skin penetration 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.
Updated 2025-09-21. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Practical handling notes centre on limiting exposure to water, oxygen, and repeated temperature cycling. Weighed powder is often equilibrated to room temperature before opening to avoid condensation on the solid. Working solutions are typically divided into single-use aliquots and frozen rather than stored refrigerated for long periods. Reported shelf lives vary widely between laboratories, and no single set of conditions is universally treated as a reference standard, which complicates direct comparison of published stability figures.
Solutions of GHK-Cu respond strongly to pH, redox conditions, and the presence of competing chelators such as EDTA. Below roughly pH 4 the copper tends to dissociate, because the amide nitrogen donors become protonated and can no longer coordinate. Strongly alkaline conditions instead favour hydrolysis and precipitation of copper hydroxide. Dissolved oxygen and light accelerate breakdown of the peptide backbone, and the copper released during that process can catalyse further oxidation, so dry, cold, dark storage is the usual recommendation.
| Property | Value | Notes |
|---|---|---|
| INCI name | Copper tripeptide-1 | Standard designation on cosmetic ingredient labels |
| Peptide sequence | Gly-His-Lys | Three-residue ligand; binding occurs at the histidine side chain |
| Metal-to-peptide ratio | 1 to 1 | One copper(II) ion per peptide unit |
| Appearance | Blue to violet powder | Colour arises from copper-to-peptide electronic transitions |
| Water solubility | Freely soluble | Commonly formulated in aqueous or water-alcohol systems |
Identity and purity are normally checked by reversed-phase high-performance liquid chromatography, often coupled to mass spectrometry. The peptide absorbs in the ultraviolet region, and the copper complex also shows a broad visible absorption band that can be followed spectroscopically. Copper content is measured separately, for example by inductively coupled plasma mass spectrometry or atomic absorption spectroscopy, because the peptide assay alone does not confirm how much metal is bound. Purity figures therefore need a stated basis: peptide peak area, copper content, or both.
Aqueous GHK-Cu solutions are less stable than the dry powder. Light, dissolved oxygen and elevated temperature all accelerate loss of the intact complex, and the main observable changes are fading of the blue colour and the appearance of peptide fragments. Acidic conditions protonate the histidine imidazole and weaken copper binding, while strongly alkaline conditions promote hydrolysis of the peptide backbone. Because several degradation routes operate at once, a single shelf-life figure does not describe all storage conditions.
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.
Analytical confirmation usually combines a separation method with a copper-specific measurement. Liquid chromatography or mass spectrometry establishes peptide identity and purity, while an elemental measurement quantifies the metal content. A frequent misconception is that any blue solution contains an intact copper peptide complex; color alone does not confirm structure, because free copper salts and degraded mixtures can also appear colored. Literature on efficacy is mixed, with in vitro findings often more dramatic than human evidence, and reviews note small sample sizes and short follow-up. Open questions include optimal concentration, skin penetration, and long-term effects.
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.
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.
GHK-Cu is a coordination complex formed between the peptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The unbound chain, abbreviated GHK, consists of three amino acids and occurs naturally in human plasma, saliva, and urine. Binding of the metal is mediated mainly by the imidazole nitrogen of the histidine residue together with backbone amides, producing a stable chelate. Ingredient nomenclature often lists the same substance as copper tripeptide-1. Its charge and solubility behaviour differ from those of the metal-free chain.
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.
=== Reproductive output === While the average weight of females does not differ between high and low-density population conditions reproductive output is greater in low-density conditions compared to high-density conditions. Females in high-density conditions also experience a higher mortality rate. In a study by Wall and Begon (1987) 10 of 29 females in high-density conditions died while no females died in the low-density conditions. A positive correlation also exists between the number of eggs per pod and the length of a female's hind femur. Females in high-density conditions produced only half of the eggs produced by females in low-density conditions. Larger females in high-density conditions produce eggs at a faster rate than smaller females. While smaller females in low-density groups produce eggs faster than larger females resulting in an equal reproductive output between small and large females.
C3Cl4 + AlCl3 → [C3Cl3]+AlCl−4 Tetrachlorocyclopropene can be converted to tris(tert-butyldimethylsilyl)cyclopropene. Hydride abstraction with nitrosonium tetrafluoroborate yields the trisilyl-substituted cyclopropenium cation.
