PEAQ-DSC Automated

Differential Scanning Calorimetry (DSC) is a powerful analytical technique for the characterization of the thermal stability of proteins and other biomolecules. These molecules often undergo thermally induced conformational changes, such as unfolding. When a protein unfolds, non-covalent bounds break and a new, probably non-functional structural arrangement is created. Differential scanning calorimeters measure the absorbed heat required for rearranging the conformational structure.

The MicroCal PEAQ-DSC Automated system available in our facility provides high throughput, highly sensitive protein stability analysis with fully automated cell filling and cleaning functions for walk-away operations. DSC is most commonly used in biopharmaceutical development and manufacture for predicting and optimizing a product´s shelf life, the optimization of purification and manufacturing conditions, the assessment of biosimilarity and batch-to-batch comparability. In addition, the label-free stability data obtained by DSC can be applied for general stability studies, sensitive and reproducible analysis of protein folding and unfolding, characterization of lipids and detergent micelles etc.

The thermal core of the system consists of a sample cell containing the sample of interest and a reference cell with buffer solution. Both cells are enclosed within an insulating jacket where they are always kept at the same temperature. During measurement, they are heated at a constant scanning rate. The absorption of heat that occurs when a protein unfolds causes a temperature difference (∆T) between sample and reference cell, resulting in a thermal gradient across the Peltier units. The voltage that is created is converted into electric power and used to return ∆T to zero. The electric power supply required to maintain both sample and reference cell at the same temperature is measured by the instrument and plotted against the temperature. Since protein unfolding is an endothermic event, it appears as a positive displacement in the thermogram. The midpoint of this protein melting transition is the T_m and the area under the curve represents the enthalpy (∆H) of the unfolding process. It can also be used to determine the change in heat capacity (∆C_p) of denaturation. From the results obtained by DSC, factors that contribute to folding/unfolding and stability of biomolecules can be explained. These include hydrophobic interactions, hydrogen bonding, conformational entropy and the physical environment. The higher the thermal transition midpoint T_m, the more stable is the molecule.