If you have been reading about Purity assay and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-09-09. Numbers and descriptions here follow the published literature rather than marketing material.
The molecular weight and charge of GHK-Cu depend on the pH and the number of coordinated ligands. At neutral pH, the peptide typically binds one copper ion, but ternary complexes with other biomolecules can form. Spectroscopic methods such as electron paramagnetic resonance and circular dichroism are used to study the coordination environment. Reports on the exact geometry vary because the complex is dynamic in solution. Researchers often use synthetic GHK-Cu rather than extracted material to control stoichiometry and purity.
GHK-Cu is a coordination complex formed from the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide binds copper through its histidine imidazole nitrogen, the terminal amino group, and the deprotonated amide nitrogen. This arrangement creates a square-planar or distorted geometry around the metal center, depending on pH and the presence of competing ligands. The complex occurs naturally in human plasma, saliva, and urine at low concentrations, and its sequence is conserved across many vertebrate species.
Dry material is normally held cold, commonly at -20 °C for long-term storage and 2 to 8 °C for working quantities, protected from light and moisture. Vials should be allowed to reach room temperature before opening so that condensation does not form on the powder. In liquid formulations the complex is generally kept near neutral to slightly acidic pH, because strongly alkaline conditions favour precipitation of copper hydroxide. Antioxidants or chelate-stabilising excipients are often added, though the specific approaches are proprietary and rarely published in detail.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry to confirm the expected mass. Copper content is measured separately by inductively coupled plasma optical emission spectrometry or atomic absorption spectroscopy, because the peptide assay alone does not establish the metal-to-peptide ratio. Visible spectroscopy provides a rapid check on complex integrity through the absorption band in the visible region. Agreement between the peptide assay and the copper assay is the practical test of whether a sample is the intended complex rather than a mixture.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Gly-His-Lys | Tripeptide; copper binds via His and N-terminus |
| Copper stoichiometry | Typically 1 Cu(II) per peptide | Can form ternary complexes under some conditions |
| Molecular formula (peptide) | C14H24N6O4 | Free peptide; copper complex mass differs |
| Appearance (solid) | Blue to blue-green powder | Color derives from copper d-d transitions |
| Solubility | Soluble in water and polar solvents | Solubility depends on pH and counterions |
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide binds copper through its histidine imidazole nitrogen, its terminal amino group, and a deprotonated amide nitrogen, creating a stable chelate ring. The resulting complex carries a distinctive blue to blue-violet color, which arises from copper d-d electronic transitions. In the solid state it is usually handled as a powder, while in solution the complex can dissociate and re-form depending on pH and competing ligands. The name copper tripeptide-1 is widely used in ingredient listings.
The tripeptide was first isolated from a human plasma filtrate in 1973 during studies of tissue repair factors. Later work detected the free peptide and its copper complex in saliva, urine, and wound fluid, suggesting a natural role in tissue remodeling. Plasma concentrations reported in early literature decline with age, a pattern often cited in discussions of skin aging. Whether these endogenous levels are directly functional or largely incidental remains an open question. The peptide sequence is conserved across mammalian species.
Solid GHK-Cu is generally stored as a dry powder under frozen conditions to limit degradation. The peptide bond can hydrolyze, and the copper center can be displaced by strong chelators such as EDTA. Aqueous solutions are less stable than the solid and may lose color or form precipitates over time. Temperature, pH, and oxygen exposure are the main variables that affect shelf life. Neutral to slightly acidic conditions tend to preserve the complex better than strongly alkaline media.
Routine handling calls for minimizing freeze-thaw cycles and preparing solutions shortly before use. Glass or inert plastic containers reduce adsorption and metal leaching. Working stocks are often kept at 2–8 °C for short periods, while long-term reference material stays at −20 °C or below. Light protection is prudent because prolonged exposure may accelerate oxidation of the peptide. Documentation of lot number, concentration, and preparation date supports reproducibility in laboratory work.
