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Selank Disposable Self-injection Pen is a pre-filled device holding the heptapeptide TKPRPGP, built from the immune tetrapeptide tuftsin plus a three-residue tail.
– CAS 129954-34-3 · MW approx. 751 g/mol · seven residues: Thr-Lys-Pro-Arg-Pro-Gly-Pro
– The first four residues are tuftsin, cut from the heavy chain of immunoglobulin G
– Pro-Gly-Pro on the end slows exopeptidase attack, which is the whole point of the modification
– Supplied in solution · keep cold and protected from light · purity per lot-specific COA
Research use only. Not for human or veterinary use, food, or household application.
Epic Peptides Lab · Research Use Only
TKPRPGP heptapeptide · tuftsin analogue · CAS 129954-34-3
Selank Disposable Self-injection Pen is a pre-filled device supplying the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro, CAS 129954-34-3, molecular formula C33H57N11O9, molecular weight 751.88. The sequence joins the tuftsin tetrapeptide to a three-residue proline-glycine-proline extension.
| Property | Value |
|---|---|
| Compound | Selank |
| CAS number | 129954-34-3 |
| Molecular formula | C33H57N11O9 |
| Molecular weight | 751.88 g/mol |
| Residue count | 7 |
| Single-letter sequence | TKPRPGP |
| Three-letter sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent tetrapeptide | Tuftsin, Thr-Lys-Pro-Arg, residues 289 to 292 of the immunoglobulin G heavy chain |
| Extension | Pro-Gly-Pro at the carboxy terminus |
| Purpose of the extension | Reported to increase resistance to enzymatic degradation |
| Proline content | Three of seven residues |
| Net charge at neutral pH | Positive, from lysine and arginine |
| Originating programme | Institute of Molecular Genetics, Russian Academy of Sciences |
| Oxidation-prone residues | None |
| Format | Pre-filled Disposable Self-injection Pen device |
| Physical state | Solution, supplied ready-filled |
| Appearance | Clear colourless solution |
| Purity | Per lot-specific certificate of analysis |
| Storage | 2-8°C, protected from light |
| Regulatory status | No approved human or veterinary formulation in the United States |
The first four residues supplied in a Selank Disposable Self-injection Pen are not an arbitrary sequence, and they correspond to a naturally occurring tetrapeptide with a well-documented origin.
Tuftsin is Thr-Lys-Pro-Arg, corresponding to residues 289 to 292 of the immunoglobulin G heavy chain. It is released from the Fc region by enzymatic cleavage, which makes it a fragment of an abundant circulating protein rather than a product of a dedicated peptide precursor.
It was named for Tufts University, where it was described in the 1970s, and the literature on it concerns interactions with cells of the immune system, particularly phagocytes.
A receptor for tuftsin has been proposed in the form of neuropilin-1, though the characterisation is less complete than for well-established peptide receptors and the interaction is a subject of ongoing work rather than a settled fact.
Selank therefore inherits a partially characterised pharmacology. The tetrapeptide is real and its origin is certain, while the receptor question remains more open than descriptions of the compound typically convey.
The three-residue extension at the carboxy terminus is the modification that turns tuftsin into Selank, and the rationale concerns stability.
Short peptides are degraded rapidly by exopeptidases working inward from the termini. A four-residue peptide offers very little to work with, and tuftsin is correspondingly short-lived in biological systems.
Proline is unusual among amino acids in that its side chain bonds back to the backbone nitrogen, forming a ring. That constrains the backbone conformation and, importantly, makes the preceding peptide bond a poor substrate for many proteases, which cannot accommodate the geometry.
Placing prolines at positions 5 and 7 therefore shields the carboxy-terminal region. The published rationale for the extension is increased resistance to enzymatic degradation, and the chemistry supports that reasoning independently of any specific measurement.
The same strategy appears in Semax, where a Pro-Gly-Pro extension is added to an ACTH fragment by the same research programme. Recognising the shared design across both compounds clarifies that this is a deliberate platform approach rather than a one-off modification.
Three prolines in seven residues is a high proportion and it determines the physical behaviour of the molecule.
Proline-rich sequences cannot form conventional alpha helices, because the ring structure denies the backbone the hydrogen bonding a helix requires and the nitrogen has no hydrogen to donate. Beta sheet is similarly disfavoured.
