Effect of the environment on the protein dynamical transition: a neutron scattering study.
We performed an elastic neutron scattering investigation of the molecular dynamics of lysozyme solvated in glycerol, at different water contents h (grams of water/grams of lysozyme). The marked non-Gaussian behavior of the elastic intensity was studied in a wide experimental momentum transfer range, as a function of the temperature. The internal dynamics is well described in terms of the double-well jump model. At low temperature, the protein total mean square displacements exhibit an almost linear harmonic trend irrespective of the hydration level, whereas at the temperature T(d) a clear changeover toward an anharmonic regime marks a protein dynamical transition. The decrease of T(d) from approximately 238 K to approximately 195 K as a function of h is reminiscent of that found in the glass transition temperature of aqueous solutions of glycerol, thus suggesting that the protein internal dynamics as a whole is slave to the environment properties. Both T(d) and the total mean square displacements indicate that the protein flexibility strongly rises between 0.1 and 0.2h. This hydration-dependent dynamical activation, which is similar to that of hydrated lysozyme powders, is related to the specific interplay of the protein with the surrounding water and glycerol molecules.
Paciaroni
Alessandro
A
Istituto Nazionale per la Fisica della Materia, Dipartimento di Fisica dell'Università di Perugia, Perugia 06121, Italy. alessandro.paciaroni@fisica.unipg.it
Cinelli
Stefania
S
Onori
Giuseppe
G
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002645:Chickens; D005990:Glycerol / Q000737:chemistry; D009113:Muramidase / Q000737:chemistry; D009502:Neutrons; D011506:Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D013696:Temperature; D014867:Water / Q000737:chemistry
D011506:Proteins; D014867:Water; D009113:Muramidase; D005990:Glycerol