Molecular characterization of sinistirin

The molecular weight distribution of sinistrin (Inutest ®, Laevosan Ges., Linz, Austria), determined by analytical gel-permeation chromatography, using narrow fractions ($\text{M}$_w$\text{M}$_n< 1.07) obtained by preparative gel-permeation chromatography, covered the range 800–16,000 with $\text{M}$_n  2,500 and $\text{M}$_w  3,500. From viscosity measurements on dilute, aqueous solutions, the relation η]  0.28 X M^0.3 was obtained, indicating a branched molecular structure; the largest molecules can be described by a sphere with r  23 Å. Comparison of the content of glucose and reducing sugars in the fractions with the molecular weight determined by vapour-pressure osmometry indicated that a glucose end-group is present in the majority of the molecules. The percentage of glucose end-groups is higher in the fractions of lower molecular weight. From this finding, speculations on the biosynthesis of sinistrin are made. The specific optical rotation of sinistrin fractions decreases linearly with 1/$\text{M}$_n.