Molecular Sieve Studies of Interacting Protein Systems

The transport of self-associating macromolecules on molecular sieve columns has been investigated by computer simulation. The chromatographic behavior of monomer-trimer, monomer-tetramer, and monomer-octamer systems has been simulated in order to study the effects of several important variables on reaction boundary shape. These variables include flow rate, gel porosity, gel particle diameter, development time, and equilibrium constant. A given self-associating solute can be expected to yield appreciably different boundary profiles on gels of different porosities and bead sizes or on the same column at different flow rates. Results of the simulations indicate that axial dispersion contributes substantially to the shape of solute profiles. The effect of axial dispersion on boundary shapes was evaluated by comparing the simulated profiles with quantitative predictions of the corresponding asymptotic equations in which axial dispersion is assumed to be absent. Substantial differences were found between equilibrium constants and centroid parameters predicted from the asymptotic equations and those of the simulated profiles. The role of axial dispersion was investigated further by simulations in which all nondispersive transport was assumed to be absent. It was found that bimodal derivative patterns can arise from simultaneous dispersive transport and chemical reaction in the absence of the translational components. Results of the simulated chromatographic cases were compared with simulations of velocity sedimentation of the same solute systems in order to evaluate similarities and differences between the two types of transport behavior.