Protein Encapsulation in Mesoporous Silicate:  The Effects of Confinement on Protein Stability, Hydration, and Volumetric Properties

• Published in: Journal of the American Chemical Society Vol. 126; no. 39; pp. 12224 - 12225
• Main Authors: Ravindra, Revanur, Zhao, Shuang, Gies, Hermann, Winter, Roland
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06-10-2004
• Subjects: Biological and medical sciences; Calorimetry, Differential Scanning; Enzyme Stability; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Isoelectric Focusing; Kinetics; Miscellaneous; Molecular biophysics; Physico-chemical properties of biomolecules; Pressure; Protein Conformation; Ribonuclease, Pancreatic - chemistry; Silicates - chemistry; Water - chemistry; Encapsulation; Differential scanning calorimetry; Temperature dependence; Enzyme; Pore structure; Chemical stability; Aluminosilicates; Thermodynamic stability; Esterases; Molecular sieve; Thermal expansion coefficient; Hydrolases; Pancreatic ribonuclease; Thermodynamic properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja046900n

On the basis of the predictions of statistical−thermodynamic models, it is postulated that excluded volume effects may play a significant role in the stability, interaction, and function of proteins. We studied the effects of confinement on protein un/refolding and stability. Our approach was to encapsulate a model protein, RNase A, in a mesoporous silica, MCM-48, with glasslike wall structure and with well-defined pores to create a crowded microenvironment. To the best of our knowledge, this is the first report where pressure perturbation and differential scanning calorimetric techniques are employed to evaluate the stability, hydration, and volumetric properties of the confined protein. A drastic increase in protein stability (∼30 °C increase in unfolding temperature) is observed. The increase in stability is probably not only due to a restriction in conformational space (excluded volume effect due to nonspecific interactions) but also due to an increased strength of hydration of the protein within the narrow silica pores.