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Allen FI, De Teresa JM, Onoa B. Focused Helium Ion and Electron Beam-Induced Deposition of Organometallic Tips for Dynamic Atomic Force Microscopy of Biomolecules in Liquid. ACS Appl Mater Interfaces 2024; 16:4439-4448. [PMID: 38244049 DOI: 10.1021/acsami.3c16407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2024]
Abstract
We demonstrate the fabrication of sharp nanopillars of high aspect ratio onto specialized atomic force microscopy (AFM) microcantilevers and their use for high-speed AFM of DNA and nucleoproteins in liquid. The fabrication technique uses localized charged-particle-induced deposition with either a focused beam of helium ions or electrons in a helium ion microscope (HIM) or scanning electron microscope (SEM). This approach enables customized growth onto delicate substrates with nanometer-scale placement precision and in situ imaging of the final tip structures using the HIM or SEM. Tip radii of <10 nm are obtained and the underlying microcantilever remains intact. Instead of the more commonly used organic precursors employed for bio-AFM applications, we use an organometallic precursor (tungsten hexacarbonyl) resulting in tungsten-containing tips. Transmission electron microscopy reveals a thin layer of carbon on the tips. The interaction of the new tips with biological specimens is therefore likely very similar to that of standard carbonaceous tips, with the added benefit of robustness. A further advantage of the organometallic tips is that compared to carbonaceous tips they better withstand UV-ozone cleaning treatments to remove residual organic contaminants between experiments, which are inevitable during the scanning of soft biomolecules in liquid. Our tips can also be grown onto the blunted tips of previously used cantilevers, thus providing a means to recycle specialized cantilevers and restore their performance to the original manufacturer specifications. Finally, a focused helium ion beam milling technique to reduce the tip radii and thus further improve lateral spatial resolution in the AFM scans is demonstrated.
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Affiliation(s)
- Frances I Allen
- Department of Materials Science and Engineering, University of California, Berkeley, California 97420, United States
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 97420, United States
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 97420, United States
| | - José María De Teresa
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain
| | - Bibiana Onoa
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 97420, United States
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Onoa B, Díaz-Celis C, Cañari-Chumpitaz C, Lee A, Bustamante C. Real-Time Multistep Asymmetrical Disassembly of Nucleosomes and Chromatosomes Visualized by High-Speed Atomic Force Microscopy. ACS Cent Sci 2024; 10:122-137. [PMID: 38292612 PMCID: PMC10823521 DOI: 10.1021/acscentsci.3c00735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Revised: 10/30/2023] [Accepted: 11/30/2023] [Indexed: 02/01/2024]
Abstract
During replication, expression, and repair of the eukaryotic genome, cellular machinery must access the DNA wrapped around histone proteins forming nucleosomes. These octameric protein·DNA complexes are modular, dynamic, and flexible and unwrap or disassemble either spontaneously or by the action of molecular motors. Thus, the mechanism of formation and regulation of subnucleosomal intermediates has gained attention genome-wide because it controls DNA accessibility. Here, we imaged nucleosomes and their more compacted structure with the linker histone H1 (chromatosomes) using high-speed atomic force microscopy to visualize simultaneously the changes in the DNA and the histone core during their disassembly when deposited on mica. Furthermore, we trained a neural network and developed an automatic algorithm to track molecular structural changes in real time. Our results show that nucleosome disassembly is a sequential process involving asymmetrical stepwise dimer ejection events. The presence of H1 restricts DNA unwrapping, significantly increases the nucleosomal lifetime, and affects the pathway in which heterodimer asymmetrical dissociation occurs. We observe that tetrasomes are resilient to disassembly and that the tetramer core (H3·H4)2 can diffuse along the nucleosome positioning sequence. Tetrasome mobility might be critical to the proper assembly of nucleosomes and can be relevant during nucleosomal transcription, as tetrasomes survive RNA polymerase passage. These findings are relevant to understanding nucleosome intrinsic dynamics and their modification by DNA-processing enzymes.
