Models for the analytical ultracentrifuge behavior of Helix pomatia alpha-hemocyanin. II. Simulations of reacting microheterogeneous hemocyanin

Simulations for the moving-boundary ultracentrifuge behavior of Helix pomatia alpha-hemocyanin have been developed, based on modification of published models. In the present treatment, it has been assumed that the protein system is extensively microheterogeneous, with respect to its whole-half molecule reactivity. It has also been assumed that all such association and dissociation reactions can proceed to equilibrium in a time appreciably shorter than that which would be required to separate nonreacting half molecules from nonreacting whole molecules. Predictions based on this model agree well with reported experimental findings of nonequilibration of fractionated material, apparent independence of whole-to-half molecule concentration ratios on total concentration in sedimentation experiments, and stopped-flow dilution reactivity over a wide range of sedimentation coefficients.