151
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Moss FR, Shuken SR, Mercer JAM, Cohen CM, Weiss TM, Boxer SG, Burns NZ. Ladderane phospholipids form a densely packed membrane with normal hydrazine and anomalously low proton/hydroxide permeability. Proc Natl Acad Sci U S A 2018; 115:9098-9103. [PMID: 30150407 PMCID: PMC6140541 DOI: 10.1073/pnas.1810706115] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Ladderane lipids are unique to anaerobic ammonium-oxidizing (anammox) bacteria and are enriched in the membrane of the anammoxosome, an organelle thought to compartmentalize the anammox process, which involves the toxic intermediate hydrazine (N2H4). Due to the slow growth rate of anammox bacteria and difficulty of isolating pure ladderane lipids, experimental evidence of the biological function of ladderanes is lacking. We have synthesized two natural and one unnatural ladderane phosphatidylcholine lipids and compared their thermotropic properties in self-assembled bilayers to distinguish between [3]- and [5]-ladderane function. We developed a hydrazine transmembrane diffusion assay using a water-soluble derivative of a hydrazine sensor and determined that ladderane membranes are as permeable to hydrazine as straight-chain lipid bilayers. However, pH equilibration across ladderane membranes occurs 5-10 times more slowly than across straight-chain lipid membranes. Langmuir monolayer analysis and the rates of fluorescence recovery after photobleaching suggest that dense ladderane packing may preclude formation of proton/hydroxide-conducting water wires. These data support the hypothesis that ladderanes prevent the breakdown of the proton motive force rather than blocking hydrazine transmembrane diffusion in anammox bacteria.
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Affiliation(s)
- Frank R Moss
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Steven R Shuken
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Jaron A M Mercer
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Carolyn M Cohen
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Thomas M Weiss
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford University, Menlo Park, CA 94025
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305;
| | - Noah Z Burns
- Department of Chemistry, Stanford University, Stanford, CA 94305;
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152
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SMrT Assay for Real-Time Visualization and Analysis of Clathrin Assembly Reactions. Methods Mol Biol 2018. [PMID: 30129016 DOI: 10.1007/978-1-4939-8719-1_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Clathrin-mediated endocytosis manages the vesicular transport of the bulk of membrane proteins from the plasma membrane and the trans-Golgi network. During this process, discrete sets of adaptor proteins recognize specific classes of membrane proteins, which recruit and assemble clathrin lattices on the membrane. An important determinant to the success of this vesicular transport reaction is the intrinsic ability of adaptors to polymerize clathrin on a membrane surface. Adaptor-induced clathrin assembly has traditionally been analyzed using static electron microscopy-based approaches. Here, we describe a methodology to follow adaptor-induced clathrin assembly in real-time using fluorescence microscopy on a facile model membrane assay system of supported membrane tubes (SMrT). Results from such assays can be conveniently run through routine image analysis procedures to extract kinetic parameters of the clathrin assembly reaction.
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153
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Donaphon B, Bloom LB, Levitus M. Photophysical characterization of interchromophoric interactions between rhodamine dyes conjugated to proteins. Methods Appl Fluoresc 2018; 6:045004. [PMID: 29985159 DOI: 10.1088/2050-6120/aad20f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Rhodamine dyes in aqueous solution form non-fluorescent dimers with a plane-to-plane stacking geometry (H-dimers). The self-quenching properties of these dimers have been exploited to probe the conformation and dynamics of proteins using a variety of fluorescence approaches that require the interpretation of fluorescence intensities, lifetimes and fluctuations. Here, we report on a systematic study of the photophysical properties of three rhodamine dyes (tetramethylrhodamine, Alexa 488 and Alexa 546) covalently bound to the E. coli sliding clamp (β clamp) with emphasis on the properties of the H-dimers that form when the dimeric protein is labeled with one dye at each side of the dimer interface. Overall, results are consistent with an equilibrium between non-emissive dimers and unstacked monomers that experience efficient dynamic quenching Protein constructs labeled with tetramethylrhodamine show the characteristic features of H-dimers in their absorption spectra and a c.a. 40-fold quenching of fluorescence intensity. The degree of quenching decreases when samples are labeled with a tetramethylrhodamine derivative bearing a six-carbon linker. H-dimers do not form in samples labeled with Alexa 488 and A546, but fluorescence is still quenched in these samples through a dynamic mechanism. These results should help researchers design and interpret fluorescence experiments that take advantage of the properties of rhodamine dimers in protein research.
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Affiliation(s)
- Bryan Donaphon
- School of Molecular Sciences and Biodesign Institute, Arizona State University, Tempe, AZ 85287, United States of America
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154
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Abstract
Dextrans are a versatile class of polysaccharides with applications that span medicine, cell biology, food science, and consumer goods. Here, we report on a new type of large monofunctionalized dextran that exhibits unusual properties: efficient cytosolic and nuclear uptake. This dextran permeates various human cell types without the use of transfection agents, electroporation, or membrane perturbation. Cellular uptake occurs primarily through active transport via receptor-mediated processes. These monofunctionalized dextrans could serve as intracellular delivery platforms for drugs or other cargos.
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Affiliation(s)
- Wen Chyan
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Henry R. Kilgore
- Graduate Program in Biophysics, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Ronald T. Raines
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
- Department of Biochemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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155
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Diederichs T, Nguyen QH, Urban M, Tampé R, Tornow M. Transparent Nanopore Cavity Arrays Enable Highly Parallelized Optical Studies of Single Membrane Proteins on Chip. NANO LETTERS 2018; 18:3901-3910. [PMID: 29741381 DOI: 10.1021/acs.nanolett.8b01252] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Membrane proteins involved in transport processes are key targets for pharmaceutical research and industry. Despite continuous improvements and new developments in the field of electrical readouts for the analysis of transport kinetics, a well-suited methodology for high-throughput characterization of single transporters with nonionic substrates and slow turnover rates is still lacking. Here, we report on a novel architecture of silicon chips with embedded nanopore microcavities, based on a silicon-on-insulator technology for high-throughput optical readouts. Arrays containing more than 14 000 inverted-pyramidal cavities of 50 femtoliter volumes and 80 nm circular pore openings were constructed via high-resolution electron-beam lithography in combination with reactive ion etching and anisotropic wet etching. These cavities feature both, an optically transparent bottom and top cap. Atomic force microscopy analysis reveals an overall extremely smooth chip surface, particularly in the vicinity of the nanopores, which exhibits well-defined edges. Our unprecedented transparent chip design provides parallel and independent fluorescent readout of both cavities and buffer reservoir for unbiased single-transporter recordings. Spreading of large unilamellar vesicles with efficiencies up to 96% created nanopore-supported lipid bilayers, which are stable for more than 1 day. A high lipid mobility in the supported membrane was determined by fluorescent recovery after photobleaching. Flux kinetics of α-hemolysin were characterized at single-pore resolution with a rate constant of 0.96 ± 0.06 × 10-3 s-1. Here, we deliver an ideal chip platform for pharmaceutical research, which features high parallelism and throughput, synergistically combined with single-transporter resolution.
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Affiliation(s)
- Tim Diederichs
- Institute of Biochemistry, Biocenter , Goethe University Frankfurt , Max-von-Laue-Str. 9 , 60438 Frankfurt/M. , Germany
| | - Quoc Hung Nguyen
- Molecular Electronics , Technical University of Munich , Theresienstrasse 90 , 80333 Munich , Germany
| | - Michael Urban
- Institute of Biochemistry, Biocenter , Goethe University Frankfurt , Max-von-Laue-Str. 9 , 60438 Frankfurt/M. , Germany
| | - Robert Tampé
- Institute of Biochemistry, Biocenter , Goethe University Frankfurt , Max-von-Laue-Str. 9 , 60438 Frankfurt/M. , Germany
- Cluster of Excellence Frankfurt (CEF) Macromolecular Complexes ; Goethe University Frankfurt , Max-von-Laue-Strasse 9 , 60438 Frankfurt/M. , Germany
| | - Marc Tornow
- Molecular Electronics , Technical University of Munich , Theresienstrasse 90 , 80333 Munich , Germany
- Fraunhofer Research Institution for Microsystems and Solid State Technologies (EMFT) , Hansastrasse 27d , 80686 Munich , Germany
- Center for NanoScience (CeNS) , Ludwig-Maximilians-University , Geschwister-Scholl Platz 1 , 80539 Munich , Germany
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156
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Ripp S, Turunen P, Minot ED, Rowan AE, Blank KG. Deciphering Design Principles of Förster Resonance Energy Transfer-Based Protease Substrates: Thermolysin-Like Protease from Geobacillus stearothermophilus as a Test Case. ACS OMEGA 2018; 3:4148-4156. [PMID: 31458650 PMCID: PMC6641592 DOI: 10.1021/acsomega.7b02084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 03/19/2018] [Indexed: 06/10/2023]
Abstract
Protease activity is frequently assayed using short peptides that are equipped with a Förster resonance energy transfer (FRET) reporter system. Many frequently used donor-acceptor pairs are excited in the ultraviolet range and suffer from low extinction coefficients and quantum yields, limiting their usefulness in applications where a high sensitivity is required. A large number of alternative chromophores are available that are excited in the visible range, for example, based on xanthene or cyanine core structures. These alternatives are not only larger in size but also more hydrophobic. Here, we show that the hydrophobicity of these chromophores not only affects the solubility of the resulting FRET-labeled peptides but also their kinetic parameters in a model enzymatic reaction. In detail, we have compared two series of 4-8 amino acid long peptides, designed to serve as substrates for the thermolysin-like protease (TLP-ste) from Geobacillus stearothermophilus. These peptides were equipped with a carboxyfluorescein donor and either Cy5 or its sulfonated derivative Alexa Fluor 647 as the acceptor. We show that the turnover rate k cat is largely unaffected by the choice of the acceptor fluorophore, whereas the K M value is significantly lower for the Cy5- than for the Alexa Fluor 647-labeled substrates. TLP-ste is a rather nonspecific protease with a large number of hydrophobic amino acids surrounding the catalytic site, so that the fluorophore itself may form additional interactions with the enzyme. This hypothesis is supported by the result that the difference between Cy5- and Alexa Fluor 647-labeled substrates becomes less pronounced with increasing peptide length, that is, when the fluorophore is positioned at a larger distance from the catalytic site. These results suggest that fluorophores may become an integral part of FRET-labeled peptide substrates and that K M and k cat values are generally only valid for a specific combination of the peptide sequence and FRET pair.
