This is a working overview of Coordination complex, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-05-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Long-term storage | -20 °C | Dry powder, sealed and protected from light |
| Working storage | 2 to 8 °C | Short-term holding; avoid repeated warming cycles |
| Purity assay | Reversed-phase HPLC with UV detection | Detection commonly near 214 nm |
| Copper assay | ICP-OES or atomic absorption | Confirms metal content and the metal-to-peptide ratio |
| Visible absorption | Roughly 520 to 600 nm | Rapid indicator of complex integrity |
Copper(II) binds the peptide through four nitrogen donors: the terminal amino group, the imidazole nitrogen of histidine, and two deprotonated amide nitrogens of the peptide backbone. This tetradentate arrangement gives a roughly square-planar geometry, the thermodynamically favoured form near neutral pH. Because the amide nitrogens must lose a proton before they can coordinate, complex formation is strongly pH-dependent, and the fully coordinated species dominates only above mildly acidic conditions. Electronic transitions within the copper d orbital set produce the characteristic blue to violet colour in aqueous solution.
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.
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.
Stability of GHK-Cu in solution depends on pH, temperature, buffer composition, and oxygen exposure. The copper center can undergo reduction or dissociation, especially in the presence of strong metal chelators such as EDTA. Aqueous solutions are often prepared fresh or stored frozen to limit degradation. Lyophilized solid is more stable than liquid formulations, but it can absorb moisture and should be kept dry. Light exposure may also affect copper complexes, though the effect is often modest.
Purity assessment typically involves high-performance liquid chromatography for the peptide and atomic spectroscopy for copper content. The ratio of copper to peptide is a key quality parameter; a value near one indicates proper stoichiometry. Impurities can include free peptide, copper salts, and truncated sequences from synthesis. Because the complex is dynamic, sample preparation and mobile-phase conditions can shift the observed species. Reported purity values therefore depend on the analytical method and should be interpreted with that context.
Characterizing GHK-Cu requires methods that distinguish the intact complex from free peptide and unbound copper. UV-visible absorption around 600 nm provides a rapid check for copper coordination, while circular dichroism reports on peptide secondary structure. Mass spectrometry confirms the peptide mass and can detect copper adducts under carefully controlled conditions. Electron paramagnetic resonance is particularly informative for Cu(II) because it reveals the ligand field symmetry. No single technique fully defines the complex, so laboratories combine orthogonal methods.
== Method principle == Before the introduction of the first automated cell counters, hematologists were referred to manual cell count under the microscope. The Celloscope method for automated counting of blood cells was described in an article by Öhlin in 1958. In the described method, cells in a saline (conductive) solution are allowed to pass through a capillary with a length and diameter corresponding to the size of blood cells. At the same time, an electric current passes the capillary, and each cell then gives rise to an electric pulse through the increase in resistance that it causes in the electric circuit. The number of pulses is recorded and corresponds to the number of cells in a certain volume. Diluting the blood sample to a sufficient extent for the distance between the cells when passing through the capillary to be greater than the dimension of the cells and capillary ensures that each cell is counted individually. As cells are counted in an absolute volume of the suspension, the number of cells in mm3 of whole blood can be calculated using the dilution factor. The described automated Celloscope cell count method enabled an improved accuracy compared with manual examination by microscopy, while decreasing manual work for the operator. The method allows 50 000 cells to be counted in about 45 seconds, with high accuracy. The Celloscope counter was also equipped with a discriminator, or electrical threshold, which allows only pulses above a certain size to be counted, enabling different blood cells to be counted.
== Safety == In vivo dermal sensitization studies according to OECD 429 confirmed HBTU is a moderate skin sensitizer, showing a response at 0.9 wt% in the Local Lymph Node Assay (LLNA) placing it in Globally Harmonized System of Classification and Labelling of Chemicals (GHS) Dermal Sensitization Category 1A. Thermal hazard analysis by differential scanning calorimetry (DSC) shows HBTU is potentially explosive.
