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Induced CD provides evidence for helical solution conformation in cellulosic chains
Author(s) -
Ritcey Anna M.,
Gray Derek G.
Publication year - 1988
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.360270309
Subject(s) - chemistry , chromophore , aqueous solution , polymer , dimer , circular dichroism , cotton effect , cellulose , asymmetry , crystallography , exciton , stereochemistry , photochemistry , organic chemistry , physics , quantum mechanics
Evidence for a helical contribution to the conformation of methylcellulose in dilute solution is given by CD measurements. Congo red binds to methylcellulose in dilute aqueous solution and becomes optically active. The shape of the induced CD spectra is as predicted by exciton coupling for a helical arrangement of chromophores. The magnitude of the induced CD changes reversibly with temperature, decreasing upon heating. The dimer analogue of the polymer, prepared by acid methanolysis, does not show this effect. These observations suggest that the induced optical activity reflects the conformational dissymmetry of the polymer. Analogous experiments with the cellulose oligomers (cellotriose through cellohexaose) show that five anhydroglucose units are necessary before asymmetry is induced upon dye binding.