Biological Physics


Biological Physics has been a significant research concentration within the Physics Department for more than 15 years. Eight faculty have active research programs in biological or on medical physics. Highlights of the program include:

Research on multiple levels from molecular (DNA, proteins) to tissue (heart muscle, brain) National and international collaborations Undergraduate Biomedical Physics program Biological physics seminar series sponsored by the Center for Interdisciplinary Research Center (CIRCS) Funding: NIH, NSF, American Heart Association, Charles H. Farnsworth Trust, Research Corporation

Single Molecule DNA-Protein Interactions
Force spectroscopy measurements in the laboratory of Professor Mark Williams use optical tweezers to manipulate single molecules and measure the forces required to stretch them. Measurements of these forces are used to determine the stability of the DNA double helix and the extent to which various DNA binding proteins alter the structure and stability of DNA. This approach provides unique insights into the function of these proteins in the cell.

Biological Metallodynamics
Nuclear resonance vibrational spectroscopy (NRVS) reveals low frequency Fe vibrations that participate in biological reactions, on the basis of synchrotron measurements near the 14.4 keV Mössbauer resonance. This work is done by the group of Professor Tim Sage in collaboration with Wolfgang Sturhahn and Ercan Alp at the Advanced Photon Source and Professor Steve Durbin at Purdue University.

Infrared Crystallography
Polarized infrared measurements in the laboratory of Professor Tim Sage yield precise molecular orientations and connect structural models derived from X-ray diffraction with conformational dynamics under physiological conditions.

Femtosecond Protein Dynamics
Femtosecond coherence spectroscopy measurements in the laboratory of Professor Paul Champion use ultrafast lasers to probe the "big bang" of biophysics, the first picosecond of diatomic ligand binding reactions in heme proteins. Direct measurements of coherent protein oscillations and vibration population decay (cooling) are performed using state-of-the-art laser technology. Longer time-scale biological processes (including a variety of novel proteins in aqueous equilibrium states or embedded in biological membranes) are probed with more conventional methodology (e.g., optical absorption and resonance Raman spectroscopy).		$Continuum laser pulses of femtosecond duration are used to probe the optical absorption of oxygenated myoglobin to measure the quantum yield of oxygen photolysis and the cooling of the unphotolyzed oxygen-bound fraction$

Theoretical Biological Physics
The interests of Professor Jorge José center on collective phenomena and self-organized ordering in condensed matter and biological systems. His current interests in biological physics include the theoretical and computational modeling of cellular division, in particular the molecular motor self-organized formation of the mitotic spindle. He also has a significant effort in trying to understand the information coding processes of physiologically relevant neuronal systems.

Medical Physics
In contrast to the molecular approach of Biophysics, Medical Physics focuses on the behavior of anatomical entities as a whole. Consequently it involves studies of healthy and diseased subjects, in both academic laboratory and hospital clinical settings. The research of Professors Aaron and Shiffman is an example, in which non-invasive electrical impedance measurements are used to assess the condition and activity of skeletal muscle. This has clear relevance to neuromuscular disease, and to general systemic disease via the mechanism of "chronic illness induced myopathy." These aspects of the program are conducted in collaboration with physicians at local hospitals, while study of the physics underlying the measurements is the primary focus at the university.

Cardiac Dynamics
The research in Professor Alain Karma's group is aimed at understanding the physiological origin and complex nonlinear dynamics of irregular heart rhythms through the development of mathematical models and computer simulations. Ongoing projects focus on modeling the bidirectional coupling of the intracellular calcium and electrical systems at the single cell level and the initiation and maintenance of the electrical turbulence underlying ventricular fibrillation at the organ level.

Theoretical / Computational Neuroscience
The primary goal of Prof. Armen Stepanyants' group is to understand the principles governing synaptic connectivity in the mammalian brain. Among several fundamental questions studied are: how do neurons find appropriate synaptic targets in the course of development, and how do neuron circuits change during learning and memory? What is the connectivity diagram in the adult cortical column? Is there an optimization principle which accounts for the design and the evolution of the cortex?

The Biological Physics faculty includes Professors Ronald Aaron (Emeritus), Paul Champion, David Garelick, Jorge José, Alain Karma, J. Timothy Sage (Associate), Carl Shiffman (Emeritus), Armen Stepanyants (Assistant), and Mark Williams (Assistant).