title: Single file diffusion into a semi-infinite tube.
abstract: We investigate single file diffusion (SFD) of large particles entering a semi-infinite tube, such as luminal diffusion of proteins into microtubules or flagella. While single-file effects have no impact on the evolution of particle density, we report significant single-file effects for individually tracked tracer particle motion. Both exact and approximate ordering statistics of particles entering semi-infinite tubes agree well with our stochastic simulations. Considering initially empty semi-infinite tubes, with particles entering at one end starting from an initial time t = 0, tracked particles are initially super-diffusive after entering the system, but asymptotically diffusive at later times. For finite time intervals, the ratio of the net displacement of individual single-file particles to the average displacement of untracked particles is reduced at early times and enhanced at later times. When each particle is numbered, from the first to enter (n = 1) to the most recent (n = N), we find good scaling collapse of this distance ratio for all n. Experimental techniques that track individual particles, or local groups of particles, such as photo-activation or photobleaching of fluorescently tagged proteins, should be able to observe these single-file effects. However, biological phenomena that depend on local concentration, such as flagellar extension or luminal enzymatic activity, should not exhibit single-file effects.
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2, Canada.
authors.forename: Spencer G
authors.initials: SG
authors.lastname: Farrell
authors.forename: Aidan I
authors.initials: AI
authors.lastname: Brown
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Rutenberg
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D008870:Microtubules / Q000737:chemistry*; D008956:Models, Chemical; D013269:Stochastic Processes