We are theoretical and experimental physicists committed to developing a deeper understanding of life. Why do we do it? What can our discipline contribute to this undertaking? In our view the answers are multifaceted and speak directly to who we are as scientists, how we see one part of the future of physics, and where we hope to contribute to our university’s role as an intellectual leader in the twenty-first century.
We are privileged to live in an age where fundamental workings of life are first being understood in a quantitative manner. New insights into the complexity of living systems are coming fast, one upon the next, from our colleagues in chemistry, biology, and a wide variety of related fields. Current introductory biology textbooks that intend to survey the state of the field have to be regularly updated. A biologist of the nineteenth century would be bewildered by a current elementary biology textbook; one from the mid twentieth century would recognize, say, Crick’s central dogma underlying information flow in molecular biology, but, I suspect, be astounded by the extension of these ideas into e.g., epigenetics.
Dr. Craig Venter, who made key contributions to sequencing the human genome and who created the first cells with a synthetic genome, suggested that we indeed live in the age of biology: "If the 20th century was the century of physics, the 21st will be the century of biology" (New Perspectives Quarterly 21 (4), 73—77 (2004).
We disagree. Precisely because of the remarkable flood of new information coming from the mapping of genomes, a better understanding of the biochemical inventory of living cells, and new quantitative techniques allowing us to probe, for the first time, single molecules, there is a need for a new role of physics, functioning productively at the boundaries of the traditional disciplines.
Biological phenomena are constrained by fundamental physics. This fact was already well understood and exploited by physicists like Galileo Galilei, who formulated simple organizing principles that continue to help us make sense of the wide variety of body plans found in the living world.
More recently, Charles Young and Hermann Helmholtz made significant contributions to the biomechanics of the skeleton and to elucidating fundamental laws of human perception such as hearing and vision.
We see ourselves as physicists who continue that tradition, but now at the level of individual molecules and cells. Today, physicists have an exciting project and opportunity: developing a profound understanding of how the interactions of complex molecular systems lead to the collective organization and dynamics that we see as life. Exquisite new experimental tools, such as the ability to manipulate individual macromolecules, have become available to help us in that quest.
For example, we are learning that the cytoskeleton, a complex chemically heterogeneous network of filaments that controls the mechanics of cells, is driven out of equilibrium by endogenous molecular motors. Now, here is an interesting problem for physics! What are the collective elastic properties of such a complex and active (i.e., nonequilibrium) material? We already have learned that established and fundamental principle of equilibrium statistical mechanics like linear-response theory and the fluctuation-dissipation “theorem” fail to apply to this system. Can we formulate new physical descriptions that can describe the cytoskeleton quantitatively and help us to better understand how cells adopt so many different morphologies?
Of course, the details of how that nonequilibrium steady state is tuned by the cell are, at the time of my writing, still murky. We know, for instance, that calcium ion concentrations can control the activity of the myosin molecular motors, but these same motors also appear to be affected by an entirely independent signaling (“Rho-associated kinases” or ROCK) pathway. Nevertheless, the basic point remains: biology pushes us to consider the collective properties of complex condensed matter systems in specific nonequilibrium states.
Our colleagues in biology and chemistry may be rather nonplussed at this approach, whose scientific outlook is based more on insights provided by molecular biochemistry and evolutionary descriptions, such as bioinformatics. This problem is, in my view, endemic in interdisciplinary science. The distinguished physicist Professor Michael Fisher (Maryland) said, “There is no interdisciplinary science without the disciplines.”
I take this to mean that the key to biological physics is to approach questions regarding living systems in a new light based on the study of physics. We do not necessarily intend to answer questions posed by our colleagues in the life sciences differently, but rather to ask different questions. We founded this center for biological physics to foster an environment where those new questions may be framed.