The short version of GHK-Cu fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-02-03. Anything still debated is marked as such rather than presented as settled.
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.
Copper(II) binds the peptide through four nitrogen donors: the terminal amino group, the imidazole nitrogen of histidine, and two deprotonated amide nitrogens of the peptide backbone. This tetradentate arrangement gives a roughly square-planar geometry, the thermodynamically favoured form near neutral pH. Because the amide nitrogens must lose a proton before they can coordinate, complex formation is strongly pH-dependent, and the fully coordinated species dominates only above mildly acidic conditions. Electronic transitions within the copper d orbital set produce the characteristic blue to violet colour in aqueous solution.
Endogenous GHK occurs in blood plasma, saliva, and urine, and reported plasma concentrations decline with age in several studies. Researchers have proposed that the peptide acts as a copper carrier that delivers the metal to cells and to sites of injury. That transport role is a hypothesis supported by binding measurements and tissue-distribution data rather than a settled mechanism, and the peptide is generally described as a minor contributor to total plasma copper transport. Values reported in wound fluid and certain tissue extracts are higher than in circulating plasma.
Analytical verification commonly relies on high-performance liquid chromatography for purity assessment and mass spectrometry for identity confirmation. Spectroscopic methods such as UV-visible absorption and electron paramagnetic resonance can probe the metal centre itself, since the d9 configuration of copper(II) produces characteristic signals. Elemental analysis or plasma-based techniques quantify copper content. Because each method reports a different aspect of the same sample, purity figures are most meaningful when the technique and its detection wavelength are stated alongside the value.
Stability of the complex in solution depends on pH, temperature, and the presence of competing ligands. It is generally described as more resistant to breakdown than the metal-free chain, since coordination reduces susceptibility to enzymatic attack. Oxidation and hydrolysis can nevertheless proceed over time in aqueous media. Storage guidance in laboratory settings commonly involves refrigeration, protection from light, and avoidance of strongly alkaline conditions. Published data on long-term behaviour vary considerably and depend on the specific matrix.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Copper(II)-tripeptide complex | One peptide ligand with one coordinated metal centre |
| Peptide sequence | Gly-His-Lys | Three residues written in one-letter notation |
| Free peptide mass | 340.4 g/mol | Metal-free GHK; the complex has a higher mass |
| Appearance | Blue to violet solid or solution | Colour originates from copper d orbital transitions |
| Storage | Desiccated, -20 °C, protected from light | Dry powder is more stable than dissolved material |
The copper-binding activity of this sequence was described in the 1970s during studies of liver tissue and plasma factors. Early work identified the peptide as a component that influenced copper uptake by cells and that appeared in wound fluid. Later investigations examined its presence across species, reporting the same chain in human and animal samples. A decline in measured concentration with age became a recurring observation, although the underlying causes remain incompletely characterised.
Published studies describe the complex in several research contexts, including collagen synthesis, antioxidant behaviour, and wound repair models. Much of this work is conducted in cultured cells or in small animal systems, and the findings are frequently cited in reviews of copper peptides. Direct clinical evidence in humans is comparatively limited, and reported outcomes vary with formulation and study design. Whether free chain or metal-bound form was used is not always stated, a point that complicates comparison between reports.
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.
Aqueous solutions of GHK-Cu are less stable than the dry powder. The peptide backbone is vulnerable to hydrolysis at extreme pH, and copper can be stripped from the complex by strong chelating agents such as EDTA or citrate. Oxidising agents and high concentrations of ascorbic acid can reduce copper(II) and change the complex, which is one reason formulators often keep such ingredients in separate phases. How quickly these changes occur under real storage conditions depends on pH, buffer, temperature and packaging, and quantitative data on the subject are limited.
