Glossary
Synthetic (SPPS)
Synthetic peptides are built chemically on resin beads, one amino acid per cycle. How this shapes purity, allows non-natural residues and defines a good COA.
In a peptide catalogue, "synthetic" almost always refers to solid-phase peptide synthesis (SPPS), in which the sequence grows one amino acid per cycle on a solid polymer support before cleavage and purification. Practically every research peptide shorter than about 50 residues is made this way — from BPC-157 and ipamorelin to semaglutide and the nootropic sequences.
What chemical production offers
The chemistry brings three properties. Control is total — non-natural units — D-amino acids, Aib, PEG chains, acetyl end-caps — can be put exactly where they are wanted, something biological expression cannot achieve. Reproducibility is high, since an identical protocol delivers an identical molecule free of the batch variation that living cells introduce. And there are no contaminants from a host organism, meaning bacterial endotoxin is not built into the process the way it is for recombinant products.
The typical impurities are chemical instead: deletion sequences caused by incomplete couplings, truncated chains, protecting groups that were not fully removed, and TFA left over from cleavage. A COA with its HPLC chromatogram exists to quantify precisely these.
Related terms
purity · linear peptide