This is a working overview of reversed-phase HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-09 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Copper(II) tripeptide complex | Contains glycyl-histidyl-lysine ligand |
| Peptide sequence | Gly-His-Lys | N-terminal glycine, C-terminal lysine |
| Molecular formula | C14H22CuN6O4 | Commonly cited for the 1:1 complex |
| Appearance | Blue to blue-violet solid | Color arises from copper d-d transitions |
| Solubility | Water-soluble | Also dissolves in some polar solvents |
Identity and purity are established with a combination of chromatographic and spectroscopic techniques. Reversed-phase high-performance liquid chromatography separates the intact complex from peptide fragments and free copper, and the elution profile yields a purity estimate. Mass spectrometry gives the mass of the intact species and exposes degradation products. Ultraviolet-visible spectroscopy displays a broad absorption band in the visible region that is characteristic of the copper center. Nuclear magnetic resonance is less informative here, because the paramagnetic metal broadens signals and complicates spectral interpretation.
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.
The International Nomenclature of Cosmetic Ingredients lists the substance as copper tripeptide-1, the name that appears on most topical product labels. Related designations include copper peptide and GHK-Cu, and the hyphenated form is common in research literature. In cosmetics the material is regulated as an ingredient rather than as a drug, so products may reach the market without evidence of the effects claimed for them. Whether those effects are clinically meaningful is an open question, since most supportive data come from laboratory work and small trials.
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 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.
Published work on GHK-Cu concentrates largely on cell culture systems rather than whole organisms. Frequently used endpoints include collagen synthesis, expression of matrix metalloproteinases, and migration of fibroblasts. Some reports describe antioxidant behavior, while others stress delivery of copper into cells. These mechanisms are proposed rather than demonstrated, and the relative weight of each pathway is unclear. Human trials are few and generally small, so laboratory findings should not be read as confirmed clinical results.
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.
=== Comparison of AAS === AAS differ in a variety of ways including in their capacities to be metabolized by steroidogenic enzymes such as 5α-reductase, 3-hydroxysteroid dehydrogenases, and aromatase, in whether their potency as AR agonists is potentiated or diminished by 5α-reduction, in their ratios of anabolic/myotrophic to androgenic effect, in their estrogenic, progestogenic, and neurosteroid activities, in their oral activity, and in their capacity to produce hepatotoxicity.
=== 2019 revision of the SI === Before the 2019 revision of the SI, the mole was defined as the amount of substance of a system that contains as many elementary entities as there are atoms in 12 grams of carbon-12 (the most common isotope of carbon). The term gram-molecule was formerly used to mean one mole of molecules, and gram-atom for one mole of atoms. For example, 1 mole of MgBr2 is 1 gram-molecule of MgBr2 but 3 gram-atoms of MgBr2. In 2011, the 24th meeting of the General Conference on Weights and Measures (CGPM) agreed to a plan for a possible revision of the SI base unit definitions at an undetermined date. On 16 November 2018, after a meeting of scientists from more than 60 countries at the CGPM in Versailles, France, all SI base units were defined in terms of physical constants. This meant that each SI unit, including the mole, would not be defined in terms of any physical objects but rather they would be defined by physical constants that are, in their nature, exact. Such changes officially came into effect on 20 May 2019. Following such changes, "one mole" of a substance was redefined as containing "exactly 6.02214076×1023 elementary entities" of that substance.
4-HO-DPT acts as a high-efficacy partial agonist to full agonist of the serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptors. It has more than two orders of magnitude greater potency as an agonist of the serotonin 5-HT2A and 5-HT2B receptors than as an agonist of the serotonin 5-HT2C receptor. Hence, it shows considerable selectivity for the serotonin 5-HT2A receptor over the serotonin 5-HT2C receptor. Compared to psilocin (4-HO-DMT), 4-HO-DPT has about the same potency and efficacy as a serotonin 5-HT2A receptor agonist, has about the same potency but is much more efficacious as a serotonin 5-HT2B receptor agonist (EmaxTooltip maximal efficacy = 39% vs. 94%, respectively), and has about the same efficacy but approximately 10-fold lower potency as a serotonin 5-HT2C receptor agonist. 4-HO-DPT produces the head-twitch response, a behavioral proxy of psychedelic effects, in rodents. Its potency for inducing the head-twitch response in mice is about 4- or 5-fold lower than that of psilocin.
