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Division of Science, Mathematics, and Computing presents

Quasichemical Consideration of the Effect of Osmolytes in Protein Solution Thermodynamics

Tuesday, February 5, 2013

A lecture by
Dilip Asthagiri
Johns Hopkins University
The stability of a folded protein against denaturation or aggregation is usually only a few times the typical strength of a hydrogen bond in water (about 5 kcal/mol). This modest stability results from large competing effects that arise from hydration effects and the intra-molecular interaction in the protein. Natural systems also include ions and osmolytes — small organic solutes — in the solvent matrix that can change this subtle balance of interactions stabilizing a protein. For example, in response to high concentrations of urea, a protein denaturant, cellular processes encourage accumulation of methyl amines, osmolytes that stabilize a macromolecule. Such adaptation in response to chemical, thermal, and mechanical stresses is seen in all living systems. Elucidating the physics underlying such adaptation is of fundamental interest in understanding how the solvent controls biomolecular structure, function, and organization.

Towards addressing the role of osmolytes in protein solution thermodynamics, we have developed a theoretical and computational framework that allows, for the first time, a clear examination of the excess free energy of the protein in a given solvent. We will first consider the main idea behind this framework with illustrative examples on the hydration of Ca(2+) and the protein cytochrome c. Then we will consider in detail the role of trimethylamine n-oxide (TMAO), an osmolyte, and urea in the coil to helix folding of a deca-alanine peptide.

Location: Reem-Kayden Center Laszlo Z. Bito '60 Auditorium