Protonic Conductivity in Biomaterials in the Frame of Percolation Model
In the last few years we have studied the dielectric properties of nearly dry biological materials as a function of their water content. Details of the experimental apparatus have been given1. Let us only mention here that our technique combines a digital balance to monitor sample’s weight with an a. c. bridge to record radiofrequency dielectric properties of a composite capacitor, designed to avoid metal contacts and to ensure uniform evaporation from the sample. The investigation of lysozyme powders was quite fruitful because we were able to assess the onset of a protonic percolative conductivity at a critical hydration threshold. This threshold was found to be coincident with the critical hydration for the onset of enzymatic activity3–7. This study was extended to other more complex biomaterials, of different origin: purple membrane8, artemia cysts9, and maize-seed components10. In all these cases a critical hydration for the onset of a biological function was already known, and our data showed the percolative threshold for proton motion to be correlated with the emergence of biological function11.
KeywordsCritical Exponent Percolation Threshold Protonic Conductivity Percolation Theory Percolation Model
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