lyophilized powder comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-05-27. Numbers and descriptions here follow the published literature rather than marketing material.
GHK-Cu is the copper-binding complex formed by the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The free peptide is usually written as GHK, and the complex is written as GHK-Cu or Cu-GHK. The sequence was identified in human plasma and later detected in saliva and urine. Its name comes from the single-letter codes of glycine, histidine and lysine. The complex is widely described as a naturally occurring carrier of copper in blood rather than as a free peptide with its own hormonal role.
Copper binds to the peptide through the histidine imidazole nitrogen and the terminal amino group, forming a stable square-planar complex. Binding constants reported for copper(II) with GHK are high, so the peptide competes effectively for copper in solution. The complex absorbs visible light, which gives solutions a blue to violet colour. Whether the metal-free peptide has a distinct biological function of its own is still an open question; some work treats it mainly as a copper delivery vehicle, while other work reports peptide-specific effects.
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.
| Property | Value | Notes |
|---|---|---|
| Sequence | Gly-His-Lys | Three amino acids; histidine supplies the main copper-binding nitrogen |
| Bound metal | Copper(II) | Coordination is described as square-planar around the metal centre |
| Appearance | Blue to violet solid | Colour originates from copper d-d electronic transitions |
| Solubility class | Freely soluble in water | Aqueous solutions are often slightly acidic |
| Common synonyms | Copper tripeptide, Cu-GHK | Ingredient lists may say only 'copper peptide' without giving the sequence |
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.
Stability of GHK-Cu is influenced by light, oxygen, moisture, pH, and temperature. Solid material is generally kept desiccated and frozen to reduce hydrolysis and oxidation, while aqueous solutions are best prepared fresh or stored cold in aliquots. Repeated freeze-thaw cycles can promote aggregation, precipitation, or peptide degradation. Copper coordination may change under strongly acidic or alkaline conditions, potentially altering the complex's spectroscopic properties. Published long-term stability data for specific matrices, such as cosmetic emulsions or biological buffers, are limited, so shelf-life claims should be treated as formulation-specific rather than universal.
Quality control for GHK-Cu relies on documentation and independent testing rather than a single accepted standard. A certificate of analysis may report peptide purity, copper content, residual solvents, water content, and microbial limits, but the underlying methods and acceptance criteria vary by supplier. Verification can include mass confirmation, amino acid analysis, and comparison with a reference standard when one is available. Open questions include how different copper-binding modes or peptide isomers affect measured activity and whether conventional purity assays capture those differences. Buyers of research-grade material typically need to request raw data rather than rely solely on a summary certificate.
The reaction pathway of this enzyme is key in regulating the synthesis and degradation of collagen, a vital protein necessary for multiple aspects of the body. Irregular levels of serum prolidase in the blood are indicative of various diseases and conditions in humans. Deficiency in prolidase leads to a rare, severe autosomal recessive disorder (prolidase deficiency) that causes many chronic, debilitating health conditions in humans. These phenotypical symptoms vary and may include skin ulcerations, mental retardation, splenomegaly, recurrent infections, photosensitivity, hyperkeratosis, and unusual facial appearance. Furthermore, prolidase activity was found to be abnormal compared to healthy levels in various medical conditions including but limited to: bipolar disorder, breast cancer, endometrial cancer, keloid scar formation, erectile dysfunction, liver disease, lung cancer, hypertension, melanoma, and chronic pancreatitis. In some cancers with increased levels of prolidase activity, such as melanoma, the differential expression of prolidase and its substrate specificity for dipeptides with proline at the carboxyl end suggests the potential of prolidase in becoming a viable, selective endogenous enzyme target for proline prodrugs. Serum prolidase enzyme activity is also currently being explored as a possible, reliable marker for diseases including chronic hepatitis B and liver fibrosis.
==== Visible from the front or above ==== Frontal suture / Metopic suture – between the two frontal bones, prior to the fusion of the two into a single bone Sagittal suture – along the midline, between parietal bones
=== Other === Some evidence indicates that plasmapheresis (therapeutic plasma exchange) can be used to treat the systemic form of scleroderma. In Italy, it is a government-approved treatment option. This is done by replacing blood plasma with a fluid consisting of albumin, and is thought to keep the disease at bay by reducing the circulation of scleroderma autoantibodies.
Thirdly and most importantly, IUPAC rejected the name seaborgium for element 106, having just approved a rule that an element could not be named after a living person, even though the IUPAC had given the LBNL team the sole credit for its discovery. In 1997, IUPAC renamed elements 104 to 109, and gave elements 104 and 106 the Berkeley proposals rutherfordium and seaborgium. The name dubnium was given to element 105 at the same time. The 1997 names were accepted by researchers and became the standard.
Sources: en.wikipedia.org
Joost Hiltermann of Foreign Policy wrote that whatever little material support the Houthis may have received from Iran, the intelligence and military support by US and UK for the Saudi Arabian-led coalition exceed that by many factors. In April 2015, the United States National Security Council spokesperson Bernadette Meehan remarked that "It remains our assessment that Iran does not exert command and control over the Houthis in Yemen". Joost Hiltermann wrote that Iran does not control the Houthis' decision-making as evidenced by Houthis' flat rejection of Iran's demand not to take over Sanaa in 2015. Thomas Juneau, writing in the journal, International Affairs, states that even though Iran's support for Houthis has increased since 2014, it remains far too limited to have a significant impact in the balance of power in Yemen. The Quincy Institute for Responsible Statecraft argues that Teheran's influence over the movement has been "greatly exaggerated" by "the Saudis, their coalition partners (mainly the United Arab Emirates), and their [lobbyists] in Washington." Similarly, academics such as Marieke Brandt and Charles Schmitz have stated that the allegation that the Houthis are merely an Iranian proxy force has its roots in political narratives by Saleh, Saudi Arabia, the United States and other anti-Houthi forces. While the Houthis have praised post-Islamic Revolution Iran for its opposition to American and Israeli imperialism in the Middle East, they have also criticized Iranian political and religious doctrine, including Iran's state religion of Twelver Shi'ism.
=== Patient and public involvement === Besides being participants in a clinical trial, members of the public can be actively collaborate with researchers in designing and conducting clinical research. This is known as patient and public involvement (PPI). Public involvement involves a working partnership between patients, caregivers, people with lived experience, and researchers to shape and influence what is researched and how. PPI can improve the quality of research and make it more relevant and accessible. People with current or past experience of illness can provide a different perspective than professionals and compliment their knowledge. Through their personal knowledge they can identify research topics that are relevant and important to those living with an illness or using a service. They can also help to make the research more grounded in the needs of the specific communities they are part of. Public contributors can also ensure that the research is presented in plain language that is clear to the wider society and the specific groups it is most relevant for.
=== Enzyme activity === An enzyme's name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase. Examples are lactase, alcohol dehydrogenase and DNA polymerase. Different enzymes that catalyze the same chemical reaction are called isozymes. The International Union of Biochemistry and Molecular Biology have developed a nomenclature for enzymes, the EC numbers (for "Enzyme Commission"). Each enzyme is described by "EC" followed by a sequence of four numbers which represent the hierarchy of enzymatic activity (from very general to very specific). That is, the first number broadly classifies the enzyme based on its mechanism while the other digits add more and more specificity. The top-level classification is:
== Biography == Jerome Gross was born in New York City on February 25, 1917. In 1939, he graduated from the Massachusetts Institute of Technology. While his scientific interests included astronomy and biology, he chose a career in medicine. He subsequently attended the New York University College of Medicine. After a year as an intern at Long Island College Hospital, he served two years in the Army Medical Corps. Gross believed that clues to diseases such as rheumatic fever would be found in the molecular structure and biology of connective tissue. He returned to M.I.T. to join the laboratory of Francis O. Schmitt as a Research Associate, where he began research on structural macromolecules utilizing chemical and electron microscopical methods. Despite many important observations on hyaluronic acid and elastin, he chose to focus on collagen. He was attracted to Harvard Medical School and the Massachusetts General Hospital by Walter Bauer, who thought that many of the secrets of rheumatoid arthritis and rheumatic fever could be uncovered by similar methods. Gross's pioneering findings that collagen molecules could be extracted from tissues using solutions of neutral salt or dilute acid and reconstituted into various structures opened up the field of collagen research. Gross then began to study collagen structure in animal models of human wound healing. In the late 1950s, he became interested in lathyrism and, with Charles Levene, made the critical observations that lathyrism resulted from abnormal aggregation and defective cross-linking of collagen molecules.
