Size exclusion chromatography of proteoglycans from the supernatant (A) and cell extract (B) of the immature erythroid progenitor cell line HEL. Proteoglycans isolated by anion exchange chromatography were submitted to size exclusion chromatography on a TSK 4000 column. Elution profiles for the proteoglycans from the supernatant (A) and cell extract (B) are shown for the native (——) and HNO₂-treated (- - -) samples. Elution profiles were monitored by liquid scintillation counting.