Department of Biology, Pennsylvania State University , University Park, Pennsylvania 16803, United States.
Biomacromolecules. 2014 May 12;15(5):1727-36. doi: 10.1021/bm5001247. Epub 2014 Apr 16.
(1,3)(1,4)-β-D-Glucan (mixed-linkage glucan or MLG), a characteristic hemicellulose in primary cell walls of grasses, was investigated to determine both its role in cell walls and its interaction with cellulose and other cell wall polysaccharides in vitro. Binding isotherms showed that MLG adsorption onto microcrystalline cellulose is slow, irreversible, and temperature-dependent. Measurements using quartz crystal microbalance with dissipation monitoring showed that MLG adsorbed irreversibly onto amorphous regenerated cellulose, forming a thick hydrogel. Oligosaccharide profiling using endo-(1,3)(1,4)-β-glucanase indicated that there was no difference in the frequency and distribution of (1,3) and (1,4) links in bound and unbound MLG. The binding of MLG to cellulose was reduced if the cellulose samples were first treated with certain cell wall polysaccharides, such as xyloglucan and glucuronoarabinoxylan. The tethering function of MLG in cell walls was tested by applying endo-(1,3)(1,4)-β-glucanase to wall samples in a constant force extensometer. Cell wall extension was not induced, which indicates that enzyme-accessible MLG does not tether cellulose fibrils into a load-bearing network.
(1,3)(1,4)-β-D-葡聚糖（混合连接葡聚糖或 MLG）是禾本科植物初生细胞壁中的一种特征性半纤维素，本研究旨在探究其在细胞壁中的作用，以及其在体外与纤维素和其他细胞壁多糖的相互作用。结合等温线表明，MLG 吸附到微晶纤维素上的过程缓慢、不可逆且依赖于温度。使用石英晶体微天平结合耗散监测的测量结果表明，MLG 不可逆地吸附到无定形再生纤维素上，形成厚水凝胶。使用内切-(1,3)(1,4)-β-葡聚糖酶进行寡糖分析表明，结合和未结合的 MLG 中(1,3)和(1,4)键的出现频率和分布没有差异。如果先将纤维素样品用某些细胞壁多糖（如木葡聚糖和半乳甘露聚糖）处理，MLG 与纤维素的结合就会减少。通过在恒力拉伸仪中将内切-(1,3)(1,4)-β-葡聚糖酶应用于细胞壁样品来测试 MLG 在细胞壁中的固定功能。细胞壁没有发生延伸，这表明酶可及的 MLG 不会将纤维素纤维固定成具有承载能力的网络。
