Everything below concerns redox activity. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-01-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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 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 |
|---|---|---|
| Molecular formula | C14H24N6O4 | Free tripeptide, without copper |
| Molecular weight | About 340 g/mol | Peptide portion only |
| Appearance | Blue to violet powder | Color from copper coordination |
| Solubility | Soluble in water | pH influences dissolution |
| Common synonyms | Copper tripeptide-1, Cu-GHK | Seen on ingredient labels |
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.
The sequence carries three residues in the order glycine, histidine, lysine, which places a small, flexible chain around a single metal centre. Compared with larger copper-binding proteins, the complex is compact and its coordination chemistry can be reproduced with synthetic peptide in a laboratory. Published structural work agrees on the nitrogen donor set but differs in the exact geometry assigned under some conditions, so the arrangement is best treated as well characterised in outline rather than fixed in every detail.
Published work on GHK-Cu is dominated by in vitro experiments and small animal studies. Human trials tend to be short and small, with endpoints such as skin appearance rather than clinical outcomes. Review articles often summarize the same underlying laboratory findings, which can make the evidence base look broader than it is. Several basic questions remain open: the concentration of the intact complex in human tissue, the route by which it crosses the skin barrier, and whether effects seen in culture produce measurable changes in people.
Laboratory studies describe GHK-Cu as a source of copper that cells can take up, with reported effects on collagen, elastin, and glycosaminoglycan synthesis in cultured fibroblasts. The peptide also appears in wound-repair research, where it is linked to the activity of matrix metalloproteinases and their inhibitors. These observations come largely from cell and animal models. How directly the complex controls any single pathway in intact human skin remains an open question, and reported effects depend on concentration, vehicle, and exposure time.
Copper takes part in redox chemistry, and the same property that makes it useful in enzymes can generate reactive oxygen species when the ion is loosely bound. GHK chelates copper through imidazole, amino, and amide nitrogen donors, which reduces the amount of free copper in solution. Whether that chelation is protective, neutral, or harmful in a given tissue is not settled. Laboratory assays report both antioxidant and pro-oxidant behavior, depending on the conditions and the readout used.
Copper content is measured separately, since a peptide assay alone does not report the metal-to-peptide ratio. Elemental techniques such as inductively coupled plasma optical emission spectroscopy quantify copper after acid digestion of the sample. The result is compared with the theoretical value for a one-to-one complex, and a shortfall indicates free peptide or partial dissociation. Suppliers differ in how they state purity, as some quote peptide content and others quote the whole complex. A defined stoichiometry therefore requires both a peptide assay and a copper assay.
Solid GHK-Cu is usually supplied as a lyophilized powder and is kept cold and dry. Moisture, light, and repeated temperature cycling shorten its useful life in the laboratory. In aqueous solution the complex undergoes slow hydrolysis of the peptide backbone and gradual loss of coordinated copper. Buffers containing strong chelators, such as EDTA, compete for the metal and strip it from the peptide. Working solutions are therefore prepared shortly before use, and leftover liquid is not returned to the stock container.
Fifty years after the introduction of fluoxetine and other SSRIs, these drugs remain widely used and effective for depression. Concerns about over prescription, under-treatment of depression through other modalities, and role in the over-medicalization of normal life remain debated.
Before the widespread use of a vaccine against measles, rates of disease were so high that infection was felt to be "as inevitable as death and taxes." Reported cases of measles in the United States fell from hundreds of thousands to tens of thousands per year following introduction of the vaccine in 1963. Increasing uptake of the vaccine following outbreaks in 1971, and 1977, brought this down to thousands of cases per year in the 1980s. An outbreak of almost 30,000 cases in 1990 led to a renewed push for vaccination and the addition of a second vaccine to the recommended schedule. Fewer than 200 cases have been reported in the US each year between 1997 and 2013, and the disease is no longer considered endemic there. The benefit of measles vaccination in preventing illness, disability, and death has been well documented. The first 20 years of licensed measles vaccination in the US prevented an estimated 52 million cases of the disease, 17,400 cases of intellectual disability, and 5,200 deaths. During 1999–2004, a strategy led by the World Health Organization and UNICEF led to improvements in measles vaccination coverage that averted an estimated 1.4 million measles deaths worldwide. Between 2000 and 2018, measles vaccination resulted in a 73% decrease in deaths from the disease. Measles is common in many areas of the world. Although it was declared eliminated from the US in 2000, high rates of vaccination and good communication with people who refuse vaccination are needed to prevent outbreaks and sustain the elimination of measles in the US.
