Analysis of protein-protein interaction by simulation of small-zone size exclusion chromatography. Stochastic formulation of kinetic rate contributions to observed high-performance liquid chromatography elution characteristics

Abstract

High-performance liquid chromatography (HPLC) procedures provide size-exclusion chromatography with sufficient speed that the elution characteristics of mixtures of interacting macromolecules are potentially determined by the kinetics of association and dissociation. However, few studies have yet addressed the consequences of interaction kinetics on HPLC analyses or evaluated the potential application of HPLC methods for the qualitative and quantitative interpretation of macromolecular interaction kinetics. An earlier simulation of small-zone chromatography of interacting molecules (Stevens, F. J. 1986. Biochemistry. 25:981-993) has been modified to incorporate the effects of association/dissociation kinetics on elution behavior. The previous assumption of instantaneous equilibration has been replaced by explicit calculation of partial relaxation of complexed and free constituent mixtures during each iteration of the simulation. In addition, a stochastically based formulation has been introduced to determine a velocity probability distribution that emulates the partial intermixing of free and complexed pools during the iteration cycle. The simulation generates bimodal elution profiles representing stable complexed and free components of mixtures for which interaction is characterized by slow kinetics relative to chromatography run times. For mixtures with rapid kinetics, a single-asymmetric peak results. When tested with a large-zone sample such that a plateau of stable concentration is generated, the simulation reproduces previous characterizations based on evaluations of solute continuity equations. Therefore, HPLC may, in many cases be an appropriate basis for techniques by which to evaluate kinetic and affinity characteristics of interacting biomolecules.