Reis D, Vian B, Chanzy H, Roland J C
Laboratoire des Biomembranes et Surfaces Cellulaires Végétales, ENS, Paris, France.
Biol Cell. 1991;73(2-3):173-8. doi: 10.1016/0248-4900(91)90100-2.
In numerous plant cell walls, the cellulose microfibrils are arranged in a helicoidal pattern which has been considered as an analog to a cholesteric order. Here, we report on the spontaneous helicoidal organization which occurs in acellular conditions from aqueous suspensions of cellulose. The cellulosic mucilage of mature seeds of quince (Cydonia oblonga L) was studied both in situ (pre-release mucilage) and after water extraction and in in vitro re-assembly (prolonged high speed ultracentrifugation, further progressive dehydration and embedding in LR White methacrylate or hydrosoluble melamine resin). The cellulosic component was characterized by the use of cellobiohydrolase (CBH1) bound to colloidal gold, and the glucuronic acid residues of the xylan matrix were characterized by the use of cationised gold. Inside the seeds, the pre-release mucilage is mostly helicoidal, with the occurrence of more or less ordered domains, which indicate a fluid organization relevant to an actual liquid crystal state. Cytochemical tests revealed the tight association between cellulose and glucuronoxylans, the latter constituting a charged coat around each microfibril. Following the hydration of the seed, a cellulosic suspension was extracted in which microfibrils were totally dispersed. The progressive dehydration of the suspension gave rise to concentrated viscous drops. Ultrastructural observations revealed the occurrence of multidomain organization, from non-ordered to cholesteric-like regions, revealing that the mucilage is at the same time crystalline and liquid. This constitutes the first demonstration that liquid crystal type assemblies can arise from crystalline and biological cellulose in aqueous suspension. It strengthens the hypothesis that a transient liquid crystal state must occur during the cellulose ordering. The possible morphogenetic role of the glucuronoxylans in the cholesteric organization of the cellulose is discussed.
在许多植物细胞壁中，纤维素微纤丝呈螺旋状排列，这种排列被认为类似于胆甾相序。在此，我们报道了纤维素水悬浮液在无细胞条件下发生的自发螺旋状组织。对榅桲（Cydonia oblonga L）成熟种子的纤维素黏液进行了原位研究（释放前的黏液），以及水提取后和体外重新组装（长时间高速超速离心、进一步逐步脱水并包埋在LR White甲基丙烯酸酯或水溶性三聚氰胺树脂中）的研究。通过使用与胶体金结合的纤维二糖水解酶（CBH1）对纤维素成分进行表征，通过使用阳离子化金对木聚糖基质的葡萄糖醛酸残基进行表征。在种子内部，释放前的黏液大多呈螺旋状，存在或多或少有序的区域，这表明其具有与实际液晶态相关的流体组织。细胞化学测试揭示了纤维素与葡糖醛酸木聚糖之间的紧密关联，后者在每个微纤丝周围构成一层带电涂层。种子水化后，提取出一种纤维素悬浮液，其中微纤丝完全分散。悬浮液的逐步脱水产生了浓缩的粘性液滴。超微结构观察揭示了从无序到类胆甾相区域的多畴组织的出现，表明黏液同时具有结晶性和流动性。这首次证明了液晶型组装可以从水性悬浮液中的结晶性生物纤维素产生。它强化了纤维素有序化过程中必然会出现短暂液晶态的假设。还讨论了葡糖醛酸木聚糖在纤维素胆甾相组织中可能的形态发生作用。