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Affiliation(s)
- Sophie Ripp
- Institute
for Molecules and Materials, Department of Molecular Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Petri Turunen
- Institute
for Molecules and Materials, Department of Molecular Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ethan D. Minot
- Department
of Physics, Oregon State University, 301 Weniger Hall, Corvallis, Oregon 97331-6507, United States
| | - Alan E. Rowan
- Institute
for Molecules and Materials, Department of Molecular Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Kerstin G. Blank
- Institute
for Molecules and Materials, Department of Molecular Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
- Mechano(bio)chemistry,
Max Planck Institute of Colloids and Interfaces, Potsdam-Golm Science Park, 14424 Potsdam, Germany
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157
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Schoch RL, Barel I, Brown FLH, Haran G. Lipid diffusion in the distal and proximal leaflets of supported lipid bilayer membranes studied by single particle tracking. J Chem Phys 2018; 148:123333. [DOI: 10.1063/1.5010341] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Rafael L. Schoch
- Department of Chemical and Biological Physics, Weizmann Institute of Science, P.O. Box 26, Rehovot 7610001, Israel
| | - Itay Barel
- Department of Chemistry and Biochemistry and Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - Frank L. H. Brown
- Department of Chemistry and Biochemistry and Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - Gilad Haran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, P.O. Box 26, Rehovot 7610001, Israel
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158
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Tiwari A, Prince A, Arakha M, Jha S, Saleem M. Passive membrane penetration by ZnO nanoparticles is driven by the interplay of electrostatic and phase boundary conditions. NANOSCALE 2018; 10:3369-3384. [PMID: 29388654 DOI: 10.1039/c7nr08351c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The internalization of nanoparticles through the biological membrane is of immense importance for biomedical applications. A fundamental understanding of the lipid specificity and the role of the membrane biochemical and physical forces at play in modulating penetration are lacking. The current understanding of nanoparticle-membrane interaction is drawn mostly from computational studies and lacks sufficient experimental evidence. Herein, using confocal fluorescence imaging and potentiometric dye-based fluorimetry, we first investigated the interaction of ZnONP in both multi-component and individual lipid membranes using cell-like giant unilamellar vesicles to dissect the lipid specificity; also, we investigated the changes in membrane order, anisotropy and hydrophobicity. ZnONP was found to interact with phosphatidylinositol and phosphatidylcholine head-group-containing lipids specifically. We further investigated the interaction of ZnONP with three physiologically relevant membrane conditions varying in composition and dipole potential. We found that ZnONP interaction leads to a photoinduced enhancement of the partial-to-complete phase separation depending upon the membrane composition and cholesterol content. Interestingly, while the lipid order of a partially-phase-separated membrane remained unchanged upon ZnONP crowding, a fully-phase-separated membrane showed an increase in the lipid order. Strikingly, ZnONP crowding induced a contrasting effect on the fluorescence anisotropy of the membrane upon binding to the two membrane conditions, in line with the measured diffusion coefficient. ZnONP seems to preferentially penetrate through the liquid disordered areas of the membrane and the boundaries of the phase-separated regions driven by the interplay between the electrostatics and phase boundary conditions, which are collectively dictated by the composition and ZnONP-induced lipid reorganization. The results may lead to a greater understanding of the interplay of membrane parameters and ZnONP interaction in driving passive penetration.
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Affiliation(s)
- Anuj Tiwari
- Department of Life Sciences, National Institute of Technology, Rourkela, India - 769008.
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159
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Cauldbeck H, Le Hellaye M, McDonald TO, Long M, Williams RL, Rannard SP, Kearns VR. Modulated release from implantable ocular silicone oil tamponade drug reservoirs. ACTA ACUST UNITED AC 2018; 56:938-946. [PMID: 29610546 PMCID: PMC5873246 DOI: 10.1002/pola.28973] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 01/22/2018] [Indexed: 11/07/2022]
Abstract
Complicated cases of retinal detachment can be treated with silicone oil tamponades. There is the potential for silicone oil tamponades to have adjunctive drug releasing behaviour within the eye, however the lipophilic nature of silicone oil limits the number of drugs that are suitable, and drug release from the hydrophobic reservoir is uncontrolled. Here, a radiometric technique was developed to accurately measure drug solubility in silicone oil and measure release into culture media. All-trans retinoic acid (atRA), a lipophilic drug known to act as an anti-proliferative within the eye, was used throughout this work. Chain-end modification of polydimethylsiloxane with atRA produced a polydimethylsiloxane retinoate (PDMS-atRA), which was used as an additive to silicone oil to modify the solvent environment within the silicone oil and the distribution coefficient. Blends of PDMS-atRA and silicone oil containing different concentrations of free atRA were produced. The presence of PDMS-atRA in silicone oil had a positive effect on atRA solubility and the longevity of release in vitro. The drug release period was independent of atRA starting concentration and dependent on the PDMS-atRA concentration in the blend. A clinically relevant release period of atRA over 7 weeks from a silicone oil blend with PDMS-atRA was observed. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 938-946.
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Affiliation(s)
- Helen Cauldbeck
- Department of Eye and Vision Science University of Liverpool Liverpool L7 8TX United Kingdom.,Department of Chemistry University of Liverpool, Crown Street Liverpool L69 7ZD United Kingdom
| | - Maude Le Hellaye
- Department of Eye and Vision Science University of Liverpool Liverpool L7 8TX United Kingdom.,Department of Chemistry University of Liverpool, Crown Street Liverpool L69 7ZD United Kingdom
| | - Tom O McDonald
- Department of Chemistry University of Liverpool, Crown Street Liverpool L69 7ZD United Kingdom
| | - Mark Long
- Unilever Research & Development Port Sunlight Laboratory, Quarry Road East Bebington Wirral CH63 3JW United Kingdom
| | - Rachel L Williams
- Department of Eye and Vision Science University of Liverpool Liverpool L7 8TX United Kingdom
| | - Steve P Rannard
- Department of Chemistry University of Liverpool, Crown Street Liverpool L69 7ZD United Kingdom
| | - Victoria R Kearns
- Department of Eye and Vision Science University of Liverpool Liverpool L7 8TX United Kingdom
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160
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Assays with Detection of Fluorescence Anisotropy: Challenges and Possibilities for Characterizing Ligand Binding to GPCRs. Trends Pharmacol Sci 2018; 39:187-199. [DOI: 10.1016/j.tips.2017.10.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/10/2017] [Accepted: 10/10/2017] [Indexed: 01/24/2023]
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161
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Escudero C, Vera M, Oggerin M, Amils R. Active microbial biofilms in deep poor porous continental subsurface rocks. Sci Rep 2018; 8:1538. [PMID: 29367593 PMCID: PMC5784017 DOI: 10.1038/s41598-018-19903-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 01/08/2018] [Indexed: 11/24/2022] Open
Abstract
Deep continental subsurface is defined as oligotrophic environments where microorganisms present a very low metabolic rate. To date, due to the energetic cost of production and maintenance of biofilms, their existence has not been considered in poor porous subsurface rocks. We applied fluorescence in situ hybridization techniques and confocal laser scanning microscopy in samples from a continental deep drilling project to analyze the prokaryotic diversity and distribution and the possible existence of biofilms. Our results show the existence of natural microbial biofilms at all checked depths of the Iberian Pyrite Belt (IPB) subsurface and the co-occurrence of bacteria and archaea in this environment. This observation suggests that multi-species biofilms may be a common and widespread lifestyle in subsurface environments.
