The short version of freeze-thaw cycle fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-11-29 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Physical state | Blue-violet solid | Typically supplied as lyophilized powder |
| Storage temperature | −20 °C or below | Desiccated, protected from light |
| Working stability | Hours to days at 2–8 °C | Depends on concentration and buffer |
| Identity test | RP-HPLC with UV-Vis | Visible absorbance near 600–630 nm |
| Copper assay | ICP-MS or AAS | Metal content confirms stoichiometry |
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.
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.
== Function == Following binding of GnRH, the GnRHR associates with G-proteins that activate a phosphatidylinositol (PtdIns)-calcium second messenger system. Activation of the GnRHR ultimately causes the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH).
== External links == The idea of antiangiogenesis was pioneered by Dr. Judah Folkman. See [1] and [2] Angiogenesis Inhibitors for Cancer – from The Angiogenesis Foundation, 23 June 2009 Angiogenesis Inhibitors for Eye Disease – from The Angiogenesis Foundation, 23 June 2009 Angiogenesis Inhibitors in the Treatment of Cancer – from the National Cancer Institute Angiogenesis+Inhibitors at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
== Membership == After passage of the Eighteenth Constitutional Amendment in April 2010, it is mandatory for the Council to meet at least once in ninety days. Membership of the CCI consists of the following:
=== Orthologs === The ortholog space of C3orf62 is fairly narrow, with the majority of orthologs found in mammals. A small fraction of orthologs have also been found in the following classes: Reptila, Sarcopterygii, and Actinoptergii. The groupings of nearly all Mammalia ortholog sequences of C3orf62 are as follows: E-value: 2e-94 to 1e-169; similarity 56-84%. Mammals in this group consist largely of primates but also include the following orders: Perissodactyla, Rodentia, Carnivora, Proboscidea, Cetartiodactyla, Cingulata, Artiodactyla, Eulipotyphla, Diselphimorphia, and Afrosoricida. More distantly related ortholog sequences of C3orf62 include organisms from classes Reptilia, Sarcopterygii, and Actinopterygii ranging from an E-value of 8e-10 to 3e-59 with similarity of 24-39%. Organisms in this grouping consist of Testudines, Coelacanthiformes, Squamata, and Osteoglossiformes orders. No ortholog sequences of C3orf62 were found for the following life forms: Bacteria, archaea, protist, plant, fungus, trichoplax, invertebrate, amphibian, or bird.
The Bergmann degradation is a series of chemical reactions designed to remove a single amino acid from the carboxylic acid (C-terminal) end of a peptide. First demonstrated by Max Bergmann in 1934, it is a rarely used method for sequencing peptides. The later developed Edman degradation is an improvement upon the Bergmann degradation, instead cleaving the N-terminal amino acid of peptides to produce a hydantoin containing the desired amino acid. The Bergmann degradation follows the earlier work of Bergmann and his close colleague Leonidas Zervas, combining the organic azide degradation of the Curtius rearrangement with the Bergmann-Zervas carbobenzoxy method, which they designed to occur under relatively mild conditions so as to allow peptide sequencing. A single round of the Bergmann degradation yields an aldehyde containing the sought after amino acid residue and the remaining fragment of the original peptide in amide form.
Sources: en.wikipedia.org
The coding region of HROB consists of 2699 base pairs and encodes for a protein that is 647 amino acids long. Per NCBI AceView, the transcription of HROB produces nine alternatively spliced mRNAs and 17 distinct gt-ag introns Of these nine alternatively spliced variants four distinct protein products are formed. The molecular weight of HROB is 69 kilodaltons. The isoelectric point is 5.85. The protein sequence of HROB is both Proline and Glutamine rich, while low in Tyrosine. Aside from Proline, Glutamine, and Tyrosine, there exists a relatively even distribution of amino acids in the protein product of HROB. The protein product of HROB has been shown to target the nucleus, with minor localization in the cytoplasm. MCM8, MCM9 — HROB interacts with the MCM8-MCM9 helicase complex, which is involved in DNA repair. In particular, it helps recruit the complex to areas of damaged DNA. RPA1 — HROB interacts with the heterotrimeric RPA complex via its interaction with RPA1. This complex helps stabilize DNA while it’s being repaired.
Motilin is a 22-amino acid polypeptide hormone in the motilin family that, in humans, is encoded by the MLN gene. Motilin is secreted by endocrine Mo cells (also referred to as M cells, which are not the same as the M cells, or microfold cells, found in Peyer's patches) that are numerous in crypts of the small intestine, especially in the duodenum and jejunum. It is released into the general circulation in humans at about 100-min intervals during the inter-digestive state and is the most important factor in controlling the inter-digestive migrating contractions; and it also stimulates endogenous release of the endocrine pancreas. Based on amino acid sequence, motilin is unrelated to other hormones. Because of its ability to stimulate gastric activity, it was named "motilin." Apart from in humans, the motilin receptor has been identified in the gastrointestinal tracts of pigs, rats, cows, and cats, and in the central nervous system of rabbits.
