Everything below concerns certificate of analysis. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Several names circulate for the same material, which complicates literature searches. Cosmetic ingredient lists often use copper tripeptide-1, while older biochemistry papers use glycyl-L-histidyl-lysine or its abbreviation GHK. The copper complex is sometimes written as GHK-Cu(II) to make the oxidation state explicit. Terminology is not fully standardized, so matching a compound across sources requires attention to the exact sequence, the counterion, and the stated copper content. Reviews that compare studies must account for these naming differences before drawing conclusions.
GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine, a short sequence of three amino acids. The peptide was first isolated from human plasma in 1973 during research on factors that influence tissue repair in liver. Its ability to bind copper ions became a central point of interest because the metal changes the peptide's chemistry and its behaviour in laboratory systems. Today the compound appears in cosmetic formulations, cell-culture studies, and biochemistry literature under several names.
The peptide sequence places a histidine in the middle, and this residue dominates metal binding. Copper(II) coordinates through the imidazole nitrogen of histidine and the terminal amino group, forming a stable chelate ring system. Loss of the copper ion leaves the free tripeptide, which has different solubility and reactivity. This structural detail matters because assays that measure only the peptide backbone can miss whether copper is still bound to it.
| 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 |
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.
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.
Research interest in GHK-Cu centers on its ability to deliver copper and to influence cellular processes in laboratory models. In cell culture and animal studies, the complex has been linked to collagen synthesis, antioxidant enzyme activity, and expression of genes associated with tissue remodeling. These effects are not equivalent to proven clinical outcomes. The mechanisms proposed include copper transfer to cuproenzymes, modulation of growth factor signaling, and interactions with extracellular matrix components. How much of the observed activity depends on intact GHK-Cu versus free copper or free peptide is not fully resolved.
The compound entered scientific literature in the 1970s, when plasma factors with copper-binding activity were isolated and characterized. Later work expanded into wound healing, skin biology, and cosmetic formulation, where copper tripeptide-1 became a recognized ingredient name. Most published studies remain preclinical or small-scale, and findings are often reported in specialized dermatology or peptide journals. Regulatory treatment varies: some jurisdictions allow it as a cosmetic ingredient, while research-grade material is sold for laboratory use. Questions about optimal delivery, target tissues, and long-term effects continue to be investigated rather than settled.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide sequence is often abbreviated Gly-His-Lys, and the copper is bound through the histidine imidazole nitrogen and adjacent peptide nitrogens. The complex is frequently described as a 1:1 peptide-to-copper species. It occurs naturally in human plasma, saliva, and urine at low concentrations. Its endogenous levels have been reported to decline with age, although the precise physiological role of that change remains an open question.
Donald has supervised many students and postdocs, many of whom are now professors in reputed universities such as MIT, Carnegie-Mellon University, University of Washington, Seattle, University of Massachusetts Amherst, Dartmouth College, Duke University, Middlebury College and University of Toronto, and researchers at organizations such as NIAID, NIST, IBM, Sandia National Laboratories. Donald is the son of historian David Herbert Donald and historian and editor Aida DiPace Donald. MEMS Protein design NMR Protein Structure Kinodynamic planning Donald is the author of over 100 publications. A representative selection includes:
== Caesium-133 == Caesium-133 is the only stable isotope of caesium. The SI base unit of time, the second, is defined by a specific caesium-133 transition. Since 1967, the official definition of a second is:
Compulsive overeating, or emotional eating, is "the tendency to eat in response to negative emotions". Empirical studies have indicated that anxiety leads to decreased food consumption in people with normal weight and increased food consumption in the obese. Many laboratory studies showed that overweight individuals are more emotionally reactive and are more likely to overeat when distressed than people of normal weight. Furthermore, it was consistently found that obese individuals experience negative emotions more frequently and more intensively than do normal weight persons. The naturalistic study by Lowe and Fisher compared the emotional reactivity and emotional eating of normal and overweight female college students. The study confirmed the tendency of obese individuals to overeat, but these findings applied only to snacks, not to meals. That means that obese individuals did not tend to eat more while having meals; rather, the amount of snacks they ate between meals was greater. One possible explanation that Lowe and Fisher suggest is obese individuals often eat their meals with others and do not eat more than average due to the reduction of distress because of the presence of other people. Another possible explanation would be that obese individuals do not eat more than the others while having meals due to social desirability. Conversely, snacks are usually eaten alone.