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Affiliation(s)
- Cristina Escudero
- Centro de Biología Molecular Severo Ochoa (UAM-CSIC), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Mario Vera
- Instituto de Ingeniería Biológica y Médica, Escuelas de Ingeniería, Medicina y Ciencias Biológicas, Departamento de Ingeniería Hidráulica y Ambiental, Escuela de Ingeniería, Pontificia Universidad Católica de Chile, Av Vicuña Mackenna, 4860, Santiago, Chile
| | - Monike Oggerin
- Centro de Biología Molecular Severo Ochoa (UAM-CSIC), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain.,Centro de Astrobiología (CSIC-INTA), Ctra de Ajalvir km 4, Torrejón de Ardoz, 28850, Madrid, Spain
| | - Ricardo Amils
- Centro de Biología Molecular Severo Ochoa (UAM-CSIC), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain. .,Centro de Astrobiología (CSIC-INTA), Ctra de Ajalvir km 4, Torrejón de Ardoz, 28850, Madrid, Spain.
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162
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Conner JW. Fluorogens: Generating Receptor-Specific Turn-On Fluorescence. Aust J Chem 2018. [DOI: 10.1071/ch17492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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163
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Nikić-Spiegel I. Genetic Code Expansion- and Click Chemistry-Based Site-Specific Protein Labeling for Intracellular DNA-PAINT Imaging. Methods Mol Biol 2018; 1728:279-295. [PMID: 29405005 DOI: 10.1007/978-1-4939-7574-7_18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Super-resolution microscopy allows imaging of cellular structures at nanometer resolution. This comes with a demand for small labels which can be attached directly to the structures of interest. In the context of protein labeling, one way to achieve this is by using genetic code expansion (GCE) and click chemistry. With GCE, small labeling handles in the form of noncanonical amino acids (ncAAs) are site-specifically introduced into a target protein. In a subsequent step, these amino acids can be directly labeled with small organic dyes by click chemistry reactions. Click chemistry labeling can also be combined with other methods, such as DNA-PAINT in which a "clickable" oligonucleotide is first attached to the ncAA-bearing target protein and then labeled with complementary fluorescent oligonucleotides. This protocol will cover both aspects: I describe (1) how to encode ncAAs and perform intracellular click chemistry-based labeling with an improved GCE system for eukaryotic cells and (2) how to combine click chemistry-based labeling with DNA-PAINT super-resolution imaging. As an example, I show click-PAINT imaging of vimentin and low-abundance nuclear protein, nucleoporin 153.
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Affiliation(s)
- Ivana Nikić-Spiegel
- Werner Reichardt Centre for Integrative Neuroscience, The Eberhard Karls University of Tübingen, Tübingen, Germany.
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164
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Manger LH, Foote AK, Wood SL, Holden MR, Heylman KD, Margittai M, Goldsmith RH. Revealing Conformational Variants of Solution-Phase Intrinsically Disordered Tau Protein at the Single-Molecule Level. Angew Chem Int Ed Engl 2017; 56:15584-15588. [PMID: 29063723 PMCID: PMC5831721 DOI: 10.1002/anie.201708242] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/05/2017] [Indexed: 11/09/2022]
Abstract
Intrinsically disordered proteins, such as tau protein, adopt a variety of conformations in solution, complicating solution-phase structural studies. We employed an anti-Brownian electrokinetic (ABEL) trap to prolong measurements of single tau proteins in solution. Once trapped, we recorded the fluorescence anisotropy to investigate the diversity of conformations sampled by the single molecules. A distribution of anisotropy values obtained from trapped tau protein is conspicuously bimodal while those obtained by trapping a globular protein or individual fluorophores are not. Time-resolved fluorescence anisotropy measurements were used to provide an explanation of the bimodal distribution as originating from a shift in the compaction of the two different families of conformations.
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Affiliation(s)
- Lydia H Manger
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Alexander K Foote
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Sharla L Wood
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Michael R Holden
- Department of Chemistry & Biochemistry, University of Denver, 2190 East Iliff Ave., Denver, CO, 80208, USA
| | - Kevin D Heylman
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Martin Margittai
- Department of Chemistry & Biochemistry, University of Denver, 2190 East Iliff Ave., Denver, CO, 80208, USA
| | - Randall H Goldsmith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
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165
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Di Paolo D, Afanzar O, Armitage JP, Berry RM. Single-molecule imaging of electroporated dye-labelled CheY in live Escherichia coli. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0492. [PMID: 27672145 PMCID: PMC5052738 DOI: 10.1098/rstb.2015.0492] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2016] [Indexed: 11/12/2022] Open
Abstract
For the past two decades, the use of genetically fused fluorescent proteins (FPs) has greatly contributed to the study of chemotactic signalling in Escherichia coli including the activation of the response regulator protein CheY and its interaction with the flagellar motor. However, this approach suffers from a number of limitations, both biological and biophysical: for example, not all fusions are fully functional when fused to a bulky FP, which can have a similar molecular weight to its fused counterpart; they may interfere with the native interactions of the protein and the chromophores of FPs have low brightness and photostability and fast photobleaching rates. A recently developed technique for the electroporation of fluorescently labelled proteins in live bacteria has enabled us to bypass these limitations and study the in vivo behaviour of CheY at the single-molecule level. Here we show that purified CheY proteins labelled with organic dyes can be internalized into E. coli cells in controllable concentrations and imaged with video fluorescence microscopy. The use of this approach is illustrated by showing single CheY molecules diffusing within cells and interacting with the sensory clusters and the flagellar motors in real time. This article is part of the themed issue ‘The new bacteriology’.
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Affiliation(s)
- Diana Di Paolo
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Oshri Afanzar
- Department of Biological Chemistry, The Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Richard M Berry
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
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166
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Revealing Conformational Variants of Solution-Phase Intrinsically Disordered Tau Protein at the Single-Molecule Level. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201708242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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167
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Bixner O, Gal N, Zaba C, Scheberl A, Reimhult E. Fluorescent Magnetopolymersomes: A Theranostic Platform to Track Intracellular Delivery. MATERIALS (BASEL, SWITZERLAND) 2017; 10:E1303. [PMID: 29137172 PMCID: PMC5706250 DOI: 10.3390/ma10111303] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 11/07/2017] [Accepted: 11/10/2017] [Indexed: 12/19/2022]
Abstract
We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent and magnetic vesicles is described. Cell uptake of the densely PEGylated polymer vesicles could be altered by surface modifications that vary surface charge and accessibility of the membrane active species. Cell uptake and cytotoxicity were evaluated by confocal microscopy, transmission electron microscopy, iron content and metabolic assays, utilizing multimodal tracking of membrane fluorophores and nanoparticles. Cationic functionalization of vesicles promoted endocytotic uptake. In particular, incorporation of cationic lipids in the polymersome membrane yielded tremendously increased uptake of polymersomes and magnetopolymersomes without increase in cytotoxicity. Ultrastructure investigations showed that cationic magnetopolymersomes disintegrated upon hydrolysis, including the dissolution of incorporated iron oxide nanoparticles. The presented platform could find future use in theranostic multimodal imaging in vivo and magnetically triggered delivery by incorporation of thermorepsonsive amphiphiles that can break the membrane integrity upon magnetic heating via the embedded superparamagnetic nanoparticles.
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Affiliation(s)
- Oliver Bixner
- Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190 Vienna, Austria.
| | - Noga Gal
- Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190 Vienna, Austria.
| | - Christoph Zaba
- Institute for Synthetic Bioarchitectures, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190 Vienna, Austria.
| | - Andrea Scheberl
- Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190 Vienna, Austria.
| | - Erik Reimhult
- Institute for Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190 Vienna, Austria.
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168
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Fearon AD, Stokes GY. Thermodynamics of Indomethacin Adsorption to Phospholipid Membranes. J Phys Chem B 2017; 121:10508-10518. [PMID: 29064244 DOI: 10.1021/acs.jpcb.7b08359] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Using second-harmonic generation, we directly monitored adsorption of indomethacin, a nonsteroidal anti-inflammatory drug, to supported lipid bilayers composed of phospholipids of varying phase, cholesterol content, and head group charge without the use of extrinsic labels at therapeutically relevant aqueous concentrations. Indomethacin adsorbed to gel-phase lipids with a high binding affinity, suggesting that like other arylacetic acid-containing drugs, it preferentially interacts with ordered lipid domains. We discovered that adsorption of indomethacin to gel-phase phospholipids was endothermic and entropically driven, whereas adsorption to fluid-phase phospholipids was exothermic and enthalpically driven. As temperature increased from 19 to 34 °C, binding affinities to gel-phase lipids increased by 7-fold but relative surface concentration decreased to one-fifth of the original value. We also compared our results to the entropies reported for indomethacin adsorbed to surfactant micelles, which are used in drug delivery systems, and assert that adsorbed water molecules in the phospholipid bilayer may be buried deeper into the acyl chains and less accessible for disruption. The thermodynamic studies reported here provide mechanistic insight into indomethacin interactions with mammalian plasma membranes in the gastrointestinal tract and inform studies of drug delivery, where indomethacin is commonly used as a prototypical, hydrophobic small-molecule drug.
