Motor proteins that walk on biological filaments perform important jobs in cells. How exactly do these motors distribute along the filaments? This image shows the phase plane of a model of motors that move on antiparallel microtubule overlaps and switch between filaments. At sufficiently high switching rate, new transition points (labeled TP) appear in the phase plane, which leads to a new phase with multiple domain walls. The phase-plane approach brings a new set of mathematical tools to the study of multi-lane motor problems.
Bipolar mitotic spindles form from a monopolar initial condition in a fundamental construction problem. Microtubules, motors, and cross-linkers are important for bipolarity, but the mechanisms necessary and sufficient for spindle assembly remain unknown. We developed a physical model that exhibits de novo bipolar spindle formation that agrees quantitatively with our experiments in fission yeast, thereby establishing a minimal system with which to interrogate collective self-assembly. This work was published in Science Advances.
In many biological systems, such as proteins in the nuclear pore complex, proteins in cells, and membrane proteins and lipids in the presence of lipid domains, particles diffuse in a crowded environment. Crowding can cause a particle's diffusion to be anomalous, leading to a mean squared displacement that is not linear in time. We studied a model of the dynamics of tracer particles which can bind to soft obstacles, and contrasted sticky (no bound motion) and slippery (motion while bound) obstacles.
Betterton group 2018
Members of the Biophysics group went to the mountains for hiking and the group research retreat.
Torque due to crosslinkers can promote or oppose antiparallel alignment of the MTs, because the magnitude and direction of the torque depends on MT length and the crossing angle. By using the Langevin equations for translational and rotational motion of filaments we can derive a system of integro-differential equations for the length and angle between microtubule bundles.
In-cell NMR in S. cerevisiae is a novel way of looking at disordered proteins in a crowded cellular environment. The methodology has been developed here, which could be broadly applicable to other protein systems. In an example, the non-specific interactions of the FG Nup construct, FSFG-K, with the cytoplasm is similar to previously found bacterial interactions using NMR relaxation techniques. This work was recently published in Biophysical Journal.