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PHYSICS AND ASTRONOMY Science at the Edge Friday, March 5, 2010 11:30a 1400 Biomedical & Physical Sciences Bldg Refreshments at 11:15a in 1400 BPS Bldg Angel Garcia Rensselaer Polytechnic Institute “Exploring the Energy Landscape of Proteins and RNA oligomers” The folded state of a protein is described as a highly packed conformation. However, upon an increase of hydrostatic pressure, proteins will unfold. This seems to contradict physical institution where a low volume state is preferred at high pressures. The solution of the clue is that the unfolded state of the protein reduces the overall volume of the protein in solution by packing water molecules in the protein interior. An analysis of the potential of mean force of small non polar molecules in water supports this idea. However, the balance between energy and volume in biomolecular systems may be more complex than for simple hydrophobic solutes in water. We will describe atomic simulations of the folding/unfolding equilibrium of a small protein (the Trp-cage miniprotein) and of an RNA tetraloop that exhibit pressure induced unfolding and cold denaturation. We will show that the structure and hydration of the unfolded state at low T and high P is different from the unfolded state at high T and low P. The equilibrium pressure-temperature free energy of folding, ∆G(P,T), is calculated from replica exchange molecular dynamics simulations. This free energy diagram has an elliptical shape, similar to what has been observed in globular proteins. We find that pressure changes the unfolded state ensemble of the protein to state that increased the solvent exposed are of the protein. This work is supported by the National Science Foundation, MCB-0543769. ****To make an appointment to meet with the speaker, please contact Prof. Lisa Lapidus ([log in to unmask])**** Kim Crosslan Undergraduate Secretary Dept. Physics & Astronomy Michigan State University 1312 Biomedical & Physical Sciences East Lansing, MI 48824 517-884-5531 <mailto:[log in to unmask]> [log in to unmask]