A practical reference on Coordination complex: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-07-31. Anything still debated is marked as such rather than presented as settled.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide was isolated from human plasma in the early 1970s by Loren Pickart, who observed that a plasma fraction from young donors stimulated growth in cultured liver cells. The copper-bound form is abbreviated GHK-Cu, while the metal-free peptide is written simply as GHK. In the research literature the complex also appears as copper tripeptide-1 and as glycyl-histidyl-lysine copper complex.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Copper(II)-tripeptide complex | One peptide ligand with one coordinated metal centre |
| Peptide sequence | Gly-His-Lys | Three residues written in one-letter notation |
| Free peptide mass | 340.4 g/mol | Metal-free GHK; the complex has a higher mass |
| Appearance | Blue to violet solid or solution | Colour originates from copper d orbital transitions |
| Storage | Desiccated, -20 °C, protected from light | Dry powder is more stable than dissolved material |
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.
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.
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.
== Scientific approach == In xenobiology, the aim is to design and construct biological systems that differ from their natural counterparts on one or more fundamental levels. Ideally these new-to-nature organisms would be different in every possible biochemical aspect exhibiting a very different genetic code. The long-term goal is to construct a cell that would store its genetic information not in DNA but in an alternative informational polymer consisting of xeno nucleic acids (XNA), different base pairs, using non-canonical amino acids and an altered genetic code. So far cells have been constructed that incorporate only one or two of these features.
On June 13, 2013, ESPN announced that they would end the broadcast of the ESPN 3D channel by the end of that year and would "...experiment with things like UHDTV." On June 26, 2013, Sharp announced the LC-70UD1U, which is a 70 in (180 cm) 4K Ultra HD TV. The LC-70UD1U is the world's first TV with THX 4K certification. On July 2, 2013, Jimmy Kimmel Live! recorded in 4K Ultra HD a performance by musical guest Karmin, and the video clip was used as demonstration material at Sony stores. On July 3, 2013, Sony announced the release of their 4K Ultra HD Media Player with a price of US$7.99 for rentals and US$29.99 for purchases. The 4K Ultra HD Media Player only worked with Sony's 4K Ultra HD TVs. On July 15, 2013, the CTA published CTA-861-F, a standard that applies to interfaces such as DVI, HDMI, and LVDS. The CTA-861-F standard adds support for several Ultra HD video formats and additional color spaces. On September 2, 2013 Acer announced the first smartphone, dubbed Liquid S2, capable of recording 4K video. On September 4, 2013, the HDMI Forum released the HDMI 2.0 specification, which supports 4K resolution at 60 fps. On the same day, Panasonic announced the Panasonic TC-L65WT600—the first 4K TV to support 4K resolution at 60 FPS. The Panasonic TC-L65WT600 has a 65 in (170 cm) screen, support for DisplayPort 1.2a, support for HDMI 2.0, an expected ship date of October, and a suggested retail price of US$5,999.
=== Patents === According to the World Health Organization (WHO), the biggest barrier to vaccine production in less developed countries has not been patents, but the substantial financial, infrastructure, and workforce requirements needed for market entry. Vaccines are complex mixtures of biological compounds, and unlike the case for prescription drugs, there are no true generic vaccines. The vaccine produced by a new facility must undergo complete clinical testing for safety and efficacy by the manufacturer. For most vaccines, specific processes in technology are patented. These can be circumvented by alternative manufacturing methods, but this required R&D infrastructure and a suitably skilled workforce. In the case of a few relatively new vaccines, such as the human papillomavirus vaccine, the patents may impose an additional barrier. When increased production of vaccines was urgently needed during the COVID-19 pandemic in 2021, the World Trade Organization and governments around the world evaluated whether to waive intellectual property rights and patents on COVID-19 vaccines, which would "eliminate all potential barriers to the timely access of affordable COVID-19 medical products, including vaccines and medicines, and scale up the manufacturing and supply of essential medical products".
=== DNA repair === Two classical DNA repair pathways, nucleotide excision repair and base excision repair, are present in hydra, and these repair pathways facilitate unhindered reproduction. The identification of these pathways in hydra is based, in part, on the presence in the hydra genome of genes homologous to genes in other genetically well studied species that have been demonstrated to play key roles in these DNA repair pathways.
