Short Peptide Bioregulators: Matching Trade Names to Sequences

Short peptide bioregulators are some of the smallest molecules a peptide lab will handle: two to four amino acids, sold under coined names such as epitalon, pinealon, vilon and thymogen. For anyone receiving several of them in one order, those names are a problem, because none of them describes the molecule. Two of the best known are also so close in mass that a routine identity check cannot separate them. This guide sets out the sequences behind the names, explains the one near-collision that trips up mass spectrometry, and covers how to test and log these compounds reliably.

Trade names versus sequences

The names come from a single Russian research programme and are applied consistently within that literature, but they are coined labels rather than chemical nomenclature. Nothing in “pinealon” tells you it is Glu-Asp-Arg. For inventory and QC purposes, the sequence is the identifier and the name is a convenience.

Spelling also varies. Epitalon appears as epithalon and epitalone, for example. A receiving log keyed on the sequence avoids treating one compound as two, or two as one.

The epitalon and vesugen near-collision

Look at the table again: epitalon and vesugen sit 0.036 Da apart. Their average molecular weights, about 390.35 and 390.39, round to the same whole number.

The reason is residue arithmetic. An alanine residue (71.037 Da) plus a glycine residue (57.021 Da) totals 128.058 Da. A lysine residue is 128.095 Da. Swap Ala and Gly for Lys, drop a residue in the process, and the total barely moves. In elemental terms, lysine carries an extra CH4 and one fewer oxygen, and those nearly cancel.

What this means in practice:

• A nominal-mass or low-resolution instrument cannot tell them apart. Both give an [M+H]+ ion near m/z 391.
• High-resolution MS can. At mass 390, a 0.036 Da gap is roughly 90 ppm, well within the resolving power of Orbitrap or time-of-flight instruments.
• Chromatography can. A lysine-containing tripeptide and a glycine-ended tetrapeptide are retained differently, so co-elution with a reference standard settles the question.
• Tandem MS can. Fragment ions reveal the sequence directly, which is the most definitive check of all.

For a lab holding both compounds in inventory, this matters at receiving. A mislabelled or swapped vial would pass a low-resolution mass check. If your identity testing relies on nominal mass, add a retention comparison for these two.

Testing short peptide bioregulators by HPLC

Getting them to stick to the column

All six sequences are small, highly polar and carry several charges. Each has at least one glutamate or aspartate, half have lysine or arginine, and only thymogen has a large hydrophobic side chain. On a standard C18 gradient most of them elute at or near the void, where they are not separated from salts and solvent disturbances.

Labs deal with this in different ways: C18 phases designed for fully aqueous mobile phases, stronger ion-pairing agents such as heptafluorobutyric acid, or hydrophilic interaction chromatography (HILIC), which retains polar compounds well. Each approach gives different retention and selectivity, so purity figures for these compounds are harder to compare across labs than figures for longer peptides.

Seeing them with a UV detector

Only thymogen contains an aromatic residue. Its tryptophan gives useful absorbance at 280 nm and native fluorescence, so it is the easy one to detect. The rest rely on low-wavelength absorbance from peptide bonds, and a dipeptide has only one. Signals are weak, samples are often run at higher concentration, and a longer impurity will be over-represented relative to the main peak in area percentage. A mass-based detector such as CAD can be a helpful cross-check.

Why salt form matters more for tiny peptides

Most research peptides are isolated as salts, commonly acetate or trifluoroacetate. On a long peptide, the counter-ion is a small fraction of the weighed mass. On a dipeptide it is not. One acetate (about 60 Da) paired with vilon (275 Da) would account for roughly 18 percent of the salt’s mass, and some basic sequences carry more than one counter-ion.

That makes net peptide content, the proportion of the powder that is actually peptide, a bigger consideration for these compounds than for longer ones. When preparing analytical standards or comparing lots, check whether the certificate reports HPLC purity only or also gives peptide content and salt form. Those are different numbers answering different questions.

Receiving and logging a mixed bioregulator order

When several of these compounds arrive together, a short routine keeps records clean:

1. Log each line by full sequence in three-letter code, with the trade name as a secondary field.
2. Record the expected monoisotopic mass and note the epitalon and vesugen pair as needing more than a nominal-mass check.
3. Note the salt form and whether the terminus is free acid or amide, since both change the calculated mass.
4. Match each vial to its certificate by cap and crimp colour and record the pairing.
5. Store the lyophilised vials cold and dry, grouped by lot.

Where this leaves identity testing

For these compounds, a certificate is unambiguous when it gives the sequence, a mass that matches it, and the method used to confirm identity. For epitalon and vesugen in particular, look for high-resolution mass data, tandem MS or a retention comparison against a standard.

From this group, Bulk Peptides lists epitalon (epithalon) in 10 mg vials. Our products go through third-party HPLC purity testing, some certificates are published on the certificates of analysis page, and cap and crimp colours tie each vial to its certificate.

Short peptide bioregulators and every other compound we list are research chemicals for in-vitro laboratory work only. They are not medicines and are not to be used in humans or animals.