Epitalon: structure and analysis

What it is

Epitalon, also written Epithalon, is a synthetic tetrapeptide with the sequence Ala-Glu-Asp-Gly. Four residues makes it one of the shortest compounds in this catalogue.

Two of those four residues are acidic — glutamic acid and aspartic acid — which makes the molecule strongly polar and, at neutral pH, negatively charged.

How it is produced

Assembled by solid-phase peptide synthesis: the chain is built one residue at a time on an insoluble resin support, then cleaved from the resin, deprotected and purified — most commonly by reversed-phase high-performance liquid chromatography. The purified material is lyophilized to a dry solid.

The impurity profile that appears on a certificate is a record of where that process was imperfect: deletion sequences from an incomplete coupling, truncated chains, and species retaining a protecting group.

Confirming identity

Mass spectrometry confirms the four-residue sequence. For a tetrapeptide the expected mass is low and the measurement correspondingly precise.

The aspartyl-glycine motif at the third and fourth positions is worth noting for identity purposes, because it is a site where rearrangement can produce a species of identical mass.

Analytical considerations

That aspartyl-glycine sequence is a recognised site for succinimide formation and subsequent isoaspartate rearrangement in solution. An isoaspartate product is isobaric with the intended peptide — the same molecular mass — so mass spectrometry alone cannot distinguish them, and chromatographic separation carries that burden.

The compound is also very weakly retained on reversed-phase columns given its size and charge, so the analytical method has to be built for a small polar peptide rather than adapted from one designed for longer sequences.

What its certificate reports

A certificate for a lot of this material names the lot, names the issuing laboratory, and states for each parameter both the method used and the specification the result was measured against. Identity and purity are the two core results; net peptide content states how much of the fill weight is actually peptide.

A certificate belongs to a lot, not to a product line. When a new lot is released it is tested again, and the certificate published against it is that lot's certificate — a previous lot's result is never carried forward.

Research use only

This page describes structure and analysis. It makes no claim about what this compound does, and none should be inferred from it. Material is supplied for laboratory research use only: it is not a drug, food, dietary supplement, cosmetic or medical device, it is not for human or veterinary consumption, and no dosing, administration or reconstitution guidance is provided for any such use.