Conformational properties of hyperbranched hetero-polysaccharides by SEC-MALS-IV

Significance of the Topic

Acacia gums are complex hyperbranched hetero-polysaccharides widely used as stabilizers, emulsifiers and thickeners in food, pharmaceutical and materials applications. Understanding their molecular architecture is essential to control rheology, functionality and performance in industrial formulations.

Objectives and Study Overview

• Compare conformational properties of Acacia senegal and Acacia seyal gums.
• Assess the impact of branching density on macromolecular size, shape and anisotropy.
• Demonstrate the capabilities of SEC-MALS-IV for detailed structural analysis.

Methodology and Instrumentation

Solutions of Acacia gum (1 mg/mL) were separated by size-exclusion chromatography on a Shimadzu HPLC system using Shodex OHPAK SB columns at 30 °C. The eluate was characterized online with a DAWN multi-angle light scattering detector, a ViscoStar differential viscometer and an Optilab refractive index detector. Measurements were analyzed with ASTRA software using a dn/dc of 0.145 mL/g. Mobile phase: 0.1 M LiNO₃ with 0.02 % NaN₃ at 1 mL/min.

Main Results and Discussion

• MW distributions showed A. seyal macromolecules to have higher molecular weights than A. senegal at the same hydrodynamic volume, indicating a more compact architecture in A. seyal.
• Conformation plots (Rg vs M) exhibited two scaling regimes for both gums, with scaling exponents (νg) reflecting transitions from near-spherical to ellipsoidal shapes and increasing compactness at higher molecular weight.
• Intrinsic viscosity analysis (Mark–Houwink α) yielded a single low exponent (α≈0.28) for A. seyal, indicating a homogeneous compact distribution, while A. senegal displayed three regimes (α≈0.44, 0.78, 0.44), consistent with varying anisotropy across molecular weight ranges.
• The asymmetry parameter ρ (Rg/Rh) ranged from ~0.75 to 1.2, confirming conformational transitions from spheroidal to oblate and prolate ellipsoids and increasing anisotropy with molecular weight.

Benefits and Practical Applications

These conformational insights enable targeted optimization of Acacia gum-based ingredients for viscosity control, texture modification and stability in food, pharmaceutical and cosmetic formulations. Detailed structural data support quality control and formulation consistency.

Future Trends and Applications

• Coupling SEC-MALS-IV with alternative fractionation techniques (e.g. AF4) to extend molecular weight coverage.
• Integration with microfluidic and rheo-optical platforms for dynamic conformation monitoring under flow.
• Predictive design of tailored hyperbranched polymers based on quantitative branching and anisotropy data.

Conclusion

SEC-MALS-IV provides a comprehensive approach to quantify size, shape and branching in hyperbranched hetero-polysaccharides. The distinct conformational behaviors of A. seyal and A. senegal reflect differences in branching density and anisotropy, with direct implications for their functional performance.

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