Streptococcus agalactiae (also known as group B streptococcus or GBS) is a gram-positive coccus (round bacterium) with a tendency to form chains (as reflected by the genus name Streptococcus). It is a beta-hemolytic, catalase-negative, and facultative anaerobe. S. agalactiae is the most common human pathogen of streptococci belonging to group B of the Rebecca Lancefield classification of streptococci. GBS are surrounded by a bacterial capsule composed of polysaccharides (exopolysaccharide). The species is subclassified into ten serotypes (Ia, Ib, II–IX) depending on the immunologic reactivity of their polysaccharide capsule. The plural term group B streptococci (referring to the serotypes) and the singular term group B streptococcus (referring to the single species) are both commonly used synonymously with S. agalactiae even though S. halichoeri and S. pseudoporcinus are also group B Streptococcus. These species test positive as group B, but are not frequently carried by humans and only rarely cause disease.
Sources: en.wikipedia.org
==== Increased limit for tax deductions for state and local taxes ==== From January 1, 2025, to December 31, 2029, individuals may take a tax deduction for up to $40,000 of state and local taxes ($20,000 if married filing separately), which is an increase from $10,000 previously. There is a reduction to the limit for the tax deduction for individuals whose modified adjusted gross income is over $500,000 ($250,000 for married filing separately) but it never goes below $10,000. This provision has an estimated cost of $142 billion. Republican representatives Elise Stefanik, Mike Lawler, Nick LaLota, and Andrew Garbarino of New York, Representative Young Kim of California, and Representative Tom Kean Jr. of New Jersey cut this deal with House speaker Mike Johnson in exchange for their votes.
It noted that TikTok had implemented positive measures, such as forbidding direct messaging for users younger than 16 and allowing their parents to manage privacy settings directly through a paired family account, but the risk of children pretending to be older when creating their account remains. TikTok raised the minimum age for livestreaming from 16 to 18 after a BBC News investigation found hundreds of accounts going live from Syrian refugee camps. Thirty of them showed children begging for digital donation. TikTok reportedly made as much as a 70% commission on some of them, a figure that the company disputed. In March 2024, the Italian Competition Authority fined TikTok €10 million for not protecting underage users adequately from harmful content such as the "French scar" challenge, which left heavy pinch marks on a person's cheeks. On 30 December 2024, Venezuela's Supreme Court fined TikTok $10 million over viral challenges that authorities say led to the deaths of three children. The court cited TikTok's negligence in failing to implement "necessary and adequate measures" to prevent the viral video challenges.
Beta-secretase 1, also known as beta-site amyloid precursor protein cleaving enzyme 1, beta-site APP cleaving enzyme 1 (BACE1), membrane-associated aspartic protease 2, memapsin-2, aspartyl protease 2, and ASP2, is an enzyme that in humans is encoded by the BACE1 gene. Expression of BACE1 is observed mainly in neurons and oligodendrocytes. BACE1 is an aspartic acid protease important in the formation of myelin sheaths in peripheral nerve cells: in mice the expression of BACE1 is high in the postnatal stages, when myelination occurs. The transmembrane protein contains two active site aspartate residues in its extracellular protein domain and may function as a dimer, its cytoplasmic tail is required for the correct maturation and an efficient intracellular trafficking, but does not affect the activity. It is produced as a pro-enzyme, the endoproteolitc removal occurs after BACE leaves endoplasmic reticulum, in the Golgi apparatus. In addition the pro-peptide receives additional sugars to increase the molecular mass. and the tail became a palmitoylated. The BACE1 expression is influenced by the inflammatory state: during AD the cytokines reduce the PPAR1 an inhibitor of BACE1 mRNA.
The South African Defence Force (SADF) (Afrikaans: Suid-Afrikaanse Weermag) comprised the armed forces of South Africa from 1957 until 1994. Shortly before the state reconstituted itself as a republic in 1961, the former Union Defence Force was officially succeeded by the SADF, which was established by the Defence Act (No. 44) of 1957. The SADF, in turn, was superseded by the South African National Defence Force in 1994.
Sources: en.wikipedia.org
The letters GHK are the one-letter codes for glycine, histidine and lysine, the three amino acids in the peptide. The suffix Cu indicates that the peptide is bound to a copper ion, normally copper(II).
The free tripeptide and its copper complex have been measured in human plasma, saliva, urine and some tissue extracts. Reported concentrations vary widely between studies, and the role of the complex in normal physiology remains partly unresolved.
The plain peptide lacks the metal, so its charge, colour and binding behaviour differ. The copper complex is blue and carries a bound copper ion, while the metal-free form is colourless and has different solution chemistry.
Lyophilized material is normally held at about minus twenty degrees Celsius in a sealed, desiccated vial. Dissolved samples are less durable and are prepared fresh. Repeated freeze-thaw cycles are avoided.