Analytical verification typically combines reversed-phase high-performance liquid chromatography with ultraviolet-visible detection. The copper complex absorbs visible light near 600–630 nm, giving a characteristic blue signal. Mass spectrometry confirms molecular mass and can detect free peptide or mismatched copper stoichiometry. Copper content is often measured independently by inductively coupled plasma mass spectrometry or atomic absorption spectroscopy. Purity, counterion identity, and residual solvents are additional quality-control parameters that methods may address.
GHK-Cu is the copper-binding complex formed by the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The free peptide is usually written as GHK, and the complex is written as GHK-Cu or Cu-GHK. The sequence was identified in human plasma and later detected in saliva and urine. Its name comes from the single-letter codes of glycine, histidine and lysine. The complex is widely described as a naturally occurring carrier of copper in blood rather than as a free peptide with its own hormonal role.
Copper binds to the peptide through the histidine imidazole nitrogen and the terminal amino group, forming a stable square-planar complex. Binding constants reported for copper(II) with GHK are high, so the peptide competes effectively for copper in solution. The complex absorbs visible light, which gives solutions a blue to violet colour. Whether the metal-free peptide has a distinct biological function of its own is still an open question; some work treats it mainly as a copper delivery vehicle, while other work reports peptide-specific effects.
The sequence carries three residues in the order glycine, histidine, lysine, which places a small, flexible chain around a single metal centre. Compared with larger copper-binding proteins, the complex is compact and its coordination chemistry can be reproduced with synthetic peptide in a laboratory. Published structural work agrees on the nitrogen donor set but differs in the exact geometry assigned under some conditions, so the arrangement is best treated as well characterised in outline rather than fixed in every detail.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide was isolated from human plasma in the early 1970s by Loren Pickart, who observed that a plasma fraction from young donors stimulated growth in cultured liver cells. The copper-bound form is abbreviated GHK-Cu, while the metal-free peptide is written simply as GHK. In the research literature the complex also appears as copper tripeptide-1 and as glycyl-histidyl-lysine copper complex.
== Portrayal in the media == Woodroof’s life was the basis of the 2013 film Dallas Buyers Club. He was portrayed in the film by Matthew McConaughey, who won an Academy Award for Best Actor for his performance as Woodroof.
=== Antimalarial === Doxycycline is active against the erythrocytic stages of Plasmodium falciparum, a protozoan parasite that causes malaria, but it is not active against the gametocytes of P. falciparum. As such, doxycycline is used to prevent malaria, but not recommended alone for initial treatment of malaria, even when the parasite is doxycycline-sensitive, because the antimalarial effect of doxycycline is delayed by 48 to 96 hours owing to a "delayed death" mechanism in which parasites complete their current replication cycle before dying in the next cycle. For this reason, doxycycline prophylaxis must be continued for four weeks after leaving a malarious area, compared with only seven days for atovaquone/proguanil. Doxycycline blocks protein production in the apicoplast (an organelle) of P. falciparum. This disrupts the parasite's ability to produce fatty acids, which are essential for its growth, and impairs the production of heme, a cofactor. These effects occur late in the parasite's life cycle during the blood stage (the erythrocytic cycle, when the parasite replicates inside human red blood cells). By blocking important processes in the parasite, doxycycline both inhibits the growth and prevents the replication of P. falciparum. Doxycycline does not directly kill living P. falciparum, but creates conditions that prevent their growth and replication. The World Health Organization (WHO) guidelines state that the combination of doxycycline with either artesunate or quinine may be used for the treatment of uncomplicated malaria due to P.
=== Athlete biological passport === The athlete biological passport is a program that tracks the location of an athlete to combat doping in sports. This means that the athlete can be monitored and drug tested wherever they are and this data can be compared to the history of their doping test results. There is an ongoing discussion about how this measure can be seen as a violation of an individual's privacy.
=== Cellular mechanisms === DNA polymerases, used in DNA replication, have a high specificity of 104 to 106-fold in base pairing. They have proofreading abilities to correct incorrect matches, allowing 90-99.9% of mismatches to be excised and repaired. The base mismatches that go unnoticed are repaired by the DNA mismatch repair pathway, also inherent in cells. The DNA mismatch repair pathway uses exonucleases that move along the DNA strand and remove the incorrectly incorporated base in order for DNA polymerase to fill in the correct base.Exonuclease1 is involved in many DNA repair systems and moves 5' to 3' on the DNA strand.
