Tetrapeptide
Definition
Four residues. Epithalon (Ala-Glu-Asp-Gly) and several of the bioregulators are tetrapeptides.
What this means for research sourcing
Structure and identity terms are what a certificate of analysis is written in. Every Volta compound ships with its sequence, molecular weight and measured purity, so these terms map directly onto the specification on the product page.
Related Terms in Chemistry & Structure
Pentapeptide
Five residues. The prefix is a residue count and nothing more, which is worth saying because cosmetic ingredient names lean on it heavily.
Pentadecapeptide
Fifteen residues. BPC-157 is routinely described this way in the literature, so the word is more common in peptide writing than its length would suggest.
Disulfide Bond
A covalent bridge between the sulfur atoms of two cysteine residues. It staples distant parts of a chain together and holds a fold in place, and reducing conditions break it, which is one way a peptide loses activity without losing mass.
Cysteine
The amino acid whose thiol side chain forms disulfide bridges. It is also one of the three residues most readily oxidised, so a sequence containing it has a predictable degradation liability.
Peptide Fragment
A section cut from a longer peptide or protein and studied on the assumption that it carries part of the parent's activity. The assumption is not automatic: a fragment can retain binding and lose function, or do neither. HGH Fragment 176-191 is named for the residues it spans.
Peptidomimetic
A molecule built to reproduce what a peptide does without being one, often by replacing amide bonds with linkages proteases cannot cut. The point is stability and absorption rather than novelty of target.
Synthetic Peptide
A peptide assembled chemically, in practice almost always by solid-phase synthesis, rather than extracted from tissue or expressed in cells. Research peptides are overwhelmingly synthetic, which is also why their identity can be checked against a known sequence.
Solid-Phase Peptide Synthesis (SPPS)
The standard way peptides are made: the chain is anchored to a resin bead and extended one protected residue at a time, then cleaved off and purified. Coupling efficiency compounds over the chain, so yield and purity both fall as length rises.