AdaSelank

1 Identity

Nominally a synthetic adamantane-conjugated heptapeptide; in practice a name without an established chemical identity. Vendor naming is inconsistent across this heading and is not authority for structure.

Sequence

No defined sequence, and the absence is the finding rather than a gap. The parent is established: Selank is H-Thr-Lys-Pro-Arg-Pro-Gly-Pro-OH (TKPRPGP), C33H57N11O9, 751.89 average / 751.4341 monoisotopic, confirmed against PubChem CID 11765600 - the tuftsin tetrapeptide Thr-Lys-Pro-Arg extended by Pro-Gly-Pro. The conjugate has no established sequence. No public monograph, no CAS registry entry and no PubChem record exists for an adamantane-conjugated Selank, and not one seller located states an attachment site, a linkage chemistry, a linker length or a C-terminal state. Two nucleophiles are available on the parent - the N-terminal alpha-amine and the Lys2 epsilon-amine - and they give isobaric products, so even a correct mass would not identify which molecule is in the vial. Nothing is asserted here beyond the parent.

Molecular formula

Not established. C44H71N11O10 is a conditional candidate only - it is exact for Selank plus one adamantane-1-carbonyl group - and it was derived from an assumed structure that no source corroborates. It is a formula to test a lot against, not a formula to print.

Average mass

No average mass is established for this article; confirm against a reference standard before listing, and no reference standard exists. The 914.1 Da figure is carried against a conditional formula only: it is 914.119 for C44H71N11O10, which is arithmetically exact for that formula, but the formula came from an assumption and not from a measurement or a declaration. Printing 914.1 as a specification would repeat, on a second molecule, precisely the error this catalog exists to catch.

Monoisotopic mass

Not established. 913.5385 Da is the monoisotopic value of the candidate formula C44H71N11O10 and is recorded as a candidate to test against, with the same caveat: it is identical for both positional isomers, so it cannot on its own identify the article even if the formula turns out to be right.

Salt / variant note

The Adamax failure mode, repeated, and the dominant commercial article again contains no adamantane. (1) What is actually sold: the market name is Adalank, and two independent listings state it as Ac-Thr-Lys-Pro-Arg-Pro-Gly-Pro-NH2 - N-acetyl Selank amidate, C35H60N12O9, 792.94 average / 792.4606 monoisotopic, CAS 2920938-92-5, an article with its own registry number sold independently on the same shelves by five separate sellers. No adamantane cage anywhere in the molecule. (2) Conditional candidates for an actual adamantane conjugate, each formula-derived and none corroborated: mono-adamantoyl Selank free acid, C44H71N11O10, 914.12 / 913.5385, identical for both positional isomers; and, if the conjugate follows the pattern the contract laboratory established for Adamax - parent plus one glycine plus a C-terminal amide - Ada-CO-TKPRPGP-Gly-NH2, C46H75N13O10, 970.19 / 969.5760. (3) The parallel non-adamantyl extension, matching the Adamax 984.10 article residue for residue: Ac-TKPRPGP-Ala-Gly-OH, C40H67N13O12, 922.06 / 921.5032. (4) The one-dalton pair any nominal-mass certificate will confuse: N-acetyl Selank free acid, C35H59N11O10, 793.92 / 793.4446, sitting 0.98 Da from the amidate at 792.94. (5) Cheaper substitutions behind a name nobody checks: unconjugated Selank at 751.89 / 751.4341; Selank amide, C33H58N12O8, 750.90 / 750.4501; and the tuftsin tetrapeptide TKPR, C21H40N8O6, 500.60 / 500.3071 - a four-residue synthesis sold as a seven-residue conjugate. (6) Over-conjugation: the bis-adamantoyl species with a cage on both amines, C55H85N11O11, 1076.35 / 1075.6430. (7) the isomer no mass resolves: N-alpha-adamantoyl-Selank and N-epsilon(Lys2)-adamantoyl-Selank are both 914.12 average and 913.5385 monoisotopic. They satisfy any accurate-mass criterion at any resolution, and they are different molecules with different solid-state behavior, because blocking the alpha-amine suppresses the diketopiperazine route at the N-terminal Thr-Lys-Pro motif and leaving it free does not.

2 Class & testing panel

Form

Single article

Testing panel

P2 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

No indexed primary publication was identified under this name at all - no synthesis paper, no characterization, no animal study, no controlled human trial. The parent heptapeptide Selank has a mainly Russian-language rodent and in-vitro literature and a Russian regulatory approval, and neither transfers to a covalently modified analogue that no one has characterized. The citation index page for this record is therefore short, says so, and labels every reference as parent-compound literature with the structural difference stated at the top of the page.

4 Storage & specification

Storage

Lyophilized solid in a Type I amber glass vial under nitrogen, stoppered and crimped. Labeled: store at -20 degrees C plus or minus 5 degrees C, protect from light and moisture, equilibrate the sealed vial to room temperature before opening. The article is hygroscopic - a lysine- and arginine-bearing peptide salt takes up water quickly in open air - so Karl Fischer runs at release and at every retest point and the label carries a close-immediately-after-weighing instruction. Ships ambient with a labeled cumulative excursion allowance of 120 hours at or below 30 degrees C; gel packs at 2-8 degrees C beyond that; single-use temperature logger in every export carton.

Shelf life

Shelf life is provisional at 18 months at -20 degrees C plus or minus 5 degrees C from the date of QA release, pending the company's own stability data. It is longer than the methionine-containing conjugate because the oxidation-labile residue is absent. Extension to 36 months only on real-time data at 18, 24 and 36 months with the diketopiperazine-related cleavage product, total related substances and water as the stability-indicating attributes. Printed retest date on every vial and first-expiry-first-out enforced against it.