PolyStyrene磺酸盐与溶菌酶复合物的多尺度静电重组
Multiple Scale Reorganization of Electrostatic Complexes of PolyStyrene Sulfonate and Lysozyme
摘要：
我们报告的SANS调查的潜在这些结构重组的复合物组成的溶菌酶和小PSS链的相反的电荷，如果溶液的物理化学条件改变后，它们的形成。具有高物质含量并且引入的电荷比[-]/[+]接近静电化学计量的溶菌酶和PSS的溶液的混合物导致宏观上稳定的悬浮液。它们在局部尺度上由半径约为100 μ m的致密球状原生复合体组成;在更高尺度上，它们以2.1维分形组织。我们首先表明，配合物的溶液的稀释，所有其他的物理化学参数保持不变，诱导宏观不稳定的解决方案，但不修改的结构的配合物在亚微米尺度。这表明复合物的胶体稳定性可以通过高浓度下网络中分形聚集体的互锁来解释：稀释不会破坏局部聚集体结构，但会破坏网络。我们表明，第二，盐的加入不会改变几乎冻结的内部结构的核心的初级复合物，虽然它确实鼓励增长的复合物，这些合并成更大的复合物盐部分屏蔽了两个初级复合物之间的静电排斥。这些较大的初级复合物保持聚集，分形维数为2.1。第三，我们发现，在形成[-]/[+]intro接近1的初级复合物后，添加PSS链直到[-]/[+]intro ~ 20，仅轻微改变初级复合物的内部结构。此外，与在一步混合程序中实现的合成（其中蛋白质在一系列[-]/[+]引入中解折叠）相反，蛋白质的天然构象保留在冷冻核心内。
英文摘要：
We report on a SANS investigation into the potential for these structural reorganization of complexes composed of lysozyme and small PSS chains of opposite charge if the physicochemical conditions of the solutions are changed after their formation. Mixtures of solutions of lysozyme and PSS with high matter content and with an introduced charge ratio [-]/[+]intro close to the electrostatic stoichiometry, lead to suspensions that are macroscopically stable. They are composed at local scale of dense globular primary complexes of radius ~ 100 Å; at a higher scale they are organized fractally with a dimension 2.1. We first show that the dilution of the solution of complexes, all other physicochemical parameters remaining constant, induces a macroscopic destabilization of the solutions but does not modify the structure of the complexes at submicronic scales. This suggests that the colloidal stability of the complexes can be explained by the interlocking of the fractal aggregates in a network at high concentration: dilution does not break the local aggregate structure but it does destroy the network. We show, secondly, that the addition of salt does not change the almost frozen inner structure of the cores of the primary complexes, although it does encourage growth of the complexes; these coalesce into larger complexes as salt has partially screened the electrostatic repulsions between two primary complexes. These larger primary complexes remain aggregated with a fractal dimension of 2.1. Thirdly, we show that the addition of PSS chains up to [-]/[+]intro ~ 20, after the formation of the primary complex with a [-]/[+]intro close to 1, only slightly changes the inner structure of the primary complexes. Moreover, in contrast to the synthesis achieved in the one-step mixing procedure where the proteins are unfolded for a range of [-]/[+]intro, the native conformation of the proteins is preserved inside the frozen core.
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