Dynamics of myoglobin in confinement: An elastic and quasi-elastic neutron scattering study

In order to clarify the role of hard confinement on protein dynamics, elastic and quasi-elastic neutron scattering experiments have been performed on ferric horse myoglobin in two different systems: the protein embedded in a porous silica matrix, and the corresponding hydrated protein powder. Elastic data have been analysed using two different models (dynamical heterogeneity and anharmonic double-well potential) that take into account deviations of elastic intensity from Gaussian behaviour. The profile of quasi-elastic spectra has been approximated by a combination of Lorentzian and Gaussian components. Comparison between the data relative to the two different samples indicates that geometrical confinement within the matrix plays a crucial role in protein dynamics and conformational stability, the effect of sol-gel encapsulation being essentially a reduction of large scale protein motions (alpha-relaxation) likely related to the slowing down of solvent confined diffusion. (C) 2007 Elsevier B.V. All rights reserved.