1
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Bao P, Phillips K, Raval R. Membrane Proteins in Action Monitored by pH-Responsive Liquid Crystal Biosensors. ACS APPLIED MATERIALS & INTERFACES 2024; 16:31843-31850. [PMID: 38841859 PMCID: PMC11194810 DOI: 10.1021/acsami.4c06614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 05/30/2024] [Accepted: 05/31/2024] [Indexed: 06/07/2024]
Abstract
Liquid crystal (LC) biosensors have received significant attention for their potential applications for point-of-care devices due to their sensitivity, low cost, and easy read-out. They have been employed to detect a wide range of important biological molecules. However, detecting the function of membrane proteins has been extremely challenging due to the difficulty of integrating membrane proteins, lipid membranes, and LCs into one system. In this study, we addressed this challenge by monitoring the proton-pumping function of bacteriorhodopsin (bR) using a pH-sensitive LC thin film biosensor. To achieve this, we deposited purple membranes (PMs) containing a 2D crystal form of bRs onto an LC-aqueous interface. Under light, the PM patches changed the local pH at the LC-aqueous interface, causing a color change in the LC thin film that is observable through a polarizing microscope with crossed polarizers. These findings open up new opportunities to study the biofunctions of membrane proteins and their induced local environmental changes in a solution using LC biosensors.
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Affiliation(s)
- Peng Bao
- Open Innovation
Hub for Antimicrobial
Surfaces, Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX, U.K.
| | - Kyle Phillips
- Open Innovation
Hub for Antimicrobial
Surfaces, Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX, U.K.
| | - Rasmita Raval
- Open Innovation
Hub for Antimicrobial
Surfaces, Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX, U.K.
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2
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Lei H, Zhang J, Li Y, Wang X, Qin M, Wang W, Cao Y. Histidine-Specific Bioconjugation for Single-Molecule Force Spectroscopy. ACS NANO 2022; 16:15440-15449. [PMID: 35980082 DOI: 10.1021/acsnano.2c07298] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Atomic force microscopy (AFM) based single-molecule force spectroscopy (SMFS) is a powerful tool to study the mechanical properties of proteins. In these experiments, site-specific immobilization of proteins is critical, as the tether determines the direction and amplitude of forces applied to the protein of interest. However, existing methods are mainly based on thiol chemistry or specific protein tags, which cannot meet the need of many challenging experiments. Here, we developed a histidine-specific phosphorylation strategy to covalently anchor proteins to an AFM cantilever tip or the substrate via their histidine tag or surface-exposed histidine residues. The formed covalent linkage was mechanically stable with rupture forces of over 1.3 nN. This protein immobilization method considerably improved the pickup rate and data quality of SMFS experiments. We further demonstrated the use of this method to explore the pulling-direction-dependent mechanical stability of green fluorescent protein and the unfolding of the membrane protein archaerhodopsin-3.
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Affiliation(s)
- Hai Lei
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University 22 Hankou Road, Nanjing 210093, People's Republic of China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University 163 Xianlin Road, Nanjing 210023, People's Republic of China
| | - Junsheng Zhang
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University 22 Hankou Road, Nanjing 210093, People's Republic of China
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325001, People's Republic of China
| | - Ying Li
- Institute of Advanced Materials and Flexible Electronics (IAMFE), School of Chemistry and Materials Science, Nanjing University of Information Science & Technology 219 Ningliu Road, Nanjing, 210044, People's Republic of China
| | - Xin Wang
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325001, People's Republic of China
| | - Meng Qin
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University 22 Hankou Road, Nanjing 210093, People's Republic of China
| | - Wei Wang
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University 22 Hankou Road, Nanjing 210093, People's Republic of China
| | - Yi Cao
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University 22 Hankou Road, Nanjing 210093, People's Republic of China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University 163 Xianlin Road, Nanjing 210023, People's Republic of China
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325001, People's Republic of China
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250021, People's Republic of China
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3
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Ido S, Kobayashi K, Oyabu N, Hirata Y, Matsushige K, Yamada H. Structured Water Molecules on Membrane Proteins Resolved by Atomic Force Microscopy. NANO LETTERS 2022; 22:2391-2397. [PMID: 35274954 DOI: 10.1021/acs.nanolett.2c00029] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Water structuring on the outer surface of protein molecules called the hydration shell is essential as well as the internal water structures for higher-order structuring of protein molecules and their biological activities in vivo. We now show the molecular-scale hydration structure measurements of native purple membrane patches composed of proton pump proteins by a noninvasive three-dimensional force mapping technique based on frequency modulation atomic force microscopy. We successfully resolved the ordered water molecules localized near the proton uptake channels on the cytoplasmic side of the individual bacteriorhodopsin proteins in the purple membrane. We demonstrate that the three-dimensional force mapping can be widely applicable for molecular-scale investigations of the solid-liquid interfaces of various soft nanomaterials.
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Affiliation(s)
- Shinichiro Ido
- Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Kei Kobayashi
- Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Noriaki Oyabu
- Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Yoshiki Hirata
- National Institute of Advanced Industrial Science and Technology, 1-1 Umezono, Tsukuba, Ibaraki 305-8566, Japan
| | - Kazumi Matsushige
- Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Hirofumi Yamada
- Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
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4
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Fang B, Zhao L, Du X, Liu Q, Yang H, Li F, Sheng Y, Zhao W, Zhong H. Studying the
Rhodopsin‐Like
G Protein Coupled Receptors by Atomic Force Microscopy. Cytoskeleton (Hoboken) 2022; 78:400-416. [DOI: 10.1002/cm.21692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/09/2022] [Accepted: 01/13/2022] [Indexed: 11/10/2022]
Affiliation(s)
- Bin Fang
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Li Zhao
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Xiaowei Du
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Qiyuan Liu
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
- School of Basic Medicine Gannan Medical University Ganzhou People's Republic of China
| | - Hui Yang
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Fangzuo Li
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Yaohuan Sheng
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Weidong Zhao
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Haijian Zhong
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
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5
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Free-energy changes of bacteriorhodopsin point mutants measured by single-molecule force spectroscopy. Proc Natl Acad Sci U S A 2021; 118:2020083118. [PMID: 33753487 DOI: 10.1073/pnas.2020083118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Single amino acid mutations provide quantitative insight into the energetics that underlie the dynamics and folding of membrane proteins. Chemical denaturation is the most widely used assay and yields the change in unfolding free energy (ΔΔG). It has been applied to >80 different residues of bacteriorhodopsin (bR), a model membrane protein. However, such experiments have several key limitations: 1) a nonnative lipid environment, 2) a denatured state with significant secondary structure, 3) error introduced by extrapolation to zero denaturant, and 4) the requirement of globally reversible refolding. We overcame these limitations by reversibly unfolding local regions of an individual protein with mechanical force using an atomic-force-microscope assay optimized for 2 μs time resolution and 1 pN force stability. In this assay, bR was unfolded from its native bilayer into a well-defined, stretched state. To measure ΔΔG, we introduced two alanine point mutations into an 8-amino-acid region at the C-terminal end of bR's G helix. For each, we reversibly unfolded and refolded this region hundreds of times while the rest of the protein remained folded. Our single-molecule-derived ΔΔG for mutant L223A (-2.3 ± 0.6 kcal/mol) quantitatively agreed with past chemical denaturation results while our ΔΔG for mutant V217A was 2.2-fold larger (-2.4 ± 0.6 kcal/mol). We attribute the latter result, in part, to contact between Val217 and a natively bound squalene lipid, highlighting the contribution of membrane protein-lipid contacts not present in chemical denaturation assays. More generally, we established a platform for determining ΔΔG for a fully folded membrane protein embedded in its native bilayer.
