This is a working overview of metal chelation, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-07-15 and is reviewed periodically as new material appears.
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.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide binds copper through its histidine imidazole nitrogen, its terminal amino group, and a deprotonated amide nitrogen, creating a stable chelate ring. The resulting complex carries a distinctive blue to blue-violet color, which arises from copper d-d electronic transitions. In the solid state it is usually handled as a powder, while in solution the complex can dissociate and re-form depending on pH and competing ligands. The name copper tripeptide-1 is widely used in ingredient listings.
The tripeptide was first isolated from a human plasma filtrate in 1973 during studies of tissue repair factors. Later work detected the free peptide and its copper complex in saliva, urine, and wound fluid, suggesting a natural role in tissue remodeling. Plasma concentrations reported in early literature decline with age, a pattern often cited in discussions of skin aging. Whether these endogenous levels are directly functional or largely incidental remains an open question. The peptide sequence is conserved across mammalian species.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Gly-His-Lys | Three amino acids, histidine in the middle |
| Complex formula | C14H22CuN6O4 | One copper(II) ion per peptide |
| Molar mass (complex) | approx. 402.9 g/mol | Depends on counterion and hydration state |
| Appearance | Blue to blue-violet solid | Colour arises from copper coordination |
| Common synonyms | Copper tripeptide-1, GHK-Cu | Naming varies between disciplines |
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.
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.
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.
== SELEX variants and alternative aptamer selection methods == FRELEX was developed in 2016 by NeoVentures Biotechnology Inc to allow the selection of aptamers without immobilizing the target or the oligonucleotide library. Immobilization is a necessary component of SELEX; however, it has the potential to inhibit key epitopes, and thus weaken the likelihood of successful binding, particularly when working with small molecules. FRELEX follows a similar overall methodology to SELEX; however, instead of immobilizing the target, the researcher introduces a series of random and blocker oligonucleotides to an immobilization field before introduction to the target. This allows the researcher to better target small molecules that may be lost during partitioning. It also can be used in some circumstances to select an aptamer library without knowing the target. Most modern aptamer selection methods strive to improve the conventional SELEX aptamer search method. Despite the publication of various methods aimed at increasing the affinity and specificity of aptamers, experimental approaches face limitations in the number and variety of sequences that can be examined and selected. Library capacity for SELEX experiments is practically limited to 1015 candidates, whereas, assuming there is a 4-monomeric repertoire from which pools can be created, there are ~1.6 × 1060 unique sequences in sequence space limited to a 100-residue matrix, which is clearly beyond experimental capabilities.
Once a nucleic acid sequence has been obtained from an organism, it is stored in silico in digital format. Digital genetic sequences may be stored in sequence databases, be analyzed (see Sequence analysis below), be digitally altered and be used as templates for creating new actual DNA using artificial gene synthesis.
Therefore, the shape of the open surface of a fluid equals the equipotential plane of the applied outer conservative force field. Let the z-axis point downward. In this case the field is gravity, so Φ = −ρfgz where g is the gravitational acceleration, ρf is the mass density of the fluid. Taking the pressure as zero at the surface, where z is zero, the constant will be zero, so the pressure inside the fluid, when it is subject to gravity, is
Sources: en.wikipedia.org
Epilogue: After Sally and Ollie's chapters have been completed, the player can choose one of two endings: either Arthur departs Wellington Wells for the mainland and continues his search for Percy, or takes a memory-destroying pill and rejoins the populace in their ignorance. If Arthur continues to the mainland, he encounters an impoverished young child complaining about the rainy weather, indicating other towns in England did not follow the path Wellington Wells did.
For Bukele to run for president with Nuevas Ideas, he was required to register the party with the Supreme Electoral Court (TSE). Although Nuevas Ideas had enough signatures to register, Bukele believed that the TSE would not register the party before the 29 July 2018 presidential nomination deadline. Bukele registered as a member of Democratic Change and sought the party's presidential nomination before the deadline, but the TSE canceled the party's registration four days before the deadline because Democratic Change failed to receive over 50,000 votes during the 2015 legislative elections. On 29 July 2018, Bukele registered with the right-wing Grand Alliance for National Unity (GANA) and received the party's presidential nomination. He selected Félix Ulloa, a lawyer, as his vice-presidential candidate. Bukele used social media such as Facebook, Instagram, and Twitter extensively throughout his campaign to communicate with his supporters. He did not attend either of the two presidential debates, in December 2018 and January 2019, despite saying that he would attend, claiming that the debate rules were not explained to him. Bukele was the election's front-runner, leading virtually every poll by a substantial margin. His three opponents were ARENA's Carlos Calleja, a businessman who owned the Super Selectos supermarket chain; the FMLN's former minister of foreign affairs Hugo Martínez, and Vamos' Josué Alvarado, a businessman. On election day, 3 February 2019, Bukele defeated Calleja, Martínez, and Alvarado with 53.1 percent of the vote.
