Mechanism and dynamics of conformational ordering in xanthan polysaccharide

Norton, Ian T.; Goodall, David M.; Frangou, S.A.; Morris, Edwin R.; Rees, David A.

doi:10.1016/0022-2836(84)90354-1

Cited by 239 publications

(86 citation statements)

References 41 publications

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“…30 This difference is more pronounced in synthetic polymers than natural polymers 31 temperature-ionic strength conditions. 32 Even lower values (~ 1.00) were observed for EPS1190…”

Section: Resultsmentioning

confidence: 95%

Biophysical Analysis of the Molecular Interactions between Polysaccharides and Mucin

et al. 2015

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Mucoadhesive materials adhere persistently to mucosal surfaces. A mucoadhesive delivery system could therefore facilitate the controlled release of drugs and optimize their bioavailability in mucosal tissues. Polysaccharides are the most versatile class of natural polymers for transmucosal drug delivery. We used microviscosimetry to explore the mucoadhesion of a library of polysaccharide families with diverse structural characteristics as a first step towards the rational design of mucoadhesive polysaccharide-based nanoformulations. Here we show that the magnitude of deviation between the viscosity of mixed polysaccharide-mucin solutions and the corresponding individual stock solutions can indicate underlying molecular interactions. We found that nonlinear monotonic curves predicted a correlation between the magnitude of interaction and the ability of polysaccharide coils to contract in the presence of salt (i.e. chain flexibility). Charge-neutral polysaccharides such as dextran and Streptococcus thermophilus exopolysaccharide did not interact with mucin. Synchrotron small-angle X-ray scattering (SAXS) data supported the previously described structural features of mucin. Furthermore, high-q scattering data (i.e. sensitive to smaller scales) revealed that when mucin is in dilute solution (presumably in an extended conformation) in the presence of low-Mw alginate, its structure resembles that observed at higher concentrations in the absence of alginate. This effect was less pronounced in the case of high-Mw alginate but the latter influenced the bulk properties of mucin-alginate mixtures (e.g. hydrodynamic radius and relative viscosity) more prominently than its low-Mw counterpart.

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“…30 This difference is more pronounced in synthetic polymers than natural polymers 31 temperature-ionic strength conditions. 32 Even lower values (~ 1.00) were observed for EPS1190…”

Section: Resultsmentioning

confidence: 95%

Biophysical Analysis of the Molecular Interactions between Polysaccharides and Mucin

et al. 2015

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“…However, the molecular origin of the observed changes in the specific optical rotation accompanying the transition is mainly unknown, but it has been shown that removal of pyruvate has an effect on the magnitude of the optical r o t a t i~n .~.~ Some information has also been obtained from CD studies of xanthan near 200 nm, 3,9,10 showing that the overall change in ellipticity upon heating above the transition temperature is negative, whereas the change in optical rotation at higher wavelengths is positive, indicating that the CD bands corresponding to the optical rotation lie Complementary information on the conformational transition may be obtained by other physical methods such as nmr3 or differential scanning calorimetry (DSC). "-" The latter method yields a thermodynamic quantity, the transition enthalpy (AHca,), in addition to the transition temper-…”

Section: Introductionmentioning

confidence: 99%

Temperature‐Induced conformational transition in xanthans with partially hydrolyzed side chains

et al. 1993

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The conformational properties of xanthans with partially hydrolyzed side chains were investigated by optical rotation, CD, and differential scanning calorimetry (DSC). All variants displayed the well-known temperature-driven, cooperative order-disorder transition, and both optical rotation and DSC showed that the transition temperature was essentially independent of the content of terminal beta-mannose. It was found that up to 80% of the changes in the specific optical rotation accompanying the transition reflects conformational changes linked to the terminal beta-mannose in the side chains. Modification of the side chains also affected the CD when xanthan was in the ordered state, but in this case the data suggest that the glucuronic acid is the major component determining the magnitude of the CD signal. DSC measurements showed that the transition enthalpy (delta Hcal) increased linearly with the fraction of beta-mannose, again indicating that a significant part (up to 80%) of delta Hcal reflects conformational changes in the side chains. The conformational transition of the xanthan variants generally showed a higher degree of cooperativity (sharper transition) than unmodified, pyruvated xanthan. Calculation of the cooperativity parameter sigma by means of the Zimm-Bragg theory (OR data) or from the ratio between delta Hcal and the van't Hoff enthalpy (delta HvH) using DSC data showed a correlation between sigma and the content of beta-mannose, but the two methods gave different results when the content of beta-mannose approached 100%. The ionic strength dependence of the transition temperature, expressed as d (log I)/d(T-1m), was nearly identical for intact xanthan and a sample containing only 6% of the terminal beta-mannose. Application of the Manning polyelectrolyte theory does not readily account for the observed delta Hcal values, neither does it provide new information on the nature of the ordered and disordered conformations in xanthan.

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“…Experimentally, DH can be determined from integration of the DSC curves. The ratio DH vH / DH [49][50][51] represents the cooperative unit size, which is related to the cooperativity parameter in the ZimmBragg theory 52 for the coil-to-single-helix transition.…”

Section: Figurementioning

confidence: 99%

“…51 For the coil-to-double-helix transition of Nagellans, some qualitative information can be obtained from Eq. (6).…”

Section: Figurementioning

confidence: 99%

Thermally induced coil‐to‐helix transition of sodium gellan gum with different molar masses in aqueous salt solutions

et al. 2005

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Using 5 samples of well-purified Na-gellans (Na-gellans G1-G5, weight-average molar mass M(w) = 120 x 10(3)-32 x 10(3) at 40 degrees C), the effects of molar mass on the coil-to-double-helix transition in aqueous solutions with 25 mM NaCl were studied by light scattering and circular dichroism (CD) measurements, viscometry, and differential scanning calorimetry (DSC). From the temperature dependence of M(w), molar ellipticity at 201 nm [theta]201, intrinsic viscosity [eta], and DSC exothermic curves, it was found that the coil-to-double-helix transitions for G1-G5 samples took place at almost the same temperature. The [eta] and M(w) obtained in the temperature range from 40 to 25 degrees C can be explained by a simple coil/double-helix equilibrium model using the double-helix contents determined from CD data. The van't Hoff's transition enthalpy deltaH(vH) of Na-gellans depended on M(w). It is concluded that the coil-to-double-helix transitions of Na-gellans are all-or-none type transitions, and are accelerated with increasing M(w).

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Mechanism and dynamics of conformational ordering in xanthan polysaccharide

Cited by 239 publications

References 41 publications

Biophysical Analysis of the Molecular Interactions between Polysaccharides and Mucin

Biophysical Analysis of the Molecular Interactions between Polysaccharides and Mucin

Temperature‐Induced conformational transition in xanthans with partially hydrolyzed side chains

Thermally induced coil‐to‐helix transition of sodium gellan gum with different molar masses in aqueous salt solutions

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