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On the blue color of triiodide ions in starch and starch fractions. III. Resonance Raman spectra of bluing species in amylose
Author(s) -
Handa Takashi,
Yajima Hirofumi,
Kajiura Teruo
Publication year - 1980
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1980.360191004
Subject(s) - chemistry , raman spectroscopy , analytical chemistry (journal) , degree of polymerization , amylose , triiodide , resonance (particle physics) , spectral line , ion , starch , polymerization , polymer , chromatography , atomic physics , optics , organic chemistry , dye sensitized solar cell , electrolyte , physics , electrode , astronomy
In order to clarify the characteristics of the basic units responsible for the blue coloring of iodine/iodide in amylose, we made a resonance Raman spectroscopic study at several KI concentrations using excitation by Ar + , He‐Ne, and Kr + lasers and amyloses with the degrees of polymerization (DP) of 30, 100, 300, and 1000. Similar Raman spectra were observed, regardless of the KI and I 2 concentrations, DP, and excitation wavelengths. Four Raman lines appearing at 159, 111, 55, and 27 cm −1 were obviously fundamental tones, with a degree of depolarization ρ of ca. 1/3 for every spectrum. However, the internal ratios of the intensities of the 159, 55, and 27 cm −1 lines to that of the 111‐cm −1 line decreased with increasing KI concentration. Based on the value of ρ, the assignment of the fundamental lines was made by taking a schematic model of the true motions as a projection in separately analyzing the modes of stretching and bending vibrations for a pseudolinear polyiodide chain, which we found to be perturbed by the external forces of the amylose lattice. In accordance with the variation of the force constants from the assignment of the spectra associated with the change in the composition of the bound species, it was concluded that the basic unit changed from I 6 2−to I 10 2−through I 8 2−with decreasing KI concentration.