=== Plot === Opposing Force opens with Shephard riding on a V-22 Osprey with his squad. His squad discuss their deployment, somewhat irritated that they have not been told what they are being deployed for. However, as they are nearing their landing zone at Black Mesa, airborne alien creatures attack the Osprey formation, causing Shephard's Osprey to crash land. Shephard regains consciousness in a Black Mesa medical bay, tended to by the science team, learning that the Marines are being steadily beaten by the alien forces from Xen and orders have come through to pull out. Consequently, Shephard departs to reach an extraction point and escape the facility. However, Shephard is prevented from reaching the extraction point by the enigmatic G-Man, resulting in the evacuation craft leaving without him. Other Marines who have also been left behind team up with Shephard and attempt to reach another extraction point near Black Mesa's Lambda Complex, but en route they come under attack from black operations units seeking to thoroughly contain the situation and eliminate all survivors. Shephard makes it to the Lambda Complex alive, and briefly sees Gordon Freeman as the latter teleports to Xen in the final stages of Half-Life. To escape the teleportation chamber, Shephard is forced to enter a separate portal, briefly taking him to Xen before depositing him in an entirely different area of the facility.
Sources: en.wikipedia.org
== Further reading == Press Conference by professor Samuel S. Epstein M.D. 1999-05-31 World Trade Organization (2000). Dispute Settlement Reports 1998. Cambridge University Press. p. 79. ISBN 0-521-78895-1. Galbraith, H. (December 2002). "Hormones in international meat production: biological, sociological and consumer issues". Nutrition Research Reviews. 15 (2). CABI Publishing: 293–314. doi:10.1079/NRR200246. PMID 19087409. M. Ellin Doyle. "Human Safety of Hormone Implants Used to Promote Growth in Cattle". National Cattlemen's Foundation. Archived from the original (Microsoft Word) on 7 May 2006. J. J. Kastner & R. K. Pawsey (29 November 2001). "Harmonising sanitary measures and resolving trade disputes through the WTO–SPS framework. Part I: a case study of the US–EU hormone-treated beef dispute" (PDF). Food Control. 13. Elsevier Science Ltd.: 49–55. doi:10.1016/S0956-7135(01)00023-8. Archived from the original (PDF) on 21 May 2004. Tim Josling; Donna Roberts & Ayesha Hassan (12 April 2000). "The Beef-Hormone Dispute and its Implications for Trade Policy" (PDF). Stanford University. Archived from the original (PDF) on 11 June 2007. Grace Skogstad (September 2001). "The WTO and Food Safety Regulatory Policy Innovation in the European Union". Journal of Common Market Studies. 39 (3): 485–505. doi:10.1111/1468-5965.00300. Christina L. Davis (2003). "Battles over Beef: The Beef Hormone Dispute". Food Fights Over Free Trade: How International Institutions Promote Agricultural Trade Liberalization. Princeton University Press. pp. 321–337. ISBN 0-691-11505-2.
Under this new franchise agreement, new owners were disallowed from living more than one hour from their restaurants – restricting them to smaller individuals or ownership groups and preventing large, multi-state corporations from owning franchises. Franchisees were also now prohibited from operating other chains, preventing them from diverting funds away from their Burger King holdings. This new policy effectively limited the size of franchisees and prevented larger franchises from challenging Burger King Corporation as Chart House had. Smith also sought to have BKC be the primary owner of new locations and rent or lease the restaurants to its franchises. This policy would allow the company to take over the operations of failing stores or evict those owners who would not conform to the company guidelines and policies. By 1988, parent company Pillsbury had relaxed many of Smith's changes, scaling back on construction of new locations, which resulted in stalled growth of the brand. Neglect of Burger King by new owner Grand Metropolitan and its successor Diageo further hurt the standing of the brand, causing significant financial damage to BK franchises and straining relations between the parties. By 2001 and after nearly 18 years of stagnant growth, the state of its franchises was beginning to affect the value of the company. One of the franchises most heavily affected by the lack of growth was the nearly 400-store AmeriKing Inc., one of the largest Burger King franchisees.
A fusee is a practical necessity in watches using a verge escapement, and can also provide considerable benefit with a lever escapement and other high precision types of escapements (Hamiltons WWII era Model 21 chronometer used a fusee in combination with a detent escapement). Keywind watches are also commonly seen with conventional going barrels and other types of mainspring barrels, particularly in American watchmaking.
