(457c) Protein Stabilization by Chemical Stabilizers: Molecular Dynamic Simulation and Experimental Validation

Protein stabilization is of fundamental importance for the processing and application of proteins as pharmaceuticals or catalysts. Polyol, carbohydrates, organic salts, polymers and weakly hydrophobic surfactant are proven to be effective to stabilize protein and peptide drugs in solution. However, little is known about the mechanisms particularly from the viewpoint of molecular interaction. In this work, we use a G¨-like off-lattice model to investigate the thermodynamics and kinetics of an all b-sheet protein in the solution in both absence and presence of small molecules, which are composed of hydrophobic and hydrophilic segment. We find that small chemical additives of an appropriate hydrophobicity assemble themselves around surface of model protein and form a confinement, which increases the conformational transition temperature and decreases the destabilization rate constant of model protein. Additives with strong hydrophobicity penetrate into the hydrophobic core of model protein, resulting in the disruption of structure. Based on above simulation results, we propose a new protein stabilization protocol, i.e. using small chemical molecules to form a confinement via self-assembly. To demonstrate above simulation, we chosen lysozyme as a model protein and determined the stabilization effect of a series of alkyl ammonium bromide (CnAB), which has both hydrophobic and hydrophilic segment. It is shown that the optimal stabilization effect is obtained by using C4AB and the order of effectiveness is as C4AB > C2AB > C1AB, C4AB > C9AB > C14AB > C16AB. The optimal concentration and temperature was also determined respectively and agreed well with experimental observations. Above simulation and experimental work are of fundamental importance for the design and selection of chemical stabilizer for protein formulation and application.