Thymogen

1 Identity

Base synthetic dipeptide. Two proteinogenic L-residues, free alpha-amino N-terminus, free C-terminal acid, no acylation, no amidation, no cyclization, no cysteine, no disulfide, no metal, no non-proteinogenic residue. The identity nonetheless turns on two attributes no mass measurement can see: the glutamyl linkage must be alpha and not gamma, and both residues must be L. Supplied as the free acid or as the registered mono-sodium salt. Chemically it is alpha-L-glutamyl-L-tryptophan, and the abbreviations "Glu-Trp" and "EW" circulate as if they were identities when each names at least four molecules. The alias that matters most is a near-homograph inside this catalog: Thymagen, a separate record here, is entered under the same declared sequence Glu-Trp.

Sequence

H-L-alpha-Glu-L-Trp-OH. Two residues: L-glutamic acid joined to L-tryptophan through the glutamate alpha-carboxyl, not the gamma. Free alpha-amino N-terminus, no N-acetyl; free C-terminal acid, no amide. No cysteine, no disulfide, no non-proteinogenic residue, no D-residue. Two facts fix this identity and neither of them is a mass: the glutamyl linkage must be alpha, and both residues must be L. The single tryptophan is the oxidation- and light-labile point of the molecule, and the N-terminal glutamate can cyclize to pyroglutamate; those two degradation routes are what the specification and the storage condition are built around.

Molecular formula

C16H19N3O5 (free acid); C16H18N3NaO5 (mono-sodium salt, the form registered in the Russian Federation). The formula is identical for the alpha and gamma linkages and for every stereoisomer, which is precisely why it is not an identity statement on its own.

Average mass

333.344 Da (C16H19N3O5, free acid), on IUPAC 2021 abridged conventional atomic weights (C 12.011, H 1.008, N 14.007, O 15.999). Mono-sodium salt C16H18N3NaO5, 355.326 Da; the free acid is 93.8 percent of the salt by mass, which is the correction a labeled-milligram figure needs. The older atomic-weight table gives 333.34 for the same formula, and the two agree within rounding; the basis is stated on the face of the number because this catalog standardizes on the 2021 table.

Monoisotopic mass

333.13247 Da neutral (C16H19N3O5); [M+H]+ 334.13975; [M-H]- 332.12519. Mono-sodium salt 355.11441. A plus or minus 5 ppm window on [M+H]+ is plus or minus 0.0017 Da. That window is trivially met and excludes almost nothing here, because the molecules that matter share the formula exactly; the only mass-resolvable neighbors are degradation products and salt forms, not the isomers.

