Philip Nelson

I'm currently studying the physics of artificial biomembranes, biopolymers such as DNA, and other "soft" condensed matter systems.

There is a great cultural gap between physics, which seeks to understand extremely simple systems, and biology, which is obliged to study the overall behavior of extremely complex systems. I think that one area where simplicity and life intersect is the study of biomembranes and biopolymers, both in isolation and as active elements of cells. Membranes and polymers display the sort of universal behavior amenable to the powerful tools of statistical physics, thus making these systems are a bit more inevitable, less accidental, than more complex architectural elements of life. Nature has made extensive use of these generic properties in constructing useful materials and molecular machines; moreover, artificial analogs of biomaterials are subjects of intense investigation for a wide variety of bioengineering applications.

Of course, physicists have been studying membranes and polymers for much of this century. Much physical research on these systems has concerned bulk systems, in thermal equilibrium. But the activities of many molecular actors are obscured when we look at them in bulk; new, single-molecule techniques reveal much that was previously hidden. Also, life processes take place far from equilibrium. So we have been studying mainly experiments involving the manipulation of single molecules of DNA, and dynamical phenomena involving membranes.

I have some interest as well in general nonlinear dynamics (including pattern formation), self-assembly, electrostatics at the colloidal level, and the general area of geometrical methods in physics.

• Fellow of the American Physical Society, "For contributions to the understanding of soft biomaterials, quantum fields, and superstrings, using geometrical and topological methods" (2003)
• Ira Abrams Memorial Award for excellence in undergraduate teaching (2001)
• National Science Foundation Presidential Young Investigator Award (1988)
• Alfred P. Sloan Foundation Fellow (1988)
• Department of Energy Outstanding Junior Investigator Award (1988)
• Junior Fellow, Harvard University Society of Fellows (1984-87)

• Professor, University of Pennsylvania (1998-)
• Member, Institute for Medicine and Engineering, University of Pennslyvania (1998-)
• Associate Professor, University of Pennsylvania (1992-1998)
• Assistant Professor, University of Pennsylvania (1988-1992)
• Assistant Professor, Boston University (1987-88)

• My book: Biological Physics: Energy, Information, Life (Updated edition; W.H. Freeman and Co.,  2008). Now translated into Spanish, Portuguese, and Chinese.
• The Role of Microtubule Movement in Bidirectional Organelle Transport, PNAS, in press (2008) (with I. Kulic, A.E.X. Brown, H. Kim, C. Kural, B. Blehm, P. Selvin, and V. Gelfand).
• DNA looping kinetics analyzed using diffusive hidden Markov model. With J. Beausang, C. Zurla, C. Manzo, D. Dunlap, and L. Finzi. Biophys. J. 92, L64 (2007).
• High flexibility of DNA on short length scales probed by atomic force microscopy, Nature Nanotechnology, 1 137-141 (2006) (with P. A. Wiggins, T. van der Heijden, F. Moreno--Herrero, A. Spakowitz, R. Phillips, J. Widom, and C. Dekker).
• Electrostatic Repulsion of Positively Charged Vesicles and Negatively Charged Objects, Science 285 394--397 (1999) (with H. Aranda-Espinosa, Y. Chen, N. Dan, T. C. Lubensky, L. Ramos, and D. A. Weitz).
• Transport of Torsional Stress in DNA. Proc. Natl. Acad. Sci. USA 96 14342 (1999).
• Torsional Directed Walks, Entropic Elasticity, and DNA Twist Stiffness, Proc. Natl. Acad. Sci. USA 94 14418 (1997) (with J. D. Moroz).
• Spontaneous Expulsion of Giant Lipid Vesicles Induced by Laser Tweezers, Phys. Rev. Lett. 78 386 (1997) (with J. D. Moroz, R. Bar-Ziv, and E. Moses).
• Lectures on Strings and Moduli Space, Phys. Reports 149 337 (1987).
• Global Color is not Always Defined, Phys. Rev. Lett. 50, 943 (1983) (with A. Manohar).