies of pore-forming toxins visualized by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:500-11. [PMID: 26577274 DOI: 10.1016/j.bbamem.2015.11.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 10/23/2015] [Accepted: 11/09/2015] [Indexed: 02/05/2023]
Abstract
A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Alessandrini A, Facci P. Phase transitions in supported lipid bilayers studied by AFM. SOFT MATTER 2014; 10:7145-7164. [PMID: 25090108 DOI: 10.1039/c4sm01104j] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the capabilities of Atomic Force Microscopy (AFM) in the study of phase transitions in Supported Lipid Bilayers (SLBs). AFM represents a powerful technique to cover the resolution range not available to fluorescence imaging techniques and where spectroscopic data suggest what the relevant lateral scale for domain formation might be. Phase transitions of lipid bilayers involve the formation of domains characterized by different heights with respect to the surrounding phase and are therefore easily identified by AFM in liquid solution once the bilayer is confined to a flat surface. Even if not endowed with high time resolution, AFM allows light to be shed on some aspects related to lipid phase transitions in the case of both a single lipid component and lipid mixtures containing sterols also. We discuss here the obtained results in light of the peculiarities of supported lipid bilayer model systems.
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Affiliation(s)
- Andrea Alessandrini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Via Campi 213/A, 41125, Modena, Italy.
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Harb F, Simon A, Tinland B. Ripple formation in unilamellar-supported lipid bilayer revealed by FRAPP. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:140. [PMID: 24343762 DOI: 10.1140/epje/i2013-13140-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 12/06/2013] [Indexed: 06/03/2023]
Abstract
The mechanisms of formation and conditions of the existence of the ripple phase are fundamental thermodynamic questions with practical implications for medicine and pharmaceuticals. We reveal a new case of ripple formation occurring in unilamellar-supported bilayers in water, which results solely from the bilayer/support interaction, without using lipid mixtures or specific ions. This ripple phase is detected by FRAPP using diffusion coefficient measurements as a function of temperature: a diffusivity plateau is observed. It occurs in the same temperature range where ripple phase existence has been observed using other methods. When AFM experiments are performed in the appropriate temperature range the ripple phase is confirmed.
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Affiliation(s)
- Frédéric Harb
- CNRS, UMR7325, Aix-Marseille Univ., CINaM, 13288, Marseille, France
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18
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Creutz CE, Eaton JM, Harris TE. Assembly of high molecular weight complexes of lipin on a supported lipid bilayer observed by atomic force microscopy. Biochemistry 2013; 52:5092-102. [PMID: 23862673 DOI: 10.1021/bi4004765] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Lipins are phosphatidic acid phosphatases involved in the biosynthesis of triacylglycerols and phospholipids. They are associated with the endoplasmic reticulum but can also travel into the nucleus and alter gene expression. Previous studies indicate lipins in solution form high molecular weight complexes, possibly tetramers. This study was undertaken to determine if lipins form complexes on membranes as well. Murine lipin 1b was applied to a supported bilayer of phosphatidylcholine, phosphatidylserine, and cholesterol and examined by atomic force microscopy (AFM) over time. Lipin on bare mica appeared as a symmetric particle with a volume consistent with the size of a monomer. On the bilayer, lipin initially bound as asymmetric, curved particles that sometimes assembled into circular structures with an open center. Subsequently, lipin assemblies grew into large, symmetric particles with an average volume 12 times that of the monomer. Over time, some of the lipin assemblies were removed from the bilayer by the AFM probe leaving behind "footprints" composed of complex patterns that may reflect the substructure of the lipin assemblies. The lipin complexes appeared very flat, with a diameter 20 times their height. The footprints had a similar diameter, providing confirmation of the extensive deformation of the protein under the AFM probe. The ability of lipin to form large complexes on membranes may have significant implications for the local concentrations of the product, diacylglycerol, formed during hydrolysis of phosphatidic acid and for cooperative hormonal regulation of lipin activity through phosphorylation of one or more monomers in the complexes.
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Affiliation(s)
- Carl E Creutz
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, United States.
