Epithalon peptide: sequence, molecular data, certificate of analysis, 10 mg vial

Epithalon, also written epitalon and sometimes abbreviated to its one-letter sequence AEDG, is a synthetic peptide of four residues: alanine, glutamic acid, aspartic acid, glycine.

It was designed in the 1990s at the St Petersburg Institute of Bioregulation and Gerontology, in the laboratory of Vladimir Khavinson, as a synthetic counterpart of epithalamin, a pineal extract that the same institute had worked on since the 1970s.

The name is a contraction of the extract's name; the two spellings are the same molecule.

Four residues is very small. For comparison, KPV is three, SS-31 is four, Selank is seven, and DSIP is nine.

At this length a synthesis run produces almost no deletion by-products, and what a certificate has to look for is a single isomer, described below, rather than a family of shorter chains.

Everything sold under the name today is made by solid-phase synthesis.

Nothing is extracted from a gland: the compound is a defined four-residue molecule with one mass and one CAS number, and the extract it was modelled on is not. Research use only. Not for human or veterinary use.

Three of the four residues carry a carboxyl: the side chain of glutamic acid, the side chain of aspartic acid, and the C-terminus of glycine.

Against them stands a single amine, the N-terminus of alanine.

The peptide is therefore strongly acidic, dissolves in plain water without a solvent trick, and behaves on a reverse-phase column like the very polar compound it is: it elutes early, close to the solvent front, and a chromatogram needs an ion-pairing acid in the mobile phase to hold it on the column at all.

The absence of an aromatic residue matters for the certificate.

Tryptophan, tyrosine and phenylalanine are what a laboratory reads at 280 nm; epithalon has none of them, so the only signal is the peptide bond itself at 210 to 215 nm.

A certificate showing a 280 nm trace for this compound is showing a trace of nothing.

Residues three and four of the sequence are aspartic acid followed by glycine.

In peptide chemistry Asp-Gly is the best-known motif for a side reaction called aspartimide formation: during synthesis, or slowly in solution, the side-chain carboxyl of the aspartic acid attacks the backbone, closes a five-membered ring, and that ring reopens on either side.

One of the two products is the original peptide; the other is the beta-aspartyl isomer, in which the glycine is attached to the side-chain carboxyl of the aspartic acid instead of its alpha-carboxyl.

The isomer has the same formula and the same mass, 390.3, as the compound on the label. Mass spectrometry cannot tell them apart; only the chromatogram can, and the two elute close together.

This is why the HPLC line on an epithalon certificate deserves more attention than usual: a second peak riding on the shoulder of the main one is this isomer, and it belongs in the impurity total even though the mass line reads perfectly.

A synthesis that uses a protected aspartic acid building block chosen for this motif, and a cleavage kept short and cold, produces lots where the isomer stays below 1 %.

A certificate that reports a single peak above 98 % on a four-residue chain has, in practice, answered the question.

A batch certificate for a tetrapeptide is short, and four lines carry the whole document.

• Purity by reverse-phase HPLC, read at 210 to 215 nm, one main peak with its area against total peak area. Above 98 % is ordinary for a four-residue chain; the by-product to look for is the beta-aspartyl isomer described above, not a deletion sequence.
• Mass by mass spectrometry. The protonated molecule at m/z 391.1 [M+H]⁺, often with the sodium adduct at 413.1; in negative mode, which suits an acidic peptide, the deprotonated molecule at 389.1. All reconstruct to 390.3. A value 57 lower means the glycine is missing; 71 lower, the alanine; 129 lower, the glutamic acid.
• Net peptide content, by amino-acid analysis or nitrogen determination. With a single basic site, the acetate salt carries one acetate per molecule, 60 g against 390: a pure lyophilized lot cannot exceed 87 % net content, and 75 to 85 % after residual water is the realistic band. A 10 mg fill therefore holds roughly 7.5 to 8.5 mg of peptide; the arithmetic is set out on the bacteriostatic water calculator.
• Lot number, date, laboratory name, and a photograph of the labeled vial. The four fields that tie the document to the object in hand rather than to a production run somewhere.

How to read each field, and how to check a report number against the laboratory itself, is in how to read a peptide COA and how to read a Janoshik test report. Certificates are published per lot in the COA library.

Epithalon is supplied in one size, a 10 mg vial: 10 mg of a 390-dalton peptide is 25.6 micromoles, a generous bench quantity for a compound this small, and the price per milligram of a four-residue synthesis makes a smaller fill cost nearly as much to fill, label and certify.

The catalog card at the top of this page reads the live price and the live stock from the catalog, so it never contradicts the epithalon product page; volume tiers apply from two vials, and the subscription price applies to every delivery.

The other short regulatory peptides in the catalog are thymalin, from the same St Petersburg institute, and the two Moscow heptapeptides Selank and Semax.

What the price includes at OXpeptides: a sealed, labeled vial from a tested lot, its batch COA, and a replacement if the parcel arrives lost or damaged.

Ships from France (EU) and California (US) · tracked, tracked: $19, free from $150.

See epithalon in the catalog →

• Temperature: −20 °C for long-term storage; 2 to 8 °C for periods of a few weeks.
• Light and moisture: keep the vial sealed and in its box. Let a cold vial reach room temperature before it leaves its bag, so no condensation forms on the glass and none of it reaches the powder. An acetate salt with three carboxyls is hygroscopic.
• Shelf life: 24 months for a sealed lyophilized vial stored as above; the date printed on the label governs.
• In solution: refrigerated, protected from light, and split into aliquots at the moment it is made. The Asp-Gly motif is the reason a solution of this peptide should not stand: the isomerisation described above proceeds slowly in water at neutral pH, and a solution kept for weeks is a mixture of the two isomers.

Ambient shipping over a few days does not degrade a sealed lyophilized powder, which is why research peptides travel without cold packs. Compound by compound, the rules are in lyophilized peptides: storage and shelf life.

"Epithalon" returns twelve thousand searches a month in the US, split between the two spellings, and the first page is a mix of encyclopaedia entries, journal abstracts and research suppliers.

The listing worth reading answers five questions on the page itself.

1. Is the sequence printed? Ala-Glu-Asp-Gly, four residues. A page that names the compound and never writes the sequence has nothing to check.
2. Is the mass stated, and is it 390.3? A page giving another figure is describing a different molecule or copying a different data sheet.
3. Is there a batch certificate from a named independent laboratory, with a lot number matching the vial, a date, a photograph of the labeled vial, and an HPLC trace read at 210 to 215 nm rather than 280?
4. Is the vial sealed, labeled and lyophilized, with a stated size? A listing that sells a solution of this peptide has made a choice about the isomer on the buyer's behalf.
5. Does the page describe the reagent only (sequence, mass, purity documentation, storage), with research use only stated plainly? A supplier who publishes usage content is a supplier easy to shut down, and the parcel in transit belongs to the buyer.

The seven-point method, including what a re-used or edited certificate looks like, is in how to check a peptide supplier. The US-wide checklist is in where to buy research peptides in the US.