Dextran optical rotation

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

The characterization of dextrans by the optical rotation of their cupram-... 

Dextran forms crystalline, spherulitic complexes with Ca " ", Ba, and La, but not with Mg " and Na. The optical rotation of dextran in aqueous solution is considerably increased by the addition of La and Ba, but only slightly by Ca, Mg, and Na" " acetates. Complex-formation appears to ter the conformation of the polymer chain. A 20% solution of dextran will dissolve — 5% of Fe this solution is used for the treatment of anemia. ... 

Previous VUCD studies have been reported for amylose(14) and, by us, for pustulan (9), and dextran (10). Prior to those works, optical studies of glucan conformation in solution included optical rotation and optical rotatory dispersion measurements to approximately 200 nm (15-20), CD studies of chemically modified glucans (21,22.23.24.25). and perturbation methods applied to glucan-ligand complexes (26-33). 

What is the minimum degree of polymerization necessary for dextran to exhibit properties characteristic of a typical polymer This question should be resolved by examining the molecular weight dependence of its solution properties, although this may be subject to the limitation that native dextran is not a linear polymer but a branched one. The optical rotation data in Figure 2 demonstrate the transition from oligomer to polymer aroxmd the... 

Figure 2. Molecular-weight dependence of the optical rotation of dextran. Data shown by (%) are taken from Turvey and Whelan (2).

The use of the optical rotation detector in HPLC also allows one to determine the molar optical rotation (MDP-1) for the two series (relation 1 Figure 6) for these conditions/ the term ([m] + [A]) is obtained from the slopes [a]D = 192 and 185 is calculated as specific optical rotation of the corresponding polymers amylose and dextran/ respectively. These values are in good agreement with the values given in the literature. 

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