Everything below concerns GHK-Cu. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-03-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
The peptide portion consists of three amino acids: glycine, histidine and lysine. Copper(II) coordinates through the imidazole nitrogen of histidine, the alpha-amino group of glycine and a deprotonated amide nitrogen of the backbone, producing a roughly square-planar geometry. This arrangement gives the complex its characteristic blue-to-violet colour and helps it resist dissociation in water. Reported stability constants are high, although values differ between studies because of differences in ionic strength and measurement method.
| Property | Value | Notes |
|---|---|---|
| Long-term storage | -20 °C | Dry powder, sealed and protected from light |
| Working storage | 2 to 8 °C | Short-term holding; avoid repeated warming cycles |
| Purity assay | Reversed-phase HPLC with UV detection | Detection commonly near 214 nm |
| Copper assay | ICP-OES or atomic absorption | Confirms metal content and the metal-to-peptide ratio |
| Visible absorption | Roughly 520 to 600 nm | Rapid indicator of complex integrity |
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.
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.
Mechanistic accounts focus on how the complex delivers copper and how the released peptide interacts with the extracellular matrix. Copper is an essential cofactor for lysyl oxidase and other enzymes involved in collagen and elastin cross-linking, and GHK is one of several peptides able to carry the metal. Reported effects include altered gene expression in fibroblasts and changes in matrix metalloproteinase activity, although many of these findings come from cell culture rather than whole organisms. The relative contribution of the peptide backbone, the copper ion, and downstream copper metabolism is not fully resolved.
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.
Proposed mechanisms for copper peptide activity center on delivery of copper ions to cells and on peptide fragments acting as signaling molecules. Copper is a cofactor for enzymes involved in collagen cross-linking and antioxidant defense, and the peptide may improve its availability at target sites. Separately, the tripeptide and its breakdown products have been reported to influence gene expression in cultured fibroblasts. Much of this evidence comes from laboratory cell cultures and animal models rather than controlled human trials. The relative contribution of the copper ion and the peptide sequence is therefore not fully settled.
Stability depends on temperature, light exposure, moisture, and the presence of oxidizing or reducing agents. Solid material held dry and protected from light is generally more stable than aqueous solutions, which can undergo gradual degradation. Recommended storage in much of the literature is a freezer at around minus twenty degrees Celsius for long-term retention, with working aliquots kept cold and shielded from light. Repeated freeze-thaw cycles and alkaline pH are commonly noted as factors that accelerate loss of the intact complex, though exact degradation rates vary.
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.
Material described in research and cosmetic supply chains is typically a synthetic peptide supplied as a lyophilized powder. Purity is commonly reported through chromatographic separation, often at 95 percent or higher, while copper content is confirmed by separate elemental analysis. Batch variation in color and solubility can reflect residual counter-ions, moisture, or partial oxidation of the peptide. Because the complex is not a single regulatory entity, specifications differ between suppliers and are not standardized internationally.
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.
=== Interaction with ethanol === Concurrent use with ethanol is contraindicated because fomepizole is known to prolong the half-life of ethanol via inhibiting its metabolism to acetaldehyde by alcohol dehydrogenase.
The set point theories of hunger and eating are a group of theories developed in the 1940s and 1950s that operate under the assumption that hunger is the result of an energy deficit and that eating is a means by which energy resources are returned to their optimal level, or energy set point. According to this assumption, a person's energy resources are thought to be at or near their set point soon after eating, and are thought to decline after that. Once the person's energy levels fall below a certain threshold, the sensation of hunger is experienced, which is the body's way of motivating the person to eat again. The set point assumption is a negative feedback mechanism. Two popular set point theories include the glucostatic set point theory and the lipostatic set point theory. The set point theories of hunger and eating present a number of weaknesses.
As protons cross the membrane through the channel in the base of ATP synthase, the FO proton-driven motor rotates. Rotation might be caused by changes in the ionization of amino acids in the ring of c subunits causing electrostatic interactions that propel the ring of c subunits past the proton channel. This rotating ring in turn drives the rotation of the central axle (the γ subunit stalk) within the α and β subunits. The α and β subunits are prevented from rotating themselves by the side-arm, which acts as a stator. This movement of the tip of the γ subunit within the ball of α and β subunits provides the energy for the active sites in the β subunits to undergo a cycle of movements that produces and then releases ATP.
