Department of Physics and the
Over the years my colleagues and I have been interested in a wide variety of problems at the interface of physics and biology. These are links to our work in several different (not always mutually exclusive) areas. If you follow the links youÕll find selected papers with (evolving) commentaries in each category, as well as further links to downloadable versions of most of the papers; see also the full publication list.
Optimization. Much of my work is motivated by the (perhaps dangerously mystical) idea that biological systems may be optimized for particular functions, operating at or near some fundamental physical limits to their performance. Often this idea stays comfortably in the background, but sometimes itÕs been possible to confront the issue head on. This set of papers explores the physical limits to various biological processes, develops optimization principles that predict how biological systems must work if they are going to reach these limits, and assesses the experimental evidence for these predictions.
The fly papers. I have had a long theory/experiment collaboration with Rob de Ruyter van Steveninck (now at Indiana University) looking at the flyÕs visual system as an example of several general issues in neural coding and computation, especially the ideas of optimization. This is a guide to some of our work together, as well as closely related things that we have done separately.
More about neural coding. Throughout the nervous system of almost all animals, continuous signals are encoded in sequences of identical pulses called action potentials or spikes. As a physicist my hope is that there are some general principles that govern the structure of this code. Although the fly has been a testing ground for many of our ideas about the neural code, the hypothesis that there are general principles can be tested only by looking at many different systems. Here youÕll find a sampling of collaborative efforts with my experimentalist friends that explore these possibilities, together with some theoretical papers that (hopefully) address issues that go beyond the details of any one system.
Protein dynamics and function. Although I havenÕt looked at these problems much in the past ten years, for quite some time my collaborators and I were interested in the dynamics of biological molecules and the way in which these dynamics connect to their functions. One particular obsession was with the interplay between classical and quantum dynamics in these large molecules.
Dynamics and computation in single cells and biochemical networks. Single cells have to solve many problems of computation and signal processing at the biochemical level. Many of the problems they face are analogous to those faced by the brain, but the physical constraints are even clearer. In particular, many critical phenomena of life depend on shockingly small numbers of molecules. How do cells achieve reliable function in the presence of the inevitable fluctuations associated with these small numbers? How much of the intricate machinery of the cell can be understood as a principled solution to these problems of noise and computation? These are some of the questions we have been exploring, both theoretically and more recently in connection with specific experiments.