The biophysics group is comprised of four faculty members interested in a wide array of topics ranging from structure and dynamics of biological macromolecules to collective behavior of macromolecular and cellular systems. The faculty members are joined in their endeavors by several postdoctoral research associates, and graduate and undergraduate students. More details can be obtained from web pages of individual groups or faculty members and from other areas of the Physics Department website.
Faculty: A. Ourmazd, V. Raicu, D.K. Saldin and M. Schmidt.
Abbas Ourmazd's research is aimed at developing innovative approaches for determining the structure and conformations of biological systems ranging from single molecules to whole cells at high resolution. The central hypothesis rests on new evidence that advanced algorithms stemming from Riemannian geometry, graph theory, and machine learning can be combined to forge a powerful new approach to biological structure determination in a way which circumvents the limits set by noise and radiation damage. These algorithms can be used with existing techniques, such as cryo-electron microscopy (cryo-EM), and emerging approaches exploiting the extreme brightness of X-ray Free Electron Lasers (XFELs). More generally, our work has important implications for tomography of faintly scattering, non-stationary objects at any length scale.
For more information: Ourmazd's research website
Valerică Raicu is interested in experimental and theoretical aspects of the structure and dynamics of macromolecular and cellular systems in vivo. One of the main research themes in his lab is imaging of protein activity and interactions in living cells. This study involves novel approaches to laser-scanning fluorescence microscopy with spectral and temporal resolution, which is used in conjunction with a process of non-radiative energy transfer between fluorescent molecules, called Förster (or fluorescence) resonance energy transfer (FRET). The second major research theme in Prof. Raicu's lab is the use of dielectric (or impedance) spectroscopy to probe the response to radiofrequency electrical fields of a material's electrical polarization in order to determine its physical and structural characteristics at the microscopic level. This method is particularly suitable for characterization of biological cells individually dispersed in suspension or as part of supracellular associations, such as tissues and organs.
For more information: Raicu's research website
Dilano Saldin's biophysics research is aimed developing methods for determining the structures of biological molecules from ensembles close to their natural environments, thus obviating the sometimes problematic need for crystallization. Examples are molecules in liquid solution, or proteins embedded in membranes. In the former case the molecules may be assumed to be oriented completely randomly, while in the latter, they are assumed to be randomly oriented about an axis normal to the membrane. Another configuration of partial orientational ordering from which we are extracting structural information is that of single molecules aligned by a laser, as well as molecules with completely arbitrary orientation, as in proposed experiments at a future x-ray free electron laser (XFEL). The theoretical approaches focus on analyzing angular correlations amongst scattered intensities in a spherical or circular harmonic basis, and generalization of fiber diffraction theory (which led to the elucidation of the DNA structure) most appropriately analyzed in a cylindrical harmonic basis.
For more information: Saldin's research website
Marius Schmidt’s research focuses on a unique method that unifies atomic structure with chemical kinetics: ultra-rapid, time-resolved X-ray structure analysis of proteins. This technique requires the brightest X-ray sources of the world, one of which is the close-by Advanced Photon Source at Argonne National Lab near Chicago. X-ray data collected there are four dimensional, with space and time as variables. With these data, chemical reactions can be observed directly in the protein crystals with a time-resolution of 100 pico-seconds and on the atomic length scale. The aim is to completely understand the catalyzed reaction including the atomic structures of the reaction intermediates and the corresponding kinetic mechanism. To analyze the large body of time-resolved X-ray data sophisticated and user-friendly software is required that is also developed by Prof. Schmidt’s research group. In addition, proteins are produced, purified and crystallized for “de-novo” X-ray structure analyses.
For more information: Schmidt's research website