P021 / P21 (adamantane-modified; CAS 1246751-68-7)

1 Identity

Neuroactive regulatory peptidomimetic. A four-residue N-acetylated peptide whose C-terminus is formed as the amide of a carbamoyl-substituted aminoadamantane. It is a peptide-small-molecule conjugate, not a peptide: the adamantane cage is a non-proteinogenic structural element and carries no amide backbone. Developed from a short region of ciliary neurotrophic factor by way of the eleven-residue literature peptide known as Peptide 6; it is not an analogue of the cytokine, which is roughly fifty times its size. because that designation collides with the unrelated human protein p21-Cip1/Waf1 (CDKN1A). CAS 1246751-68-7. "P21" is carried as an alias only and is never used as an identity statement.

Sequence

Ac-Asp-Gly-Gly-Leu-NH-(3-carbamoyladamantan-1-yl). The N-acetylated tetrapeptide Ac-L-Asp-Gly-Gly-L-Leu with its C-terminus formed as the amide of 3-carbamoyl-1-aminoadamantane - not plain 1-aminoadamantane, and the difference is 43.03 Da. Four proteinogenic L-residues (two of them glycine, which is achiral) plus one non-proteinogenic structural element, the carbamoyl-substituted adamantyl cap, which is the defining feature of the molecule and the element most often absent from material sold under the short name. A description of this article that omits the C-terminal adamantylamide would allow a structurally different, lighter product to be received and sold as this one, and the cytokine the molecule derives from is an approximately 200-residue, 22.7 kDa protein, so no analogy of size can be read into the name. Full IUPAC name as indexed against the CAS structure: (3S)-3-acetamido-4-[[2-[[2-[[(2S)-1-[[(5S,7R)-3-carbamoyl-1-adamantyl]amino]-4-methyl-1-oxopentan-2-yl]amino]-2-oxoethyl]amino]-2-oxoethyl]amino]-4-oxobutanoic acid; InChIKey LUJZBZPLIRWWGJ-NBONATBJSA-N. Two stereo-relevant features drive the panel: the L-Asp and L-Leu centers, and the Asp-Gly motif, which is the single most aspartimide- and racemization-prone arrangement in Fmoc solid-phase peptide chemistry. Both are the reason a chiral method and an iso-aspartate method are mandatory on this specification rather than optional additions to a default peptide panel.

Molecular formula

C27H42N6O8 (the registered structure). Confusables carried separately and never as impurities of this article: plain-adamantyl analogue C26H41N5O7; uncapped N-acetylated tetrapeptide free acid C16H26N4O8; uncapped C-terminal amide C16H27N5O7; des-acetyl P021 C25H40N6O7; capping-reagent residuals 1-aminoadamantane C10H17N and 3-amino-1-adamantanecarboxamide C11H18N2O. Two formulas in live commercial circulation that are documentation errors and match no structure of this compound: C30H54N6O5 and C24H40N8O10.

Average mass

578.67 Da (C27H42N6O8) on IUPAC 2021 abridged conventional atomic weights, 578.667 unrounded. A circulating catalog table prints 578.658, rounded elsewhere to 578.66, and one seller prints 578.7; 578.658 is the same formula evaluated on the older CODATA/IUPAC weights and is not an error, but 578.67 is what IUPAC 2021 gives and is the figure this catalog carries for consistency with every other record. A figure of 535.6 Da also circulates under this name: it is computed from an assumed plain-adamantyl cap, it is light by 43.03 Da, and it belongs to a different compound. Confusables: plain-adamantyl C26H41N5O7 535.64; uncapped free acid C16H26N4O8 402.40; uncapped amide C16H27N5O7 401.42; des-acetyl C25H40N6O7 536.63; 1-aminoadamantane 151.25; 3-amino-1-adamantanecarboxamide 194.28. The circulating error formula C30H54N6O5 computes to 578.80, which is within 0.14 Da of the correct average and is therefore invisible to any certificate that rounds - and it is also, exactly, the formula of palmitoyl tripeptide-1, a different article in this same catalog. That collision is a named red flag on both records.

Monoisotopic mass

578.30641 Da neutral (C27H42N6O8); [M+H]+ 579.31369; [M+2H]2+ m/z 290.16048; [M-H]- 578.29913. Identity window on [M+H]+ at plus or minus 5 ppm is plus or minus 0.0029 Da. Confusables at monoisotopic resolution: plain-adamantyl 535.30060 neutral, [M+H]+ 536.30787 (-43.006 Da); des-acetyl 536.29583 neutral, [M+H]+ 537.30311 - note that 536.3 is genuinely ambiguous between the des-acetyl correct-cap compound and the acetylated wrong-cap compound, and only 0.005 Da separates their [M+H]+ ions, so a nominal "536" identifies neither. Uncapped free acid 402.17506, [M+H]+ 403.18234; uncapped amide 401.19105, [M+H]+ 402.19833, which sits 0.98 Da below the free acid, so 402 and 403 on a nominal certificate are two different wrong products. The circulating error formula C30H54N6O5 is 578.41563 monoisotopic, 0.109 Da (189 ppm) from this article - resolvable at 30,000 resolving power and invisible below it.