18 December: The Ministry of Education cancels Gloriavale Christian School's registration as a private school effective 23 January next year, citing insufficient evidence that the school was complying with registration criteria. Wellington High Court Justice Jason McHerron orders Corrections Department chief executive Jeremy Lightfoot to comply with a legal requirement entitling prisoners to at least one hour of exercise daily. The Waihi North extension of OceanaGold's Waihi mine becomes the first mining project to gain approval under the Fast-track Approvals Act 2024's regime. The Whangarei District Council votes unanimously to reject plans for fast-tracked sand mining at Bream Bay. 19 December: Esarona David Lologa is sentence to life imprisonment with a minimum term of 22 years for murdering five people and causing the Loafers Lodge fire in 2023. High Court Justice David Gendall rules that Justice Minister Paul Goldsmith unlawfully appointed Human Rights Commissioner Stephen Rainbow and Race Relations Commissioner Melissa Derby. 20 December — Members of the Brian Tamaki–aligned "True Patriots of NZ" attempt to block a Sikh rally in Auckland. Police intervene to keep the two groups apart. 22 December — India and New Zealand confirm plans to sign a free trade agreement in 2026. 23 December - A scrub fire destroys multiple buildings and forces the evacuation of several residents between Fernhill, Hawke's Bay and the Ngaruroro River bridge.
=== Fraction collector === The fraction collector is typically a rotating rack that can be filled with test tubes or similar containers. Distribution of the eluate into separate containers are determined by fixed volumes or specific fractions detected at peaks of protein concentration. Many systems include various optional components. A filter may be added between the mixer and column to minimize clogging. In large FPLC columns the sample may be loaded into the column directly using a small peristaltic pump rather than an injection loop. When the buffer contains dissolved gas, bubbles may form as pressure drops where the buffer exits the column; these bubbles create artifacts if they pass through the flow cells. This may be prevented by degassing the buffers, e.g. with a degasser, or by adding a flow restrictor downstream of the flow cells to maintain a pressure of 1-5 bar in the eluant line.
Sources: en.wikipedia.org
Radiation protection measures may also be necessary against scattered radiation, which occurs during tumor irradiation of the head and neck on metal parts of the dentition (dental fillings, bridges, etc.). Since the 1990s, soft tissue retractors known as radiation protection splints have been used to prevent or reduce mucositis, an inflammation of the mucous membranes. It is the most significant adverse acute side effect of radiation. The radiation protection splint is a spacer that keeps the mucosa away from the teeth and reduces the amount of scattered radiation that hits the mucosa according to the square law of distance. Mucositis, which is extremely painful, is one of the most significant detriments to a patient's quality of life and often limits radiation therapy, thereby reducing the chances of tumor cure. The splint reduces oral mucosal reactions that typically occur in the second and third third of a radiation series and are irreversible.
== The Kenner Prize and Awards at University of Liverpool == The George Kenner Prize and Lectureship was established in 1979 with a sum of £12,000 raised by subscription to commemorate the late Professor GW Kenner, Heath Harrison Professor of Organic Chemistry from 1957 to 1976 and Royal Society Professor from 1977 to 1978. The duty of the Lectureship recipient is to deliver lectures on subjects related to the study of Organic Chemistry at the University. The first of these lectures was held on 28 October 1980. Lord Todd introduced the speaker, George Kenner's former research collaborator and lifelong friend Har Gobind Khorana, Nobel prizewinner and Professor at the Massachusetts Institute of Technology. Other famous organic chemists awarded the honour of the George Kenner Lectureship include Gilbert Stork, Ryoji Noyori, Steven V. Ley, Albert Eschenmoser, John George Adami, Duilio Arigoni, and Jean-Marie Lehn. The George W. Kenner Award for graduate students was established at the University of Liverpool in 2006 to commemorate Kenner. The award is annually given to the first-year PhD student in the organic section of the Department of Chemistry who is the best in both academic and research performance.