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6
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Müller DJ, Dumitru AC, Lo Giudice C, Gaub HE, Hinterdorfer P, Hummer G, De Yoreo JJ, Dufrêne YF, Alsteens D. Atomic Force Microscopy-Based Force Spectroscopy and Multiparametric Imaging of Biomolecular and Cellular Systems. Chem Rev 2020; 121:11701-11725. [PMID: 33166471 DOI: 10.1021/acs.chemrev.0c00617] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
During the last three decades, a series of key technological improvements turned atomic force microscopy (AFM) into a nanoscopic laboratory to directly observe and chemically characterize molecular and cell biological systems under physiological conditions. Here, we review key technological improvements that have established AFM as an analytical tool to observe and quantify native biological systems from the micro- to the nanoscale. Native biological systems include living tissues, cells, and cellular components such as single or complexed proteins, nucleic acids, lipids, or sugars. We showcase the procedures to customize nanoscopic chemical laboratories by functionalizing AFM tips and outline the advantages and limitations in applying different AFM modes to chemically image, sense, and manipulate biosystems at (sub)nanometer spatial and millisecond temporal resolution. We further discuss theoretical approaches to extract the kinetic and thermodynamic parameters of specific biomolecular interactions detected by AFM for single bonds and extend the discussion to multiple bonds. Finally, we highlight the potential of combining AFM with optical microscopy and spectroscopy to address the full complexity of biological systems and to tackle fundamental challenges in life sciences.
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Affiliation(s)
- Daniel J Müller
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 28, 4056 Basel, Switzerland
| | - Andra C Dumitru
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain (UCLouvain), Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium
| | - Cristina Lo Giudice
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain (UCLouvain), Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium
| | - Hermann E Gaub
- Applied Physics, Ludwig-Maximilians-Universität Munich, Amalienstrasse 54, 80799 München, Germany
| | - Peter Hinterdorfer
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics and Department of Physics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - James J De Yoreo
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States.,Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Yves F Dufrêne
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain (UCLouvain), Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium
| | - David Alsteens
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain (UCLouvain), Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium
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7
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Garcia R. Nanomechanical mapping of soft materials with the atomic force microscope: methods, theory and applications. Chem Soc Rev 2020; 49:5850-5884. [PMID: 32662499 DOI: 10.1039/d0cs00318b] [Citation(s) in RCA: 161] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Fast, high-resolution, non-destructive and quantitative characterization methods are needed to develop materials with tailored properties at the nanoscale or to understand the relationship between mechanical properties and cell physiology. This review introduces the state-of-the-art force microscope-based methods to map at high-spatial resolution the elastic and viscoelastic properties of soft materials. The experimental methods are explained in terms of the theories that enable the transformation of observables into material properties. Several applications in materials science, molecular biology and mechanobiology illustrate the scope, impact and potential of nanomechanical mapping methods.
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Affiliation(s)
- Ricardo Garcia
- Instituto de Ciencia de Materiales de Madrid, CSIC, c/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain.
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8
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Abstract
The bacterial cell envelope is essential for viability, the environmental gatekeeper and first line of defense against external stresses. For most bacteria, the envelope biosynthesis is also the site of action of some of the most important groups of antibiotics. It is a complex, often multicomponent structure, able to withstand the internally generated turgor pressure. Thus, elucidating the architecture and dynamics of the cell envelope is important, to unravel not only the complexities of cell morphology and maintenance of integrity but also how interventions such as antibiotics lead to death. To address these questions requires the capacity to visualize the cell envelope in situ via high-spatial resolution approaches. In recent years, atomic force microscopy (AFM) has brought novel molecular insights into the assembly, dynamics, and functions of bacterial cell envelopes. The ultrafine resolution and physical sensitivity of the technique have revealed a wealth of ultrastructural features that are invisible to traditional optical microscopy techniques or imperceptible in their true physiological state by electron microscopy. Here, we discuss recent progress in our use of AFM imaging for understanding the architecture and dynamics of the bacterial envelope. We survey recent studies that demonstrate the power of the technique to observe isolated membranes and live cells at (sub)nanometer resolution and under physiological conditions and to track in vitro structural dynamics in response to growth or to drugs.
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9
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Ritzmann N, Thoma J. Mechanical Unfolding and Refolding of Single Membrane Proteins by Atomic Force Microscopy. Methods Mol Biol 2020; 2127:359-372. [PMID: 32112333 DOI: 10.1007/978-1-0716-0373-4_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Atomic force microscopy (AFM)-based single-molecule force spectroscopy allows direct physical manipulation of single membrane proteins under near-physiological conditions. It can be applied to study mechanical properties and molecular interactions as well as unfolding and folding pathways of membrane proteins. Here, we describe the basic procedure to study membrane proteins by single-molecule force spectroscopy and discuss general requirements of the experimental setup as well as common pitfalls typically encountered when working with membrane proteins in AFM.
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Affiliation(s)
- Noah Ritzmann
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Basel, Switzerland
| | - Johannes Thoma
- Wallenberg Centre for Molecular and Translational Medicine, Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
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10
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Giliberti V, Polito R, Ritter E, Broser M, Hegemann P, Puskar L, Schade U, Zanetti-Polzi L, Daidone I, Corni S, Rusconi F, Biagioni P, Baldassarre L, Ortolani M. Tip-Enhanced Infrared Difference-Nanospectroscopy of the Proton Pump Activity of Bacteriorhodopsin in Single Purple Membrane Patches. NANO LETTERS 2019; 19:3104-3114. [PMID: 30950626 PMCID: PMC6745627 DOI: 10.1021/acs.nanolett.9b00512] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/02/2019] [Indexed: 05/21/2023]
Abstract
Photosensitive proteins embedded in the cell membrane (about 5 nm thickness) act as photoactivated proton pumps, ion gates, enzymes, or more generally, as initiators of stimuli for the cell activity. They are composed of a protein backbone and a covalently bound cofactor (e.g. the retinal chromophore in bacteriorhodopsin (BR), channelrhodopsin, and other opsins). The light-induced conformational changes of both the cofactor and the protein are at the basis of the physiological functions of photosensitive proteins. Despite the dramatic development of microscopy techniques, investigating conformational changes of proteins at the membrane monolayer level is still a big challenge. Techniques based on atomic force microscopy (AFM) can detect electric currents through protein monolayers and even molecular binding forces in single-protein molecules but not the conformational changes. For the latter, Fourier-transform infrared spectroscopy (FTIR) using difference-spectroscopy mode is typically employed, but it is performed on macroscopic liquid suspensions or thick films containing large amounts of purified photosensitive proteins. In this work, we develop AFM-assisted, tip-enhanced infrared difference-nanospectroscopy to investigate light-induced conformational changes of the bacteriorhodopsin mutant D96N in single submicrometric native purple membrane patches. We obtain a significant improvement compared with the signal-to-noise ratio of standard IR nanospectroscopy techniques by exploiting the field enhancement in the plasmonic nanogap that forms between a gold-coated AFM probe tip and an ultraflat gold surface, as further supported by electromagnetic and thermal simulations. IR difference-spectra in the 1450-1800 cm-1 range are recorded from individual patches as thin as 10 nm, with a diameter of less than 500 nm, well beyond the diffraction limit for FTIR microspectroscopy. We find clear spectroscopic evidence of a branching of the photocycle for BR molecules in direct contact with the gold surfaces, with equal amounts of proteins either following the standard proton-pump photocycle or being trapped in an intermediate state not directly contributing to light-induced proton transport. Our results are particularly relevant for BR-based optoelectronic and energy-harvesting devices, where BR molecular monolayers are put in contact with metal surfaces, and, more generally, for AFM-based IR spectroscopy studies of conformational changes of proteins embedded in intrinsically heterogeneous native cell membranes.
