538 



Wilhelm Menke 



alike in the case of all plants examined so far (Fig. 2; ' . Terminal group 

 determinations showed that a considerable number of different polypeptide 



Fig. 2. The amino acid composition of the lamellar structural 

 proteins from thylakoids of different plants (left to right for each 

 amino acid) Oscillatoria chalybea, Chlorella pyrenoidosa, Allium 

 porrum, Spinacia oleracea, Antirrhinum majus 



chains is involved in the build-up to the lamellar structural proteiri^^. It has 

 so far been possible to dissolve the lamellar structural protein only in anhy- 

 drous formic acid. It is decomposed into subunits in this process, which 

 sediment fairly uniformly in the ultracentrifuge at 5. 9 S. The particle weight 

 is about 165, OftO.x Further decomposition takes place during oxidation with 

 performic acia . 



The composition of the lipid mixture is not so uniform in various plants, 

 although it also has common and characteristic features. I would draw atten- 

 tion here to the presence of galactolipids and the predominance of linolenic 

 acid among the fatty acidi^^' ^°' ^'^ • ^^' ^9, 20; -^he thylakoids contain 8-10% 

 chlorophyll. The quantitative chemical analysis of chloroplasts and their 

 lamellar system is but one of the ways to be adopted in elucidating the molec- 

 ular structure. 



It is known that chloroplasts are double refracting and dichroic. ^ The fluo- 

 rescence emitted by chloroplasts is in part linearly polarized ' ^^. The 

 analysis of optical anisotropy showed already quite some time ago that the 

 chloroplasts possess lamellar fine structure, and that the lamellar system 

 probably consists of protein and lipid layers which alternate with each other, 

 tha lipid molecules being oriented perpendicularly to the planes of the lamel- 

 lae^ '. The same result can be derived from volumetric studies (Fig. 3). If 



water 



Fig. 3. a- Changes in size and shape of chloroplasts of Plagiochilla 

 asplenioides due to loss of water and lipid extraction; b- The layer 

 model; c- The particle model 



chloroplasts, the water of which has been extracted by preservative drying, 

 are extracted with organic solvents, their diameter remains unchanged, while 

 their thickness is reduced to almost half. This must be the case if proteins 

 and lipids are present in separate layers. The diameter of mixed layers of 



