The short version of chelation fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C for solid; 2-8 °C for short-term solution use | Avoid repeated freeze-thaw cycles |
| Preferred solvent | Water or aqueous buffer near neutral pH | Nonpolar solvents give poor dissolution |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Copper quantified separately by ICP-MS |
| Principal degradation routes | Backbone hydrolysis, histidine oxidation, photolysis | Alkaline pH accelerates hydrolysis |
| Counterion form | Acetate salt is common | Counterion contributes to measured mass |
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.
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.
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.
Commercial products list GHK-Cu as copper tripeptide-1, a cosmetic ingredient. Formulators value its blue color and water solubility, which allow incorporation into serums, creams, and masks. Regulatory treatment varies: in the United States it appears in cosmetics, while some jurisdictions classify certain claims as drug-like. The compound is not an approved drug for any indication. Studies continue to examine its effects on skin, hair, and wound repair, but dosage, delivery, and long-term safety questions remain open.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and copper(II). The peptide sequence consists of glycine, histidine, and lysine, and its imidazole and amino groups provide binding sites for the metal ion. In the complex, copper is held through nitrogen donors from the histidine side chain, the N-terminal amine, and deprotonated amide nitrogens. The resulting compound is intensely blue and water-soluble. It occurs naturally in human plasma, saliva, and urine at low concentrations.
The peptide was first isolated from human albumin in 1973 by Loren Pickart, who later described its copper-binding behavior. Early work linked the complex to wound healing and tissue remodeling. Plasma levels of GHK decline with age, a pattern that stimulated interest in topical and supplemental applications. Researchers have reported that the tripeptide influences collagen synthesis, antioxidant defense, and inflammatory signaling in cell and animal models. Human clinical evidence remains limited and often relies on small studies.
2-Arachidonoylglycerol (2-AG) is an endocannabinoid, an endogenous agonist of the CB1 receptor and the primary endogenous ligand for the CB2 receptor. It is an ester formed from the omega-6 fatty acid arachidonic acid and glycerol. It is present at relatively high levels in the central nervous system, with cannabinoid neuromodulatory effects. It has been found in bovine and human milk. The chemical was first described in 1994–1995, although it had been discovered some time before that. The activities of phospholipase C (PLC) and diacylglycerol lipase (DAGL) mediate its formation. 2-AG is synthesized from arachidonic acid-containing diacylglycerol (DAG). 2-AG, unlike anandamide (another endocannabinoid), is present at relatively high levels in the central nervous system; it is the most abundant molecular species of monoacylglycerol found in mouse and rat brain (~5–10 nmol/g tissue). Detection of 2-AG in brain tissue is complicated by the relative ease of its isomerization to 1-AG during standard lipid extraction conditions. It has been found in bovine as well as human milk.
The issue has a similar format to the previous volume in that each game in the list has a retrospective article accompanied by a full-page illustration (often a piece of concept art from the game). The list was composed solely by Edge staff; there are no sidebars with readers' comments. The "Top 100" lists contained in the 2007 volume were not reprinted. The criteria Edge used when compiling the list were simple: games from any platform were eligible, series featuring straight-up sequels could only include a single entry, and the games in the list "had to stand up today rather than making the cut for reasons of nostalgia or historic significance." The top 10 of the 100 greatest videogames were: Dark Souls Grand Theft Auto V The Last of Us Bloodborne Half-Life 2 Tetris Super Mario Galaxy 2 The Legend of Zelda: Ocarina of Time Resident Evil 4 Minecraft An Edge Special Edition - "the 100 greatest videogames" (2017)
Amino Acid + ATP + tRNA → Aminoacyl-tRNA + AMP + PPi The net reaction is energetically favorable only because the pyrophosphate (PPi) is later hydrolyzed. The hydrolysis of pyrophosphate to two molecules of inorganic phosphate (Pi) reaction is highly energetically favorable and drives the other two reactions. Together, these highly exergonic reactions take place inside the aminoacyl-tRNA synthetase specific for that amino acid.
At the World Economic Forum in Davos on 21 January 2026, Trump gave a speech containing numerous false claims about Greenland, Denmark and NATO. He falsely claimed that Greenland is a US territory, despite it being associated with the kingdoms of Denmark and Norway for over a millennium, which was inherited by the Danish Unitary State, and later by modern-day Danish Realm. He stated he would not use military force in his attempt to annex Greenland, while not ruling out economic coercion, insisting on "immediate negotiations" despite Denmark telling him Greenland is not for sale. He appeared to issue a veiled warning to European leaders, stating that they could consent to Washington's annexation of Greenland and earn America's gratitude, or refuse and face the assurance that the United States would "remember". During his speech, Trump also repeatedly confused Iceland with Greenland, which Marco Rubio later confirmed. Shortly after, Trump abruptly announced that he and NATO secretary general Mark Rutte had "formed the framework of a future deal with respect to Greenland" and withdrew his threats of punitive tariffs against NATO members. Trump said the proposed deal involved military cooperation related to his Golden Dome project and cooperation between Greenland, the United States and European allies on mineral development. Rutte said his discussion with Trump did not cover control of Greenland, instead focusing on broader Arctic security.
