Palmitoyl Tripeptide-5 (Syn-Coll)

1 Identity

Acylated cosmetic tripeptide (lipopeptide conjugate). A synthetic tripeptide Lys-Val-Lys carrying a single C16:0 palmitoyl group amide-bonded to the N-terminal alpha-amino group of Lys1. Two free lysine epsilon-amines make the conjugate strongly basic and hygroscopic; there is no aromatic residue, no sulfur, no metal, no disulfide and no chromophore stronger than the amide bond. Sold as a topical bulk cosmetic ingredient and laboratory raw material. and SYN-COLL or Syn-Coll. Two CAS numbers are in live commerce and they are not interchangeable: 623172-55-4 is used for the free base, cataloged by one reagent supplier against formula C33H65N5O5 and MW 611.9, and 623172-56-5 is used for the trifluoroacetate salt sold by an institutional supplier.

Sequence

N-hexadecanoyl(palmitoyl)-L-Lys-L-Val-L-Lys-OH (Pal-KVK). One C16:0 palmitoyl group amide-bonded to the alpha-amino group of Lys1; free C-terminal carboxylic acid on Lys3; no amidation, no cyclization, no disulfide; all three residues L and proteinogenic. The sequence statement is incomplete without the regiochemistry statement: two lysine epsilon-amines plus the N-terminal alpha-amine give three candidate acylation sites, all three products carry the identical formula and the identical exact mass, and the article is specifically the N-alpha-palmitoyl regioisomer. It is also incomplete without the salt statement, because the two CAS numbers in commerce are the free base and the bis-trifluoroacetate.

Molecular formula

C33H65N5O5 as the free base, corroborated by two independent suppliers under the two registry numbers and reconstructing exactly from Pal-Lys-Val-Lys. As the bis-trifluoroacetate salt, C33H65N5O5 . 2CF3COOH, which is C37H67F6N5O9 as a formula unit. Free tripeptide KVK C17H35N5O4. Carrier dilutions in glycerin, water or butylene glycol have no formula and must not be received against this specification.

Average mass

611.913 Da free base (C33H65N5O5) on IUPAC 2021 abridged conventional atomic weights (C 12.011, H 1.008, N 14.007, O 15.999); a reagent catalog prints 611.9 for the same formula and other listings print the same formula, and all agree within rounding. As the bis-trifluoroacetate formula weight, 839.96 - that is C33H65N5O5 plus two CF3COOH at 114.02 each, and it matches the 840.0 published for the salt article to the rounding. The gap between the two salt states is 228.05 Da, which is 27.2 percent of the shipped mass, and it is a content-calculation difference on every lot rather than a labeling nicety: 100 mg of the trifluoroacetate article contains about 72.8 mg of free base. Free tripeptide KVK 373.498, exactly 238.42 Da lighter, which is the palmitoyl delta.

Monoisotopic mass

611.49857 Da neutral free base (C33H65N5O5); [M+H]+ 612.50585; [M+2H]2+ m/z 306.75656; [M-H]- 611.49129. Identity window on [M+H]+ at plus or minus 5 ppm is plus or minus 0.0031 Da. Electrospray never observes the trifluoroacetate salt - it dissociates in solution and the measured ion is the protonated free base at 612.50585 - so 840.0 is a formula weight and not a mass any instrument reports; for completeness the neutral monoisotopic mass of the C37H67F6N5O9 formula unit is 839.48430, a number with a use in gravimetric calculation and no use in a mass spectrum. Free tripeptide KVK 373.26890 neutral, [M+H]+ 374.27618. C-terminal amide 610.51455 neutral, 0.984 Da below parent.