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Affiliation(s)
- Bibiana Onoa
- Jason
L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences, QB3, University of California, Berkeley, California 94720, United States
| | - César Díaz-Celis
- Jason
L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences, QB3, University of California, Berkeley, California 94720, United States
| | - Cristhian Cañari-Chumpitaz
- Jason
L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences, QB3, University of California, Berkeley, California 94720, United States
| | - Antony Lee
- Laboratoire
Photonique Numérique et Nanosciences, LP2N UMR 5298, Université de Bordeaux, Institut d’Optique,
CNRS, F-33400 Talence, France
| | - Carlos Bustamante
- Jason
L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences, QB3, University of California, Berkeley, California 94720, United States
- Kavli
Energy Nanoscience Institute, University
of California, Berkeley, California 94720, United States
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Zhang M, Díaz-Celis C, Onoa B, Cañari-Chumpitaz C, Requejo KI, Liu J, Vien M, Nogales E, Ren G, Bustamante C. Molecular organization of the early stages of nucleosome phase separation visualized by cryo-electron tomography. Mol Cell 2022; 82:3000-3014.e9. [PMID: 35907400 DOI: 10.1016/j.molcel.2022.06.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 05/09/2022] [Accepted: 06/28/2022] [Indexed: 12/16/2022]
Abstract
It has been proposed that the intrinsic property of nucleosome arrays to undergo liquid-liquid phase separation (LLPS) in vitro is responsible for chromatin domain organization in vivo. However, understanding nucleosomal LLPS has been hindered by the challenge to characterize the structure of the resulting heterogeneous condensates. We used cryo-electron tomography and deep-learning-based 3D reconstruction/segmentation to determine the molecular organization of condensates at various stages of LLPS. We show that nucleosomal LLPS involves a two-step process: a spinodal decomposition process yielding irregular condensates, followed by their unfavorable conversion into more compact, spherical nuclei that grow into larger spherical aggregates through accretion of spinodal materials or by fusion with other spherical condensates. Histone H1 catalyzes more than 10-fold the spinodal-to-spherical conversion. We propose that this transition involves exposure of nucleosome hydrophobic surfaces causing modified inter-nucleosome interactions. These results suggest a physical mechanism by which chromatin may transition from interphase to metaphase structures.
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Affiliation(s)
- Meng Zhang
- Applied Science and Technology Graduate Group, University of California, Berkeley, CA, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA; The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - César Díaz-Celis
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
| | - Bibiana Onoa
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
| | | | - Katherinne I Requejo
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
| | - Jianfang Liu
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Michael Vien
- Department of Physics, University of California, Berkeley, CA, USA
| | - Eva Nogales
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Gang Ren
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Carlos Bustamante
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA, USA; Department of Chemistry, University of California, Berkeley, CA, USA; Department of Physics, University of California, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA; Kavli Energy Nanoscience Institute, University of California, Berkeley, CA, USA.
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Klass SH, Gleason JM, Omole AO, Onoa B, Bustamante CJ, Francis MB. Preparation of Bioderived and Biodegradable Surfactants Based on an Intrinsically Disordered Protein Sequence. Biomacromolecules 2022; 23:1462-1470. [PMID: 35238203 DOI: 10.1021/acs.biomac.2c00051] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Surfactants, block copolymers, and other types of micellar systems are used in a wide variety of biomedical and industrial processes. However, most commonly used surfactants are synthetically derived and pose environmental and toxicological concerns throughout their product life cycle. Because of this, bioderived and biodegradable surfactants are promising alternatives. For biosurfactants to be implemented industrially, they need to be produced on a large scale and also have tailorable properties that match those afforded by the polymerization of synthetic surfactants. In this paper, a scalable and versatile production method for biosurfactants based on a hydrophilic intrinsically disordered protein (IDP) sequence with a genetically engineered hydrophobic domain is used to study variables that impact their physicochemical and self-assembling properties. These amphiphilic sequences were found to self-assemble into micelles over a broad range of temperatures, pH values, and ionic strengths. To investigate the role of the IDP hydrophilic domain on self-assembly, variants with increased overall charges and systematically decreased IDP domain lengths were produced and examined for their sizes, morphologies, and critical micelle concentrations (CMCs). The results of these studies indicate that decreasing the length of the IDP domain and consequently the molecular weight and hydrophilic fraction leads to smaller micelles. In addition, significantly increasing the amount of charged residues in the hydrophilic IDP domain results in micelles of similar sizes but with higher CMC values. This represents an initial step in developing a quantitative model for the future engineering of biosurfactants based on this IDP sequence.
