BIOLOGIC PROPERTIES OF POLYNUCLEOTIDES. I. THE ANTI-COMPLEMENTARY ACTIVITY OF POLYNUCLEOTIDES*

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Abstract
Polyinosinic acid has been found to be a potent anticomplementary substance; 0.0073 [mu] mole P of this material will inhibit 1 50% hemolytic U of complement. A wide variety of mammalian and bacterial RNA, as well as calf thymus DNA, polyadenylic acid, polyuridylic acid, and polycytidylic acid, are devoid of anti-complementary activity. Mononucleotides also are devoid of anti-complementary activity. Polyinosinic acid does not interfere with the uptake of hemolysin by sheep red cells. The anticomplementary activity of polyinosinic acid can be abolished stoichiometrically by polyadenylic or polycytidylic acid in ratios consistent with the known structure of these hybrid helices (I + C, 21 + A). Mixed copolymers of inosinic and uridylic acids, or guanylic and uridylic acids having high guanylic or inosinic acid contents, possess anticomplementary activity that is not destroyed by pancreatic ribonuclease digestion. The anti-complementary properties of polynucleotides depend upon base composition and secondary structure.