The International Nomenclature of Cosmetic Ingredients lists the substance as copper tripeptide-1, the name that appears on most topical product labels. Related designations include copper peptide and GHK-Cu, and the hyphenated form is common in research literature. In cosmetics the material is regulated as an ingredient rather than as a drug, so products may reach the market without evidence of the effects claimed for them. Whether those effects are clinically meaningful is an open question, since most supportive data come from laboratory work and small trials.
GHK-Cu is the copper complex of the tripeptide glycyl-L-histidyl-L-lysine, a short sequence found naturally in human plasma, saliva and urine. Loren Pickart reported the isolation of the free peptide in 1973 while studying factors that influenced the growth of aged liver cells in culture. The peptide was later shown to bind copper(II) with high affinity, and the metal-bound form became the focus of most subsequent research. Its concentration in circulation declines markedly with age, a pattern that is well documented, though the physiological consequences of that decline remain debated.
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.
Copper peptide solutions tend to resist degradation better than many free peptides, because the bound metal protects the N-terminus and reduces susceptibility to some peptidases. Backbone hydrolysis, oxidation of the histidine imidazole ring, and photochemical reactions remain the principal degradation routes. Aqueous solutions are generally most stable near neutral to mildly acidic pH, while strongly alkaline conditions accelerate hydrolysis. Light exposure is usually avoided, since both the peptide and the copper center can take part in photochemical processes. Stability data published by suppliers often describe short-term behavior rather than multi-year shelf life.
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.
France's constant warfare with the combined forces of different combinations of, and eventually all, of the other major powers of Europe for over two decades finally took its toll. By the end of the Napoleonic Wars, France no longer held the role of the dominant power in continental Europe, as it had since the times of Louis XIV, as the Congress of Vienna produced a "balance of power" by resizing the main powers so they could balance each other and remain at peace. In this regard, Prussia was restored in its former borders, and also received large chunks of Poland and Saxony. Greatly enlarged, Prussia became a permanent Great Power. In order to drag Prussia's attention towards the west and France, the Congress also gave the Rhineland and Westphalia to Prussia. These industrial regions transformed agrarian Prussia into an industrial leader in the nineteenth century. Britain emerged as the most important economic power, and its Royal Navy held unquestioned naval superiority across the globe well into the 20th century. After the Napoleonic period, nationalism, a relatively new movement, became increasingly significant. This shaped much of the course of future European history. Its growth spelled the beginning of some states and the end of others, as the map of Europe changed dramatically in the hundred years following the Napoleonic Era. Rule by fiefdoms and aristocracy was widely replaced by national ideologies based on shared origins and culture.
Actin-binding proteins (also known as ABPs) are proteins that bind to actin. This may mean ability to bind actin monomers, or polymers, or both. Many actin-binding proteins, including α-actinin, β-spectrin, dystrophin, utrophin and fimbrin, do this through the actin-binding calponin homology domain. This is a list of actin-binding proteins in alphabetical order.
== Ligands == Ac-Val-Gln-(pI)DPhe-DTic-NH2, first MC3 selective agonist, 100x selectivity over MC4. Ac-Val-Gln-DBip-DTic-NH2, 140x selectivity over MC4. Pyrrolidine bis-cyclic guanidines, non-peptide small molecule MC3 agonists, good selectivity over MC4 but not over MC1 or MC5. SHU-9119, mixed MC3/MC4 antagonist.
The two substrates of this enzyme are ribitol and oxidised nicotinamide adenine dinucleotide (NAD+). Its products are D-ribulose, reduced NADH, and a proton. This enzyme participates in pentose and glucuronate interconversions.
showed that small molecule inhibitors of Prp8 intein splicing were selective and effective at slowing the growth of C. neoformans and C. gattii, providing exciting evidence for the antimicrobial potential of intein splicing inhibitors.