Salt / variant note

(1) salt axis, live in the market right now and the largest single number on this record: free base C33H65N5O5 at 611.913 against bis-trifluoroacetate at 839.96 formula weight, a 27.2 percent content difference, with one reagent catalog selling the free base under CAS 623172-55-4 and one institutional supplier selling the trifluoroacetate salt under CAS 623172-56-5. A mono-trifluoroacetate at 725.94 is a third possibility that neither number covers. Unlike the rest of this cosmetic group, the institutional channel lists this article below the consumer channel, so a low quoted price is not on its own evidence of a substituted article. (2) des-palmitoyl free tripeptide KVK, C17H35N5O4, 373.498 / 373.26890, [M+H]+ 374.27618 - 238.42 Da light, the incomplete-acylation failure and the cheapest substitution; blended with free palmitic acid it gives a plausible elemental analysis while the spectrum shows two peaks and no conjugate. (3) regioisomers carrying no mass difference: acylation at either lysine epsilon-amine gives the identical C33H65N5O5 and the identical 611.49857, and only MS/MS or co-elution against a qualified standard separates them from the N-alpha article. (4) DI-palmitoyl over-acylation C49H95N5O6, 850.328 / 849.72824 - plus 238.42 Da, the same control failure in the other direction, and note that its formula weight sits within 10 Da of the bis-trifluoroacetate salt formula weight of the correct article, so a document quoting bare 'MW approximately 840-850' with no basis is uninterpretable. (5) acyl-chain axis: myristoyl (C14:0) analogue C31H61N5O5 583.859 / 583.46727, 28.05 Da light; stearoyl (C18:0) analogue C35H69N5O5 639.967 / 639.52987, 28.05 Da heavy. (6) valine substitution: Pal-Lys-Leu-Lys or Pal-Lys-Ile-Lys, C34H67N5O5, 625.940 / 625.51422 - plus 14.03 Da, a single methylene, and the two leucine/isoleucine products are indistinguishable from each other by mass at any resolution. (7) C-terminal amide C33H66N6O4, 610.929 / 610.51455 - 0.984 Da below the free acid. (8) nearest shelf-MATE: palmitoyl tripeptide-38, Pal-Lys-Met(O2)-Lys, C33H65N5O7S at 675.971 - identical carbon and hydrogen counts, plus sulfur and two oxygens, 64.06 Da heavy, and the two are adjacent line items on cosmetic ingredient lists. Further same-shelf articles: palmitoyl tripeptide-1 578.799, Pal-AHK 592.826, palmitoyl tetrapeptide-7 694.919, palmitoyl pentapeptide-4 802.068. (9) presentation axis: neat conjugate powder against parts-per-million dilutions in glycerin, water or butylene glycol sold under the same trade name.

2 Class & testing panel

Form

Single article

Testing panel

P2 — panel definition

3 Primary sources & evidence

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

No compound-specific primary literature has been located for this article under its own name - in vitro, animal or human - in cosmeceutical peptide reviews, in Cosmetic Ingredient Review safety assessments or in targeted searches on the INCI name. The efficacy claims made for this group trace to supplier technical literature rather than to independent peer-reviewed primary literature under the ingredient's own name. Class-level citations, kept separate on this page and belonging to other molecules: Kraeling et al., Cutan Ocul Toxicol 2015, PMID 24754410, in vitro, excised human cadaver and hairless guinea pig skin; Choi et al., Biomol Ther 2014, PMID 25143811, in vitro, hairless mouse skin; Imhof and Leuthard, Dermatology 2021, PMID 32882685, systematic review of over-the-counter topical antiaging agents; Wang et al., Adv Sci 2025, PMID 39783908, solubility and delivery of palmitoylated cosmetic peptides; Chen et al., World J Clin Cases 2021, PMID 33748252, case report on injection of a cosmetic peptide. No human trial of this article has been located and no registry number is quoted because none was found - an absence of located evidence rather than a demonstration that none exists. The Cosmetic Ingredient Review has published safety assessments for other peptide ingredients; none has been located for this one. Literature volume by study type is printed at the head of the research page.

4 Storage & specification

Storage

Off-white to pale-tan lyophilized powder or friable waxy solid, acetate salt unless the trifluoroacetate is specifically ordered and declared, packed in amber glass with a nitrogen headspace and a desiccant sachet. Laboratory and cosmetic raw-material presentation: non-sterile, no sterility claim, no stoppered-and-crimped injection format. Labeled condition 2-8 degrees C, protected from light and moisture; the institutional supplier of the trifluoroacetate article labels it -20 degrees C, which is recorded here as that supplier's condition and not adopted by default. Two free lysine epsilon-amines make the solid markedly hygroscopic, so the jar is equilibrated to room temperature sealed before opening and closed under nitrogen after each withdrawal - a specification item, not a packaging preference, because moisture uptake changes every gravimetric calculation made from the jar. Shipped ambient with a temperature-excursion indicator; excursions to 25 degrees C for up to 14 days cumulative are accepted against the stability protocol and recorded on the lot record. The palmitoyl chain makes the conjugate amphiphilic and poorly water-soluble - the limitation documented for palmitoylated cosmetic peptides at PMID 39783908 - so dissolution for assay uses a named co-solvent system stated on the handling page, which says nothing about route or vehicle.

Shelf life

Provisional 24-month retest interval at 2-8 degrees C, and provisional 36 months at -20 degrees C plus or minus 5 degrees C for the retained reference portion. Both are provisional placeholders for this company's own ICH Q1A-format study on three production lots, long-term at 5 degrees C plus or minus 3 degrees C and accelerated at 25 degrees C / 60 percent RH, which replaces them at the 12-month data point. The stability-indicating attributes are free palmitic acid and des-palmitoyl KVK, not total assay: amide hydrolysis at the acyl linkage regenerates the free tripeptide and free palmitic acid, and a slow drift there is invisible inside an unspecified-impurity bucket. Karl Fischer water is trended alongside them because the article is hygroscopic and water gain alone will move an assay result without any chemical change at all. A retest date is printed on every jar and first-expiry-first-out is enforced against that date rather than against receipt date. The interval is shortened on data and never extended without a completed dataset.