Research Overview
Why glycosylation defines this molecule
Among protein hormones, hCG is one of the most instructive examples of carbohydrate as a functional determinant rather than decoration. Its N-linked glycans support correct folding and heterodimer assembly, while the O-linked sugars on the beta subunit's C-terminal extension slow renal and hepatic clearance dramatically. Deglycosylated hCG still binds LHCGR but signals poorly, a finding that helped establish that receptor binding and receptor activation are separable events.
Shared subunit architecture
hCG, LH, FSH and TSH all share an identical alpha subunit and differ only in beta. This makes the family a natural system for studying how specificity is encoded in protein–protein interfaces. Because hCG-beta and LH-beta are highly homologous over their first hundred-odd residues, the two hormones act on the same receptor, and hCG is routinely used as the long-acting stand-in for LH in experimental systems where LH's short half-life is inconvenient.
- LHCGR binding, activation and cAMP signalling kinetics
- Structure–function work separating binding determinants from activation determinants
- Gonadal steroidogenesis models in cell culture and animal systems
- Assay and standard-reference applications, since hCG underpins pregnancy immunoassays
Potency, not mass
Unlike synthetic peptides, hCG is quantified by biological activity in international units rather than by weight, because glycoform heterogeneity means preparations of equal mass need not have equal activity. Highly purified material runs in the region of ten thousand international units per milligram, but the assayed value on the certificate of analysis is the figure to work from, not a mass conversion.
Stability considerations
As a non-covalent heterodimer, hCG can dissociate into its free subunits — which are individually inactive at LHCGR — under heat, extreme pH or vigorous agitation. It is therefore markedly more fragile in solution than the small peptides in this catalogue. Gentle reconstitution, cold storage, minimal agitation and short in-use periods are the standard precautions.