Sources: en.wikipedia.org
Structural analogues of psilocybin (4-PO-DMT; O-phosphorylpsilocin) and psilocin (4-HO-DMT) include 4-hydroxytryptamine (4-HT), dimethyltryptamine (DMT), serotonin (5-hydroxytryptamine; 5-HT), bufotenin (5-HO-DMT), 6-hydroxy-DMT, 7-hydroxy-DMT, 4-AcO-DMT (psilacetin; O-acetylpsilocin), 4-PrO-DMT (O-propionylpsilocin), psilomethoxin (4-HO-5-MeO-DMT; 5-methoxypsilocin), 4-MeO-DMT (O-methylpsilocin; PSOM), 4-methyl-DMT, ethocybin (4-PO-DET), baeocystin (4-PO-NMT), aeruginascin (4-PO-TMT), and norbaeocystin (4-PO-T), among others.
Notes: % monoesters and HLB reported in this table are the approximative values indicated by the suppliers for each blend. B= Behenate (22 carbon chain) - S = stearate (18 carbon chain) - O = Oleate (18 carbon chain, 1 unsaturation) - P = Palmitate (16 carbon chain) - M = myristate (14 carbon chain) - L = Laurate (12 carbon chain) It means that a transposition of the HLB scale of the PEO surfactants has been made for defining the HLB of sucrose esters, because both families of surfactants are non-ionic surfactants. There are two issues with this transposition. The first one is that in this numerical transposition of the Griffin's scale to sucrose esters, the monoesters content is supposed to correspond the hydrophilic part of the surfactant what is a strong approximation because the monoesters fraction is not purely hydrophilic, since it also contains a high proportion of hydrophobic fatty chains in mass percent. It means also that, for example, a sucrose laurate blend (a sucrose grafted with a 12 carbon fatty acid) and a sucrose stearate blend (a sucrose grafted with a 18 carbon fatty acid) have the same HLB (see Table), despite the fact that sucrose laurates are really more hydrophilic and water-soluble than sucrose stearates. The second issue is that this HLB scale, established for non-ionic PEO surfactants on the basis of experimental data, is valid only for the latter. This scale has a genuine predictive value for choosing the right PEO surfactant for a given application, typically oil-in-water or water-in-oil emulsification.
=== Scientific instrumentation === HVEC represented a shift in how experimental physics acquired its tools. Before the company's founding, laboratories typically built accelerators from scratch; HVEC's mass-produced instruments made reliable high-voltage machines available to institutions without in-house engineering capacity. The result was a rapid expansion of experimental nuclear physics. At the field's peak in the mid-1970s, nearly 70 percent of published papers relied on data from HVEC accelerators. Presidential science adviser D. Allan Bromley, who worked with the first HVEC tandem at Chalk River, called the machines "superb nuclear science instruments." In a 1984 assessment, he concluded that "of all the accelerators yet devised in nuclear science I believe that a very strong case can be made that the large tandems span the greatest range and scope of physics."
Ishibashi T, Yokoi N, Kinoshita S (2003). "Comparison of the effects of topical levobunolol and timolol solution on the human ocular surface". Cornea. 22 (8): 709–15. doi:10.1097/00003226-200311000-00001. PMID 14576520. S2CID 25444383. Ogasawara H, Yoshida A, Fujio N, Konno S, Ishiko S (1999). "[Effect of topical levobunolol on retinal, optic nerve head, and choroidal circulation in normal volunteers]". Nippon Ganka Gakkai Zasshi. 103 (7): 544–50. PMID 10443129. Leung M, Grunwald J (1997). "Short-term effects of topical levobunolol on the human retinal circulation". Eye. 11 (3): 371–6. doi:10.1038/eye.1997.78. PMID 9373479.
Sources: en.wikipedia.org
This micelle controlled technique provides for unique opportunities for solving complicated separation problems. Despite the poor efficiency of MLC, it has been successfully used in many applications. The use of MLC in the future appears to be extremely advantages in the areas of physiological fluids, pharmaceuticals, and even inorganic ions. The technique has proven to be superior over ion-pairing and ion-exchange for many applications. As new approaches are developed to combat the poor efficiency of MLC, its application is sure to spread and gain more acceptance.
