Synthetic and recombinant production

Chemical synthesis

Chemical synthesis builds the chain one residue at a time and suits sequences up to a few dozen residues. It gives exact control over the sequence, including non-natural residues and modifications that a cell could not make.

Its characteristic impurities are chain-related: deletion sequences where a coupling step failed, truncated chains, and residues where a protecting group was not fully removed. It also leaves residual solvents and reagents, which purification is designed to remove.

Recombinant expression

Recombinant production inserts the coding sequence into a host organism and lets the cell assemble the chain. It handles long sequences that synthesis cannot, and produces correctly folded protein where folding matters.

Its impurities are biological: host-cell proteins, host DNA, and endotoxin where a bacterial host is used. These are removed by a different purification strategy and tested for differently.

Why it appears on documentation

The production route determines which contaminants are plausible, and therefore which tests are meaningful. Endotoxin testing matters for a recombinant product in a way it does not for a synthetic tripeptide.