CKLF-like MARVEL transmembrane domain-containing 5 (CMTM5), previously termed chemokine-like factor superfamily 5 (i.e. CKLFSF5), designates any one of the six protein isoforms (termed CMTM5-v1 to CMTM5-v6) encoded by six different alternative splices of its gene, CMTM5; CMTM5-v1 is the most studied of these isoforms. The CMTM5 gene is located in band 11.2 on the long (i.e. "q") arm of chromosome 14. The CMTM5 isoforms are members of the CKLF-like MARVEL transmembrane domain-containing family (CMTM). This family consists of 9 proteins although most of them are known to have one or more isoforms. These proteins are: chemokine-like factor (i.e. CLF, the founding member of the family) and CEF-like marvel transmembrane domain-containing 1 through 8 (i.e. CMTM1 through CMTM8). All of these proteins as well as the genes responsible for their production (i.e. CKLF and CMTM1 to CMTM8, respectively) have similar structures but vary in their apparent physiological and pathological functions. Preliminary studies suggest that CMTM5-v1 (which cells commonly secrete to the extracellular spaces such as the blood) or an unspecified CMTM5 isoform has various functions including involvements in regulating the autoimmune system, the development of numerous types of cancers, and the cardiovascular system.
21. Adv Gerontol. 2011;24(1):38-42. [Characteristics of the pineal gland and thymus relationship in aging]. [Article in Russian] Lin'kova NS, Poliakova VO, Kvetnoĭ IM, Trofimov AV, Sevost'ianova NN. The review presents the interference between thymus and pineal gland during their involution. The research data of thymus peptides influence on pineal gland and pineal peptides on thymus are summarized. Analysis of these data showed that pineal peptides (Epithalamin, Epitalon) had more effective geroprotective effect on thymus involution in comparison with geroprotective effect of thymic peptides (Thymalin, Thymogen) on involution of pineal gland. The key mechanisms of pineal peptides effect on thymus dystrophy is immunoendocrine cooperation, which is realized as transcription's activation of various proteins.
Sources: en.wikipedia.org
== Distribution == The labeled [18F]FDG compound has a relatively short shelf life which is determined largely by the physical decay of fluorine-18 with a half-life of 109.8 minutes, or slightly less than two hours. Still, this half-life is sufficiently long to allow shipping the compound to remote PET scanning facilities, in contrast to other medical radioisotopes like carbon-11 with a half-life of ~20 minutes. Due to transport regulations for radioactive compounds, delivery is normally done by specially licensed road transport, but means of transport may also include dedicated small commercial jet services. Transport by air allows expanding the distribution area around a [18F]FDG production site to deliver the compound to PET scanning centres within a 1–3-hour flight time. Recently, on-site cyclotrons with integral shielding and portable chemistry stations for making [18F]FDG have accompanied PET scanners to remote hospitals. This technology holds some promise in the future, for replacing some of the scramble to transport [18F]FDG from site of manufacture to site of use.
== Metabolism in the opium poppy == In Papaver somniferum, there are two possible pathways to morphine from thebaine. These differ according to which methyl group in thebaine is first to be removed in an oxidation reaction.
== Legacy == The name continues in use as a geographical and cultural term, and it survives in Cumberland sausages; HMS Cumberland; the Cumberland Fell Runners Club; the Cumberland Athletics Club; and various organisations and companies, such as the local newspapers The Cumberland News, and The West Cumberland Times and Star, and the Cumberland Building Society. It is also mentioned in Macbeth as the kingdom given to Prince Malcolm, and is also the initial setting for the Geoffrey Trease historical novel Cue for Treason. In June 1994, during the 1990s UK local government reform, the Local Government Commission published draft recommendations, suggesting as one option a North Cumbria unitary authority (also including Appleby, the historic county town of Westmorland). It also suggested that Cumberland could be reinstated as an independent ceremonial county. The final recommendations, published in October 1994, did not include such recommendations, apparently due to lack of expression of support for the proposal to the commission. The Grass-of-Parnassus was the county flower. It had been associated with the county since 1951, when it was included in the coat of arms granted to the Cumberland County Council. It subsequently featured in the arms granted to Cumbria County Council and Copeland Borough Council, in both cases to represent Cumberland. The flower was also attributed to Cumbria in 2002 as part of a national County flowers of the United Kingdom campaign by the charity Plantlife.
Transgenic mice, with foreign genes inserted into their genome: Abnormally large mice, with an inserted rat growth hormone gene Oncomice, with an activated oncogene, so as to significantly increase the incidence of cancer Doogie mice, with enhanced NMDA receptor function, resulting in improved memory and learning Knockout mice, where a specific gene was made inoperable by a technique known as gene knockout: the purpose is to study the function of the gene's product or to simulate a human disease Obese mice, prone to obesity due to a carboxypeptidase E deficiency Strong muscular mice, with a disabled myostatin gene, nicknamed "mighty mice". Since 1998, it has been possible to clone mice from cells derived from adult animals.
Cysteine-rich proteins (CRP, cysteine-rich peptide or disulphide-rich peptide) are small proteins that contain a large number of cysteines. These cysteines either cross-link to form disulphide bonds, or bind metal ions by chelation, stabilising the protein's tertiary structure. CRPs include a highly conserved secretion peptide signal at the N-terminus and a cysteine-rich region at the C-terminus.
Sources: en.wikipedia.org
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.
Reversed-phase HPLC with UV-visible detection is common because the copper complex absorbs visible light. Mass spectrometry provides molecular mass confirmation. Copper-specific methods such as ICP-MS quantify the metal content.
The blue color comes from copper-ligand interactions. Displacement of copper by chelators or changes in pH can shift or diminish the color. Such changes often indicate that the complex has been altered.
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.