Novel Uses in Protein Production, Processing, Analysis, and Formulation

Amino acids are the building blocks of proteins, but they also have nutritional and therapeutic values and are becoming popular as dietary supplements (1). These molecules also find wide applications in protein research and biotechnology product development. The idea that they could have value in such applications stems from the use of certain amino acids and other low– molecular-weight organic compounds (called osmolytes) by various organisms to protect their cells from water stress, e.g., in high salt concentrations, desiccation, or freezing conditions (2). Glycine, alanine, serine, and proline accumulate at high concentrations in cells to raise their intracellular osmotic pressure. Despite high concentration, they are compatible with the function and activity of most proteins and are termed compatible solutes. Osmolytes do not bind to proteins, but they do stabilize them (3). These properties make amino acids useful reagents in protein research and biotechnology applications. Most proteins are fairly unstable in aqueous solution (4). Many factors in their natural environment protect proteins from unfolding and aggregation. Biotech scientists look for the conditions or additives that will stabilize isolated, purified proteins. Certain amino acids can be used for stabilizing proteins in aqueous solutions (5). Removing water (by lyophilization) offers another option. Glycine is widely used as a stabilizing and bulking agent in dried protein powders (6). Formation of stable cakes during and after freezedrying is essential to successful lyophilization, long-term storage of dried protein products, and ultimately rapid dissolution during their reconstitution (7). Histidine is often used as a buffer component for lyophilization because of its stabilizing properties during freezing and drying as well as in dried powders (8). Arginine finds extensive uses in refolding of recombinant proteins. It can be an effective amino acid in production, processing, and characterization of proteins (including antibodies).