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Affiliation(s)
- Amanda D Fearon
- Department of Chemistry and Biochemistry, Santa Clara University , 500 El Camino Real, Santa Clara, California 95053, United States
| | - Grace Y Stokes
- Department of Chemistry and Biochemistry, Santa Clara University , 500 El Camino Real, Santa Clara, California 95053, United States
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169
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Zhao Z, Shen Y, Hu F, Min W. Applications of vibrational tags in biological imaging by Raman microscopy. Analyst 2017; 142:4018-4029. [PMID: 28875184 PMCID: PMC5674523 DOI: 10.1039/c7an01001j] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
As a superb tool to visualize and study the spatial-temporal distribution of chemicals, Raman microscopy has made a big impact in many disciplines of science. While label-free imaging has been the prevailing strategy in Raman microscopy, recent development and applications of vibrational/Raman tags, particularly when coupled with stimulated Raman scattering (SRS) microscopy, have generated intense excitement in biomedical imaging. SRS imaging of vibrational tags has enabled researchers to study a wide range of small biomolecules with high specificity, sensitivity and multiplex capability, at a single live cell level, tissue level or even in vivo. As reviewed in this article, this platform has facilitated imaging distribution and dynamics of small molecules such as glucose, lipids, amino acids, nucleic acids, and drugs that are otherwise difficult to monitor with other means. As both the vibrational tags and Raman instrumental development progress rapidly and synergistically, we anticipate that this technique will shed light onto an even broader spectrum of biomedical problems.
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Affiliation(s)
- Zhilun Zhao
- Department of Chemistry, Columbia University, New York, 10027, USA.
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170
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Abstract
Secondary ion mass spectrometry (SIMS) has become an increasingly utilized tool in biologically relevant studies. Of these, high lateral resolution methodologies using the NanoSIMS 50/50L have been especially powerful within many biological fields over the past decade. Here, the authors provide a review of this technology, sample preparation and analysis considerations, examples of recent biological studies, data analyses, and current outlooks. Specifically, the authors offer an overview of SIMS and development of the NanoSIMS. The authors describe the major experimental factors that should be considered prior to NanoSIMS analysis and then provide information on best practices for data analysis and image generation, which includes an in-depth discussion of appropriate colormaps. Additionally, the authors provide an open-source method for data representation that allows simultaneous visualization of secondary electron and ion information within a single image. Finally, the authors present a perspective on the future of this technology and where they think it will have the greatest impact in near future.
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171
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Sánchez-Rico C, Voith von Voithenberg L, Warner L, Lamb DC, Sattler M. Effects of Fluorophore Attachment on Protein Conformation and Dynamics Studied by spFRET and NMR Spectroscopy. Chemistry 2017; 23:14267-14277. [PMID: 28799205 DOI: 10.1002/chem.201702423] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Indexed: 12/28/2022]
Abstract
Fluorescence-based techniques are widely used to study biomolecular conformations, intra- and intermolecular interactions, and conformational dynamics of macromolecules. Especially for fluorescence-based single-molecule experiments, the choice of the fluorophore and labeling position are highly important. In this work, we studied the biophysical and structural effects that are associated with the conjugation of fluorophores to cysteines in the splicing factor U2AF65 by using single pair Förster resonance energy transfer (FRET) and nuclear magnetic resonance (NMR) spectroscopy. It is shown that certain acceptor fluorophores are advantageous depending on the experiments performed. The effects of dye attachment on the protein conformation were characterized using heteronuclear NMR experiments. The presence of hydrophobic and aromatic moieties in the fluorophores can significantly affect the conformation of the conjugated protein, presumably by transient interactions with the protein surface. Guidelines are provided for carefully choosing fluorophores, considering their photophysical properties and chemical features for the design of FRET experiments, and for minimizing artifacts.
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Affiliation(s)
- Carolina Sánchez-Rico
- Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.,Biomolecular NMR and Center for Integrated Protein Science Munich at Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747, Garching, Germany
| | - Lena Voith von Voithenberg
- Physical Chemistry, Department of Chemistry, Munich Center for Integrated Protein Science, Nanosystems Initiative Munich and Centre for Nanoscience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Lisa Warner
- Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.,Biomolecular NMR and Center for Integrated Protein Science Munich at Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747, Garching, Germany
| | - Don C Lamb
- Physical Chemistry, Department of Chemistry, Munich Center for Integrated Protein Science, Nanosystems Initiative Munich and Centre for Nanoscience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.,Biomolecular NMR and Center for Integrated Protein Science Munich at Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747, Garching, Germany
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172
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Xu J, Zhang B, Jansen M, Goerigk L, Wong WWH, Ritchie C. Highly Fluorescent Pyridinium Betaines for Light Harvesting. Angew Chem Int Ed Engl 2017; 56:13882-13886. [DOI: 10.1002/anie.201704832] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 06/29/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Jingjing Xu
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
| | - Bolong Zhang
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
| | - Marina Jansen
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
- Present Address: Organisch-Chemisches Institut der Universität Münster Corrensstrasse 40 48149 Münster Germany
| | - Lars Goerigk
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
| | - Wallace W. H. Wong
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
- ARC Centre of Excellence in Exciton Science School of Chemistry The University of Melbourne Parkville Victoria 3010 Australia
| | - Chris Ritchie
- School of Chemistry The University of Melbourne Bio21 Institute 30 Flemington Road Parkville Victoria 3010 Australia
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173
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174
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Jacobsen MT, Fairhead M, Fogelstrand P, Howarth M. Amine Landscaping to Maximize Protein-Dye Fluorescence and Ultrastable Protein-Ligand Interaction. Cell Chem Biol 2017; 24:1040-1047.e4. [PMID: 28757182 PMCID: PMC5563079 DOI: 10.1016/j.chembiol.2017.06.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 05/15/2017] [Accepted: 06/27/2017] [Indexed: 12/11/2022]
Abstract
Chemical modification of proteins provides great opportunities to control and visualize living systems. The most common way to modify proteins is reaction of their abundant amines with N-hydroxysuccinimide (NHS) esters. Here we explore the impact of amine number and positioning on protein-conjugate behavior using streptavidin-biotin, a central research tool. Dye-NHS modification of streptavidin severely damaged ligand binding, necessitating development of a new streptavidin-retaining ultrastable binding after labeling. Exploring the ideal level of dye modification, we engineered a panel bearing 1–6 amines per subunit: “amine landscaping.” Surprisingly, brightness increased as amine number decreased, revealing extensive quenching following conventional labeling. We ultimately selected Flavidin (fluorophore-friendly streptavidin), combining ultrastable ligand binding with increased brightness after conjugation. Flavidin enhanced fluorescent imaging, allowing more sensitive and specific cell labeling in tissues. Flavidin should have wide application in molecular detection, providing a general insight into how to optimize simultaneously the behavior of the biomolecule and the chemical probe. Labeling of streptavidin with small-molecule dyes impairs ligand binding K121R mutation rescues ligand stability after dye labeling Landscaping of protein amines optimizes brightness Fluorophore-friendly streptavidin improves imaging specificity and sensitivity
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Affiliation(s)
- Michael T Jacobsen
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Michael Fairhead
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Per Fogelstrand
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Mark Howarth
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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175
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Membrane Curvature and Lipid Composition Synergize To Regulate N-Ras Anchor Recruitment. Biophys J 2017; 113:1269-1279. [PMID: 28738989 DOI: 10.1016/j.bpj.2017.06.051] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 06/26/2017] [Accepted: 06/27/2017] [Indexed: 11/22/2022] Open
Abstract
Proteins anchored to membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to membrane domains of different lipid composition. We recently showed that membrane shape/curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how membrane curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of membrane curvature to recruit lipidated proteins. As a model system we used the lipidated minimal membrane anchor of the GTPase, N-Ras (tN-Ras). Our data revealed complex synergistic effects, whereby tN-Ras binding was higher on planar DOPC than POPC membranes, but inversely higher on curved POPC than DOPC membranes. This variation in the binding to both planar and curved membranes leads to a net increase in the recruitment by membrane curvature of tN-Ras when reducing the acyl chain saturation state. Additionally, we found increased recruitment by membrane curvature of tN-Ras when substituting PC for PE, and when decreasing acyl chain length from 14 to 12 carbons (DMPC versus DLPC). However, these variations in recruitment ability had different origins, with the headgroup size primarily influencing tN-Ras binding to planar membranes whereas the change in acyl chain length primarily affected binding to curved membranes. Molecular field theory calculations recapitulated these findings and revealed lateral pressure as an underlying biophysical mechanism dictating how curvature and composition synergize to modulate recruitment of lipidated proteins. Our findings suggest that the different compositions of cellular compartments could modulate the potency of membrane curvature to recruit lipidated proteins and thereby synergistically regulate the trafficking and sorting of lipidated proteins.
