Two Methods of Fractionating Potato Tuber Proteins and some Preliminary Results with Dormant and Active Tubers.

Two methods of fractionating the protoplasmic proteins of potato tubers are described, the first based primarily on filtration, the second primarily on highspeed centrifugation. By the first method it was shown that proteins increase about 20 per cent when tuber-halves are transferred from +3 to +26°C for 10 days during late fall and decrease about 10 per cent during a similar transfer in summer. Tubers kept constantly at +26°C showed a steady drop in protein content, which became more rapid as soon as sprouting was initiated. A similar initial drop occurred during three successive years on transfer to +3° C, but after a few weeks either the original protein content was largely regained or at least the drop was markedly slowed up as compared with tubers at +26° C. Differences between fractions associated with sprouting are indicated. By the second method it was shown that conversion of tubers from the dormant to the active state by transfer from +3° to +26° C for 10 days resulted in a large decrease in mitochondria, microsomes and acid-insoluble proteins, whereas the globulins and acid-soluble albumins remained unchanged. The changes in the first three fractions decreased as the tubers came out of their rest period. These changes associated with sprouting are essentially in agreement with the changes found by the first method. A comparison of the two methods indicates that method 2 yields a more nearly complete extraction and a better separation of the fractions. [ABSTRACT FROM AUTHOR]