206 MACROMOLECULAR COMPLEXES 



Extraction of Wall Components from Intact Cells 



In view of the substantial body of information developed up to 

 about 1950 on the polysaccharides obtained by extraction of intact 

 yeast cells with hot water, hot alkali, or cold concentrated acid, it 

 seems advisable to present a short survey of information available 

 prior to the present era of studies on the composition of clean cell 

 walls isolated from mechanically disrupted yeasts. A comparison 

 of results obtained by application of the several methods of extrac- 

 tion enumerated above has been presented by Garzuly-Janke 

 (1940), who concluded that hot alkaline extraction procedures lead 

 to more or less profound modifications of the alkali-soluble poly- 

 saccharide component. Certainly the application of more or less 

 drastic extraction procedures designed to remove a polysaccharide 

 material from a cell as a protein-free, nucleic acid-free moiety has 

 led us to some insight into the nature of the polysaccharide in ques- 

 tion, but it has also given rise to considerable controversy about the 

 natural structure of the polysaccharide. Furthermore, efforts di- 

 rected at "throwing away the protein" have not led to an apprecia- 

 tion of the importance of protein -polysaccharide complexes as the 

 macromolecular fibers of the cell-wall fabric. 



Yeast Glucan. The water-insoluble polysaccharide fraction of 

 yeast that resists boiling in dilute alkali was studied by Salkowski 

 (1894b) and designated yeast "achroocellulose." This fraction was 

 subsequently studied by Zechmeister and Toth (1934), who found 

 that, like cellulose, the resistant polysaccharide could be hydrolyzed 

 in 40 per cent HCl, although it did not exhibit many of the other 

 characteristics of cellulose (yeast glucan is insoluble in Schweizer's 

 reagent, does not produce a color with zinc-chlor-iodide, and does 

 not yield cellobiose on acetolysis). An uncommon 1,3-glucosidic 

 linkage was indicated for yeast glucan from methylation studies: 

 2,4,6-trimethylglucose was the sole product isolated. Further work 

 by Hassid et al. (1941) on the glucan fraction confirmed 2,4,6-tri- 

 methylglucose as the sole methylation product, and supplied evi- 

 dence of the /^-configuration for the anhvdroglucose units in the 

 polymer (i.e., low specific rotations of the alkylated derivatives and 

 upward mutarotation during their hydrolysis). From viscosity de- 

 terminations a molecular weight of 6500 was suggested, and the 



