Photochemical Activities of Spinach Chloroplasts Following Treatment with the Detergent Triton X-100.

A nuinber of detergenits have beeni used to convert chloroplasts inlto smaller complexes for miiore intensive study of the properties of the photosynithetic apparatus (16). In all early series of experiments, Smiiith treated chloroplasts with digitonin, bile salts, sodium deoxycholate and sodium dodecyl sulfate (2325). The first 3 detergents removed and solubilized the chlorophyll wlhile the latter split the chloroplasts inlto protein units containing the pigment. Other investigators have employed Zephiran chloride, Tween 20 aind saponin (10), Duponol C and span 80 (4). anid several anionic and cationic detergents (15). Digitolnin treatment of chloroplasts has been uised to release a photooxidative activity (5, 9, 13, 20) aniid to l)rodlice sel)arable chloroplast fractionls whiclh conltaini altered chlorophyll ratios anid appear to represenit a separationi of pigment systemii I (1, 3. 31). Tritoln X-100 effectively ruptures initact chloroplasts, and at low conicenttrationis dlisrul)ts the se(luetitial electroni flow required for the Hill reaction (6, 10, 22). Satier anid Park reported that in coiitrast to other dletergenits tested. Tritoni X-100 causes a change in the fluiorescenice l)rol)erties of the chloro)last at concentrations below those required to inhibit the Hill reaction (22). indicatillg a facile interaction of this detergent wvith the chlorophyll of the chloroplast. The experiments of Vernon et al. showed that chloroplasts solubilized by Tritoni X-100 catalyze photochemical redox reactions similar to those catalyzed by purified chlorophyll a solubilized by the same detergent (28, 30). Furthermore, Kahn isolated a chlorophyll-protein complex from chloroplasts by treatments with Triton X-100 (7). In contrast to the solubilizinig effect of Triton X100 at high concentrations, lower amounts produce rather specific effects uponl the inltermiiediate electroni transport complex of chloroplasts, inhibiting photophosphorylation and the related pH shift while stimulating electron flow (6. 18. 19). Because of its maniy effects upon the photosynthetic apparatus, an investigation into the actioni of this detergent upon a variety of photochemical reactions of spinach chloroplasts has been coniducted and serves as the basis for this paper.