Physikalische, chemische und biologische Charakterisierung von menschlichem Choriongonadotropin

Purification of commercially available HCG preparations with DEAE Sephadex A 50 and Sephadex G 100 column chromatography gave homogeneous fractions having specific biological activities four fold those of the starting materials. The purified HCG has ICSH characteristics and, in high doses, a definite FSH effect is present.Chemical analysis of HCG showed it to contain 29% carbohydrates and 69% peptides. The C-terminal amino acid of the peptide chain was found to be serine, but the N-terminal amino acid could not be determined with normal methods. A molecular weight of 22000 — 27000 daltons was obtained by quantitative end group analysis. Ultracentrifugation experiments in 4 m guanidine hydrochloride gave a molecular weight of 27200 daltons, but in neutral saline solutions at HCG concentrations above 2 mg/ml the apparent molecular weight was higher and indicated dimer formation. A dissociation constant of 10-5 mol/l was estimated for the monomer-dimer equilibrium. Since biological activity is found with 0.1 to 0.5 µg, it was concluded that the HCG monomer is the active entity.The purified HCG is stable from pH 4.5 to pH 10 for 6 hours at 37 °C. At pH 2.5 only 5 to 10% of the original activity is retained. HCG is rapidly inactivated at 100 °C, but a residual activity of 6 — 10% remained after 30 minutes at 80 °C. No activity was lost after 30 minutes incubation at 60 °C.