Estimation of Molecular Size of Complement Components by Sephadex Chromatography

The molecular weights of C′1, C′2 and C′4 (the first, second and fourth components of complement) in a number of species were estimated by studying their behavior in gel filtration. The molecular weight found for C′4 was about 180,000 and for C′2 about 150,000. C′1 is a considerably larger molecule than C′4 or C′2, for it coincided with the high molecular weight fraction obtained from serum by gel filtration. Using intermediate products and purified components of guinea pig C′, we have demonstrated the presence of C′1, C′2 and C′4 in the sera of a wide variety of mammals.