Peptides are one of the most studied classes of compounds in modern biochemistry. Yet the term is often misunderstood or conflated with other molecular categories. This guide provides a research-focused introduction to what peptides are, how they're classified, and why they're so widely used in laboratory science.
The Basic Definition
A peptide is a short chain of amino acids linked together by peptide bonds — the same chemical bonds that hold proteins together. The distinction between a peptide and a protein is primarily one of length:
- Peptides: typically 2–50 amino acids
- Polypeptides: 10–100 amino acids (loosely defined)
- Proteins: 50+ amino acids, often with complex folded structures
When two amino acids join via a peptide bond, the result is a dipeptide. Three amino acids form a tripeptide. Most research peptides fall in the range of 5–40 amino acids.
How Peptides Are Made
Peptides occur naturally throughout the body. For research purposes, they are typically synthesised using one of two methods:
Solid-Phase Peptide Synthesis (SPPS) — the most common method. Amino acids are added sequentially to a resin support, building the chain from C-terminus to N-terminus.
Recombinant DNA technology — used for longer, more complex peptides. A gene encoding the desired sequence is expressed in bacteria or yeast.
Research-grade peptides, like those stocked by Papa Peptides, are synthesised via SPPS and purified to ≥99% purity as verified by HPLC.
Why Purity Matters
When conducting experiments with peptides, compound purity directly affects result reliability. Impurities can introduce confounding variables in cell studies, affect solubility and reconstitution behaviour, and produce inconsistent results across experiments.
This is why every Papa Peptides product includes an independent Certificate of Analysis (COA) confirming purity per batch.
Classes of Research Peptides
| Class | Examples | Studied For |
|---|---|---|
| GLP-1 analogues | Semaglutide, Tirzepatide | Metabolic pathway research |
| Tissue-protective peptides | BPC-157, TB-500 | Cellular and tissue biology |
| Growth hormone peptides | Various GHRP analogues | GH secretion mechanisms |
| Melanocortin peptides | Various | Pigmentation, inflammation research |
Storage and Handling Fundamentals
Research peptides are fragile compounds. Proper storage is essential:
- Lyophilised form: most stable. Store at -20°C in a dry, dark environment.
- Reconstituted solution: store at 4°C. Use within 2–6 weeks.
- Avoid freeze-thaw cycles: these break peptide bonds and reduce purity.
- Reconstitution: use bacteriostatic water or sterile saline.
Browse our range of research-grade peptides: papapeptides.my/shop