== Deaths == January 6 – Alex Felipe, 32, futsal player (Sporting CP, Norilsk Nickel, national team) January 10 – Isabel Veloso, 19, social media influencer January 24 – Constantino de Oliveira Júnior, 57, founder and CEO (2004–2012) of Gol Linhas Aéreas February 4 – Ricardo Schnetzer, 72, voice actor February 13 – José Álvaro Moisés, 81, political scientist. April 17 – Oscar Schmidt, 68, Hall of Fame basketball player (JuveCaserta, Corinthians, national team). April 18 – Oscar Andrade, 68, deputy (1996–2003). April 19 – Gerardo Renault, 96, Minas Gerais MLA (1968–1978), deputy (1978–1986). April 27 – Luciana Novaes, 42, social worker, politician, and Rio de Janeiro city councilwoman. May 4 – Hermano da Silva Ramos, 100, French-Brazilian racing driver (Formula One). May 2 – Raimundo Rodrigues Pereira, 85, journalist. May 5 – Guto Graça Mello, 78, composer and music producer. May 23 – Gabriel Ganley, 22, bodybuilder and social media influencer. June 9 – Orlando Senna, 86, film director (Iracema: Uma Transa Amazônica). June 11 – Brito, 86, football player. June 14 – Oliver Tree, 32, American singer-songwriter. Lucas Frota, 27, record producer, musician, and DJ. June 19 – Brasão, 44, footballer (Athletico Paranaense, Santa Cruz, Salgaocar). July 3 – Lydia Möcklinghoff, 45, German ecologist and zoologist. July 7 – Benedito Ruy Barbosa, 95, telenovela writer (Pantanal, O Rei do Gado, Terra Nostra). July 16 – Renato Machado, 83, newscaster and journalist (TV Globo). July 26 – Octavio Gallotti, 95, minister (1984–2000) and president (1991, 1993–1995) of the Supreme Federal Court.
D-amino-acid transaminase (EC 2.6.1.21) is an enzyme originally characterised from bacteria that catalyzes several reversible chemical reactions that interconvert specific D-amino acids and α-ketoglutaric acid with the corresponding α-keto acid and D-glutamic acid. For example, it can use D-alanine as a substrate:
Sources: en.wikipedia.org
== Medical uses == Diazoxide is used as a vasodilator in the treatment of acute hypertension or malignant hypertension. Diazoxide also inhibits the secretion of insulin by opening ATP-sensitive potassium channel of beta cells of the pancreas; thus, it is used to counter hypoglycemia in disease states such as insulinoma (a tumor producing insulin) or congenital hyperinsulinism.
In February 2020, the FDA requested that the manufacturer of lorcaserin voluntarily withdraw the drug from the US market because a safety clinical trial showed an increased occurrence of cancer. The drug manufacturer, Eisai, voluntarily withdrew the drug.
While APHL primarily focuses on public health laboratories in the United States, their global health program makes an effort to help other countries strengthen their own laboratory practices.APHL works with more than 30 countries to: Share effective testing procedures Develop laboratory policies Improve the quality of data Train laboratory leaders Utilize information management systems Create strategies to monitor and detect Establish emergency response programs Design training programs APHL also works with public health laboratories around the world to share information on global health crises and promotes cross-border collaboration.
Aldo-keto reductase family 1 (AKR1) is a family of aldo-keto reductase enzymes that is involved in steroid metabolism. It includes the AKR1C and AKR1D subgroups, which respectively consist of AKR1C1–AKR1C4 and AKR1D1. Together with short-chain dehydrogenase/reductases (SDRs), these enzymes catalyze oxidoreductions, act on the C3, C5, C11, C17 and C20 positions of steroids, and function as 3α-HSDTooltip 3α-Hydroxysteroid dehydrogenases, 3β-HSDsTooltip 3β-Hydroxysteroid dehydrogenases, 5β-reductases, 11β-HSDsTooltip 11β-Hydroxysteroid dehydrogenases, 17β-HSDsTooltip 17β-hydroxysteroid dehydrogenases, and 20α-HSDsTooltip 20α-Hydroxysteroid dehydrogenases, respectively. The AKR1C enzymes act as 3-, 17- and 20-ketosteroid reductases, while AKR1D1 acts as the sole 5β-reductase in humans. AKR1A1; AKR1B1; AKR1B10; AKR1C1; AKR1C2; AKR1C3; AKR1C4; AKR1D1; Others Steroidogenic enzyme
γ-Aminobutyric acid (GABA) prodrugs include progabide and tolgabide. Picamilon (N-nicotinoyl-GABA) has been claimed to be a prodrug of GABA, but has not actually been demonstrated to be converted into GABA. N-Benzoyl-GABA is of very similar chemical structure as picamilon and has also been claimed to be a prodrug of GABA, but this remains unclear similarly. Pivagabine (N-pivaloyl-GABA) was once thought to be a prodrug of GABA, but this proved not to be the case. Cetyl-GABA (GABA cetyl ester) is another prodrug of GABA. 4-Amino-1-butanol is known to be converted into GABA through the actions of aldehyde reductase (ALR) and aldehyde dehydrogenase (ALDH). 4-Amino-1-butanol is to GABA as 1,4-butanediol (4-hydroxy-1-butanol; 1,4-BD) is to γ-hydroxybutyric acid (GHB) (with 1,4-BD being a well-known prodrug of GHB). The metabolic intermediate γ-aminobutyraldehyde (GABAL) is also converted into GABA. A number of γ-hydroxybutyric acid (GHB) prodrugs are known. These include 1,4-butanediol (1,4-BD) and γ-butyrolactone (GBL), as well as the metabolic intermediate γ-hydroxybutyraldehyde (GHBAL).
