Thousands of different types of proteins occur in biological organisms. They are responsible for catalyzing and regulating biochemical reactions, transporting molecules, the chemistry of vision and of the photosynthetic conversion of light to growth, and they form the basis of structures such as skin, hair and tendon. Protein molecules have remarkable structures. A protein is a linear chain of a particular sequence of monomer units. A major class of proteins, globular proteins, ball up into compact configurations that can have much internal symmetry. (See figure 1.) Each globular protein has a unique folded state, determined by its sequence of monomers.
Understanding and predicting the three‐dimensional structures of proteins from their sequences of amino acids requires both basic knowledge of molecular forces and sophisticated computer programs that search for the correct configurations.