BSA Aggregation in Trehalose-Water Systems

Introduction Recent studies [1] on ternary protein-trehalose-water samples have shown that the protein thermal denaturation temperature is linearly correlated with the glass transition temperature of the system, despite the quite large temperature difference between the two processes. In such studies it is stated that the collective, long range properties of the matrix that regulate the glass transition are strictly correlated with local features on which the denaturation of the protein depends. In order to ascertain whether an analogous correlation exists between the effects of trehalose on the protein’s aggregation process and the glass transition temperature of the system, we performed Light Scattering measurements on thermal aggregation of Bovine Serum Albumin (BSA) in presence of trehalose at various concentrations. Experimental We used Static and Dynamic Light Scattering to study the thermal aggregation of BSA in buffered aqueous solution, at 0.1% w/w protein concentration and in presence of trehalose, whose weight concentration was varied from 0 to 50 % trehalose/(trehalose+water). Measurements were performed in the temperature range 50 °C – 80 °C. Results Addition of trehalose appears to cause temperature shifts of the entire process towards higher values. In particular, the effects of trehalose on the temperature of the aggregation process appear to be linearly correlated with the effects of the sugar on the glass transition temperature. The latter quantity was estimated through the Gordon-Taylor equation [2] with already reported parameters [1]. Addition of sugar is also responsible for shape changes in plots of scattered light intensity versus temperature during temperature scan. Such changes reflect differences in the aggregation process, which can be sorted out through a suitable analysis of the increase of the hydrodynamic radius during the temperature scans. In particular, we determined the fractal dimension of the aggregates, which gives information on their packing. References 1. G. Bellavia, G. Cottone, S. Giuffrida, A. Cupane, L. Cordone, J. Phys. Chem. B. 113, (2009) 11543–11549. 2. M. Gordon, J. S. Taylor, J. Appl. Chem. 2, (1952) 493–500.