In March 2020, the Chinese government was found to be using the Uyghur minority for forced labour, inside sweat shops. According to a report published then by the Australian Strategic Policy Institute (ASPI), no fewer than around 80,000 Uyghurs were forcibly removed from the region of Xinjiang and used for forced labour in at least twenty-seven corporate factories. According to the Business and Human Rights resource center, corporations such as Abercrombie & Fitch, Adidas, Amazon, Apple, BMW, Fila, Gap, H&M, Inditex, Marks & Spencer, Nike, North Face, Puma, PVH, Samsung, and UNIQLO have each sourced products from these factories prior to the publication of the ASPI report.
== Artificial intelligence readiness == The Government Artificial Intelligence Readiness Index 2019 seeks to answer the question, "how well placed are national governments to take advantage of the benefits of AI in their operations and delivery of public services?" In its survey of 194 nations, research firm Oxford Insights conducted research on behalf of Canada's International Development Research Centre (IDRC). Thailand ranked 56 of 194 nations. Other ASEAN members were ranked: Singapore, 1; Malaysia, 22; Philippines, 50; Indonesia, 57; Vietnam, 70; Brunei, 121; Cambodia, 124; Laos, 137; and Myanmar, 159.
=== Types of rhinoplasty === In plastic surgical praxis, the term primary rhinoplasty denotes an initial (first-time) reconstructive, functional, or aesthetic corrective procedure. The term secondary rhinoplasty denotes the revision of a failed rhinoplasty, an occurrence in 5–20 per cent of rhinoplasty operations, hence a revision rhinoplasty. The corrections usual to secondary rhinoplasty include the cosmetic reshaping of the nose because of a functional breathing deficit from an over aggressive rhinoplasty, asymmetry, deviated or crooked nose, areas of collapses, hanging columella, pinched tip, scooped nose and more. Although most revision rhinoplasty procedures are "open approach", such a correction is more technically complicated, usually because the nasal support structures either were deformed or destroyed in the primary rhinoplasty; thus the surgeon must re-create the nasal support with cartilage grafts harvested either from the ear (auricular cartilage graft) or from the rib cage (costal cartilage graft). A functional rhinoplasty refers to a rhinoplasty performed to alleviate nasal obstruction, whereas a cosmetic rhinoplasty refers to a rhinoplasty performed for aesthetic reasons. Procedures performed as part of a functional rhinoplasty typically include septoplasty, inferior turbinate reduction, and spreader graft placement. Results Can be good if performed by an experienced practitioner. As in all plastic surgery procedures, there can be some unpredictability, and biologic systems can heal in different ways.
Sources: en.wikipedia.org
=== Founding and early years === On June 20, 1919, Roy W. Allen opened his first root beer stand in Lodi, California. The first day was for a homecoming celebration of soldiers who returned from battle in World War I. The following day, his stand was open for regular customers, selling root beer glasses for 5 cents (equivalent to $0.93 in 2025). The following year, Allen opened a second stand in Stockton, California. Shortly afterward, the effect of the period of prohibition that existed in the United States from 1920 to 1933 gave Allen and his stand with a beverage with "beer" in the name a heavy rebound. Four years later, A&W began when Allen and Frank Wright opened their drive-in restaurant in Sacramento, California, combining both of their initials for the name, and selling the root beer from Allen's stand. Curbside service was provided by tray boys and tray girls. In 1924, Allen purchased Frank Wright's stake in the business. In 1925, Allen began franchising the root beer, while the franchisee added the other menu items and operated at their discretion. Most of the restaurants that opened under this scheme were on the highways of the Central Valley region, mainly for travelers. This may have arguably been the first successful food-franchising operation. Allen sold the company in 1950 and retired. A lot of World War I veterans eventually founded A&W franchises throughout the US, while some of their descendants still own franchises. A&W's initial menu relied heavily on root beer and snacks, such as popcorn and peanuts, as well as sandwiches on sliced bread. In 1927, J.
