title: Optimality of Spatially Inhomogeneous Search Strategies.
abstract: We consider random search processes alternating stochastically between diffusion and ballistic motion, in which the distribution function of ballistic motion directions varies from point to point in space. The specific space dependence of the directional distribution together with the switching rates between the two modes of motion establishes a spatially inhomogeneous search strategy. We show that the mean first passage times for several standard search problems-narrow escape, reaction partner finding, reaction escape-can be minimized with a directional distribution that is reminiscent of the spatial organization of the cytoskeleton filaments of cells with a centrosome: radial ballistic transport from the center to the periphery and back, and ballistic transport in random directions within a concentric shell of thickness Δ_{opt} along the domain boundary. The results suggest that living cells realize efficient search strategies for various intracellular transport problems economically through a spatial cytoskeleton organization that involves radial microtubules in the central region and only a narrow actin cortex rather than a cell body filled with randomly oriented actin filaments.
authors.affiliation: Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Schwarz
authors.affiliation: Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Schröder
authors.affiliation: Biophysics, CIPMM, Saarland University, 66421 Homburg, Germany.
authors.forename: Bin
authors.initials: B
authors.lastname: Qu
authors.affiliation: Biophysics, CIPMM, Saarland University, 66421 Homburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Hoth
authors.affiliation: Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Rieger
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins; D001692:Biological Transport; D003599:Cytoskeleton / Q000737:chemistry*; D004058:Diffusion; D008870:Microtubules; D009038:Motion
chemical_list: D000199:Actins