imidazole coordination is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-04-13. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide backbone consists of glycine, histidine, and lysine joined in that order. Copper is held through the imidazole nitrogen of histidine and the alpha-amino group at the N-terminus, which together produce a square-planar arrangement around the metal center. The solid appears blue to violet, a color that originates from d-d electronic transitions within the copper coordination sphere. The complex is indexed under CAS number 89030-95-5.
The sequence now called GHK was first reported in the early 1970s after isolation from human plasma, where it was noted to influence liver cell behavior in laboratory preparations. Later work described a copper-binding form and its activity in fibroblast and wound-model experiments. Review articles frequently group the substance with other copper peptides. Concentrations in blood appear to fall with age in several small surveys, although the reason for this trend is not settled. Whether such a decline carries functional consequences remains an open question.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C | Dry, protected from light |
| Appearance in solution | Blue | Tone varies with pH and concentration |
| Primary analytical method | LC-MS with ICP-MS | Identity plus copper content |
| pH sensitivity | Higher near neutral and above | Alkaline conditions can degrade it |
| Common supplied form | Freeze-dried solid | Dissolved before use |
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 usually assessed with reversed-phase high-performance liquid chromatography, often paired with mass spectrometry. Copper content is measured separately by techniques such as inductively coupled plasma mass spectrometry or atomic absorption. Amino acid analysis confirms the peptide sequence after hydrolysis. Because the metal and the peptide can be quantified independently, a complete certificate of analysis normally reports both values rather than a single purity figure. This separation of measurements is important when comparing suppliers.
Solid GHK-Cu appears as a blue to blue-violet powder, and the colour is a direct consequence of copper coordination. The complex dissolves readily in water and in many polar solvents, while the free peptide behaves differently. Solubility in nonpolar media is low, which limits its use in oil-based systems. Solutions are typically prepared fresh because the dissolved form is more exposed to hydrolysis and to loss of the metal ion than the dry powder. Working concentrations are usually low, and preparation notes often specify the solvent and the order of addition.
Dry material is typically held at low temperature, often around minus twenty degrees Celsius, and protected from moisture and light. Copper complexes can release their metal ion under acidic conditions or in the presence of competing chelators. Hydrolysis of the peptide backbone is a slower but real pathway, and the histidine residue is susceptible to oxidation over long periods. Stability statements therefore depend on formulation, pH, and container, and they should be read as conditional rather than absolute.
These models tend to recognize partial molecular structures early in training but require significantly longer to accurately distinguish between enantiomers, sometimes exhibiting periods of confusion where @ and @@ tokens are frequently interchanged. The interpretability of neural network-based descriptors is often limited compared to traditional physically-motivated descriptors. Additionally, these methods typically perform best for compounds structurally similar to training data and may not generalize well to novel scaffolds or unusual stereochemical arrangements.
=== Fuselage === Circular-section structure of frames and stringers with a continuous main deck and lower decks fore and aft of the centre section. Rectangular windows in most interframe bays, eight ICAO Type 1a passenger doors on the main deck and three more on the lower deck portside; two freight hold doors and a galley supply door on the lower deck starboard. The main deck houses the flightdeck, two wardrobes, eight toilets, two pantries and a three-section passenger cabin. The lower deck houses three entry vestibules/luggage stores with hydraulic boarding stairs to ground level and fixed stairs to the main deck, a midships galley linked with the main deck by an electric lift, two freight holds (fore and aft of the passenger facilities), an avionics bay and two technical bays. The entire accommodation is pressurised and air-conditioned with "earphones for music or on-board cinema."
== Biosynthesis == After translation, the AGP protein backbones are highly decorated with complex carbohydrates, primarily type II AG polysaccharides. The biosynthesis of the mature AGP involves cleavage of the signal peptide at the N-terminus, hydroxylation on the P residues and subsequent glycosylation and in many cases addition of a GPI-anchor.
Sources: en.wikipedia.org
Glutaredoxins (also known as Thioltransferase) are small redox enzymes of approximately one hundred amino-acid residues that use glutathione as a cofactor. In humans this oxidation repair enzyme is also known to participate in many cellular functions, including redox signaling and regulation of glucose metabolism. Glutaredoxins are oxidized by substrates, and reduced non-enzymatically by glutathione. In contrast to thioredoxins, which are reduced by thioredoxin reductase, no oxidoreductase exists that specifically reduces glutaredoxins. Instead, glutaredoxins are reduced by the oxidation of glutathione. Reduced glutathione is then regenerated by glutathione reductase. Together these components compose the glutathione system. Like thioredoxin, which functions in a similar way, glutaredoxin possesses an active centre disulfide bond. It exists in either a reduced or an oxidized form where the two cysteine residues are linked in an intramolecular disulfide bond. Glutaredoxins function as electron carriers in the glutathione-dependent synthesis of deoxyribonucleotides by the enzyme ribonucleotide reductase. Moreover, GRX act in antioxidant defense by reducing dehydroascorbate, peroxiredoxins, and methionine sulfoxide reductase. Beside their function in antioxidant defense, bacterial and plant GRX were shown to bind iron-sulfur clusters and to deliver the cluster to enzymes on demand.
=== The term chemotherapy === The word chemotherapy without a modifier usually refers to cancer treatment, but its historical meaning was broader. The term was coined in the early 1900s by Paul Ehrlich as meaning any use of chemicals to treat any disease (chemo- + -therapy), such as the use of antibiotics (antibacterial chemotherapy). Ehrlich was not optimistic that effective chemotherapy drugs would be found for the treatment of cancer. The first modern chemotherapeutic agent was arsphenamine, an arsenic compound discovered in 1907 and used to treat syphilis. This was later followed by sulfonamides (sulfa drugs) and penicillin. In today's usage, the sense "any treatment of disease with drugs" is often expressed with the word pharmacotherapy.
