INRA-BIA, BP 71627, 44316 Nantes Cedex 3, France.
J Colloid Interface Sci. 2010 May 1;345(1):54-63. doi: 10.1016/j.jcis.2010.01.036. Epub 2010 Jan 18.
We investigated the structure of heat-induced assemblies of whey globular proteins using small angle neutron scattering (SANS), static and dynamic light scattering (SLS and DLS), and cryogenic transmission electron microscopy (Cryo-TEM). Whey protein molecules self-assemble in fractal aggregates with a structure density depending on the electrostatic interactions. We determined the static and dynamic properties of interfacial layer formed by the protein assemblies, upon adsorption and spreading at the air-water interface using surface film balance and interfacial dilatational rheology. Upon spreading, all whey protein systems show a power-law scaling behavior of the surface pressure versus concentration in the semi-dilute surface concentration regime, with an exponent ranging from 5.5 to 9 depending on the electrostatic interactions and the aggregation state. The dilatational modulus derived from surface pressure isotherms shows a main peak at 6-8 mN/m, generally considered to be the onset of a conformational change in the monolayer, and a second peak or a shoulder at 15 mN/m. Long-time adsorption kinetics give similar results for both the native whey proteins and the corresponding self-similar assemblies, with a systematic effect of the ionic strength.
我们使用小角中子散射（SANS）、静态和动态光散射（SLS 和 DLS）以及低温透射电子显微镜（Cryo-TEM）研究了乳清球蛋白在受热时形成的聚集体结构。乳清蛋白分子通过静电相互作用自组装成具有结构密度的分形聚集体。我们使用表面膜天平（surface film balance）和界面膨胀流变学（interfacial dilatational rheology），确定了在空气-水界面上吸附和铺展时由蛋白质组装体形成的界面层的静态和动态特性。在铺展过程中，所有乳清蛋白体系在半稀表面浓度范围内，表面压力与浓度的关系都表现出幂律行为，其指数范围从 5.5 到 9，这取决于静电相互作用和聚集状态。从表面压力等温线上得出的膨胀模量在 6-8 mN/m 处有一个主要峰值，通常被认为是单层构象变化的开始，在 15 mN/m 处有第二个峰值或肩峰。长时间的吸附动力学对天然乳清蛋白和相应的自相似组装体给出了相似的结果，离子强度有系统的影响。