Salt / variant note

The adamantyl cap and its carbamoyl group are the two elements most often missing from material bought under the short name, and each absence is arithmetic. (1) plain-adamantyl compound Ac-Asp-Gly-Gly-Leu-NH-(1-adamantyl), C26H41N5O7, 535.64 average / 535.30060 monoisotopic, [M+H]+ 536.30787 - 43.03 Da light, missing the CONH2 on the cage. It is a different article from the registered structure. (2) uncapped N-acetylated tetrapeptide free acid Ac-Asp-Gly-Gly-Leu-OH, C16H26N4O8, 402.40 / 402.17506, [M+H]+ 403.18234 - 176.26 Da light. A different product, not an impurity of this one. (3) uncapped C-terminal amide Ac-Asp-Gly-Gly-Leu-NH2, C16H27N5O7, 401.42 / 401.19105, [M+H]+ 402.19833 - sits 0.98 Da below the free acid, so 402 and 403 on a nominal certificate are two different wrong products. (4) des-acetyl P021 H-Asp-Gly-Gly-Leu-NH-(3-carbamoyladamantyl), C25H40N6O7, 536.63 / 536.29583 - 42.01 Da light and colliding with variant (1) at nominal 536. (5) capping-reagent residuals that give the diagnostic aliphatic cage signature in NMR with no peptide attached: 1-aminoadamantane C10H17N, 151.25 / 151.13614; 3-amino-1-adamantanecarboxamide C11H18N2O, 194.28 / 194.14191. (6) iso-aspartate and aspartimide: the beta-aspartyl rearrangement product at the Asp-Gly motif is isobaric with the parent - same formula, same 578.30641, normal-looking chromatogram - and the succinimide intermediate sits at minus 18.011 Da; neither is a mass problem, both are method problems. (7) published-formula errors in live circulation: one seller's monograph prints "C30H54N6O5" with "578.3 g/mol" on the same page, and C30H54N6O5 computes to 578.80 average / 578.41563 monoisotopic, so the formula does not match its own stated weight; C30H54N6O5 is also exactly the formula of palmitoyl tripeptide-1, a separate article in this catalog at 578.80 average and only 0.109 Da away monoisotopically. A second circulating monograph prints C24H40N8O10 / 600.62. Neither is the CAS structure.

2 Class & testing panel

Form

Single article

Testing panel

P3 — panel definition

3 Primary sources & evidence

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

Published literature exists, is entirely preclinical, and is graded D. By study type and identifier: rodent work in the 3xTg-AD triple transgenic mouse over a twelve-month chronic oral course (Kazim et al., Neurobiol Dis 2014;71:110-30, PMID 25046994 - animal, mouse); the Ts65Dn mouse model with prenatal-to-early-postnatal dosing (Kazim et al., Sci Rep 2017, PMID 28368015 - animal, mouse); two further 3xTg-AD mouse studies (Wei et al., Alzheimers Res Ther 2020, PMID 32854771; Wei et al., J Alzheimers Dis 2021, PMID 34057082 - animal, mouse); a diffusion-MRI imaging-biomarker study in the same model (Falangola et al., Magn Reson Imaging 2026, PMID 41740658 - animal, mouse); and one in-vitro and in-vivo study in models of CDKL5 deficiency disorder from a laboratory other than the originating group (Mottolese et al., J Neurodev Disord 2024, PMID 39592934 - in vitro and animal). That last item is the only replication outside the originating laboratory identified in the retrieved literature. There is also an earlier literature on the eleven-residue parent peptide from the same group; this record keeps the parent-peptide and derivative literatures separate and does not allow a citation for one to be read as support for the other. Human literature: none identified. No registered human study, no first-in-human pharmacokinetic or tolerability publication and no published human exposure was identified, which is a no-trial-identified finding rather than a certified absence. No published acute, repeat-dose, genotoxicity, reproductive or carcinogenicity toxicology program was identified.

4 Storage & specification

Storage

White to off-white lyophilized powder in the sealed original container with desiccant, stored at -20 degrees C plus or minus 5 degrees C, protected from light, equilibrated to room temperature in the sealed container before opening, shipped frozen in a validated shipper with a temperature logger whose record is filed against the shipment. Desiccation is a control here rather than a formality: aspartimide formation and its hydrolysis to iso-aspartate are moisture- and pH-accelerated, and this molecule's Asp-Gly motif is the most susceptible arrangement in peptide chemistry. The adamantyl cap makes the material markedly more lipophilic than most articles in this catalog, so the handling page names the solvent system used for the assay and says nothing about administration, route or vehicle.

Shelf life

Provisional 24-month retest interval at -20 degrees C plus or minus 5 degrees C, desiccated and light-protected, dated on iso-aspartate and aspartimide content rather than on total assay - a rearranged lot has the same mass, the same molecular formula and, on an unresolved method, the same chromatogram as a good one, so assay is the wrong dating attribute for this molecule. Provisional pending the company's own data: three lots on real-time storage at -20 degrees C with pull points at 0, 3, 6, 12, 18, 24 and 36 months, accelerated arms at 25 degrees C / 60 percent RH and 40 degrees C / 75 percent RH, and an open-dish moisture-challenge arm, with iso-aspartate reported at every pull.