N-Acetyl Selank

1 Identity

Synthetic heptapeptide, N-terminally acetylated. Linear, all-L, all proteinogenic; no cysteine, no disulfide, no methionine, no tryptophan, no lipid, no PEG, no metal, no acylation beyond the terminal acetyl. Ac-TKPRPGP-OH (free acid) and Ac-TKPRPGP-NH2 (amide, marketed as 'N-Acetyl Selank Amidate' and as 'Adalank'). Parent is Selank / TP-7, H-Thr-Lys-Pro-Arg-Pro-Gly-Pro-OH, PubChem CID 11765600. Not a synonym for Selank, not a synonym for tuftsin (the Thr-Lys-Pro-Arg tetrapeptide inside it).

Sequence

Ac-Thr-Lys-Pro-Arg-Pro-Gly-Pro-OH (Ac-TKPRPGP-OH) as the catalog default, with the C-terminal amide Ac-TKPRPGP-NH2 as the form the direct-to-consumer channel actually ships under the adjacent name 'N-Acetyl Selank Amidate'. Seven proteinogenic L-residues; the parent is the tuftsin tetrapeptide Thr-Lys-Pro-Arg extended at the C-terminus by Pro-Gly-Pro. The N-terminal alpha-amine is capped; the Lys2 epsilon-amine and the Arg4 guanidine remain free and basic, which is why the solid is hygroscopic and why the counterion loading is material to gravimetric assay. Three prolines make cis/trans conformer broadening a chromatographic fact of life on this molecule and a method-development problem rather than an impurity.

Molecular formula

C35H59N11O10 (C-terminal free acid, free base, salt-free) as the catalog default. C35H60N12O9 (C-terminal amide, free base) for the amidated article sold under the adjacent name. Parent Selank C33H57N11O9.

Average mass

793.924 Da for the free acid (C35H59N11O10) and 792.940 Da for the amide (C35H60N12O9), both from the formulas on IUPAC 2021 abridged conventional atomic weights. Listings commonly print 793.91 and 792.93; those are the same formulas computed on the pre-2021 table (793.911 and 792.926) and are not errors. The distinction is worth stating precisely, because a monograph figure of 792.94 circulates for the amide: on the 2021 table the agreement with that figure is exact, and the 0.01 Da gap that is sometimes reported is an artifact of mixing atomic-weight tables. Parent Selank 751.887 (2021 table); 751.879 on the pre-2021 table.

Monoisotopic mass

793.4446 Da neutral monoisotopic for the free acid; [M+H]+ 794.4519. 792.4606 Da neutral monoisotopic for the amide; [M+H]+ 793.4679. Parent Selank 751.4341; [M+H]+ 752.4414. The separation between the two forms of this article is exactly 0.9840 Da, which no unit-resolution instrument can see, and the acetyl increment over the parent is exactly 42.0106.

Salt / variant note

Six distinct molecules move through this name and the adjacent trade names, and each is separated by arithmetic. (1) Ac-TKPRPGP-NH2, C35H60N12O9, avg 792.940 / mono 792.4606, [M+H]+ 793.4679 - the amide, and what the storefronts labeled 'N-Acetyl Selank Amidate' actually list. (2) Ac-TKPRPGP-OH, C35H59N11O10, avg 793.924 / mono 793.4446, [M+H]+ 794.4519 - the free acid, 0.9840 Da away, invisible on any nominal-mass instrument. (3) Plain Selank, H-TKPRPGP-OH, C33H57N11O9, avg 751.887 / mono 751.4341, [M+H]+ 752.4414 - 41.03 Da lighter than the amide and the cheapest substitution in the family. (4) Selank amide, des-acetyl, H-TKPRPGP-NH2, C33H58N12O8, avg 750.903 / mono 750.4501, [M+H]+ 751.4573. Note the collision that this creates: its [M+H]+ 751.4573 sits 0.023 Da from plain Selank's neutral monoisotopic 751.4341, so a bare '751' on a certificate identifies nothing at all. (5) Tuftsin, Thr-Lys-Pro-Arg, C21H40N8O6, avg 500.601 / mono 500.3071, [M+H]+ 501.3144 - the four-residue fragment, sold separately and far cheaper. (6) Cross-family substitution from the Semax bench next to it: Semax C37H51N9O10S avg 813.928 / mono 813.3480, and N-acetyl Semax amidate C39H54N10O10S avg 854.981 / mono 854.3745. Salt form is a seventh axis and is not an impurity: acetate or trifluoroacetate at typical loading shifts gravimetric weight without shifting the free-base mass, so a certificate reporting mass but neither counterion content nor net peptide content has not closed the mass balance. AdaSelank, the adamantane conjugate, is a separate record and its attachment site is genuinely unresolved; it is not a variant of this article and must not be released against this specification.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definition

3 Primary sources & evidence

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

Published literature exists, and it is thinner for this article than for its parent. Parent compound: a predominantly Russian-language base of rodent behavioral and neurochemical studies together with a small number of clinical reports, most originating from or associated with the institute that developed the compound; independent replication outside that group is sparse, and no adequate and well-controlled trial to United States registrational standards was identified. For the N-acetylated derivative specifically the published record is substantially thinner - on the order of a handful of synthetic-chemistry, stability and animal pharmacokinetic reports, with no controlled human trial identified. No FDA-approved product, no United States IND-stage program and no ClinicalTrials.gov registration identified for the derivative as of 11 August 2026. The product's evidence page lists the primary sources with DOIs or PMIDs and tags each by study type; it does not summarize conclusions and it does not extrapolate from the parent to the derivative, because a terminal modification makes a different molecule.

4 Storage & specification

Storage

White to off-white lyophilized powder, acetate or trifluoroacetate salt as declared, in Type I amber glass under nitrogen, stoppered and crimped. Store at -20 degrees C plus or minus 5 degrees C in the sealed original container with desiccant, protected from light. The solid is hygroscopic - the lysine and arginine side chains and the counterion all draw water - so containers are equilibrated to room temperature before opening to prevent condensation onto the cake, and the label carries a close-immediately-after-weighing instruction. Karl Fischer is run at release and at every retest point. Ship on dry ice or with a validated frozen shipper, single-use temperature logger in every export carton, and the excursion record travels with the lot. No reconstituted-material stability data are held and none is implied: the label states that the product is not to be stored in solution.

Shelf life

Provisional 24-month retest interval at -20 degrees C plus or minus 5 degrees C, protected from light and moisture. Provisional is meant literally - the interval is an engineering assumption carried until this company's own stability protocol produces data. That protocol places three lots on real-time storage at -20 degrees C with pull points at 0, 3, 6, 12, 18, 24 and 36 months, plus accelerated arms at 25 degrees C / 60 percent RH and 40 degrees C / 75 percent RH, and the interval is reset to whatever the data support. There is no assay-based reason to expect rapid chemical loss: the sequence carries no cysteine, no methionine and no tryptophan, so the interval is expected to be governed by water uptake and by counterion-driven physical change rather than by oxidation. Printed retest date on every vial, first-expiry-first-out enforced against it.