ABSTRACT
Proteins are linear heteropolymers that incorporate a sequence of the 20 naturally occurring amino acids. They vary greatly in length, from just a few amino acids to many thousands of residues.* The larger extreme of the range is usually confined to long (extended) fibrous proteins in which, typically, a short unit is repeated many times. This unit can be from as small as three residues (as in collagen) to about 100 (as in the muscle protein titan). The proteins that are of primary interest in this chapter, however, lie in the middle of the range, with lengths of several tens of residues to several hundred. They tend to have more compact dimensions and are accordingly referred to as globular.