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176
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Sjöholm J, Bergstrand J, Nilsson T, Šachl R, Ballmoos CV, Widengren J, Brzezinski P. The lateral distance between a proton pump and ATP synthase determines the ATP-synthesis rate. Sci Rep 2017; 7:2926. [PMID: 28592883 PMCID: PMC5462737 DOI: 10.1038/s41598-017-02836-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/19/2017] [Indexed: 11/09/2022] Open
Abstract
We have investigated the effect of lipid composition on interactions between cytochrome bo 3 and ATP-synthase, and the ATP-synthesis activity driven by proton pumping. The two proteins were labeled by fluorescent probes and co-reconstituted in large (d ≅ 100 nm) or giant (d ≅ 10 µm) unilamellar lipid vesicles. Interactions were investigated using fluorescence correlation/cross-correlation spectroscopy and the activity was determined by measuring ATP production, driven by electron-proton transfer, as a function of time. We found that conditions that promoted direct interactions between the two proteins in the membrane (higher fraction DOPC lipids or labeling by hydrophobic molecules) correlated with an increased activity. These data indicate that the ATP-synthesis rate increases with decreasing distance between cytochrome bo 3 and the ATP-synthase, and involves proton transfer along the membrane surface. The maximum distance for lateral proton transfer along the surface was found to be ~80 nm.
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Affiliation(s)
- Johannes Sjöholm
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Jan Bergstrand
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), SE-106 91, Stockholm, Sweden
| | - Tobias Nilsson
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Radek Šachl
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the A.S.C.R. v.v.i., Prague, Czech Republic
| | | | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology (KTH), SE-106 91, Stockholm, Sweden
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
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177
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Schneider F, Ruhlandt D, Gregor I, Enderlein J, Chizhik AI. Quantum Yield Measurements of Fluorophores in Lipid Bilayers Using a Plasmonic Nanocavity. J Phys Chem Lett 2017; 8:1472-1475. [PMID: 28296418 DOI: 10.1021/acs.jpclett.7b00422] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Precise knowledge of the quantum yield is important for many fluorescence-spectroscopic techniques, for example, for Förster resonance energy transfer. However, to measure it for emitters in a complex environment and at low concentrations is far from being trivial. Using a plasmonic nanocavity, we measure the absolute quantum yield value of lipid-conjugated dyes incorporated into a supported lipid bilayer. We show that for both hydrophobic and hydrophilic molecules the quantum yield of dyes inside the lipid bilayer strongly differs from its value in aqueous solution. This finding is of particular importance for all fluorescence-spectroscopic studies involving lipid bilayers, such as protein-protein or protein-lipid interactions in membranes or direct fluorescence-spectroscopic measurements of membrane physical properties.
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Affiliation(s)
- Falk Schneider
- University of Göttingen, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Daja Ruhlandt
- University of Göttingen, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Ingo Gregor
- University of Göttingen, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Jörg Enderlein
- University of Göttingen, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Alexey I Chizhik
- University of Göttingen, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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178
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Zhang Z, Yomo D, Gradinaru C. Choosing the right fluorophore for single-molecule fluorescence studies in a lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1242-1253. [PMID: 28392350 DOI: 10.1016/j.bbamem.2017.04.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/14/2017] [Accepted: 04/05/2017] [Indexed: 10/19/2022]
Abstract
Nonspecific interactions between lipids and fluorophores can alter the outcomes of single-molecule spectroscopy of membrane proteins in live cells, liposomes or lipid nanodiscs and of cytosolic proteins encapsulated in liposomes or tethered to supported lipid bilayers. To gain insight into these effects, we examined interactions between 9 dyes that are commonly used as labels for single-molecule fluorescence (SMF) and 6 standard lipids including cationic, zwitterionic and anionic types. The diffusion coefficients of dyes in the absence and presence of set amounts of lipid vesicles were measured by fluorescence correlation spectroscopy (FCS). The partition coefficients and the free energies of partitioning for different fluorophore-lipid pairs were obtained by global fitting of the titration FCS curves. Lipids with different charges, head groups and degrees of chain saturation were investigated, and interactions with dyes are discussed in terms of hydrophobic, electrostatic and steric contributions. Fluorescence imaging of individual fluorophores adsorbed on supported lipid bilayers provides visualization and additional quantification of the strength of dye-lipid interaction in the context of single-molecule measurements. By dissecting fluorophore-lipid interactions, our study provides new insights into setting up single-molecule fluorescence spectroscopy experiments with minimal interference from interactions between fluorescent labels and lipids in the environment.
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Affiliation(s)
- Zhenfu Zhang
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada; Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Dan Yomo
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada; Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Claudiu Gradinaru
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada; Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada.
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179
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Chamma I, Rossier O, Giannone G, Thoumine O, Sainlos M. Optimized labeling of membrane proteins for applications to super-resolution imaging in confined cellular environments using monomeric streptavidin. Nat Protoc 2017; 12:748-763. [DOI: 10.1038/nprot.2017.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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180
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Mailfert S, Hamon Y, Bertaux N, He HT, Marguet D. A user's guide for characterizing plasma membrane subdomains in living cells by spot variation fluorescence correlation spectroscopy. Methods Cell Biol 2017; 139:1-22. [PMID: 28215331 DOI: 10.1016/bs.mcb.2016.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Due to the intrinsic molecular Brownian agitation within plasma membrane and the vast diversity of membrane components, it is expected that the plasma membrane organization is highly heterogeneous with the formation of local complex multicomponent assemblies of lipids and proteins on different time scales. Still, deciphering this lateral organization on living cells and on the appropriate length and temporal scales has been challenging but is crucial to advance our knowledge on the biological function of the plasma membrane. Among the methodological developments based on biophotonics, the spot variation FCS (svFCS), a fluorescent correlation spectroscopy (FCS)-based method, has allowed the significant progress in the characterization of cell membrane lateral organization at the suboptical level, including to providing compelling evidence for the in vivo existence of lipid-dependent nanodomains. The aim of this chapter is to serve as a guide for setting and applying the svFCS methodology to study the plasma membrane of both adherent and nonadherent cell types.
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Affiliation(s)
- S Mailfert
- Centre d'Immunologie de Marseille Luminy, Aix Marseille Université, Inserm, CNRS, Marseille, France
| | - Y Hamon
- Centre d'Immunologie de Marseille Luminy, Aix Marseille Université, Inserm, CNRS, Marseille, France
| | - N Bertaux
- Institut Fresnel, Aix Marseille Université, Centrale Marseille, CNRS, Marseille, France
| | - H-T He
- Centre d'Immunologie de Marseille Luminy, Aix Marseille Université, Inserm, CNRS, Marseille, France
| | - D Marguet
- Centre d'Immunologie de Marseille Luminy, Aix Marseille Université, Inserm, CNRS, Marseille, France
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181
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Rodríguez G, Nargoli J, López A, Moyna G, Álvarez G, Fernández M, Osorio-Martínez CA, González M, Cerecetto H. Synthesis and in vivo proof of concept of a BODIPY-based fluorescent probe as a tracer for biodistribution studies of a new anti-Chagas agent. RSC Adv 2017. [DOI: 10.1039/c6ra27851e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A BODIPY-fluorophore based probe (1-BODIPY) for compound 1 was developed and investigated for its potential as in vivo tracer.
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Affiliation(s)
- Gonzalo Rodríguez
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
| | - Javier Nargoli
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
| | - Andrés López
- Departamento de Química del Litoral
- Universidad de la República
- Paysandú 60000
- Uruguay
| | - Guillermo Moyna
- Departamento de Química del Litoral
- Universidad de la República
- Paysandú 60000
- Uruguay
| | - Guzmán Álvarez
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
| | - Marcelo Fernández
- Laboratorio de Experimentación Animal
- Centro de Investigaciones Nucleares
- Facultad de Ciencias
- Universidad de la República
- Uruguay
| | - Carlos A. Osorio-Martínez
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
| | - Mercedes González
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
| | - Hugo Cerecetto
- Grupo de Química Medicinal
- Laboratorio de Química Orgánica
- Instituto de Química Biológica
- Facultad de Ciencias
- Universidad de la República
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182
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Moss FR, Boxer SG. Atomic Recombination in Dynamic Secondary Ion Mass Spectrometry Probes Distance in Lipid Assemblies: A Nanometer Chemical Ruler. J Am Chem Soc 2016; 138:16737-16744. [PMID: 27977192 DOI: 10.1021/jacs.6b10655] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The lateral organization of biological membranes is thought to take place on the nanometer length scale. However, this length scale and the dynamic nature of small lipid and protein domains have made characterization of such organization in biological membranes and model systems difficult. Here we introduce a new method for measuring the colocalization of lipids in monolayers and bilayers using stable isotope labeling. We take advantage of a process that occurs in dynamic SIMS called atomic recombination, in which atoms on different molecules combine to form diatomic ions that are detected with a NanoSIMS instrument. This process is highly sensitive to the distance between molecules. By measuring the efficiency of the formation of 13C15N- ions from 13C and 15N atoms on different lipid molecules, we measure variations in the lateral organization of bilayers even though these heterogeneities occur on a length scale of only a few nm, well below the diameter of the primary ion beam of the NanoSIMS instrument or even the best super-resolution fluorescence methods. Using this technique, we provide direct evidence for nanoscale phase separation in a model membrane, which may provide a better model for the organization of biological membranes than lipid mixtures with microscale phase separation. We expect this technique to be broadly applicable to any assembly where very short scale proximity is of interest or unknown, both in chemical and biological systems.