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Affiliation(s)
- Valeria Giliberti
- Istituto
Italiano di Tecnologia, Center for Life NanoScience, Viale Regina Elena 291, I-00161 Roma, Italy
- E-mail:
| | - Raffaella Polito
- Department
of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, I-00185 Roma, Italy
| | - Eglof Ritter
- Humboldt-Universität
zu Berlin, Institut für
Biologie, Invalidenstraße
42, D-10115 Berlin, Germany
| | - Matthias Broser
- Humboldt-Universität
zu Berlin, Institut für
Biologie, Invalidenstraße
42, D-10115 Berlin, Germany
| | - Peter Hegemann
- Humboldt-Universität
zu Berlin, Institut für
Biologie, Invalidenstraße
42, D-10115 Berlin, Germany
| | - Ljiljana Puskar
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - Ulrich Schade
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - Laura Zanetti-Polzi
- Department
of Physical and Chemical Sciences, University
of L’Aquila, Via Vetoio, I-67010 L’Aquila, Italy
| | - Isabella Daidone
- Department
of Physical and Chemical Sciences, University
of L’Aquila, Via Vetoio, I-67010 L’Aquila, Italy
| | - Stefano Corni
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy
- CNR
Institute
of Nanoscience, Via Campi
213/A, I-41125 Modena, Italy
| | - Francesco Rusconi
- Dipartimento
di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Paolo Biagioni
- Dipartimento
di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Leonetta Baldassarre
- Department
of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, I-00185 Roma, Italy
| | - Michele Ortolani
- Istituto
Italiano di Tecnologia, Center for Life NanoScience, Viale Regina Elena 291, I-00161 Roma, Italy
- Department
of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, I-00185 Roma, Italy
- E-mail:
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11
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Pick H, Alves AC, Vogel H. Single-Vesicle Assays Using Liposomes and Cell-Derived Vesicles: From Modeling Complex Membrane Processes to Synthetic Biology and Biomedical Applications. Chem Rev 2018; 118:8598-8654. [PMID: 30153012 DOI: 10.1021/acs.chemrev.7b00777] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The plasma membrane is of central importance for defining the closed volume of cells in contradistinction to the extracellular environment. The plasma membrane not only serves as a boundary, but it also mediates the exchange of physical and chemical information between the cell and its environment in order to maintain intra- and intercellular functions. Artificial lipid- and cell-derived membrane vesicles have been used as closed-volume containers, representing the simplest cell model systems to study transmembrane processes and intracellular biochemistry. Classical examples are studies of membrane translocation processes in plasma membrane vesicles and proteoliposomes mediated by transport proteins and ion channels. Liposomes and native membrane vesicles are widely used as model membranes for investigating the binding and bilayer insertion of proteins, the structure and function of membrane proteins, the intramembrane composition and distribution of lipids and proteins, and the intermembrane interactions during exo- and endocytosis. In addition, natural cell-released microvesicles have gained importance for early detection of diseases and for their use as nanoreactors and minimal protocells. Yet, in most studies, ensembles of vesicles have been employed. More recently, new micro- and nanotechnological tools as well as novel developments in both optical and electron microscopy have allowed the isolation and investigation of individual (sub)micrometer-sized vesicles. Such single-vesicle experiments have revealed large heterogeneities in the structure and function of membrane components of single vesicles, which were hidden in ensemble studies. These results have opened enormous possibilities for bioanalysis and biotechnological applications involving unprecedented miniaturization at the nanometer and attoliter range. This review will cover important developments toward single-vesicle analysis and the central discoveries made in this exciting field of research.
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Affiliation(s)
- Horst Pick
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Ana Catarina Alves
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Horst Vogel
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
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12
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Giliberti V, Badioli M, Nucara A, Calvani P, Ritter E, Puskar L, Aziz EF, Hegemann P, Schade U, Ortolani M, Baldassarre L. Heterogeneity of the Transmembrane Protein Conformation in Purple Membranes Identified by Infrared Nanospectroscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1701181. [PMID: 28960799 DOI: 10.1002/smll.201701181] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/02/2017] [Indexed: 06/07/2023]
Abstract
Cell membranes are intrinsically heterogeneous, as the local protein and lipid distribution is critical to physiological processes. Even in template systems embedding a single protein type, like purple membranes, there can be a different local response to external stimuli or environmental factors, resulting in heterogeneous conformational changes. Despite the dramatic advances of microspectroscopy techniques, the identification of the conformation heterogeneity is still a challenging task. Tip-enhanced infrared nanospectroscopy is here used to identify conformational changes connected to the hydration state of the transmembrane proteins contained in a 50 nm diameter cell membrane area, without the need for fluorescent labels. In dried purple membrane monolayers, areas with fully hydrated proteins are found among large numbers of molecules with randomly distributed hydration states. Infrared nanospectroscopy results are compared to the spectra obtained with diffraction-limited infrared techniques based on the use of synchrotron radiation, in which the diffraction limit still prevents the observation of nanoscale heterogeneity.
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Affiliation(s)
- Valeria Giliberti
- Istituto Italiano di Tecnologia, Center for Life NanoScience, Viale Regina Elena 291, I-00161, Roma, Italy
| | - Michela Badioli
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185, Roma, Italy
| | - Alessandro Nucara
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185, Roma, Italy
| | - Paolo Calvani
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185, Roma, Italy
| | - Eglof Ritter
- Humboldt-Universität zu Berlin, Institut für Biologie, Invalidenstraße 42, D-10115, Berlin, Germany
| | - Ljiljana Puskar
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Emad Flear Aziz
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Peter Hegemann
- Humboldt-Universität zu Berlin, Institut für Biologie, Invalidenstraße 42, D-10115, Berlin, Germany
| | - Ulrich Schade
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Michele Ortolani
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185, Roma, Italy
| | - Leonetta Baldassarre
- Istituto Italiano di Tecnologia, Center for Life NanoScience, Viale Regina Elena 291, I-00161, Roma, Italy
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185, Roma, Italy
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13
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Recent advances in biophysical studies of rhodopsins - Oligomerization, folding, and structure. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1512-1521. [PMID: 28844743 DOI: 10.1016/j.bbapap.2017.08.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 08/06/2017] [Accepted: 08/11/2017] [Indexed: 12/19/2022]
Abstract
Retinal-binding proteins, mainly known as rhodopsins, function as photosensors and ion transporters in a wide range of organisms. From halobacterial light-driven proton pump, bacteriorhodopsin, to bovine photoreceptor, visual rhodopsin, they have served as prototypical α-helical membrane proteins in a large number of biophysical studies and aided in the development of many cutting-edge techniques of structural biology and biospectroscopy. In the last decade, microbial and animal rhodopsin families have expanded significantly, bringing into play a number of new interesting structures and functions. In this review, we will discuss recent advances in biophysical approaches to retinal-binding proteins, primarily microbial rhodopsins, including those in optical spectroscopy, X-ray crystallography, nuclear magnetic resonance, and electron paramagnetic resonance, as applied to such fundamental biological aspects as protein oligomerization, folding, and structure.
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14
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Ikai A, Afrin R, Saito M, Watanabe-Nakayama T. Atomic force microscope as a nano- and micrometer scale biological manipulator: A short review. Semin Cell Dev Biol 2017; 73:132-144. [PMID: 28739341 DOI: 10.1016/j.semcdb.2017.07.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 07/16/2017] [Accepted: 07/19/2017] [Indexed: 11/27/2022]
Abstract
The amazing capacity of atomic force microscope to let us touch the molecular and cellular level samples with a sharp probe stimulated its application to bio-medical field among others. In addition to topographical imaging of the sample surface, a direct mechanical manipulation has attracted innovative minds to develop new methodologies aiming at direct handling of proteins, DNA/RNA, and cells. Measurement of their mechanical properties brought about a vivid picture of their physical nature. Direct handling of individual molecules and cells prompted development of nano-medical applications. This short review summarized recent application of AFM for measurement of mechanical properties of biological samples and attempts to perform direct manipulations of nano-medicine.
