On the blue color of triiodide ions in starch and starch fractions. II. Characterization of the changes in absorption and circular dichroism spectra of triiodide ions in amylose with the DP

✍ Scribed by Takashi Handa; Hirofumi Yajima

• Publisher: Wiley (John Wiley & Sons)
• Year: 1980
• Tongue: English
• Weight: 927 KB
• Volume: 19
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1980.360190402

✦ Synopsis

Abstract

Three steps appeared in the color change of triiodide ions in amylose with the degree of polymerization (DP), associated with the change in the CD spectra. First, the shoulder around 480 nm developed strikingly from the achromic point of DP 10 to DP 30. Second, the blue color developed critically from DP 30 and deepened on going to DP 100, where the consistent increase in the intensities of the absorption and mutually split CD bands (+,−) was observed. Third, the deep bluing associated with the shallowing of the dual CD band was observed above DP 100. This change depended strongly on the mixing rate of I~2~ with amylose in the presence of excess KI. In particular, the signs of the dual CD band changed from (+,−) to (+,+) for high‐DP amyloses at high I~2~ in the rapid‐mixing system. The first and second phenomena are explained in terms of the enhancements in the short‐ and long‐axis transitions dipoles of the ions in the dimeric unit, respectively, being associated with the change in their spatial configuration due to the augmented shear from the stepwise promotion in the types and number of hydrogen bonds in the complex with the DP. The third phenomenon was attributed to the interactions of the skewed ions located in the knot portions and in the associated helices of the aggregate.