Carlos F. Lopez, a Post-doc in the Department of Chemistry and Biochemistry at the University of Texas, Austin, presents On The Hydrophilic Role of Hydrophobic Groups and Their Contributions to Cold Protein Denaturation as part of ChBE's spring seminar series.

* Refreshments will be served at 3:30 PM in the Lower Level 1 Gossage Atrium
* Lecture commences at 4:00 PM in L1255 in the Ford ES&T Building

Seminar Abstract
Proteins undergo structural transitions to denatured states when thermodynamic or chemical
perturbations are introduced to their native environment. Cold denaturation is an interesting
solvent-driven phenomenon whereby proteins lose their hydrophobic associations leading to a
denatured state. The currently accepted explanation for cold denaturation is tightly linked to a
favourable change in the water to non-polar group interaction at cold temperatures which is
thought to eventually disrupt the protein tertiary structure. In this work we show how this
environmental perturbation leads to kinetic changes in the protein core due to a shift in the water
to non-polar atom interactions in apomyoglobin (apoMB). Analysis of our results shows that the
isothermal compressibility of the protein increases with decreasing temperature thus suggesting
an increase in the protein interstitial space. An increase in the number of solvent contacts around
the protein, and in particular, around non-polar atoms suggests that the compressibility increase
is an indirect result of increased interfacial surface contacts. Atoms with increased
compressibility and larger-than-expected fluctuations are localized within the protein core
regions. These results can be used to motivate an atomic level cold denaturation mechanism that
explains and predicts protein structural changes under cold conditions. These results provide a
basic biophysical explanation of the mechanism of denaturation away from ambient conditions
and how such conditions affect protein stability. As such, our results provide novel plausible
pathways for the loss of protein structure, which could be important in fundamental biochemical
and biophysical processes, as well as subjects of medical nature such as diseases linked to
protein structural transitions.