A differential scanning calorimeter is an instrument that measures how samples respond to changes in temperature. One sample is used because the changes it undergoes when the temperature rises or decreases are already known. It is used as a comparison to another sample, for which the response to changes in temperature is being tested. Each sample is kept in a container called a crucible, and the materials the device is designed to test are usually biological molecules, such as nucleic acids or proteins.
Testing done using the differential scanning calorimeter is based on the field of differential scanning calorimetry (DSC), which involves the analysis of how stable biological molecules and systems are. The energy associated with molecules unfolding is measured as well as their equilibrium between being folded or unfolded. When molecules change states or the sample melts or solidifies, the changes in their heat capacity allow researchers to classify them. Molecules are considered to be more stable when temperatures are higher and the material is in a state in which at least half the molecules are in transition.
To measure any new sample, it has to be compared to the rate of change for another type of material. The temperature differences are also measured when the containers are empty, and these are used as a baseline to calculate a specific heat capacity. The rate at which the temperature changes is the same for both containers and occurs over the same temperature range. Heat capacities from 212°F to 2,192°F (100°C to 1,200°C) are measured. A differential scanning calorimeter can also measure phase changes that occur in a 68°F to 2,732°F (20°C to 1,500°C) temperature range.
Heating rates are usually constant, but minor changes in the rate, or oscillations, can be performed with a modulated differential scanning calorimeter. In one scan, this feature lets researchers have a clearer understanding of a substance’s heat capacity and also measure reversible and non-reversible effects of heat on a sample during the time the oscillation takes place. The instrument provides a more sensitive method of characterizing molecules.
Differential scanning calorimeter systems are generally used for characterizing polymers as well as the stability of proteins. They are used in specialized fields, such as protein engineering, studying antibodies, and understanding the nature of nucleic acids, lipids, and membranes. Molecular interactions can be measured on a very small scale, and scientists can also study how structural alterations in molecules have an effect over certain temperature ranges and rates of change.