Phase transitions proton conductivity

The dependence of protein and solvent dynamics on hydration fits well into the above three-stage picture for some, but not all, properties. For dynamic properties that do not fit well, analysis on a case-by-case basis within the framework of the time-average picture can be informative. For example, consider protonic conduction, measured by the megahertz frequency dielectric response for partially hydrated powders of lysozyme. The capacitance grows explosively above a hydration level of 0.15 A, in a way characteristic of a phase transition (Section HI, A). The hydration dependence of thermodynamic properties shows, however. 

The rearrangement of the hydrogen-bonded network at the superionic phase transitions studied in the framework of the lattice-gas-type model, which has been described in the previous subsection, makes it possible to evaluate the main aspects of proton conductivity in the mentioned compounds. 

Spectroscopic data can also be used to study dynamical aspects, either as proton dynamics deciphered from the AH stretching band profile or as the dynamics of phase transitions. They are helpful in determining the order (first or second), the nature (displacive, order-disorder, reconstructive) and particularly the mechanism of the transformation at the molecular level. This can also shed some light on the conductivity mechanism, which can change considerably in going from one phase to the other. 

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