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