=== Foreign policy === Polls conducted in the late 2010s and early 2020s of adults under the age of 30 show that the top foreign-policy issues for this cohort were combating climate change, preventing the proliferation of weapons of mass destruction, and defending the United States from terrorism. Maintaining American military strength and defending American allies were not as important to young voters. Moreover, young Americans are markedly less concerned about combating America's geopolitical adversaries, notably China and Russia, compared to older voters, who still have lingering sentiments from the (previous) Cold War. A 2019 poll by the International Federation of Accountants found that in the United States, 52% of Generation Z wanted their government to focus more on national problems, a 24% margin ahead of those who thought otherwise. Similarly, 2020 poll conducted by the Center for American Progress found that only 18% of Americans supported liberal internationalism, which has been part of American foreign policy since the time of President Franklin D. Roosevelt, while young Americans were even less likely to support it, contributing to a return towards isolationism, a historical norm dating back to the Founding Fathers. Polls indicates that by 2025, there is broad support for isolationism and tariffs (imposed by President Donald Trump in his trade wars) among Gen-Z Americans.
Average life expectancy following diagnosis is about four years. Updated international guidelines were published in 2022, which resulted in some simplification in diagnosis and the removal of antacids as a possible adjunct therapy.
=== Skip chain === Has a left cutter, drive link, drive link, right cutter arrangement. It has one-third fewer cutting teeth and is generally used on long bars (≥24 in or 610 mm) for added chip clearance or when a bar longer than ideal for a given power head is used. Fewer teeth require less power to operate.
Members of Generation Z are anxious to pick majors that teach them marketable skills, with an overwhelming majority consider job preparation to be the point of college. A 2018 Gallup poll on over 32,000 university students randomly selected from 43 schools from across the United States found that just over half (53%) of them thought their chosen major would lead to gainful employment. STEM students expressed the highest confidence (62%) while those in the liberal arts were the least confident (40%). Just over one in three thought they would learn the skills and knowledge needed to become successful in the workplace. While the number of students majoring in the humanities has fallen significantly, those in science, technology, engineering, and mathematics, or STEM, have risen sharply. While about half of STEM graduates work in non-STEM jobs, people with collegiate STEM training still tend to earn more, regardless of whether or not their job is STEM-related or not. By the late 2010s, the historical trend of men being more likely to have higher education has reversed. Women are now more likely to enroll in university than men, a trend accelerated by the COVID-19 pandemic. By the end of the 2020–21 academic year, 59.5% of university students were women. This growing sex gap has been growing for four decades in the United States in parallel with other countries of middle to high income. Among those who attend college or university, women are more likely then men to graduate with a degree within six years.
Sources: en.wikipedia.org
== Notable people == The teaching of medicine at the University of Cambridge dates back to 1540 when Henry VIII endowed the University’s first Professorship of Physic, Dr John Blyth. In 1842, George Paget, the famous physician, into his third year at Addenbrooke’s Hospital, pioneered bedside examinations.
=== Design for affinity === Protein–protein interactions are involved in most biotic processes. Many of the hardest-to-treat diseases, such as Alzheimer's disease, many forms of cancer (e.g., TP53), and human immunodeficiency virus (HIV) infection involve protein–protein interactions. Thus, to treat such diseases, it is desirable to design protein or protein-like therapeutics that bind one of the partners of the interaction and, thus, disrupt the disease-causing interaction. This requires designing protein-therapeutics for affinity toward its partner. Protein–protein interactions can be designed using protein design algorithms because the principles that rule protein stability also rule protein–protein binding. Protein–protein interaction design, however, presents challenges not commonly present in protein design. One of the most important challenges is that, in general, the interfaces between proteins are more polar than protein cores, and binding involves a tradeoff between desolvation and hydrogen bond formation. To overcome this challenge, Bruce Tidor and coworkers developed a method to improve the affinity of antibodies by focusing on electrostatic contributions. They found that, for the antibodies designed in the study, reducing the desolvation costs of the residues in the interface increased the affinity of the binding pair.
