Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269, USA.
Pharm Res. 2011 Aug;28(8):1973-83. doi: 10.1007/s11095-011-0424-7. Epub 2011 Apr 14.
To understand the apparent inconsistency between the dilute and high concentration viscosity behavior of bovine serum albumin (BSA).
Zeta potential and molecular charge on BSA were determined from Electrophoretic mobility measurements. Second virial coefficient (B(22)) and interaction parameter (k(D)) obtained from static and dynamic light scattering, respectively, quantified intermolecular interactions. Rheology studies characterized viscoelasticity at high concentration. The dipole moment was calculated using Takashima's approximation for proton fluctuations over charged residues.
The effective isoelectric point of BSA was pH 4.95. In dilute solutions (≤ 40 mg/ml), the viscosity was minimal at the pI; at high concentrations, pH 5.0 solutions were most viscous. B(22) and k(D) showed intermolecular attractions at pH 5.0; repulsions dominated at other pHs. The attractive interactions led to a high storage modulus (G') at pH 5.0.
In dilute solutions, the electroviscous effect due to net charge governs the viscosity behavior; at high concentrations, the solution viscosity cannot be justified based on a single parameter. The net interplay of all intermolecular forces dictates viscosity behavior, wherein intermolecular attraction leads to a higher solution viscosity.
理解牛血清白蛋白（BSA）在稀溶液和高浓度下黏度行为的明显不一致。
通过电泳迁移率测量确定 BSA 的动电电势和分子电荷。通过静态和动态光散射分别获得的第二维里系数（B(22)）和相互作用参数（k(D)）量化了分子间相互作用。流变学研究在高浓度下表征了粘弹性。利用 Takashima 对荷电残基质子波动的近似值计算偶极矩。
BSA 的有效等电点为 pH 4.95。在稀溶液（≤40mg/ml）中，黏度在等电点时最小；在高浓度下，pH 5.0 的溶液最粘稠。在 pH 5.0 时，B(22)和 k(D)显示出分子间吸引力；在其他 pH 值下，排斥力占主导地位。吸引力导致 pH 5.0 时储能模量（G'）较高。
在稀溶液中，净电荷引起的电动效应控制着黏度行为；在高浓度下，不能仅用单一参数来解释溶液黏度。所有分子间力的净相互作用决定了黏度行为，其中分子间吸引力导致溶液黏度更高。