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Affiliation(s)
- Atsushi Ikai
- Innovation Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
| | - Rehana Afrin
- Innovation Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
| | - Masakazu Saito
- Innovation Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
| | - Takahiro Watanabe-Nakayama
- Innovation Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
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15
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Pfreundschuh M, Harder D, Ucurum Z, Fotiadis D, Müller DJ. Detecting Ligand-Binding Events and Free Energy Landscape while Imaging Membrane Receptors at Subnanometer Resolution. NANO LETTERS 2017; 17:3261-3269. [PMID: 28361535 DOI: 10.1021/acs.nanolett.7b00941] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Force-distance curve-based atomic force microscopy has emerged into a sophisticated technique for imaging cellular membranes and for detecting specific ligand-binding events of native membrane receptors. However, so far the resolution achieved has been insufficient to structurally map ligand-binding sites onto membrane proteins. Here, we introduce experimental and theoretical approaches for overcoming this limitation. To establish a structurally and functionally well-defined reference sample, we engineer a ligand-binding site to the light-driven proton pump bacteriorhodopsin of purple membrane. Functionalizing the AFM stylus with an appropriate linker-system tethering the ligand and optimizing the AFM conditions allows for imaging the engineered bacteriorhodopsin at subnanometer resolution while structurally mapping the specific ligand-receptor binding events. Improved data analysis allows reconstructing the ligand-binding free energy landscape from the experimental data, thus providing thermodynamic and kinetic insight into the ligand-binding process. The nanoscopic method introduced is generally applicable for imaging receptors in native membranes at subnanometer resolution and for systematically mapping and quantifying the free energy landscape of ligand binding.
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Affiliation(s)
- Moritz Pfreundschuh
- Department of Biosystems Science and Engineering, ETH Zürich , 4058 Basel, Switzerland
| | - Daniel Harder
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Zöhre Ucurum
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Dimitrios Fotiadis
- Institute of Biochemistry and Molecular Medicine, University of Bern , 3012 Bern, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zürich , 4058 Basel, Switzerland
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16
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Abdelwahab MT, Kalyoncu E, Onur T, Baykara MZ, Seker UOS. Genetically-Tunable Mechanical Properties of Bacterial Functional Amyloid Nanofibers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4337-4345. [PMID: 28388843 DOI: 10.1021/acs.langmuir.7b00112] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Bacterial biofilms are highly ordered, complex, dynamic material systems including cells, carbohydrates, and proteins. They are known to be resistant against chemical, physical, and biological disturbances. These superior properties make them promising candidates for next generation biomaterials. Here we investigated the morphological and mechanical properties (in terms of Young's modulus) of genetically-engineered bacterial amyloid nanofibers of Escherichia coli (E. coli) by imaging and force spectroscopy conducted via atomic force microscopy (AFM). In particular, we tuned the expression and biochemical properties of the major and minor biofilm proteins of E. coli (CsgA and CsgB, respectively). Using appropriate mutants, amyloid nanofibers constituting biofilm backbones are formed with different combinations of CsgA and CsgB, as well as the optional addition of tagging sequences. AFM imaging and force spectroscopy are used to probe the morphology and measure the Young's moduli of biofilm protein nanofibers as a function of protein composition. The obtained results reveal that genetically-controlled secretion of biofilm protein components may lead to the rational tuning of Young's moduli of biofilms as promising candidates at the bionano interface.
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Affiliation(s)
- M Tarek Abdelwahab
- Department of Mechanical Engineering, Bilkent University , Ankara 06800, Turkey
- Institute of Materials Science and Nanotechnology, Bilkent University , Ankara 06800, Turkey
- National Nanotechnology Research Center (UNAM), Bilkent University , Ankara 06800, Turkey
| | - Ebuzer Kalyoncu
- Institute of Materials Science and Nanotechnology, Bilkent University , Ankara 06800, Turkey
- National Nanotechnology Research Center (UNAM), Bilkent University , Ankara 06800, Turkey
| | - Tugce Onur
- Institute of Materials Science and Nanotechnology, Bilkent University , Ankara 06800, Turkey
- National Nanotechnology Research Center (UNAM), Bilkent University , Ankara 06800, Turkey
| | - Mehmet Z Baykara
- Department of Mechanical Engineering, Bilkent University , Ankara 06800, Turkey
- Institute of Materials Science and Nanotechnology, Bilkent University , Ankara 06800, Turkey
- National Nanotechnology Research Center (UNAM), Bilkent University , Ankara 06800, Turkey
| | - Urartu Ozgur Safak Seker
- Institute of Materials Science and Nanotechnology, Bilkent University , Ankara 06800, Turkey
- National Nanotechnology Research Center (UNAM), Bilkent University , Ankara 06800, Turkey
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17
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Kato HE, Inoue K, Kandori H, Nureki O. The light-driven sodium ion pump: A new player in rhodopsin research. Bioessays 2016; 38:1274-1282. [PMID: 27859420 DOI: 10.1002/bies.201600065] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Rhodopsins are one of the most studied photoreceptor protein families, and ion-translocating rhodopsins, both pumps and channels, have recently attracted broad attention because of the development of optogenetics. Recently, a new functional class of ion-pumping rhodopsins, an outward Na+ pump, was discovered, and following structural and functional studies enable us to compare three functionally different ion-pumping rhodopsins: outward proton pump, inward Cl- pump, and outward Na+ pump. Here, we review the current knowledge on structure-function relationships in these three light-driven pumps, mainly focusing on Na+ pumps. A structural and functional comparison reveals both unique and conserved features of these ion pumps, and enhances our understanding about how the structurally similar microbial rhodopsins acquired such diverse functions. We also discuss some unresolved questions and future perspectives in research of ion-pumping rhodopsins, including optogenetics application and engineering of novel rhodopsins.
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Affiliation(s)
- Hideaki E Kato
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Keiichi Inoue
- Department of Frontier Materials, Nagoya Institute of Technology, Nagoya, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Nagoya, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
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18
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Grebikova L, Radiom M, Maroni P, Schlüter AD, Borkovec M. Recording stretching response of single polymer chains adsorbed on solid substrates. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.02.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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19
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Lazarova T, Mlynarczyk K, Querol E, Tenchov B, Filipek S, Padrós E. Identification of Specific Effect of Chloride on the Spectral Properties and Structural Stability of Multiple Extracellular Glutamic Acid Mutants of Bacteriorhodopsin. PLoS One 2016; 11:e0162952. [PMID: 27657718 PMCID: PMC5033488 DOI: 10.1371/journal.pone.0162952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/31/2016] [Indexed: 11/18/2022] Open
Abstract
In the present work we combine spectroscopic, DSC and computational approaches to examine the multiple extracellular Glu mutants E204Q/E194Q, E204Q/E194Q/E9Q and E204Q/E194Q/E9Q/E74Q of bacteriorhodopsin by varying solvent ionic strength and composition. Absorption spectroscopy data reveal that the absorption maxima of multiple EC Glu mutants can be tuned by the chloride concentration in the solution. Visible Circular dichroism spectra imply that the specific binding of Cl- can modulate weakened exciton chromophore coupling and reestablish wild type-like bilobe spectral features of the mutants. The DSC data display reappearance of the reversible thermal transition, higher Tm of denaturation and an increase in the enthalpy of unfolding of the mutants in 1 M KCl solutions. Molecular dynamics simulations indicate high affinity binding of Cl- to Arg82 and to Gln204 and Gln194 residues in the mutants. Analysis of the experimental data suggests that simultaneous elimination of the negatively charged side chain of Glu194 and Glu204 is the major cause for mutants' alterations. Specific Cl- binding efficiently coordinates distorted hydrogen bonding interactions of the EC region and reconstitutes the conformation and structure stability of mutated bR in WT-like fashion.
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Affiliation(s)
- Tzvetana Lazarova
- Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Barcelona, Spain
- * E-mail: (TL); (EP)
| | - Krzysztof Mlynarczyk
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Enric Querol
- Institut de Biomedicina i Biotecnologia, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Boris Tenchov
- Department of Medical Physics and Biophysics, Faculty of Medicine, Medical University – Sofia, Sofia, Bulgaria
| | - Slawomir Filipek
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Esteve Padrós
- Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Barcelona, Spain
- * E-mail: (TL); (EP)
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20
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Enhanced photocurrent generation in bacteriorhodopsin based bio-sensitized solar cells using gel electrolyte. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2016; 162:208-212. [DOI: 10.1016/j.jphotobiol.2016.06.044] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/25/2016] [Indexed: 11/17/2022]
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21
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Mashaghi A, Mashaghi S, Reviakine I, Heeren RMA, Sandoghdar V, Bonn M. Label-free characterization of biomembranes: from structure to dynamics. Chem Soc Rev 2014; 43:887-900. [PMID: 24253187 DOI: 10.1039/c3cs60243e] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We review recent progress in the study of the structure and dynamics of phospholipid membranes and associated proteins, using novel label-free analytical tools. We describe these techniques and illustrate them with examples highlighting current capabilities and limitations. Recent advances in applying such techniques to biological and model membranes for biophysical studies and biosensing applications are presented, and future prospects are discussed.
