Synthetic peptide is a highly purified, manufactured, biochemical product used in research applications like cancer diagnosis, drug discovery, vaccine development and epitope mapping. Peptides are produced by a process called solid-phase synthesis. The peptide sequence remains covalently attached to a solid support resin during synthesis, while other soluble chemicals that are not necessary for the peptide synthesis are removed by filtration and washing. This approach allows for a much faster reaction than is possible using conventional solution-phase synthesis.
During peptide synthesis, a variety of chemical treatments are used to modify the functional groups on the amino acids to enable coupling and subsequent cyclization of the resulting chain. These treatment methods are referred to as protecting groups. Some of these are acid labile (such as Bzl and Boc) while others are base labile (Fmoc, Fmse, Tmsec), and some are fluoride labile (tBu). All of these protect the amino acids from cleavage during peptide synthesis, and are subsequently cleaved in a separate step called deprotection or coupling.
Cleavage is an important and critical step in the peptide synthesis process. During this process, the peptide-bound resin is exposed to a reagent that splits the peptide chain into its constituent amino acids. This cleavage is a highly competitive reaction, and unless the correct reagents are selected for the cleavage cocktail, it can result in an irreversible side reaction that will affect the desired peptide.
During peptide synthesis, the carboxyl groups of the incoming amino acids are linked to the N-terminus of the growing peptide chain, a process known as C-to-N synthesis. This is the opposite of protein synthesis, in which the N-terminus is coupled to the carboxyl group of the first amino acid added.