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Affiliation(s)
- Sarah H Klass
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Jamie M Gleason
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Anthony O Omole
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Bibiana Onoa
- Howard Hughes Medical Institute, University of California, Berkeley, California 94720, United States
| | - Carlos J Bustamante
- Howard Hughes Medical Institute, University of California, Berkeley, California 94720, United States.,Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, United States.,Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Matthew B Francis
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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5
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Clauss ZS, Wardzala CL, Schlirf AE, Wright NS, Saini SS, Onoa B, Bustamante C, Kramer JR. Tunable, biodegradable grafting-from glycopolypeptide bottlebrush polymers. Nat Commun 2021; 12:6472. [PMID: 34753949 PMCID: PMC8578664 DOI: 10.1038/s41467-021-26808-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 10/01/2021] [Indexed: 11/09/2022] Open
Abstract
The cellular glycocalyx and extracellular matrix are rich in glycoproteins and proteoglycans that play essential physical and biochemical roles in all life. Synthetic mimics of these natural bottlebrush polymers have wide applications in biomedicine, yet preparation has been challenged by their high grafting and glycosylation densities. Using one-pot dual-catalysis polymerization of glycan-bearing α-amino acid N-carboxyanhydrides, we report grafting-from glycopolypeptide brushes. The materials are chemically and conformationally tunable where backbone and sidechain lengths were precisely altered, grafting density modulated up to 100%, and glycan density and identity tuned by monomer feed ratios. The glycobrushes are composed entirely of sugars and amino acids, are non-toxic to cells, and are degradable by natural proteases. Inspired by native lipid-anchored proteoglycans, cholesterol-modified glycobrushes were displayed on the surface of live human cells. Our materials overcome long-standing challenges in glycobrush polymer synthesis and offer new opportunities to examine glycan presentation and multivalency from chemically defined scaffolds. Synthetic mimics of glycoproteins and proteoglycans have wide applications in biomedicine, yet preparation has been challenged by their high grafting and glycosylation densities. Here the authors show one-pot dual-catalysis polymerization of glycan-bearing α-amino acid N-carboxyanhydrides to form glycopolypeptide brushes.
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Affiliation(s)
- Zachary S Clauss
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA
| | - Casia L Wardzala
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA
| | - Austin E Schlirf
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA
| | - Nathaniel S Wright
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA
| | - Simranpreet S Saini
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA
| | - Bibiana Onoa
- Howard Hughes Medical Institute University of California Berkeley, Berkeley, CA, 94720, USA
| | - Carlos Bustamante
- Howard Hughes Medical Institute University of California Berkeley, Berkeley, CA, 94720, USA.,Department of Chemistry, University of California Berkeley, Berkeley, CA, 94720, USA.,Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.,Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Jessica R Kramer
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, 84102, USA. .,Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, 84102, USA.
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6
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Onoa B, Fukuda S, Iwai M, Bustamante C, Niyogi KK. Atomic Force Microscopy Visualizes Mobility of Photosynthetic Proteins in Grana Thylakoid Membranes. Biophys J 2020; 118:1876-1886. [PMID: 32224302 PMCID: PMC7175462 DOI: 10.1016/j.bpj.2020.02.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 02/10/2020] [Accepted: 02/28/2020] [Indexed: 12/19/2022] Open
Abstract
Thylakoid membranes in chloroplasts contain photosynthetic protein complexes that convert light energy into chemical energy. Photosynthetic protein complexes are considered to undergo structural reorganization to maintain the efficiency of photochemical reactions. A detailed description of the mobility of photosynthetic complexes in real time is necessary to understand how macromolecular organization of the membrane is altered by environmental fluctuations. Here, we used high-speed atomic force microscopy to visualize and characterize the in situ mobility of individual protein complexes in grana thylakoid membranes isolated from Spinacia oleracea. Our observations reveal that these membranes can harbor complexes with at least two distinctive classes of mobility. A large fraction of grana membranes contained proteins with quasistatic mobility exhibiting molecular displacements smaller than 10 nm2. In the remaining fraction, the protein mobility is variable with molecular displacements of up to 100 nm2. This visualization at high spatiotemporal resolution enabled us to estimate an average diffusion coefficient of ∼1 nm2 s-1. Interestingly, both confined and Brownian diffusion models could describe the protein mobility of the second group of membranes. We also provide the first direct evidence, to our knowledge, of rotational diffusion of photosynthetic complexes. The rotational diffusion of photosynthetic complexes could be an adaptive response to the high protein density in the membrane to guarantee the efficiency of electron transfer reactions. This characterization of the mobility of individual photosynthetic complexes in grana membranes establishes a foundation that could be adapted to study the dynamics of the complexes inside intact and photosynthetically functional thylakoid membranes to be able to understand its structural responses to diverse environmental fluctuations.
