Application of Equilibrium Density Gradient Sedimentation to the Separation and Purification of Proteinpolysaccharides

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Abstract
Mixtures of proteinpolysaccharides can be effectively separated by equilibrium sedimentation of solutions containing high concentrations of salts such as cesium chloride. The method is most effective when the buoyant densities of the constituent molecules differ widely. Degradation of the proteinpolysaccharide macromoleculcs is minimized because degradative enzymes readily sediment away from the denser carbohydrate-containing substances. The macromolccules are subjected to conditions no more severe than exposure to high salt concentrations. The recovery of material is always quantitative and all components are subjected to identical treatments. By sedimenting dilute solutions of proteinpolysaccharides to equilibrium in cesium salt density gradients, separation and concentration can often be effected in a single step. The method is less suitable when the constituent proteinpolysaccharides are polydisperse or of small molecular weight. In the case of very complex mixtures of proteinpolysaccharides, i.e., extracts from arterial tissue, the method may be useful for preliminary separations only. The method is time-consuming and can be expensive with regard to materials and equipment. However, as most laboratories possess high-speed preparative centrifuges and cesium salts can be recovered after use, these problems are not insurmountable.