A simple preparative method for the isolation of amylose and amylopectin from potato starch.

The defatted starch was dispersed in NaOH (1 M) and neutralized with HCl (1 M). The amylose 1-butanol complex is adsorbed on defatted cellulose powder in the solvent system containing acetate buffer (pH 4.8,0.1 M) + urea (2 M) + 1-butanol (8.5%, v/v). The complex adsorbed on cellulose powder is separated by centrifugation (2418 g). The sediment is washed with the solvent system-I to obtain the intermediate fraction. The adsorbed amylose is eluted with urea (2 M) in acetate buffer (pH 4.8, 0.1 M). The amylose, intermediate fraction and amylopectin were precipitated with ethanol, washed free of urea and air dried. They were characterized by determining their blue value and beta -amylolysis limit.

A modified method for the preparation of agarose.

A simple procedure for the preparation of agarose suitable for electrophoresis is developed in which anionic polysaccharides are removed by extracting the agar gel-granules with phosphate buffer (0.03 M, pH 6.8) containing urea (4 M), followed by electrophoresis in the same buffer system. Further, alkali treatment in the presence of sodium borohydride, eliminates electroendosmosis, giving essentially a neutral agarose, as judged by the electrophoretic behaviour of basic substances like crystal violet and cytochrome C. The purified agarose with yields 60-65%, has a sulphur content less than 0.1%, and forms rigid, transparent gels.

Ligand-induced structural changes in amylose partially complexed with iodine.

The influence of complexing agents such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, cyclohexanol and 2-octanol on the formation of a blue coloured amylose - iodine complex (pH 4.8), under suboptimum concentrations of iodine and in the absence of potassium iodide, is studied by recording the absorbance at 640 nm. A drop in absorbance at 640 nm accompanied by a blue shift in the spectrum (640-580 nm) was observed at higher concentrations of the complexing agents. This behaviour of amylose partially complexed with iodine appears to be due to ligand-induced structural changes in the amylose chain. The fall in absorbance at 640 nm observed when the temperature of amylose - iodine complex in the presence of complexing agents is raised, and the subsequent regeneration of the absorbance on cooling, indicates the possible helix to random coil transition of the amylose chain in an aqueous system.