In order for the acyl-CoA to enter the mitochondrion the carnitine shuttle is used: Acyl-CoA is transferred to the hydroxyl group of carnitine by carnitine palmitoyltransferase I, located on the cytosolic faces of the outer and inner mitochondrial membranes. Acyl-carnitine is shuttled inside by a carnitine-acylcarnitine translocase, as a carnitine is shuttled outside. Acyl-carnitine is converted back to acyl-CoA by carnitine palmitoyltransferase II, located on the interior face of the inner mitochondrial membrane. The liberated carnitine is shuttled back to the cytosol, as an acyl-CoA is shuttled into the mitochondrial matrix. Beta oxidation, in the mitochondrial matrix, then cuts the long carbon chains of the fatty acids (in the form of acyl-CoA molecules) into a series of two-carbon (acetate) units, which, combined with co-enzyme A, form molecules of acetyl CoA, which condense with oxaloacetate to form citrate at the "beginning" of the citric acid cycle. It is convenient to think of this reaction as marking the "starting point" of the cycle, as this is when fuel - acetyl-CoA - is added to the cycle, which will be dissipated as CO2 and H2O with the release of a substantial quantity of energy captured in the form of ATP, during the course of each turn of the cycle and subsequent oxidative phosphorylation.
Sources: en.wikipedia.org
=== Water treatment === Scale deposition in boilers can reduce heat transfer efficiency and increase energy consumption. Antiscalants are added to boiler feedwater to prevent scale formation on heat transfer surfaces, piping, and other boiler components. Water treatment plants can use antiscalants to maintain filtration.
== Experiments with argiotoxins == Argiotoxins studies have been particularly made to discover the relation between inhibition, receptors, and ionic channels. Researchers have specifically pursued the blocking of receptors on invertebrates, rather than on vertebrates. Referring to invertebrates, Planorbarius corneus is a mollusc involved in one of the many ionic experiments. To begin with, neurons of molluscan pedal ganglia were isolated and transferred to a special chamber with saline solution and regulated temperature. Then, the observation was based on routine voltage clamp technique. Electrical measurements were obtained from the evaluation of neurons response to various substances (argiopines). In addition to that, crayfish, a freshwater crustacean, has followed a similar protocol to this study. In this case, the analysis was made of the stomach muscles and using the patch clamp technique. The research findings were obtained taking into account the bursts of openings of excitatory channels. Other experiments use spectroscopy in order to analyse and differentiate these molecules. HPLC, mass spectrometry, UV data and amino acid analysis are the elements that allow identifying diverse argiotoxins due to their spectrum. Argiope lobata toxins (Arg 636, Arg 630, Arg 658, Arg 744, Arg 759, Arg 373, Arg 728, Arg 723, ...) show a close similarity in their structures; the subtle differences between them are chemical points, such as N-methyl groups, molecular masses or lysine residues that are determined in a certain position in their structure.
=== Polymers and coatings === IGC has been used extensively for the characterization of polymer films, beads, and powders. For instance, IGC was used to study surface properties and interactions amongst components in paint formulations. Also, IGC has been used to investigate the degree of crosslinking for ethylene propylene rubber using the Flory–Rehner equation [17]. Additionally, IGC is a sensitive technique for the detection and determination of first and second order phase transitions like melting and glass transition temperatures of polymers. Although other techniques like differential scanning calorimetry are capable of measuring these transition temperatures, IGC has the capability of glass transition temperatures as a function of relative humidity.
Great Britain, Ireland, Germany, the Netherlands, Sweden, and Denmark have produced a number of bog bodies, mummies of people deposited in sphagnum bogs, apparently as a result of murder or ritual sacrifices. In such cases, the acidity of the water, low temperature and lack of oxygen combined to tan the body's skin and soft tissues. The skeleton typically disintegrates over time. Such mummies are remarkably well preserved on emerging from the bog, with skin and internal organs intact; it is even possible to determine the decedent's last meal by examining stomach contents. The Haraldskær Woman was discovered by labourers in a bog in Jutland in 1835. She was erroneously identified as an early medieval Danish queen, and for that reason was placed in a royal sarcophagus at the Saint Nicolai Church, Vejle, where she currently remains. Another bog body, also from Denmark, known as the Tollund Man was discovered in 1950. The corpse was noted for its excellent preservation of the face and feet, which appeared as if the man had recently died. Only the head of Tollund Man remains, due to the decomposition of the rest of his body, which was not preserved along with the head.
Sources: en.wikipedia.org
=== Metabolism === The metabolism of progesterone is rapid and extensive, and it occurs mainly in the liver, though enzymes that metabolize progesterone are also expressed widely in the brain, skin, and various other extrahepatic tissues. Progesterone has an elimination half-life of only approximately five minutes in circulation. The metabolism of progesterone is complex, and it may form as many as 35 different unconjugated metabolites when it is ingested orally. Progesterone is highly susceptible to enzymatic reduction via reductases and hydroxysteroid dehydrogenases because of its double bond (between the C4 and C5 positions) and its two ketones (at the C3 and C20 positions). The major metabolic pathway of progesterone is reduction by 5α-reductase and 5β-reductase, into the dihydrogenated 5α-dihydroprogesterone and 5β-dihydroprogesterone, respectively. This is followed by the further reduction of these metabolites via 3α-hydroxysteroid dehydrogenase and 3β-hydroxysteroid dehydrogenase into the tetrahydrogenated allopregnanolone, pregnanolone, isopregnanolone, and epipregnanolone. Subsequently, 20α-hydroxysteroid dehydrogenase and 20β-hydroxysteroid dehydrogenase reduce these metabolites to form the corresponding hexahydrogenated pregnanediols (eight different isomers in total), which are then conjugated via glucuronidation and/or sulfation, released from the liver into circulation, and excreted by the kidneys into the urine.
