This is a working overview of extracellular matrix, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-01-06. Anything still debated is marked as such rather than presented as settled.
Copper takes part in redox chemistry, and the same property that makes it useful in enzymes can generate reactive oxygen species when the ion is loosely bound. GHK chelates copper through imidazole, amino, and amide nitrogen donors, which reduces the amount of free copper in solution. Whether that chelation is protective, neutral, or harmful in a given tissue is not settled. Laboratory assays report both antioxidant and pro-oxidant behavior, depending on the conditions and the readout used.
Published work on GHK-Cu is dominated by in vitro experiments and small animal studies. Human trials tend to be short and small, with endpoints such as skin appearance rather than clinical outcomes. Review articles often summarize the same underlying laboratory findings, which can make the evidence base look broader than it is. Several basic questions remain open: the concentration of the intact complex in human tissue, the route by which it crosses the skin barrier, and whether effects seen in culture produce measurable changes in people.
Laboratory studies describe GHK-Cu as a source of copper that cells can take up, with reported effects on collagen, elastin, and glycosaminoglycan synthesis in cultured fibroblasts. The peptide also appears in wound-repair research, where it is linked to the activity of matrix metalloproteinases and their inhibitors. These observations come largely from cell and animal models. How directly the complex controls any single pathway in intact human skin remains an open question, and reported effects depend on concentration, vehicle, and exposure time.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-lysine and a copper(II) ion. The peptide sequence is conventionally written as Gly-His-Lys, abbreviated GHK. Copper binds through the imidazole nitrogen of histidine, the alpha-amino group, and a deprotonated amide nitrogen, producing a square-planar geometry. The complex carries a net positive charge near physiological pH and is intensely blue in aqueous solution. The metal-free peptide is often written simply as GHK, while the copper-bound form is written GHK-Cu.
The compound was first isolated from human plasma by the biochemist Loren Pickart in 1973. Early work identified it as a factor that altered the behavior of cultured liver cells, and later studies linked it to connective tissue and wound-related processes. Reported plasma concentrations fall markedly between roughly age twenty and age sixty, a pattern that generated interest in copper peptide biology. Whether that decline has functional consequences remains an open question, because differences observed across age groups do not by themselves establish causation. Research interest later expanded into cosmetic and tissue-culture settings.
Mechanistic accounts focus on how the complex delivers copper and how the released peptide interacts with the extracellular matrix. Copper is an essential cofactor for lysyl oxidase and other enzymes involved in collagen and elastin cross-linking, and GHK is one of several peptides able to carry the metal. Reported effects include altered gene expression in fibroblasts and changes in matrix metalloproteinase activity, although many of these findings come from cell culture rather than whole organisms. The relative contribution of the peptide backbone, the copper ion, and downstream copper metabolism is not fully resolved.
| Property | Value | Notes |
|---|---|---|
| Copper binding sites | Imidazole, amino, and amide nitrogens | Form chelate rings with Cu(II) |
| Conditional binding constant | Reported near 10^16 at neutral pH | Value depends on method and medium |
| Visible absorption | Broad band in the blue-violet region | Source of the characteristic color |
| Common analytical methods | LC-MS, HPLC, UV-Vis, ICP-OES | Used for identity and copper content |
| Main degradation routes | Oxidation, photolysis, hydrolysis | Accelerated by light, heat, and pH extremes |
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide backbone consists of glycine, histidine, and lysine joined in that order. Copper is held through the imidazole nitrogen of histidine and the alpha-amino group at the N-terminus, which together produce a square-planar arrangement around the metal center. The solid appears blue to violet, a color that originates from d-d electronic transitions within the copper coordination sphere. The complex is indexed under CAS number 89030-95-5.
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.
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.
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.
Spermidine is an aliphatic polyamine. In plants and some bacteria, spermidine synthase (SPDS) catalyzes its formation from putrescine. It is a precursor to other polyamines, such as spermine and its structural isomer thermospermine. Many of the organisms that make up the gut microbiota in humans do not contain the SPDS enzyme, for example the ϵ-proteobacteria. Instead, they use a combination of two enzymes to produce spermidine from putrescine. First, carboxynorspermidine synthase catalyses a reductive amination using nicotinamide adenine dinucleotide phosphate (NADPH) as the reducing agent.
