3 CHLOROPLASTS 247 



16% of raw wax and 2-7% of phosphatides (Menke and Jacob, 

 T942). Other authors find similar values as shown in Table XXIV 

 (Frey-Wyssling, 1949b). 



There is no intrinsic chemical difference between the chloroplastic 

 protein and cytoplasmic protein of spinach (Noack and Timm, 1942; 

 TiMM, 1942) ; the former contains a little more histidine and somewhat 

 less lysine and glutamic acid. According to Noack (1930), the cata- 

 lytically active iron (Noack and Liebich, 1941; Liebich, 1941) is 

 bound by adsorption in the stroma. Mommaerts was inclined to view 

 the grana as the containers of the iron, but the grana he used for his 

 Avork were not perfectly pure. 



Microchemically, the lipid content of the stroma has been definitely 

 proved both by the myelin forms produced by Weber (1933) and 

 Menke (1934a) from chloroplasts, and by the vital staining of the 

 grana by the lipid dye rhodamine B introduced by Strugger (1936/37). 



The formation of myelin depends upon the following two con- 

 ditions: firstly the lipid molecules must be liberated from any loose 

 linkage to the protein frame so that they can "coalesce"; secondly, 

 they must possess not only lipophiHc, but also hydrophiHc end groups 

 which, as seen on p. 5 6, cause an infiltration of water. The presence 

 ■of water alone does not initiate the emigration of the plastid myelin, 

 from which fact one may infer that the lipids in the chloroplasts have 

 no free hydrophilic groups, but that these are screened ofT, for instance, 

 by the formation of a hpoprotein complex. If, however, they are 

 liberated by saponification in a shghtly alkahne medium (NH4OH), 

 myelin is formed at once. 



We have fewer exact data on the chemical constitution of the 

 grana. If they do not serve merely as energy traps, but are at the same 

 time the loci of COo assimilation, they must contain proteins in 

 addition to pigments. Euler, Bergman and Hellstrom are of 

 opinion that this system is ten to twenty times the size of a chlorophyll 

 molecule. Mestre (1930) calls the compound between chlorophyll, 

 lipid and protein the "phyllochlorine complex". Stole, borrowing 

 Willstatter's nomenclature (Willstatter and Rohdewald, 1934), 

 called the hypothetic compound "chloroplastin simplex". (It should 

 be noted that in this term the word "plastin" does not cover the sense 

 in which the older authors employed it; they used it to denote the 

 stroma protein, whereas it is here applied to the grana protein.) Stole 