Salt / variant note

This is the purest example of the substitution problem in the catalog, because the leading confusable is not close to the target, it is identical to it, and it is on sale. Exactly isobaric, different molecule: gamma-D-Glu-L-Trp, developed as SCV-07 and sold as golotimod, CAS 229305-39-9, C16H19N3O5, 333.344 / 333.13247, stocked at institutional scale in six pack sizes from 2 mg to 100 mg. It differs from this article in exactly two ways a mass spectrometer cannot see at any resolving power: the linkage is gamma rather than alpha and the glutamate is D rather than L. Three more sit on the same number: gamma-L-Glu-L-Trp, the regiochemical impurity from coupling through the side-chain carboxyl; alpha-L-Glu-D-Trp and alpha-D-Glu-L-Trp, the chiral impurities; and Trp-Glu, the reversed dipeptide, likewise exact. At least five distinct molecules share 333.13247, which is why accurate mass is worth almost nothing as identity evidence here. Mass-resolvable forms, each an arithmetic check a buyer can run without a standard: mono-sodium salt C16H18N3NaO5 355.326 / 355.11441, the registered article; a 1:1 trifluoroacetate-paired form C18H20F3N3O7 447.367 / 447.12533, of which the free acid is only 74.5 percent by mass; pyroGlu-Trp C16H17N3O4 315.329 / 315.12191, exactly 18.011 Da light, the N-terminal cyclization product; oxidized tryptophan at plus 15.995 (C16H19N3O6, 349.343 / 349.12739) and plus 31.990 (C16H19N3O7, 365.342 / 365.12230); the kynurenine-type oxidation product at plus 3.995 (C15H19N3O6, 337.332 / 337.12739), a shift small enough to be dismissed as calibration noise on a poorly tuned instrument; N-acetyl-Glu-Trp C18H21N3O6 375.381 / 375.14304 if the terminus was capped. Unreacted starting materials: free L-Trp 204.229 / 204.08988 and free L-Glu 147.130 / 147.05316, and tryptophan is UV-bright at 280 nm, so residual free Trp inflates a purity figure read at the wrong wavelength. Cartalax, Ala-Glu-Asp, C12H19N3O8, is 333.297 average and 333.11721 monoisotopic, another peptide of the same program sold by the same vendors in the same product block, 46 ppm away monoisotopic and identical to 333.3 on the average, so a rounded certificate distinguishes neither. Name-adjacent traps: Thymagen, the same declared dipeptide under a second trade name and a separate record here; Thymalin, the undefined thymus extract with no mass at all; thymosin alpha-1, an acetylated 28-mer at 3108.315 / 3106.50413. Three articles, three orders of magnitude apart, sold under names one syllable apart.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definitionwith mandatory regiochemical and P3 chiral additions

3 Primary sources & evidence

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

Literature exists and is recorded by study type without any statement of effect. The index places this molecule inside the Khavinson short-peptide program and grades that program D: animal and in-vitro work plus non-independent, largely Russian-language reviews from the originating institution, with no independently replicated randomized human trial located. Named items: Khavinson VKh, Neuro Endocrinol Lett 2002, PMID 12374906, review; Khavinson V, Linkova N, Diatlova A, Trofimova S, Stem Cell Rev Rep 2020, PMID 31808038, review and the source of the program's verbatim structural claim; Khavinson VK, Kvetnoii IM, Bull Exp Biol Med 2000, PMID 11276315, rat study; Khavinson VKh, Kuznik BI, Ryzhak GA, Adv Gerontol 2012, PMID 23734519 and Adv Gerontol 2013, PMID 24003726, both reviews rather than primary randomized trials; Mironova ES et al., Adv Gerontol 2020, PMID 32593244, review. The index also records the field's objection to the program's central structural claim, that a dipeptide has too few contacts to specify a unique genomic site. A separate literature exists for the isobar golotimod / SCV-07 under its own identifiers. That literature belongs to a different molecule, and none of it is carried on this record. Crucially, no located publication states the glutamyl linkage and the configuration of the material studied, so no citation can be tied to a lot released against this specification.

4 Storage & specification

Storage

Lyophilized white to off-white solid in the sealed original vial, under foil overwrap or in amber glass. Labeled storage -20 degrees C plus or minus 5 degrees C, desiccated, protected from light. This is the most light-sensitive material in this part of the catalog: the single tryptophan is the photolysis- and oxidation-labile point of the molecule. Sampling is performed under yellow light and the sampling record captures cumulative light exposure, so that an out-of-specification oxidation result can be traced to handling rather than argued about. Vials are equilibrated to room temperature before the seal is broken so that moisture does not condense onto a hygroscopic cake.

Shelf life

Provisional retest interval 24 months at -20 degrees C plus or minus 5 degrees C in the sealed original container, protected from light, stated as provisional pending the company's own stability data. Because tryptophan oxidation and N-terminal pyroglutamate formation are the two named degradation routes, the confirming study runs an ICH Q1B photostability arm alongside the long-term and accelerated arms, and the stability-indicating method must resolve pyroGlu-Trp at minus 18.011 Da and the plus 15.995 Da oxidation product from parent. An area-percent purity figure alone does not date this molecule.