Effect of Petroleum Ether Extraction and Readdition of Various Compounds on the Photochemical Activity of Isolated Chloroplasts.

The discovery in this laboratory by Lynch and French (1) that A3-carotene partially restores the photochemical activity lost by petroleum ether extraction of chloroplasts suggests that this pigment is ain active component of the photosynthetic mechanism. This observation prompted the present inquiry to determine whether ,8-carotene is specific for such reactivation or whether other fat soluble components in the petroleum ether extract may replace or complement the,-carotene effect. In the course of these studies certain refinements in techniques for isolation of chloroplasts and for measuring photochemical activity were introduced. Lynch and French (1) found that the extracted material usually retained a substantial fraction of its original activity, and that readdition of the petroleum ether extract restored its photochemical activity to a larger extent than did the addition of pure ,8-carotene. In the present work, we found it possible to reduce the activity by petroleum ether extraction nearly to zero by changing the method of isolating the chloroplast material. The reactivating effect of a number of substances other than /8-carotene was tested. None of these equalled the reactivation effect of adding back the intact petroleum ether extract.