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Correlation between the ripple phase and stripe domains in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2849-58. [DOI: 10.1016/j.bbamem.2011.08.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/12/2011] [Accepted: 08/16/2011] [Indexed: 12/19/2022]
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20
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Hulme EC, Trevethick MA. Ligand binding assays at equilibrium: validation and interpretation. Br J Pharmacol 2011; 161:1219-37. [PMID: 20132208 DOI: 10.1111/j.1476-5381.2009.00604.x] [Citation(s) in RCA: 441] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The focus of this review paper is factors affecting data interpretation in ligand binding assays under equilibrium conditions. Protocols for determining K(d) (the equilibrium dissociation constant) and K(dA) (the equilibrium inhibitor constant) for receptor ligands are discussed. The basic theory describing the interaction of a radiotracer and an unlabelled competitor ligand with a receptor is developed. Inappropriate experimental design may result in ligand depletion and non-attainment of equilibrium, distorting the calculation of K(d) and K(dA) . Strategies, both theoretical and practical, will be given to avoid and correct such errors, thus leading to the determination of reliable values for these constants. In determining K(dA) from competition binding studies, two additional concepts are discussed. First, the necessity to measure an adequate specific binding signal from the bound radiotracer ligand limits the range of affinity constants that can be measured: a particular set of assay conditions may lead to an upper limit on the apparent affinity of unlabelled ligands. Second, an extension of the basic assay methodology can indicate whether the interaction between the tracer and a test ligand is mediated by a competitive or an allosteric mechanism. Finally, the review ends with a discussion of two factors that are often overlooked: buffer composition and the temperature at which the assay is conducted, and the impact these can have on affinity measurements and the understanding of drug interactions.
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Affiliation(s)
- Edward C Hulme
- Division of Physical Biochemistry, MRC National Institute for Medical Research, Mill Hill, London, UK.
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21
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Londoño-Londoño J, Lima VRD, Jaramillo C, Creczynski-pasa T. Hesperidin and hesperetin membrane interaction: Understanding the role of 7-O-glycoside moiety in flavonoids. Arch Biochem Biophys 2010; 499:6-16. [DOI: 10.1016/j.abb.2010.04.023] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 04/16/2010] [Accepted: 04/30/2010] [Indexed: 10/19/2022]
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22
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Oreopoulos J, Epand RF, Epand RM, Yip CM. Peptide-induced domain formation in supported lipid bilayers: direct evidence by combined atomic force and polarized total internal reflection fluorescence microscopy. Biophys J 2010; 98:815-23. [PMID: 20197035 DOI: 10.1016/j.bpj.2009.12.4327] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 11/25/2009] [Accepted: 12/09/2009] [Indexed: 12/01/2022] Open
Abstract
Direct visualization of the mechanism(s) by which peptides induce localized changes to the structure of membranes has high potential for enabling understanding of the structure-function relationship in antimicrobial and cell-penetrating peptides. We have applied a combined imaging strategy to track the interaction of a model antimicrobial peptide, PFWRIRIRR-amide, with bacterial membrane-mimetic supported phospholipid bilayers comprised of POPE/TOCL. Our in situ studies revealed rapid reorganization of the POPE/TOCL membrane into localized TOCL-rich domains with a concomitant change in the organization of the membranes themselves, as reflected by changes in fluorescent-membrane-probe order parameter, upon introduction of the peptide.
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Affiliation(s)
- John Oreopoulos
- Institute of Biomaterials and Biomedical Engineering, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Ontario, Canada
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23
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Giocondi MC, Yamamoto D, Lesniewska E, Milhiet PE, Ando T, Le Grimellec C. Surface topography of membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:703-18. [DOI: 10.1016/j.bbamem.2009.09.015] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/11/2009] [Accepted: 09/20/2009] [Indexed: 12/24/2022]
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El Kirat K, Morandat S, Dufrêne YF. Nanoscale analysis of supported lipid bilayers using atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:750-65. [DOI: 10.1016/j.bbamem.2009.07.026] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/17/2009] [Accepted: 07/23/2009] [Indexed: 12/11/2022]
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25
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Oreopoulos J, Yip CM. Combinatorial microscopy for the study of protein–membrane interactions in supported lipid bilayers: Order parameter measurements by combined polarized TIRFM/AFM. J Struct Biol 2009; 168:21-36. [DOI: 10.1016/j.jsb.2009.02.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 02/23/2009] [Accepted: 02/24/2009] [Indexed: 02/06/2023]
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Organization and synergistic binding of copine I and annexin A1 on supported lipid bilayers observed by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1950-61. [PMID: 19539605 DOI: 10.1016/j.bbamem.2009.06.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 05/26/2009] [Accepted: 06/11/2009] [Indexed: 01/24/2023]
Abstract
The transduction of signals across the plasma membrane of cells after receptor activation frequently involves the assembly of interacting protein molecules on the cytoplasmic face of the membrane. However, the structural organization and dynamics of the formation of such complexes has not been well defined. In this study atomic force microscopy was used to monitor the assemblies formed in vitro by two classes of calcium-dependent, membrane-binding proteins that participate in the formation of signaling complexes on membranes - the annexins and the copines. When applied to supported lipid bilayers composed of 25% brain phosphatidylserine and 75% dioleyl phosphatidylcholine in the presence of 1 mM Ca(2+) both human annexin A1 and human copine I bound only to specialized domains that appeared to be 0.5 to 1.0 nm lower than the rest of the bilayer. These domains may be enriched in phosphatidylserine and have a more disordered structure allowing probe penetration. Confinement of the binding of the proteins to these domains may be important in the process of concentrating other signaling proteins bound to the copine or annexin. The binding of the annexin promoted the growth of the domains and created additional binding space for the copine. This may reflect a general ability of annexins to alter membrane structure in such a way that C2 domain-containing proteins like copine can bind. Copine I formed a reticular lattice composed of linear elements approximately 45 nm long on the specialized domains. This lattice might provide a scaffold for the assembly and interaction of copine target proteins in signaling complexes.
