How it is made
Where the word peptide stops meaning anything
A working definition, the boundary with proteins, and the two things in this catalog that are not peptides at all.
A peptide is a chain of amino acids joined by peptide bonds. Past roughly fifty residues the convention is to call it a protein instead, and the line is a convention rather than a chemical fact: nothing changes at residue fifty-one.
Why the length matters commercially
Short chains are made by solid-phase synthesis. Long ones increasingly are not, because yield falls with every cycle and past a certain length recombinant expression in cells becomes the cheaper route. That changes the impurity profile, the certificate and the price.
The things that are not peptides
Two items in this catalog are filed under research compounds rather than peptides, and it is not a technicality. NAD+ is a dinucleotide. 5-Amino-1MQ is a small-molecule methylquinolinium. Neither is a chain of amino acids and neither is made the way the rest of the shelf is made.
Most shelves in this market file both under peptides. It is a small thing that tells you whether the person writing the catalog knows what they are selling.
Blends are several peptides, not one
A blend vial holds two or more separate peptides co-lyophilized. It is one vial and one lot number, but the certificate should report each component separately, because a purity figure for a mixture is not a meaningful number.
For laboratory research use only. Not a drug, not a supplement, and nothing here is a claim about what any of this material does in a person or an animal.