512 



Leo P. Vernon, Waldo S. Zaugg and Elwood Shaw 



support an extensive photooxidation of PMSH2. Addition of Triton X-100 

 allows the photooxidation to proceed, while addition of deoxycholate causes a 

 photoreduction of PMS. The larger aliphatic side chain on UQ^ decreases the 

 solubility of this quinone in water. This may explain the inactivity of the UQ5 

 in the absence of detergent. 



TMQ, trimethylbenzoquinone, was also tested in photoreactions with PMS. 

 This quinone was added in the reduced form to PMS and sufficient time allowed 

 for the two compounds to react chemically. Subsequent illumination in the 

 presence of chloroplasts caused no appreciable reaction. The addition of 

 Triton X-100 resulted in a photoreduction of PMS, and a faster photoreduction 

 rate was obtained by the addition of deoxycholate. 



Although not examined in detail, other detergents were also tested as to 

 their effect on the PMS photoreactions. Sodium lauryl sulfate, an anionic 

 detergent, resembled deoxycholate in causing the chloroplasts to affect a 

 photoreduction of PMS, while digitonin had very little effect. A cationic de- 

 tergent ethylhexadecyldimethylammonium bromide also behaved like Triton, 

 resulting in a marked stimulation of the photooxidation rate for PMSH2. 



A number of people have reported on the effect detergents have on chloro- 

 plasts and chloroplast activity. Solubilization of chloroplasts was accom- 

 plished in 1941 by Smith, using digitonin, bile salts, sodium deoxycholate and 

 sodium dodecyl sulfate (17-19) ^^le first three detergents remove and 

 solubilize the chlorophyll while the latter splits the chloroplast into protein 

 units containing the pigment. Ke and Clendenning ^^^\ using such detergents 

 as sodium dodecyl sulfate, Zephiran chloride, Tween 20, Triton X-100, 

 digitonin, bile salts and saponin, studied the effect these detergents had upon 

 the Hill reaction and physical properties of the chloroplast. Eversole and 

 Wolken prepared a pigment -protein complex called chloroplastin by treating 

 chloroplasts with digitonin ^ ' and reported that it retained some of the 

 photochemical activities of the chloroplasts. Nieman and Vennesland ^^^' 

 reported that digitonin treated chloroplasts catalyze a photooxidation of 

 ferrocytochrome c. Hinkson and Vernon ' ' studied the effect of digitonin 

 upon ascorbate photooxidation in the presence of DPIP, di owing that digitonin 

 treated chloroplasts are more than six times as reactive. Chiba and 

 Okayama ' ' studied the effects of Dupanol C and span 80 upon the photo- 

 oxidations catalyzed by chloroplasts. These detergents solubilize the chloro- 

 plast and cause a marked increase in the photooxidation of ascorbate in the 

 presence of DPIP under aerobic conditions. Kondo et al. ^^^' have studied 

 the effect of surface active agents upon chloroplasts showing that cationic 

 and anionic detergents have the effect of either fluculating or lysing 

 (solubilizing) chloroplast preparations. They reported that nonionic deter- 

 gents had no effect. 



We have tested the effect of Triton X-100 concentration upon the chloro- 

 plast preparations used in our experiments. Table 1 shows that Triton X-100 

 is able to remove chlorophyll from the chloroplast with complete removal 

 being obtained at a concentration of 0. 02 per cent. Under these conditions 





