274 



R. A. Dilley, M. D. Henninger and F. L. Crane 



Separation and Identification of Quinones 



Thin- layer chromatography has been of tremendous value in the separa- 

 tion and identification of naturally occurring quinones. In addition to being 

 a rapid means of getting high resolution and handling relatively large quan- 

 tities of material, this method allows the simultaneous determination of the 

 oxidized and reduced forms of plastoquinones ^^' . Preparative strip chroma- 

 tography is easily accomplished using the thin-layer technique, thus allowing 

 isolation of measurable quantities of compounds which occur in very small 

 amounts. 



PHOTO- INDUCED CHANGES OF CHLOROPLAST QUINONES 



A study was conducted on the effect of light on the concentration of the 

 oxidized form of cx-TQ, PQ-(A-fB), and PQ-D in spinach chloroplasts. Thin- 

 layer chromatography was used to isolate the quinones from an acetone 

 extract of the chloroplasts ^^'. The conditions of the experiments are given 

 under Table II. Although the incident light intensity was 1600 foot candles, 

 the suspensions were so thick that the chloroplasts may be considered as 

 exposed to a lower light intensity. Table II shows the results of a repre- 

 sentative experiment. It is seen that low intensity white light results in an 

 increase in the concentration of oL-TQ and PQ-(A-fB). 



Table II 



Light and NADP- Induced Changes in Chloroplast Quinone Concentrations 



a-TQ PQ-D PQ-(A+B) 



umoles umoles umoles 



dark light dark light dark light 



1 0.55 1.1 1.3 1.3 6.4 8.1 



1 -I- NADP 0.60 1.6 1.3 2.5 7.4 5.6 



Fresh spinach chloroplasts (prep)ared according to Jagendorf and 

 Avron (5), chlorophyll assayed by method of Arnon (6) ) corres- 

 ponding to 50 mg chlorophyll, 0. 05 M tris pH 8. 0, 0. 01 M NaCl, 

 7. 5 umoles NADP, and distilled water to make final volume 200 

 ml. Light intensity 1600 foot candles. 



The presence of NADP in the reaction mixture resulted in a marked 

 increase in oc-TQ and PQ-D levels but a decrease in PQ-(A+B). Friend and 

 Redfearn have also shown a decrease in the concentration of oxidized PQ-A in 

 the presence of added NADP (^). Other experiments revealed that these light 

 and NADP- induced changes were inhibited by o-phenanthroline at 10" 4 M, 

 and that a dark incubation period following the light exposure resulted in 

 about the same quinone levels as in the dark control. Experiments are 

 presently underway to study the stoichiometry of the changes in OC-TQ, 



