Huang, Huey W.2009-06-042009-06-041995Cao, Hung Duc. "Protein dynamics at various hydration levels using the incoherent quasielastic neutron scattering technique." (1995) Diss., Rice University. <a href="https://hdl.handle.net/1911/16803">https://hdl.handle.net/1911/16803</a>.https://hdl.handle.net/1911/16803The incoherent quasi-elastic neutron scattering (IQNS) method is a useful technique to study biomolecular dynamics. The versatility of the method makes possible motional studies of biomolecules in different forms: powder, crystal, and solution; and at different temperatures. Thus, it allows for the investigation of biomolecular dynamics over a wide-range of physical conditions. We have used the IQNS method to study the motions of side chains in trypsin and myoglobin at various D$\sb2$O hydration levels. The scattering spectra S(Q,$\omega$) were measured in constant-Q mode. The protein in powder form exhibits vibrational high-frequency motions, while the protein in solution and in crystals are characterized by diffusive jumps, and high-frequency vibrations. At temperatures below 200K, the S(Q,$\omega$) for these proteins in solution is similar to an harmonic solid. As temperature increases, a transition is seen at 200K, above which the protein becomes more liquid-like with rapid transitions between conformational substates. The diffusion constant D for the side chains is on the order of 10$\sp{-6}$ cm$\sp2$/sec.88 p.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.BiophysicsMolecular physicsThesisTHESIS PHYS. 1995 CAO