Ethanol-containing beverages can cause alcohol flush reactions, exacerbations of rhinitis, and, more seriously and commonly, bronchoconstriction in patients with a history of asthma, and in some cases, urticarial skin eruptions, and systemic dermatitis. Such reactions can occur within 1–60 minutes of ethanol ingestion, and may be caused by:
The very success of modernization encourages "utopian" hopes that all problems can be solved via the "spirit of science" that are inevitably dashed. Modern society causes unavoidable "irritations" which led to people looking backwards to "traditions" and/or a "clean" modernity where the state would attempt to solve social problems via radical means. The "demystification of the world" leads people to seek faith and self-validation either via irrational theories such as "race" and/or a charismatic leader who would revitalize society. Modernity creates a mass society that can be more easily manipulated and mobilized to ends that can be either moral or amoral. Peukert argued that starting in 1929 that the disjoint between Weimar democracy vs. the problems of "classical modernity" started to fell apart when faced with the Great Depression. Peukert maintained that the Weimar Republic was a muddled system built out of the compromises between so many different interests with for instance Weimar Coalition consisting of the left-wing SPD, the liberal DDP, and the centre-right Zentrum being the only political parties wholeheartedly committed to the Weimar republic. Other competing interests in Germany included the struggle between men vs. women, farmers vs. towns, Catholics vs. Protestants, and unions vs. business.
Sources: en.wikipedia.org
== Epidemiology == Plantar fasciitis is the most common type of plantar fascia injury and is the most common reason for heel pain, responsible for 80% of cases. The condition tends to occur more often in women, military recruits, older athletes, dancers, the obese, and young male athletes. Plantar fasciitis is estimated to affect 1 in 10 people at some point during their lives, most commonly those 40-60 years old. In the United States alone, more than two million people receive treatment annually at a cost estimated to be $284 million.
Degradation to tetranorlipoic acid in which the four CH2-groups between the ring and the carboxilic acid are removed, oxidation of one or both of the sulfur atoms to the sulfoxide, and S-methylation of the sulfide occur. Degradation of lipoic acid is similar in humans, although it is not clear if the sulfur atoms become significantly oxidized.
=== Valine === Valine is produced by a four-enzyme pathway. It begins with the condensation of two equivalents of pyruvate catalyzed by acetohydroxy acid synthase yielding α-acetolactate. The second step involves the NADPH+-dependent reduction of α-acetolactate and migration of methyl groups to produce α, β-dihydroxyisovalerate. This is catalyzed by acetohydroxy isomeroreductase. The third step is the dehydration of α, β-dihydroxyisovalerate catalyzed by dihydroxy acid dehydrase. In the fourth and final step, the resulting α-ketoisovalerate undergoes transamination catalyzed either by an alanine-valine transaminase or a glutamate-valine transaminase. Valine biosynthesis is subject to feedback inhibition in the production of acetohydroxy acid synthase.
Biko was commemorated in several artworks after his death. Gerard Sekoto, a South African artist based in France, produced Homage to Steve Biko in 1978, and another South African artist, Paul Stopforth, included a work entitled The Interrogators in his 1979 exhibition. A triptych, it depicted the three police officers implicated in Biko's death. Kenya released a commemorative postage stamp featuring Biko's face. Biko's death also inspired several songs, including from artists outside South Africa such as Tom Paxton and Peter Hammill. The English singer-songwriter Peter Gabriel released "Biko" in tribute to him, which was a hit single in 1980, and was banned in South Africa soon after. Along with other anti-apartheid music, the song helped to integrate anti-apartheid themes into Western popular culture. Biko's life was also commemorated through theatre. The inquest into his death was dramatised as a play, The Biko Inquest, first performed in London in 1978; a 1984 performance was directed by Albert Finney and broadcast on television. Anti-apartheid activists used Biko's name and memory in their protests; in 1979, a mountaineer climbed the spire of Grace Cathedral in San Francisco to unfurl a banner with the names of Biko and imprisoned Black Panther Party leader Geronimo Pratt on it. Following apartheid's collapse, Woods raised funds to commission a bronze statue of Biko from Naomi Jacobson. It was erected outside the front door of city hall in East London on the Eastern cape, opposite a statue commemorating British soldiers killed in the Second Boer War.
== Chemistry == The 2C drugs, also known as 4-substituted 2,5-dimethoxyphenethylamines, are substituted phenethylamines and can be thought of as synthetic analogues of the naturally occurring phenethylamine psychedelic mescaline (3,4,5-trimethoxyphenethylamine). They are the phenethylamine (2C) analogues of the amphetamine (α-methylphenethylamine) DOx drugs like DOM, DOB, and DOI as well as of the phenylisobutylamine (α-ethylphenethylamine) 4C drugs like Ariadne (4C-D) and 4C-B. The N-benzylphenethylamines such as 25I-NBOMe, 25B-NBOMe, and 25C-NBOMe are derivatives of the 2C drugs. Certain FLY drugs such as 2C-B-FLY are also 2C derivatives.
Sources: en.wikipedia.org
==== Backwash effect ==== The backwash effect in breastfeeding refers to the process in which an infant's saliva flows back into the mother's breast during nursing. This backward flow may introduce the baby's saliva into the mammary gland, potentially prompting the mother's body to produce tailored immune responses in her breast milk to meet the infant's specific needs.