The following mechanism shows a proposed scheme for a metal-dependent "pita-bread" enzyme with residue numbering corresponding to those found in methionine aminopeptidase from E. coli. As shown in Intermediate I of the figure, three potential acidic amino acid residues interact with the N-terminus of the substrate in a fashion that is yet to be determined. The carbonyl and amide groups of the scissile peptide bond interact with the first metal ion, M1, in addition to His178 and His79, respectively. M1 and Glu204 activate a water molecule to prepare it nucleophilic attack at the carbonyl carbon of the scissile peptide bond. Then, the tetrahedral intermediate (Intermediate II) becomes stabilized from interactions with M1 and His178. Lastly, Glu204 donates a proton to the amine of the leaving peptide (P1'). This leads to the breakdown of the intermediate (Intermediate III), which retains its interactions with M1 and His178. The reaction pathway of prolidase is a fairly complicated process with many components involved. After a proton is removed from the bridge between the two Mn2+ ions, the GlyPro substrate causes a conformational change as it binds to the active site. This GlyPro is held in place by hydrogen bonds formed by multiple amino acids in this structure. The Gly-N atom of the GlyPro substrate and the Gly-O atom of the peptide bond each interact with the Mn2+ ions, which are stabilized by additional amino acids, leading to polarization.
Opipramol acts as a high affinity sigma receptor agonist, primarily of the σ1 subtype, but also of the σ2 subtype with lower affinity. In one study of σ1 receptor ligands that also included haloperidol, pentazocine, (+)-3-PPP, ditolylguanidine, dextromethorphan, SKF-10,047 ((±)-alazocine), ifenprodil, progesterone, and others, opipramol showed the highest affinity (Ki = 0.2–0.3) for the guinea pig σ1 receptor of all the tested ligands except haloperidol, which it was approximately equipotent with. The sigma receptor agonism of opipramol is thought to be responsible for its therapeutic benefits against anxiety and depression. Unlike other TCAs, opipramol does not inhibit the reuptake of serotonin or norepinephrine. However, it does act as a high affinity antagonist of the histamine H1 receptor and is a low to moderate affinity antagonist of the dopamine D2, serotonin 5-HT2, and α1-adrenergic receptors. H1 receptor antagonism accounts for its antihistamine effects and associated sedative side effects. In contrast to other TCAs, opipramol has very low affinity for the muscarinic acetylcholine receptors and virtually no anticholinergic effects. Sigma receptors are a set of proteins located in the endoplasmic reticulum. σ1 receptors play key role in potentiating intracellular calcium mobilization thereby acting as sensor or modulator of calcium signaling. Occupancy of σ1 receptors by agonists causes translocation of the receptor from endoplasmic reticulum to peripheral areas (membranes) where the σ1 receptors cause neurotransmitter release.
Sources: en.wikipedia.org
Liraglutide and semaglutide should not be used in those with a personal or family history of medullary type thyroid cancers as they may increase the risk of these types of tumors. Their use is further contraindicated in those with acute kidney injury, gallbladder disease or a history of pancreatitis. The FDA prescribing information for semaglutide recommends monitoring for depression or suicidal thoughts during treatment, though a real-world retrospective study of adolescents with obesity found that treatment with liraglutide or semaglutide was associated with a reduced risk for suicidal ideation or attempt. Setmelanotide is approved for children six years or older with certain types of secondary obesity. It may cause skin hyperpigmentation or other dermatologic effects as well as gastrointestinal side effects, with rare instances of depression and suicidal ideation. Metformin is often used off-label in children or adolescents with obesity, and has been found to cause a 1.1 decrease in BMI. A Cochrane review in 2016 concluded that medications might reduce BMI and bodyweight to a small extent in obese children and adolescents. This conclusion was based only on low-quality evidence.
