Active-material utilization volume changes

Russet Burbank potatoes were quartered and placed in a water bath at 80 C for 10 min. The tubers were rinsed with cold water and blended to a paste. Absolute ethanol was blended in slowly with the paste until it was 80% ethanol by volume. The mixture was filtered through Whatman No. 1 filter paper with the aid of a vacuum. The ethanol in the filtrate was removed by vacuum evaporation and the resulting solution was dialyzed in a 2,000 MW cut off dialysis bag against several changes of distilled water. The remaining extract in the dialysis bag was lyophilized. The dry material contained one major polypeptide, CPI, and some minor components. On a protein basis the material was over 95% CPI. Purity of this crude CPI fraction was also demonstrated by electrophoresis by the method of Panyim and Chalkley (8). No Inhibitor I nor Inhibitor II could be detected by immunological techniques, however a small quantity of trypsin inhibitor activity (less than 0.5%) was present, presumably from contamination by the polypeptide trypsin inhibitor that is present in potato tubers (4). This CPI preparation was utilized for the chick feeding experiments. 

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