Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zurich, Switzerland.
Biophys J. 2013 Jun 18;104(12):2686-94. doi: 10.1016/j.bpj.2013.05.017.
Cells are coated with a glycocalyx-a layer of carbohydrate-containing biomolecules, such as glycoproteins. Although the structure and orientation of the cell-surface glycans are frequently regarded as being random, we have found, using α-1-acid glycoprotein and antitrypsin as model systems for surface glycans, that this is not the case. A glycoprotein monolayer was adsorbed onto hydrophilic and hydrophobic substrates. Surface-force measurements revealed that the orientation of the glycans with respect to the aqueous solution has a profound effect on the structure of vicinal water. The glycan antennae of the surface-adsorbed glycoproteins apparently impose an ordering on the water, resulting in a strong repulsive force over some tens of nanometers with superposed film-thickness transitions ranging from ≈0.7 to 1.8 nm. When the glycan orientation is modified by chemical means, this long-range repulsion disappears. These results may provide an explanation as to why the multiantennary structure is ubiquitous in glycoproteins. Although direct, specific interactions between glycans and other biomolecules are essential for their functionality, these results indicate that glycans' long-range structuring of water may also influence their ability to interact with biomolecules in their vicinity.
细胞表面覆盖着一层糖萼——由含有碳水化合物的生物分子组成的层，例如糖蛋白。尽管细胞表面糖链的结构和取向通常被认为是随机的，但我们已经发现，使用α-1-酸性糖蛋白和抗胰蛋白酶作为表面糖链的模型系统，事实并非如此。糖蛋白单层被吸附到亲水和疏水基底上。表面力测量显示，糖链相对于水溶液的取向对邻近水的结构有深远的影响。表面吸附糖蛋白的糖链触角显然对水施加了一种有序性，导致在数十纳米的范围内产生强烈的排斥力，叠加的膜厚转变范围约为 0.7 至 1.8nm。当糖链取向通过化学手段改变时，这种长程排斥力就会消失。这些结果可能为为什么多天线结构在糖蛋白中普遍存在提供了一个解释。虽然糖链与其他生物分子之间的直接、特异性相互作用对于它们的功能至关重要，但这些结果表明，糖链对水的长程结构也可能影响它们与附近生物分子相互作用的能力。
