What Are Peptides? – A Scientific Research Guide

Published by Scandinavian Pen Peptide

Everyone knows about proteins. Amino acids too—at least by name. But peptides? They rarely come up in everyday conversation, even though biochemically they are among the most important molecules in the human body.

This is not because they are unimportant. It’s because they often work in the background—as signals, regulators, messengers. Without peptides, insulin wouldn’t work. Without peptides, nerve cells wouldn’t communicate properly. Without peptides, much of the body’s hormonal regulation would simply collapse.

This article explains what peptides are, how they are structured, what role they play in biology, and why they have been one of the most active areas of biomedical research for years. Browse our full range of research peptides or explore our research guides.

What Is a Peptide?

Peptides are short chains of amino acids linked by peptide bonds. The peptide bond itself forms through a condensation reaction between the amino group of one amino acid and the carboxyl group of another—with the release of a water molecule.

Depending on the length of the chain, we distinguish between: dipeptides (2 amino acids), tripeptides (3), oligopeptides (4 to 20), and polypeptides (longer chains). The boundary between peptide and protein is not sharp—from about 50 amino acids onwards, it is generally referred to as a protein, but this is a convention, not a biological law.

The Difference from Proteins

Insulin has 51 amino acids and is a peptide. Hemoglobin has over 570 and is a protein. Proteins often perform structural functions—collagen maintains connective tissue, actin and myosin enable muscle contraction. Peptides, on the other hand, are most often functional signals: they transmit information between cells, activate receptors, and trigger biochemical cascades.

How Peptides Act Biologically

Peptides communicate with cells via receptors. A peptide binds to a specific receptor on the cell surface, which triggers an intracellular signaling cascade, and the cell changes its behavior.

• GLP-1 binds to GLP-1 receptors in the pancreas and stimulates insulin secretion.
• GHRH binds to receptors in the anterior pituitary and stimulates the release of growth hormone.
• Endorphins bind to opioid receptors and reduce pain perception.

Naturally Occurring Peptides in the Body

Insulin regulates glucose metabolism. It is the best-known example of a peptide playing a vital hormonal role.

GLP-1 is secreted in the gut after meals, signals satiety to the brain, and stimulates insulin production. This is the starting point for Semaglutide, Tirzepatide, and Retatrutide.

GHRH is the endogenous signal that prompts the pituitary to secrete growth hormone. CJC-1295 is a synthetic analogue that mimics this signaling pathway.

BPC-157 is derived from a protein found in human gastric juice. Preclinical studies have observed effects on tissue repair and angiogenesis.

MOTS-c is encoded in mitochondrial DNA. It is secreted during physical exertion and activates AMPK, a central regulator of energy metabolism.

How Research Peptides Are Made

Most research peptides are synthetically produced by solid-phase peptide synthesis (SPPS). Amino acids are linked step-by-step to a solid support, the completed chain is cleaved from the resin, and purified by HPLC. Purity is checked by mass spectrometry. Purity levels above 98% are considered the standard in the scientific community. For the underlying methodology, see SPPS literature on PubMed.

Current Research Areas

Metabolism and Obesity. Retatrutide, a triple GLP-1/GIP/glucagon agonist, showed average weight reductions of over 17% after 24 weeks in phase 2 data. Phase 3 studies are underway. See Retatrutide phase 2 data on PubMed.

Tissue Repair. BPC-157 and TB-500 are being studied in preclinical models for their effects on muscles, tendons, cartilage, and wound healing.

Growth Hormone Axes. Ipamorelin and CJC-1295 are frequently combined in studies on the GH axis. Ipamorelin is considered a selective GHRP that stimulates GH secretion without significantly affecting ACTH or cortisol.

Cellular Aging. Epitalon, Thymalin, and MOTS-c are among the compounds being investigated in longevity research. See longevity peptide research on PubMed.

Skin and Collagen. GHK-Cu is one of the most well-characterized peptides in dermatological research. See GHK-Cu studies on PubMed.

Quality and Storage

For serious research, three elements are essential: purity, proof of identity, and correct storage. A Certificate of Analysis (COA) documents the purity level, molecular weight, and lot number. Without a COA, the quality of a substance cannot be independently verified.

Lyophilized peptides are generally stable at −20°C for several months. In solution, most compounds degrade much faster. Avoid repeated freeze-thaw cycles—aliquoting before storage is the practical solution.

Legal Situation in France

Research peptides are legal in France when acquired exclusively for scientific purposes and not intended for human use. Compounds classified as medicines are subject to the Public Health Code and require marketing authorization. The intended use is the determining factor. For further questions, visit our FAQ.

FAQ

What is a peptide?
A short chain of amino acids linked by peptide bonds. Peptides occur naturally in the body and act as hormones, neurotransmitters, and signaling molecules.

What is the difference between peptides and proteins?
The boundary is blurry. Roughly: peptides are shorter and often signaling molecules, proteins are longer and often structural molecules.

How are research peptides made?
By solid-phase peptide synthesis (SPPS). Amino acids are linked sequentially to a support resin, the completed chain is cleaved and purified by HPLC. Purity levels above 98% are the norm.

Are research peptides legal in France?
Yes, for scientific purposes. The intended use is decisive—not the chemical structure of the molecule.

What is a COA?
A Certificate of Analysis that documents the purity, molecular weight, and lot number of a compound. Without a COA, quality cannot be independently verified.

How should peptides be stored correctly?
Lyophilized at −20°C. In solution, stability is shorter. Avoid repeated freeze-thaw cycles. Aliquoting before storage is the practical solution.

⚠️ Research use only. All products from Scandinavian Pen Peptide are exclusively intended for laboratory research purposes. They are not medicines and are not intended for the diagnosis, treatment, or prevention of diseases. Contact us or visit our distributor page for more information.