What are peptides? The complete beginner's guide

Research context (RUO): This guide explains neutrally what peptides are and which categories of research peptides exist. All peptides offered at Peplife are intended exclusively for in-vitro laboratory research (Research Use Only), not for human or animal use.

What are peptides? The complete beginner's guide

What exactly are peptides? In short, a peptide is a short chain of amino acids strung together through so-called peptide bonds. Amino acids are the building blocks of all life; link a handful together and you have a peptide. In the body, many of these chains behave as signalling molecules: they bind to receptors on cells and set off a series of reactions there. It is precisely this property that makes peptides so interesting for scientific research, and explains why research peptides have received so much attention in recent years.

What is a peptide? — amino acid chains explained

A peptide forms when two or more amino acids bind together through a condensation reaction. That bond is called a peptide bond. Scientists roughly classify the chains by length: from two to about ten amino acids they are called oligopeptides, and above twenty amino acids polypeptides. An amino acid sequence determines how the chain folds and which receptors it fits. The hormone insulin, for example, contains 51 amino acids, whereas well-known research peptides such as BPC-157 count only around fifteen.

What is the difference between a peptide and a protein?

The difference between a peptide and a protein lies mainly in length and structure. Both are built from the same amino acids and the same peptide bonds, but a peptide is shorter and usually folded less complexly. Once a chain becomes long enough and folds into a stable three-dimensional shape with a biological function, it is called a protein. The boundary is not razor-sharp: many sources place it around fifty amino acids. Put simply: every protein is built from peptide chains, but not every peptide is a protein.

How do peptides work in the body? — signalling molecules

Many peptides function as messengers. They bind with high specificity to receptors on the outside of cells and thereby activate a cascade of signals inside the cell. In this way peptide hormones regulate processes such as metabolism, blood pressure, growth and reproduction. Well-known endogenous examples are insulin and glucagon (blood sugar regulation), oxytocin and the natriuretic peptides. In scientific reviews, peptides are therefore described as hormones, growth factors, neurotransmitters or receptor ligands. Because they can bind so specifically to a single receptor, peptides can influence protein-protein interactions that are often out of reach for smaller molecular compounds.

Why are peptides interesting for research?

In science, peptides occupy a special place between classical chemical compounds and large biological drugs such as antibodies. In a review in Signal Transduction and Targeted Therapy (2022) researchers describe that there are more than 170 peptides in clinical development worldwide, spread across areas such as metabolism, oncology, cardiovascular disease and infectious diseases. Researchers cite as advantages the high target specificity, the relatively low immunogenicity and lower production costs compared with antibodies. For laboratories, research peptides therefore form an attractive model for studying cell signalling, receptor binding and metabolic pathways.

The main categories of research peptides

Research peptides are usually classified by the biological system they address in studies. Below are the main categories, each with a link to the corresponding range:

• Recovery & tissue: peptides studied in preclinical research in relation to tissue repair, tendons and inflammatory processes, such as BPC-157 and TB-500. View the recovery peptides.
• Metabolism & GLP-1: the incretin analogues such as semaglutide, tirzepatide and retatrutide, studied for glucose metabolism and fat loss. View the metabolism peptides.
• GH axis (growth hormone): growth hormone secretagogues and releasing peptides such as ipamorelin, CJC-1295 and sermorelin, studied in relation to the growth hormone axis. View the GH-axis peptides.
• Cognitive: peptides such as Semax and Selank that are linked in research to neuromodulation and the central nervous system. View the cognitive peptides.
• Skin: copper peptides and related molecules such as GHK-Cu, studied for skin and collagen processes. View the skin peptides.
• Longevity & bioregulators: peptides such as epitalon and the so-called peptide bioregulators, studied around ageing and cellular regulation. View the anti-aging peptides.

Peptides in laboratory research: handling & dissolving

Research peptides are usually supplied as a freeze-dried (lyophilised) powder in a vial. Before they can be used in an in-vitro setup, they are dissolved in the laboratory — this is called reconstitution. Which liquid is suitable for this and how purity and stability play a role is explained neutrally in the guide reconstitute peptides. For choosing the solvent there is the supplementary pillar on which liquid is suitable for dissolving a peptide.

Quality & purity

The reliability of research results depends heavily on the purity of the peptide used. Every relevant batch is independently HPLC-tested by an external laboratory; the certificate of analysis (CoA) is publicly verifiable per batch. This makes it verifiable each time which substance and which purity are actually in the vial — a basic prerequisite for reproducible laboratory research.

Frequently asked questions about peptides

What is the difference between a peptide and a protein?
Both consist of amino acids linked through peptide bonds. A peptide is shorter and simpler; a protein is longer and folds into a stable three-dimensional structure with a biological function. The boundary is often placed around fifty amino acids.

Are peptides legal?
Within the EU, research peptides are traded as laboratory chemicals for research purposes. They are not registered as a medicine and not approved for human or animal use. Purchase and possession for in-vitro research is permitted; their use outside that context falls outside it.

What does RUO mean?
RUO stands for “Research Use Only”: for research exclusively. It means a product is intended solely for in-vitro laboratory research and not for diagnostic or therapeutic use in humans or animals.

Are peptides the same as steroids?
No. Steroids are fat-like molecules with a ring structure, whereas peptides are chains of amino acids. They are chemically entirely different classes of substances that interact with the body in different ways.

How are research peptides stored?
In freeze-dried form, peptides are usually stored cool and dry; after reconstitution, refrigeration is customary to preserve stability. The precise shelf life varies per molecule and is recorded in laboratory protocols.

What are peptides studied for?
Depending on the category, researchers study peptides in relation to tissue repair, metabolism and glucose regulation, the growth hormone axis, neuromodulation, skin processes and ageing, among others — always in preclinical, in-vitro or animal models.

Read more & research at Peplife

• BPC-157 research: the repair peptide under the microscope
• Semaglutide vs tirzepatide: GLP-1 peptides compared
• Growth-hormone peptides and the GH axis
• Longevity peptides and bioregulators
• Fat-loss peptides in research
• Cognitive peptides and neuromodulation
• Reconstituting peptides: from powder to solution

Sources: Biochemistry, Peptide — StatPearls (NCBI/NIH) · Therapeutic peptides: current applications and future directions — Signal Transduction and Targeted Therapy (2022) · What Is the Difference Between a Peptide and a Protein? — Britannica

Research Use Only. All products are supplied exclusively for in vitro laboratory research. Not intended for diagnostic or therapeutic use in humans or animals, and not approved by the EMA or FDA.