Maleki Atoosa, Lafitte Géraldine, Kjøniksen Anna-Lena, Thuresson Krister, Nyström Bo
Department of Chemistry, University of Oslo, PO Box 1033, Blindern, N-0315 Oslo, Norway.
Carbohydr Res. 2008 Feb 4;343(2):328-40. doi: 10.1016/j.carres.2007.10.005. Epub 2007 Oct 13.
In this study, dynamic light scattering (DLS), turbidity, and rheo-small angle light scattering (rheo-SALS) methods have been utilized to examine the impact of pH (1 < or = pH < or = 7) on aqueous solutions of noncommercial purified pig gastric mucin. The asymmetric flow field-flow fractionation (AFFFF) measurements established that the mucin sample has a high molecular weight and is polydisperse. DLS measurements on dilute solutions of mucin disclosed large interchain aggregates at pH 2, where the polymer has a low charge density or is uncharged. At lower or higher values of pH, mucin is charged and the tendency of forming interpolymer complexes is affected. In the semidilute concentration regime, pronounced junction zones ('lumps' of polymer) are evolved and a heterogeneous connected network is formed at pH 2, whereas the association structures are disintegrated (smaller 'lumps') at lower or higher pH values due to electrostatic repulsive interactions, and a more homogeneous network is evolved. The DLS and viscosity results at pH 1 indicate the development of a fragmented network, composed of contracted chains that are decorated by some positive charges. The effect of shear flow on the structure of semidilute solutions of mucin was investigated with the aid of rheo-SALS methods. The scattered intensity revealed a strong upturn at low values of the wave vector (q) for mucin solutions at pH 2 and pH 4, which suggests the evolution of large association domains. At these pH values, a flow-induced anisotropy in the 2D SALS patterns in the form of elliptical shapes was observed at high shear rates.
在本研究中，动态光散射（DLS）、浊度和流变小角光散射（rheo-SALS）方法已被用于研究pH值（1≤pH≤7）对非商业纯化猪胃粘蛋白水溶液的影响。不对称流场-流分级（AFFFF）测量结果表明，粘蛋白样品具有高分子量且多分散。对粘蛋白稀溶液的DLS测量显示，在pH 2时聚合物电荷密度低或不带电，存在大的链间聚集体。在较低或较高pH值时，粘蛋白带电，形成聚合物间复合物的趋势受到影响。在半稀浓度范围内，在pH 2时会形成明显的连接区（聚合物“团块”）并形成异质连接网络，而在较低或较高pH值时，由于静电排斥相互作用，缔合结构会解体（较小的“团块”），并形成更均匀的网络。pH 1时的DLS和粘度结果表明形成了由带有一些正电荷的收缩链组成的破碎网络。借助rheo-SALS方法研究了剪切流对粘蛋白半稀溶液结构的影响。对于pH 2和pH 4的粘蛋白溶液，散射强度在低波矢（q）值处显示出强烈的上升，这表明形成了大的缔合域。在这些pH值下，在高剪切速率下观察到二维SALS图案中以椭圆形形式存在的流动诱导各向异性。
