Cellulose chirality

纤维素研究已经复兴，基于其在植物细胞壁中无处不在的结构作用，其作为丰富的，可再生的，碳中性和无毒材料的价值，有助于木材，纸张，纺织品和纳米复合材料的强度。我们计划集中在一个被忽视的纤维素性质，即其手性。手性表示在几个长度尺度。当然，单个葡萄糖单元含有手性碳中心，但在更长的长度尺度上，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、纸张和木材的超结构。文艺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（今年我们的研究获得了很多认可）。但是，我们希望在本提案中解决一些尚未开发的更大尺度的研究领域。多年来，我们首次观察到了几种纤维素材料的手性结构和响应。我们计划着重于两个具体的观察。首先，我们发现纤维素纳米晶体的有序胶体悬浮液形成左手手性的棒状结构，这意味着棒状纳米晶体之间存在着手性相互作用。我们和其他人已经推测了这种相互作用的性质，但缺乏实验证据。我们希望应用AFM力测量直接解决这个问题。纤维素样品和仪器几何形状的选择将是关键变量。其次，我们首次从许多植物的叶柄（叶柄）中分离出了一种右旋卷曲的纤维素结构。手性是否是纤维素微纤维的手性相互作用的函数，或者是生物合成途径（或两者）的结果尚不清楚。在任何情况下，观察到的结构似乎在通过植物维管系统的水分运输中发挥作用。虽然植物的维管系统已被广泛研究，但这一关键的自然过程仍存在许多问题。我们想从物理化学的角度来研究我们对叶柄结构和功能的初步观察的意义。

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.