86 



UNITY AND DIVERSITY IN BIOCHEMISTRY 



^ ,-^'8,35 



Fig. 1 (Meyer and Mark) — The dimensions are shown in Angstrom units. The black 

 dots represent the oxygen atoms of the pyranose rings. 



seems clear that cellulose contains only l:4-jS-linkages. Hydrolysis of 

 methylated cellulose yields 2:3:4:6-tetramethyl-glucopyranose and 2:3:6- 

 trimethylglucopyranose. Methylation followed by hydrolysis never gives 

 any dimethylglucose, so the chain must be a straight one. The chain 

 differs in length according to the source of the cellulose, and the values 

 obtained range between 1400 and 10,000 glucose units. The lay-out of 

 atoms is such that each cellobiose residue has the dimensions shown 

 in Fig. 5. 



The cellobiose chains, arranged in the network illustrated by Fig. 1, are 

 grouped in bundles, the cellulose micelles, which are about 50A thick and 

 at least 500A long. The grouping of these micelles as they exist in structures 

 where the crystallites are parallel is shown in Fig. 2. 



Fig. 2 (Seifriz) — Orientation of the micelles in a block of cellulose 