Macrophages can internalize antigens through receptor-mediated phagocytosis. Macrophages have a wide variety of pattern recognition receptors (PRRs) that can recognize microbe-associated molecular patterns (MAMPs) from pathogens. Many PRRs, such as toll-like receptors (TLRs), scavenger receptors (SRs), C-type lectin receptors, among others, recognize pathogens for phagocytosis. Macrophages can also recognize pathogens for phagocytosis indirectly through opsonins, which are molecules that attach to pathogens and mark them for phagocytosis. Opsonins can cause a stronger adhesion between the macrophage and pathogen during phagocytosis, hence opsonins tend to enhance macrophages' phagocytic activity. Both complement proteins and antibodies can bind to antigens and opsonize them. Macrophages have complement receptor 1 (CR1) and 3 (CR3) that recognize pathogen-bound complement proteins C3b and iC3b, respectively, as well as fragment crystallizable γ receptors (FcγRs) that recognize the fragment crystallizable (Fc) region of antigen-bound immunoglobulin G (IgG) antibodies. When phagocytosing and digesting pathogens, macrophages go through a respiratory burst where more oxygen is consumed to supply the energy required for producing reactive oxygen species (ROS) and other antimicrobial molecules that digest the consumed pathogens.
Sources: en.wikipedia.org
where A = 0.02939 mPa·s, B = 507.88 K, and C = 149.3 K. Experimentally determined values of the viscosity are also given in the table below. The values at 20 °C are a useful reference: there, the dynamic viscosity is about 1 cP and the kinematic viscosity is about 1 cSt.
Hertz (1939), operations research scholar known for pioneering the Monte Carlo methods in finance Victor Wouk (1939), pioneer in the development of electric and hybrid vehicles Julius Ashkin (1940), nuclear physicist, brother of Arthur Ashkin '47 Jeremiah Stamler (1940), epidemiologist, expert in the field of preventive cardiology, professor emeritus at Northwestern University Ulrich P. Strauss (1941), chemist at Rutgers University, 1971 Guggenheim Fellow Bruce Wallace (1941), geneticist, professor at Virginia Tech Robert S. Wallerstein (1941), psychoanalyst and former president of the International Psychoanalytical Association and director of the Langley Porter Psychiatric Institute, brother of political scientist Immanuel Wallerstein '51 Kimball Chase Atwood III (1942), geneticist, professor at Columbia University Medical School Leon Davidson (1942), chemical engineer known for his work in the Manhattan Project and the study of Unidentified Flying Objects Karl Koopman (1943), chiropterologist and curator at the American Museum of Natural History Robert G.
Retinopathy of prematurity is a condition that occurs in premature babies. In premature babies, the retina has not completely vascularized. Rather than continuing in the normal in utero fashion, the vascularization of the retina is disrupted, leading to an abnormal proliferation of blood vessels between the areas of vascularized and avascular retina. These blood vessels grow in abnormal ways and can invade into the vitreous humor, where they can hemorrhage or cause retinal detachment in neonates.
=== Cactus Club Cafe === Cactus Club Cafe is a chain of premium casual restaurants founded by Richard Jaffray and Scott Morison in Vancouver in 1988. Currently 31 restaurants are operated across Canada. As of 2022 "After 34 years, Richard Jaffray stepped aside as an owner and executive of Cactus Club Cafe, the restaurant chain he co-founded. The Fuller family, who have been silent partners since the company began, will become full owners." The Fuller family also owns Earls, Joey's, Cactus Club and Saltlik Steakhouse.
is the fracture stress for the bulk material. These models demonstrate that the bulk material selection can drastically impact the mechanical response of freeze casted structures under stress. Other microstructural features such as the lamellar thickness, pore morphology and degree of macroporosity can also heavily influence the compressive strength and Young's modulus of these highly anisotropic structures.
Sources: en.wikipedia.org
=== After WWII === After World War II, research tools and technologies of another level appeared. Thanks to these technologies, it became understandable what really occurs inside cells and between them (for example, the model of the DNA double helix was created in 1953). At the same time, changed ethical norms did not allow cardinal experiments to be performed on humans, as had been possible in previous decades. Consequently, the influence of different factors could be estimated only indirectly.
