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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.61: Poster

Freitag, 12. März 2004, 10:30–13:00, B

Pressure-Induced Unfolding of Myoglobin: Neutron Diffraction and Dynamic Scattering Experiments — •Wolfgang Doster¹, Ronald Gebhardt¹, and Alan Soper² — ¹Technische Universität München, Physik E 13, 85748 Garching — ²ISIS, Rutherford Appleton National Laboratory, England

Pressure, as opposed to temperature, probes the role of volume fluctuations in biophysical reactions without affecting the thermal energy. This feature can provide new insight into the folding problem. Globular proteins tend to unfold in response to the application of hydrostatic pressure typically exceeding 3 kbar. Unfolding is driven by a volume decrease, which may occur either by releasing intra-molecular voids or by contraction of the solvent near the newly exposed protein surface. The latter involves changes in structure of the protein-solvent network. By dynamic neutron scattering we probe the pressure evolution of protein-solvent bonds. At the unfolding transition, we observe a reduction of the structural inter-conversion rates and of water fluctuational amplitudes, related to a compressibility change. This result suggests that stronger protein-solvent interactions in the unfolded form destabilize the native state at high pressure. Neutron diffraction experiments reveal a reorganisation in the hydration shell upon unfolding in parallel with a decrease in helix content. About 40 intact in the pressure-unfolded state indicative of a molten globular conformation.