Chemically synthesized peptides usually carry free amino and carboxyl termini unless otherwise specified. N-terminal acetylation and C-terminal amidation are common terminal modifications used to alter charge, improve stability, and more closely mimic native peptide or protein fragments.
Acetylation caps the N-terminus and removes the free terminal positive charge contribution.
Amidation converts the free terminal carboxyl group to an amide, reducing terminal negative charge.
Because terminal charges are reduced, acetylation and amidation often make peptides less soluble than their unmodified counterparts.
These terminal modifications may help the peptide better resemble its native biological context and can sometimes improve functional performance.
These modifications must be requested before synthesis. They are not simple post-synthesis changes that can be added later without resynthesizing the peptide.
Terminal acetylation and amidation can improve biological relevance but may also change solubility and handling. This matters more for hydrophobic, long, or assay-sensitive peptides.
Analyze your sequence before deciding on terminal modifications: