Determination of enantiomers in ephedrine mixtures by polarimetry.

Enantiomeric purities have been measured with precisions that are equivalent to those obtained from chiral chromatography by a simple ligand substitution reaction into the first coordination sphere of Cu(II)-tartrate complexes. The model systems are binary mixtures of the ephedrines. Ligand exchange reactions are done in bulk aqueous media. The detector is polarimetry. Multivariate regression analyses of optical rotation data measured at five wavelengths are used to prepare calibration and prediction models for binary mixtures of the enantiomers.

Induced circular dichroism study of the aqueous solution complexation of cello-oligosaccharides and related polysaccharides with aromatic dyes.

Acetobacter xylinum, grown in the presence of low levels of the water-soluble dye Calcofluor White ST produces a pellicle of cellulose that has no detectable crystallinity. Biological factors of this sort are probably more important than physical factors in controlling the higher order structures of celluloses. Circular dichroism (CD) is induced by complexes that are formed by specific interactions between chiral oligosaccharides and dye molecules. Using CD, equilibrium constants were measured for the association reactions between various dyes with a series of cello-oligosaccharides (n = 2-6), methylcellulose, hydroxypropylcellulose (HPC), amylose, cyclomalto-oligosaccharides (cyclodextrins), and the linear malto-oligosaccharides (n = 3-7). Possible structural features of the complexes are discussed. Dyes that are capable of binding to the higher cello-oligomers in aqueous solutions are the same dyes that modify the solid structure of bacterial cellulose. An analogy between the binding of water-soluble dyes to cello-oligosaccharides and the binding of the cellulose-degrading enzyme, cellobiohydrolase I, to cellulose is discussed.