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@ARTICLE{Head:19042,
      author       = {Head, D.A. and Briels, W.J. and Gompper, G.},
      title        = {{S}pindles and active vortices in a model of confined
                      filament-motor mixtures},
      journal      = {BMC Biophysics},
      volume       = {4},
      issn         = {2046-1682},
      address      = {London},
      publisher    = {BioMed Central},
      reportid     = {PreJuSER-19042},
      year         = {2011},
      note         = {Financial support of this project by the European Network
                      of Excellence "SoftComp" through a joint postdoctoral
                      fellowship for DAH is gratefully acknowledged.},
      abstract     = {Robust self-organization of subcellular structures is a key
                      principle governing the dynamics and evolution of cellular
                      life. In fission yeast cells undergoing division, the
                      mitotic spindle spontaneously emerges from the interaction
                      of microtubules, motor proteins and the confining cell
                      walls, and asters and vortices have been observed to
                      self-assemble in quasi-two dimensional microtubule-kinesin
                      assays. There is no clear microscopic picture of the role of
                      the active motors driving this pattern formation, and the
                      relevance of continuum modeling to filament-scale structures
                      remains uncertain.Here we present results of numerical
                      simulations of a discrete filament-motor protein model
                      confined to a pressurised cylindrical box. Stable spindles,
                      nematic configurations, asters and high-density semi-asters
                      spontaneously emerge, the latter pair having also been
                      observed in cytosol confined within emulsion droplets. State
                      diagrams are presented delineating each stationary state as
                      the pressure, motor speed and motor density are varied. We
                      further highlight a parameter regime where vortices form
                      exhibiting collective rotation of all filaments, but have a
                      finite life-time before contracting to a semi-aster.
                      Quantifying the distribution of life-times suggests this
                      contraction is a Poisson process. Equivalent systems with
                      fixed volume exhibit persistent vortices with stochastic
                      switching in the direction of rotation, with switching times
                      obeying similar statistics to contraction times in
                      pressurised systems. Furthermore, we show that increasing
                      the detachment rate of motors from filament plus-ends can
                      both destroy vortices and turn some asters into vortices.We
                      have shown that discrete filament-motor protein models
                      provide new insights into the stationary and dynamical
                      behavior of active gels and subcellular structures, because
                      many phenomena occur on the length-scale of single
                      filaments. Based on our findings, we argue the need for a
                      deeper understanding of the microscopic activities
                      underpinning macroscopic self-organization in active gels
                      and urge further experiments to help bridge these lengths.},
      keywords     = {J (WoSType)},
      cin          = {IAS-2 / ICS-2},
      ddc          = {570},
      cid          = {I:(DE-Juel1)IAS-2-20090406 / I:(DE-Juel1)ICS-2-20110106},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung},
      pid          = {G:(DE-Juel1)FUEK505},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:22087580},
      pmc          = {pmc:PMC3253673},
      UT           = {WOS:000299412000001},
      doi          = {10.1186/2046-1682-4-18},
      url          = {https://juser.fz-juelich.de/record/19042},
}