Optical Rotatory Dispersion Studies on Partially Methylated Cellulose

Abstract

ROTATORY dispersion studies have been conducted on a large number of proteins and polypeptides^1-3. We wish to report some preliminary studies on the rotatory dispersion of polysaccharides. The material used for this work was ‘Methocel’ (registered trade mark of the Dow Chemical Company, Midland, Michigan) supplied by the Dow Chemical Co. ‘Methocel’ is a partially methylated cellulose which has the characteristic of being more soluble in cold water than in hot water. This investigation was carried out on material with an intrinsic viscosity of 1.6 (corresponding roughly to a molecular weight of 35,000) and a methyoxyl analysis of 29.5 per cent (1.8 OCH₃ groups/anhydroglucose unit). The method of solubilizing this particular polysaccharide consisted in dispersing the material in boiling water and allowing it to cool to room termperature. Solution A (Figs. 1 and 2) was further cooled to 0° C. overnight and then maintained at room temperature (24° C.). Solution D (Figs. 1 and 2) was maintained at room temperature. The dispersion curves for these two solutions are shown in Fig. 1. The majority of the measurements were carried out on a Keston photoelectric polarimeter attached to the Beckman DU spectrophotometer. The cell was covered with black paper to eliminate any spurious rotation as described in a recent paper by Winkler and Markus⁴. The dispersion curve of solution A from 270 mµ to 600 mµ was obtained on a Rudolph photoelectric spectropolarimeter, model 200 S. (The use of this instrument was kindly permitted by Prof. M. L. Wolfrom of the Chemistry Department, Ohio State University, Columbus, Ohio.) The results using the Keston instrument checked very well with the results on the Rudolph instrument.