Biophysical chemistry applies fundamental knowledge and techniques from the field of physical chemistry to large molecules of biological interest, such as proteins and their interactions. The shape, interactions, stability and chemical reactions of In the context of biological molecules, physical chemistry provides the theory to predict various kinds of energy transfer between large molecules in the cell. Binding of one protein to another, chemical reactions, and changes in shape can be described in terms of their likelihood and their stability.

In all living things, metabolism of nutrients and synthesis of new molecules are controlled by enzymes. Most enzymes are proteins that facilitate chemical reactions. They do this by binding to the starting materials (substrates), and lowering the energy barrier required for the chemical reaction to take place-- this is called catalysis. Starting materials bind to the catalytic site of the enzyme and are converted to products.

Enzymes in key chemical pathways have evolved elaborate control mechanisms that ensure that chemical reactions occur at the proper rates, depending on environmental conditions. Allosteric regulation is one of the most interesting types of enzymatic control, because it involves a second site on the enzyme, known as the allosteric site-- which controls enzyme activity by binding to smaller molecules. The smaller molecules serve as signals, and can be either positive or negative regulators of the rate of conversion of starting materials to products. Biophysical chemistry provides a powerful way to study these interactions in molecular detail.

Chaperones are proteins that help proteins to fold into their characteristic, active shapes. Heat shock proteins, as the name implies, appear when cells are shocked by heat, and often involve repair of basic cellular functions. They provide useful model systems for studying cellular events in a controlled laboratory setting.