Loop formation of microtubules during gliding at high density

Abstract

The microtubule cytoskeleton, including the associated proteins, forms a complex network essential to multiple cellular processes. Microtubule-associated motor proteins, such as kinesin-1, travel on microtubules to transport membrane bound vesicles across the crowded cell. Other motors, such as cytoplasmic dynein and kinesin-5, are used to organize the cytoskeleton during mitosis. In order to understand the self-organization processes of motors on microtubules, we performed filament-gliding assays with kinesin-1 motors bound to the cover glass with a high density of microtubules on the surface. To observe microtubule organization, 3% of the microtubules were fluorescently labeled to serve as tracers. We find that microtubules in these assays are not confined to two dimensions and can cross one other. This causes microtubules to align locally with a relatively short correlation length. At high density, this local alignment is enough to create 'intersections' of perpendicularly oriented groups of microtubules. These intersections create vortices that cause microtubules to form loops. We characterize the radius of curvature and time duration of the loops. These different behaviors give insight into how crowded conditions, such as those in the cell, might affect motor behavior and cytoskeleton organization.

Microtubule shuttles on kinesin-coated glass micro-wire tracks

“…However, inclusion of casein in our experimental procedure often suppressed binding of microtubules to the kinesin-treated surface, possibly due to a non-optimal casein solution. For the present work, we coated the glass surface densely with kinesin as an alternative way of surface passivation (Howard et al, 1989;Liu et al, 2011). Assuming that all kinesin molecules in solution within the flow cell attach to the glass surfaces, the kinesin surface density from the 4 µM kinesin solution is estimated to be 108,000 molecules per 1 µm 2 .…”

Device and programming abstractions for spatiotemporal control of active micro-particle swarms

“…[1][2][3][4][5][6][7][8][9] Controlled swarm motion may be employed to generate flows in lab-onchip devices in conjunction with digital microfluidics, [1][2][3][4][5][10][11][12] on-chip computation as previously explored with droplet logic and neural computation, 7,13 cargo delivery, 6,[14][15][16] and for selfassembly of nano-and microdevices. 8,10,15,[17][18][19][20] Algorithms for efficient control and programming of such swarms have been extensively studied via theory 20,21 and experiment in both synthetic 22 and natural systems, from motor proteins and filaments 23,24 to single-celled organisms 2,8,25,26 to insects 27 to macroscopic robots. 20,21,28 For microbiological swarms, "interactive biology" setups have enabled both professionals and non-experts to interact and experiment with swarm agents in real-time for research and edutainment purposes, e.g., through biology cloud experimentation laboratories, 29,…”

Microtubules, MAPs, and motor patterns

“…Here, we outline the experimental methods to create cell-like patterns in vitro based on a simple microtubule-gliding assay powered by kinesin-1 motor proteins (Liu, Tüzel, & Ross, 2011;Pringle et al, 2013). We systematically add more microtubules or other types of associated proteins to probe how the patterns change in increased complexity.…”