Structure of the Plasma Membrane and Other Surfaces

Danielli (15) shows that the permeation of molecules through a lipide layer requires a minimum kinetic energy for passage past energy barriers, of which those for transition between water and oil phases are prominent. 

This idea is adaptable to any type of membrane, regardless of the supposed unavoidable passage through oils. 

Proteins obviously retain molecules by various tyiies of force at different positions, and in general it must be recognized that this idea is valid. Danielli suggests a modification of his formula which must be used if the plasma membrane is not a homogeneous lipide layer, but obviously the modification is not usable because of lack of data. However, even if this membrane is of Danielli s tjrpe, he concludes that the passage of a solute obeys the rule  

Therefore there is no reason, in any of the cases cited, for attributing any properties to the plasma membrane which invalidates the use of the diffusion laws developed above. 

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