POLYSACCHARIDE-PROTEIN COMPLEXES 219 



thinner cell wall." Photographs of Northcote and Home (1952) 

 clearly show two layers in wall material that had been extracted 

 only with lipid solvents, but their photographs reveal only one laver 

 in wall material that had been treated with 3 per cent aqueous 

 NaOH to remove mannan and protein. 



Fig. 10. Electron micrograph of isolated cell wall of bakers' yeast. Bud 

 scar, as seen from outside of cell, has central mark that appears as a depres- 

 sion. 



The initial ultracentrifugal studies on the glucomannan-protein 

 complex in the primaiy alkaline extract of isolated walls had shown 

 (Fig. 3) the presence of a major component that sedimented as a 

 single peak, but the height of the boundary to the left of the peak 

 indicated the presence of material of low molecular weight. On 

 subsequent fractionation of the primary extract with ammonium 

 sulfate, the components GMP-I and GMP-II were obtained. Ultra- 

 centrifugal studies on these components (Figs. 11, 12) show GMP-I 

 to be a slowly sedimenting substance of low molecular weight, 