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Affiliation(s)
- Bibiana Onoa
- Howard Hughes Medical Institute, University of California, Berkeley, California.
| | - Shingo Fukuda
- Howard Hughes Medical Institute, University of California, Berkeley, California
| | - Masakazu Iwai
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California; Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Carlos Bustamante
- Howard Hughes Medical Institute, University of California, Berkeley, California; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California; Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, California; Department of Molecular and Cell Biology, University of California, Berkeley, California; Department of Physics, University of California, Berkeley, California; Kavli Energy NanoScience Institute, Lawrence Berkeley National Laboratory, University of California, Berkeley, California
| | - Krishna K Niyogi
- Howard Hughes Medical Institute, University of California, Berkeley, California; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California; Department of Plant and Microbial Biology, University of California, Berkeley, California.
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7
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Onoa B, Fukuda S, Iwai M, Niyogi KK, Bustamante C. Dynamic Characterization of Photosynthetic Proteins on Thylakoid Membranes by High-Speed AFM. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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8
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Onoa B, Schneider AR, Brooks MD, Grob P, Nogales E, Geissler PL, Niyogi KK, Bustamante C. Atomic force microscopy of photosystem II and its unit cell clustering quantitatively delineate the mesoscale variability in Arabidopsis thylakoids. PLoS One 2014; 9:e101470. [PMID: 25007326 PMCID: PMC4090009 DOI: 10.1371/journal.pone.0101470] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/06/2014] [Indexed: 11/25/2022] Open
Abstract
Photoautotrophic organisms efficiently regulate absorption of light energy to sustain photochemistry while promoting photoprotection. Photoprotection is achieved in part by triggering a series of dissipative processes termed non-photochemical quenching (NPQ), which depend on the re-organization of photosystem (PS) II supercomplexes in thylakoid membranes. Using atomic force microscopy, we characterized the structural attributes of grana thylakoids from Arabidopsis thaliana to correlate differences in PSII organization with the role of SOQ1, a recently discovered thylakoid protein that prevents formation of a slowly reversible NPQ state. We developed a statistical image analysis suite to discriminate disordered from crystalline particles and classify crystalline arrays according to their unit cell properties. Through detailed analysis of the local organization of PSII supercomplexes in ordered and disordered phases, we found evidence that interactions among light-harvesting antenna complexes are weakened in the absence of SOQ1, inducing protein rearrangements that favor larger separations between PSII complexes in the majority (disordered) phase and reshaping the PSII crystallization landscape. The features we observe are distinct from known protein rearrangements associated with NPQ, providing further support for a role of SOQ1 in a novel NPQ pathway. The particle clustering and unit cell methodology developed here is generalizable to multiple types of microscopy and will enable unbiased analysis and comparison of large data sets.
