Dammak Abir, Quémener Bernard, Bonnin Estelle, Alvarado Camille, Bouchet Brigitte, Villares Ana, Moreau Céline, Cathala Bernard
INRA, UR1268 Biopolymères Interactions Assemblages, 44316 Nantes, France.
Biomacromolecules. 2015 Feb 9;16(2):589-96. doi: 10.1021/bm5016317. Epub 2015 Jan 21.
Xyloglucan (XG) is believed to act as a cementing material that contributes to the cross-linking and mechanical properties of the cellulose framework in plant cell walls. XG can adsorb to the cellulose nanocrystal (CNC) surface in vitro in order to simulate this in vivo relationship. The target of our work was to investigate the sorption behavior of tamarind seed XG on CNC extracted from cotton linters at different XG/CNC concentration ratios, that is, different adsorption regimes regarding the XG-CNC complex organization and the enzymatic susceptibility of XG. First, we determined the adsorption isotherm. Second, XG-CNC complexes were enzymatically hydrolyzed using a xyloglucan-specific endoglucanase in order to quantify the different XG fractions involved in binding to CNC and to determine adsorption regimes, that is, presence of loops, tails, and trains. Finally, the architecture of the XG-CNC complex was investigated by transmission electron microscopy imaging of negatively stained XG-CNC suspensions and XG immunolabeled suspensions at different XG/CNC concentration ratios, both before and after xyloglucanase hydrolysis process. This study revealed that an increasing XG/CNC concentration ratio led to a change in the XG binding organization to CNC. At low XG/CNC concentration ratios, almost all XG chains were bound as trains to the CNC surface. In contrast, at increasing XG/CNC concentration ratios, the proportion of loops and tails increases. The organization change induces CNC aggregation to form a cellulose/XG network at low XG/CNC regimes, whereas CNC remains in the form of individual particles at higher XG/CNC regimes. Results are discussed both regarding the biological role of XG in plant cell walls and in the perspective of designing new biobased materials.
木葡聚糖（XG）被认为起着粘结材料的作用，有助于植物细胞壁中纤维素框架的交联和机械性能。XG可以在体外吸附到纤维素纳米晶体（CNC）表面，以模拟这种体内关系。我们工作的目标是研究罗望子种子XG在不同XG/CNC浓度比下对从棉短绒中提取的CNC的吸附行为，即关于XG-CNC复合物组织和XG酶敏感性的不同吸附状态。首先，我们测定了吸附等温线。其次，使用木葡聚糖特异性内切葡聚糖酶对XG-CNC复合物进行酶水解，以量化参与与CNC结合的不同XG组分，并确定吸附状态，即环、尾和链的存在情况。最后，通过对不同XG/CNC浓度比的经负染色的XG-CNC悬浮液和XG免疫标记悬浮液在木葡聚糖酶水解过程前后进行透射电子显微镜成像，研究了XG-CNC复合物的结构。这项研究表明，XG/CNC浓度比的增加导致XG与CNC结合组织的变化。在低XG/CNC浓度比下，几乎所有XG链都以链的形式结合到CNC表面。相反，随着XG/CNC浓度比的增加，环和尾的比例增加。组织变化在低XG/CNC状态下诱导CNC聚集形成纤维素/XG网络，而在高XG/CNC状态下CNC保持单个颗粒的形式。从XG在植物细胞壁中的生物学作用以及设计新型生物基材料的角度对结果进行了讨论。