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Affiliation(s)
- Alireza Mashaghi
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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22
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David R, Erdmann M, Fornof AR, Gaub HE. Functionalization of cantilever tips with nucleotides by the phosphoramidite method. ChemMedChem 2014; 9:2049-51. [PMID: 25130700 DOI: 10.1002/cmdc.201402165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 07/29/2014] [Indexed: 11/10/2022]
Abstract
In atomic force microscopy (AFM) a sharp cantilever tip is used to scan surfaces at the atomic level. One further application is force spectroscopy, in which force-distance curves between binding partners located on the cantilever and substrate surface are determined. This requires specifically immobilized molecules. Herein we describe the covalent binding of single adenosine and thymidine nucleotides on an amino-PEGylated cantilever tip by the phosphoramidite method. Force-distance curves between these cantilever tips and gold surfaces were recorded. The rupture forces of the coordination bond between the primary amine of adenosine and the undercoordinated gold atoms were determined to be 145 pN, which is in agreement with previously published data. The force-distance curves of thymidine-functionalized tips did not show rupture events, because this nucleotide does not possess a primary amine function. Nucleotide-functionalized tips could aid in the understanding of binding mechanisms of nucleotide binding molecules such as polymerases immobilized on surfaces or membranes.
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Affiliation(s)
- Ralf David
- Chair for Applied Physics and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 81677 München (Germany), Fax: +49 (0) 89/2180-2050.
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23
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Pfreundschuh M, Martinez-Martin D, Mulvihill E, Wegmann S, Muller DJ. Multiparametric high-resolution imaging of native proteins by force-distance curve–based AFM. Nat Protoc 2014; 9:1113-30. [DOI: 10.1038/nprot.2014.070] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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24
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Ando T, Uchihashi T, Scheuring S. Filming biomolecular processes by high-speed atomic force microscopy. Chem Rev 2014; 114:3120-88. [PMID: 24476364 PMCID: PMC4076042 DOI: 10.1021/cr4003837] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Toshio Ando
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Takayuki Uchihashi
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Simon Scheuring
- U1006
INSERM/Aix-Marseille Université, Parc Scientifique et Technologique
de Luminy Bâtiment Inserm TPR2 bloc 5, 163 avenue de Luminy, 13288 Marseille Cedex 9, France
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25
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Medalsy ID, Müller DJ. Nanomechanical properties of proteins and membranes depend on loading rate and electrostatic interactions. ACS NANO 2013; 7:2642-2650. [PMID: 23442147 DOI: 10.1021/nn400015z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Knowing the dynamic mechanical response of tissue, cells, membranes, proteins, nucleic acids, and carbohydrates to external perturbations is important to understand various biological and biotechnological problems. Atomic force microscopy (AFM)-based approaches are the most frequently used nanotechnologies to determine the mechanical properties of biological samples that range in size from microscopic to (sub)nanoscopic. However, the dynamic nature of biomechanical properties has barely been addressed by AFM imaging. In this work, we characterizethe viscoelastic properties of the native light-driven proton pump bacteriorhodopsin of the purple membrane of Halobacterium salinarum. Using force-distance curve (F-D)-based AFM we imaged purple membranes while force probing their mechanical response over a wide range of loading rates (from ∼0.5 to 100 μN/s). Our results show that the mechanical stiffness of protein and membrane increases with the loading rate up to a factor of 10 (from ∼0.3 to 3.2 N/m). In addition, the electrostatic repulsion between AFM tip and sample can alter the mechanical stiffness measured by AFM up to ∼60% (from ∼0.8 to 1.3 N/m).These findings indicate that the mechanical response of membranes and proteins and probably of other biomolecular systems should be determined at different loading rates to fully understand their properties.
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Affiliation(s)
- Izhar D Medalsy
- Department of Biosystems Science and Engineering, ETH Zurich, CH-4058 Basel, Switzerland
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26
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Erickson BW, Coquoz S, Adams JD, Burns DJ, Fantner GE. Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2012; 3:747-758. [PMID: 23213638 PMCID: PMC3512124 DOI: 10.3762/bjnano.3.84] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 10/08/2012] [Indexed: 05/27/2023]
Abstract
Modern high-speed atomic force microscopes generate significant quantities of data in a short amount of time. Each image in the sequence has to be processed quickly and accurately in order to obtain a true representation of the sample and its changes over time. This paper presents an automated, adaptive algorithm for the required processing of AFM images. The algorithm adaptively corrects for both common one-dimensional distortions as well as the most common two-dimensional distortions. This method uses an iterative thresholded processing algorithm for rapid and accurate separation of background and surface topography. This separation prevents artificial bias from topographic features and ensures the best possible coherence between the different images in a sequence. This method is equally applicable to all channels of AFM data, and can process images in seconds.
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Affiliation(s)
- Blake W Erickson
- Laboratory for Bio- and Nano-Instrumentation, École Polytechnique Fédérale de Lausanne, Batiment BM 3109 Station 17, 1015 Lausanne, Switzerland
| | - Séverine Coquoz
- Laboratory for Bio- and Nano-Instrumentation, École Polytechnique Fédérale de Lausanne, Batiment BM 3109 Station 17, 1015 Lausanne, Switzerland
| | - Jonathan D Adams
- Laboratory for Bio- and Nano-Instrumentation, École Polytechnique Fédérale de Lausanne, Batiment BM 3109 Station 17, 1015 Lausanne, Switzerland
| | - Daniel J Burns
- Mechatronics Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States of America
| | - Georg E Fantner
- Laboratory for Bio- and Nano-Instrumentation, École Polytechnique Fédérale de Lausanne, Batiment BM 3109 Station 17, 1015 Lausanne, Switzerland
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27
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Andreopoulos B, Labudde D. Efficient unfolding pattern recognition in single molecule force spectroscopy data. Algorithms Mol Biol 2011; 6:16. [PMID: 21645400 PMCID: PMC3126767 DOI: 10.1186/1748-7188-6-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 06/06/2011] [Indexed: 11/20/2022] Open
Abstract
Background Single-molecule force spectroscopy (SMFS) is a technique that measures the force necessary to unfold a protein. SMFS experiments generate Force-Distance (F-D) curves. A statistical analysis of a set of F-D curves reveals different unfolding pathways. Information on protein structure, conformation, functional states, and inter- and intra-molecular interactions can be derived. Results In the present work, we propose a pattern recognition algorithm and apply our algorithm to datasets from SMFS experiments on the membrane protein bacterioRhodopsin (bR). We discuss the unfolding pathways found in bR, which are characterised by main peaks and side peaks. A main peak is the result of the pairwise unfolding of the transmembrane helices. In contrast, a side peak is an unfolding event in the alpha-helix or other secondary structural element. The algorithm is capable of detecting side peaks along with main peaks. Therefore, we can detect the individual unfolding pathway as the sequence of events labeled with their occurrences and co-occurrences special to bR's unfolding pathway. We find that side peaks do not co-occur with one another in curves as frequently as main peaks do, which may imply a synergistic effect occurring between helices. While main peaks co-occur as pairs in at least 50% of curves, the side peaks co-occur with one another in less than 10% of curves. Moreover, the algorithm runtime scales well as the dataset size increases. Conclusions Our algorithm satisfies the requirements of an automated methodology that combines high accuracy with efficiency in analyzing SMFS datasets. The algorithm tackles the force spectroscopy analysis bottleneck leading to more consistent and reproducible results.
