To understand an article about peptides, it helps to distinguish the amino acids, their sequence and the shape the chain takes. The next questions concern which sample was examined, in which model and by which method.
This article covers the chemistry, how research peptides are made and analysed, the research fields they are used in, how they are regulated, peptides in skincare and what “Research Use Only” means at ArcticAmino. Short answers to the most common questions are at the end.
Amino acids form a chain
An amino acid has chemical groups that allow it to bond with other amino acids. In a typical peptide chain, the carboxyl group of one amino acid is linked to the amino group of the next. The bond between them is an amide bond called a peptide bond. Once an amino acid forms part of the chain, it is called an amino acid residue.
Two linked amino acids form a dipeptide. Three form a tripeptide. GHK is an example of a named tripeptide sequence: glycine, histidine and lysine. The letters identify the amino acids in a particular order. GHK-Cu denotes a copper complex of this sequence, so the addition of Cu is part of its chemical identity.
The diagram shows only the principle of a chain. It does not show the full molecular structure, relative sizes or how a particular peptide behaves in a biological sample.
Amino acids linked by peptide bonds
Where is the boundary with proteins?
The terms overlap. IUPAC defines polypeptides as peptides containing ten or more amino acid residues. Biological literature also uses other practical size thresholds. A rule that every chain below a certain length is a peptide and every chain above it is a protein would therefore be too categorical.
Proteins consist of one or more polypeptide chains. The amino acid sequence is the primary structure; local folding patterns and the overall three-dimensional shape describe other levels of structure. Shape affects which molecules a protein can bind and which tasks it can perform.
The number of amino acids is therefore just one piece of information. A short sequence, a long chain and a folded protein may require different analyses, even though they all contain peptide bonds.
| Term | What it describes | What it does not determine |
|---|---|---|
| Amino acid | A chemical component that can form part of a chain | The function of the chain it forms part of |
| Peptide | Amino acids linked by peptide bonds | Medical efficacy or approval |
| Polypeptide | A chain of multiple amino acid residues | A single, unambiguous biological function |
| Protein | One or more polypeptide chains with a specific structure | Whether every isolated sample has the same properties |
The same building blocks can form different substances
Order matters. A list of amino acids is not enough to identify a peptide; its sequence must also be known. Other structural information may be needed, such as whether the chain has modified ends or bonds that constrain parts of its structure.
The same applies when a trade name appears in several publications. Before comparing results, check whether the name refers to the same compound and the same form. A result for one molecule cannot simply be transferred to a related fragment.
In a certificate of analysis, identity and purity are different questions. Identity concerns which substance the sample contains. Purity concerns the sample's composition as measured by a specified method. Both are needed to assess a research material.
How research peptides are made and analysed
Research peptides are usually produced by chemical synthesis. The amino acids are coupled one at a time in the order the sequence requires, often while the chain is attached to a solid-phase support. The chain is then released, purified and dried, usually to a freeze-dried powder. EMA's guideline on synthetic peptides describes this type of manufacture and the impurities it can produce, such as chains that lack one amino acid.
The analyses answer different questions. HPLC separates the components of the sample and is used to state purity as a share of the measured signal. LC-MS links mass information to the peaks and is used to assess identity. Content, meaning how much peptide a vial actually contains, requires a separate quantitative method. A high purity figure therefore does not on its own say how much peptide the sample contains, and it says nothing about sterility.
The results are collected in a certificate of analysis, a COA, for the individual batch. The certificate applies to the sample the laboratory received and the methods stated. ArcticAmino sends a copy of the batch's certificate on request before ordering. How to read such a document, and what HPLC and LC-MS can and cannot show, is described in separate articles.
What are research peptides used for in laboratories?
Peptides are studied in cell cultures, in animal models and in clinical trials, depending on the compound and the question. Many peptides resemble signalling substances the body makes itself, and the studies often examine how a particular signalling pathway responds when the peptide is added. The model used determines what the result can tell us. A finding in cultured cells is not the same as a finding in humans.
The categories in ArcticAmino's catalogue follow the research fields the studies belong to, not an effect of the product. None of the categories says anything about efficacy, safety or lawful use; they are a way of finding one's way in the literature, and the peptide guide describes for each name which models were used, how many studies were found and what they measured. These are the categories:
- Weight loss: including retatrutide, tirzepatide and cagrilintide, studied in models of appetite and metabolism.
- Recovery: BPC-157, TB-500 and GHK-Cu, examined in models of tissue and healing.
- Growth / GH: peptides such as tesamorelin and ipamorelin, studied in connection with the growth hormone axis.
- Cognitive: peptides such as semax, selank and DSIP, examined in studies of the nervous system.
- Skin and pigmentation: MT-1, MT-2, AHK-Cu and GLOW.
- Energy and cell health: including NAD+, glutathione and epitalon.
- Accessories: bacteriostatic water and other equipment used when a freeze-dried powder is to be dissolved for laboratory use.
Are peptides legal? Norway's rules and the rest of Europe
Peptide is a chemical term, not a legal category. In Norway, the medicines agency DMP decides whether a product is a medicine on the basis of function and presentation. In its background article of September 2026, DMP writes that peptides that are injected will almost always be classified as medicines and are illegal to import from abroad by post, whether or not they are on the doping list. Since 15 September 2026, BPC-157, CJC-1295, ipamorelin, TB-500, tesamorelin and sermorelin, together with ibutamoren, have been on Norway's criminal-law doping list, and according to DMP's guidance, importing medicines for non-medical use always requires a permit from DMP.
Those are Norway's rules. In the EU, a medicinal product is defined by presentation or function (Directive 2001/83/EC, Article 1), and whether a particular product counts as a medicine is decided nationally, case by case, by the competent authority. The word peptide or research on a label does not settle it. The rules in other European countries are the subject of a separate article.
