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Metachromasy of crystal violet in the presence of poly(α-L-glutamic acid) and the bound-dye spectra determined by the principal/component-analysis method

Authors
Journal
Biophysical Chemistry
0301-4622
Publisher
Elsevier
Publication Date
Volume
12
Issue
2
Identifiers
DOI: 10.1016/0301-4622(80)80055-x

Abstract

Abstract In order to study quantitatively the metachromatic behaviour of crystal violet (CV) in the presence of poly (α-L-glutamic acid), (poly (Glu)), four sets of the absorption spectra of the poly(Glu)-CV system were analyzed by the extended principal-component-analysis (PCA) method. Two classes of CV-Glu complexes, i.e., the bound-CV species, are present in poly(Glu) regardless of its helical and random-coiled conformations over a wide range of the mixing ratios of Glu residues to CV (P/D). The spectra of the bound CV in a low P/D range < 100 (complex I), extracted by the PCA method, are conformation-dependent showing three absorption bands at 506, ca. 550, and 610–620 nm. The spectra of the bound CV in a high P/D range > 100 (complex II) are closely related to, but not identical with, the free CV. The molar fractions of free CV and complexes I and II, evaluated in the P/D range of 0–150, indicate that CV binds more to the random-coiled poly(Glu) than to the helical one. Metachromasy of CV results from a complicated interplay of an unbound and two differently bound species.

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