An exactly solvable ogston model of gel electrophoresis. 7. Diffusion and mobility of hard spherical particles in three-dimensional gels

We extend our lattice model of gel electrophoresis (and diffusion) to the s tudy of the continuum limit (no lattice effect) for hard spherical particle s migrating in periodic and random three-dimensional gels. To reach the con tinuum limit, the mesh size of the system is progressively decreased until a clear extrapolation to the continuum limit (where the size of the lattice parameter is infinitely small in comparison to the size of the gel fibers) can be done. Various types of gel are studied, starting from simple period ic parallel and straight fibers to a representation of a more realistic gel formed of irregular, cross-linked fibers placed along random directions. O ur mobility data for pseudospherical particles in the continuum limit are i nterpreted in terms of the obstruction model of diffusion.