Tripeptide-29

1 Identity

Cosmetic ingredient sold as a topical bulk raw material and as a laboratory chemical, marketed as a collagen-repeat tripeptide. If the commercial identification is correct, it is a small, highly polar, water-soluble tripeptide with a free alpha-amino N-terminus and a free C-terminal acid, containing one non-proteinogenic residue, 4-hydroxyproline, and no cysteine, no disulfide, no metal and no chromophore stronger than the amide bond. If the identification is not correct, the class statement falls with it. Glycyl-L-prolyl-L-hydroxyproline (Gly-Pro-Hyp) and sold under descriptions such as "collagen tripeptide" and "collagen booster peptide"; Tripeptide-29 is itself an INCI name. The identity behind that INCI number could not be independently confirmed. No CAS number was verified and none is printed. Not synonyms, and each is a separate molecule with its own mass: Tripeptide-1 (GHK), Tripeptide-5 (the core of Syn-Coll), Tripeptide-10 citrulline, and glycine-proline-glutamate (GPE), which differs from the claimed structure by a single oxygen atom. An INCI number is a naming convention administered for labeling purposes and not a statement of structure.

Sequence

Declared, not confirmed: H-Gly-L-Pro-trans-4-hydroxy-L-Pro-OH (Gly-Pro-Hyp). Vendor and cosmetic-supplier literature states this sequence; it stands as a commercial assertion, and no peer-reviewed primary source, regulatory monograph or Cosmetic Ingredient Review assessment tying the INCI name to that sequence was located. The declaration is also incomplete even if true, because hydroxyproline is not one residue but a family: trans-4-hydroxy-L-proline (2S,4R) is the collagen residue, and cis-4-hydroxy-L-proline (2S,4S), 4-hydroxy-D-proline and 3-hydroxyproline all share the formula C5H9NO3 and are mass-identical at every decimal place. A specification that says only "Hyp" has not fixed the molecule.

Molecular formula

CONDITIONAL. IF the article is Gly-Pro-Hyp, C12H19N3O5. The conditional is not decoration: the formula is arithmetic applied to a commercial assertion, and no independent source tying the INCI number to that structure was located. If the article is Gly-Pro-Pro, the formula is C12H19N3O4; if it is glycine-proline-glutamate, C12H19N3O6. Three plausible readings of a marketed "collagen tripeptide", three formulas, one of which differs from another by a single oxygen.

Average mass

IF the article is Gly-Pro-Hyp: 285.300 Da (C12H19N3O5), computed on IUPAC 2021 abridged conventional atomic weights. Roughly 285.3 is flagged as unverified for the same reason given here. The arithmetic is exact and reproducible; the premise is a supplier's word. For an ingredient sold as a bulk raw material, the fact that its basic chemical identity rests on supplier assertion is itself the material finding, and printing 285.300 without the conditional attached would convert an assertion into an apparent measurement.

Monoisotopic mass

CONDITIONAL on the same premise. IF Gly-Pro-Hyp: 285.13247 Da neutral (C12H19N3O5); [M+H]+ 286.13975; [M-H]- 284.12519. A plus or minus 5 ppm window on [M+H]+ is plus or minus 0.0014 Da, which is easily met and settles nothing about the hydroxyproline isomer, since every candidate isomer shares the formula exactly. Note the delta that matters most: glycine-proline-glutamate at 301.12739 is exactly 15.99491 Da heavier, which is also the mass of an oxidation, so a plus 16 peak under this name is ambiguous between contamination with a different marketed tripeptide and an oxidized species.

