Adsorption of Arabinoxylan on Cellulosic Surfaces: Influence of Degree of Substitution and Substitution Pattern on Adsorption Characteristics

Köhnke, Tobias; Östlund, Åsa; Brelid, Harald

doi:10.1021/bm200437m

Cited by 134 publications

(126 citation statements)

References 46 publications

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“…This observation is contradictory to previous studies of in vitro adsorption of xylans from solution onto cellulose surfaces, in which a lower degree of substitution was correlated to a higher level of xylan adsorption (Köhnke et al, 2008(Köhnke et al, , 2011Bosmans et al, 2014). Additionally, technical xylans with lower glycosyl substituents formed during chemical pulping and readsorbed onto cellulose microfibrils improve pulp strength (Danielsson and Lindström, 2005).…”

Section: Discussioncontrasting

confidence: 74%

Regular Motifs in Xylan Modulate Molecular Flexibility and Interactions with Cellulose Surfaces

et al. 2017

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ORCID IDs: 0000-0003-0277-2269 (J.B.); 0000-0001-6732-2571 (J.W.); 0000-0003-3572-7798 (F.V.).Xylan is tightly associated with cellulose and lignin in secondary plant cell walls, contributing to its rigidity and structural integrity in vascular plants. However, the molecular features and the nanoscale forces that control the interactions among cellulose microfibrils, hemicelluloses, and lignin are still not well understood. Here, we combine comprehensive mass spectrometric glycan sequencing and molecular dynamics simulations to elucidate the substitution pattern in softwood xylans and to investigate the effect of distinct intramolecular motifs on xylan conformation and on the interaction with cellulose surfaces in Norway spruce (Picea abies). We confirm the presence of motifs with evenly spaced glycosyl decorations on the xylan backbone, together with minor motifs with consecutive glucuronation. These domains are differently enriched in xylan fractions extracted by alkali and subcritical water, which indicates their preferential positioning in the secondary plant cell wall ultrastructure. The flexibility of the 3-fold screw conformation of xylan in solution is enhanced by the presence of arabinofuranosyl decorations. Additionally, molecular dynamic simulations suggest that the glycosyl substitutions in xylan are not only sterically tolerated by the cellulose surfaces but that they increase the affinity for cellulose and favor the stabilization of the 2-fold screw conformation. This effect is more significant for the hydrophobic surface compared with the hydrophilic ones, which demonstrates the importance of nonpolar driving forces on the structural integrity of secondary plant cell walls. These novel molecular insights contribute to an improved understanding of the supramolecular architecture of plant secondary cell walls and have fundamental implications for overcoming lignocellulose recalcitrance and for the design of advanced wood-based materials.

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Section: Discussioncontrasting

confidence: 74%

Regular Motifs in Xylan Modulate Molecular Flexibility and Interactions with Cellulose Surfaces

et al. 2017

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“…In this scheme, hsGAX binds to lsGAX, thereby indirectly spanning multiple cellulose microfibrils; we propose that EXPB1 may bind and disrupt the hsGAX-lsGAX junctions. Consistent with this scenario, lsGAX is known to bind to cellulose in vitro (Carpita, 1983;Köhnke et al, 2011;Selig et al, 2015), whereas hsGAX does not. Strong GAX-cellulose cross peaks are seen in 2D SSNMR spectra of Brachypodium, a model grass species, indicating subnanometer contacts between the two polysaccharides , which is also supported by the presence of a cellulose form that is restructured by interactions with GAX in Brachypodium and XyG in Arabidopsis CWs .…”

Section: A Model Of Expb1-mediated Cw Looseningmentioning

confidence: 63%

The Target of β-Expansin EXPB1 in Maize Cell Walls from Binding and Solid-State NMR Studies

