What are peptides?

01

What peptides are

A peptide is a short chain of amino acids joined end-to-end by peptide bonds. Chemists usually call a chain of two to about fifty amino acids a peptide; longer chains that fold into stable three-dimensional shapes are called proteins. The boundary is a convention rather than a law of nature — peptides and proteins are made of the same building blocks and differ mainly in length and folding.

Peptides are therefore not a product, a brand or a single invention. They are a broad class of molecules found in every living organism, from bacteria to plants to people.

02

From amino acids to peptides to proteins

Living cells use twenty standard amino acids. Each has the same backbone — an amino group, a central carbon and a carboxyl group — with a different side chain that gives it its character. When the carboxyl group of one amino acid reacts with the amino group of the next, a molecule of water is released and a peptide bond forms.

Two amino acids joined this way make a dipeptide, three a tripeptide, and so on. A chain of several amino acids is an oligopeptide; tens of residues form a polypeptide; and once a polypeptide folds into a defined shape — often fifty or more residues — it is generally described as a protein. The order of the amino acids (the sequence) determines what the molecule does.

03

Where peptides occur and what they do

The body makes thousands of peptides. Many act as hormones and messengers: insulin regulates blood glucose, oxytocin is involved in childbirth and lactation, glucagon raises blood sugar, and gut peptides such as GLP-1 signal between the intestine and the brain. Others are neuropeptides (endorphins, substance P), antimicrobial peptides on skin and mucosal surfaces (defensins, cathelicidins), or fragments released when larger proteins are broken down.

Because peptides are built to fit particular receptors, they can carry very specific instructions — and because they are made of ordinary amino acids, the body can break them down again quickly. Both properties matter to researchers.

04

A short history

Peptide chemistry began in Germany at the start of the twentieth century. In 1901 Emil Fischer and Ernest Fourneau reported the first laboratory synthesis of a dipeptide, glycyl-glycine, and Fischer introduced the word "peptide" in 1902 [1]. Fischer received the 1902 Nobel Prize in Chemistry for his wider work on sugars and purines.

In 1921–22 Frederick Banting, Charles Best, James Collip and J. J. R. Macleod in Toronto isolated insulin — a peptide hormone — and used it to treat diabetes, the first medical use of a peptide [2]. Between 1951 and 1955 Frederick Sanger in Cambridge worked out insulin’s complete amino-acid sequence, proving for the first time that a protein has a defined sequence [3].

In 1953 Vincent du Vigneaud in the United States determined the structure of oxytocin and achieved its total synthesis — the first synthesis of a peptide hormone — for which he received the 1955 Nobel Prize in Chemistry [4]. In 1963 Bruce Merrifield published solid-phase peptide synthesis, building a chain step-by-step on an insoluble resin; this method, recognised with the 1984 Nobel Prize, is still the basis of how most research peptides are made today [5].

Since then, automated synthesisers, recombinant DNA production and high-resolution analytical techniques (HPLC, mass spectrometry) have made it routine to produce and characterise peptides of defined sequence and purity [6].

05

Natural, synthetic, approved and investigational

Naturally occurring peptides are those an organism makes itself. Synthetic peptides are made chemically; they may copy a natural sequence exactly or be deliberately modified — for example by swapping an amino acid or attaching a fatty-acid chain — to change stability or receptor binding.

Approved peptide medicines are synthetic or recombinant peptides that have passed through regulated clinical trials and been authorised by bodies such as the MHRA, EMA or FDA for a specific use. More than eighty peptide drugs have reached the market worldwide, including insulins, oxytocin, GLP-1 analogues and several hormone analogues [6].

Investigational compounds are peptides being studied in laboratories or clinical trials that have not been approved. Research materials — including those sold by Peptiva — are supplied for laboratory and in-vitro study only; they are not medicines, carry no approval and are not for human or animal use. The same chemical name can therefore describe an approved medicine in one context and an unapproved research material in another.

06

Why peptides are studied — and the limits of the research

Peptides interest scientists because they combine the specificity of large biological molecules with the chemical tractability of small ones. Modified peptides can be tuned for receptor selectivity and duration of action, and they are a major source of new medicines in metabolism, endocrinology and oncology [6].

The limits are just as important. Many widely discussed peptides have been studied only in cells or animals; results in a rat tendon or a mouse colon do not establish an effect in people. Published human data, where they exist, often come from small trials of a pharmaceutical formulation under medical supervision, and cannot be transferred to a research material. Claims of benefit, synergy between compounds or safety should be read against this background — and nothing on this website constitutes medical, dosing or administration advice.