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  • 1
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    Mechanism of shape determination in motile cells (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-05-24
    Description: The shape of motile cells is determined by many dynamic processes spanning several orders of magnitude in space and time, from local polymerization of actin monomers at subsecond timescales to global, cell-scale geometry that may persist for hours. Understanding the mechanism of shape determination in cells has proved to be extremely challenging due to the numerous components involved and the complexity of their interactions. Here we harness the natural phenotypic variability in a large population of motile epithelial keratocytes from fish (Hypsophrys nicaraguensis) to reveal mechanisms of shape determination. We find that the cells inhabit a low-dimensional, highly correlated spectrum of possible functional states. We further show that a model of actin network treadmilling in an inextensible membrane bag can quantitatively recapitulate this spectrum and predict both cell shape and speed. Our model provides a simple biochemical and biophysical basis for the observed morphology and behaviour of motile cells.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877812/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877812/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keren, Kinneret -- Pincus, Zachary -- Allen, Greg M -- Barnhart, Erin L -- Marriott, Gerard -- Mogilner, Alex -- Theriot, Julie A -- U54 GM064346/GM/NIGMS NIH HHS/ -- U54 GM064346-099040/GM/NIGMS NIH HHS/ -- U54 GM64346/GM/NIGMS NIH HHS/ -- England -- Nature. 2008 May 22;453(7194):475-80. doi: 10.1038/nature06952.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Technion- Israel Institute of Technology, Haifa 32000, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18497816" target="_blank"〉PubMed〈/a〉
    Keywords: Actin Cytoskeleton/chemistry/metabolism ; Actins/chemistry/metabolism ; Animals ; Biophysical Phenomena ; Biophysics ; Cell Membrane/chemistry/metabolism ; Cell Movement/*physiology ; Cell Shape/*physiology ; Cells, Cultured ; *Cichlids ; Epithelial Cells/*cytology ; Models, Biological ; Pseudopodia/metabolism ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Sequence-specific molecular lithography on single DNA molecules (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-07-06
    Description: Recent advances in the realization of individual molecular-scale electronic devices emphasize the need for novel tools and concepts capable of assembling such devices into large-scale functional circuits. We demonstrated sequence-specific molecular lithography on substrate DNA molecules by harnessing homologous recombination by RecA protein. In a sequence-specific manner, we patterned the coating of DNA with metal, localized labeled molecular objects and grew metal islands on specific sites along the DNA substrate, and generated molecularly accurate stable DNA junctions for patterning the DNA substrate connectivity. In our molecular lithography, the information encoded in the DNA molecules replaces the masks used in conventional microelectronics, and the RecA protein serves as the resist. The molecular lithography works with high resolution over a broad range of length scales from nanometers to many micrometers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keren, Kinneret -- Krueger, Michael -- Gilad, Rachel -- Ben-Yoseph, Gdalyahu -- Sivan, Uri -- Braun, Erez -- New York, N.Y. -- Science. 2002 Jul 5;297(5578):72-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Solid State Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12098693" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies ; Biopolymers ; Biotin ; DNA/chemistry/genetics/*metabolism ; DNA, Single-Stranded/*metabolism ; Electric Conductivity ; *Electronics ; Glutaral ; Gold ; Microscopy, Atomic Force ; Microscopy, Electron, Scanning ; *Nanotechnology ; Nucleic Acid Hybridization ; Rec A Recombinases/chemistry/immunology/*metabolism ; Recombination, Genetic ; Silver ; Streptavidin ; Templates, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    DNA-templated carbon nanotube field-effect transistor (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-11-25
    Description: The combination of their electronic properties and dimensions makes carbon nanotubes ideal building blocks for molecular electronics. However, the advancement of carbon nanotube-based electronics requires assembly strategies that allow their precise localization and interconnection. Using a scheme based on recognition between molecular building blocks, we report the realization of a self-assembled carbon nanotube field-effect transistor operating at room temperature. A DNA scaffold molecule provides the address for precise localization of a semiconducting single-wall carbon nanotube as well as the template for the extended metallic wires contacting it.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keren, Kinneret -- Berman, Rotem S -- Buchstab, Evgeny -- Sivan, Uri -- Braun, Erez -- New York, N.Y. -- Science. 2003 Nov 21;302(5649):1380-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14631035" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteriophage lambda ; Biotin/chemistry ; *DNA/chemistry ; DNA, Single-Stranded/chemistry ; DNA, Viral/chemistry ; Gold ; Microscopy, Atomic Force ; Microscopy, Electron, Scanning ; *Nanotechnology ; *Nanotubes, Carbon ; Rec A Recombinases/metabolism ; Recombination, Genetic ; Streptavidin/chemistry ; *Transistors, Electronic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Myosin II contributes to cell-scale actin network treadmilling through network disassembly (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-05-21
