Many natural peptide hormones end in an amide rather than an acid: the body amidates them in the last step of their maturation. That modification removes the negative charge at the end of the chain and changes how the molecule fits its receptor.
In synthetic peptides amidation is used for two purposes: to faithfully reproduce the natural hormone when it is amidated, and to increase resistance to carboxypeptidases, enzymes that break down chains from their C-terminal end.
On a data sheet it is recognised by the –NH₂ suffix (for example, D-Arg-Dmt-Lys-Phe-NH₂ in SS-31). Amidation changes the molecular formula and lowers the weight by about 1 Da compared with the acid form, a difference that mass spectrometry must detect.
An amidated and a non-amidated version of the same peptide are not interchangeable: they differ in mass, charge and often in activity. The identity analysis must match the declared form.
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).