Molecular weight and some chemical properties of the granulocytic chalone

Granulocytic Chalone (GCh) has been highly purified from culture medium conditioned by human peripheral leukocytes. Purification was performed by column chromatography on Sephadex G-25 and G-10, rechromatography on G-10, preparative paper chromatography and thin-layer-chromatography. The inhibitory activity and specificity of GCh was monitored by agar colony formation and 3H-thymidine incorporation into bone marrow and thymic cells. The gelchromatographic behavior of GCh is discussed in detail with regard to its molecular weight. The results obtained indicate that GCh may be a small (MW 500--600), acidic and highly polar peptide containing aspartic and glutamic acid among others. The N-terminal aminogroup seems to be blocked.