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Biological physics at APS 2009: How ants find food, cells lag, and bundles twist

by Andre on 18 March 2009

So far I’m very impressed by the level (and amount) of biological physics at the March meeting. There’s even more to be excited about this year than in previous years and I think it reflects physicists’ growing excitement about biology and a larger group of scientists realizing that they have things to talk about with physicists. It’s great to see.

One of the talks this morning was about how ants search when exposed to a new environment. When they find themselves in an empty, uniform, flat box, they seem to initially walk in a directed way away from the point of origin and then start a random walk to explore the new space. These experiments by William Baxter from Penn State have the appeal of simplicity, and they already yield interesting results. If one ant performs a random walk after a dash to a new area, what do two ants do? Do they avoid each other to make the search more efficient? So many great things to do. This also reminded me of a profile in em>Science (subscription required) last week that I wanted to write about anyway. If you have access, have a look. Awesome stuff.

There was also a nice talk by Elijah Bogart in Carl Franck’s group at Cornell. They’re using dicty as a model to study the lag phase of cell growth that precedes the exponential phase. Check out their paper in PRE and stay tuned for new results.

Finally, Greg Grason gave a beautiful talk on filament bundling and twisting. Bundles form when filaments are attracted to one another and this favours a hexagonal packing. In the absence of other factors, this should lead to infinite width bundles because the system could always reduce its free energy by adding another filament to the bundle. But, of course, there are other factors. One of those that Greg illustrated so nicely is that biological filaments are chiral, and that these chiral, twisted filaments would prefer a slight tilt when they pack together. This effect can lead to the formation of twisted bundles to accommodate this preference, but in this case, the filaments must bend and this has its own energy cost. Using mostly geometric arguments he was able to come to some neat conclusions about bundles. He and former postdoc advisor Robijn Bruinsma published some of this work in PRL and Greg has a new paper extending this work on the arXiv. This could be a link to the more recent paper, but I can’t check because I’ve been denied access to the arXiv using the convention center wireless:

Accesses from your site have triggered our automatic robot detection system.

Presumably the large concentration of physicists here has confused the server!

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