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28
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Last JA, Russell P, Nealey PF, Murphy CJ. The applications of atomic force microscopy to vision science. Invest Ophthalmol Vis Sci 2011; 51:6083-94. [PMID: 21123767 DOI: 10.1167/iovs.10-5470] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The atomic force microscope (AFM) is widely used in materials science and has found many applications in biological sciences but has been limited in use in vision science. The AFM can be used to image the topography of soft biological materials in their native environments. It can also be used to probe the mechanical properties of cells and extracellular matrices, including their intrinsic elastic modulus and receptor-ligand interactions. In this review, the operation of the AFM is described along with a review of how it has been thus far used in vision science. It is hoped that this review will serve to stimulate vision scientists to consider incorporating AFM as part of their research toolkit.
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Affiliation(s)
- Julie A Last
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
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29
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Suzuki Y, Yokokawa M, Yoshimura SH, Takeyasu K. Biological Application of Fast-Scanning Atomic Force Microscopy. SCANNING PROBE MICROSCOPY IN NANOSCIENCE AND NANOTECHNOLOGY 2 2011. [DOI: 10.1007/978-3-642-10497-8_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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30
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Schranz M, Baumann RP, Rhinow D, Hampp N. Dynamics of bacteriorhodopsin in solid-supported purple membranes studied with tapping-mode atomic force microscopy. J Phys Chem B 2010; 114:9047-53. [PMID: 20509702 DOI: 10.1021/jp102377c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Purple membrane (PM) from Halobacterium salinarum, which comprises bacteriorhodopsin (BR) and lipids only, has been employed by many groups as a model system to study the structure and dynamics of membrane proteins. Although the conformational dynamics of BR within PM has been extensively analyzed with subnanometer resolution by means of diffraction experiments and spectroscopic methods, as well, structural studies of dynamical transitions within single PMs are rare. In this work, we show that tapping-mode atomic force microscopy (TM-AFM) is ideally suited to study dynamical transitions within solid-supported PMs at the nanoscale. Time-dependent AFM analysis of solid-supported PMs shows that redistribution processes take place between a crystalline core region, featuring a height of approximately 5 nm, and a highly mobile rim region (approximately 4 nm in height). Furthermore, we discuss the influence of temperature and substrate on the equilibrium. The experiments are complemented by electrostatic force microscopy (EFM) of PM on mica. Beyond their importance for many physiological processes, dynamical transitions in biological membranes, as observed in this work, are of critical importance for all methods that make use of solid-supported membrane assemblies, either analytical tools or applications.
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Affiliation(s)
- Michael Schranz
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Strasse Building H, D-35032 Marburg, Germany
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31
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Shibata M, Yamashita H, Uchihashi T, Kandori H, Ando T. High-speed atomic force microscopy shows dynamic molecular processes in photoactivated bacteriorhodopsin. NATURE NANOTECHNOLOGY 2010; 5:208-12. [PMID: 20154686 DOI: 10.1038/nnano.2010.7] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 01/08/2010] [Indexed: 05/24/2023]
Abstract
Dynamic changes in protein conformation in response to external stimuli are important in biological processes, but it has proved difficult to directly visualize such structural changes under physiological conditions. Here, we show that high-speed atomic force microscopy can be used to visualize dynamic changes in stimulated proteins. High-resolution movies of a light-driven proton pump, bacteriorhodopsin, reveal that, upon illumination, a cytoplasmic portion of each bacteriorhodopsin monomer is brought into contact with adjacent trimers. The bacteriorhodopsin-bacteriorhodopsin interaction in the transiently formed assembly engenders both positive and negative cooperative effects in the decay kinetics as the initial bacteriorhodopsin recovers and, as a consequence, the turnover rate of the photocycle is maintained constant, on average, irrespective of the light intensity. These results confirm that high-resolution visualization is a powerful approach for studying elaborate biomolecular processes under realistic conditions.
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Affiliation(s)
- Mikihiro Shibata
- Department of Physics, Kanazawa University, Kanazawa 920-1192, Japan
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32
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Antoranz Contera S, Voïtchovsky K, Ryan JF. Controlled ionic condensation at the surface of a native extremophile membrane. NANOSCALE 2010; 2:222-229. [PMID: 20644798 DOI: 10.1039/b9nr00248k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
At the nanoscale level biological membranes present a complex interface with the solvent. The functional dynamics and relative flexibility of membrane components together with the presence of specific ionic effects can combine to create exciting new phenomena that challenge traditional theories such as the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or models interpreting the role of ions in terms of their ability to structure water (structure making/breaking). Here we investigate ionic effects at the surface of a highly charged extremophile membrane composed of a proton pump (bacteriorhodopsin) and archaeal lipids naturally assembled into a 2D crystal. Using amplitude-modulation atomic force microscopy (AM-AFM) in solution, we obtained sub-molecular resolution images of ion-induced surface restructuring of the membrane. We demonstrate the presence of a stiff cationic layer condensed at its extracellular surface. This layer cannot be explained by traditional continuum theories. Dynamic force spectroscopy experiments suggest that it is produced by electrostatic correlation mediated by a Manning-type condensation of ions. In contrast, the cytoplasmic surface is dominated by short-range repulsive hydration forces. These findings are relevant to archaeal bioenergetics and halophilic adaptation. Importantly, they present experimental evidence of a natural system that locally controls its interactions with the surrounding medium and challenges our current understanding of biological interfaces.
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Affiliation(s)
- Sonia Antoranz Contera
- University of Oxford, Bionanotechnology IRC, Clarendon Laboratory, Physics Department, Parks Road, OX1 3PU, Oxford, UK.
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33
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Ikai A. A review on: atomic force microscopy applied to nano-mechanics of the cell. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2010; 119:47-61. [PMID: 19343307 DOI: 10.1007/10_2008_41] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Since its introduction in 1986, AFM has been applied to biological studies along with its widespread use in physics, chemistry and engineering fields. Due to its dual capabilities of imaging nano-materials with an atomic level resolution and of directly manipulating samples with high precision, AFM is now considered an indispensable instrument for nano-technological researchers especially in physically oriented fields. In biology in general, however, and in biotechnology in particular, its usefulness must be critically examined and, if necessary as it certainly is, further explored from a practical point of view. In this review, a new trend of applying AFM based technology to elucidate the mechanical basis of the cellular structure and its interaction with the extracellular matrix including cell to cell interaction is reviewed. Some of the recent studies done by using other force measuring or force exerting methods are also covered in the hope that all the nano-mechanical work on the cellular level will eventually contribute to the emergence of the mechano-chemical view of the cell in a unified manner.
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Affiliation(s)
- Atsushi Ikai
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan,
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34
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Casuso I, Kodera N, Le Grimellec C, Ando T, Scheuring S. Contact-mode high-resolution high-speed atomic force microscopy movies of the purple membrane. Biophys J 2009; 97:1354-61. [PMID: 19720023 DOI: 10.1016/j.bpj.2009.06.019] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 06/08/2009] [Accepted: 06/15/2009] [Indexed: 11/16/2022] Open
Abstract
High-speed atomic force microscopy (HS-AFM) is becoming a reference tool for the study of dynamic biological processes. The spatial and time resolutions of HS-AFM are on the order of nanometers and milliseconds, respectively, and allow structural and functional characterization of biological processes at the single-molecule level. In this work we present contact-mode HS-AFM movies of purple membranes containing two-dimensional arrays of bacteriorhodopsin (bR). In high-resolution movies acquired at a 100 ms frame acquisition time, the substructure on individual bR trimers was visualized. In regions in between different bR arrays, dynamic topographies were observed and interpreted as motion of the bR trimers. Similarly, motion of bR monomers in the vicinity of lattice defects in the purple membrane was observed. Our findings indicate that the bR arrays are in a mobile association-dissociation equilibrium. HS-AFM on membranes provides novel perspectives for analyzing the membrane diffusion processes of nonlabeled molecules.