What such sequences can adopt is the polyproline II conformation, an extended left-handed helix with roughly three residues per turn. It is a genuine ordered structure, not simply disorder, and proline-rich regions in larger proteins frequently use it as a recognition surface.
The practical implication is that this peptide has little conformational entropy to lose on binding, which can favour association, and that it will not aggregate through the beta-sheet mechanism that troubles many peptides.
It also means the molecule is chemically durable in the ways that matter for storage. No cysteine, no methionine, no tryptophan, no asparagine-glycine motif. There is very little in this sequence for degradation chemistry to act on.
The Selank Disposable Self-injection Pen format suits a chemically durable short peptide better than it suits a folded protein, and Selank is at the favourable end of that spectrum.
With no oxidation-prone residues and no disulfides, the degradation routes that make solution-state storage risky for other compounds largely do not apply. The principal concerns are microbial contamination, which the sealed format addresses, and adsorptive loss.
Adsorption is worth noting. The peptide carries a net positive charge from lysine and arginine, and basic peptides adsorb to negatively charged surfaces. In a sealed device with a fixed container that loss occurs once and reaches equilibrium rather than accumulating, but it means the delivered concentration may sit slightly below the labelled one.
Freezing should be avoided as with all pre-filled devices, on mechanical grounds rather than peptide-stability grounds in this case.
Visual inspection remains worthwhile. A clear colourless solution is expected, and any cloudiness or particulate warrants rejecting the unit even though this peptide is not prone to aggregation.
Two compounds from the same Russian research programme use an identical structural strategy, and comparing them clarifies what the strategy is intended to achieve.
Semax takes an ACTH fragment, residues 4 to 7 in the sequence Met-Glu-His-Phe, and appends Pro-Gly-Pro at the carboxy terminus. The heptapeptide here takes tuftsin, Thr-Lys-Pro-Arg, and appends the same three residues in the same position.
Both parent tetrapeptides derive from larger endogenous proteins rather than from dedicated peptide precursors, one from a pituitary hormone and one from immunoglobulin G. Both are short enough to be degraded rapidly without protection.
The shared extension is therefore a platform element rather than a compound-specific design choice. The programme identified a short protective motif and applied it across candidates, which is a reasonable medicinal chemistry approach and one that leaves a recognisable signature.
That signature is useful diagnostically. A short peptide ending in Pro-Gly-Pro is likely to originate from this programme, and knowing the origin tells a reader where the supporting literature will be concentrated.
It also raises a testable question that appears not to have been systematically addressed: whether the extension contributes activity of its own rather than only protection, which a Pro-Gly-Pro-only arm would answer.
The tuftsin core comes from an antibody heavy chain, and that provenance carries implications that descriptions of the compound rarely draw out.
Immunoglobulin G is among the most abundant proteins in circulation. A tetrapeptide released from its Fc region is therefore potentially generated continuously wherever the appropriate proteolytic activity exists, rather than being produced on demand from a dedicated precursor.
That is a different regulatory logic from a conventional peptide hormone. A hormone is synthesised, stored and released in response to a signal. A fragment liberated from an abundant structural protein is generated as a function of proteolytic activity and substrate availability.
Whether the tetrapeptide constitutes a genuine signalling molecule or an incidental proteolysis product has been discussed in the literature since the 1970s, and the question is not fully settled.
For experimental design the implication is that background levels may be present in any system containing immunoglobulin and the relevant protease activity, including serum-preparationed culture medium.
Measuring or at least considering that background, rather than assuming a zero baseline, is the reasonable precaution and it is one that serum-free conditions largely resolve.
Where the peptide is this chemically forgiving and the format is sealed, the record shrinks to traceability.
Lot number, fill date, and the concentration stated on the certificate with the method used to determine it. Those three cover the material itself.
Storage temperature and any excursion, though the consequences of an excursion are milder here than for a folded protein or a coenzyme, because this sequence has very little available degradation chemistry.
Date of first use and date of each subsequent use, so that a Selank Disposable Self-injection Pen spanning several experiments can be matched against the series it supplied.
Visual condition at each use, briefly. Clear and colourless is expected and anything else warrants stopping.