The rules of sport are a third set of rules: WADA's 2026 Prohibited List places BPC-157 under S0, non-approved substances, and the other peptides named above under S2. This article does not determine the legality of any specific transaction.
Peptides in skincare
Peptides are used as ingredients in cosmetics, and GHK-Cu is a widely discussed example. The research behind that discussion consists largely of laboratory experiments. Maquart and colleagues reported stimulation of collagen synthesis in fibroblast cultures in 1988, and in 1992 Wegrowski, Maquart and Borel found changes in the synthesis of some glycosaminoglycans in cultured human fibroblasts, but no effect on hyaluronic acid synthesis.
Whether a peptide reaches relevant cells in intact skin is a separate question. A study published online in 2010 examined the transport and retention of copper from a GHK-Cu solution in different skin layers in a laboratory setup, and a 2008 study examined the transport of copper complexes through a model of the stratum corneum. Such experiments shed light on barriers and transport, not on whether people get a visible cosmetic improvement.
A finished cream or serum is a different material from a laboratory powder. The EU Cosmetics Regulation requires a safety assessment and a safety report for the finished product before it is placed on the market. A certificate of analysis for one raw material does not replace such an assessment, and this article gives no recipes for making such formulations. The article on GHK-Cu goes through the studies model by model.
What does “Research Use Only” mean at ArcticAmino?
“Research Use Only”, abbreviated RUO, means that the products are sold exclusively for research purposes. They are not approved for use in humans or animals, for consumption or for administration, and ArcticAmino publishes no instructions for use. Each batch can be documented with a certificate of analysis, sent on request. The certificate describes the analysed sample; it documents neither medical efficacy nor that the raw material can be used in humans.
Nor is the label a permit: which permits may be required for import, acquisition or the planned activity is a question for the national medicines agency, and the article on Norway's 2026 peptide rules shows, with Norway as the example, how the different sets of rules fit together.
When you read a product page at ArcticAmino, this means in practice: the name and CAS number identify the compound, the certificate of analysis documents the batch, and the peptide guide summarises what the studies have examined. None of these is a recommendation for use. Whether peptides are dangerous cannot be answered for the whole group of substances; what the authorities warn against is covered on a separate page.
From chemical name to research result
A study in cultured cells can examine a specific process, such as the production of a protein. Such a result describes that particular experiment. To assess its relevance, the reader also needs to know the cell type, control group and measurement method. A human study asks different questions and has different limitations.
Peptide is also not a product category that automatically permits sale or import. Norway's DMP assesses medicinal product classification based on function and presentation. A label such as research product therefore cannot by itself determine which rules apply.
First read what the compound is, then what the study measured. Finally, assess whether the result applies to the sample and question you are actually interested in. This order makes it easier to spot when a chemical definition is being used as an unsupported claim of efficacy.
Frequently asked questions
What are peptides?
Peptides are compounds in which amino acids are linked by peptide bonds. Two amino acids give a dipeptide, three a tripeptide, and IUPAC counts chains of ten or more amino acid residues as polypeptides. The term describes chemical structure, not effect, safety or legal status.
What is the difference between peptides and proteins?
The boundary is gradual. Proteins consist of one or more polypeptide chains with a specific three-dimensional structure, while short chains are called peptides. The number of amino acids is just one piece of information; sequence, shape and any modifications determine what the molecule is.
Are peptides legal?
It depends on the substance and the act. In the EU, medicines are defined by presentation or function, and whether a product is a medicine is decided nationally in the specific case. In Norway, DMP writes that peptides that are injected are almost always classified as medicines, and six named peptides have been on the criminal-law doping list since 15 September 2026. This article does not determine the legality of an individual transaction.
What are peptides used for in research?
Peptides are studied in cell cultures, animal models and clinical trials of signalling pathways, metabolism, tissue, the nervous system, skin and cell function. The categories at ArcticAmino follow these research fields. The model used determines what a result can tell us.
What are peptides in skincare?
Peptides such as GHK-Cu are used as cosmetic ingredients. The evidence is mainly cell experiments and studies of transport through skin; a finished formulation must be safety-assessed under the EU Cosmetics Regulation. A laboratory powder is not a skincare product.
What does Research Use Only mean?
That the product is sold exclusively for research purposes and is not approved for use in humans or animals. ArcticAmino sends the batch's certificate of analysis on request, but the label does not replace permits that may be required for import or acquisition.
Sources
- IUPAC Gold Book: peptides
- IUPAC Gold Book: polypeptides
- IUPAC/IUB: symbols for amino acids and peptides
- Molecular Biology of the Cell: protein structure
- Maquart et al. (1988): GHK-Cu in fibroblast cultures
- DMP: classification of medicinal products
- EMA: development and manufacture of synthetic peptides
- IUPAC Gold Book: liquid chromatography
- ICH Q2(R2): validation of analytical procedures
- Directive 2001/83/EC, Article 1: the definition of medicinal product
- DMP, 15.09.2026: new substances on the doping list
- DMP, 15.09.2026: background and health risks
- DMP: import and purchase permits for non-medical use
- WADA: 2026 Prohibited List
- Wegrowski et al. (1992): glycosaminoglycans in cell culture
- Hostynek et al. (2011; online 2010): transport in skin samples
- Study (2008): copper complexes and a stratum corneum model
- Cosmetics Regulation 1223/2009, Article 10 and Annex I
ArcticAmino sells research materials. These articles are written by the supplier and summarise sources for informational purposes. They are not medical advice or instructions for use. A certificate of analysis does not make a research material an approved medicine.