Thermodynamic potential gradients

Interfaces are necessarily narrow, their smallest width being of atomic dimension. Therefore, thermodynamic potential gradients or potential changes across interfaces are often large compared with corresponding quantities in the bulk crystal. As a consequence, the linear regime of transport rates across interfaces is readily exceeded. 

For the phosphotransferase system there is no problem in identifying the energy source for the establishment of the thermodynamic potential gradient. It is apparent that a high-energy phosphate bond in phospho-enol-pyruvate is the immediate source of the energy responsible for the vectorial translocation of the sugar molecule across the membrane (17). 

S02) easily reacts with the same membrane components, and need therefore to be removed before the separation unit. The material designer must also consider possible evaporation of membrane components. The high temperature in combination with steam can lead to increased evaporation by metal-hydroxy components. Kinetic demixing seems to be an unavoidable phenomena originating from difference in diffusivity of the metal components in thermodynamic potential gradients... 

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