==== Comparison with other antidepressants ==== In general, sertraline efficacy is similar to that of other antidepressants. For example, a meta-analysis of 12 new-generation antidepressants showed that sertraline and escitalopram are the best in terms of efficacy and acceptability in the acute-phase treatment of adults with depression. Comparative clinical trials demonstrated that sertraline is similar in efficacy against depression to moclobemide, nefazodone, escitalopram, bupropion, citalopram, fluvoxamine, paroxetine, venlafaxine, and mirtazapine. Sertraline may be more efficacious for the treatment of depression in the acute phase (first four weeks) than fluoxetine. There are differences between sertraline and some other antidepressants in their efficacy in the treatment of different subtypes of depression and in their adverse effects. For severe depression, sertraline is as good as clomipramine but is better tolerated. Sertraline appears to work better in melancholic depression than fluoxetine, paroxetine, and mianserin and is similar to the tricyclic antidepressants such as amitriptyline and clomipramine. In the treatment of depression accompanied by OCD, sertraline performs significantly better than desipramine on the measures of both OCD and depression. Sertraline is equivalent to imipramine for the treatment of depression with co-morbid panic disorder, but it is better tolerated. Compared with amitriptyline, sertraline offered a greater overall improvement in quality of life of depressed patients.
In 2019, trastuzumab emtansine was approved in the United States for the adjuvant treatment of patients with HER2-positive early breast cancer (EBC) who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. Approval was based on KATHERINE (NCT01772472), a randomized, multicenter, open-label trial of 1486 patients with HER2-positive EBC. Breast tumor samples were required to demonstrate HER2 overexpression defined as 3+ IHC or ISH amplification ratio ≥ 2.0 determined at a central laboratory using Ventana's PATHWAY anti-HER2-/neu (4B5) Rabbit Monoclonal Primary Antibody or INFORM HER2 Dual ISH DNA Probe Cocktail assays. Patients were required to have had neoadjuvant taxane and trastuzumab-based therapy with residual invasive tumor in the breast and/or axillary lymph nodes. Patients received radiotherapy and/or hormonal therapy concurrent with study treatment per local guidelines. Patients were randomized (1:1) to receive trastuzumab emtansine 3.6 mg/kg intravenously or trastuzumab 6 mg/kg intravenously on day 1 of a 21-day cycle for 14 cycles. The trial's primary endpoint was invasive disease-free survival (IDFS), defined as the time from the date of randomization to first occurrence of ipsilateral invasive breast tumor recurrence, ipsilateral local or regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, or death from any cause.
Pyruvate + NADH + H+ → Lactate + NAD+ This process occurs in the bacteria involved in making yogurt (the lactic acid causes the milk to curdle). This process also occurs in animals under hypoxic (or partially anaerobic) conditions, found, for example, in overworked muscles that are starved of oxygen. In many tissues, this is a cellular last resort for energy; most animal tissue cannot tolerate anaerobic conditions for an extended period of time. Some organisms, such as yeast, convert NADH back to NAD+ in a process called ethanol fermentation. In this process, the pyruvate is converted first to acetaldehyde and carbon dioxide, and then to ethanol. Lactic acid fermentation and ethanol fermentation can occur in the absence of oxygen. This anaerobic fermentation allows many single-cell organisms to use glycolysis as their only energy source. Anoxic regeneration of NAD+ is only an effective means of energy production during short, intense exercise in vertebrates, for a period ranging from 10 seconds to 2 minutes during a maximal effort in humans. (At lower exercise intensities it can sustain muscle activity in diving animals, such as seals, whales and other aquatic vertebrates, for very much longer periods of time.) Under these conditions NAD+ is replenished by NADH donating its electrons to pyruvate to form lactate. This produces 2 ATP molecules per glucose molecule, or about 5% of glucose's energy potential (38 ATP molecules in bacteria). But the speed at which ATP is produced in this manner is about 100 times that of oxidative phosphorylation.
Sources: en.wikipedia.org
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.
The free peptide was reported in 1973 by Loren Pickart, who isolated it from human plasma. Its copper-binding behaviour was characterised over the following years. The metal-bound form has been the subject of most later research.
Yes. Copper tripeptide-1 is the name used in cosmetic ingredient labelling, while GHK-Cu is the shorthand found in the scientific literature. Both refer to the same peptide-copper complex, and the two terms are interchangeable in most technical documents.
Inductively coupled plasma mass spectrometry or atomic absorption spectroscopy gives total copper after acid digestion. Combining that value with a peptide concentration from chromatography or amino acid analysis yields the metal-to-peptide ratio.