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Affiliation(s)
- Bibiana Onoa
- California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America
| | - Anna R. Schneider
- Biophysics Graduate Group, University of California, Berkeley, California, United States of America
| | - Matthew D. Brooks
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Patricia Grob
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
| | - Eva Nogales
- California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Phillip L. Geissler
- California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America
- Biophysics Graduate Group, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- Department of Chemistry, University of California, Berkeley, California, United States of America
| | - Krishna K. Niyogi
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Carlos Bustamante
- California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Physics, University of California, Berkeley, California, United States of America
- Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- * E-mail:
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9
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Anantharam A, Onoa B, Edwards RH, Holz RW, Axelrod D. Localized topological changes of the plasma membrane upon exocytosis visualized by polarized TIRFM. J Biophys Biochem Cytol 2012. [PMCID: PMC3341163 DOI: 10.1083/jcb.2009080101973c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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10
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Anantharam A, Onoa B, Edwards RH, Holz RW, Axelrod D. Localized topological changes of the plasma membrane upon exocytosis visualized by polarized TIRFM. ACTA ACUST UNITED AC 2010; 188:415-28. [PMID: 20142424 PMCID: PMC2819686 DOI: 10.1083/jcb.200908010] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Imaging of individual secretory granules reveals how exocytosis curves the membrane. Total internal reflection fluorescence microscopy (TIRFM) images the plasma membrane–cytosol interface and has allowed insights into the behavior of individual secretory granules before and during exocytosis. Much less is known about the dynamics of the other partner in exocytosis, the plasma membrane. In this study, we report the implementation of a TIRFM-based polarization technique to detect rapid submicrometer changes in plasma membrane topology as a result of exocytosis. A theoretical analysis of the technique is presented together with image simulations of predicted topologies of the postfusion granule membrane–plasma membrane complex. Experiments on diI-stained bovine adrenal chromaffin cells using polarized TIRFM demonstrate rapid and varied submicrometer changes in plasma membrane topology at sites of exocytosis that occur immediately upon fusion. We provide direct evidence for a persistent curvature in the exocytotic region that is altered by inhibition of dynamin guanosine triphosphatase activity and is temporally distinct from endocytosis measured by VMAT2-pHluorin.
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Affiliation(s)
- Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA.
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Anantharam A, Onoa B, Edwards RH, Holz RW, Axelrod D. Localized topological changes of the plasma membrane upon exocytosis visualized by polarized TIRFM. J Gen Physiol 2010. [DOI: 10.1085/jgp1353oia3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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12
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Onoa B, Li H, Elias LA, Edwards RH. Vesicular Monoamine and Glutamate Transporters Select Distinct Synaptic Vesicle Recycling Pathways. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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13
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Abstract
Single-molecule studies of RNA folding and unfolding are providing impressive details of the intermediates that occur and their rates of interconversion. The folding and unfolding of RNA are controlled by varying the concentration of magnesium ions and measuring fluorescence energy transfer, or by applying force to the RNA and measuring the end-to-end distance. The hierarchical nature of RNA folding - first secondary structure, then tertiary structure - makes the process susceptible to analysis and prediction.
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Affiliation(s)
- Bibiana Onoa
- DuPont Central Research & Development Experimental Station, PO Box 80328, Wilmington, Delaware 19880-0328, USA.
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Abstract
Mechanical unfolding trajectories for single molecules of the Tetrahymena thermophila ribozyme display eight intermediates corresponding to discrete kinetic barriers that oppose mechanical unfolding with lifetimes of seconds and rupture forces between 10 and 30 piconewtons. Barriers are magnesium dependent and correspond to known intra- and interdomain interactions. Several barrier structures are "brittle," breakage requiring high forces but small (1 to 3 nanometers) deformations. Barrier crossing is stochastic, leading to variable unfolding paths. The response of complex RNA structures to locally applied mechanical forces may be analogous to the responses of RNA during translation, messenger RNA export from the nucleus, and viral replication.
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Affiliation(s)
- Bibiana Onoa
- Department of Physics and Department of Molecular and Cell Biology and Howard Hughes Medical Institute
| | | | - Jan Liphardt
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Steven B. Smith
- Department of Physics and Department of Molecular and Cell Biology and Howard Hughes Medical Institute
| | - Ignacio Tinoco
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Carlos Bustamante
- Department of Physics and Department of Molecular and Cell Biology and Howard Hughes Medical Institute
- Biophysics Graduate Group
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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15
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Abstract
Here we use mechanical force to induce the unfolding and refolding of single RNA molecules: a simple RNA hairpin, a molecule containing a three-helix junction, and the P5abc domain of the Tetrahymena thermophila ribozyme. All three molecules (P5abc only in the absence of Mg2+) can be mechanically unfolded at equilibrium, and when kept at constant force within a critical force range, are bi-stable and hop between folded and unfolded states. We determine the force-dependent equilibrium constants for folding/unfolding these single RNA molecules and the positions of their transition states along the reaction coordinate.
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Affiliation(s)
- J Liphardt
- Department of Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA.
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