Jacoboni I, Valdrè U, Mori G, Quaglino D, Pasquali-Ronchetti I
INFM and Department of Physics, University of Bologna, Bologna, Italy.
J Struct Biol. 1999 Jun 1;126(1):52-8. doi: 10.1006/jsbi.1999.4090.
Hyaluronic acid (HA) of different molecular weights has been examined by atomic force microscopy (AFM) in air. This technique allows 3-D surface images of soft samples without any pretreatment, such as shadowing or staining. In the present study we examined the supermolecular organization of HA chains when deposited on mica and graphite, to better understand the interchain and intrachain interactions of HA molecules in solution. The concentration of the solution deposited varied from 0.001 to 1 mg/ml. On both substrates, and independent of the concentration, high-molecular-mass HA formed networks in which molecules ran parallel for hundreds of nanometers, giving rise to flat sheets and tubular structures that separate and rejoin into similar neighboring aggregates. Accurate measurements of the thickness of the thinnest sheets were consistent with a monolayer of HA molecules, 0.3 nm thick, strongly indicating lateral aggregation forces between chains as well as rather strong hydrophilic interactions between mica and HA. The results agree with an existing model of HA tertiary structure in solution in which the network is stabilized by both hydrophilic and hydrophobic interactions. Our images support this model and indicate that hydrophobic interactions between chains may exert a pivotal role in aqueous solution.
不同分子量的透明质酸（HA）已在空气中通过原子力显微镜（AFM）进行了检测。该技术无需任何诸如投影或染色等预处理，就能获取软质样品的三维表面图像。在本研究中，我们检测了沉积在云母和石墨上的HA链的超分子结构，以便更好地理解溶液中HA分子的链间和链内相互作用。所沉积溶液的浓度在0.001至1毫克/毫升之间变化。在这两种基质上，且与浓度无关，高分子量的HA形成了网络结构，其中分子平行排列数百纳米，形成了扁平片层和管状结构，这些结构分离并重新连接成类似的相邻聚集体。对最薄片层厚度的精确测量结果与厚度为0.3纳米的单层HA分子一致，这有力地表明了链间的侧向聚集力以及云母与HA之间相当强的亲水相互作用。这些结果与溶液中HA三级结构的现有模型相符，在该模型中，网络通过亲水和疏水相互作用得以稳定。我们的图像支持这一模型，并表明链间的疏水相互作用在水溶液中可能起着关键作用。