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Böcker M, Muschter S, Schmitt EK, Steinem C, Schäffer TE. Imaging and patterning of pore-suspending membranes with scanning ion conductance microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:3022-3028. [PMID: 19437710 DOI: 10.1021/la8034227] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Nano-BLMs (black lipid membranes) suspending the pores of highly ordered porous silicon substrates have been proven useful for functional investigations of ion channel proteins by electrical readouts. With the aim to monitor the resistive behavior of nano-BLMs spatially resolved in a contact-free manner, we report here on the visualization of nano-BLMs by means of scanning ion conductance microscopy (SICM). Silicon surfaces with highly ordered pore arrays were coated with a gold layer and functionalized with octadecanethiol before a droplet of 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) (2% w/v) dissolved in n-decane was applied. The topography of DPhPC membranes suspending the pores was stably imaged for hours without mechanical contact using SICM. This suggests that SICM provides a significant advantage over atomic force microscopy, where mechanical interactions occur that easily damage the suspended membranes. Dynamic processes such as spreading and rupturing of membranes were spatially and temporally resolved. Furthermore, SICM was used to individually manipulate membranes suspending single pores, thereby writing lithographic patterns into the lipid. The process of local membrane manipulation was correlated to a characteristic signature in the simultaneously recorded ion current. The results show that SICM is well-suited both for contact-free imaging of soft suspended membranes and for local membrane manipulation.
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Affiliation(s)
- Matthias Böcker
- Institute of Applied Physics, University of Erlangen-Nuremberg, Staudtstr. 7, Bldg. A3, 91058 Erlangen, Germany
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28
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Chen M, Li M, Brosseau CL, Lipkowski J. AFM studies of the effect of temperature and electric field on the structure of a DMPC-cholesterol bilayer supported on a Au(111) electrode surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1028-1037. [PMID: 19113809 DOI: 10.1021/la802839f] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Atomic force microscopy (AFM) was used to characterize a phospholipid bilayer composed of 70 mol % 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 30 mol % cholesterol, at a Au(111) electrode surface. Results indicate that addition of cholesterol relaxes membrane elastic stress, increases membrane thickness, and reduces defect density. The thickness and thermotropic properties of the mixed DMPC-cholesterol bilayer supported at the gold electrode surface are quite similar to the properties of the mixed membrane in unilamellar vesicles. The stability of the supported membrane at potentials negative to the potential of zero charge E(pzc) was investigated. This study demonstrates that the bilayer supported at the gold electrode surface is stable provided the applied potential (E - E(pzc)) is less than -0.3 V. At larger polarizations, swelling of the membrane is observed. Polarizations larger than -1 V cause electrodewetting of the bilayer from the gold surface. At these negative potentials, the bilayer remains in close proximity to the metal surface, separated from it by a approximately 2 nm thick layer of electrolyte.
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Affiliation(s)
- Maohui Chen
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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29
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Sánchez-Verdejo T, Undabeytia T, Nir S, Maqueda C, Morillo E. Environmentally friendly slow release formulations of alachlor based on clay-phosphatidylcholine. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:5779-5784. [PMID: 18754508 DOI: 10.1021/es800743p] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A new clay-liposome complex was developed for reducing leaching of herbicides and contamination of groundwater. The liposomes were composed of the neutral and Environmental Protection Agency approved phospholipid phosphatidylcholine (PC). Adsorption of PC liposomes on the clay mineral montmorillonite could exceed the cation exchange capacity of the clay, and was well simulated by the Langmuir equation. X-ray diffraction results for 6 mM PC and 1.6 g/L clay (3 day incubation) yielded a basal spacing of 7.49 nm, which was interpreted as the formation of a supported planar bilayer on montmorillonite platelets. Fluorescence methods demonstrated structural changes which reflected adsorption of PC followed by loss of vesicle integrity as measured by the penetration of dithionite into the internal monolayer of fluorescently labeled liposomes, resulting in a decrease in fluorescence intensity to 18% of initial after 4 h. Energy transfer was demonstrated after 1 h from labeled liposomes to montmorillonite labeled by an acceptor. The neutral herbicide alachlor adsorbed on the liposome-clay complex, yielding a formulation of up to 40% active ingredient, and 1.6-fold reduction in herbicide release in comparison to the commercial formulation. Hence, the PC-montmorillonite complex can form a basis for environmentally friendly formulations of herbicides, which would yield reduced leaching.
