OPTICAL ROTATORY DISPERSION OF AMYLOSE FILMS

There is a direct correlation between the structure of amylose in the solid state, as determined by X-ray diffraction, and the conformation of amylose in solution. The specific rotations of amylose films showing a methyl sulfoxide complex (VMe2SO), amorphous, or alkali-amylose structure are the same as those of amylose in corresponding solutions of methyl sulfoxide, 0.5m potassium chloride, or 0.1-0.5m potassium hydroxide. The rotation of amylose films that give a B-type of X-ray pattern is higher than that of either amylose V or amorphous films; this higher rotation is attributed to the presence of intermolecular hydrogen-bonds between adjacent amylose chains in the B structure. It is also shown that rotatory dispersion data, alone, cannot be used to establish the conformation of amylose in solution, since the parameter λc in the Drude equation is insensitive to changes in structure; that is, amylose VMe2SO, V, and water-soaked B films all have a λc of 150 nm. Consideration of X-ray, optical rotation, and published viscosity data leads to the conclusion that there is a continuous transition from a stiff, tightly coiled helix in methyl sulfoxide to a flexible coil in neutral, aqueous solution. © 1969.