Friday, October 21, 2011: 10:10 AM
101 F (Minneapolis Convention Center)
The long-term stability of biological molecules such as proteins can be significantly enhanced by encapsulation in organic glasses. Of particular interest is the disaccharide trehalose, ubiquitously found in nature and known to protect organisms during harsh environmental conditions. Trehalose is routinely used in pharmaceutical formulations to augment the shelf life of labile molecules. Glycerol, also a known bioprotectant, has been shown to enhance the protective nature of trehalose glasses when present at low concentrations. Past studies have argued that glycerol acts as an antiplasticizer that decreases the glass transition temperature but increases the elastic moduli of the resulting glass. The trehalose/glycerol system thus offers an interesting case study on the properties of a glass that are responsible for the stabilization of embedded proteins. Using Monte Carlo and molecular dynamics simulations, we examine the behavior of a few select proteins encased in different compositions of trehalose/glycerol binary glasses. The proteins are selected to provide a variety of structural motifs and electrostatic environments. Short-time dynamic information such as structural relaxation times and Debye-Waller factors (often used as a measure of rigidity) are analyzed. Local elasticity is also investigated. Our simulations show that, even at small concentrations, glycerol can alter significantly the local environment of encapsulated proteins. Our results also reveal that significantly different behaviors arise depending on the local stiffness of the material and the local hydrophilicity of distinct chemical motifs.