Haig P. Papazian Distinguished Service Professor
OFFICE: 5735 S. Ellis Ave., SCL 231, Chicago, IL 60637
PHONE: (773) 702-9092
FAX: (773) 795-9106
The research in the Voth group involves theoretical and computer simulation studies of biomolecular and liquid state phenomena, as well as of novel materials. A primary goal of this effort is the development and application of new computational methodologies to explain and predict the behavior of complex systems. Such methods are developed, for example, to probe phenomena such as protein-protein self-assembly, membrane-protein interactions, biomolecular and liquid state charge transport, complex fluids and nanoparticle self-assembly. Specific examples of research projects include:
Multiscale Theory and Simulation: The Voth group has a key focus on the development of powerful multiscale theory and computational methods for complex biomolecular systems. These multiscale methods include systematic coarse-graining approaches, mesoscopic modeling, and multiscale bridging between all of the relevant scales. Our multiscale methods are being applied to filaments (such as actin, shown in Fig. 1), microtubules, biological membranes and membrane proteins, nucleic acids, peptide aggregation and self-assembly, carbohydrates, and viral capsids.
Membranes and Membrane Proteins: One of the most important problems in all of biophysics is the complex interplay between the "fluid mosaic" of the biological membrane, membranes domains (aka "rafts") that are rich in several membrane components, and membrane proteins (e.g., ion channels or receptors). Membranes bind with proteins that have a specific purpose, such as for membrane remodeling (e.g., to assist the budding of vesicles). As one example, the Voth group has developed and applied a comprehensive multiscale approach to describe the complex and interesting process of membrane remodeling that involves proteins having N-BAR domains, as illustrated in Fig. 2
Charge Transport: The transport of charge (protons and electrons) in aqueous and biomolecular systems is another important multiscale phenomenon. Here, the smallest scale is at the scale of the electrons because such processes involve either the electrons directly or indirectly, often in the form of proton transport (via, for example, the Grotthuss hopping mechanism in which chemical bonds and hydrogen bonds are rearranged to translocate the excess protonic charge along the water chain). Proton transport is also dependent on the conformation, dynamics, and assembly of the medium in which it occurs. Our group has worked for nearly twenty years to develop a multiscale theoretical and computational methodology to describe proton transport phenomena in biology and in a host of other systems. Schematically depicted in Fig. 3 below is the range of the systems we have studied, in this case relevant to biological proton solvation and transport processes occurring in the cell. This includes excess protons in bulk water and related systems (panel A), at phospholipid membrane interfaces (panel B), in proton pumps such as cytochrome c oxidase (panel C), through proteins such as the M2 proton channel of the influenza A virus (panel D), in other channels such as mutated aquaporins (panel E), in Na+/H+ and Cl-/H+ antiporters, and in the enzyme human carbonic anhydrase and its mutants (panel F). In the future, proton and electron transport in a number of other important biomolecular systems will also be studied, and this description of fundamental charge transport phenomena will be incorporated into our overall multiscale computer simulations in order to reach very large length and time scales, and enzymes such as carbonic anhydrase. A critical aspect of the computational approach of these problems is the ability to include the explicit process of proton shuttling through chains of water molecules and protein amino acids.
Complex Materials Relevant to Renewable Energy Technology: This work in the Voth group includes theoretical and computational studies of solvation phenomena and complex dynamics in novel room temperature ionic liquids and ion exchange membranes, such as proton exchange membranes (PEMs) for fuel cell applications (see Fig. 4 below).