Reading a Peptide's Technical Data Sheet: CAS Number, Mass, Sequence and Formula
CAS number, molecular formula, molar mass, one- and three-letter sequence codes, salt, purity, storage: what each line of a data sheet is for.
Contents
A peptide data sheet lists a series of coded information: CAS number, formula, mass, sequence… Each has a precise use in the lab. Here is how to read them.
The CAS number
The CAS number (*Chemical Abstracts Service*) is a unique identifier assigned to a chemical substance, in the form *XXXXXX-XX-X*. It lets you find a molecule unambiguously in databases and the literature, whatever trade name is used. Careful: a salt form or a variant of the same peptide can have a different number.
The molecular formula
The molecular formula (for example C₁₄H₂₄N₆O₄ for GHK) gives the number of atoms of each element. It serves as a consistency check against the molar mass and the sequence.
The molar mass
Expressed in g/mol (or daltons, Da), the molar mass is the figure found on a certificate of analysis: mass spectrometry checks that the measured mass matches the theoretical mass, which confirms the compound's identity (see how to read a certificate of analysis).
The sequence
The sequence describes the order of the amino acids, from the amine end (N-terminal) to the acid end (C-terminal). Two notations coexist:
- the three-letter code: Gly-His-Lys;
- the one-letter code: GHK.
Notes sometimes complete the sequence: -NH₂ (amidated end), Ac- (acetylation), D-form amino acids, or a cyclization (a disulfide bridge between two cysteines, for example). These modifications change the molecule's stability and behaviour (see the example of NA Selank Amidate).
The counter-ion
Many peptides are supplied as a salt: acetate, trifluoroacetate (TFA), hydrochloride. The counter-ion is part of the weighed mass: the amount of peptide actually present can therefore be slightly lower than the total powder mass. The certificate of analysis often states the measured quantity, which clears up any doubt.
Purity, appearance, solubility, storage
- Purity: percentage determined by HPLC (for example ≥ 99%).
- Appearance: usually a white lyophilized powder (GHK-Cu is blue: see why).
- Solubility: the recommended solvent, useful for choosing between sterile and bacteriostatic water.
- Storage: recommended temperature for the powder and for the solution.
The cross-checks to make
Before any experiment, three simple checks: the vial's name and lot match the certificate; the measured mass matches the data sheet's theoretical mass; the stated purity is met.
To learn more
Research Use Only (RUO). This content explains the technical documentation of laboratory reagents. It constitutes neither a recommendation for use in humans or animals nor a therapeutic claim.