== History == The Penning trap was named after F. M. Penning (1894–1953) by Hans Georg Dehmelt (1922–2017) who built the first trap. Dehmelt got inspiration from the vacuum gauge built by F. M. Penning where a current through a discharge tube in a magnetic field is proportional to the pressure. Citing from H. Dehmelt's autobiography: "I began to focus on the magnetron/Penning discharge geometry, which, in the Penning ion gauge, had caught my interest already at Göttingen and at Duke. In their 1955 cyclotron resonance work on photoelectrons in vacuum Franken and Liebes had reported undesirable frequency shifts caused by accidental electron trapping. Their analysis made me realize that in a pure electric quadrupole field the shift would not depend on the location of the electron in the trap. This is an important advantage over many other traps that I decided to exploit. A magnetron trap of this type had been briefly discussed in J.R. Pierce's 1949 book, and I developed a simple description of the axial, magnetron, and cyclotron motions of an electron in it. With the help of the expert glassblower of the Department, Jake Jonson, I built my first high vacuum magnetron trap in 1959 and was soon able to trap electrons for about 10 sec and to detect axial, magnetron and cyclotron resonances." – H. Dehmelt
=== Secondary packaging === Secondary packaging contains a number of primary packages into one box, being made usually out of corrugated cardboard. Thus, the secondary level is a physical distribution carrier for the primary packages, making them more easy to handle during transportation. Occasionally, it can be used as an aid in retail outlets or supermarkets for the display of basic goods.
Sources: en.wikipedia.org
Dracaena cinnabari, the Socotra dragon tree, or dragon blood tree, is a dragon tree native to the Socotra archipelago, part of Yemen, located in the Arabian Sea. It is named after the blood-like color of the red sap that the trees produce. It is also the national tree of Yemen.
Fishing scenes are rarely represented in ancient Greek culture, a reflection of the low social status of fishing. However, Oppian of Corycus, a Greek author wrote a major treatise on sea fishing, the Halieulica or Halieutika, composed between 177 and 180. This is the earliest such work to have survived to the modern day. The consumption of fish varied by the wealth and location of the household. In the Greek islands and on the coast, fresh fish and seafood (squid, octopus, and shellfish) were common. They were eaten locally but more often transported inland. Sardines and anchovies were regular fare for the citizens of Athens. They were sometimes sold fresh, but more frequently salted. A stele of the late 3rd century BCE from the small Boeotian city of Akraiphia, on Lake Copais, provides us with a list of fish prices. The cheapest was skaren (probably parrotfish) whereas Atlantic bluefin tuna was three times as expensive. Common salt water fish were yellowfin tuna, red mullet, ray, swordfish, or sturgeon, a delicacy that was eaten salted. Lake Copais itself was famous in all of Greece for its eels, celebrated by the hero of The Acharnians. Other freshwater fish were pike fish, carp, and the less appreciated catfish. Pictorial evidence of Roman fishing comes from mosaics. At a certain time, the goatfish was considered the epitome of luxury, above all because its scales exhibit a bright red colour when it dies out of water. For this reason, these fish were occasionally allowed to die slowly at the table.
==== Respiratory syncytial virus (Human orthopneumovirus) ==== Sendai virus was also used as a backbone for vaccine against respiratory syncytial virus (HRSV). This virus (HRSV), is a major cause of lower respiratory tract infections and hospital visits during infancy and childhood. It was shown that administration of SeV-based RSV vaccine protects cotton rats and African green monkeys from this viral infection. The HRSV phase I clinical trial was completed in adults. It demonstrated high safety of the SeV-based construct that expressed HRSV envelope F glycoprotein.
=== Legal status in the United States === The US government imposed tougher prescribing rules for hydrocodone in 2014, changing the drug from Schedule III to Schedule II. In 2011, hydrocodone products were involved in around 100,000 abuse-related emergency department visits in the United States, more than double the number in 2004.
== Structure == The core of the signal peptide contains a long stretch of hydrophobic amino acids (about 5–16 residues long) that has a tendency to form a single alpha-helix and is also referred to as the "h-region". In addition, many signal peptides begin with a short positively charged stretch of amino acids, which may help to enforce proper topology of the polypeptide during translocation by what is known as the positive-inside rule. Because of its close location to the N-terminus it is called the "n-region". At the end of the signal peptide there is typically a stretch of amino acids that is recognized and cleaved by signal peptidase and therefore named cleavage site. This cleavage site is absent from transmembrane-domains that serve as signal peptides, which are sometimes referred to as signal anchor sequences. Signal peptidase may cleave either during or after completion of translocation to generate a free signal peptide and a mature protein. The free signal peptides are then digested by specific proteases. Moreover, different target locations are aimed by different types of signal peptides. For example, the structure of a target peptide aiming for the mitochondrial environment differs in terms of length and shows an alternating pattern of small positively charged and hydrophobic stretches. Nucleus-targeting signal peptides can be found at both the N-terminus and the C-terminus of a protein and are in most cases retained in the mature protein.
Sources: en.wikipedia.org
Freezer temperatures are common for long-term retention. Light and moisture exposure should be limited. Working portions are best kept cold and used without repeated freeze-thaw cycles.
Sequence assays confirm the amino acids but say nothing about the metal. Copper content links the peptide to the ion that defines the complex. An elemental technique is used for this step.
No. Several copper species and degraded mixtures can also look blue. Confirmation needs both separation data and elemental data.
It is the copper complex of the tripeptide glycyl-L-histidyl-lysine. The metal ion is held by the histidine imidazole group and the peptide N-terminus. Most research on it concerns skin and wound models.