Molecular configuration of amylose and its complexes in aqueous solutions. Part IV. Determination ofDP of amylose by measuring the concentration of free iodine in solution of amylose-iodine complex

Autor: J. Szejtli, S. Augustat, M. Richter
Rok vydání: 1968
Předmět:
Zdroj: Biopolymers. 6:27-41
ISSN: 1097-0282
0006-3525
DOI: 10.1002/bip.1968.360060103
Popis: In aqueous solutions of the amylase–iodine complex the concentration of free iodine [If]v after reaching equilibrium (or closely approximating it) is determined by the following factors: temperature, pH, concentration of iodide ions and amylose, and DP of amylose. In the present paper the role of temperature, amylose concentration, and DP has been investigated. At half-saturation of amylose by iodine, the reciprocal value of free iodine defines the equilibrium constant: 1/[If]v = K. The relation between [If]v, in normality and temperature is the following: 5 + log [If]v = −(2.132/T) + 8.52, for DPn = 1290, 0.4 mg. amylose in 100 ml. 0.1N HCl. The value of the energy of activation Ea between 2 and 52°C. is 9.72 kcal./mole. The influence of amylose concentration [Am] on photometrically determined [If]v, at 20°C, in the range of 0.1–1.2 mg./100 ml. 0.1 N HCl for DPn = 1290 is: 5 + log [If]v = 0.209 − 0.047 log [Am]. At [Am] = 0.6 mg. amylose/ 100 ml. 0.1 N HCl and 20°C, the value of [If]v depends on DPn as follows: 5 + log [If]v = 0.085 = + 0.222 log (104/DPn). These above equations are summarized by the relation: [If]v = exp {16.865 − (Ea/RT)}[Am]0.047(104/DPn)0.222 ×10−5 Considering that the determination of [If]v by automatic photometric titration can be performed quickly and with appropriate reproducibility, this method is convenient for a rapid empirical and approximate determination of DP of amylose on a microscale. The iodine-binding capacity [IBC] as well as the value of λmax, have been also investigated as functions of DPn, by photometric and by amperometric titration.
Databáze: OpenAIRE
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