312 FINE-STRUCTURE OF PROTOPLASMIC DERIVATIVES III 



TABLE XXIX 

 AMYLOSE CONTENT OF STARCH 

 (from bates, FRENCH AND RUNDLE, 1 943) 



Starch 



% Amylose 



Ketan {Ory^a sativa f. glutimsa) . 

 Waxy Corn {Zea mays f. saccharatd) 

 Tapioca {Manihot utilissimd) . . 



Rice {Oryxa sativa) 



Banana {Musa sap/enfum) . . . . 



Corn (Zea mays) 



Potato {Solanum tuberosum) . . . 

 Wheat {JTriticum aestivum) . . . 

 Sago {Mefroxylon spec.) .... 

 Lily bulb {JLilium spec.) .... 



o 

 o 



17 

 17 

 20.5 



21 

 22 



24 

 27 

 34 



Freudenberg, Schaaf, Dumpert and Ploetz (1939) as also 

 RuNDLE and Edwards (1943) argue that the chains of dissolved and 

 precipitated amylose molecules are spirals, with six successive glucose 

 rings to one revolution. Just as there are H-bonds between the neigh- 

 bouring chain molecules of cellulose, so might there also be H-bonds 

 between neighbouring turns of the same chain in the spiral model of 

 the starch molecule. The six glucose rings per revolution can be 

 compared with Schardinger's dextrins^, the molecules of which 

 contain six to seven glucose residues (Hanes, 1957). Then, the inside 

 of the hollow cylinders formed by the spiral chain provides the 

 necessary space for the infiltration of iodine causing the blue starch 



reaction. 



Dextrins obtained as de- 

 gradation products in starch 

 hydrolysis give no iodine 

 colour reaction when they 

 contain only six or fewer 

 glucose units. Dextrins con- 

 taining eight to twelve glu- 

 cose units produce red ra- 

 ther than blue complexes. Only the longer amylose chains give the 

 typical blue iodine colour. It is believed that the \ molecules are 

 arranged along the centre of the amylose helix (Fig. 153). 

 ^ Kratky and Schneidmesser (1938). 



Fig. 153. Model of iodine-filled amylose helix, 

 (from RuNDLE, Foster and Baldwin, 1944). 



