Lopez-Sanchez Patricia, Schuster Erich, Wang Dongjie, Gidley Michael J, Strom Anna
ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, 4072, Australia.
Soft Matter. 2015 May 28;11(20):4002-10. doi: 10.1039/c5sm00103j. Epub 2015 Apr 22.
Cellulose hydrogels are extensively applied in many biotechnological fields and are also used as models for plant cell walls. We synthesised model cellulosic hydrogels containing hemicelluloses, as a biomimetic of plant cell walls, in order to study the role of hemicelluloses on their mass transport properties. Microbial cellulose is able to self-assemble into composites when hemicelluloses, such as xyloglucan and arabinoxylan, are present in the incubation media, leading to hydrogels with different nano and microstructures. We investigated the diffusivities of a series of fluorescently labelled dextrans, of different molecular weight, and proteins, including a plant pectin methyl esterase (PME), using fluorescence recovery after photobleaching (FRAP). The presence of xyloglucan, known to be able to crosslink cellulose fibres, confirmed by scanning electron microscopy (SEM) and (13)C NMR, reduced mobility of macromolecules of molecular weight higher than 10 kDa, reflected in lower diffusion coefficients. Furthermore PME diffusion was reduced in composites containing xyloglucan, despite the lack of a particular binding motif in PME for this polysaccharide, suggesting possible non-specific interactions between PME and this hemicellulose. In contrast, hydrogels containing arabinoxylan coating cellulose fibres showed enhanced diffusivity of the molecules studied. The different diffusivities were related to the architectural features found in the composites as a function of polysaccharide composition. Our results show the effect of model hemicelluloses in the mass transport properties of cellulose networks in highly hydrated environments relevant to understanding the role of hemicelluloses in the permeability of plant cell walls and aiding design of plant based materials with tailored properties.
纤维素水凝胶在许多生物技术领域有着广泛应用，还被用作植物细胞壁的模型。我们合成了含有半纤维素的模型纤维素水凝胶，作为植物细胞壁的仿生材料，以研究半纤维素对其传质特性的作用。当木葡聚糖和阿拉伯木聚糖等半纤维素存在于培养介质中时，微生物纤维素能够自组装成复合材料，从而形成具有不同纳米和微观结构的水凝胶。我们使用光漂白后荧光恢复（FRAP）技术，研究了一系列不同分子量的荧光标记葡聚糖以及包括植物果胶甲酯酶（PME）在内的蛋白质的扩散系数。扫描电子显微镜（SEM）和（13）C NMR证实，已知能够交联纤维素纤维的木葡聚糖的存在，降低了分子量高于10 kDa的大分子的迁移率，这在较低的扩散系数中得到体现。此外，尽管PME中缺乏与这种多糖的特定结合基序，但在含有木葡聚糖的复合材料中PME的扩散仍有所降低，这表明PME与这种半纤维素之间可能存在非特异性相互作用。相比之下，含有阿拉伯木聚糖包覆纤维素纤维的水凝胶显示出所研究分子的扩散率增强。不同的扩散率与复合材料中根据多糖组成所发现的结构特征有关。我们的结果表明，在与理解半纤维素在植物细胞壁通透性中的作用以及辅助设计具有定制特性的植物基材料相关的高度水合环境中，模型半纤维素对纤维素网络的传质特性有影响。
