Application of conductivity studies and polyelectrolyte theory to the conformation and order-disorder transition of xanthan polysaccharide

Jones, S. A.; Goodall, David M.; Cutler, A. Norman; Norton, Ian T.

doi:10.1007/bf00263683

Cited by 21 publications

(20 citation statements)

References 29 publications

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“…(l), (18) and (24) for different conformations, random-coil, single-helix and double-helix, over that temperature range, it appeared that at low temperatures the data were consistent with a single rather than a double helix [75]. In systems without added 1:l salt, a transition helix + coil is observed at -33 'C, with Ab = 0.05 nm, whereas in systems with added 1:l salt, the order-disorder temperature appeared to be = 62 'C with Ab -0.55 nm.…”

Section: Conformational Changes Of Polyionsmentioning

confidence: 88%

Conductometric analysis of polyelectrolytes in solution

Leeuwen¹,

Cleven²,

Valenta³

1991

Pure and Applied Chemistry

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Section: Conformational Changes Of Polyionsmentioning

confidence: 88%

Conductometric analysis of polyelectrolytes in solution

Leeuwen¹,

Cleven²,

Valenta³

1991

Pure and Applied Chemistry

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“…Figure 5 of Ref. 41 shows that with decreasing T, the optical rotation in aqueous KBr levels off at a value larger for a lower salt concentration. This behavior is similar to what was observed for Na samples1,'2'13 disordered once a t high T, indicating that the "ordered form" of Jones et al at low salt concentrations is largely disordered and differs from the one we consider the ordered form.…”

Section: Discussionmentioning

confidence: 99%

“…Salt-free solutions of Jones et al 41 were dialyzed against deionized water for 48 h. Although the temperature of the solutions in the dialysis is not given in Ref. 41, the double-helical structure of the polysaccharide is likely to be broken in water by strong electrostatic repulsions between charged groups; in order to prepare solutions of double-stranded xanthan, salt-free solutions of purified high molecular weight sample (Na salt) need to be carefully treated below 15°C (preferably below 10°C),16,32 probably because separated singlechain portions in dimers tend to aggregate randomly instead of complete pairing when the solvent condition is changed to that favorable for the double helix.…”

Section: Discussionmentioning

confidence: 99%

Order–Disorder conformation change of xanthan in 0.01M aqueous sodium chloride: Dimensional behavior

Liu

Norisuye

1988

Biopolymers

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SynopsisWeight-average molecular weights M,, second virial coefficients, and z-average radii of gyration (S2):/2 were determined by light scattering as a function of temperature T for four sodium salt samples of xanthan in 0.01M aqueous NaCI, in which the polysaccharide undergoes an order-disorder conformation change with increasing T. The data for (S2):/' and 44, at 25 and 80"C, the lowest and highest temperatures studied, confirmed the previous conclusion that the predominant conformation at the former T, i.e., in the ordered state, is a double helix, while that at the latter T, i.e., in the disordered state, is a dimerized coil expanded by electrostatic repulsions between charged groups of the polymer. As T was increased from 25 to W C , (SZ):/' sigmoidally decreased or increased depending on the dimer's molecular weight. This temperature dependence of (S2):/2 and that determined elsewhere for a high molecular weight sample were found to be described almost quantitatively by a simple dimer model in which the double helix melts from both ends, when the double-helical fraction in the dimer at a given T estimated previously from optical rotation data was used.

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“…Models specifically developed for water-soluble synthetic polymers, appear to be suitable for this specific problem (Bekiranov, Bruinsma, & Pincus, 1997;De Gennes, 1991;Matsuyama & Tanaka, 1990). On the other hand, many food polymers, such as various polysaccharides are electrically charged, and for these strongly interacting systems, poly-electrolyte theories have to be used (Jones, Goodall, Cutler, & Norton, 1987). The variation of strength of interactions has also dramatic consequences in another large family of foods: the colloidal dispersions.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium and non-equilibrium structures in complex food systems

Mezzenga

2007

Food Hydrocolloids

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The physics ruling the macroscopic behaviour of foods is discussed in a few selected examples in which the equilibrium/nonequilibrium nature can be directly related to the typical length scale of the food structure and the specific interaction strength, the latter describing the decrease in specific free energy (e.g., per mole of species or per single event) when going from a non-equilibrium to the equilibrium configuration. Liquid-crystalline phases in foods, such as those based on self-assembled lipids and water, are discussed as an example of equilibrium system, in which low correlation length scales ($nm) enable very-short times to re-organize molecules into equilibrium configurations. High internal phase emulsions and dry foams where length scales are very large ($10 1 -10 4 mm), are discussed as a typical example of non-equilibrium system, which however, can be stable for long times owing to the high free energy barrier and the large correlation lengths. Finally double emulsion systems are considered as an example where both interaction strength and correlation lengths have intermediate values. This allows tuning morphologies and making equilibrium behaviour to prevail over non-equilibrium by suitably tailoring the energetic interactions. In particular the case of osmotic pressure in the water phase of water/oil/water double emulsions is discussed as a viable route to control interaction strength in complex food systems.

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Application of conductivity studies and polyelectrolyte theory to the conformation and order-disorder transition of xanthan polysaccharide

Cited by 21 publications

References 29 publications

Conductometric analysis of polyelectrolytes in solution

Conductometric analysis of polyelectrolytes in solution

Order–Disorder conformation change of xanthan in 0.01M aqueous sodium chloride: Dimensional behavior

Equilibrium and non-equilibrium structures in complex food systems

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