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== Health claims == By the early 2010s, "bone broth" had become a popular health food trend, due to the resurgence in popularity of dietary fat over sugar, and interest in "functional foods" to which "culinary medicinals" such as turmeric and ginger could be added. Bone broth bars, bone broth home delivery services, bone broth carts, and bone broth freezer packs grew in popularity in the United States. The fad was heightened by the 2014 book Nourishing Broth, in which authors Sally Fallon Morell and Kaayla T. Daniel claim that the broth's nutrient density has a variety of health effects. There is no scientific evidence to support many of the claims made for bone broth.
Sources: en.wikipedia.org
==== Structure ==== The myophosphorylase structure consists of 842 amino acids. The molecular weight of the unprocessed precursor is 97 kDa. The three-dimensional structure has been determined for this protein. The interactions of several amino acids in myophosphorylase's structure are known. Ser-14 is modified by phosphorylase kinase during activation of the enzyme. Lys-680 is involved in binding the pyridoxal phosphate, which is the active form of vitamin B6, a cofactor required by myophosphorylase. By similarity, other sites have been estimated: Tyr-76 binds AMP, Cys-109 and Cys-143 are involved in subunit association, and Tyr-156 may be involved in allosteric control.
== Reduced-footprint cement == Growing environmental concerns and the increasing cost of fossil fuels have resulted, in many countries, in a sharp reduction of the resources needed to produce cement, as well as effluents (dust and exhaust gases). Reduced-footprint cement is a cementitious material that meets or exceeds the functional performance capabilities of Portland cement. Various techniques are under development. One is geopolymer cement, which incorporates recycled materials, thereby reducing consumption of raw materials, water, and energy. Another approach is to reduce or eliminate the production and release of damaging pollutants and greenhouse gasses, particularly CO2. Recycling old cement in electric arc furnaces is another approach. A team at the University of Edinburgh has developed the 'DUPE' process based on the microbial activity of Sporosarcina pasteurii, a bacterium precipitating calcium carbonate, which, when mixed with sand and urine, can produce mortar blocks with a compressive strength 70% of that of concrete.
Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue) and space around the alveoli (air sacs) of the lungs. It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, and perivascular and perilymphatic tissues. It may occur when an injury to the lungs triggers an abnormal healing response. Ordinarily, the body generates just the right amount of tissue to repair damage, but in interstitial lung disease, the repair process is disrupted, and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into the bloodstream. The disease presents itself with the following symptoms: shortness of breath, nonproductive coughing, fatigue, and weight loss, which tend to develop slowly, over several months. While many forms are progressive and serious, some types of ILD remain mild or stable for extended periods, especially with early detection and appropriate treatment. The average rate of survival for someone with this disease is between three and five years. The term ILD is used to distinguish these diseases from obstructive airways diseases. There are specific types in children, known as children's interstitial lung diseases. The acronym ChILD is sometimes used for this group of diseases. In children, the pathophysiology involves a genetic component, exposure-related injury, autoimmune dysregulation, or all of the components.
American Heart Association's Heart Attack web site – Information and resources for preventing, recognizing, and treating a heart attack. TIMI Score for UA/NSTEMI Archived 2016-11-05 at the Wayback Machine and STEMI Archived 2009-03-19 at the Wayback Machine HEART Score for Major Cardiac Events Archived 2016-10-28 at the Wayback Machine "Heart Attack". MedlinePlus. U.S. National Library of Medicine.
