Abstract
C2n was isolated and purified from nurse shark serum by initial cold low ionic strength precipitation, followed by ion exchange chromatography on DE-52 cellulose, adsorbtion/desorbtion on hydroxylapatite and filtration on Bio-Gel A-0.5. The final purification step used was polyacrylamide disc gel electrophoresis. The molecular weight of C2n was determined by gel filtration on Bio-Gel A-0.5 and Sephacryl S-200, and polyacrylamide disc gel electrophoresis: values obtained were 1.7 x 10('5) daltons, 1.6 x 10('5) daltons and 1.8 x 10('5) daltons respectively. C2n is heat stable, retaining 100% activity after heating for 2 hours at 56(DEGREES)C. The component is not compatible with guinea pig C2 and interfers with the lysis of EAnC1n by guinea pig C4 in the presence of C4-deficient serum. No appreciable decay of EAnC1nC2n was noted in 1 hour at 30(DEGREES)C. Comparative studies suggest C2n to be analogous to its mammalian counterpart, C4.