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Affiliation(s)
- Frank R Moss
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
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183
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Bordovsky SS, Wong CS, Bachand GD, Stachowiak JC, Sasaki DY. Engineering Lipid Structure for Recognition of the Liquid Ordered Membrane Phase. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12527-12533. [PMID: 27564087 DOI: 10.1021/acs.langmuir.6b02636] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The selective partitioning of lipid components in phase-separated membranes is essential for domain formation involved in cellular processes. Identifying and tracking the movement of lipids in cellular systems would be improved if we understood how to achieve selective affinity between fluorophore-labeled lipids and membrane assemblies. Here, we investigated the structure and chemistry of membrane lipids to evaluate lipid designs that partition to the liquid ordered (Lo) phase. A range of fluorophores at the headgroup position and lengths of PEG spacer between the lipid backbone and fluorophore were examined. On a lipid body with saturated palmityl or palmitoyl tails, we found that although the lipid tails can direct selective partitioning to the Lo phase through favorable packing interactions, headgroup hydrophobicity can override the partitioning behavior and direct the lipid to the disordered membrane phase (Ld). The PEG spacer can serve as a buffer to mute headgroup-membrane interactions and thus improve Lo phase partitioning, but its effect is limited with strongly hydrophobic fluorophore headgroups. We present a series of lipid designs leading to the development of novel fluorescently labeled lipids with selective affinity for the Lo phase.
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Affiliation(s)
- Stefan S Bordovsky
- Biotechnology and Bioengineering Department, Sandia National Laboratories , Livermore, California 94551, United States
- Department of Biomedical Engineering, The University of Texas at Austin , Austin, Texas 78705, United States
| | - Christopher S Wong
- Biotechnology and Bioengineering Department, Sandia National Laboratories , Livermore, California 94551, United States
| | - George D Bachand
- Nanosystems Synthesis/Analysis Department, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin , Austin, Texas 78705, United States
| | - Darryl Y Sasaki
- Biotechnology and Bioengineering Department, Sandia National Laboratories , Livermore, California 94551, United States
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184
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Chadda R, Robertson JL. Measuring Membrane Protein Dimerization Equilibrium in Lipid Bilayers by Single-Molecule Fluorescence Microscopy. Methods Enzymol 2016; 581:53-82. [PMID: 27793292 PMCID: PMC5568537 DOI: 10.1016/bs.mie.2016.08.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dimerization of membrane protein interfaces occurs during membrane protein folding and cell receptor signaling. Here, we summarize a method that allows for measurement of equilibrium dimerization reactions of membrane proteins in lipid bilayers, by measuring the Poisson distribution of subunit capture into liposomes by single-molecule photobleaching analysis. This strategy is grounded in the fact that given a comparable labeling efficiency, monomeric or dimeric forms of a membrane protein will give rise to distinctly different photobleaching probability distributions. These methods have been used to verify the dimer stoichiometry of the Fluc F- ion channel and the dimerization equilibrium constant of the ClC-ec1 Cl-/H+ antiporter in lipid bilayers. This approach can be applied to any membrane protein system provided it can be purified, fluorescently labeled in a quantitative manner, and verified to be correctly folded by functional assays, even if the structure is not yet known.
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Affiliation(s)
- R Chadda
- The University of Iowa, Iowa City, IA, United States
| | - J L Robertson
- The University of Iowa, Iowa City, IA, United States.
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185
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Gadok AK, Busch DJ, Ferrati S, Li B, Smyth HDC, Stachowiak JC. Connectosomes for Direct Molecular Delivery to the Cellular Cytoplasm. J Am Chem Soc 2016; 138:12833-12840. [DOI: 10.1021/jacs.6b05191] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Avinash K. Gadok
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - David J. Busch
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Silvia Ferrati
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Brian Li
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Hugh D. C. Smyth
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jeanne C. Stachowiak
- Department
of Biomedical Engineering, ‡College of Pharmacy,
and §Institute for Cellular
and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, United States
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186
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Kilchrist KV, Evans BC, Brophy CM, Duvall CL. Mechanism of Enhanced Cellular Uptake and Cytosolic Retention of MK2 Inhibitory Peptide Nano-polyplexes. Cell Mol Bioeng 2016; 9:368-381. [PMID: 27818713 PMCID: PMC5089375 DOI: 10.1007/s12195-016-0446-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/13/2016] [Indexed: 11/30/2022] Open
Abstract
Electrostatic complexation of a cationic MAPKAP kinase 2 inhibitory (MK2i) peptide with the anionic, pH-responsive polymer poly(propylacrylic acid) (PPAA) yields MK2i nano-polyplexes (MK2i-NPs) that significantly increase peptide uptake and intracellular retention. This study focused on elucidating the mechanism of MK2i-NP cellular uptake and intracellular trafficking in vascular smooth muscle cells. Small molecule inhibition of various endocytic pathways showed that MK2i-NP cellular uptake involves both macropinocytosis and clathrin mediated endocytosis, whereas the free peptide exclusively utilizes clathrin mediated endocytosis for cell entry. Scanning electron microscopy studies revealed that MK2i-NPs, but not free MK2i peptide, induce cellular membrane ruffling consistent with macropinocytosis. TEM confirmed that MK2i-NPs induce macropinosome formation and achieve MK2i endo-lysosomal escape and cytosolic delivery. Finally, a novel technique based on recruitment of Galectin-8-YFP was utilized to demonstrate that MK2i-NPs cause endosomal disruption within 30 minutes of uptake. These new insights on the relationship between NP physicochemical properties and cellular uptake and trafficking can potentially be applied to further optimize the MK2i-NP system and more broadly toward the rational engineering of nano-scale constructs for the intracellular delivery of biologic drugs.
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Affiliation(s)
- Kameron V Kilchrist
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37235, USA
| | - Brian C Evans
- Division of Vascular Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Colleen M Brophy
- Division of Vascular Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Veterans Affairs Medical Center, VA Tennessee Valley Healthcare System, Nashville TN 37212, USA
| | - Craig L. Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37235, USA
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187
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Chadda R, Krishnamani V, Mersch K, Wong J, Brimberry M, Chadda A, Kolmakova-Partensky L, Friedman LJ, Gelles J, Robertson JL. The dimerization equilibrium of a ClC Cl(-)/H(+) antiporter in lipid bilayers. eLife 2016; 5. [PMID: 27484630 PMCID: PMC5010387 DOI: 10.7554/elife.17438] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 07/29/2016] [Indexed: 12/20/2022] Open
Abstract
Interactions between membrane protein interfaces in lipid bilayers play an important role in membrane protein folding but quantification of the strength of these interactions has been challenging. Studying dimerization of ClC-type transporters offers a new approach to the problem, as individual subunits adopt a stable and functionally verifiable fold that constrains the system to two states - monomer or dimer. Here, we use single-molecule photobleaching analysis to measure the probability of ClC-ec1 subunit capture into liposomes during extrusion of large, multilamellar membranes. The capture statistics describe a monomer to dimer transition that is dependent on the subunit/lipid mole fraction density and follows an equilibrium dimerization isotherm. This allows for the measurement of the free energy of ClC-ec1 dimerization in lipid bilayers, revealing that it is one of the strongest membrane protein complexes measured so far, and introduces it as new type of dimerization model to investigate the physical forces that drive membrane protein association in membranes.
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Affiliation(s)
- Rahul Chadda
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
| | | | - Kacey Mersch
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
| | - Jason Wong
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.,Department of Natural Sciences, University of Bath, Bath, United Kingdom
| | - Marley Brimberry
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
| | - Ankita Chadda
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
| | | | - Larry J Friedman
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Janice L Robertson
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States
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188
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Lozano MM, Hovis JS, Moss FR, Boxer SG. Dynamic Reorganization and Correlation among Lipid Raft Components. J Am Chem Soc 2016; 138:9996-10001. [PMID: 27447959 DOI: 10.1021/jacs.6b05540] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lipid rafts are widely believed to be an essential organizational motif in cell membranes. However, direct evidence for interactions among lipid and/or protein components believed to be associated with rafts is quite limited owing, in part, to the small size and intrinsically dynamic interactions that lead to raft formation. Here, we exploit the single negative charge on the monosialoganglioside GM1, commonly associated with rafts, to create a gradient of GM1 in response to an electric field applied parallel to a patterned supported lipid bilayer. The composition of this gradient is visualized by imaging mass spectrometry using a NanoSIMS. Using this analytical method, added cholesterol and sphingomyelin, both neutral and not themselves displaced by the electric field, are observed to reorganize with GM1. This dynamic reorganization provides direct evidence for an attractive interaction among these raft components into some sort of cluster. At steady state we obtain an estimate for the composition of this cluster.
