If you have been reading about chelation 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.
Last reviewed on 2026-02-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-lysine and a copper(II) ion. The peptide sequence is conventionally written as Gly-His-Lys, abbreviated GHK. Copper binds through the imidazole nitrogen of histidine, the alpha-amino group, and a deprotonated amide nitrogen, producing a square-planar geometry. The complex carries a net positive charge near physiological pH and is intensely blue in aqueous solution. The metal-free peptide is often written simply as GHK, while the copper-bound form is written GHK-Cu.
The compound was first isolated from human plasma by the biochemist Loren Pickart in 1973. Early work identified it as a factor that altered the behavior of cultured liver cells, and later studies linked it to connective tissue and wound-related processes. Reported plasma concentrations fall markedly between roughly age twenty and age sixty, a pattern that generated interest in copper peptide biology. Whether that decline has functional consequences remains an open question, because differences observed across age groups do not by themselves establish causation. Research interest later expanded into cosmetic and tissue-culture settings.
Discovery of GHK is generally attributed to work in the 1970s that isolated a plasma factor influencing liver cell behavior. Subsequent studies identified the copper-binding tripeptide and its ability to chelate copper with high affinity. Early reports linked the complex to wound healing and tissue remodeling in animal models. The free peptide and the copper-bound form have different properties, so the two are distinguished in the literature. Whether endogenous GHK-Cu serves a single primary physiological role remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22CuN6O4 as the complex | Free peptide is C14H24N6O4 |
| Molecular weight | About 402 g/mol | Free peptide is about 340 g/mol |
| Appearance | Blue solid or blue solution | Color from copper d-d transitions |
| Solubility class | Water-soluble; poor in nonpolar solvents | Ionic character favors aqueous media |
| Common synonyms | Copper tripeptide-1; glycyl-L-histidyl-L-lysine copper | INCI listing uses copper tripeptide-1 |
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.
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.
Identity and purity are commonly assessed by reversed-phase high-performance liquid chromatography, frequently paired with mass spectrometry to confirm the molecular ion. Copper content is measured separately, typically by inductively coupled plasma mass spectrometry or atomic absorption spectroscopy, because the chromatographic signal reports the peptide rather than the metal. Ultraviolet-visible spectroscopy provides a fast check on complex formation, since copper(II) peptide complexes absorb in the visible region. Elemental analysis and amino acid analysis are used less often but remain useful for reference standards. A gap between reported peptide purity and measured copper content is a recurring source of confusion.
Material described as GHK-Cu appears in several distinct markets, including cosmetic ingredients, laboratory reagents, and consumer products, and the quality expectations attached to each differ. A certificate of analysis generally reports peptide purity by chromatography, copper content, appearance, and residual solvents or counterions. Counterion identity matters, because the complex is usually supplied as an acetate or a similar salt, and the counterion contributes to the measured mass. Independent verification of sequence and metal stoichiometry is advisable when a material is used for quantitative work. Batch-to-batch variation is common and should be documented rather than assumed negligible.
Characterizing GHK-Cu requires methods that distinguish the intact complex from free peptide and unbound copper. UV-visible absorption around 600 nm provides a rapid check for copper coordination, while circular dichroism reports on peptide secondary structure. Mass spectrometry confirms the peptide mass and can detect copper adducts under carefully controlled conditions. Electron paramagnetic resonance is particularly informative for Cu(II) because it reveals the ligand field symmetry. No single technique fully defines the complex, so laboratories combine orthogonal methods.
Stability of GHK-Cu in solution depends on pH, temperature, buffer composition, and oxygen exposure. The copper center can undergo reduction or dissociation, especially in the presence of strong metal chelators such as EDTA. Aqueous solutions are often prepared fresh or stored frozen to limit degradation. Lyophilized solid is more stable than liquid formulations, but it can absorb moisture and should be kept dry. Light exposure may also affect copper complexes, though the effect is often modest.
GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine, a short sequence of three amino acids. The peptide was first isolated from human plasma in 1973 during research on factors that influence tissue repair in liver. Its ability to bind copper ions became a central point of interest because the metal changes the peptide's chemistry and its behaviour in laboratory systems. Today the compound appears in cosmetic formulations, cell-culture studies, and biochemistry literature under several names.
The peptide sequence places a histidine in the middle, and this residue dominates metal binding. Copper(II) coordinates through the imidazole nitrogen of histidine and the terminal amino group, forming a stable chelate ring system. Loss of the copper ion leaves the free tripeptide, which has different solubility and reactivity. This structural detail matters because assays that measure only the peptide backbone can miss whether copper is still bound to it.
Several names circulate for the same material, which complicates literature searches. Cosmetic ingredient lists often use copper tripeptide-1, while older biochemistry papers use glycyl-L-histidyl-lysine or its abbreviation GHK. The copper complex is sometimes written as GHK-Cu(II) to make the oxidation state explicit. Terminology is not fully standardized, so matching a compound across sources requires attention to the exact sequence, the counterion, and the stated copper content. Reviews that compare studies must account for these naming differences before drawing conclusions.
It is cleared from the body by tubular secretion and excreted unchanged in the urine; it is undetectable in blood plasma within 24 hours of a single oral dose. The average elimination half-life in plasma is 6.2 hours. Metformin is distributed to (and appears to accumulate in) red blood cells, with a much longer elimination half-life: 17.6 hours (reported as ranging from 18.5 to 31.5 hours in a single-dose study of nondiabetics). Some evidence indicates that liver concentrations of metformin in humans may be two to three times higher than plasma concentrations, due to portal vein absorption and first-pass uptake by the liver in oral administration.
=== PMB === PMB (Probability Matrix from Blocks) of 2004 uses the additivity of evolutionary distances to improve on BLOSUM's analysis of the BLOCKS database. The up-to-date 2001 version of BLOCKS was used to generate a new set of BLOSUM matrices. The "observed substitution frequencies" found in these BLOSUM matrices are used to estimate actual substitution frequencies (with higher evolutionary distance, i.e. lower r, some later replacement can mask earlier replacements). PMB thus defines a true evolutionary model like PAM and JTT do. It is not a symmetric matrix.
== Manufacturing == Erythritol can be produced by enzymatic hydrolysis of the starch from corn to generate glucose. Glucose is then fermented with yeast or another fungus to produce erythritol. Because production through chemical synthesis is commercially not profitable, industrial production is biotechnologically done by fermentation of sugar with a genetically engineered strain of the yeast Yarrowia lipolytica. Alternatively, glycerol may be used as a carbon source and high osmotic pressure to increase yields up to 62%.
Relaxin is a protein hormone of about 6000 Da, first described in 1926 by Frederick Hisaw. The relaxin family peptide hormones belong to the insulin superfamily and consists of seven peptides of high structural but low sequence similarity; relaxin-1 (RLN1), 2 (RLN2) and 3 (RLN3), and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, and INSL6 remain uncharacterised.
Sources: en.wikipedia.org
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=== Religious use === Use of DET by Alan Birnbaum played an important role in the development and beliefs of his psychedelic church The Temple of the True Inner Light, which subsequently employed the unscheduled and hence dipropyltryptamine (DPT) as well as other psychedelics as sacraments.
The secret behind a spider web's stickiness lies in the tiny glue droplets dotting its silk threads. Orb-weaver spiders, such as Larinioides cornutus, coat their silk with a special hygroscopic substance that keeps the glue soft and tacky by drawing in water from the air. This built-in humidity control prevents the adhesive from drying out too quickly. The hardening of the viscoelastic protein is indirectly controlled by changes in water content, which in turn affect the concentration of the ionic liquid. As this balance shifts, the glue's viscosity adjusts, helping the web maintain its grip on captured prey. The web is electrically conductive which causes the silk threads to spring out to trap their quarry, as flying insects tend to gain a static charge which attracts the silk. Neurotoxins have been detected in the glue balls of some spider webs. Presumably these toxins help immobilize prey, but their function could also be antimicrobial, or protection from ants or other animals that steal from the webs or might attack the spider. Spider silk has greater tensile strength than the same weight of steel and much greater elasticity. Its microstructure is under investigation for potential applications in industry, including bullet-proof vests and artificial tendons. Researchers have used genetically modified mammals and bacteria to produce the proteins needed to make this material.
