Preparative isolation of polyphosphoinositide fractions from ox brain

A simple preparative method for chromatographic isolation of pure fractions of di- and triphosphoinositides (1-phosphatidylinositol 4-phosphate and 1-phosphatidylinositol 4,5-bisphosphate) from ox brain is described. Polyphosphoinositide fractions have been obtained by ion-exchange chromatography of the lipid extract using gradient elution with 0-0.6 M ammonium acetate in chloroform/methanol/water (20:9:1) from a DEAE-cellulose column. Before chromatography, divalent metal ions were removed from the lipid extract by passing through a Dowex-50 (H+) column and lipids were converted to the sodium salt by neutralisation with sodium hydroxide in methanol solution. After chromatography, fractions of di- and triphosphoinositides were precipitated in methanol/water mixture (1:1) by evaporation in a vacuum to a final concentration of about 4 M ammonium acetate. Necessary salts of di- and triphosphoinositides were obtained by passing the ammonium salts of the lipids through Dowex-50 (H+) and neutralising with corresponding base in methanol solution. About 0.35 mmol of diphosphoinositide and 0.63 mmol of triphosphoinositide were obtained from 1 kg of wet ox brain tissue.