N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Kosygin Str. 4., 119334 Moscow, Russia.
Department of Physics and Astronomy, Laboratory of Solid State Physics and Magnetism, KU Leuven , Celestijnenlaan 200D, Box 2414, B-3001 Leuven, Belgium.
Langmuir. 2017 Nov 28;33(47):13530-13542. doi: 10.1021/acs.langmuir.7b01477. Epub 2017 Nov 13.
It is known that the formation of electrostatic polyelectrolyte complexes can induce conformational changes in the interacting macromolecules. However, the opposite effect, namely, that of the helix-coil transition of one of the interacting polyelectrolytes on its associative phase separation with another polyelectrolyte and the possible phase transitions in such systems, has not been determined. Atomic force and confocal laser scanning microscopy, phase analysis, dynamic and electrophoretic light scattering, turbidimetry, absorption, and fluorescence measurements as well as differential scanning calorimetry and rheology were used to study the effect of the helix-coil transition in bovine skin gelatin (Gel) on its associative phase separation with hen egg white lysozyme (Lys) at different temperatures (18-40 °C) and various Lys/Gel weight ratios (0.01-100) at low ionic strength (0.01) and pH 7.0. The effects of the main variables on the phase state, the phase diagram, and the main complexation and binding parameters as well as the temperature and enthalpy of the helix-coil transition of Gel within the complexes were investigated. Associative phase separation is observed only for the system with Gel in the helix state. Effective charge and structure and the solution and rheological behavior of the formed complexes proved to be dependent on the [An]/[Cat] charge ratio. The localization of Lys within the complex particles has irregular character without the formation of a single center of binding. The binding of Lys with Gel does not lead to the disruption of its tertiary structure or to an appreciable change in the thermodynamic parameters of the thermal transitions of Lys. Gel in the coil state interacts only weakly with Lys, forming water-soluble complex associates. It is suggested that the Voorn-Overbeek model could potentially describe the stronger binding and phase separation in the case of Gel in the helix state.
已知静电聚电解质复合物的形成会引起相互作用的大分子构象发生变化。然而，与之相反的效果，即相互作用的聚电解质之一的螺旋-卷曲转变对其与另一种聚电解质的缔合相分离以及此类系统中可能发生的相转变的影响，尚未确定。原子力和共焦激光扫描显微镜、相分析、动态和电泳光散射、浊度法、吸收和荧光测量以及差示扫描量热法和流变学被用于研究牛皮明胶（Gel）的螺旋-卷曲转变对其与鸡卵清溶菌酶（Lys）在不同温度（18-40°C）和各种 Lys/Gel 重量比（0.01-100）下在低离子强度（0.01）和 pH 7.0 下的缔合相分离的影响。研究了主要变量对相态、相图以及主要的络合和结合参数以及 Gel 在复合物中的螺旋-卷曲转变的温度和焓的影响。仅在 Gel 处于螺旋状态的系统中观察到缔合相分离。有效电荷和结构以及形成的复合物的溶液和流变行为被证明取决于[An]/[Cat]电荷比。Lys 在复合物颗粒内的定位具有不规则的特征，没有形成单一的结合中心。Lys 与 Gel 的结合不会导致其三级结构的破坏，也不会导致 Lys 热转变的热力学参数发生明显变化。处于卷曲状态的 Gel 仅与 Lys 弱相互作用，形成水溶性复合配合物。有人提出，Voorn-Overbeek 模型可能潜在地描述了 Gel 处于螺旋状态时更强的结合和相分离。