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30
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Qaqish SE, Paige MF. Rippled domain formation in phase-separated mixed Langmuir-Blodgett films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:6146-6153. [PMID: 18489185 DOI: 10.1021/la8002146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The morphology and composition of phase-separated Langmuir and Langmuir-Blodgett films of stearic acid (C17H35COOH) (SA) mixed with perfluorotetradecanoic acid (C13F27COOH) (PA) have been investigated using a combination of atomic force microscopy (AFM) measurements and surface pressure-area isotherms. At elevated surface pressures, the mixed film phase-separated to form a distinct series of lines (ripples), as opposed to the hexagons that have previously been observed with mixed films with longer alkyl chain fatty acids. At low surface pressures, phase separation is still observed, though a range of different domain structures was formed. The chemical composition of the phase-separated domains has been investigated by AFM-based compositional mapping, which has allowed unambiguous identification of the chemical composition of the domains. A simple mechanistic model describing how domain formation takes place in this system is presented.
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Affiliation(s)
- Shatha E Qaqish
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, Canada S7N 5C9
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31
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Past, present and future of atomic force microscopy in life sciences and medicine. J Mol Recognit 2008; 20:418-31. [PMID: 18080995 DOI: 10.1002/jmr.857] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
To introduce this special issue of the Journal of Molecular Recognition dedicated to the applications of atomic force microscopy (AFM) in life sciences, this paper presents a short summary of the history of AFM in biology. Based on contributions from the first international conference of AFM in biological sciences and medicine (AFM BioMed Barcelona, 19-21 April 2007), we present and discuss recent progress made using AFM for studying cells and cellular interactions, probing single molecules, imaging biosurfaces at high resolution and investigating model membranes and their interactions. Future prospects in these different fields are also highlighted.
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Oliynyk V, Jäger M, Heimburg T, Buckin V, Kaatze U. Lipid membrane domain formation and alamethicin aggregation studied by calorimetry, sound velocity measurements, and atomic force microscopy. Biophys Chem 2008; 134:168-77. [DOI: 10.1016/j.bpc.2008.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 02/07/2008] [Accepted: 02/09/2008] [Indexed: 11/29/2022]
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Abstract
Electric-field induced changes in structure and conductivity of supported bilayer lipid membranes (SLM) have been studied at submicroscopic resolution using atomic force microscopy and electrochemical impedance spectroscopy. The SLMs are formed on gold surfaces modified with mixed self-assembled monolayers of a cholesterol-tether and 6-mercaptohexanol. At applied potentials of < or =-0.25 V versus standard hydrogen electrode, the conductance of the SLM increases and membrane areas of <150 nm in size are found to elevate from the surface up to 15 nm in height. To estimate the electric field experienced by the lipid membrane, electrowetting has been used to determine the point of zero charge of a 6-mercaptohexanol-modified surface (0.19 +/- 0.13 V versus standard hydrogen electrode). The effects of electric fields on the structure and conductance of supported membranes are discussed.
