Degrees of long-chain branching in dextrans11Part II of the series G.p.c. Analyses of Polysaccharides.

Kuge, Takashi; Kobayashi, Kimie; Kitamura, Shinichi; Tanahashi, Hiroshi

doi:10.1016/0008-6215(87)80312-9

Cited by 26 publications

(14 citation statements)

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“…Among other properties they also tried to establish the molar mass dependence of the intrinsic viscosity. Unfortunately, they determined the number average molar mass but found a significantly larger exponent than those found by the authors in refs −13. Such behavior has been known for a long time, because despite careful fractionation it is virtually impossible to prepare sufficiently narrow distributions with branched materials.…”

Section: Introductionmentioning

confidence: 60%

“…The results were obtained from SEC-MALLS in combination with a viscometer (VISC.) The filled triangles up and down correspond to the nonfractionated samples and the filled circles with a dot and squares are data from Kuge et al 11 and Senti et al, 13 respectively. The dashed line represents the initial slope at small molar masses, which may be related to linear dextrans.…”

Section: Resultsmentioning

confidence: 99%

“…10 A few other characterizations of dextrans were made earlier with limited instrumental possibilities. [11][12][13][14] A detailed analysis, similar to the present study, was made previously by Kuge et al 11 They applied common gel permeation chromatography and determined first the product M wi [η] i from each slice on the basis of a universal calibration function M[η] as a function of the elution volume v e , which was established for a number of linear and branched glucans in water. The molar mass M wi of the fractions in each slice was then determined with the aid of the molar mass dependence of the intrinsic viscosity, that was established with nonfractionated and fractionated dextrans.…”

Section: Introductionmentioning

confidence: 99%

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Structure Properties of Dextran. 3. Shrinking Factors of Individual Clusters

2001

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Size exclusion chromatography in combination with multiangle laser light scattering and viscometry was applied for the study of the branched structures of commercial dextrans. Shrinking factors g ) Rg,i 2 branch/Rg,i 2 linear and g′ ) [η]i,branch/[η]i,linear were calculated, where the radii of gyration of pullulan were taken as the reference for the derivation of g, For the calculation of the g′ factor, a reference curve was constructed by linear extrapolation of the low molar mass dextran data toward higher molar masses. A power law behavior g′ ) g b η was found with exponent bη ) 0.71 ( 0.05 which is slightly larger than 0.60 as was estimated by Kurata et al. and found with endlinked polystyrene star molecules. The combination of both shrinking factors also allowed us to estimate the Flory draining parameter Φ as a function of molar mass and of g, respectively. The Φ factor was found to increase with the number of branching points of the macromolecules. A quantitative estimation of the number of branching points is possible for randomly branched materials by applying the Zimm-Stockmayer relationship. For a good fit the equation had to be modified by changing the asymptotic power from -0.5 to -0.72. The branching unit was found to have a molar mass of 29 000 g/mol, which corresponds for hyperbranched chains to a chain length of about 90 monomer units between two branching points. The effect of incomplete fractionation is discussed.

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Section: Introductionmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure Properties of Dextran. 3. Shrinking Factors of Individual Clusters

2001

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“…The column system was calibrated using pullulan and linear amylose as previously described. 34 The data for the (1 --* 6 ) - …”

Section: Gel Permeation Chromatographymentioning

confidence: 99%

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

et al. 1993

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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.

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“…22 O decréscimo no índice de polidispersividade 1,72 → 1,42 → 1,10 observado é coerente pois, o número de ramificações nas dextranas tende a diminuir simultaneamente com a redução da sua massa molar (Mw). 6,23,24 Mesmo levando-se em consideração o caráter majoritariamente qualitativo da cromatografia por exclusão por tamanho, com detecção por índice de refração, em nossos experimentos padrões de dextranas com massas molares significativamente distintas apresentaram em função da área do pico, respostas da mesma ordem de grandeza para as mesmas concentrações de dextranas, como observado na Figura 3.…”

Section: Resultsunclassified

Dextranas em açúcares do estado de São Paulo

Aquino¹,

Franco²

2008

Quím. Nova

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Recebido em 15/3/07; aceito em 27/11/07; publicado na web em 8/7/08 DEXTRANS IN SUGARS FROM SÃO PAULO STATE. The characterization of dextran in sugars by size exclusion chromatography (SEC) has been carried out according to the number-average molecular weight (Mn), the weight-average molecular weight (Mw), the Z-average molecular weight (Mz), and the polydispersity (Mw/Mn). The results suggest that all the analyzed thirty sugar samples from São Paulo state were contaminated with two or three different dextran polymers. The collected data clearly point out that the total dextran content together with the mass distribution parameters Mw, Mn, Mz, and Mw/Mn should be considered during the evaluation of the quality of the sugar used for the cachaça sweeting process.

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Degrees of long-chain branching in dextrans11Part II of the series G.p.c. Analyses of Polysaccharides.

Cited by 26 publications

References 24 publications

Structure Properties of Dextran. 3. Shrinking Factors of Individual Clusters

Structure Properties of Dextran. 3. Shrinking Factors of Individual Clusters

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

Dextranas em açúcares do estado de São Paulo

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