Sources: en.wikipedia.org
Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. Its principal commercial source is as a by-product from the processing of the rare earth phosphate mineral monazite (Ce,La,...)PO4, which has concentrations of only 0.0001% of the element, not much higher than the abundance of lutetium in the Earth crust of about 0.5 mg/kg. No lutetium-dominant minerals are currently known. The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia. The world production of lutetium (in the form of oxide) is about 10 tonnes per year. Pure lutetium metal is very difficult to prepare. It is one of the rarest and most expensive of the rare earth metals with the price about US$10,000 per kilogram, or about one-fourth that of gold. Crushed minerals are treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. Several rare earth metals, including lutetium, are separated as a double salt with ammonium nitrate by crystallization. Lutetium is separated by ion exchange.
=== Pharmacokinetics === The oral bioavailability of cannabidiol is approximately 6% in fasting state and 36.5–57.3% in fed-state in humans, while its bioavailability via inhalation is 11–45% (mean 31%). The oral bioavailability of cannabidiol varies based on several factors such as formulation, dose, and food intake. The sublingual bioavailability of cannabidiol is approximately 12–35%. The elimination half-life of cannabidiol in blood is 56–61 hours after oral doses twice per day over 7 days. Based on the pharmacokinetic analysis of long-term dosing of cannabidiol in humans, the terminal elimination half-life is estimated to be >134 hours. Cannabidiol is metabolized in the liver as well as in the intestines by cytochrome P450 enzymes.
In the mid-1960s James R. Rice (then at Brown University) and G. P. Cherepanov independently developed a new toughness measure to describe the case where there is sufficient crack-tip deformation that the part no longer obeys the linear-elastic approximation. Rice's analysis, which assumes non-linear elastic (or monotonic deformation theory plastic) deformation ahead of the crack tip, is designated the J-integral. This analysis is limited to situations where plastic deformation at the crack tip does not extend to the furthest edge of the loaded part. It also demands that the assumed non-linear elastic behavior of the material is a reasonable approximation in shape and magnitude to the real material's load response. The elastic-plastic failure parameter is designated JIc and is conventionally converted to KIc using the equation below. Also note that the J integral approach reduces to the Griffith theory for linear-elastic behavior. The mathematical definition of J-integral is as follows:
== Causes == Disease: Infections including an anorectal abscess and inflammatory diseases including Crohn's disease and ulcerative colitis can result in fistulas. Fistulas to the anus may occur in hidradenitis suppurativa. In women, fistulas can also occur following pelvic infection and inflammation.
Sources: en.wikipedia.org
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.
The colour comes from electronic transitions between the copper ion and the surrounding peptide nitrogen atoms. The resulting absorption sits in the visible region, giving the solid and its solutions a blue to violet appearance. Loss of colour can indicate that the copper has dissociated from the peptide.
Chromatography establishes the identity and purity of the peptide, while elemental analysis establishes the copper content. The two results should agree with a one-to-one ratio. Visible spectroscopy adds a quick check that the complex itself is intact.
It is a complex of a three-amino-acid peptide, glycine, histidine and lysine, bound to a single copper(II) ion. The metal is held mainly by the histidine side chain and the peptide backbone. Most commercial material is supplied as an acetate salt rather than as the free complex.