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34
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Blistering of supported lipid membranes induced by Phospholipase D, as observed by real-time atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:276-82. [DOI: 10.1016/j.bbamem.2007.09.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 09/11/2007] [Accepted: 09/28/2007] [Indexed: 11/21/2022]
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35
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Brasseur R, Deleu M, Mingeot-Leclercq MP, Francius G, Dufrêne YF. Probing peptide–membrane interactions using AFM. SURF INTERFACE ANAL 2008. [DOI: 10.1002/sia.2682] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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36
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Vallejo AA, Velázquez JB, Fernández MS. Lateral organization of mixed, two-phosphatidylcholine liposomes as investigated by GPS, the slope of Laurdan generalized polarization spectra. Arch Biochem Biophys 2007; 466:145-54. [PMID: 17679103 DOI: 10.1016/j.abb.2007.06.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 06/29/2007] [Accepted: 06/30/2007] [Indexed: 11/18/2022]
Abstract
The effect of the excitation or emission wavelengths on Laurdan generalized polarization (GP) can be evaluated by GPS, a quantitative, simplified determination of the GP spectrum slope, the thermotropic dependence of which allows the assessment of phospholipid lamellar membrane phase, as shown in a recent publication of our laboratory [J.B. Velázquez, M.S. Fernández, Arch. Biochem. Biophys. 455 (2006) 163-174]. In the present work, we applied Laurdan GPS to phase transition studies of mixed, two-phosphatidylcholine liposomes prepared from variable proportions of dimyristoyl- and dipalmitoylphosphatidylcholine (DMPC and DPPC, respectively). We have found that the GPS function reports a clear limit between the gel/liquid-crystalline phase coexistence region and the liquid-crystalline state, not only at a certain temperature T(c) for liposomes of constant composition submitted to temperature scans, but also at a defined mole fraction X(c), for two-component liposomes of variable composition at constant temperature. The T(c) or the X(c) values obtained from GPS vs. temperature or GPS vs. composition plots, respectively, allow the construction of a partial phase diagram for the DMPC-DPPC mixtures, showing the boundary between the two-phase coexisting region and the liquid-crystalline state. Likewise, at the onset of the transition region, i.e., the two-phase coexisting region as detected by GPS, it is possible to determine, although with less precision, a temperature T(o) or a mole fraction X(o) defining a boundary located below but near the limit between the gel and ripple phase, reported in the literature. These GPS results are consistent with the proposal by several authors that a fraction of L(alpha) phospholipids coexists with gel phospholipids in the rippled phase.
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Affiliation(s)
- Alba A Vallejo
- Department of Biochemistry, Centro de Investigación y de Estudios Avanzados del I.P.N., P.O. Box 14.740, 07000 México D. F., Mexico
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Brasseur R, Braun N, El Kirat K, Deleu M, Mingeot-Leclercq MP, Dufrêne YF. The biologically important surfactin lipopeptide induces nanoripples in supported lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:9769-72. [PMID: 17696376 DOI: 10.1021/la7014868] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Under specific conditions, lipid membranes form ripple phases with intriguing nanoscale undulations. Here, we show using in situ atomic force microscopy (AFM) that the biologically important surfactin lipopeptide induces nanoripples of 30 nm periodicity in dipalmitoyl phosphatidylcholine (DPPC) bilayers at 25 degrees (i.e. well below the pretransition temperature of DPPC). Whereas most undulations formed the classical straight orientation with characteristic angle changes of 120 degrees , some of them also displayed unusual circular orientations. Strikingly, ripple structures were formed at 15% surfactin but were rarely or never observed at 5 and 30% surfactin, emphasizing the important role played by the surfactin concentration. Theoretical simulations corroborated the AFM data by revealing the formation of stable surfactin/lipid assemblies with positive curvature.
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Affiliation(s)
- Robert Brasseur
- Centre de Biophysique Moléculaire Numérique, Faculté Universitaire des Sciences Agronomiques de Gembloux, Passage des Déportés 2, B-5030 Gembloux, Belgium
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38
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Yoder NC, Kalsani V, Schuy S, Vogel R, Janshoff A, Kumar K. Nanoscale patterning in mixed fluorocarbon-hydrocarbon phospholipid bilayers. J Am Chem Soc 2007; 129:9037-43. [PMID: 17602478 PMCID: PMC2507729 DOI: 10.1021/ja070950l] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A growing body of literature suggests that fluorocarbons can direct self-assembly within hydrocarbon environments. We report here the fabrication and characterization of supported lipid bilayers (SLBs) composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and a synthetic, fluorocarbon-functionalized analogue, 1. AFM investigation of these model membranes reveals an intricate, composition-dependent domain structure consisting of approximately 50 nm stripes interspersed between approximately 1 microm sized domains. Although DSC of 1 showed a phase transition near room temperature, DSC of DPPC:1 mixtures exhibited complex phase behavior suggesting domain segregation. Finally, temperature-dependent AFM of DPPC:1 bilayers shows that, while the stripe structures can be melted above the Tm of 1, the stripes and domains result from immiscibility of the hydrocarbon and fluorocarbon lipid gel phases. Fluorination appears to be a promising strategy for chemical self-assembly in two dimensions. In particular, because no modification is made to the lipid headgroups, it may be useful for nanopatterning biologically relevant ligands on bilayers in vitro or in living cells.
