Category: Compound Identity

hCG is a two-chain glycoprotein with no single mass, so vials carry WHO-referenced International Units. What 5,000 IU does and does not tell you.

Oxytocin (CYIQNCPLG-NH2) is a nonapeptide with a Cys1-Cys6 disulfide ring. Sequence, 1007.2 mass, vasopressin comparison, HPLC and impurity checks.

NAD+ identity reference: dinucleotide structure, C21H27N7O14P2 at 663.4 g/mol, the 340 nm test for NADH, HILIC and ion-pair HPLC, degradants and MS ions.

Semax sequence explained: how it differs from ACTH(4-10), why methionine oxidation gives a +16 Da peak, and how to read its HPLC and mass data.

Selank explained structurally: the tuftsin core, why a Pro-Gly-Pro tail resists exopeptidases, and why 280 nm purity figures mislead for this peptide.

Melanotan-I, Melanotan-II and PT-141 compared by sequence, ring structure, C-terminus, formula and mass, and what that means for identity data.

Why Long R3 IGF-1 is quoted at 9111.5, 9117.6 or 7649 Da, what intact mass misses about disulfide pairing, and which methods reveal folding.

How N-terminal acetylation and C-terminal amidation change peptide mass, charge and identity, and how to spot the difference in sequence notation.

A practical key to research peptide names: sequence direction, fragment ranges, bracketed substitutions, terminal groups, DAC and salt forms.

GHK and GHK-Cu compared: CAS numbers, formulas, molecular weights, how copper binds, and why the label weight convention changes price comparisons.