Solid-phase peptide synthesis

Abstract

Peptides play a central role in numerous biological and physiological processes. They also may be critical for research endeavors in the post-genomic and proteomic era that is characterized by a vast array of new predicted protein sequences. To elucidate the biological function of putative proteins it is important to have facile access to their synthesis. Today we have almost routine technologies for the chemical synthesis of small peptides and proteins, and have made significant progress toward the synthesis of larger proteins via chemoselective ligation (1-5) and expressed protein ligation (6-8). Although these new approaches are impressive and have been employed successfully for the synthesis of many proteins, general protein chemical synthesis is still not routine and there are still many challenges that remain to be confronted. Methods for synthesizing peptides are divided conveniently into two categories: solution and solid-phase. Classical solution chemistry involves the preparation of fully protected peptide segments and their subsequent condensation in organic solvents for the convergent synthesis of large polypeptides. Solid-phase peptide synthesis (SPPS) uses an insoluble polymeric support for sequential addition of side-chain protected amino acids. The resulting peptide is then cleaved from the resin, typically under acidic conditions. SPPS has numerous advantages over the classical solution procedure, such as automation of the elongation reaction, independence from solubility problems, and minimization of side product formation. On the other hand, in the classical solution procedure, the products can be monitored and purified at each step in the reaction, potentially leading to easier isolation of the desired final peptide. Therefore, solution synthesis retains value in large-scale manufacturing, and for specialized laboratory applications, whereas solid-phase chemistry remains the method of choice in research. In this chapter, an overview of SPPS is presented. For brevity, only commercially available reagents and derivatives utilized for synthesis will be considered here. The reader is referred to a number of comprehensive reviews for further discussion of peptide synthesis techniques (9-22). © 2008 Humana Press.