What is solid phase peptide synthesis (SPPS)

In general, to synthesize a peptide, a peptide bond between two amino acids will need to be formed. The exact size of peptides that can be synthesized is not well defined, but it usually refers to flexible chains of up to 30 to 50 amino acids. However, peptides with up to 100 amino acids within the chain can now be synthesized as well.

The basic concept in solid-phase peptide synthesis is the step-wise construction of a polypeptide chain attached to an insoluble polymeric support. This approach permits unreacted reagents to be removed by washing without loss of product. Synthesis of the peptide chain proceeds from the carboxyl end of the amino terminus of the polypeptide. The carboxyl moiety of each incoming amino acid is activated by one of several strategies and couples with the α-amino group of the preceding amino acid. The α-amino group of the incoming residue is temporarily blocked in order to prohibit peptide bond formation at this site. The residue is de-blocked at the beginning of the next synthesis cycle. In addition, reactive side chains on the amino acids are modified with appropriate protecting groups. The polypeptide chain is extended by reiteration of the synthesis cycle. Excess reagents are used to drive reactions as close to completion as possible. This generates the maximum possible yield of the final product.

After fully assembling the peptide the side-chain protecting groups are removed, and the peptide is cleaved from the solid support, using conditions that inflict minimal damage on labile residues. The product is analyzed to verify the sequence thereafter. The synthetic peptide is usually purified by gel chromatography or HPLC.