Physicochemical properties of (1 → 6)‐branched (1 → 3)‐β‐D‐glucans. 1. Physical dimensions estimated from hydrodynamic and electron microscopic data

Abstract

The physical dimensions of several (1-->6) branched (1-->3)-beta-D-glucan samples obtained from different organisms and their derivatives have been studied by electron microscopy, light scattering measurements, viscometry, and gel permeation chromatography. The electron micrographs indicate that in most samples these biopolymers are adequately described as linear worm-like coils. A sample reconstituted from alkaline media appeared as a blend of the linear, circular, and aggregated polymer morphologies. The average mass per unit length, ML = Mw/Lw for the macroscopically linear samples, was estimated to be 2100 +/- 200 g mol-1 nm-1. The parameter ML was determined from the contour lengths obtained by electron microscopy and the molecular weight by light scattering measurements. The observed ML was consistent with the triple-helical structure reported from x-ray diffraction studies and observed degree of side-chain substitution. From the molecular snapshots shown in the electron micrographs, the persistence lengths of these beta-D-glucans were determined to be 140 +/- 30 nm. The experimentally determined intrinsic viscosities were consistent with these estimates of ML and persistence length. Comparison of the molecular weight distributions obtained from gel permeation chromatography and those deduced from the electron micrographs indicates that number and weight average contour lengths are more reliable than z and z + 1 averages.

Probing macromolecular architectures of nanosized cyclic structures of (1→3)-β-d-glucans by AFM and SEC-MALLS

“…Based on the M w in aqueous solution and the weight average contour length (L w ) measured in these electron micrographs, a linear mass density (M L ) equal to 2080 ± 200 g mol À1 nm À1 was estimated for the linear molecules. 14,18 This value of M L is consistent with the proposed triple-helical structure.…”

Macromolecular triplex zipping observed in derivatives of fungal (1 ? 3)-?-D-glucan by electron and atomic force microscopy

“…The present estimate of L pe could be biased toward the more stiffer species in the ensemble compared to that obtained previously 30,31 because chains with intramolecular overlapping chain segments were excluded. These data are therefore considered to be in agreement with previous reports 30,31 and lend support to this scleroglucan sample also being triplex.…”

“…The electron micrographs of scleroglucan revealed a rather stiff, semiflexible structure in agreement with previous reports. 30,31 The scleraldehyde samples resembled the native scleroglucan ( Figure 2). This was found for samples with DS equal 0.4, 0.6 and 1.0 and the DS ϭ 1.0 samples additionally revealed a larger tendency to form aggregated structures.…”

“…Likewise, the correspondence between the structures observed for scleroglucan in the micrographs and the solution properties of such triplehelical (1 3 3)-␤-D-glucans, have been discussed previously. 31 The aim here is to evaluate the above identifications with the reported data of the scleraldehydes and sclerox with various degrees of substitution in aqueous electrolyte solutions. Recently, small-angle x-ray scattering (SAXS) data were reported for scleraldehyde samples with different degrees of substitution.…”

Rheological characterization of schizophyllan aqueous solutions after denaturation–renaturation treatment

“…Both SPG and scleroglucan, as well as lentinan, belong to the family of (1 3 6) branched (1 3 3) -␤-D-glucans where the chemical difference distinguishing the various members mainly is a small variation in the degree of branching. 3,4 In the most recent two decades, SPG has attracted more and more attention due to its interesting molecular conformation and potential antitumor or antiviral properties. 5,6 In aqueous solutions, SPG possesses a very stiff triple-helical conformation.…”