Biological Physics Research Areas

Our faculty members are conducting research in the following Biological Physics areas: 

Leon Cooper conducts research in brain function and neural systems that draws on biology, psychology, mathematics, engineering, physics, linguistics, and computer science within the Institute for Brain and Neural Systems. The overall goal is a deeper understanding of the basic processes by which the central nervous system learns and organizes itself and acquires the capacity for mental acts. The Institute is especially interested in the interaction between theoretical ideas and experimental results. Current areas of research include theories of cortical plasticity, cellular and molecular mechanisms underlying learning and memory storage, the analysis and application of artificial neural networks and signal processing.

Sean Ling and Derek Stein lead two experimental groups working in the field of nanobiophysics. Ling's group applies the latest nanopore and nanochannel technologies to the study of biologically relevant questions such as rapid DNA sequencing. His group is combining micromanipulation techniques such as magnetic and optical tweezers with solid-state nanopores/nanochannels and fluorescence imaging, to study the dynamics of biomolecules. He is also exploring the possibility of using these nanotechnology tools for studying gene regulation.

Derek Stein’s group focuses on studying the molecular building blocks of life at their natural length scales using nanofabricated tools such as solid-state nanopores and nanofluidic devices. Because of their extremely small size, the measured ionic current through a nanometer-scale pore is sensitive to the insertion of a single molecule. Based on this principle, the electrophoresis of individual DNA molecules through a nanopore provides information on both molecular size and folding conformation at remarkably high speeds. It should also provide a powerful new way to study the action of important proteins on DNA. Since bases are forced through the pore single-file, it may even offer a way to directly read the sequence off a single molecule. Nanofluidic devices confine fluids and biomolecules to ultra-small volumes whose geometries can be arbitrarily defined by lithography. New behavior tends to emerge as channel dimensions become comparable to molecular length scales. The confinement of DNA to channels smaller than the molecular radius of gyration, for example, leads to entropy-dominated dynamics that can be used to measure molecular length. We anticipate new behavior and technological opportunities to emerge as the size of nanofluidic systems approaches other fundamental length scales, such as the molecular persistence length and the electrostatic (Debye) screening length. 

Jay Tang's biophysics laboratory seeks to bridge the gap between the traditionally separate physics and biology fields by taking physicists' approach towards biological problems and systems. Their expertise is in assembly and dynamics of cytoskeletal protein filaments F-actin and microtubules. The recent research of the group has focused on the phase transition and diffusion of actin filaments and the pattern formation of microtubules. The pertinent biological questions addressed include morphology, pattern formation, force generation and motility of cells. The ongoing research on cell motility, in particular, covers experiments on adhesion, spreading and migration of human white blood cells, on reconstituting actin based propulsion using enzyme coated beads in cellular extracts, and on bacterial swimming, accumulation and adhesion. The Tang group also performs computer simulations in close comparison with experimental findings, with the goal of quantitatively account for biological phenomena based on known physical principles. For more details, visit 

Jim Valles' group investigates how strong static magnetic fields interact with biological systems and materials. These interactions have the potential to be exploited as new tools for dissecting biological processes such as cell division, pattern formation by biopolymers, and gravity sensing by micro-organisms. Their most recent investigations focus on the source of the exquisitely sensitive gravity force transduction mechanism of paramecia. They are combining microscopy, variable magnetic forces and particle tracking techniques to probe it. 

See-Chen Ying’s theoretical research in biophysics concerns the study of dynamics of biopolymers such as DNA and RNA in restricted geometries including nanopore and nanochannels. The translocation of the biopolymers through nanopores is a complicated non-equilibrium process since the translocation time is typically comparable or shorter than the equilibration time of a long polymer. Initial attempts at understanding the process in terms of equilibrium concepts such as entropic barriers yield only a qualitative understanding of the process. More detailed scaling arguments and numerical simulation studies suggest complicated scaling behavior of the translocation time as a function of the length of the polymer and the driving force, depending on the nature of the driving force, length and width of the nanopore and the details of the monomer sequence.

Besides translocation, another of See-Chen Ying’s projects involves the study of unzipping of double stranded DNA via external applied force driving it through restricted geometries. Recent dynamical force spectroscopy indicates an interesting nonlinear variation of the force required to unzip the hydrogen-bonded base pairs as a function of the rate of change of the external driving force. The microscopic origin of this variation lies in the rate variation of the efficiency of the thermally activated process of unzipping the base pair. The efficiency decrease monotonically as the rate of external driving force increases. In the asymptotic limit of infinite rate of change, the base pair unzip only at a critical value of the external driving force corresponding to the point when the activation barrier vanishes. Interestingly, this problem is isomorphic to the variation of the nanofriction with the rate at which an adatom is dragged over a substrate surface.