=== On Mars === Thiophene derivatives have been detected at nanomole levels in 3.5 billions year old Martian soil sediments (Murray Formation, Pahrump Hills) by the rover Curiosity at Gale crater (Mars) between 2012 and 2017.
Hegseth ordered the supercarrier USS Gerald R. Ford deployed to Latin America on 24 October. According to The Washington Post, it is "the world's largest aircraft carrier" and its deployment "signaled a major expansion of [the] military campaign against 'Transnational Criminal Organizations' in Latin America". The New York Times reported it "carries about 5,000 sailors and has more than 75 attack, surveillance and support aircraft, including F/A-18 fighters". The Ford's full air wing is reportedly embarked. Though its escort typically includes five Arleigh Burke class destroyers—USS Winston S. Churchill, USS Bainbridge, USS Mahan, USS Forrest Sherman and USS Mitscher—as of 8 November the USS Forrest Sherman and Mitscher were still operating independently in other areas of the globe (such as the Red Sea). On 26 October, a Russian Il-76 transport aircraft under US sanctions landed in Venezuela "after a circuitous route over Africa to avoid Western airspace, according to Flightradar24". The aircraft carried Pantsir-S1 and Buk-M2E air defense systems, according to a Russian official. As of 31 October, Gettysburg (CG-64), another guided missile cruiser, had joined the fleet.
=== Early career === Robinson was one of the few students ever to be appointed to the faculty of the University of California, San Diego immediately after getting his Ph.D., but resigned four years later. He was a co-founder, along with Linus Pauling and Keene Dimick, of the Institute of Orthomolecular Medicine, later renamed the Linus Pauling Institute in 1973.
=== β-Adrenergic receptor antagonism === Stimulation of β1 receptors by epinephrine and norepinephrine induces a positive chronotropic and inotropic effect on the heart and increases cardiac conduction velocity and automaticity. Stimulation of β1 receptors on the kidney causes renin release. Stimulation of β2 receptors induces smooth muscle relaxation, induces tremor in skeletal muscle, and increases glycogenolysis in the liver and skeletal muscle. Stimulation of β3 receptors induces lipolysis. Beta blockers inhibit these normal epinephrine- and norepinephrine-mediated sympathetic actions, but have minimal effect on resting subjects. That is, they reduce the effect of excitement or physical exertion on heart rate and force of contraction, and also tremor, and breakdown of glycogen. Beta blockers can have a constricting effect on the bronchi of the lungs, possibly worsening or causing asthma symptoms. Since β2 adrenergic receptors can cause vascular smooth muscle dilation, beta blockers may cause some vasoconstriction. However, this effect tends to be small because the activity of β2 receptors is overshadowed by the more dominant vasoconstricting α1 receptors. By far the greatest effect of beta blockers remains in the heart. Newer, third-generation beta blockers can cause vasodilation through blockade of alpha-adrenergic receptors. Accordingly, nonselective beta blockers are expected to have antihypertensive effects.
Sources: en.wikipedia.org
GHK is the free tripeptide, while GHK-Cu includes a bound copper(II) ion. The copper complex is the form most often studied for skin and wound-related activity. The two names are sometimes used interchangeably in product labeling, but they refer to distinct chemical species.
Yes, it is found in human plasma, saliva, and urine. Its concentration in plasma tends to decrease with age. This natural presence is one reason researchers have investigated its role in tissue maintenance.
No, GHK-Cu is not an approved drug in major markets. It is widely used as a cosmetic ingredient, where it is listed under names such as copper tripeptide-1. Any therapeutic claims would require separate regulatory review.
Dry powder is best kept cold, dark and sealed, typically at -20 °C for long-term storage or 2 to 8 °C for material in regular use. Vials should be warmed to room temperature before opening to prevent moisture condensing on the contents. Aqueous stock solutions degrade faster and are usually prepared fresh.