=== Toxicity due to capping ligands === Some of the capping ligands associated with AuNPs can be toxic while others are nontoxic. In gold nanorods (AuNRs), it has been shown that a strong cytotoxicity was associated with CTAB-stabilized AuNRs at low concentration, but it is thought that free CTAB was the culprit in toxicity . Modifications that overcoat these AuNRs reduces this toxicity in human colon cancer cells (HT-29) by preventing CTAB molecules from desorbing from the AuNRs back into the solution. Ligand toxicity can also be seen in AuNPs. Compared to the 90% toxicity of HAuCl4 at the same concentration, AuNPs with carboxylate termini were shown to be non-toxic. Large AuNPs conjugated with biotin, cysteine, citrate, and glucose were not toxic in human leukemia cells (K562) for concentrations up to 0.25 M. Also, citrate-capped gold nanospheres (AuNSs) have been proven to be compatible with human blood and did not cause platelet aggregation or an immune response. However, citrate-capped gold nanoparticles sizes 8-37 nm were found to be lethally toxic for mice, causing shorter lifespans, severe sickness, loss of appetite and weight, hair discoloration, and damage to the liver, spleen, and lungs; gold nanoparticles accumulated in the spleen and liver after traveling a section of the immune system. There are mixed-views for polyethylene glycol (PEG)-modified AuNPs. These AuNPs were found to be toxic in mouse liver by injection, causing cell death and minor inflammation.
== Formation, 1936–1937 == The first Arab Higher Committee was formed on 25 April 1936, following the outbreak of the Great Arab revolt, and national committees were formed in all of the towns and some of the larger villages, during that month. The members of the committee were:
Sources: en.wikipedia.org
== Early career == After graduating from MIT, Swanson took a job at Citibank, where he managed a venture investment group. His performance pleased his supervisors, and he and a colleague were chosen to open a San Francisco office for Citicorp Venture Capital. However, the new Citicorp investments were not doing well. One particular failure, which Swanson later believed to have been a lucky break, was the bankruptcy of Antex, a science based company that Citicorp had invested in. He worked with Eugene Kleiner, another Citicorp executive, to attempt to get some money out of the company's bankruptcy. Eugene Kleiner was the cofounder of the venture capital partnership Kleiner & Perkins. Swanson left Citicorp and joined Kleiner & Perkins in 1974, under the recommendation of Eugene Kleiner himself. As an associate, Swanson spent a lot of time and effort attempting to convince the heads of the science company Cetus, one which Kleiner and Perkins had invested in, to pursue genetic recombination projects. His interest in the technology had been piqued in a lunch with famed scientist and Nobel laureate Donald Glaser. However, the company refused to take on such a risky endeavor, and Kleiner & Perkins parted ways with the company. This falling out was one of the main reasons for the group's decision to advise Swanson to look for another job. Kleiner & Perkins had decided that they would rather work alone, and by the end of 1975, Swanson's position there would be terminated.
=== Psychological === The primary immediate psychological effects of LSD are visual pseudo-hallucinations and altered thought, often referred to as "trips". These sensory alterations are considered pseudohallucinations because the subject does not perceive the patterns seen as being located in three-dimensional space outside the body. LSD is not considered addictive. An "afterglow" effect, characterized by an improved mood or perceived mental state, may persist for days or weeks following ingestion. Positive experiences, or "good trips", are described as intensely pleasurable and can include feelings of joy, euphoria, an increased appreciation for life, decreased anxiety, a sense of spiritual enlightenment, and a feeling of interconnectedness with the universe. Negative experiences, commonly known as "bad trips", can induce feelings of fear, agitation, anxiety, panic, and paranoia. While the occurrence of a bad trip is unpredictable, factors such as mood, surroundings, sleep, hydration, and social setting, collectively referred to as "set and setting", can influence the risk and are considered important in minimizing the likelihood of a negative experience. Uniquely among psychedelics, LSD appears to have two temporally and qualitatively distinct phases of psychoactive effects. These include an initial psychedelic phase associated with serotonin 5-HT2A receptor agonism and a subsequent paranoia- and psychosis-like phase associated with dopamine D2-like receptor agonism.
=== Isocyanide complexes === Isocyanides also form extensive families of complexes that are related to the metal carbonyls. Typical isocyanide ligands are methyl isocyanide and t-butyl isocyanide (Me3CNC). A special case is CF3NC, an unstable molecule that forms stable complexes whose behavior closely parallels that of the metal carbonyls.
