STATIC LIGHT-SCATTERING TECHNIQUE APPLIED TO PECTIN IN DILUTE-SOLUTION .3. THE TENDENCY FOR ASSOCIATION

The tendency for association was studied by light scattering applied to a series of a high-methoxyl citrus pectin solution in phosphate buffer. To prevent artefacts, the clarified stock solution and buffer were mixed within the measuring cell. The measured data are presented as Zimm and master plots. A reversible increase of the apparent molecular weight with rising polymer concentration and slightly negative second virial coefficients were found in the case of the uncentrifuged, but filtered, solutions, indicating a slight tendency for association. The associates formed remain relatively small. This is independent of the pore size of the filters used for clarification. Prepurification by ultracentrifugation gave solutions which showed two-component behaviour and gave no hint of association.