The short version
A peptide is a short chain of amino acids joined together by chemical links called peptide bonds. Amino acids are small molecules, and when a handful of them are linked in a specific order they form a peptide. Longer chains of the same building blocks are usually called proteins; the boundary between the two is a matter of length and convention rather than a hard rule.
In a laboratory-supply context, a peptide is simply a defined molecule with a known sequence of amino acids. That sequence is what gives each peptide its identity and its name.
Why the sequence matters
The order of amino acids in a peptide is called its sequence. Two peptides can be built from the same amino acids yet be completely different molecules if those amino acids are arranged in a different order. Because of this, the sequence is the single most important descriptor of a peptide, and it is what documentation such as a specification sheet or certificate of analysis refers back to.
How peptides are supplied for research
Research peptides are typically supplied as a lyophilised (freeze-dried) powder in a sealed vial, labelled with the peptide name, the quantity and a research-use-only statement. They are handled, stored and documented as laboratory materials. Evolution Biolabs supplies peptides strictly for laboratory research use only; nothing here is guidance for human or animal use.
Frequently asked questions
Is a peptide the same as a protein?
Not quite. They are made from the same building blocks — amino acids — but peptides are shorter chains and proteins are longer. The dividing line is conventional rather than exact.
What identifies one peptide from another?
Its amino acid sequence: the specific order of the building blocks. That sequence defines the molecule and is referenced by its documentation.