Physical Society Colloquium

Tuning by Pruning:
Exploiting Disorder to Design Biologically-Inspired Function

Andrea Liu

Department of Physics & Astronomy
University of Pennsylvania

The complexity of living systems poses a formidable challenge to physicists interested in biology. I will discuss one theoretical approach towards gaining possible insight into biological phenomena: to design simpler systems to exhibit similar phenomena. Allostery in a protein is a phenomenon in which a molecule binding locally to one site affects the ability of another molecule to bind at a second distant site. Inspired by the long-range coupled conformational changes that constitute allosteric function in proteins, we tune in ‘allostery’ into disordered mechanical networks by modifying the network architecture to control the local strain at one point in such a network in response to a strain applied elsewhere in the system. In another biological example, the vascular network in the brain contracts and dilates blood vessels in order to direct enhanced blood flow to multiple specific regions of the brain as it performs multiple tasks at once. We have designed flow networks to accomplish similar complex tasks. In both examples, we address a key question: what, precisely, are we tuning into the structure in order to accomplish the function? Surprisingly, we find that the structure/function relationship is not geometrical, but topological in nature.