== Mutation studies == Many P-type calcium channels mutations result in a decreased level of intracellular free calcium. Maintaining calcium homeostasis is essential for normally functioning neurons. Changing the cellular calcium ion concentration acts as a trigger for multiple diseases, in severe cases these diseases can result in mass neuronal death. Mutation studies allow experimenters to study genetically inherited channelopathies. A channelopathy is any disease that results from an ion channel with malfunctioning subunits or regulatory proteins. One example of a P-type calcium channel channelopathy is shown in homozygous ataxic mice, who are recessive for both the tottering and leaner genes. These mice present with mutations in the alpha1A subunit of their P/Q type channels. Mutations in these channels result in deficiencies within the cerebellar Purkinje cells that dramatically reduce the channels current density. The tottering mutations within mice result from a missense mutation and causes delayed-onset of seizures and ataxia. The tottering mutation substitutes a single proline instead of a leucine within the P-region of the channel. The P-region is responsible for the formation of the ion channel pore. The leaner mutation, which results in more severe symptoms than the tottering mutation, has been shown to result from a single nucleotide substitution that causes splicing failures within the channels open reading frame.
Sources: en.wikipedia.org
From its origin in 1922 until 1939, WOSM did not have its own emblem. In 1939, its director, J. S. Wilson, introduced an international Scout badge: a silver fleur-de-lis on a purple background containing the five continent names in silver, framed between two concentric circles. Wearing of the badge was confined to WOSM committee members and bureau staff and their past members. The design became WOSM's logo and a purple flag containing the design followed, the flying of which was restricted to WOSM international Scout gatherings.
The pericardial duct contains an ultrafiltrate of the blood known as the pericardial fluid, and the rate of filtration is partly controlled by the muscle- and nerve-rich branchial hearts. The renal appendages move nitrogenous and other waste products from the blood to the renal sacs, but do not add volume. The renal fluid has a higher concentration of ammonia than the urine or the blood, thus the renal sacs are kept acidic to help draw the ammonia from the renal appendages. The ammonia diffuses down its concentration gradient into the urine or into the blood, where it gets pumped through the branchial hearts and diffuses out the gills. The excretion of ammonia by O. vulgaris makes them ammonotelic organisms. Aside from ammonia, a few other nitrogenous waste products have been found to be excreted by O. vulgaris such as urea, uric acid, purines, and some free amino acids, but in smaller amounts. Within the renal sacs, two recognized and specific cells are responsible for the regulation of ions. The two kinds of cells are the lacuna-forming cells and the epithelial cells that are typical to kidney tubules. The epithelia cells are ciliated, cylindrical, and polarized with three distinct regions. These three regions are apical, middle cytoplasmic, and basal lamina. The middle cytoplasmic region is the most active of the three due to the concentration of multiple organelles within, such as mitochondria and smooth and rough endoplasmic reticulum, among others.
The specific features of Down syndrome that predispose to obstructive sleep apnea include relatively low muscle tone, a narrow nasopharynx, and a large tongue. Obesity and enlarged tonsils and adenoids, conditions that occur commonly in the western population, are much more likely to be obstructive in a person with these features than without them. Obstructive sleep apnea occurs even more frequently in people with Down syndrome than in the general population. A little over 50% of all people with Down syndrome experience obstructive sleep apnea. Some physicians advocate routine testing of this group. In other craniofacial syndromes, the abnormal feature may improve the airway, but its correction may put the person at risk for obstructive sleep apnea after surgery when it is modified. Cleft palate syndromes are such an example. During the newborn period, all humans are obligate nasal breathers. The palate is both the roof of the mouth and the floor of the nose. Having an open palate may make feeding difficult, but generally, it does not interfere with breathing; if the nose is very obstructed, then an open palate may relieve breathing. There are several clefting syndromes in which the open palate is not the only abnormal feature; additionally, there is a narrow nasal passage, which may not be obvious. In such individuals, closure of the cleft palate – whether by surgery or a temporary oral appliance – can cause the onset of obstruction.
Sources: en.wikipedia.org
It consists of a three-amino-acid peptide, glycine-histidine-lysine, bound to one copper(II) ion. The peptide supplies four nitrogen donor atoms, and the resulting complex is stable in neutral aqueous solution. The metal-free peptide is usually called GHK.
The three letters are the standard one-letter codes for glycine, histidine, and lysine. The suffix -Cu indicates the coordinated copper ion. Cosmetic ingredient lists often use the alternative name copper tripeptide-1 for the same complex.
No. Free GHK is the peptide alone, while GHK-Cu contains a bound copper atom. The two differ in colour, charge, and binding behaviour, so any study that measures copper delivery must state which form was used.
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.