Biological Physics: Energy, Information, Life , Philip Nelson (with the assistance of Marko Radosavljević and Sarina Bromberg ) W. H. Freeman, New York, 2003. $92.00 (598 pp.). ISBN 0-7167-4372-8
These days, physics departments are going through agonizing introspection about whether to include biology in the undergraduate physics curriculum. To some extent, the idea has been forced on them by the revolutionary changes happening in biology. In Biological Physics: Energy, Information, Life, Philip Nelson, a professor of physics at the University of Pennsylvania in Philadelphia, wrote in the book’s introduction addressed to instructors: “A few years ago my department asked their undergraduate students what they needed but were not getting from us. One of the answers was a course on biological physics. Our students could not help noticing all the exciting articles in The New York Times, all the cover articles in Physics Today, and so on. They wanted a piece of the action.”
Nelson’s decision to focus in his book on biological physics as opposed to biophysics reflects a long-felt division between physicists and biologists. In 1949, Max Delbrück stated the following: “Biology is a very interesting field [because of] the vastness of its structure and the extraordinary variety of strange facts, but to the physicist it is also a depressing subject because the analysis seems to have stalled around in a semi-descriptive manner without noticeably progressing towards a radical physical explanation…. We are not yet at the point where we are presented with clear paradoxes.”
Delbrück’s point of view is still shared by quite a few physicists today (see, for instance, commentary by Robert B. Laughlin in Physics Today, Physics Today 0031-9228 55 12 2002 10 https://doi.org/10.1063/1.1537890 December 2002, page 10 ). Nevertheless, the desire of the undergraduate physics students at Nelson’s university to have a biological physics class reflects the thoughts of Edward O. Wilson, who saw the significant impact the discovery of the structure of DNA had on our perception of how the world works. “Reaching beyond the transformation of genetics, it injected into all of biology a new faith in reductionism,” Wilson wrote in Naturalist (Island Press, 1994). “The most complex of processes, the discovery implied, might be simpler than we had thought.”
One way in which physicists have sought a compromise with physics and biology is by distinguishing the terms “biological physics” and “biophysics.” According to researchers Hans Frauenfelder, Peter Wolynes, and Robert Austin in Biological Physics: Third International Symposium (AIP Press/Springer-Verlag, 1999), the biological physicist “asks not what physics can do for biology, but what biology can do for physics … and defines biological physics as the field where one extracts interesting physics from biological systems. Much like the terms physical chemistry and chemical physics, the terminological differences represent only psychological style and current attitude; the same person at different times could be thinking as a biophysicist or as a biological physicist.”
So, how can physicists climb onto the biology band wagon? The difficulties of doing this are reflected in problems faced by physicists who wish to contribute to research at the forefront of biology. Because problems in biology come from the experimental study of living systems, physicists can only decide on which problems to work on by retraining themselves as biologists, which many distinguished scientists such as Delbrück, Francis Crick, and Walter Gilbert have done. As an alternative, physicists can try to collaborate closely with biologists. In his reflections on the contributions of the late Irwin C. “Gunny” Gunsalus, who was a professor of biochemistry at the University of Illinois at Urbana-Champaign, Frauenfelder noted that “after a short time it was obvious that we physicists did not know the biochemistry and the biochemists did not really understand the physics…. Gunny taught us to treat the bio-chemical side of the experiment with the same care we used [on] our own, the physics side.” However, such cooperation is fraught with difficulties, because the key ideas have to come from the biologists who, consequently, take on the leadership role in the collaboration and who see physicists as merely providing a service.
In Biological Physics , Nelson takes the point of view that one can use examples coming from biology to illustrate important physics principles. Thus his book is more an introductory physics text with emphasis on topics that come up in soft condensed matter physics rather than a text that focuses on the physical details of biological systems. Although the book contains a lot of descriptive content on biological systems, including a fairly quantitative discussion of the Hodgkin–Huxley equations, the meat of Nelson’s work is in introducing the principles of statistical physics to the study of, for example, diffusion, chemical equilibrium, and properties of polymers. Specific molecules involved in biological function are described qualitatively in the book, but one finds relatively little emphasis on what many biophysicists regard as the key para-digm of biophysics: structure—function relationships for biomolecules.
One of the problems of this approach is that it covers a lot of the same ground as the traditional physics and chemistry classes for undergraduates do, which leaves less space for biological detail. So, although it does provide an introduction to biological examples for conventional physics (and to some extent chemistry), Nelson’s book gives limited guidance on understanding the elucidation of the function of biomolecules. Such guidance is found, for example, in more specialized texts like Jonathan Howard’s book on molecular motors, Mechanics of Motor Proteins and the Cytoskeleton (Sinauer Associates, 2001), or Bertil Hille’s book, Ion Channels of Excitable Membranes (Sinauer Associates, 2001).
What is the answer for physics departments that want to provide material seen by their physics students as relevant to biology? As the interface between biology and physics evolves, physics departments may also evolve to include biology as a formal part of the curriculum. Physics departments may create a division in biophysics, or split off a separate department, as has been the case in the formation of astronomy and geophysics departments. For now, some kind of compromise must remain in which physicists who have retrained themselves as biologists can still teach in physics departments or be appointed jointly in physics and biology departments. Such decisions, when made, will probably be reflected in the way the interface between biology and physics is taught.
In the meantime, Nelson’s Biological Physics is a useful teaching tool for faculty who are more on the physics end of the interface, while other books—such as those following in the tradition of Charles Cantor and Paul Schimmel’s Biophysical Chemistry (W. H. Freeman, 1980), now sadly out of date—will provide teaching material for faculty coming from the more biologically motivated side.