=== DSF-GTP === The DSF-GTP (GFP-Tagged Protein-of-Interest) technique was developed by a team led by Patrick Schaeffer at James Cook University and published in Moreau et al. 2012. The development of differential scanning fluorimetry and the high-throughput capability of Thermofluor have vastly facilitated the screening of crystallization conditions of proteins and large mutant libraries in structural genomics programs, as well as ligands in drug discovery and functional genomics programs. These techniques are limited by their requirement for both highly purified proteins and solvatochromic dyes, prompting the need for more robust high-throughput technologies that can be used with crude protein samples. This need was met with the development of a new high-throughput technology for the quantitative determination of protein stability and ligand binding by differential scanning fluorimetry of proteins tagged with green fluorescent protein (GFP). This technology is based on the principle that a change in the proximal environment of GFP, such as unfolding and aggregation of the protein of interest, is measurable through its effect on the fluorescence of the fluorophore. The technology is simple, fast and insensitive to variations in sample volumes, and the useful temperature and pH range is 30–80 °C and 5–11 respectively. The system does not require solvatochromic dyes, reducing the risk of interferences. The protein samples are simply mixed with the test conditions in a 96-well plate and subjected to a melt-curve protocol using a real-time thermal cycler.
(1936), Recollections and Reflections, London: G. Bell & Sons, Ltd. Republished as digital edition, Cambridge: University Press, 2011 (Cambridge Library Collection series). Thomson, George Paget. (1964) J.J. Thomson: Discoverer of the Electron. Great Britain: Thomas Nelson & Sons, Ltd. Davis, Eward Arthur & Falconer, Isobel (1997), J.J. Thomson and the Discovery of the Electron. ISBN 978-0-7484-0696-8 Falconer, Isobel (1988) "J.J. Thomson's Work on Positive Rays, 1906–1914" Historical Studies in the Physical and Biological Sciences 18(2) 265–310 Falconer, Isobel (2001) "Corpuscles to Electrons" in J Buchwald and A Warwick (eds) Histories of the Electron, Cambridge, Mass: MIT Press, pp. 77–100. Navarro, Jaume (2005). "J. J. Thomson on the Nature of Matter: Corpuscles and the Continuum". Centaurus. 47 (4): 259–282. Bibcode:2005Cent...47..259N. doi:10.1111/j.1600-0498.2005.00028.x. Downard, Kevin M. (2009). "J. J. Thomson goes to America". Journal of the American Society for Mass Spectrometry. 20 (11): 1964–1973. Bibcode:2009JASMS..20.1964D. doi:10.1016/j.jasms.2009.07.008. PMID 19734055. S2CID 34371775.
Many ways and materials are available to stabilize and secure cargo in various modes of transport. Conventional load securing methods and materials such as steel strapping and plastic/wood blocking and bracing have been used for decades and are still widely used. Present load-securing methods offer several other options, including polyester strapping and lashing, synthetic webbings and dunnage bags, also known as airbags or inflatable bags. Practical advice on stabilization is given in the International Guidelines on Safe Load Securing for Road Transport.
The passion fruit (Portuguese: maracujá and Spanish: maracuyá, both from the Tupi murukuîácode: tpw is deprecated ) and granadilla is the fruit of several plants in the genus Passiflora. It is native to subtropical regions of South America from southern Brazil through Paraguay to northern Argentina. The fruit is eaten for its pulp and seeds, and as a juice. The name passion fruit derives from 18th century Christian missionaries who interpreted the flower as a religious symbol. The passion fruit spread throughout Africa, Europe, Australia, North America, and South America throughout the 1800s and 1900s.
Sources: en.wikipedia.org
It is a complex of the tripeptide glycyl-L-histidyl-L-lysine with a copper(II) ion. The peptide coordinates the metal through its histidine, amino terminus, and an amide nitrogen. It is often listed simply as copper tripeptide-1.
The peptide and its copper form have been detected in human plasma, saliva, and urine. Early reports describe levels that fall with age. The functional meaning of these pools is still debated.
Chromatographic separation gives peptide purity, often reported as a percentage. Copper content is checked by a separate elemental method. Moisture and counter-ions may be reported as well.
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.