Session A9 - Proteins.
ORAL session, Monday morning, March 22
510B, Palais des Congres
Macromolecular crowding exists in all living cells and affects protein folding, rates of diffusion, and amyloid formation. Although the biophysical theory of macromolecular crowding by thermodynamics and statistical thermodynamics approaches has been well developed, the effect of crowding on protein stability and kinetics has not received sufficient attention experimentally. We have carried out experiments to characterize the effects of macromolecular crowding on the mechanical force-induced unfolding and refolding of individual protein molecules of ubiquitin. To facilitate the mechanical unfolding experiments, polymers of ubiquitin molecules were synthesized. Using the atomic force microscope, we determined that, as the concentration of the crowding agents (dextran) increases from zero to 300 g/l, the average unfolding force of ubiquitin increase from 228 pN to 296 pN with a pulling speed of 1000 nm/s and in neutral pH. This result suggests that the unfolding rate of ubiquitin is reduced due to molecular crowding.