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Affiliation(s)
- Mónica M Lozano
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| | - Jennifer S Hovis
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| | - Frank R Moss
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
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189
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Mučibabić M, Apetri MM, Canters GW, Aartsma TJ. The effect of fluorescent labeling on α-synuclein fibril morphology. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1419-27. [PMID: 27475048 DOI: 10.1016/j.bbapap.2016.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 07/06/2016] [Accepted: 07/21/2016] [Indexed: 11/15/2022]
Abstract
The misfolding and aggregation of a small, natively unfolded protein α-synuclein (α-syn) is presumably an important factor in the development of Parkinson's disease. However, the mechanism of α-syn aggregation into amyloid fibrils and their morphology are not well understood. To elucidate the aggregation kinetics and the morphology of aggregates by the use of fluorescent techniques the protein needs to be suitably labeled. In this study, using atomic force microscopy, we demonstrate a significant effect of fluorescent labels on the α-syn fibrillization process. We studied in detail the morphology of α-syn aggregates as a function of the composition of mixtures of labeled and wild type (WT) α-syn in solution using different types of fluorescent dyes. Although the overall charge of the fluorophores we used and their chemical structure varied significantly, the morphology of α-syn fibrils changed in a similar way in all cases. The increase in the fraction of labeled α-syn in solution led to shortening of the fibrils as compared to those from WT-only α-syn, whereas the height of the fibrils remained mainly unaffected. The twisted fibril morphology observed in the WT and A140C α-syn mutant completely disappeared when the A140C α-syn mutant was 100% fluorescently labeled.
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Affiliation(s)
- M Mučibabić
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - M M Apetri
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - G W Canters
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - T J Aartsma
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands.
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190
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Zeng YS, Gao RC, Wu TW, Cho C, Tan KT. Fluorescent Probe Encapsulated in SNAP-Tag Protein Cavity To Eliminate Nonspecific Fluorescence and Increase Detection Sensitivity. Bioconjug Chem 2016; 27:1872-9. [DOI: 10.1021/acs.bioconjchem.6b00290] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yan-Syun Zeng
- Department of Chemistry, and ‡Frontier Research Center on Fundamental
and Applied
Sciences of Matters, National Tsing Hua University, 101 Sec.
2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
| | - Ruo-Cing Gao
- Department of Chemistry, and ‡Frontier Research Center on Fundamental
and Applied
Sciences of Matters, National Tsing Hua University, 101 Sec.
2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
| | - Ting-Wei Wu
- Department of Chemistry, and ‡Frontier Research Center on Fundamental
and Applied
Sciences of Matters, National Tsing Hua University, 101 Sec.
2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
| | - Chien Cho
- Department of Chemistry, and ‡Frontier Research Center on Fundamental
and Applied
Sciences of Matters, National Tsing Hua University, 101 Sec.
2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
| | - Kui-Thong Tan
- Department of Chemistry, and ‡Frontier Research Center on Fundamental
and Applied
Sciences of Matters, National Tsing Hua University, 101 Sec.
2, Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
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191
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Baranova N, Loose M. Single-molecule measurements to study polymerization dynamics of FtsZ-FtsA copolymers. Methods Cell Biol 2016; 137:355-370. [PMID: 28065316 DOI: 10.1016/bs.mcb.2016.03.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bacterial cytokinesis is commonly initiated by the Z-ring, a dynamic cytoskeletal structure that assembles at the site of division. Its primary component is FtsZ, a tubulin-like GTPase, that like its eukaryotic relative forms protein filaments in the presence of GTP. Since the discovery of the Z-ring 25years ago, various models for the role of FtsZ have been suggested. However, important information about the architecture and dynamics of FtsZ filaments during cytokinesis is still missing. One reason for this lack of knowledge has been the small size of bacteria, which has made it difficult to resolve the orientation and dynamics of individual FtsZ filaments in the Z-ring. While superresolution microscopy experiments have helped to gain more information about the organization of the Z-ring in the dividing cell, they were not yet able to elucidate a mechanism of how FtsZ filaments reorganize during assembly and disassembly of the Z-ring. In this chapter, we explain how to use an in vitro reconstitution approach to investigate the self-organization of FtsZ filaments recruited to a biomimetic lipid bilayer by its membrane anchor FtsA. We show how to perform single-molecule experiments to study the behavior of individual FtsZ monomers during the constant reorganization of the FtsZ-FtsA filament network. We describe how to analyze the dynamics of single molecules and explain why this information can help to shed light onto possible mechanism of Z-ring constriction. We believe that similar experimental approaches will be useful to study the mechanism of membrane-based polymerization of other cytoskeletal systems, not only from prokaryotic but also eukaryotic origin.
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Affiliation(s)
- N Baranova
- Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - M Loose
- Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria
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192
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Zhang L, Navaratna T, Thurber GM. A Helix-Stabilizing Linker Improves Subcutaneous Bioavailability of a Helical Peptide Independent of Linker Lipophilicity. Bioconjug Chem 2016; 27:1663-72. [PMID: 27327034 DOI: 10.1021/acs.bioconjchem.6b00209] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Stabilized peptides address several limitations to peptide-based imaging agents and therapeutics such as poor stability and low affinity due to conformational flexibility. There is also active research in developing these compounds for intracellular drug targeting, and significant efforts have been invested to determine the effects of helix stabilization on intracellular delivery. However, much less is known about the impact on other pharmacokinetic parameters such as plasma clearance and bioavailability. We investigated the effect of different fluorescent helix-stabilizing linkers with varying lipophilicity on subcutaneous (sc) bioavailability using the glucagon-like peptide-1 (GLP-1) receptor ligand exendin as a model system. The stabilized peptides showed significantly higher protease resistance and increased bioavailability independent of linker hydrophilicity, and all subcutaneously delivered conjugates were able to successfully target the islets of Langerhans with high specificity. The lipophilic peptide variants had slower absorption and plasma clearance than their respective hydrophilic conjugates, and the absolute bioavailability was also lower likely due to the longer residence times in the skin. Their ease and efficiency make double-click helix stabilization chemistries a useful tool for increasing the bioavailability of peptide therapeutics, many of which suffer from rapid in vivo protease degradation. Helix stabilization using linkers of varying lipophilicity can further control sc absorption and clearance rates to customize plasma pharmacokinetics.
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Affiliation(s)
- Liang Zhang
- Department of Chemical Engineering, and ‡Department of Biomedical Engineering University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Tejas Navaratna
- Department of Chemical Engineering, and ‡Department of Biomedical Engineering University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Greg M Thurber
- Department of Chemical Engineering, and ‡Department of Biomedical Engineering University of Michigan , Ann Arbor, Michigan 48109, United States
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193
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Bertrand R, Wolf A, Ivashchenko Y, Löhn M, Schäfer M, Brönstrup M, Gotthardt M, Derdau V, Plettenburg O. Synthesis and Characterization of a Promising Novel FFAR1/GPR40 Targeting Fluorescent Probe for β-Cell Imaging. ACS Chem Biol 2016; 11:1745-54. [PMID: 27115176 DOI: 10.1021/acschembio.5b00791] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Diabetes affects an increasing number of patients worldwide and is responsible for a significant rise in healthcare expenses. Imaging of β-cells bears the potential to contribute to an improved understanding, diagnosis, and development of new treatment options for diabetes. Here, we describe the first small molecule fluorescent probe targeting the free fatty acid receptor 1 (FFAR1/GPR40). This receptor is highly expressed on β-cells, and was up to now unexplored for imaging purposes. We designed a novel probe by facile modification of the selective and potent FFAR1 agonist TAK-875. Effective and specific binding of the probe was demonstrated using FFAR1 overexpressing cells. We also successfully labeled FFAR1 on MIN6 and INS1E cells, two widely used β-cell models, by applying an effective amplification protocol. Finally, we showed that the probe is capable of inducing insulin secretion in a glucose-dependent manner, thus demonstrating that functional activity of the probe was maintained. These results suggest that our probe represents a first important step to successful β-cell imaging by targeting FFAR1. The developed probe may prove to be particularly useful for in vitro and ex vivo studies of diabetic cellular and animal models to gain new insights into disease pathogenesis.
