Dextran series structures

Fig. 1.—Relation24 Between Movement in a Paper Chromatogram and Structure of Oligosaccharides. 1 = Galactan series (reducing) 2 = Dextran series 3 — Amyl-ose series 4 = Inulin series.

Assuming that all a-[l->6)-linkages are in the dextran backbone, our permethylation g.l.c.-m.s. data [which indicate that only the residues shown above are present in this series of dextrans) are consistent with a polymeric structure that is comb-like with side branches a single residue long. 

Meyer, F.A., Koblentz, M. and Silberberg, A. (1977) Structural investigation of loose connective tissue by using a series of dextran fractions as non-interacting macromolecular probes. Biochem. J., 161, 285-291. 

Many pioneer structural investigations were carried out in other groups of polysaccharides, notably on inulin, on the xylan from esparto, on the mannan from yeast and on a series of bacterial polysaccharides amongst the latter were included somatic and lipoid-bound polysaccharides from M. tuberculosis. Noteworthy also was the work on the dextran produced by strains of Leuconostoc, which is showing grqat promise as a blood plasma substitute. 

V = elution volume of small molecule. The standards used to derive these calibra- 0 tion curves are frequently dextrans or sulphonated polystyrenes, although this tends Z to (incorrectly) assume a linear structure for the biological macromolecule. The m behaviour of proteins and peptides on SEC columns is more accurately represented by the use of globular proteins as calibration standards. Anderson and Stoddart observed (3) that in the middle of the Kj range (/fp = 0.15—0.80) these theoretical plots are y essentially linear (see Figure 2), and they can therefore assist in the choice of SEC CO column. It is consequently graerally best (4) to choose a column on which the molecules of interest elute near the middle of the calibration curve, where this linearity occurs. Occasionally, two or more columns may be used in series. When connected in series, columns of the same pore size will increase resolution, whilst columns of different pore size will broaden the range of molecidar sizes separated. 

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