Testagen

1 Identity

Synthetic linear tetrapeptide, all-L, four proteinogenic residues, free alpha-amino N-terminus and free-acid C-terminus. No acetyl cap, no amide, no cysteine, no disulfide, no D-residue, no non-proteinogenic residue, no metal. Three carboxylic acid groups (Glu and Asp side chains plus the C-terminal glycine) against one lysine side-chain amine make it net acidic and strongly hygroscopic as a salt. Supplied as the trifluoroacetate or the acetate. cataloged within the Khavinson short peptide bioregulator family alongside Vilon (KE).

Sequence

H-Lys-Glu-Asp-Gly-OH; one-letter KEDG, four residues, all L. Free alpha-amine on Lys1; free acid on Gly4. The Asp3-Gly4 bond is the classic aspartimide-forming sequence in peptide chemistry and is the analytical center of gravity of this record: the Asn/Asp-Gly motif is the fastest-rearranging pair known in short peptides and the resulting iso-aspartyl product is exactly mass-silent. The sequence is supplier-reported and is stated as such: the originating institute's own publications and vendor catalogs give Lys-Glu-Asp-Gly, and the formula reconstructed from that sequence matches the mass the same vendors publish. It was not confirmed against a regulatory monograph, because none exists.

Molecular formula

C17H29N5O9 (free acid). Acetate salt C19H33N5O11; trifluoroacetate salt C19H30F3N5O11. No CAS number is printed for this article, because the formula rests on a supplier-reported sequence that no regulatory monograph confirms.

Average mass

447.445 Da (C17H29N5O9, free acid). Both figures are computed from the supplier-reported sequence. Mono-acetate gross 507.497; mono-TFA gross 561.468, at which the free acid is only 79.7 percent of the powder.

Monoisotopic mass

447.19653 Da free acid; [M+H]+ 448.20380; [M-H]- 446.18925. Mono-acetate 507.21766; mono-TFA 561.18939.

Salt / variant note

The whole family is the variant list, and they are stocked on one shelf under fifteen names. Vesugen H-Lys-Glu-Asp-OH C15H26N4O8 390.393 / 390.17506 is the des-Gly truncation, exactly 57.05 Da light and simultaneously the product of a failed final coupling and the easiest deliberate substitution. Livagen H-Lys-Glu-Asp-Ala-OH C18H31N5O9 461.472 / 461.21218 is 14.03 Da heavy — one CH2, Ala for Gly, invisible on a nominal-mass instrument. Pancragen H-Lys-Glu-Asp-Trp-OH C26H36N6O9 576.607 / 576.25438. Vilon H-Lys-Glu-OH C11H21N3O5 275.305 / 275.14812. Epitalon H-Ala-Glu-Asp-Gly-OH C14H22N4O9 390.349 / 390.13868, and note the trap this creates for the family method file: Vesugen at 390.393 and Epitalon at 390.349 differ by 0.044 Da average and 0.036 Da monoisotopic and are not separable at unit resolution. Bronchogen H-Ala-Glu-Asp-Leu-OH C18H30N4O9 446.457 / 446.20128 sits 0.99 Da from Testagen on average mass and is inside the isotope envelope of a low-resolution scan, which is the single most dangerous same-shelf collision on this record; mass tolerance on this molecule is therefore stated in ppm and never in daltons. Chonluten H-Glu-Asp-Gly-OH C11H17N3O8 319.270. On the article itself: the C-terminal amide H-KEDG-NH2 C17H30N6O8 446.461 / 446.21251 is 0.98 Da light; the N-acetylated form C19H31N5O10 489.482 / 489.20709 is 42.04 Da heavy. The variants that carry no mass difference at all: aspartimide-derived iso-aspartyl and D-iso-aspartyl products at the Asp3-Gly4 bond are exactly isobaric at 447.445 / 447.19653, and so is any permutation of the same four residues — amino acid analysis is composition-blind to order, so GDEK, DKEG and every other arrangement returns the identical formula and the identical mass. Only MS/MS or co-injection against an authentic standard separates them. The succinimide intermediate itself is 18.02 Da light at 429.430. And the sideways risk into the extract line: the Cytomax organ preparations are sold under adjacent names by the same vendors and have no molecular species at all.