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Affiliation(s)
- Ignacio Casuso
- Institut Curie, Equipe Institut National de la Sante et de la Recherche Médicale Avenir, Unite Mixte de Recherche 168-Centre National de la Recherche Scientifique, Paris, France
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35
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Scheuring S, Sturgis JN. Atomic force microscopy of the bacterial photosynthetic apparatus: plain pictures of an elaborate machinery. PHOTOSYNTHESIS RESEARCH 2009; 102:197-211. [PMID: 19266309 DOI: 10.1007/s11120-009-9413-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 02/10/2009] [Indexed: 05/27/2023]
Abstract
Photosynthesis both in the past and present provides the vast majority of the energy used on the planet. The purple photosynthetic bacteria are a group of organisms that are able to perform photosynthesis using a particularly simple system that has been much studied. The main molecular constituents required for photosynthesis in these organisms are a small number of transmembrane pigment-protein complexes. These are able to function together with a high quantum efficiency (about 95%) to convert light energy into chemical potential energy. While the structure of the various proteins have been solved for several years, direct studies of the supramolecular assembly of these complexes in native membranes needed maturity of the atomic force microscope (AFM). Here, we review the novel findings and the direct conclusions that could be drawn from high-resolution AFM analysis of photosynthetic membranes. These conclusions rely on the possibility that the AFM brings of obtaining molecular resolution images of large membrane areas and thereby bridging the resolution gap between atomic structures and cellular ultrastructure.
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Affiliation(s)
- Simon Scheuring
- Institut Curie, UMR168-CNRS, 26 Rue d’Ulm, 75248 Paris, France.
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36
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Palmer AR, Rosen S. British Society of Audiology Short Papers Meeting on Experimental Studies of Hearing and Deafness. Int J Audiol 2009. [DOI: 10.3109/14992020209078336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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37
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Kodama T, Koyanagi T, Sekiguchi H, Ikai A, Ohtani H. Unfolding study of native bacteriorhodopsin under acidic condition. Ultramicroscopy 2009; 109:948-51. [DOI: 10.1016/j.ultramic.2009.03.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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38
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Xiang Y, Yang M, Su T, Chen Y, Bi L, Hu K. Glycolipid Biotinylation on Purple Membrane with Maintained Bioactivity. J Phys Chem B 2009; 113:7762-6. [DOI: 10.1021/jp901416j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yan Xiang
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
| | - Meng Yang
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
| | - Tao Su
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
| | - Yuanyuan Chen
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
| | - Lijun Bi
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
| | - Kunsheng Hu
- School of Chemistry and Environment, Beihang University, Beijing, P. R. China 100191, School of Materials Science and Engineering, Beihang University, Beijing, P. R. China 100191, and Institute of Biophysics, Chinese Academy of Sciences, Beijing, P. R. China 100101
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39
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Saab MB, Estephan E, Cloitre T, Legros R, Cuisinier FJG, Zimányi L, Gergely C. Assembly of purple membranes on polyelectrolyte films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:5159-5167. [PMID: 19397356 DOI: 10.1021/la9002274] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The membrane protein bacteriorhodopsin in its native membrane bound form (purple membrane) was adsorbed and incorporated into polyelectrolyte multilayered films, and adsorption was in situ monitored by optical waveguide light-mode spectroscopy. The formation of a single layer or a double layer of purple membranes was observed when adsorbed on negatively or positively charged surfaces, respectively. The purple membrane patches adsorbed on the polyelectrolyte multilayers were also evidenced by atomic force microscopy images. The driving forces of the adsorption process were evaluated by varying the ionic strength of the solution as well as the purple membrane concentration. At high purple membrane concentration, interpenetrating polyelectrolyte loops might provide new binding sites for the adsorption of a second layer of purple membranes, whereas at lower concentrations only a single layer is formed. Negative surfaces do not promote a second protein layer adsorption. Driving forces other than just electrostatic ones, such as hydrophobic forces, should play a role in the polyelectrolyte/purple membrane layering. The subtle interplay of all these factors determines the formation of the polyelectrolyte/purple membrane matrix with a presumably high degree of orientation for the incorporated purple membranes, with their cytoplasmic, or extracellular side toward the bulk on negatively or positively charged polyelectrolyte, respectively. The structural stability of bacteriorhodopsin during adsorption onto the surface and incorporation into the polyelectrolyte multilayers was investigated by Fourier transform infrared spectroscopy in attenuated total reflection mode. Adsorption and incorporation of purple membranes within polyelectrolyte multilayers does not disturb the conformational majority of membrane-embedded alpha-helix structures of the protein, but may slightly alter the structure of the extramembraneous segments or their interaction with the environment. This high stability is different from the lower stability of the predominantly beta-sheet structures of numerous globular proteins when adsorbed onto surfaces.
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Affiliation(s)
- Marie-belle Saab
- Groupe d'Etude des Semi-conducteurs, UMR 5650, CNRS-Universite Montpellier II, 34095, Montpellier Cedex 5, France
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40
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Xu X, Melcher J, Basak S, Reifenberger R, Raman A. Compositional contrast of biological materials in liquids using the momentary excitation of higher eigenmodes in dynamic atomic force microscopy. PHYSICAL REVIEW LETTERS 2009; 102:060801. [PMID: 19257574 DOI: 10.1103/physrevlett.102.060801] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Revised: 01/04/2009] [Indexed: 05/21/2023]
Abstract
Atomic Force microscope (AFM) cantilevers commonly used for imaging soft biological samples in liquids experience a momentary excitation of the higher eigenmodes at each tap. This transient response is very sensitive to the local sample elasticity under gentle imaging conditions because the higher eigenmode time period is comparable to the tip-sample contact time. By mapping the momentary excitation response, we demonstrate a new scanning probe spectroscopy capable of resolving with high sensitivity the variations in the elasticity of soft biological materials in liquids.
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Affiliation(s)
- Xin Xu
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA
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41
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Abstract
The atomic force microscope (AFM) is an important tool for studying biological samples due to its ability to image surfaces under liquids. The AFM operates by physical interaction of a cantilever tip with the molecules on the cell surface. Adhesion forces between the tip and cell surface molecules are detected as cantilever deflections. Thus, the cantilever tip can be used to image live cells with atomic resolution and to probe single molecular events in living cells under physiological conditions. Currently, this is the only technique available that directly provides structural, mechanical, and functional information at high resolution. This unit presents the basic AFM components, modes of operation, useful tips for sample preparation, and a short review of AFM applications in microbiology.
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Affiliation(s)
- Andreea Trache
- Department of Systems Biology & Translational Medicine, College of Medicine, Texas A&M Health Science Center, College Station, Texas, USA
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42
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Strategies to prepare and characterize native membrane proteins and protein membranes by AFM. Curr Opin Colloid Interface Sci 2008. [DOI: 10.1016/j.cocis.2007.09.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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43
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Laflamme E, Badia A, Lafleur M, Schwartz JL, Laprade R. Atomic Force Microscopy Imaging of Bacillus thuringiensis Cry1 Toxins Interacting with Insect Midgut Apical Membranes. J Membr Biol 2008; 222:127-39. [DOI: 10.1007/s00232-008-9106-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 03/23/2008] [Indexed: 11/28/2022]
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44
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Affiliation(s)
- Andreas Engel
- Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland;
| | - Hermann E. Gaub
- Center for Nanoscience and Physics Department, University Munich, 80799 Munich, Germany;
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45
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Jin Y, Friedman N, Sheves M, Cahen D. Effect of metal-molecule contact roughness on electronic transport: bacteriorhodopsin-based, metal-insulator-metal planar junctions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5622-5626. [PMID: 18399666 DOI: 10.1021/la703859a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Molecular electronics is very much about contacts, and thus understanding of any generic contact effect is essential to its advance. For example, it is still not obvious in how far variations in electrode roughness of macroscopic contacts can lead to rectification. Here we report an investigation of this contact effect on electronic transport properties using metal-insulator-metal planar junctions with a 5 nm thick bacteriorhodopsin-based insulator as model system. We demonstrate that the experimentally observed rectifying behavior is not an intrinsic property of the molecules used, but rather of the local contact quality. Even a slight increase in surface roughness of the bottom electrode gives rise to distinct rectifying behavior in these and, by extrapolation, possibly other molecular junctions.