    Description: Crawling locomotion of eukaryotic cells is achieved by a process dependent on the actin cytoskeleton: protrusion of the leading edge requires assembly of a network of actin filaments, which must be disassembled at the cell rear for sustained motility. Although ADF/cofilin proteins have been shown to contribute to actin disassembly, it is not clear how activity of these locally acting proteins could be coordinated over the distance scale of the whole cell. Here we show that non-muscle myosin II has a direct role in actin network disassembly in crawling cells. In fish keratocytes undergoing motility, myosin II is concentrated in regions at the rear with high rates of network disassembly. Activation of myosin II by ATP in detergent-extracted cytoskeletons results in rear-localized disassembly of the actin network. Inhibition of myosin II activity and stabilization of actin filaments synergistically impede cell motility, suggesting the existence of two disassembly pathways, one of which requires myosin II activity. Our results establish the importance of myosin II as an enzyme for actin network disassembly; we propose that gradual formation and reorganization of an actomyosin network provides an intrinsic destruction timer, enabling long-range coordination of actin network treadmilling in motile cells.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3662466/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3662466/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wilson, Cyrus A -- Tsuchida, Mark A -- Allen, Greg M -- Barnhart, Erin L -- Applegate, Kathryn T -- Yam, Patricia T -- Ji, Lin -- Keren, Kinneret -- Danuser, Gaudenz -- Theriot, Julie A -- R01AI067712/AI/NIAID NIH HHS/ -- T32GM007276/GM/NIGMS NIH HHS/ -- U01 GM067230/GM/NIGMS NIH HHS/ -- U01 GM067230-07/GM/NIGMS NIH HHS/ -- U01GM67230/GM/NIGMS NIH HHS/ -- U54GM64346/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2010 May 20;465(7296):373-7. doi: 10.1038/nature08994.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20485438" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/*chemistry/*metabolism ; Adenosine Triphosphate/pharmacology ; Animals ; Cell Movement/drug effects ; Cichlids ; Cytoskeleton/chemistry/drug effects/metabolism ; Depsipeptides/pharmacology ; Detergents ; Epithelial Cells/*cytology/*metabolism ; Heterocyclic Compounds with 4 or More Rings/pharmacology ; Myosin Type II/antagonists & inhibitors/*metabolism ; Protein Binding/drug effects ; Protein Transport
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
    Electronic Resource
    Electronic Resource
    The different effect of electron-electron interaction on the spectrum of atoms and quantum dots (2000)
    Springer
    The European physical journal 18 (2000), S. 311-318 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 72.20.Dp General theory, scattering mechanisms - 71.10.-w Theories and models of many electron systems - 31.10.+z Theory of electronic structure, electronic transitions, and chemical binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Though atoms and quantum dots typically contain a comparable number of electrons, the number of discrete levels resolved in spectroscopy experiments is very different for the two systems. In atoms, hundreds of levels are observed while in quantum dots that number is usually smaller than 10. In the present work, this difference is traced to the different confining potentials in these systems. In atoms, the soft confining potential leads to large spatial extent of the excited electron's wave function and hence to weak Coulomb interaction with the rest of the atomic electrons. The resulting level broadening is smaller than the single particle level spacing and decreases as the excitation energy is increased. In quantum dots, on the other hand, the sharp confining potential results in electron-electron scattering rates that grow rapidly with energy and fairly quickly exceed the approximately constant single particle level spacing. The number of discrete levels in quantum dots is hence limited by electron-electron interaction, whose effect is negligible in atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070063
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    Paper (German National Licenses)
    Fulltext
  • 6
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    Actin disassembly clock determines shape and speed of lamellipodial fragments (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-12-09
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Membrane tension leads the way (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-08-23
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Microscopics of Complexation between Long DNA Molecules and Positively Charged Colloids (2002)
    American Physical Society
    Details
    Publication Date: 2002-08-05
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 9
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    Actin disassembly clock determines shape and speed of lamellipodial fragments [Biophysics and Computational Biology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-12-21
    Description: A central challenge in motility research is to quantitatively understand how numerous molecular building blocks self-organize to achieve coherent shape and movement on cellular scales. A classic example of such self-organization is lamellipodial motility in which forward translocation is driven by a treadmilling actin network. Actin polymerization has been shown to be mechanically restrained by membrane tension in the lamellipodium. However, it remains unclear how membrane tension is determined, what is responsible for retraction and shaping of the rear boundary, and overall how actin-driven protrusion at the front is coordinated with retraction at the rear. To answer these questions, we utilize lamellipodial fragments from fish epithelial keratocytes which lack a cell body but retain the ability to crawl. The absence of the voluminous cell body in fragments simplifies the relation between lamellipodial geometry and cytoskeletal dynamics. We find that shape and speed are highly correlated over time within individual fragments, whereby faster crawling is accompanied by larger front-to-rear lamellipodial length. Furthermore, we find that the actin network density decays exponentially from front-to-rear indicating a constant net disassembly rate. These findings lead us to a simple hypothesis of a disassembly clock mechanism in which rear position is determined by where the actin network has disassembled enough for membrane tension to crush it and haul it forward. This model allows us to directly relate membrane tension with actin assembly and disassembly dynamics and elucidate the role of the cell membrane as a global mechanical regulator which coordinates protrusion and retraction.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Membrane tension leads the way [Commentary] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-08-31
    Description: Tension in the plasma membrane of adherent cells arises from the in-plane tension in the lipid bilayer, as well as from the adhesion between the membrane and the cytoskeleton (1). The membrane tension exerts a force along the cell boundary that affects all processes involving membrane deformations, including edge extension, endocytosis, and exocytosis. As such, membrane tension has been implicated as an important factor in a wide range of cellular phenomena, including cell migration, cytokinesis, mitosis, and intracellular trafficking. Despite its importance, little is known about the mechanisms by which membrane tension regulates these processes and in particular about the...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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