Sodium with amylose-iodine complex

The concentration of the competing ligand (K0.5) required to reduce the absorbance of amylose-SDS- " iodine-complex (Amax) to half, as compared with the blank(64o nm) was determined by using the sequence-1, which gave maximum reduction in the absorbance. Por these experiments the system described for the study of influence of SDS on the amylose-iodine-complex was used. The concentration of amylose(0.07 mg) and iodine(BVK - 0.6 ml) was kept constant and the concentration of the competing ligands such as SDS-(1.Ox 10 M), sodium stearate-(5.0 x 10 5 m), sodium c... 

A method of determining airborne iodine has also been reported.241 Here, iodine is absorbed into 5% aqueous KI and spectrophotometrically determined at 590 nm in the form of its complex with starch. This method is selective with respect to bromine and chlorine, and the sensitivity of this method is 0.25 mg of I2 per m3 of air. The concentration of the, 31I isotope in water can be determined by a method involving isotope exchange in the starch-iodine complex.242 Flow-injection determination of ascorbic acid (0.1-40 mg/mL) has been proposed.243 Iodine is generated in the flow system as I3- ions, which are in turn exposed to starch to produce a steady signal at 350 and 580 nm. Ascorbic acid provides inversed maxima which are measured. This method is recommended for analysis of ascorbic acid in fruit juice, jam, and vitamin-C preparations. Use of the blue complex has also been reported for determination of sodium dichloro-isocyanurate in air.244 Obviously the blue reaction is applicable in the determination of amylose, amylopectin, and starch,245-252 as well as modified starches.245,253-255... 

The Interaction of Sodium Dodecyl Sulfate, a Competing Ligand, with Iodine Complexes of Amylose and Amylopectin... 

Figure 4. Absorption spectra of amylose-SDS-iodine complex in acetate buffer, pH 4.8, for three different sequences (I, 2, and 3). (A) The iodine was reduced with sodium thiosulfate, equilibrated at 60°C for 30 min, cooled to 30°C, and reiodinated. (B) The iodine was reduced with sodium thiosulfate, equilibrated at 30°C for 30 min, and reiodinated. (C) Control.

Amylose is a unique polysaccharide which forms a helical blue-coloured complex with iodine (I5). It also forms helical complexes with a variety of organic compounds such as 1-butanol, 1-pentanol, cyclohexanol, SDS etc. The interaction of SDS, a competing ligand with iodine (I ) complexes of amylose and amylopectin is studied spectrophotometrically. It is observed that the reduction in absorbance at 640 nm accompanied by the blue shift (640-570 nm) in the absorption spectrum is governed by the sequence of addition of the reagents, implying that this Interaction is closely associated with the coil—>hellx transition of the polymer chain. Perturbation of this complex with sodium thiosulphate and urea has revealed that the transition from helix—>coil is rather sluggish and hydrophobic interactions play an important role in the stability of this complex. 

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