The short version of copper tripeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-29. Anything still debated is marked as such rather than presented as settled.
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.
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 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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22CuN6O4 as the complex | Free peptide is C14H24N6O4 |
| Molecular weight | About 402 g/mol | Free peptide is about 340 g/mol |
| Appearance | Blue solid or blue solution | Color from copper d-d transitions |
| Solubility class | Water-soluble; poor in nonpolar solvents | Ionic character favors aqueous media |
| Common synonyms | Copper tripeptide-1; glycyl-L-histidyl-L-lysine copper | INCI listing uses copper tripeptide-1 |
Aqueous GHK-Cu solutions are less stable than the dry powder. Light, dissolved oxygen and elevated temperature all accelerate loss of the intact complex, and the main observable changes are fading of the blue colour and the appearance of peptide fragments. Acidic conditions protonate the histidine imidazole and weaken copper binding, while strongly alkaline conditions promote hydrolysis of the peptide backbone. Because several degradation routes operate at once, a single shelf-life figure does not describe all storage conditions.
Solid material is typically kept as a lyophilised powder in a sealed, light-protected container at minus 20 degrees Celsius, with desiccant where humidity is high. Working solutions are often prepared fresh, aliquoted and frozen to avoid repeated freeze-thaw cycles. Glassware and buffers are checked for trace metal contamination, since other transition metals can displace copper. Records of lot number, reconstitution date and storage temperature help trace unexpected colour changes. Blue colour itself is not a reliable purity test, because partly degraded solutions can remain visibly coloured.
Dry material is typically held at low temperature, often around minus twenty degrees Celsius, and protected from moisture and light. Copper complexes can release their metal ion under acidic conditions or in the presence of competing chelators. Hydrolysis of the peptide backbone is a slower but real pathway, and the histidine residue is susceptible to oxidation over long periods. Stability statements therefore depend on formulation, pH, and container, and they should be read as conditional rather than absolute.
Identity and purity are usually assessed with reversed-phase high-performance liquid chromatography, often paired with mass spectrometry. Copper content is measured separately by techniques such as inductively coupled plasma mass spectrometry or atomic absorption. Amino acid analysis confirms the peptide sequence after hydrolysis. Because the metal and the peptide can be quantified independently, a complete certificate of analysis normally reports both values rather than a single purity figure. This separation of measurements is important when comparing suppliers.
Solid GHK-Cu appears as a blue to blue-violet powder, and the colour is a direct consequence of copper coordination. The complex dissolves readily in water and in many polar solvents, while the free peptide behaves differently. Solubility in nonpolar media is low, which limits its use in oil-based systems. Solutions are typically prepared fresh because the dissolved form is more exposed to hydrolysis and to loss of the metal ion than the dry powder. Working concentrations are usually low, and preparation notes often specify the solvent and the order of addition.
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.
Practical handling notes centre on limiting exposure to water, oxygen, and repeated temperature cycling. Weighed powder is often equilibrated to room temperature before opening to avoid condensation on the solid. Working solutions are typically divided into single-use aliquots and frozen rather than stored refrigerated for long periods. Reported shelf lives vary widely between laboratories, and no single set of conditions is universally treated as a reference standard, which complicates direct comparison of published stability figures.
Solutions of GHK-Cu respond strongly to pH, redox conditions, and the presence of competing chelators such as EDTA. Below roughly pH 4 the copper tends to dissociate, because the amide nitrogen donors become protonated and can no longer coordinate. Strongly alkaline conditions instead favour hydrolysis and precipitation of copper hydroxide. Dissolved oxygen and light accelerate breakdown of the peptide backbone, and the copper released during that process can catalyse further oxidation, so dry, cold, dark storage is the usual recommendation.
== Literatur == Friedrich Lottspeich, Haralabos Zorbas: Bioanalytik. Spektrum Akademischer Verlag, Heidelberg 1998, ISBN 3-8274-0041-4. Hubert Rehm, Thomas Letzel: Der Experimentator: Proteinbiochemie / Proteomics. 6. Auflage. Spektrum Akademischer Verlag, Heidelberg 2009, ISBN 978-3-8274-2312-2.