Sources: en.wikipedia.org
It is divided between its east and west coasts by the Titiwangsa Mountains, rising to a peak elevation of 2,183 metres (7,162 ft) at Mount Korbu, part of a series of mountain ranges running down the centre of the peninsula. These mountains are heavily forested, and mainly composed of granite and other igneous rocks. Much of it has been eroded, creating a karst landscape. The range is the origin of some of Peninsular Malaysia's river systems. The coastal plains surrounding the peninsula reach a maximum width of 50 kilometres (31 mi), and the peninsula's coastline is nearly 1,931 km (1,200 mi) long, although harbours are only available on the western side.
=== Riboflavin kinase === Riboflavin kinase catalyzes the phosphorylation of riboflavin to create flavin mononucleotide(FMN). It has an ordered binding mechanism where riboflavin must bind to the kinase before it binds to the ATP molecule. Divalent cations help coordinate the nucleotide. The general mechanism is shown in the figure below. Riboflavin kinase plays an important role in cells, as FMN is an important cofactor. FMN also is a precursor to flavin adenine dinucleotide(FAD), a redox cofactor used by many enzymes, including many in metabolism. In fact, there are some enzymes that are capable of carrying out both the phosphorylation of riboflavin to FMN, as well as the FMN to FAD reaction. Riboflavin kinase may help prevent stroke, and could possibly be used as a treatment in the future. It is also implicated in infection, when studied in mice.
The formation of an astatine compound with hydrogen—usually referred to as hydrogen astatide—was noted by the pioneers of astatine chemistry. As mentioned, there are grounds for instead referring to this compound as astatine hydride. It is easily oxidized; acidification by dilute nitric acid gives the At0 or At+ forms, and the subsequent addition of silver(I) may only partially, at best, precipitate astatine as silver(I) astatide (AgAt). Iodine, in contrast, is not oxidized, and precipitates readily as silver(I) iodide. Astatine is known to bind to boron, carbon, and nitrogen. Various boron cage compounds have been prepared with At–B bonds, these being more stable than At–C bonds. Astatine can replace a hydrogen atom in benzene to form astatobenzene C6H5At; this may be oxidized to C6H5AtCl2 by chlorine. By treating this compound with an alkaline solution of hypochlorite, C6H5AtO2 can be produced. The dipyridine-astatine(I) cation, [At(C5H5N)2]+, forms ionic compounds with perchlorate (a non-coordinating anion) and with nitrate, [At(C5H5N)2]NO3. This cation exists as a coordination complex in which two dative covalent bonds separately link the astatine(I) centre with each of the pyridine rings via their nitrogen atoms. With oxygen, there is evidence of the species AtO− and AtO+ in aqueous solution, formed by the reaction of astatine with an oxidant such as elemental bromine or (in the last case) by sodium persulfate in a solution of perchloric acid.
Sources: en.wikipedia.org
GHK-Cu is a complex of the tripeptide glycyl-L-histidyl-L-lysine with copper(II). The peptide coordinates the metal through its histidine imidazole, terminal amino group, and amide nitrogen. It is studied in biochemistry and dermatological research.
Yes, the peptide and its copper complex have been detected in human plasma, saliva, and urine. Endogenous concentrations are low and vary with physiological state. Its natural functions are not fully established.
Copper binding changes the peptide's charge, shape, and reactivity. The complex can participate in redox chemistry and interact with proteins differently than the free peptide. These differences are why studies specify whether they used GHK or GHK-Cu.
Dry powder is best kept cold, dark and sealed, typically at -20 °C for long-term storage or 2 to 8 °C for material in regular use. Vials should be warmed to room temperature before opening to prevent moisture condensing on the contents. Aqueous stock solutions degrade faster and are usually prepared fresh.