Revealing the Compact Structure of Lactic Acid Bacterial Heteroexopolysaccharides by SAXS and DLS

TY - JOUR

T1 - Revealing the Compact Structure of Lactic Acid Bacterial Heteroexopolysaccharides by SAXS and DLS

AU - Khan, Sanaullah

AU - Birch, Johnny

AU - Harris, Pernille

AU - Van Calsteren, Marie Rose

AU - Ipsen, Richard

AU - Peters, Günther H J

AU - Svensson, Birte

AU - Almdal, Kristoffer

PY - 2017

Y1 - 2017

N2 - Molecular structures of exopolysaccharides are required to understand their functions and the relationships between the structure and physical and rheological properties. Small-angle X-ray scattering and dynamic light scattering were used in conjunction with molecular modeling to characterize solution structures of three lactic acid bacterial heteroexopolysaccharides (HePS-1, HePS-2, and HePS-3). Values of radius of gyration RG, cross-sectional radius of gyration RXS, approximate length L, and hydrodynamic diameter were not directly proportional to the molar mass and indicated the HePSs adopted a compact coil-like rather than an extended conformation. Constrained molecular modeling of 15000 randomized HePS-1 conformers resulted in five best-fit structures with R factor of 3.9-4.6% revealing random coil-like structure. φ and ψ angle analysis of glycosidic linkages in HePS-1 structures suggests Galf residues significantly influence the conformation. Ab initio scattering modeling of HePS-2 and HePS-3 gave excellent curve fittings with χ2 of 0.43 and 0.34 for best-fit models, respectively, compatible with coil-like conformation. The findings disclose solution behavior of HePS relevant for their interactions with biomacromolecules, for example, milk proteins.

AB - Molecular structures of exopolysaccharides are required to understand their functions and the relationships between the structure and physical and rheological properties. Small-angle X-ray scattering and dynamic light scattering were used in conjunction with molecular modeling to characterize solution structures of three lactic acid bacterial heteroexopolysaccharides (HePS-1, HePS-2, and HePS-3). Values of radius of gyration RG, cross-sectional radius of gyration RXS, approximate length L, and hydrodynamic diameter were not directly proportional to the molar mass and indicated the HePSs adopted a compact coil-like rather than an extended conformation. Constrained molecular modeling of 15000 randomized HePS-1 conformers resulted in five best-fit structures with R factor of 3.9-4.6% revealing random coil-like structure. φ and ψ angle analysis of glycosidic linkages in HePS-1 structures suggests Galf residues significantly influence the conformation. Ab initio scattering modeling of HePS-2 and HePS-3 gave excellent curve fittings with χ2 of 0.43 and 0.34 for best-fit models, respectively, compatible with coil-like conformation. The findings disclose solution behavior of HePS relevant for their interactions with biomacromolecules, for example, milk proteins.

U2 - 10.1021/acs.biomac.6b01597

DO - 10.1021/acs.biomac.6b01597

M3 - Journal article

C2 - 28042938

AN - SCOPUS:85015158330

SN - 1525-7797

VL - 18

SP - 747

EP - 756

JO - Biomacromolecules

JF - Biomacromolecules

IS - 3

ER -