et al. 2016

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The wall-loosening actions of b-expansins are known primarily from studies of EXPB1 extracted from maize (Zea mays) pollen. EXPB1 selectively loosens cell walls (CWs) of grasses, but its specific binding target is unknown. We characterized EXPB1 binding to sequentially extracted maize CWs, finding that the protein primarily binds glucuronoarabinoxylan (GAX), the major matrix polysaccharide in grass CWs. This binding is strongly reduced by salts, indicating that it is predominantly electrostatic in nature. For direct molecular evidence of EXPB1 binding, we conducted solid-state nuclear magnetic resonance experiments using paramagnetic relaxation enhancement (PRE), which is sensitive to distances between unpaired electrons and nuclei. By mixing 13 C-enriched maize CWs with EXPB1 functionalized with a Mn 2+ tag, we measured Mn 2+ -induced PRE. Strong 1 H and 13 C PREs were observed for the carboxyls of GAX, followed by more moderate PREs for carboxyl groups in homogalacturonan and rhamnogalacturonan-I, indicating that EXPB1 preferentially binds GAX. In contrast, no PRE was observed for cellulose, indicating very weak interaction of EXPB1 with cellulose. Dynamics experiments show that EXPB1 changes GAX mobility in a complex manner: the rigid fraction of GAX became more rigid upon EXPB1 binding while the dynamic fraction became more mobile. Combining these data with previous results, we propose that EXPB1 loosens grass CWs by disrupting noncovalent junctions between highly substituted GAX and GAX of low substitution, which binds cellulose. This study provides molecular evidence of b-expansin's target in grass CWs and demonstrates a new strategy for investigating ligand binding for proteins that are difficult to express heterologously.

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“…This means that the gross features of their potential energy surfaces are very similar (Mazeau and Charlier, 2012). As such, there is a high affinity between the two species, and xylan adsorbs irreversibly onto cellulose surfaces (Kabel et al, 2007;Köhnke et al, 2011). Therefore, it is possible that xylan side chains could participate in anchoring mucilage pectin to the seed coat surface through noncovalent interactions with cellulose.…”

Section: Xyl Contents In Outer Soluble Mucilage Show Tight Proportionmentioning

confidence: 99%

“…The association of cellulose, hemicellulose, and pectin polymers provides both rigidity and plasticity thanks to their distinct structural properties and how they interact. The precise nature of these interactions remains an open question, with evidence for noncovalent binding of hemicellulose or rhamnogalacturonan I (RG-I) arabinan and galactan side chains to cellulose (Hayashi et al, 1987;Vincken et al, 1995;Zykwinska et al, 2005;Köhnke et al, 2011). Improving our knowledge of the interactions between cell wall polymers, therefore, is fundamental to our understanding of the regulation of plant growth and for their exploitation in biodegradable materials or biofuel production.…”

mentioning

confidence: 99%

Xylans Provide the Structural Driving Force for Mucilage Adhesion to the Arabidopsis Seed Coat

et al. 2016

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Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells produce large amounts of mucilage that is released upon imbibition. This mucilage is structured into two domains: an outer diffuse layer that can be easily removed by agitation and an inner layer that remains attached to the outer seed coat. Both layers are composed primarily of pectic rhamnogalacturonan I (RG-I), the inner layer also containing rays of cellulose that extend from the top of each columella. Perturbation in cellulosic ray formation has systematically been associated with a redistribution of pectic mucilage from the inner to the outer layer, in agreement with cellulose-pectin interactions, the nature of which remained unknown. Here, by analyzing the outer layer composition of a series of mutant alleles, a tight proportionality of xylose, galacturonic acid, and rhamnose was evidenced, except for mucilage modified5-1 (mum5-1; a mutant showing a redistribution of mucilage pectin from the inner adherent layer to the outer soluble one), for which the rhamnose-xylose ratio was increased drastically. Biochemical and in vitro binding assay data demonstrated that xylan chains are attached to RG-I chains and mediate the adsorption of mucilage to cellulose microfibrils. mum5-1 mucilage exhibited very weak adsorption to cellulose. MUM5 was identified as a putative xylosyl transferase recently characterized as MUCI21. Together, these findings suggest that the binding affinity of xylose ramifications on RG-I to a cellulose scaffold is one of the factors involved in the formation of the adherent mucilage layer.

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Adsorption of Arabinoxylan on Cellulosic Surfaces: Influence of Degree of Substitution and Substitution Pattern on Adsorption Characteristics

Cited by 134 publications

References 46 publications

Regular Motifs in Xylan Modulate Molecular Flexibility and Interactions with Cellulose Surfaces

Regular Motifs in Xylan Modulate Molecular Flexibility and Interactions with Cellulose Surfaces

The Target of β-Expansin EXPB1 in Maize Cell Walls from Binding and Solid-State NMR Studies

Xylans Provide the Structural Driving Force for Mucilage Adhesion to the Arabidopsis Seed Coat

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