In mid-2017, Wenger brought in two signings; Alexandre Lacazette for a fee of £45m, the club's most expensive signing, and Sead Kolašinac on a free transfer from Schalke 04. On 6 August, Wenger won his seventh FA Community Shield as manager as Arsenal beat Chelsea 4–1 on penalties following a 1–1 score at full time. However, in the 2017–18 FA Cup, Arsenal lost to Nottingham Forest in the third round of the FA Cup, and again stood well outside the top four in the Premier League. The club also dealt with player unrest in the form of Sánchez, who voiced his desire to depart, and Wenger sanctioned a transfer to Manchester United in January 2018, whereby Arsenal received Henrikh Mkhitaryan in a swap-deal. Later that month, he signed Pierre-Emerick Aubameyang for a club-record fee of £56 million. However, these additions did not aid Arsenal's performances as a team, and on 20 April, Wenger announced he would step down as Arsenal manager at the end of the 2017–18 season. His final home game was a 5–0 win against Burnley on 6 May, where he received a standing ovation before the game and was gifted the gold mini-replica Premier League trophy he won during the 2003–04 Invincibles season as a departing gift from Arsenal. He officially concluded his tenure with a 1–0 away win against Huddersfield Town. Wenger later revealed that he wanted to stay at the club until the expiration of his contract, but the club thought it better he leave, with the board informing him in January of their decision to end his contract at the end of the season.
=== Israel === Prime Minister Benjamin Netanyahu welcomed the decision to halt the strikes on Iran, but insisted that the ceasefire does not apply to the Lebanon war, contradicting Shehbaz Sharif's announcement. Netanyahu also asserted that the ceasefire was "not the end" of the military campaign against Iran, saying that "it is a stop on the way to achieving all of our objectives", which will be achieved "either by agreement, or by resuming the fighting". An advisor to Netanyahu said that Israel and the US were in "complete agreement" about current tensions. Israel's diaspora affairs minister and Likud party member Amichai Chikli called the ceasefire a "mistake", saying that "countries like these, the Japanese Empire, Nazi Germany, you need to bring them to their knees". A 13 April poll conducted by the Hebrew University of Jerusalem found that most members of the Israeli public oppose the ceasefire, with 63 percent believing that the ceasefire does not extend to Lebanon, when asked what Israel should do about Iran, 39 percent said Israel should continue attacks, 41 percent said their country should respect the ceasefire. On 29 May, a report suggested that Netanyahu and his inner political circle were privately disgruntled with Trump over his alleged subversions and cancelations of Israeli plans to topple the Iranian government and viewed the concept of an emerging American agreement with Iran as "disastrous".
The chest x-ray is distinctive with features that appear similar to an extensive pneumonia, with both lungs showing widespread white patches. The white patches may seem to migrate from one area of the lung to another as the disease persists or progresses. Computed tomography (CT) may be used to confirm the diagnosis. Often the findings are typical enough to allow the doctor to make a diagnosis without ordering additional tests. To confirm the diagnosis, a doctor may perform a lung biopsy using a bronchoscope. Many times, a larger specimen is needed and must be removed surgically. Plain chest radiography shows normal lung volumes, with characteristic patchy unilateral or bilateral consolidation. Small nodular opacities occur in up to 50% of patients and large nodules in 15%. On high resolution computed tomography, airspace consolidation with air bronchograms is present in more than 90% of patients, often with a lower zone predominance. A subpleural or peribronchiolar distribution is noted in up to 50% of patients. Ground glass appearance or hazy opacities associated with the consolidation are detected in most patients. Histologically, cryptogenic organizing pneumonia is characterized by the presence of polypoid plugs of loose organizing connective tissue (Masson bodies) within alveolar ducts, alveoli, and bronchioles.
The Birman, also called the "Sacred Cat of Burma", is a domestic cat breed. The Birman is a long-haired, colour-pointed cat distinguished by a silky coat, deep blue eyes, and contrasting white "gloves" on each paw. The breed name is derived from Birmanie, the French form of Burma. The breed was first recognised in 1925 in France.
Sources: en.wikipedia.org
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.
The colour comes from electronic transitions between the copper ion and the surrounding peptide nitrogen atoms. The resulting absorption sits in the visible region, giving the solid and its solutions a blue to violet appearance. Loss of colour can indicate that the copper has dissociated from the peptide.
Chromatography establishes the identity and purity of the peptide, while elemental analysis establishes the copper content. The two results should agree with a one-to-one ratio. Visible spectroscopy adds a quick check that the complex itself is intact.
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.