Glutathione is a small tripeptide — three building blocks — supplied in its reduced form, known as GSH. It is among the most common and recognizable reference molecules in the laboratory, and it comes as a crystalline solid.
It ships as one laboratory batch, characterized for third-party verification and retrievable by lot number.
The detail that makes it unusual is its very first bond. The first two building blocks are joined through a side branch rather than the normal end-to-end link that peptides usually use. Because of that quirk, the simplest letter shorthand would misdescribe it — implying an ordinary bond that isn't there — so only the fuller annotated form is recorded. It dissolves readily in water.
For laboratory research use only. Not for human or veterinary use.