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Affiliation(s)
- Romain Bertrand
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
- Department
of Nuclear Medicine, Radboud UMC, Nijmegen 6525, The Netherlands
| | - Andrea Wolf
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
| | - Yuri Ivashchenko
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
| | - Matthias Löhn
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
| | - Matthias Schäfer
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
| | - Mark Brönstrup
- DSAR/Drug
Disposition, Sanofi GmbH, Frankfurt am Main 65926, Germany
- Helmholtz Centre
for Infection Research, Braunschweig 38124, Germany
| | - Martin Gotthardt
- Department
of Nuclear Medicine, Radboud UMC, Nijmegen 6525, The Netherlands
| | - Volker Derdau
- DSAR/Drug
Disposition, Sanofi GmbH, Frankfurt am Main 65926, Germany
| | - Oliver Plettenburg
- Diabetes Division, Research & Translational Medicine, Sanofi GmbH, Frankfurt am Main 65926, Germany
- Institute
of Medicinal Chemistry, Helmholtz Zentrum München, Ingolstaedter
Landstr. 1, Neuherberg 85764, Germany
- Leibniz University
Hannover, Schneiderberg 1 B, Hannover 30167, Germany
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194
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Mechanistic and quantitative insight into cell surface targeted molecular imaging agent design. Sci Rep 2016; 6:25424. [PMID: 27147293 PMCID: PMC4857130 DOI: 10.1038/srep25424] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 04/15/2016] [Indexed: 12/21/2022] Open
Abstract
Molecular imaging agent design involves simultaneously optimizing multiple probe properties. While several desired characteristics are straightforward, including high affinity and low non-specific background signal, in practice there are quantitative trade-offs between these properties. These include plasma clearance, where fast clearance lowers background signal but can reduce target uptake, and binding, where high affinity compounds sometimes suffer from lower stability or increased non-specific interactions. Further complicating probe development, many of the optimal parameters vary depending on both target tissue and imaging agent properties, making empirical approaches or previous experience difficult to translate. Here, we focus on low molecular weight compounds targeting extracellular receptors, which have some of the highest contrast values for imaging agents. We use a mechanistic approach to provide a quantitative framework for weighing trade-offs between molecules. Our results show that specific target uptake is well-described by quantitative simulations for a variety of targeting agents, whereas non-specific background signal is more difficult to predict. Two in vitro experimental methods for estimating background signal in vivo are compared – non-specific cellular uptake and plasma protein binding. Together, these data provide a quantitative method to guide probe design and focus animal work for more cost-effective and time-efficient development of molecular imaging agents.
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195
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Mapping the dynamics and nanoscale organization of synaptic adhesion proteins using monomeric streptavidin. Nat Commun 2016; 7:10773. [PMID: 26979420 PMCID: PMC4799371 DOI: 10.1038/ncomms10773] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 01/17/2016] [Indexed: 12/12/2022] Open
Abstract
The advent of super-resolution imaging (SRI) has created a need for optimized labelling strategies. We present a new method relying on fluorophore-conjugated monomeric streptavidin (mSA) to label membrane proteins carrying a short, enzymatically biotinylated tag, compatible with SRI techniques including uPAINT, STED and dSTORM. We demonstrate efficient and specific labelling of target proteins in confined intercellular and organotypic tissues, with reduced steric hindrance and no crosslinking compared with multivalent probes. We use mSA to decipher the dynamics and nanoscale organization of the synaptic adhesion molecules neurexin-1β, neuroligin-1 (Nlg1) and leucine-rich-repeat transmembrane protein 2 (LRRTM2) in a dual-colour configuration with GFP nanobody, and show that these proteins are diffusionally trapped at synapses where they form apposed trans-synaptic adhesive structures. Furthermore, Nlg1 is dynamic, disperse and sensitive to synaptic stimulation, whereas LRRTM2 is organized in compact and stable nanodomains. Thus, mSA is a versatile tool to image membrane proteins at high resolution in complex live environments, providing novel information about the nano-organization of biological structures. The advent of fluorescence-based super-resolution microscopy has created a need for labeling strategies relying on small probes that minimally perturb protein function. Here the authors describe a labeling method that reduces protein tag and label sizes, allowing for accurate protein targeting and measurements of protein dynamics in tight cellular spaces.
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196
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Lu T, Lin Z, Ren J, Yao P, Wang X, Wang Z, Zhang Q. The Non-Specific Binding of Fluorescent-Labeled MiRNAs on Cell Surface by Hydrophobic Interaction. PLoS One 2016; 11:e0149751. [PMID: 26930565 PMCID: PMC4773022 DOI: 10.1371/journal.pone.0149751] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 02/04/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND MicroRNAs are small noncoding RNAs about 22 nt long that play key roles in almost all biological processes and diseases. The fluorescent labeling and lipofection are two common methods for changing the levels and locating the position of cellular miRNAs. Despite many studies about the mechanism of DNA/RNA lipofection, little is known about the characteristics, mechanisms and specificity of lipofection of fluorescent-labeled miRNAs. METHODS AND RESULTS Therefore, miRNAs labeled with different fluorescent dyes were transfected into adherent and suspension cells using lipofection reagent. Then, the non-specific binding and its mechanism were investigated by flow cytometer and laser confocal microscopy. The results showed that miRNAs labeled with Cy5 (cyanine fluorescent dye) could firmly bind to the surface of adherent cells (Hela) and suspended cells (K562) even without lipofection reagent. The binding of miRNAs labeled with FAM (carboxyl fluorescein) to K562 cells was obvious, but it was not significant in Hela cells. After lipofectamine reagent was added, most of the fluorescently labeled miRNAs binding to the surface of Hela cells were transfected into intra-cell because of the high transfection efficiency, however, most of them were still binding to the surface of K562 cells. Moreover, the high-salt buffer which could destroy the electrostatic interactions did not affect the above-mentioned non-specific binding, but the organic solvent which could destroy the hydrophobic interactions eliminated it. CONCLUSIONS These results implied that the fluorescent-labeled miRNAs could non-specifically bind to the cell surface by hydrophobic interaction. It would lead to significant errors in the estimation of transfection efficiency only according to the cellular fluorescence intensity. Therefore, other methods to evaluate the transfection efficiency and more appropriate fluorescent dyes should be used according to the cell types for the accuracy of results.
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Affiliation(s)
- Ting Lu
- Division of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, China
| | - Zongwei Lin
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health; The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, China
| | - Jianwei Ren
- Health Division of Guard Bureau, General Staff Department of Chinese PLA, Beijing, China
| | - Peng Yao
- Traditional Chinese Medicine Department, Jinan Firefighting Hospital, Jinan, China
| | - Xiaowei Wang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health; The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, China
| | - Zhe Wang
- Division of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, China
| | - Qunye Zhang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health; The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, China
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197
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Zhu W, Varga Z, Silva JR. Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:3-17. [PMID: 26724572 DOI: 10.1016/j.pbiomolbio.2015.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/11/2015] [Accepted: 12/16/2015] [Indexed: 01/04/2023]
Abstract
Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models.
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Affiliation(s)
- Wandi Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Zoltan Varga
- MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Debrecen, Hungary
| | - Jonathan R Silva
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA.
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198
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Yoneda Y, Noji T, Katayama T, Mizutani N, Komori D, Nango M, Miyasaka H, Itoh S, Nagasawa Y, Dewa T. Extension of Light-Harvesting Ability of Photosynthetic Light-Harvesting Complex 2 (LH2) through Ultrafast Energy Transfer from Covalently Attached Artificial Chromophores. J Am Chem Soc 2015; 137:13121-9. [DOI: 10.1021/jacs.5b08508] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yusuke Yoneda
- Graduate
School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Tomoyasu Noji
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
- The OCU Advanced Research Institute for Natural Science & Technology (OCARINA), Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Tetsuro Katayama
- Institute
for NanoScience Design, Osaka University, Toyonaka, Osaka 560-8531, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Naoto Mizutani
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Daisuke Komori
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Mamoru Nango
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
- The OCU Advanced Research Institute for Natural Science & Technology (OCARINA), Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Hiroshi Miyasaka
- Graduate
School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Shigeru Itoh
- Center for
Gene Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Yutaka Nagasawa
- Graduate
School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Takehisa Dewa
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
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199
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Hu F, Chen Z, Zhang L, Shen Y, Wei L, Min W. Vibrational Imaging of Glucose Uptake Activity in Live Cells and Tissues by Stimulated Raman Scattering. Angew Chem Int Ed Engl 2015. [PMID: 26207979 DOI: 10.1002/anie.201502543] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Glucose is a ubiquitous energy source for most living organisms. Its uptake activity closely reflects cellular metabolic demand in various physiopathological conditions. Extensive efforts have been made to specifically image glucose uptake, such as with positron emission tomography, magnetic resonance imaging, and fluorescence microscopy, but all have limitations. A new platform to visualize glucose uptake activity in live cells and tissues is presented that involves performing stimulated Raman scattering on a novel glucose analogue labeled with a small alkyne moiety. Cancer cells with differing metabolic activities can be distinguished. Heterogeneous uptake patterns are observed with clear cell-cell variations in tumor xenograft tissues, neuronal culture, and mouse brain tissues. By offering the distinct advantage of optical resolution but without the undesirable influence of fluorophores, this method will facilitate the study of energy demands of living systems with subcellular resolution.
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Affiliation(s)
- Fanghao Hu
- Department of Chemistry, Columbia University, New York, NY 10027 (USA)
| | - Zhixing Chen
- Department of Chemistry, Columbia University, New York, NY 10027 (USA)
| | - Luyuan Zhang
- Department of Chemistry, Columbia University, New York, NY 10027 (USA)
| | - Yihui Shen
- Department of Chemistry, Columbia University, New York, NY 10027 (USA)
| | - Lu Wei
- Department of Chemistry, Columbia University, New York, NY 10027 (USA)
| | - Wei Min
- Department of Chemistry, Columbia University, New York, NY 10027 (USA). .,Kavli Institute for Brain Science, Columbia University, New York, NY 10027 (USA).
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200
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Hu F, Chen Z, Zhang L, Shen Y, Wei L, Min W. Vibrational Imaging of Glucose Uptake Activity in Live Cells and Tissues by Stimulated Raman Scattering. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201502543] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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