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Affiliation(s)
| | | | - Steffen Schuy
- Institute for Physical Chemistry, University of Mainz, 55128 Mainz, Germany
| | - Reiner Vogel
- Institute for Molecular Medicine and Cell Research, University of Freiburg, 79104 Freiburg, Germany
| | - Andreas Janshoff
- Institute for Physical Chemistry, University of Mainz, 55128 Mainz, Germany
| | - Krishna Kumar
- Department of Chemistry, Tufts University, Medford MA 02155
- Cancer Center, Tufts-New England Medical Center, Boston MA 02110
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El Kirat K, Morandat S. Cholesterol modulation of membrane resistance to Triton X-100 explored by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2300-9. [PMID: 17560898 DOI: 10.1016/j.bbamem.2007.05.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Revised: 04/23/2007] [Accepted: 05/03/2007] [Indexed: 02/05/2023]
Abstract
Biomembranes are not homogeneous, they present a lateral segregation of lipids and proteins which leads to the formation of detergent-resistant domains, also called "rafts". These rafts are particularly enriched in sphingolipids and cholesterol. Despite the huge body of literature on raft insolubility in non-ionic detergents, the mechanisms governing their resistance at the nanometer scale still remain poorly documented. Herein, we report a real-time atomic force microscopy (AFM) study of model lipid bilayers exposed to Triton X-100 (TX-100) at different concentrations. Different kinds of supported bilayers were prepared with dioleoylphosphatidylcholine (DOPC), sphingomyelin (SM) and cholesterol (Chol). The DOPC/SM 1:1 (mol/mol) membrane served as the non-resistant control, and DOPC/SM/Chol 2:1:1 (mol/mol/mol) corresponded to the raft-mimicking composition. For all the lipid compositions tested, AFM imaging revealed that TX-100 immediately solubilized the DOPC fluid phase leaving resistant patches of membrane. For the DOPC/SM bilayers, the remaining SM-enriched patches were slowly perforated leaving crumbled features reminiscent of the initial domains. For the raft model mixture, no holes appeared in the remaining SM/Chol patches and some erosion occurred. This work provides new, nanoscale information on the biomembranes' resistance to the TX-100-mediated solubilization, and especially about the influence of Chol.
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Affiliation(s)
- Karim El Kirat
- Laboratoire de Biomécanique et Génie Biomédical, UMR-CNRS 6600, Université de Technologie de Compiègne, BP 20529, 60205 Compiègne Cedex, France
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Abstract
The creation of three-dimensional structures in supported lipid bilayers has been examined. In bilayers, shape transformations can be triggered by adjusting a variety of parameters. Here, it is shown that bilayers composed of phosphatidylcholine and phosphatidic acid can be induced to reversibly form cap structures when exposed to an asymmetry in ionic strength. The structures that form depend on the asymmetry in the ionic strength and the amount of anionic lipid. Other factors that may be of importance in the creation of the structures, expansion forces, osmotic forces, and the bilayer-support interaction are discussed. The cap structures have the potential to be of considerable utility in examining the effect that curvature has on membrane processes.
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Affiliation(s)
- Lee R Cambrea
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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Oliynyk V, Kaatze U, Heimburg T. Defect formation of lytic peptides in lipid membranes and their influence on the thermodynamic properties of the pore environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:236-45. [PMID: 17141732 DOI: 10.1016/j.bbamem.2006.10.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 10/10/2006] [Accepted: 10/11/2006] [Indexed: 10/24/2022]
Abstract
We present an experimental study of the pore formation processes of small amphipathic peptides in model phosphocholine lipid membranes. We used atomic force microscopy to characterize the spatial organization and structure of alamethicin- and melittin-induced defects in lipid bilayer membranes and the influence of the peptide on local membrane properties. Alamethicin induced holes in gel DPPC membranes were directly visualized at different peptide concentrations. We found that the thermodynamic state of lipids in gel membranes can be influenced by the presence of alamethicin such that nanoscopic domains of fluid lipids form close to the peptide pores, and that the elastic constants of the membrane are altered in their vicinity. Melittin-induced holes were visualized in DPPC and DLPC membranes at room temperature in order to study the influence of the membrane state on the peptide induced hole formation. Also differential scanning calorimetry was used to investigate the effect of alamethicin on the lipid membrane phase behaviour.
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Affiliation(s)
- Vitaliy Oliynyk
- Complex Fluids Group, Drittes Physikalisches Institut, Georg-August Universität, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
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Seu KJ, Pandey AP, Haque F, Proctor EA, Ribbe AE, Hovis JS. Effect of surface treatment on diffusion and domain formation in supported lipid bilayers. Biophys J 2007; 92:2445-50. [PMID: 17218468 PMCID: PMC1864818 DOI: 10.1529/biophysj.106.099721] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Supported lipid bilayers are widely used as model systems due to their robustness. Due to the solid support, the properties of supported lipid bilayers are different from those of freestanding bilayers. In this article, we examine whether different surface treatments affect the properties of supported lipid bilayers. It will be shown that depending on the treatment method, the diffusion of the lipids can be adjusted approximately threefold without altering the composition. Additionally, as the bilayer-support interaction decreases, it becomes easier to form coexisting liquid-ordered and liquid-disordered domains. The physical/chemical alterations that result from the different treatment methods will be discussed.