Conrad Elvehjem, the son of Norwegian emigrants to Wisconsin, was born in McFarland, Wisconsin. He progressed through the secondary schools and the University of Wisconsin, where he received his PhD in 1927 with mentor E.B. Hart for his studies of the importance of copper in iron-deficiency anemia. A National Research Council fellowship permitted a year at Cambridge University in England. Elvehjem began teaching in agricultural chemistry at the University of Wisconsin in 1923, and became a full professor in 1936. He became chairman of the biochemistry department in 1944 and dean of the graduate school in 1946, at 45 years of age. He served as dean of the graduate school until he became the university's 13th president in 1958. Picking up on the work of Joseph Goldberger, he found that nicotinic acid cured black tongue in dogs, an analogous disease to pellagra. In the previous year, Elvehjem and his colleague Carl J. Koehn had found that a filtrate factor from a liver extract could cure diet-induced pellagra in chicks. That filtrate extract was designated as the vitamin G fraction, after the late Goldberger. To confirm their findings in dogs, they induced black tongue in these animals with the Goldberger diet of yellow corn, before supplementing the diet with the vitamin G fraction. Elvehjem and his colleagues later were able to isolate and identify nicotinamide and nicotinic acid from vitamin G as the curative factors for black tongue in dogs.
In the north, a scrub-covered, semi-desert plain referred as the Guban lies parallel to the Gulf of Aden littoral. With a width of twelve kilometres in the west to as little as two kilometres in the east, the plain is bisected by watercourses that are essentially beds of dry sand except during the rainy seasons. When the rains arrive, the Guban's low bushes and grass clumps transform into lush vegetation. This coastal strip is part of the Ethiopian xeric grasslands and shrublands ecoregion. Cal Madow is a mountain range in the northeastern part of the country. Extending from several kilometres west of the city of Bosaso to the northwest of Erigavo, it features Somalia's highest peak, Shimbiris, which sits at an elevation of about 2,416 metres (7,927 ft). The rugged east–west ranges of the Karkaar Mountains also lie to the interior of the Gulf of Aden littoral. In the central regions, the country's northern mountain ranges give way to shallow plateaus and typically dry watercourses that are referred to locally as the Ogo. The Ogo's western plateau, in turn, gradually merges into the Haud, an important grazing area for livestock. Somalia has only two permanent rivers, the Jubba and Shabele, both of which begin in the Ethiopian Highlands. These rivers flow southwards, with the Jubba River entering the Indian Ocean at Kismayo. The Shabele River used to enter the sea near Merca, but now reaches a point just southwest of Mogadishu. After that, it consists of swamps and dry reaches before finally disappearing in the desert terrain east of Jilib, near the Jubba River.
Sources: en.wikipedia.org
It is the copper(II) complex of the tripeptide glycyl-L-histidyl-lysine, a sequence of three amino acids. The copper ion is held by the histidine imidazole, the terminal amino group, and an amide nitrogen. The bound form is distinct from the free peptide in charge, color, and stability.
Copper(II) complexes absorb light in the red part of the visible spectrum, so transmitted light appears blue. The absorption arises from electronic transitions within the copper d-orbitals, which are split by the surrounding ligands. The intensity and exact wavelength shift somewhat with pH, solvent, and ligand arrangement.
The free peptide and the copper-bound complex are studied as separate species and do not always behave the same way in assays. Some reported responses are attributed to copper delivery, while others are attributed to the peptide sequence itself. Which fraction drives a given observation is often unresolved in the published work.
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.