"Fundamental Molecular Studies of Complex Fluids for Preservation of Biological Systems"
Labile biological systems such as proteins, cells, or tissue must often be stored for prolonged periods of time. This is generally achieved by freezing the system of interest in an aqueous solution containing various additives, whose purpose is to minimize the damage that arises from the formation of ice crystals. In some cases, it is also possible to freeze-dry the resulting formulation, thereby resulting in a product that can be stored without a need for refrigeration. In most cases, a large fraction of the biomolecules or cells do not survive the freeze-thawing or freeze-drying processes; the rates of recovery are low and contribute significantly to the cost and availability of the resulting product.
Some examples of these additives, or "protectants ", are provided by dimethylsulfoxide (DMSO) and ethylene glycol, both of which have undesirable side effects. In practice, protectant formulations are generally conceived through a costly trial-and-error process. And, while some general ideas have emerged regarding their function, the precise mechanisms by which protectant molecules act to preserve viability during freezing and drying are not well understood.
In this work the PI proposes to conduct a systematic and comprehensive study of the role of various protectant molecules on the stability of proteins in solution and in anhydrous, protectant matrices. The work is largely focused on the study of the disaccharides, which in recent years have shown promise for effective preservation of biological systems. The PI also examines how the same protectants act to stabilize lipid bilayer membranes in solution and in dry matrices.
The project includes both modeling and experimental components. Computational aspects will take priority over experimental (X-ray structure analysis, NMR and calorimetry work will not be performed). At the modeling level, the PI uses molecular simulations to elucidate the mechanisms by which protectants work, and to identify the main structural attributes that render some protectant molecules more effective than others. This will require that new simulation methods be develop to facilitate the study of large ensembles of complex molecules (water, disaccharides, electrolytes and oligopeptides) both remote and near the glass transition point. At the experimental level, the PI intends to characterize the thermophysical properties of various protectant and model-protein solutions and glasses, and to relate these to preservation efficacy and to the results of our simulations. The PI may characterize the equilibrium thermodynamic properties of lipid bilayers in the presence of protectants and varying amounts of water. These data will be compared to simulation results, and will be used to rationalize his observations and those of others regarding the preservation of cells.
The broader impact of the research is that it will lead to a deeper understanding of protein and cell stability in solution and in the presence of protectant solutes. It will also generate predictive models and experimental thermodynamic-property and transport-coefficient data for rational design and optimization of preservation processes. More importantly, it has the potential to result in improved protectant molecules and formulations that will permit long-term storage of food, pharmaceutical, and biomedical products. The potential educational impact of the research is considered high since the PI has a record of involving students, including underrepresented groups, in his research.
