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           COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
                              College of Science
                       (CDS Department CSI 898-Sec 001)
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Designing Artificial Cells for Biological Energy Conversion

                      David A. LaVan

          Materials Science and Engineering Laboratory
National Institute of Standards and Technology, Gaithersburg, MD

I will discuss work performed in collaboration with the National Center 
for Design of Biomimetic Nanoconductors (NCDBN), an NIH Nanomedicine 
Roadmap center, to study the interaction of transmembrane proteins with 
cell membranes and create synthetic protocells that leverage our 
understanding of membrane and cell function and allow us to validate 
the computational work.  Cell membranes contain numerous ion channels 
and ion pumps that work together to form ion concentration gradients 
across the membrane, which can be triggered to release electricity in 
the form of an action potential. These cells convert chemical energy 
stored in the concentration gradient into electricity.  We have modeled 
the formation of action potentials in polarized cells by incorporating 
relationships for a number of nanoconductors as well as the cell membranes. 
Using parameters extracted from initial models of an electrocyte, we 
then designed an artificial cell to maximize power output density and 
energy conversion efficiency.  The simplest configuration that could 
produce an action potential was also examined, but it is far less 
efficient than the natural electrocyte or the artificial cell.

A much simpler system is based on the formation of a DC potential 
using biological ion concentration gradients.  These devices are 
based on the formation of a lipid bilayer at the interface of two 
droplets.  The bilayer would have engineered alpha-Hemolysin as 
artificial ion channels.  A model of this system was created by 
coupling electrode, transport protein and membrane behavior; the 
device output was significantly improved.

                        Monday, November 3, 2008
                                  4:30 pm
                     Room 301, Research I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at www.cmasc.gmu.edu/seminar/schedule.html
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