Selank: A Research Primer

Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as an analog of the naturally occurring peptide tuftsin. It carries CAS number 129954-34-3 and the molecular formula C33H57N11O9, and it turns up in the neuropeptide and behavioural branches of the research literature.

This is an identity primer. It covers what the molecule is, what the label figures refer to, which corners of the published literature cite it, and how it is stored and verified as a laboratory material.

What Selank is

Selank is fully synthetic, seven amino acids long, and assembled residue by residue rather than isolated from any tissue.

Its design starts from tuftsin, a four-residue peptide with the sequence Thr-Lys-Pro-Arg. Tuftsin was named after Tufts University, where it was first characterised, and it occurs endogenously as a fragment released from a larger immunoglobulin. Selank keeps that four-residue core and adds a Pro-Gly-Pro extension on the C-terminal end. Those three extra residues are the whole structural difference between the two molecules, and they are the reason Selank is written up as a tuftsin analog rather than as tuftsin. A proline-glycine-proline cap is a familiar motif in peptide chemistry for making a short chain more resistant to enzymatic cleavage, which is a structural characteristic of the molecule.

The accurate one-line class for Selank is a synthetic tuftsin analog, or more plainly a heptapeptide. Both describe the same compound.

The chemistry

The identity data is what stays fixed from one supplier to the next, so it is the first thing to reconcile against any label or certificate.

• CAS number: 129954-34-3
• Molecular formula: C33H57N11O9
• Molecular weight: approximately 751.9 g/mol
• Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP)
• Class: synthetic heptapeptide, tuftsin analog

The single-letter sequence TKPRPGP and the three-letter form say the same thing; different papers and certificates use one or the other. A name can be transcribed a dozen ways and a formula can pick up a typo, but the CAS registry number is unambiguous, so match that first when you are checking that two sources describe the same molecule. If a molecular-weight figure looks off by a small amount, confirm whether it was calculated for the free peptide or a salt form, since that accounts for most honest discrepancies.

Where it appears in the research literature

Selank is referenced mainly in neuropeptide research and in behavioural research, the latter sometimes filed under neuropharmacology.

These are subject areas, not findings. Naming the field a compound has been studied in tells you where to look; it says nothing about what any study reported. For the primary sources themselves, the sequence and CAS number above are the search terms that will surface them faster than any trade name. The tuftsin connection is a useful second thread to follow, since a good deal of the relevant chemistry is indexed under the parent peptide.

How it is supplied and handled

Selank is supplied as a lyophilized solid, meaning it has been freeze-dried into a dry powder.

Peptides ship in this form because a dry solid survives transit far better than a solution does. Store it cold, at around -20C, keep the vial sealed until you are working with it, and limit its exposure to light, moisture, and repeated freeze-thaw swings. Kept cold and sealed, a lyophilized peptide is stable over long stretches. A freeze-dried vial often contains a small amount of bulking agent so there is a visible cake to work with, and an accurate certificate accounts for that filler when it reports mass. None of this is preparation guidance; it is how the reagent is kept intact on a shelf.

How the lots are tested

For each lot it stocks, Kits Peptides sends a sample to an independent third-party laboratory before the batch is sold. Two measurements carry the weight. Purity is read by HPLC at 220 nm, the wavelength where the peptide bond absorbs, and identity is confirmed by mass spectrometry, which checks that the molecule matches the label rather than only measuring how clean the sample is.

If you have not worked through one of these reports before, there is a walkthrough on [how to read a peptide COA](/research/how-to-read-a-peptide-coa), and a wider [checklist for sourcing research peptides in Canada](/research/buying-research-peptides-canada) covering what else to verify before ordering. Current stock and batch details for this compound live on the [Selank product page](/products/selank). Kits Peptides ships tracked from Vancouver, BC across Canada.

*All products are supplied as laboratory reagents for research use only. Not for human or veterinary use.*