Sources: en.wikipedia.org
=== Retrospective === Retrospective reviews have typically been more appreciative. Craig Butler of AllMovie wrote that "Stone Cold might seem like a throwaway action film built around a sports personality but it's actually much more. In fact, this is a model b-movie". Of the cast, he said that "Bosworth acquits himself well as the hero" and "Lance Henriksen is charming and chilling", while "William Forsythe delivers a feral, rip-snorting turn". He also pointed that "Craig Baxley does an excellent job in the director's chair." Svet Atanasoff of Blu-ray.com deemed that "Stone Cold might be the ultimate macho action film". Not convinced by Bosworth's contention that the excision of its family themes doomed the film, he claimed that he had "always liked it". Ian Jane of DVD Talk commented that "Stone Cold may be dumber than a bag of rocks, and Brian Bosworth might have all the acting charisma of a corn flake, but hot damn if this movie isn't a fantastic slice of brainless action moviemaking done right." John Higgins of Starburst called it "a no-brainer of an action film, following a traditional template and with sufficient bang, clever editing and brutal violence to just carry it over the finish line." Comparing it to Brandon Lee's equally neglected Rapid Fire, he concluded that "it may be short on plot and character, but it is a highly effective action thriller".
=== Public education and outreach === In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of awareness and knowledge about the nervous system among the general public and government officials. Such promotions have been done by both individual neuroscientists and large organizations. For example, individual neuroscientists have promoted neuroscience education among young students by organizing the International Brain Bee, which is an academic competition for high school or secondary school students worldwide. In the United States, large organizations such as the Society for Neuroscience have promoted neuroscience education by developing a primer called Brain Facts, collaborating with public school teachers to develop Neuroscience Core Concepts for K-12 teachers and students, and cosponsoring a campaign with the Dana Foundation called Brain Awareness Week to increase public awareness about the progress and benefits of brain research. In Canada, the Canadian Institutes of Health Research's (CIHR) Canadian National Brain Bee is held annually at McMaster University. Neuroscience educators formed a Faculty for Undergraduate Neuroscience (FUN) in 1992 to share best practices and provide travel awards for undergraduates presenting at Society for Neuroscience meetings. Neuroscientists have also collaborated with other education experts to study and refine educational techniques to optimize learning among students, an emerging field called educational neuroscience.
Cell membranes are generally impermeable to charged or large, polar molecules because of the lipophilic fatty acyl chains comprising their interior. Many biologically important molecules, including a number of pharmaceutical agents, are organic weak acids that can cross the membrane in their protonated, uncharged form but not in their charged form (i.e., as the conjugate base). For this reason the activity of many drugs can be enhanced or inhibited by the use of antacids or acidic foods. The charged form, however, is often more soluble in blood and cytosol, both aqueous environments. When the extracellular environment is more acidic than the neutral pH within the cell, certain acids will exist in their neutral form and will be membrane soluble, allowing them to cross the phospholipid bilayer. Acids that lose a proton at the intracellular pH will exist in their soluble, charged form and are thus able to diffuse through the cytosol to their target. Ibuprofen, aspirin and penicillin are examples of drugs that are weak acids.
Sources: en.wikipedia.org
It is not approved as a pharmaceutical in major markets and is used mainly as a cosmetic ingredient and a laboratory reagent. Regulatory status varies by country and by the product category in which it appears. Claims about therapeutic effects should be treated separately from permitted cosmetic labeling.
Reversed-phase high-performance liquid chromatography and mass spectrometry are common for the peptide portion. Copper content is usually determined by inductively coupled plasma techniques or by spectrophotometry. Ultraviolet-visible spectroscopy takes advantage of the visible absorption band of the copper complex.
Light, oxygen, and elevated temperature promote degradation of the peptide, and strongly acidic or alkaline conditions accelerate hydrolysis. The copper complex is generally more resistant to oxidation than the free peptide. Storage in a dry, dark, cold environment limits loss over time.
It is the copper(II) complex of the tripeptide glycyl-L-histidyl-lysine, a sequence of three amino acids. The copper ion is held by the histidine imidazole, the terminal amino group, and an amide nitrogen. The bound form is distinct from the free peptide in charge, color, and stability.