A major portion of most biochemical investigations involves the purification of the materials under consideration because these substances must be relatively free of contaminants if they are to be properly characterized. This is often a formidable task because a typical cell contains thousands of different substances, many of which closely resemble other cellular constituents in their physical and chemical properties. Furthermore, the material of interest may be unstable and exits in vanishingly small amounts. Typically, a substance that comprises less than 0.1% of a tissue’s dry weight must be brought to approximately 98% purity. Purification problems of this magnitude would be considered unreasonably difficult by most synthetic chemists. It is therefore hardly surprising that our understanding of biochemical processes has by and large paralleled our ability to purify biological materials.

This biochemical categories presents an overview of the most commonly used techniques for the isolation, the purifications, and to some extent, the characterization of proteins as well as other types of biological molecules. These methods are the basic tools of biochemistry whose operation dominates the day to day efforts of the practicing biochemist. Furthermore, many of these techniques are routinely used in clinical applications. Indeed, a basic comprehension of the methods described here is necessary for an appreciation of the significance and the limitations of much of the information presented in this category. This article should therefore be taken as reference material to be consulted repeatedly as the need arises while reading other articles.