== Properties == An Affibody molecule consists of three alpha helices with 58 amino acids and has a molar mass of about 6 kDa. A monoclonal antibody, for comparison, is 150 kDa, and a single-domain antibody, the smallest type of antigen-binding antibody fragment, 12–15 kDa. Affibody molecules have been shown to withstand high temperatures (90 °C (194 °F)) or acidic and alkaline conditions (pH 2.5 or pH 11, respectively). Affibody molecules have ashort plasma half-life because of their small size.While this is advantageous for imaging,as the unbound tracer is rapidly cleared from the bloodstream, a longer plasma half-life is generally preferred for therapeutic applications. One approach to extend the plasma half-life of small molecules, such as affibody molecules,is to link them to an albumin-binding domain (ABD). A highly effective ABD is the 46-amino acid G148-GA3 domain, which is derived from streptococcal protein G, along with its engineered variant ABD035. This version has a strong femtomolar affinity for human serum albumin (HSA) [28]. The ABD can help prolong the serum half-life by forming a complex with serum albumin (SA) in the bloodstream, increasing the size of the complex and preventing it from being filtered by the kidneys. Binders with an affinity of down to sub-nanomolar have been obtained from native library selections, and binders with picomolar affinity have been obtained following affinity maturation. Affibody molecules conjugated to weak electrophiles bind their targets covalently.
Vulvar organs and tissues can become affected by different infectious agents such as bacteria and viruses, or infested by parasites such as lice and mites. Over thirty types of pathogen can be sexually transmitted, and many of these affect the genitals. Most STIs do not produce symptoms or symptoms may be mild and not be indicative of an STI. The practice of safe sex can greatly reduce the risk of infection from many sexually transmitted pathogens. The use of condoms (either male or female condoms) is one of the most effective methods of protection. Bacterial infections include: chancroid – characterised by genital ulcers known as chancres; granuloma inguinale showing as inflammatory granulomas often described as nodules; syphilis –the primary stage classically presents with a single chancre, a firm, painless, non-itchy ulcer, but there may be multiple sores; and gonorrhea that very often presents no symptoms but can result in discharge. Viral infections include human papillomavirus infection (HPV) – this is the most common STI and has many types. Genital HPV can cause genital warts. There have been links made between HPV and vulvar cancer, though HPV most often causes cervical cancer. Genital herpes is mostly asymptomatic but can present with small blisters that break open into ulcers. HIV/AIDS is mostly transmitted through sexual activity, and the vulva in some cases can be affected by sores. A highly contagious viral infection is molluscum contagiosum, which is transmissible on close contact and causes water warts.
From May 1991 to the end of the year, the EPRDF is suspected to have committed dozens of summary executions despite the government's lack of information surrounding state-sanctioned executions. The 1992 elections for 14 new regional assemblies were widely criticized by international observers who asserted that instances of fraud and the arrests of opposition leaders rendered the elections' results, which overwhelmingly favored the EPRDF, meaningless. For instance, in many cases, candidates representing the All-Amhara People's Organization were prevented from registering themselves in various constituencies. Similarly, candidates representing the Oromo Liberation Front (OLF) were threatened, harassed, and detained by the EPRDF. Despite a law that lifted nearly all of the censorship restrictions enacted by the PDRE, much of the media was still controlled by the government and many journalists were still reluctant to risk challenging the TGE or raising awareness of the regime's abuses. Later, the TGE created a Special Prosecutor's Office to begin investigating government personnel associated with the previous regime or Mengistu's Worker's Party of Ethiopia, deciding to formally suspend habeas corpus from August 1992 to the end of the year. By the end of the year, however, none of the detainees had been charged with any crimes.
=== Corporate negligence === This point of view argues that management (and to some extent, local government) underinvested in safety, which allowed for a dangerous working environment to develop. Factors cited include the filling of the MIC tanks beyond recommended levels, poor maintenance after the plant ceased MIC production at the end of 1984, allowing several safety systems to be inoperable due to poor maintenance, and switching off safety systems to save money— including the MIC tank refrigeration system which could have mitigated the disaster severity, and non-existent catastrophe management plans. Other factors identified by government inquiries included undersized safety devices and the dependence on manual operations. Specific plant management deficiencies that were identified include the lack of skilled operators, reduction of safety management, insufficient maintenance, and inadequate emergency action plans.
Sources: en.wikipedia.org
The solid is typically held cold and dry, and solutions are kept for shorter periods because hydrolysis proceeds in water. Repeated freeze-thaw cycles are usually avoided, since they can degrade both the peptide and the complex. Container material and headspace also affect how long a sample remains unchanged.
Copper is quantified by an elemental technique such as inductively coupled plasma mass spectrometry, not by peptide chromatography. The chromatographic result describes the peptide chain, while the elemental result describes the metal. Reporting both is what makes the stoichiometry checkable.
It normally lists the analytical methods used, the measured purity, the appearance, and any residuals or counterions detected. It is a statement about a specific batch rather than a general property of the material. Independent testing is still needed when results must be traceable to a reference standard.
Dry powder is typically stored frozen at −20 °C or lower, protected from moisture and light. Short-term working amounts may be kept refrigerated. Avoiding repeated temperature changes helps preserve the material.