DESCRIPTION: The proposed study will apply theoretical methods to investigate the interactions of G-actin and F-actin with fructose 1,6-bisphosphate aldolase. Brownian dynamics (BD) will simulate the protein-protein associations in aqueous media as influenced by the electrostatics of the proteins; particular attention will be paid to the solvent and electrolyte effects that mediate macromolecular interaction in physiological aqueous solutions. The BD simulations will allow for the study of a large number of BD-docked complexes rather than a single complex, and they will allow for the computation of the mean force versus the docking coordinate so that a free energy curve for the protein docking can be created. The BD method allows for an automated force-guide exhaustive search of docked conformations which would avoid trapping in local energy minima. BD will be able to predict the various kinds of complexes which these proteins can form and their relative stability. The importance of the proposed study relates to the hypothesis that F-actin creates structure in the cell cytoplasm upon which glycolytic enzymes can associate and dissociate dynamically. These dynamic associations may be important to organizing the reactions in the glycolytic pathway. The outcome of this research would be an improved understanding of protein association with actin in solution. It will provide an initial theoretical test for F-actin, thus giving a framework for glycolytic enzymes to function in cells. It will be a first step in understanding the theory behind assembly of structures in the cytoplasmic matrix. Thus, the outcome of this research should have far-reaching implications for cytoplasmic structure and for metabolic regulation.