Unravelling a Direct Role for Polysaccharide β‐Strands in the Higher Order Structure of Physical Hydrogels. Issue 16 (23rd March 2017)

• Record Type: Journal Article
• Authors: Rüther, Anja; Forget, Aurelien; Roy, Anjan; Carballo, Carolina; Mießmer, Florian; Dukor, Rina K.; Nafie, Laurence A.; Johannessen, Christian; Shastri, V. Prasad; Lüdeke, Steffen
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 16(2017)
• Page Start: 4603
• Page End: 4607
• Publication Date: 2017-03-23
• Subjects: density functional calculations -- hydrogels -- polysaccharides -- Raman optical activity -- spectral fitting; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201701019
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The mechanical properties of agarose‐derived hydrogels depend on the scaffolding of the polysaccharide network. To identify and quantify such higher order structure, we applied Raman optical activity (ROA)—a spectroscopic technique that is highly sensitive toward carbohydrates—on native agarose and chemically modified agarose in the gel phase for the first time. By spectral global fitting, we isolated features that change as a function of backbone carboxylation (28, 40, 50, 60, 80, and 93 %) from other features that remain unchanged. We assigned these spectral features by comparison to ROA spectra calculated for different oligomer models. We found a 60:40 ratio of double‐ and single‐stranded α‐helix in the highly rigid hydrogel of native agarose, while the considerably softer hydrogels made from carboxylated agarose use a scaffold of unpaired β‐strands. Abstract : Agarose hydrogels are stiff but chemical carboxylation of the polysaccharide backbone leads to formation of soft gels. Carboxyl groups prevent interchain organization of the polysaccharide into double helices, thereby promoting a β‐strand conformation instead. Raman optical activity was used to identify and quantify the higher order polysaccharide structure directly in the gel phase.