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Affiliation(s)
- Yongdong Jin
- Department of Organic Chemistry, Weizman Institute of Science, Rehovot 76100, Israel.
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46
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Hendler RW, Meuse CW. Electrogenic proton-pumping capabilities of the m-fast and m-slow photocycles of bacteriorhodopsin. Biochemistry 2008; 47:5396-405. [PMID: 18422349 DOI: 10.1021/bi701748n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The parallel model for the bacteriorhodopsin (BR) photocycle at neutral pH and a temperature near 20 degrees C contains an M-fast cycle with steps BR-->K-->L-->Mf-->N-->O-->BR and an M-slow cycle which contains steps BR-->K-->L-->Ms-->BR. With increasing actinic laser strength, the M-fast cycle at first rises faster than the M-slow cycle, but reaches saturation sooner and at a lower level than the M-slow cycle. The O-intermediate shows the same saturation behavior as Mf. In this paper, we show that the peak current of proton flux and the apparent voltages developed by this flux show the same saturation behavior as Ms, which is very different from that of both M f and O. It is further shown that most of the proton-charge displacement is connected with the step Ms-->BR. The optical and electrical data in these studies were collected simultaneously by a newly designed and built spectrometer which is described separately.
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Affiliation(s)
- Richard W Hendler
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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47
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Mackenzie C, Eraso JM, Choudhary M, Roh JH, Zeng X, Bruscella P, Puskás A, Kaplan S. Postgenomic adventures with Rhodobacter sphaeroides. Annu Rev Microbiol 2007; 61:283-307. [PMID: 17506668 DOI: 10.1146/annurev.micro.61.080706.093402] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review describes some of the recent highlights taken from the studies of Rhodobacter sphaeroides 2.4.1. The review is not intended to be comprehensive, but to reflect the bias of the authors as to how the availability of a sequenced and annotated genome, a gene-chip, and proteomic profile as well as comparative genomic analyses can direct the progress of future research in this system.
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Affiliation(s)
- Chris Mackenzie
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030, USA.
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48
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Tastan O, Yu E, Ganapathiraju M, Aref A, Rader AJ, Klein-Seetharaman J. Comparison of stability predictions and simulated unfolding of rhodopsin structures. Photochem Photobiol 2007; 83:351-62. [PMID: 17576347 DOI: 10.1562/2006-06-20-ra-942] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Developing a better mechanistic understanding of membrane protein folding is urgently needed because of the discovery of an increasing number of human diseases, where membrane protein instability and misfolding is involved. Towards this goal, we investigated folding and stability of 7-transmembrane (TM) helical bundles by computational methods. We compared the results of three different algorithms for predicting changes in stability of proteins against an experimental mutation dataset obtained for bacteriorhodopsin (BR) and mammalian rhodopsin and find that 61.6% and 70.6% of the mutation results can potentially be explained by known local contributors to the stability of the folded state of BR and mammalian rhodopsin, respectively. To obtain further information on the predicted folding pathway of 7-TM proteins, we conducted simulated thermal unfolding experiments of all available rhodopsin structures with resolution better than 3 angstroms using the Floppy Inclusions and Rigid Substructure Topography (FIRST) method (Jacobs, D. J., A. J. Rader, L. A. Kuhn and M. F. Thorpe [2001] Proteins 44, 150) described previously for a single mammalian rhodopsin structure (Rader et al. [2004] PNAS 101, 7246). In statistical comparison we found that structures of mammalian rhodopsin have a stability core that is characterized by long-range interactions involving amino acids close in space but distant in sequence comprising positions from both extracellular loop and TM regions. In contrast, BR-simulated unfolding does not reveal such a core but is dominated by interactions within individual and groups of TM helices, consistent with the two-stage hypothesis of membrane protein folding. Similar results were obtained for halo- and sensory rhodopsins as for BRs. However, the average folding core energies of sensory rhodopsins were in between those observed for mammalian rhodopsins and BRs hinting at a possible evolution of these structures toward a rhodopsin-like behavior. These results support the conclusion that although the two-stage model can explain the mechanisms of folding and stability of BR, it fails to account for the folding and stability of mammalian rhodopsin, even though the two proteins are structurally related.
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Affiliation(s)
- Oznur Tastan
- Language Technologies Institute, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA
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49
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Zeng X, Roh JH, Callister SJ, Tavano CL, Donohue TJ, Lipton MS, Kaplan S. Proteomic characterization of the Rhodobacter sphaeroides 2.4.1 photosynthetic membrane: identification of new proteins. J Bacteriol 2007; 189:7464-74. [PMID: 17704227 PMCID: PMC2168454 DOI: 10.1128/jb.00946-07] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rhodobacter sphaeroides intracytoplasmic membrane (ICM) is an inducible membrane that is dedicated to the major events of bacterial photosynthesis, including harvesting light energy, separating primary charges, and transporting electrons. In this study, multichromatographic methods coupled with Fourier transform ion cyclotron resonance mass spectrometry, combined with subcellular fractionation, was used to test the hypothesis that the photosynthetic membrane of R. sphaeroides 2.4.1 contains a significant number of heretofore unidentified proteins in addition to the integral membrane pigment-protein complexes, including light-harvesting complexes 1 and 2, the photochemical reaction center, and the cytochrome bc(1) complex described previously. Purified ICM vesicles are shown to be enriched in several abundant, newly identified membrane proteins, including a protein of unknown function (AffyChip designation RSP1760) and a possible alkane hydroxylase (RSP1467). When the genes encoding these proteins are mutated, specific photosynthetic phenotypes are noted, illustrating the potential new insights into solar energy utilization to be gained by this proteomic blueprint of the ICM. In addition, proteins necessary for other cellular functions, such as ATP synthesis, respiration, solute transport, protein translocation, and other physiological processes, were also identified to be in association with the ICM. This study is the first to provide a more global view of the protein composition of a photosynthetic membrane from any source. This protein blueprint also provides insights into potential mechanisms for the assembly of the pigment-protein complexes of the photosynthetic apparatus, the formation of the lipid bilayer that houses these integral membrane proteins, and the possible functional interactions of ICM proteins with activities that reside in domains outside this specialized bioenergetic membrane.
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Affiliation(s)
- Xiaohua Zeng
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston TX, 77030, USA
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50
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Voïtchovsky K, Contera SA, Ryan JF. Electrostatic and steric interactions determine bacteriorhodopsin single-molecule biomechanics. Biophys J 2007; 93:2024-37. [PMID: 17513362 PMCID: PMC1959538 DOI: 10.1529/biophysj.106.101469] [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] [Indexed: 12/29/2022] Open
Abstract
Bacteriorhodopsin (bR) is a haloarchaeal membrane protein that converts the energy of single photons into large structural changes to directionally pump protons across purple membrane. This is achieved by a complex combination of local dynamic interactions controlling bR biomechanics at the submolecular level, producing efficient amplification of the retinal photoisomerization. Using single molecule force spectroscopy at different salt concentrations, we show that tryptophan (Trp) residues use steric specific interactions to create a rigid scaffold in bR extracellular region and are responsible for the main unfolding barriers. This scaffold, which encloses the retinal, controls bR local mechanical properties and anchors the protein into the membrane. Furthermore, the stable Trp-based network allows ion binding to two specific sites on the extracellular loops (BC and FG), which are involved in proton release and lateral transport. In contrast, the cytoplasmic side of bR is mainly governed by relatively weak nonspecific electrostatic interactions that provide the flexibility necessary for large cytoplasmic structural rearrangements during the photocycle. The presence of an extracellular Trp-based network tightly enclosing the retinal seems common to most haloarchaeal rhodopsins, and could be relevant to their exceptional efficiency.
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Affiliation(s)
- Kislon Voïtchovsky
- Bionanotechnology Interdisciplinary Research Collaboration, Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, United Kingdom
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