Contrast value, high, requirements

The high sensitivity of papain to pH changes in reactions is consistent with what is known about enzyme structure and mechanism of action. The catalytic activity of papain is based on a nucleophilic attack of the cystein residue, and the activity requires two ionizable residues Cys-25 and His-159. Only near neutral pH do these key amino acids have the appropriate ionization state that favors synthesis . At low or acidic pH values. His-159 which must be in the deprotonated state for acyl-enzyme complex formation, remains protonated leading to low enzyme activity. In contrast, at high or alkaline pH values, a proton is abstracted from Cys-25 destabilizing the intermediate transition state of the acyl-enzyme complex. 

Electrolytes for Electrochromic Devices Liquids are generally used as electrolytes in electrochemical research, but they are not well suited for practical devices (such as electrochromic displays, fuel cells, etc.) because of problems with evaporation and leakage. For this reason, solid electrolytes with single-ion conductivity are commonly used (e.g., Nafion membranes with proton conductivity. In contrast to fuel cells in electrochromic devices, current densities are much lower, so for the latter application, a high conductivity value is not a necessary requirement for the electrolyte. 

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