Cellulose chirality

基于纤维素在植物细胞壁中无处不在的结构作用，它作为一种丰富的、可再生的、碳中和的无毒材料的价值，有助于增强木材、纸张、纺织品和纳米复合材料的强度，纤维素的研究已经复兴。我们计划关注纤维素的一个被忽视的性质，即它的手性。手性在几个长度尺度上表示。当然，单个葡萄糖单元包含手性碳中心，但在更长的尺度上，这种手性也影响纤维素的晶体结构，以及植物细胞壁、纸浆纤维、纸张和木材的上层结构。复兴的一个方面是世界范围内对各种形式的纳米纤维素的兴趣（我们的研究在今年获得了很多认可）。但仍有几个未开发的研究领域，在更大的长度尺度，我们希望在本提案中解决。

There has been a renaissance in cellulose research, based on its ubiquitous structural role in the plant cell wall, its value as an abundant, renewable, carbon-neutral and non-toxic material that contributes to the strength of wood, paper, textiles and nanocomposites. We plan to focus on one neglected cellulose property, namely its chirality. The chirality is expressed over several length scales. Of course, the individual glucose units contain chiral carbon centres, but at longer length scales, this chirality also influences the crystalline structure of cellulose, and the superstructure of plant cell walls, pulp fibres, paper and wood. One aspect of the renaissance has been the world-wide interest in various forms of nanocellulose (a field where our research has garnered a lot of recognition this year). But there remain several untapped areas of research at larger length scales that we would like to address in this proposal. Over the years, we have observed, for the first time, the chiral structure and response of several cellulosic materials. We plan to focus on two particular observations. First, we found that ordered colloidal suspensions of cellulose nanocrystals form a left-handed chiral nematic structure, implying that there is some chiral interaction between the rod-like nanocrystals. We and others have speculated about the nature of this interaction, but experimental evidence is lacking. We hope to apply AFM force measurements to address this problem directly. Choice of cellulose samples and instrument geometries will be the key variables. Second, we’ve isolated for the first time a right-handed coiled cellulose-based structure from the petioles (leaf-stems) of many plants. Whether the handedness is a function of the chiral interactions of cellulose microfibrils, or is a result of biosynthetic pathways (or both) is unclear. In any case, the observed structures would seem to play a role in water transport through the plant vascular system. While the vascular system of plants has been extensively investigated, many questions on this key natural process remain. We would like to examine the significance of our preliminary observations on petiole structure and function from a physico-chemical viewpoint.