Gel point in physical gels: rheology and light scattering from thermoreversibly gelling schizophyllan

Fuchs, Tania; Richtering, Walter; Burchard, Walther; Kajiwara, Kanji; Kitamura, Shinichi

doi:10.1016/s0966-7822(97)00027-0

Cited by 68 publications

(47 citation statements)

References 33 publications

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“…45 Note that the presence of sorbitol reduces the water activity and thus promotes the entanglement of SPG chains. 30 At the temperature of 21°C, the power laws, represented by Eq. (1), are satisfied.…”

Section: Determination Of Gelation Temperature (T Gel )mentioning

confidence: 99%

“…29 -31 With respect to the gelation mechanism, they first thought that sorbitol reduces the water activity and thus SPG triple helices aggregate to form junction zones. 30 Later, through fitting SAXS profiles, they reconcluded that sorbitol dissociates a part of triple-stranded helices and bridges the dissociated parts to form junction zones. Moreover, no proof from SAXS results could confirm the presence of aggregation of triple helices.…”

Section: Introductionmentioning

confidence: 99%

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Gelation behaviors of schizophyllan‐sorbitol aqueous solutions

Fang

Nishinari

2003

Biopolymers

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On addition of D-sorbitol, schizophyllan (SPG) aqueous solution forms a thermoreversible gel upon cooling. The gelation process is characterized by rheology, differential scanning calorimetry (DSC), and optical rotation measurement (ORD). It is found that the Winter-Chambon criterion works well in determining the critical gelation point of the present system, although the criterion has been scarcely applicable to systems that show weak-gel properties even before gelation. Moreover, ORD and DSC results indicate that a disordered to ordered conformational change accompanies the gelation process, which is attributed to the transition from SPG triple helix II to I. The gelation temperature of SPG-sorbitol aqueous solution is almost independent of SPG concentration in the examined concentration range and is slightly decreased by lowering SPG molecular weight, while greatly influenced by sorbitol content. The gelation is considered to be induced by the transition from SPG triple helix II to I, which leads to a three-dimensional network constituted by the extremely entangled and stiff SPG triple helices I. Furthermore, it is proved that neither junction zone nor aggregation of SPG triple helices is involved in the SPG-sorbitol gels. The SPG-sorbitol gel is structurally like a solution that is unable to flow within a timescale of usual observation.

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Section: Determination Of Gelation Temperature (T Gel )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gelation behaviors of schizophyllan‐sorbitol aqueous solutions

Fang

Nishinari

2003

Biopolymers

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“…In an earlier work, 5 sorbitol was considered to reduce a water activity and thus schizophyllan triplestranded helices aggregate to form junction zones. However, no proof was found from the SAXS measurements to confirm the formation of the junction zone by aggregation of triple-stranded helices.…”

Section: Gelation Process Of Schizophyllanmentioning

confidence: 99%

“…The present work aims to answer the question how schizophyllan forms gel in sorbitol aqueous solution. In an earlier work, 5 sorbitol was considered to reduce a water activity and thus schizophyllan triple-stranded helices aggregate to form junction zones. We examine the structural change of schizophyllan caused by solgel transition in sorbitol aqueous solution by means of small-angle X-ray scattering (SAXS).…”

mentioning

confidence: 99%

“…5 Since SAXS contains the structural information in the order of a few A to several hundreds A, the structural change of schizophyllan induced by gelation is traced in principle on a molecular level. Here the strategy is to fit the observed SAXS profile with an appropriate molecular model, which can be constructed from the crystallographic data and other results.…”

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confidence: 99%

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Structural Aspect of Gelation in Schizophyllan/Sorbitol Aqueous Solution

Maeda

Yuguchi

Kitamura

et al. 1999

Polym J

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ABSTRACT:Although schizophyllan undergoes no gelation by itself in its aqueous solution, the addition of sorbitol results in the formation of transparent gel at lower temperatures. The mechanism of the gel formation was discussed from the structural analysis of schizophyllan in the aqueous solution with and without sorbitol, based on the results of small-angle X-ray scattering. Here sorbitol was found to disentangle a part of triple-stranded helices and bridge the disentangled parts which serve as a crosslinking domain.KEY WORDS SchizophyllaniSorbitol I Small-Angle X-Ray Scattering I Gel I Viscoelasticity I Broken Rod Model I Molecular Model I Schizophyllan is an extracellular polysaccharide produced by fungus Schizophyllum commune, and is known to suppress tumor growth. It consists of (I-+ 3)-D-/3-glucan with a (1-+6)-D-{3-glucan branch per every 3 units as shown in Figure I. Schizophyllan is non-ionic and water-soluble. It assumes a triple-stranded helical conformation in aqueous solution as confirmed from the measurements of the molecular weight and viscosity 1 and by calorimetric measurements, 2 whereas in dimethyl sulfoxide (DMSO) it has a single coiled conformation. 3 Thus in water schizophyllan is rod-like and does not form gel by itself.Addition of D-sorbitol induces the thermoreversible gelation of schizophyllan aqueous solution, 4 · 5 where the gel temperature depends only on the sorbitol concentration. The present work aims to answer the question how schizophyllan forms gel in sorbitol aqueous solution. In an earlier work, 5 sorbitol was considered to reduce a water activity and thus schizophyllan triple-stranded helices aggregate to form junction zones. We examine the structural change of schizophyllan caused by solgel transition in sorbitol aqueous solution by means of small-angle X-ray scattering (SAXS). If the above conjecture on the junction zone is correct, we should observe the thicker cylindrical objects corresponding to the aggregated triple-stranded helices in gel.The work complements the rheological observation on gelation in the same system. 5 Since SAXS contains the structural information in the order of a few A to several hundreds A, the structural change of schizophyllan induced by gelation is traced in principle on a molecular level. Here the strategy is to fit the observed SAXS profile with an appropriate molecular model, which can be constructed from the crystallographic data and other results. By doing so, we may hope to visualize the gelation process of schizophyllan in sorbitol aqueous solution. ' To whom all correspondence should be addressed. 530EXPERIMENTAL D-sorbitol was dissolved in distilled and deionized water by heating the solutions to 90°C, and the solutions of four different sorbitol concentrations (0, 1. 5, 2. 7, and 4.0 moll-1 ) were prepared. After cooling the sorbitol solutions to 60°C, NaN3 (5 X 10-3 moll-1 ) was added in order to suppress bacteria growth. Schizophyllan (M w = 45 x I 0 4 ) was dissolved in those solutions to the total concentration of 16.3 mg ml-1...

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Polysaccharides from Microorganisms, Plants and Animals

Sutherland

2002

Biopolymers Online

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Introduction Polysaccharide Composition and Structure Microbial Polysaccharide Composition and Structure Composition and Structure of Yeast and Other Fungal Polysaccharides Composition and Structure of Plant and Algal Polysaccharides Polysaccharide Synthesis Bacterial Synthesis of Polysaccharides Synthesis of Plant and Animal Polysaccharides The Physical Properties and Function of Polysaccharides Commercialization of Polysaccharides New Products

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Gel point in physical gels: rheology and light scattering from thermoreversibly gelling schizophyllan

Cited by 68 publications

References 33 publications

Gelation behaviors of schizophyllan‐sorbitol aqueous solutions

Gelation behaviors of schizophyllan‐sorbitol aqueous solutions

Structural Aspect of Gelation in Schizophyllan/Sorbitol Aqueous Solution

Polysaccharides from Microorganisms, Plants and Animals

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