Mathematical Biology and Ecology seminars take place in room L3 of the Mathematical Institute from 2-3pm on Fridays of odd weeks in full term. You can also join us afterwards for "tea and cakes" at 3pm in the Mathematical Institute Common Room.

A sister seminar series, organised by the Computational Biology Group, takes place in Room L3  of the Mathematical Institute from 2-3pm on Fridays of even weeks in full term.


24 January 2014
Prof Jaume Casademunt
We show that actin lamellar fragments extracted from cells, lacking the complex machinery for cell crawling, are spontaneously motile due solely to actin polymerization forces at the boundary. The motility mechanism is associated to a morphological instability similar to the problem of viscous fingering in Hele-Shaw cells, and does not require the existence of a global polarization of the actin gel, nor the presence of molecular motors, contrary to previous claims. We base our study on the formulation of a 2d free-boundary problem and exploit conformal mapping and center manifold projection techniques to prove the nonlinear instability of the center of mass, and to find an exact and simple relation between shape and velocity. A complex subcritical bifurcation scenario into traveling solutions is unfolded. With the help of high-precision numerical computation we show that the velocity is exponentially small close to the bifurcation points, implying a non-adiabatic mechanism. Examples of traveling solutions and their stability are studied numerically. Extensions of the approach to more realistic descriptions of actual biological systems are briefly discussed. REF: C. Blanch-Mercader and J. Casademunt, Physical Review Letters 110, 078102 (2013)
  • Mathematical Biology and Ecology Seminar