We present a statistical mechanical approach for quantifying thermodynamic properties of proteins in mixed solvents. This approach, based on molecular dynamics simulations which incorporate all atom models and the theory of preferential binding, allows us to compute transfer free energies with experimental accuracy and does not incorporate any adjustable parameters. Specifically, we applied our approach to the model proteins RNase A and T1, and the solvent components water, glycerol, and urea. We found that the observed differences in the binding of glycerol and urea to RNase T1 and A are predominantly a consequence of density differences in the first coordination shell of the protein with the cosolvents, but the second solvation shell also contributes to the overall binding coefficients. The success of this approach in modeling preferential binding indicates that it incorporates the important underlying physics of proteins in mixed solvent systems and that the difficulty in quantitative prediction to date can be surmounted by explicitly incorporating the complex protein-solvent and solvent-solvent interactions. / Singapore-MIT Alliance (SMA)

Molecular imprinting, a common method used in separations and chromatography to isolate specific molecules via surface binding, has been adapted for applications in biomaterials and related sciences. The objective of this study was to determine the effectiveness of different approaches to molecular imprinting by testing for preferential binding of protein on polysiloxane scaffold surfaces. To test preferential rebinding, the scaffolds were exposed to a mixture of the template protein and a competitor protein with similar size but different chemistry. Lysozyme-imprinted polymers rebound 8.13 0.99% of lysozyme without any competition and 5.1 0.3% of the protein during competition. Lysozyme C peptide was imprinted into polysiloxane scaffolds to investigate the epitope approach to molecular imprinting. Without competition, 8.95 11.53% of the lysozyme preferentially bound to the scaffolds, while under competition 1.85 9.47% bound to the scaffolds. Lastly, bone morphogenetic protein 2 (BMP-2) was imprinted into the polymer scaffolds. Results revealed that BMP-2 imprinted scaffolds bound 10.09 6.625% under noncompetitive conditions and a very small 0.65 4.55% during competition. Trends of preferential binding via peptide imprinting and BMP-2 imprinting can be seen, and show promise in future tissue engineering material applications and biomaterial compatibility.