Dahesh Mohsen, Banc Amélie, Duri Agnès, Morel Marie-Hélène, Ramos Laurence
Université Montpellier 2 , Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier, France.
J Phys Chem B. 2014 Sep 25;118(38):11065-76. doi: 10.1021/jp5047134. Epub 2014 Sep 11.
The supramolecular organization of wheat gluten proteins is largely unknown due to the intrinsic complexity of this family of proteins and their insolubility in water. We fractionate gluten in a water/ethanol mixture (50/50 v/v) and obtain a protein extract which is depleted in gliadin, the monomeric part of wheat gluten proteins, and enriched in glutenin, the polymeric part of wheat gluten proteins. We investigate the structure of the proteins in the solvent used for extraction over a wide range of concentration, by combining X-ray scattering and multiangle static and dynamic light scattering. Our data show that, in the ethanol/water mixture, the proteins display features characteristic of flexible polymer chains in a good solvent. In the dilute regime, the proteins form very loose structures of characteristic size 150 nm, with an internal dynamics which is quantitatively similar to that of branched polymer coils. In more concentrated regimes, data highlight a hierarchical structure with one characteristic length scale of the order of a few nm, which displays the scaling with concentration expected for a semidilute polymer in good solvent, and a fractal arrangement at a much larger length scale. This structure is strikingly similar to that of polymeric gels, thus providing some factual knowledge to rationalize the viscoelastic properties of wheat gluten proteins and their assemblies.
由于小麦面筋蛋白家族固有的复杂性及其在水中的不溶性，其超分子组织在很大程度上尚不清楚。我们在水/乙醇混合物（50/50 v/v）中对面筋进行分级分离，得到一种蛋白质提取物，该提取物中麦醇溶蛋白（小麦面筋蛋白的单体部分）含量减少，而麦谷蛋白（小麦面筋蛋白的聚合部分）含量增加。我们通过结合X射线散射以及多角度静态和动态光散射，研究了在广泛浓度范围内用于提取的溶剂中蛋白质的结构。我们的数据表明，在乙醇/水混合物中，蛋白质呈现出在良溶剂中柔性聚合物链的特征。在稀溶液状态下，蛋白质形成特征尺寸为150 nm的非常松散的结构，其内部动力学在定量上与支化聚合物线圈的动力学相似。在浓度更高的状态下，数据突出显示了一种分级结构，其具有几个纳米量级的一个特征长度尺度，该尺度显示出在良溶剂中半稀聚合物预期的与浓度的标度关系，以及在大得多的长度尺度上的分形排列。这种结构与聚合物凝胶的结构惊人地相似，从而为解释小麦面筋蛋白及其聚集体的粘弹性特性提供了一些实际依据。
