Relation between serum colloidal reactions, especially zinc turbidity test (ZnTT) and thymol turbidity test (TTT) and serum immunoglobulins was investigated.
Some of IgGs accelerated ZnTT and TTT, but IgA and IgD were not reactive with zinc nor thymol reagent. Some of IgGs had rather inhibitory effects on ZnTT and TTT. These inhibitory IgGs were electrophoretically faster and had higher carbohydrate and sialic acid contents than those of the IgGs which accelerated ZnTT and TTT.
From the results concerning inhibitory effect of amino acids on ZnTT, the most likely amino acid to bind zinc was histidine. In addition to histidine, threonine, serine, arginine, and tyrosine were also reactive with zinc reagent.
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