Salt / variant note

The stereo and REGIO isomers, none of which any mass method separates: cis-4-hydroxy-L-proline (2S,4S), 4-hydroxy-D-proline and 3-hydroxyproline all give C12H19N3O5 at 285.300 / 285.13247, identical at every decimal place; a D-proline at position 2 does the same. Only a chiral method or a chromatographic separation validated against authentic isomer standards distinguishes them, and for a molecule sold on a collagen-repeat rationale the trans-4-hydroxy-L configuration is the whole of the structural claim. Mass-resolvable neighbors: Gly-Pro-Pro, the des-hydroxy tripeptide, C12H19N3O4, 269.301 / 269.13756, minus 15.995 Da, which is what an incompletely hydroxylated or simply cheaper synthesis delivers. Glycine-proline-glutamate (GPE), C12H19N3O6, 301.299 / 301.12739, plus 15.995 Da, a separately marketed tripeptide and an explicit confusable; the delta is exactly one oxygen, which is also the classic oxidation delta, so a plus 16 species under this name is ambiguous between a different product and a degradation product, and only chromatography against both standards resolves it. Pro-Hyp, the dipeptide, C10H16N2O4, 228.248 / 228.11101. Gly-Pro-Hyp-Gly, the chain-extended tetrapeptide, C14H22N4O6, 342.352 / 342.15393. Different molecules under adjacent INCI numbers: Tripeptide-1 (GHK), C14H24N6O4, 340.384 / 340.18590, which is 55 Da heavier and a completely different chemistry; Tripeptide-5 and Tripeptide-10 citrulline, neither of which shares this backbone. Salt and counterion forms, which matter disproportionately on a 285 Da molecule: mono-acetate C14H23N3O7, 345.352 / 345.15360, of which the free peptide is 82.6 percent by mass; a 1:1 trifluoroacetate-paired form C14H20F3N3O7, 399.323 / 399.12533, of which the free peptide is only 71.4 percent. A labeled-milligram figure with no net peptide content can therefore be wrong by nearly thirty percent without anything on the certificate being false. And the formulation substitution: the ingredient is also sold as parts-per-million dilutions in glycerin, water and butylene glycol carriers, which have no formula at all and must never be received against this specification.

2 Class & testing panel

Form

Single article

Testing panel

P3 — panel definitionassigned on the non-proteinogenic hydroxyproline and specifically on its stereochemistry, which is the attribute the marketed rationale depends on and which no mass method can see. The assignment is provisional until a written sequence declaration is on file

3 Primary sources & evidence

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

The finding is an absence, and it is stated in the form the search supports. Under the INCI name Tripeptide-29, targeted PubMed searches located no primary literature at all: no in-vitro study, no animal study, no human trial, and no Cosmetic Ingredient Review Expert Panel safety assessment, in a search demonstrably capable of finding such documents, having returned CIR assessments for four adjacent peptide ingredient classes. A search for a related cosmetic-peptide term returned zero results outright. ClinicalTrials.gov was not queried, so the human-trial position is "none located" rather than "none exist". Grade F on that basis. A separate and adjacent literature exists for Gly-pro-Hyp as A defined chemical entity, and it is recorded by study type precisely so that it is not mistaken for evidence about this article: Yazaki 2017, PMID 28244315, human; Iwai 2005, PMID 16076145, human; Won 2024, PMID 38051020, rat pharmacokinetics; Yang 2024, PMID 38411396, mouse; Kim 2018, PMID 29949889, human randomized trial, n=64, 12 weeks, of an oral preparation containing Gly-Pro-Hyp as one constituent rather than of Gly-Pro-Hyp alone. Every one of those concerns oral administration of a collagen hydrolysate or its constituent, which is a different route and a different substance from a topical cosmetic raw material; the transfer of those findings to a topical product is the characteristic form of citation laundering in this market. A general systematic review of over-the-counter topical anti-aging ingredients is recorded at Imhof and Leuthard 2021, PMID 32882685. No compound-specific irritation, sensitization, cytotoxicity, genotoxicity, carcinogenicity, immunogenicity, reproductive-toxicity or pharmacokinetic data were retrieved, and no adverse-event reports were retrieved; those are absences in the retrieved literature, recorded as such.

4 Storage & specification

Storage

Lyophilized powder, minus 20 degrees C, desiccated, protected from light and moisture, with reconstituted solutions refrigerated and used promptly. The molecule is small, polar and freely water-soluble, so the practical risk in storage is water uptake rather than chemical instability, and water shows up directly in the Karl Fischer result and indirectly in every content figure calculated from weight. That handling condition is a general peptide convention plus vendor specification rather than a measured result: no compound-specific stability data exist.

Shelf life

Provisional retest interval of 24 months at minus 20 degrees C in the sealed original container, pending the company's own stability data, and provisional in a stronger sense than usual: a retest interval is a statement that a measured property has been shown to hold, and the property here is an identity that has not yet been fixed. The stability-indicating method must resolve the minus 15.995 Da and plus 15.995 Da species from parent, which an area-percent figure on an unresolved pair will not do.