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Affiliation(s)
- Kalani J Seu
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2018, USA
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Morandat S, El Kirat K. Membrane resistance to Triton X-100 explored by real-time atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:5786-91. [PMID: 16768509 DOI: 10.1021/la0604228] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Lateral segregation of lipids and proteins in biological membranes leads to the formation of detergent-resistant domains, also called "rafts". Understanding the mechanisms governing the biomembrane's resistance to solubilization by detergents is crucial in biochemical research. Here, we used real-time atomic force microscopy (AFM) imaging to visualize the behavior of a model supported lipid bilayer in the presence of different Triton X-100 (TX-100) concentrations. Mixed dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC) supported bilayers were prepared by vesicle fusion. Real-time AFM imaging revealed that, at concentrations below the critical micelle concentration (CMC), TX-100 did not solubilize the bilayer, but the DPPC domains were eroded in a time-dependent manner. This effect was attributed to the DPPC molecular packing disorganization by the detergent starting from the DOPC/DPPC interface. Just above the CMC, the detergent led to a complete solubilization of the DOPC matrix, leaving the DPPC domains unaltered. At higher TX-100 concentrations, the DOPC was also immediately removed just after detergent addition, and the DPPC domains remaining on the mica surface appeared to be more swollen and were gradually solubilized. This progressive solubilization of the DPPC remaining phase did not start at the edge of the domains but from holes appearing and expanding at the center of DPPC patches. The swelling of the DPPC domains was directly correlated with TX-100 concentration above the CMC and with detergent intercalation between DPPC molecules. We are convinced that this approach will provide a key system to elucidate the physical mechanisms of membrane solubilization by nonionic detergents.
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Affiliation(s)
- Sandrine Morandat
- Laboratoire de Génie Enzymatique et Cellulaire, Université de Technologie de Compiègne, UMR-CNRS 6022, BP 20529, 60205 Compiègne Cedex, France
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Connell SD, Smith DA. The atomic force microscope as a tool for studying phase separation in lipid membranes. Mol Membr Biol 2006; 23:17-28. [PMID: 16600898 DOI: 10.1080/09687860500501158] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Atomic force microscopy has developed into a powerful tool in the study of phase separation in lipid bilayers. Its ability to image a semi-fluid surface under buffer at nanometre lateral resolution and Angstrom resolution vertically allows us to distinguish phase separated lipid domains, models of the elusive rafts postulated to exist as functional platforms in the cellular membrane, which may only rise 0.3 nm above the surrounding membrane. This review charts the history of this development, and includes a description of sample preparation techniques, factors affecting image contrast mechanisms, its use in the investigation of the pre-transition ripple phase, and in the localization of cell surface proteins.
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Affiliation(s)
- Simon D Connell
- Astbury Centre for Structural Molecular Biology and School of Physics and Astronomy, University of Leeds, UK
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Mahajan N, Zhao Y, Du T, Fang J. Nanoscale ripples in self-assembled lipid tubules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:1973-5. [PMID: 16489777 DOI: 10.1021/la051751n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Self-assembled cylindrical tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC) have been studied by atomic force microscopy in both the height and amplitude modes. Nanoscale ripple structures in the cylindrical lipid tubules are clearly resolved in amplitude mode images. The periodicity of the ripples is found to be 200 +/- 30 nm for tubules with diameters in the range from 200 to 650 nm. The angle of the ripples with respect to the equator of the tubules shows a bimodal distribution with centers at approximately 28 degrees and approximately 5 degrees.