Der Strep-tag II ist ein Protein-Tag, der die Reinigung und Detektion von rekombinanten Proteinen mittels Affinitätschromatographie ermöglicht. Es handelt sich dabei um ein synthetisches Peptid, welches aus 8 Aminosäuren besteht und N- oder C-terminal mit einem Fusionsprotein exprimiert werden kann. Der Strep-tag II weist eine starke Affinität zu Strep-Tactin auf, welches für die Reinigung der Fusionsproteine über Affinitätschromatographie-Säulen genutzt wird. Die Elution der Strep-tag-II-Fusionsproteine erfolgt bei dieser Methode durch die Zugabe eines Biotin-Derivates, welches mit dem Strep-tag II kompetiert. Ein Vorteil des Strep-tags sind die milden physiologischen Bedingungen, unter denen die Proteinreinigung stattfindet. Aufgrund dessen eignet sich das Strep-tag System besonders für die Expression bioaktiver, funktionsfähiger Proteine. Strep-tag, Twin-Strep-tag und Strep-Tactin sind eingetragene Marken der IBA Lifesciences GmbH.
== Herkunft des Strep-tags == Als Basis der Entwicklung des Strep-tags diente die bereits lange bekannte Bindung zwischen Streptavidin und Biotin (Vitamin H). Bei Streptavidin handelt es sich um ein Protein aus dem Bakterium Streptomyces avidinii, welches aus vier identischen Untereinheiten besteht. Jede dieser Untereinheiten kann ein Molekül Biotin binden. Diese Bindung ist hoch affin und stellt eine der stärksten bekannten, nicht-kovalenten Bindungen dar. Aufgrund dieser Eigenschaft findet Streptavidin häufig Anwendung in der Molekularbiologie, Biotechnologie und Biochemie. Bei dem Strep-tag handelt es sich um ein Peptid, welches für die Bindung in der Biotin-Bindetasche von Streptavidin entwickelt wurde, um als Tool für die rekombinante Proteinreinigung dienen zu können. Die spätere Weiterentwicklung ist der Strep-tag II (Trp-Ser-His-Pro-Gln-Phe-Glu-Lys), dieser zeichnet sich wiederum durch eine verbesserte Bindung an Strep-Tactin – eine veränderte Streptavidin-Variante – aus. Die Affinität des Strep-tag II zu Strep-Tactin ist etwa 10-fach höher als die zu Streptavidin. Das so optimierte Strep-tag System, bestehend aus Strep-tag II und Strep-Tactin, hat sich als äußerst nützlich für die Isolation von funktionsfähigen Proteinen und Proteinkomplexen, sowie deren Nachweis im Rahmen von Proteom-Studien erwiesen.
== Das Prinzip des Strep-tag Systems == Der Strep-tag wird durch Klonierung, vor oder hinter die Gensequenz des gewünschten Proteins, in einen Vektor eingebracht, wodurch bei der Expression ein Fusionsprotein mit N- oder C-terminalem Strep-tag II entsteht. Für die Expression sind Vektoren für verschiedene Wirtsorganismen verfügbar. Neben Vektoren für die Expression in E. coli sind auch solche für Hefen, sowie für Insekten- und Säugerzellen verfügbar. Da der Strep-tag II nur eine geringe Größe aufweist und biochemisch nahezu inert ist, beeinflusst er weder die Proteinfaltung noch die Sekretion und wirkt sich nicht auf die Funktion des Proteins aus. Ein weiterer Vorteil ist, dass die Reinigungsschritte unter physiologischen Bedingungen durchgeführt werden können, was die Herstellung biologisch aktiver Proteine gewährleistet und die Aufreinigung von funktionalen Proteinkomplexen erlaubt. Ein Vergleich mit anderen Protein-Tags zeigte für den Strep-tag II eine sehr hohe Reinheit (>95 %) und eine hohe Ausbeute an gereinigtem Protein. Die Reinigung von Strep-tag II-Fusionsproteinen beginnt damit, dass das Zelllysat mit dem Fusionsprotein auf eine Säule mit immobilisiertem Strep-Tactin aufgetragen wird. Das Fusionsprotein bindet daraufhin an Strep-Tactin. Es folgt ein Waschschritt, bei dem mit einem physiologischen Puffer (z. B. PBS) alle nicht gebundenen Proteine von der Säule gewaschen werden. Danach erfolgt die Elution des Fusionsproteins mit einer geringen Konzentration von Desthiobiotin, einem Analogon von Biotin, dem natürlichen Liganden von Streptavidin.
Sources: de.wikipedia.org
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.
Copper(II) complexes absorb light in the red part of the visible spectrum, so transmitted light appears blue. The absorption arises from electronic transitions within the copper d-orbitals, which are split by the surrounding ligands. The intensity and exact wavelength shift somewhat with pH, solvent, and ligand arrangement.
The free peptide and the copper-bound complex are studied as separate species and do not always behave the same way in assays. Some reported responses are attributed to copper delivery, while others are attributed to the peptide sequence itself. Which fraction drives a given observation is often unresolved in the published work.
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.