When Dan Rokhsar took an undergraduate molecular biology course in 1980, the subject made little sense to him because, he says, it was hard to see how the facts were interrelated. By contrast, physics seemed very orderly and he liked that order. He opted for a career in theoretical physics, and during his first five years on the faculty of the physics department at the University of California at Berkeley, he worked on mathematical modelling of the behaviour of materials. Five or so years ago, Rokhsar started to develop an interest in biology. He attended graduate courses in biology in his spare time, although his department was largely unaware of this.

Rokhsar found that much had changed since his original foray into biology and was quickly smitten, although at first “it was pretty clear that I didn't even know how to phrase the questions properly”, he says. He spent a summer working in a biology lab, again without officially informing his department, to gain experimental experience.

“In physics you can be a theorist, and that's a perfectly respectable way to make a living,” he says. “In biology, you don't have that kind of division of labour as much: everybody's a theorist, but your theories are typically much less mathematical.” Of the few colleagues he did tell, Rokhsar says that at least one suggested that, rather than becoming a student again, he should go to a biology professor and say: “I'm a physics professor. Tell me your difficult problems and let me help you solve them.” That doesn't work, says Rokhsar, because if you don't understand the context, nothing productive will come of it.

Rokhsar, now a professor of physics and biophysics at Berkeley, says that, having decided that he wanted to switch his research focus, he looked at three areas of study — the mechanisms of protein folding, modelling in neuroscience, and devising faster ways of analysing the vast amounts of data generated from DNA microarrays. “One of the advantages of being a theorist is that you can do a lot of different things. What they all have in common is that they use mathematical models to describe complicated systems, even though the systems themselves can be very different,” he says.

Rokhsar's connections with biology have been further consolidated in that he now sits on the Chancellor's Advisory Council on Biology, which oversees the entire biology programme on campus. He says the group has been instrumental in bringing in new faculty, some through joint appointments, working at the interface between the physical sciences and biology. The biophysics group itself is expected to grow by at least three people over the next five years or so.