In college basketball, the NCAA Division I men's and women's tournaments will expand to 76 teams beginning next year. The Pentagon releases declassified documents about UFOs and extraterrestrial life. May 10 – Six people are found dead inside a boxcar on a Union Pacific freight train in Laredo, Texas. May 12 2025–2026 United States redistricting: The Republican-led South Carolina Senate rejects redistricting efforts to redraw the congressional districts in South Carolina, including efforts to eliminate the seat represented by congressman Jim Clyburn. American autonomous driving technology company Waymo recalls 3,800 robotaxis over risks that they could enter flooded areas.
{\displaystyle {\begin{array}{rcl}\\{\ce {^{3}_{1}H}}&{\ce {->[12.32\ {\ce {y}}]}}&{\ce {{^{3}_{2}He}+e^{-}}}\\{\ce {^{4}_{1}H}}&{\ce {->[139\ {\ce {ys}}]}}&{\ce {{^{3}_{1}H}+{^{1}_{0}n}}}\\{\ce {^{5}_{1}H}}&{\ce {->[86\ {\ce {ys}}]}}&{\ce {{^{3}_{1}H}+{2_{0}^{1}n}}}\\{}\end{array}}}
Sources: en.wikipedia.org
Betaine transporter (SLC6A12) InterPro: IPR002983 Creatine transporter (SLC6A8) InterPro: IPR002984 Dopamine neurotransmitter transporter (SLC6A3) InterPro: IPR002436 Inebriated neurotransmitter transporter InterPro: IPR002944 GABA neurotransmitter transporter GAT-1 (SLC6A1) InterPro: IPR002980 GABA neurotransmitter transporter GAT-2 (SLC6A13) InterPro: IPR002981 GABA neurotransmitter transporter GAT-3 (SLC6A11) InterPro: IPR002982 Glycine neurotransmitter transporter, type 1 (SLC6A9) InterPro: IPR003028 Noradrenaline neurotransmitter transporter (SLC6A2) InterPro: IPR002435 Orphan neurotransmitter transporter (SLC6A15) InterPro: IPR002438 Serotonin (5-HT) neurotransmitter transporter, N-terminal (SLC6A4) InterPro: IPR013086 Taurine transporter (SLC6A6) InterPro: IPR002434
=== Relation to acupuncture === The debated distinction between dry needling and acupuncture has become a controversy because it relates to an issue of scope of practice of various professions. Acupuncturists claim that dry needling is a form of acupuncture that does not fall in the scope of physical therapists, chiropractors, or the majority of other healthcare professionals; whereas those healthcare professionals claim dry needling is not acupuncture, but rather a procedure that is rooted in biomedical modern sciences. Becoming a certified acupuncturist requires hundreds of hours spent in educational programs, national-level exams, and good professional standing. On the other hand, to be certified in dry needling requires continued education or a certification program that is not yet regulated with strict standards; in addition, there is a general lack of policymakers, evaluation systems, or healthcare standards governing the technique of dry needling. Many physical therapists and chiropractors have asserted that they are not practicing acupuncture when dry needling; however, much of dry needling research has been done concerning acupuncture. They assert that much of the basic physiological and biomechanical knowledge that dry needling utilizes is taught as part of their core physical therapy and chiropractic education and that the specific dry needling skills are supplemental to that knowledge and not exclusive to acupuncture.
Countercurrent exchange is a mechanism between two flowing bodies flowing in opposite directions to each other, in which there is a transfer of some property, usually heat or some chemical. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. For example, in a distillation column, the vapors bubble up through the downward flowing liquid while exchanging both heat and mass. It occurs in nature and is mimicked in industry and engineering. It is a kind of exchange using counter flow arrangement. The maximum amount of heat or mass transfer that can be obtained is higher with countercurrent than co-current (parallel) exchange because countercurrent maintains a slowly declining difference or gradient (usually temperature or concentration difference). In cocurrent exchange the initial gradient is higher but falls off quickly, leading to wasted potential. For example, in the adjacent diagram, the fluid being heated (exiting top) has a higher exiting temperature than the cooled fluid (exiting bottom) that was used for heating. With cocurrent or parallel exchange the heated and cooled fluids can only approach one another. The result is that countercurrent exchange can achieve a greater amount of heat or mass transfer than parallel under otherwise similar conditions. Countercurrent exchange when set up in a circuit or loop can be used for building up concentrations, heat, or other properties of flowing liquids.
Sources: en.wikipedia.org
The peptide is glycyl-L-histidyl-L-lysine, a three-amino-acid sequence commonly abbreviated GHK. It binds a single copper(II) ion under typical laboratory conditions. The free peptide and the copper complex are separate chemical species with different properties.
The sequence was identified in human plasma in 1973. Early work examined its presence in blood and its proposed role in tissue repair. The copper-binding property was characterized afterward and became the focus of much later research.
The tripeptide has been measured in human plasma and other biological fluids. Whether it circulates mainly as the copper complex or as the free peptide remains an open question. Natural concentrations are low and difficult to measure reliably.
It is a complex of the tripeptide glycyl-L-histidyl-L-lysine with a copper(II) ion. The peptide coordinates the metal through its histidine, amino terminus, and an amide nitrogen. It is often listed simply as copper tripeptide-1.