Structural stability of (1→3)-β-d-glucan macrocycles

Effects of thermal, alkaline and ultrasonic treatments on scleroglucan stability and flow behavior

“…It has been postulated that, during ultrasonication, polymer changes may be attributed to the stretching through elongational flow fields produced by imploding cavities (Kulicke, Otto, & Baar, 1993). Reversion between different transition states of the triplex and the delay in the appearance of lower M w molecules as a consequence of bond breaking events could account for the apparent stability of these structures (Falch & Stokke, 2001).…”

“…Concerning ultrasonication effects, previous works reported its use for high M w polymer fragmentation (Falch et al, 1999;Falch & Stokke, 2001;Stahmann et al, 1995). Contrary to these observations, the herein tested scleroglucans revealed no signs of fragmentation under the applied conditions, although denaturation was suggested for EPS II after 10 min of ultrasonication (Table 1, Figs.…”

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

“…After re-establishing the neutral conditions the sample was subjected to a thermal treatment, which has shown to increase the stability of the circular species formed. 26,27 More precisely, the renatured sample was heated to 95°C for 2 h, and cooled by being left standing in air.…”

Structural properties of polyC–scleroglucan complexes

“…28 Aliquots of the samples were mixed with 60% aqueous glycerol to a final polysaccharide concentration of 2-4 g/mL and a final weight fraction of glycerol equal to 50%. A small volume of these solutions were sprayed on freshly cleaved mica discs and vacuum dried at 10 À6 Torr for at least 2 h. AFM topographs of scleroglucan and polyC-scleroglucan complexes were obtained using a Digital Instruments Multimode IIIa atomic force microscope equipped with an E-scanner.…”

“…Such rearrangements have previously been suggested to explain the increased structural stability observed for scleroglucan macrocycles exposed to thermal annealing. 28 Upon exposure to 708C, the polyC-scleroglucan complexes disintegrate (Figure 3). This temperature is well below the melting point of scleroglucan triple helixes, which is reported to be 1358C.…”