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Affiliation(s)
- Nidhi Mahajan
- Advanced Materials Processing and Analysis Center and Department of Mechanical, Materials, and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA
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46
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Chapter 4 Visualization and Characterization of Domains in Supported Model Membranes. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1554-4516(05)03004-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Pedersen TB, Kaasgaard T, Jensen MØ, Frokjaer S, Mouritsen OG, Jørgensen K. Phase behavior and nanoscale structure of phospholipid membranes incorporated with acylated C14-peptides. Biophys J 2005; 89:2494-503. [PMID: 16100273 PMCID: PMC1366748 DOI: 10.1529/biophysj.105.060756] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2005] [Accepted: 07/05/2005] [Indexed: 11/18/2022] Open
Abstract
The thermotropic phase behavior and lateral structure of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers containing an acylated peptide has been characterized by differential scanning calorimetry (DSC) on vesicles and atomic force microscopy (AFM) on mica-supported bilayers. The acylated peptide, which is a synthetic decapeptide N-terminally linked to a C14 acyl chain (C14-peptide), is incorporated into DPPC bilayers in amounts ranging from 0-20 mol %. The calorimetric scans of the two-component system demonstrate a distinct influence of the C14-peptide on the lipid bilayer thermodynamics. This is manifested as a concentration-dependent downshift of both the main phase transition and the pretransition. In addition, the main phase transition peak is significantly broadened, indicating phase coexistence. In the AFM imaging scans we found that the C14-peptide, when added to supported gel phase DPPC bilayers, inserts preferentially into preexisting defect regions and has a noticeable influence on the organization of the surrounding lipids. The presence of the C14-peptide gives rise to a laterally heterogeneous bilayer structure with coexisting lipid domains characterized by a 10 A height difference. The AFM images also show that the appearance of the ripple phase of the DPPC lipid bilayers is unaffected by the C14-peptide. The experimental results are supported by molecular dynamics simulations, which show that the C14-peptide has a disordering effect on the lipid acyl chains and causes a lateral expansion of the lipid bilayer. These effects are most pronounced for gel-like bilayer structures and support the observed downshift in the phase-transition temperature. Moreover, the molecular dynamics data indicate a tendency of a tryptophan residue in the peptide sequence to position itself in the bilayer headgroup region.
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Affiliation(s)
- Tina B Pedersen
- Department of Pharmaceutics, The Danish University of Pharmaceutical Sciences, DK-2100 Copenhagen Ø, Denmark
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Oncins G, Garcia-Manyes S, Sanz F. Study of frictional properties of a phospholipid bilayer in a liquid environment with lateral force microscopy as a function of NaCl concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:7373-9. [PMID: 16042468 DOI: 10.1021/la050644q] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Friction properties of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-supported planar bilayers deposited on mica were tested in a liquid environment by lateral force microscopy. The presence of these bilayers was detected by imaging and force measurements with atomic force microscopy. To test how the presence of NaCl affects the frictional properties of the phospholipid bilayers, four DMPC bilayers were prepared on mica in saline media ranging from 0 to 0.1 M NaCl. Changes in the lateral vs vertical force curves were recorded as a function of NaCl concentration and related to structural changes induced in the DMPC bilayer by electrolyte ions. Three friction regimes were observed as the vertical force exerted by the tip on the bilayer increased. To relate the friction response to the structure of the DMPC bilayer, topographic images were recorded at the same time as friction data. Ions in solution screened charges present in DMPC polar heads, leading to more compact bilayers. As a consequence, the vertical force at which the bilayer broke during friction experiments increased with NaCl concentration. In addition, the topographic images showed that low-NaCl-concentration bilayers recover more easily due to the low cohesion between phospholipid molecules.
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Affiliation(s)
- Gerard Oncins
- CREBEC and Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain
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Lu Q, Chen X, Wu Y, Hu S. Studies on direct electron transfer and biocatalytic properties of heme proteins in lecithin film. Biophys Chem 2005; 117:55-63. [PMID: 15907360 DOI: 10.1016/j.bpc.2005.04.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Accepted: 03/04/2005] [Indexed: 10/25/2022]
Abstract
Myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP) were incorporated in lecithin (PC) film on glassy carbon (GC) electrode by the method of vesicle-fusion. A pair of well-defined and quasi-reversible cyclic voltammetric peaks was obtained, which reflected the direct electron transfer of heme proteins. UV-Vis and reflectance absorption infrared (RAIR) spectroscopy showed that proteins in PC films remained at their secondary structure similar to their native states. Scanning electron microscopy (SEM) demonstrated the interaction between the proteins and PC would make the morphology of protein-PC films very different from the PC films alone. The immobilized proteins retained their biocatalytic activity to the reduction of NO and hydrogen peroxide, which provide the perspective to be the third generation sensors.
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Affiliation(s)
- Qing Lu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China
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50
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El Kirat K, Burton I, Dupres V, Dufrene YF. Sample preparation procedures for biological atomic force microscopy. J Microsc 2005; 218:199-207. [PMID: 15958012 DOI: 10.1111/j.1365-2818.2005.01480.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Since the late 1980s, atomic force microscopy (AFM) has been increasingly used in biological sciences and it is now established as a versatile tool to address the structure, properties and functions of biological specimens. AFM is unique in that it provides three-dimensional images of biological structures, including biomolecules, lipid films, 2D protein crystals and cells, under physiological conditions and with unprecedented resolution. A crucial prerequisite for successful, reliable biological AFM is that the samples need to be well attached to a solid substrate using appropriate, nondestructive methods. In this review, we discuss common techniques for immobilizing biological specimens for AFM studies.
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Affiliation(s)
- K El Kirat
- Unité de chimie des interfaces, Université catholique de Louvain, Belgium
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