A Selank Disposable Self-injection Pen wants refrigeration, darkness, no freezing and inspection before use, and the requirements are modest for this compound.
Maintain 2-8°C and return the device promptly after use. Selank tolerates handling better than most compounds in this catalogue, but there is no reason to test the margin.
Keep the device in original packaging until immediately before use, which handles light exposure and protects the mechanism.
Do not freeze. The reason here is the sealed liquid-filled mechanism rather than the peptide itself, which would tolerate freezing perfectly well in an ordinary tube.
Record lot, manufacture date, storage history and dates of use. Here the log serves traceability rather than stability, which is a comfortable place to be.
A closing note on sourcing. Because this compound and its relatives come from one research programme, the supporting literature is concentrated in Russian-language journals and in their English translations.
Translation quality varies, and terminology that is standard in one tradition is unfamiliar in another. Reading the original where possible, or at least checking a translated methods section against the abstract, catches discrepancies that would otherwise propagate.
It also explains why indexed citation counts for these compounds understate the volume of work behind them.
A last note on the sequence itself. Confirm it as Thr-Lys-Pro-Arg-Pro-Gly-Pro on the certificate rather than relying on the trade name, since several short peptides from the same programme share the terminal three residues and differ only in the core.
References verified against the publisher record. Note that much of the Selank literature originates from the Russian research programme that developed it.
What is the Selank Disposable Self-injection Pen?
A pre-filled device supplying the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro, CAS 129954-34-3, molecular weight 751.88. The sequence joins the tuftsin tetrapeptide to a proline-glycine-proline extension. For laboratory research purposes alone, never for human or veterinary use.
What is tuftsin?
A naturally occurring tetrapeptide, Thr-Lys-Pro-Arg, corresponding to residues 289 to 292 of the immunoglobulin G heavy chain. It is released from the Fc region by enzymatic cleavage, making it a fragment of an abundant circulating protein.
Where does the name come from?
Tufts University, where the tetrapeptide was described in the 1970s. The literature on it concerns interactions with cells of the immune system, particularly phagocytes, rather than the applications Selank is usually associated with.
Has a tuftsin receptor been identified?
Neuropilin-1 has been proposed, though the characterisation is less complete than for well-established peptide receptors. The interaction remains a subject of ongoing work rather than a settled fact, so Selank inherits a partially characterised pharmacology.
Why is Pro-Gly-Pro added?
For stability. Short peptides are degraded rapidly by exopeptidases working inward from the termini, and a four-residue peptide offers very little to work with. The extension shields the carboxy-terminal region against that degradation.
How does proline confer protease resistance?
Its side chain bonds back to the backbone nitrogen, forming a ring. That constrains backbone conformation and makes the preceding peptide bond a poor substrate for many proteases, which cannot accommodate that geometry.
Does the same strategy appear elsewhere?
Yes, in Semax, where a Pro-Gly-Pro extension is added to an ACTH fragment by the same research programme. Recognising the shared design clarifies that this is a deliberate platform approach rather than a one-off modification.
What structure does a proline-rich peptide adopt?
Polyproline II, an extended left-handed helix with roughly three residues per turn. It is a genuine ordered structure rather than disorder, and proline-rich regions in larger proteins frequently use it as a recognition surface.
Is Selank chemically durable?
It sits at the forgiving end of this catalogue. No cysteine, no methionine, no tryptophan and no asparagine-glycine motif, so the usual degradation routes are largely unavailable. There is very little in the sequence for degradation chemistry to act on.
Does adsorption affect the delivered concentration?
Possibly a little. The peptide carries a net positive charge from lysine and arginine, and basic peptides adsorb to negatively charged surfaces. In a sealed device that loss reaches equilibrium once rather than accumulating over time.
Selank is sold exclusively for laboratory research use. It is not a drug, food, or cosmetic product, and it is not a dietary product of any kind. It is not approved by the FDA or any comparable authority for human or veterinary use, and the pre-filled device format does not alter that status. This product is not intended to diagnose, treat, cure, or prevent any disease. It must not be given to humans or animals. Purchase is restricted to qualified researchers and institutions operating within applicable laws. All handling is the responsibility of the purchasing laboratory.
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