Glass Transition proteins

Temperature-dependent pure dephasing rates of MbCO in three solvents show identical power law behavior at low temperatures. At intermediate temperatures there is a break in the power law arising from the solvent-influenced protein glass transition. Above this point the data in glassy trehalose are exponentially activated. The other solvents, which at elevated temperatures are liquids, have additional solvent viscosity-dependent contributions to the pure dephasing rate. 

Vitkup, D., Ringe, D., Petsko, G.A. and Karplus, M. (2000) Solvent mobility and the protein glass transition,... 

The effect of ions on denaturation temperatures is well-studied for dilute solutions. Effects related to the Hoffineister series are apparent. Unfortunately, no systematic studies of ions on protein glass transitions are available, and it cannot be assumed that these will have a neghgible effect on the materials properties during extrusion. 

In Figure 2.8(a) we have plotted the MSD of a water molecule (bound at time t = 0) after f = 10 ps over the whole temperature range. It shows a nonmonotonic temperature dependence. Because the protein motion is coupled to the water d)mamics it is expected that the MSD of the protein will also show similar behavior, which would lead to a protein-glass transition and eventually to the loss of protein functionality. 

Toumier, A.L., Xu, J., and Smith, J.C. Translational hydration water dynamics drives the protein glass transition, Biophys.., 85,1871, 2003. 

Vitkup D, Ringe D, Petsko GA, Karpins M Solvent mobility and the protein glass transition. Nat. Struct. Biol. 2000, 7 34—38. 

Protein-glass transition and hydration-layer dynamics... 

Biological activity is found to be restored after the protein-glass transition [8]. The protein-glass transition appears to be a general phenomenon at low temperature in hydrated proteins. 

Protein-glass transition at 200 K role of water dynamics... 

The proximity of this liquid-liquid transition to the protein-glass transition temperature is suggestive. Clearly, at temperatures below 220 K or so, the dynamics of water and protein are highly coupled. A recent computer simulation study has shown that the stmctural relaxation of protein requires relaxation of the water HB network and translational displacement of interfacial water molecules. It is, therefore, clear that the dynamics of water at the interface can play an important role. This is an interesting problem that deserves further investigation. 

III. THE PROTEIN GLASS TRANSITION CROSSOVER A. Neutron Results... 

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