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SCIENCE AT THE EDGE SEMINAR QB/GEDD Friday, October 14 at 11:30am Room 1400 Biomedical and Physical Sciences Bldg. Refreshments at 11:15 Rob D. Coalson Department of Chemistry, University of Pittsburgh Modeling Permeation through Biological Ion Channels: A Physico-Chemical Perspective Ion channel proteins embed in the cell membrane so as to establish a membrane spanning aqueous pore. Most ion channels undergo conformational changes, induced by precise physiological stimuli, between a configuration which allows ions to flow through the aqueous pore (the “open” state) and one that prevents such flow (the “closed” state). It is challenging to compute, from basic physico-chemical principles, the current of ions that flows down the electrochemical gradient presented to them when the channel is “open”. This is a complex many-body problem in non-equilibrium statistical mechanics. In principle, the atoms in the protein channel, mobile ions, water solvent, and lipid bilayer membrane are all dynamical variables, and the time scale is long on the scale of all-atom MD simulations (many microseconds to collect full statistics of the permeation process). Fortunately, the ions tend to move slowly compared to fluctuations of the surrounding protein, water and membrane atoms, so a Langevin description of the ionic motion is often appropriate. Furthermore, prescriptions exist for computing the inputs into such a simulation, e.g., the effective potential felt by the mobile ions, ionic diffusion constants, etc. We will present calculations of this type performed on a recently crystallized bacterial pentameric ligand−gated ion channel, whose eukaryotic counterparts play an important role in neuronal function. Helen Geiger Administrative Assistant Quantitative Biology Graduate Program and Gene Expression in Development and Disease 502B Biochemistry Building Michigan State University East Lansing, MI 48824 Email: [log in to unmask] QB Website: http://www.qbi.msu.edu/ GEDD Website: http://www.gedd.msu.edu/