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.

Animal and in-vitro evidence only, concentrated almost entirely in one institution, and for this individual peptide it is thinner still. The family literature runs to roughly 160 PubMed publications spanning 1993-2025, overwhelmingly authored or co-authored by V. Kh. Khavinson and affiliated with the Saint Petersburg Institute of Bioregulation and Gerontology with associated Russian institutions. Much of it is review rather than primary trial: Khavinson, Neuro Endocrinol Lett 2002, PMID 12374906; Khavinson et al., Stem Cell Rev Rep 2020, PMID 31808038, the source of the group's verbatim mechanism claim; Khavinson, Kuznik and Ryzhak, Adv Gerontol 2012, PMID 23734519 (experimental) and 2013, PMID 24003726 (clinical) — the latter being the principal source for human claims and being a review by the originating group, not a primary randomized trial. Primary experimental work retrieved includes Khavinson and Kvetnoii, Bull Exp Biol Med 2000, PMID 11276315, an irradiation study in rats. At least one internationally co-authored in-vitro study exists: Avolio 2022, PMID 35408963, DOI 10.3390/ijms23073607, in the human THP-1 monocytic cell line, co-authored between Italian universities and the Saint Petersburg institute — and it covers five preparations, of which Testagen is not one. The structural feature of the evidence base is stated plainly and is not an accusation about any study: an entire class, roughly 160 publications, three decades, one institution, no located independent replication by unaffiliated laboratories. Volume of publication is not weight of evidence. Absences specific to this molecule, as of 14 August 2026: no primary human data for Testagen individually were located; no independently conducted randomized trial of any family member published in an indexed international journal was located; no independent toxicology was retrieved. The mechanistic proposition on which the family is marketed — sequence-specific nuclear DNA binding by a two-to-four-residue peptide — is a strong claim that has not entered mainstream molecular biology, and the citation index states that in the same typeface as the citations.

4 Storage & specification

Storage

Lyophilized white powder in the sealed original vial, supplied as the trifluoroacetate or the acetate with the form stated on the label and on the certificate. Labeled storage -20 degrees C plus or minus 5 degrees C, desiccated, protected from light. Strongly hygroscopic — three carboxylic acids and a lysine amine on a 447 Da molecule — so the SOP requires the container to be equilibrated to room temperature inside the desiccator before opening; condensation on a hygroscopic short peptide is the commonest way a good lot is ruined after release. Reconstituted solutions are held at 2-8 degrees C, buffered rather than left in unbuffered water, and treated as single-use: the Asp3-Gly4 aspartimide route is pH- and temperature-driven, and an aqueous stock left at room temperature is the practical way to generate the one degradant that no mass measurement will find. A tetrapeptide with free N- and C-termini is also rapidly degraded by amino- and carboxypeptidases in any biological matrix, which is a substantive experimental consideration for anyone designing a cell assay. Shipped on gel packs with a data logger in every shipper; excursion limits set by the shipping validation, not by the courier.

Shelf life

Provisional retest interval 24 months at -20 degrees C plus or minus 5 degrees C in the sealed original container, stated as provisional pending this company's own stability data. The confirming study is long-term at -20 degrees C with pulls at 0, 3, 6, 9, 12, 18 and 24 months, accelerated at 5 plus or minus 3 degrees C and at 25 degrees C / 60 percent relative humidity, assayed by a stability-indicating RP-HPLC gradient validated to resolve the iso-aspartyl degradant and the succinimide intermediate. Total iso-aspartyl is the named trended attribute, because on an Asp-Gly sequence it is the governing failure route and it is invisible to every other test on the panel; water content is trended alongside it, since the salt is hygroscopic and water uptake is what drives the rearrangement. The label carries a retest date, not an expiry date, and the interval is shortened without notice if a pull fails. Material reaching retest is re-assayed for purity, water, counterion stoichiometry and net peptide content and is either re-dated for a further 12 months or destroyed and recorded on the public failed-lot ledger. No compound-specific published stability data were retrieved for this molecule; every statement here is this company's protocol, not a literature finding.