Calorimeters

Knut Langsetmo, Ph.D., Instructor

Heat is a fundamental part of all chemical reactions, including the reactions that take place in a living organism. Therefore, the ability to measure the heat absorbed or released during a reaction provides us with a universal means to follow biological processes. As the name suggests, a calorimeter measures heat. We have the capability to make three different kinds of heat measurement. With a Differential Scanning Calorimeter (DSC), we can measure changes in the heat capacity of a solution as it is heated. This is typically used to determine the stability of a whole macromolecule or its parts. An Isothermal Titration Calorimeter (ITC) measures the heat of interaction between molecules; from such measurements we can determine how tightly they interact with each other and what type of forces are involved. Finally, with a Pressure Perturbation Calorimeter (PPC), we can measure the relationship between heat and pressure, the thermal coefficient of expansion. From this measurement over a range of temperature, we can determine the change in volume during a reaction, further characterizing its basic nature.

It has long been thought that there is a relationship between the structure of a macromolecule and its function. Understanding the link between them would greatly improve our ability to understand the causes of diseases and to develop new treatments. Key to understanding this link is knowing the various contributions to the energy of a given reaction. In this regard, calorimetric methods are particularly useful since they measure the heat involved in biological processes without modifying the components themselves. From measuring the heat involved, we can have a more fundamental description for the structure-function relationships of macromolecules.

Through a successful grant proposal, BBRI scientists recently obtained funding from the NIH for a Calorimetry Workstation, which consists of DSC, ITC and PPC instrumentation. These instruments allow us to determine the energetic contributions within and between biological macromolecules such as proteins and DNA.

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Calorimetric methods measure the heat involved in biological processes without modifying the components themselves.