Macroglobulins. 1. Studies on the isolation and physical properties of pathological macroglobulins

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Abstract
DEAE fractionation of the total serum globulins from a case of macroglobulinemia has been described. By the use of a gradient of increasing salt concentration and decreasing pH, a series of globulins, distinguishable but all sedimenting at about 7S, was first eluted; macroglobulins emerged much later as a complex of peaks. The different peaks of the complex did not differ in their sedimentation behavior. The macro-globulin fractions all contained three main stable sedimenting species (85% with S020 of 19.2S, 10% of 28.9S and 5% of 17.0S and traces of minor components, the sedimentation pattern being independent of total concentration, pH and temperature over considerable ranges. The differently sedimenting species were typical gamma-globulins electro-phoretically, with an isoelectric point at pH 5.9, and contained carbohydrate. Plots of corrected sedimentation coefficient (S020) against total initial protein concentration were linear and the extrapolated values at zero concentration differed from those reported for other macroglobulins. The different macroglobulin species were converted by 2-mercaptoethanol into a much slower and more homogeneously sedimenting material. On stabilization with iodoacetamide, the detailed sedimentation behavior was shown to be significantly different from that of the S7 globulins from the same serum. Reversal of the dissociation was slow and incomplete, slower-sedimenting species comparable with the originally occurring minor components now occurring more prominently. This evidence, and the electro-phoretic identity of the differently sedimenting macroglobulin species, suggest that the macroglobulins in this pathological case consist mainly of a number of different states of aggregation of the same monomeric unit. From sedimentation-velocity experiments on mixtures, it was found that the faster sedimenting components were retarded by slower material to the same extent as the slower retarded itself from its infinite dilution value. On the other hand, the observed retardation, of the faster components was greater than would be calculated from the increments in viscosity and density arising from the presence of the slower.