Cantharellus californicus Cantharellus cascadensis Cantharellus cibarius, which has been split into several species Cantharellus cinnabarinus Cantharellus enelensis Cantharellus formosus Cantharellus lateritius Cantharellus minor Cantharellus roseocanus Cantharellus subalbidus Craterellus cinereus Craterellus cornucopioides Craterellus ignicolor Craterellus tubaeformis Merulius odoratus Gomphus clavatus Polyozellus multiplex
Sources: en.wikipedia.org
Plastocyanin is one of the family of blue copper proteins that are involved in electron transfer reactions. The copper-binding site is described as distorted trigonal pyramidal. The trigonal plane of the pyramidal base is composed of two nitrogen atoms (N1 and N2) from separate histidines and a sulfur (S1) from a cysteine. Sulfur (S2) from an axial methionine forms the apex. The distortion occurs in the bond lengths between the copper and sulfur ligands. The Cu−S1 contact is shorter (207 pm) than Cu−S2 (282 pm). The elongated Cu−S2 bonding destabilizes the Cu(II) form and increases the redox potential of the protein. The blue color (597 nm peak absorption) is due to the Cu−S1 bond where S(pπ) to Cu(dx2−y2) charge transfer occurs. In the reduced form of plastocyanin, His-87 will become protonated with a pKa of 4.4. Protonation prevents it acting as a ligand and the copper site geometry becomes trigonal planar.
In 1976 South Africa saw settlement of the Rhodesian question as vital on several fronts: to cauterise the wound of the psychological blow … caused by her defeat in the Angolan conflict; to pre-empt possible Cuban intervention in Rhodesia and the possibility of South Africa being sucked into another Cold War regional conflict without the support and endorsement of the western powers In the latter 1970s, the militants had successfully put the economy of Rhodesia under significant pressure while the numbers of guerrillas in the country were steadily increasing. The government abandoned its early strategy of trying to defend the borders in favour of trying to defend key economic areas and lines of communication with South Africa, while the rest of the countryside became a patchwork of "no-go areas".
==== MeSH D12.776.422.512.426 – hemoglobins, abnormal ==== MeSH D12.776.422.512.426.338 – hemoglobin C MeSH D12.776.422.512.426.375 – hemoglobin E MeSH D12.776.422.512.426.463 – hemoglobin H MeSH D12.776.422.512.426.480 – hemoglobin J MeSH D12.776.422.512.426.510 – hemoglobin M MeSH D12.776.422.512.426.588 – hemoglobin, sickle
=== Economics === In the United States, the 800 mcg tablet was 6.75 times more expensive as of 2020 than the lozenge. As of 2023, the average cost for an injectable fentanyl solution (50 mcg/mL) is around US$17 for a supply of 20 milliliters, depending on the pharmacy. In a 2020 report by the Australian Institute of Criminology, a 100-microgram transdermal patch was valued from between AU$75 and AU$450 on illicit markets. Furthermore, in another 2020 study, the average price per gram of non-pharmaceutical fentanyl on various cryptomarkets was US$1,470.40 for offerings of less than five grams; the average for offers over five grams was US$139.50. In addition, on DreamMarket furanfentanyl (Fu-F), the most common analog on said market, the average price per gram was US$243.10 for retail listings and US$26.50 per gram for wholesale listings.
The mechanisms underlying the pathogenesis of vancomycin nephrotoxicity are multifactorial but include interstitial nephritis, tubular injury due to oxidative stress, and cast formation. Therapeutic drug monitoring can be used during vancomycin therapy to minimize the risk of nephrotoxicity associated with excessive drug exposure. Immunoassays are commonly utilized for measuring vancomycin levels. In children, concomitant administration of vancomycin and piperacillin/tazobactam has been associated with an elevated incidence of AKI relative to other antibiotic regimens.
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.
The peptide is glycyl-L-histidyl-L-lysine, a three-amino-acid sequence commonly abbreviated GHK. It binds a single copper(II) ion under typical laboratory conditions. The free peptide and the copper complex are separate chemical species with different properties.