Palmitoyl Tripeptide-1 (Pal-GHK)

The GHK matrikine

Gly-His-Lys is one of the best-characterised matrikines: short peptide fragments liberated when extracellular matrix proteins are proteolysed, which then act as signals to the cells embedded in that matrix. GHK occurs within the collagen alpha-2(I) sequence and its concentration in plasma has been reported to decline with age. Cell-culture work has examined its effects on fibroblast expression of collagen, elastin, decorin and glycosaminoglycans, and on the balance between matrix metalloproteinases and their tissue inhibitors.

Why the palmitoyl chain matters

Skin penetration is governed largely by lipophilicity and molecular size. Free GHK is small enough but far too polar, so it stays in aqueous phase and on the surface. Amide-linking palmitic acid to the N-terminal glycine raises log P dramatically and produces an amphiphile that will insert into lipid lamellae. Formulation researchers study lipidated peptides such as this one precisely to characterise that trade-off: penetration improves, but so does the tendency to form micelles, adsorb to container surfaces and behave unpredictably in emulsions.

• Fibroblast collagen and glycosaminoglycan expression in monolayer and three-dimensional dermal-equivalent culture
• Matrix metalloproteinase and TIMP expression as a readout of ECM turnover balance
• Franz-cell and ex vivo skin penetration studies comparing lipidated and unmodified matrikines
• Stability and partitioning behaviour in emulsions, since amphiphilic peptides distribute between oil, water and interface
• Comparative work against palmitoyl pentapeptide-4 and palmitoyl tetrapeptide-7, with which it is often co-formulated in the cosmetic literature

Interpreting results

Warm the sealed vial to room temperature before opening so condensation does not settle on the powder. This peptide is poorly water-soluble — attempting to reconstitute it directly in water usually gives a cloudy dispersion rather than a solution. Common practice is to prepare a concentrated stock in ethanol, propylene glycol or DMSO and dilute into the aqueous working system, or to disperse into a warmed surfactant-containing vehicle with agitation. Because the molecule is amphiphilic it adsorbs to plastic surfaces, so glass or low-binding labware is preferred for stocks. Store the sealed powder at −20 °C, protect solutions from light at 2–8 °C, and record lot number, solvent system and preparation date with every experiment.