Microscopic model of protein crystal growth

A microscopic, reversible model to study protein crystal nucleation and gro wth is presented. The probability of monomer attachment to the growing crys tal was assumed to be proportional to the protein volume fraction and the o rientational factor representing the anisotropy of protein molecules. The r ate of detachment depended on the free energy of association of the given m onomer in the lattice, as calculated from the buried surface area. The prop osed algorithm allowed the simulation of the process of crystal growth from free monomers to complexes having 10(5) molecules, i.e. microcrystals with already formed faces. These simulations correctly reproduced the crystal m orphology of the chosen model system - the tetragonal lysozyme crystal. We predicted the critical size, after which the growth rate rapidly increased to approximately 50 protein monomers. The major factors determining the pro tein crystallisation kinetics were the geometry of the protein molecules an d the resulting number of kinetics traps on the growth pathway. (C) 2000 El sevier Science B.V. All rights reserved.