== Catabolism == NAAG is catabolized via NAAG peptidase activity. Two enzymes with NAAG peptidase activity have been cloned, glutamate carboxypeptidase II and glutamate carboxypeptidase III. These enzymes mediate the hydrolysis of NAAG to NAA and glutamate. Their inhibition can produce therapeutic benefits. Two main types of inhibitors of this enzyme are known: compounds related to 2-(phosphonomethyl)pentanedioic acid (2-PMPA) and urea-based analogs of NAAG, including ZJ43, ZJ17, and ZJ11. In rat models, ZJ43 and 2-PMPA reduce perception of inflammatory and neuropathic pain when administered systemically, intracerebrally, or locally, suggesting that NAAG modulates neurotransmission in pain circuits via mGlu3 receptors. The inhibition of NAAG hydrolysis increases the concentration of NAAG in the synaptic space analogous to the effects of MAOIs in increasing the concentration of serotonin. This elevated NAAG gives greater activation of presynaptic mGluR3 receptors, which decrease release of transmitter (glutamate) in the pain signaling pathways of the spinal cord and brain. In the case of traumatic brain injury, the injection of a NAAG peptidase inhibitor reduces neuron and astrocyte death in the hippocampus nearest the site of the injury. In a mouse model of amyotrophic lateral sclerosis (ALS), the chronic inhibition of NAAG peptidase activity delayed the onset of ALS symptoms and slowed the progress of the neuronal death.
Other effects have been reported to include confusion, lethargy, laziness, sleepiness, lightheadedness, feeling faintish and actual fainting, brief but repeated periods of amnesia, fear of psychosis, pupil dilation, paresthesia, nausea, vomiting, abdominal cramps, diarrhea, and muscle tremors, among others. The drug was described as a "seminal" or "archetypal" psychedelic in PiHKAL.
The BOP was aware that the use of pentobarbital as their "new drug choice" would be challenged in the courts because some lawyers had said that "pentobarbital would flood prisoners' lungs with froth and foam, inflicting pain and terror akin to a death by drowning." BOP claimed that these concerns were unjustified and that their two expert witnesses asserted that the use of pentobarbital was "humane". On 25 July 2019, US Attorney General William Barr directed the federal government to resume capital punishment after 16 years, despite shortages of the compound caused by European Union restrictions and a lack of U.S. manufacturers. The federal protocol provides for intravenous administration of two syringes each containing 2.5 grams of pentobarbital sodium followed by a saline flush.
=== Heritage ciders === Heritage ciders are made from both culinary and cider apples, including bittersweet, bittersharp, heirlooms, wild apples and crabapples. Common apples used in heritage cider production include Dabinett, Kingston Black, Roxbury Russet, and Wickson. Heritage ciders are higher in tannins than modern ciders. They range in colour from yellow to amber ranging from brilliant to hazy. Clarity of heritage ciders also depends on the cider making practices used and will differ by cider maker as well. In Canada, some cideries market "Loyalist-style" ciders, which are notably dry and made with McIntosh apples, a Canadian heritage varietal.
Sources: en.wikipedia.org
It consists of a three-amino-acid peptide, glycine-histidine-lysine, bound to one copper(II) ion. The peptide supplies four nitrogen donor atoms, and the resulting complex is stable in neutral aqueous solution. The metal-free peptide is usually called GHK.
The three letters are the standard one-letter codes for glycine, histidine, and lysine. The suffix -Cu indicates the coordinated copper ion. Cosmetic ingredient lists often use the alternative name copper tripeptide-1 for the same complex.
No. Free GHK is the peptide alone, while GHK-Cu contains a bound copper atom. The two differ in colour, charge, and binding behaviour, so any study that measures copper delivery must state which form was used.
Reverse-phase high-performance liquid chromatography with ultraviolet detection is the most common approach. Purity is expressed as a share of total peak area at a specified wavelength. Mass spectrometry is then used to confirm molecular identity.