Relationship between Measured Diffusion Coefficients and Calculated Molecular Surface Properties

We show that the diffusion coefficients in both dry and swollen gelatin of a group of organic molecules can be expressed analytically in terms of computed molecular quantities: surface areas and measures of positive and negative electrostatic interaction tendencies, obtained by ab initio SCF calculations. The molecules' intrinsic mobilities are found to vary inversely with size and to be enhanced in these media by weakly positive and strongly negative surface electrostatic potentials.