聚乙烯亚胺对人血清白蛋白的构象和结合能力的影响

为了解基因载体材料聚乙烯亚胺（PEI）细胞毒性的分子作用机理，本文应用吸收光谱、荧光光谱、圆二色谱、动态光散射和zeta-电位测定分析平均相对分子量为1.8和25 kDa的PEI（记为PEI1.8k和PEI25k）对人血清白蛋白（HSA）构象的影响，同时以8-苯氨基萘-1-磺酸镁（ANS）和槲皮素为模型化合物，了解PEI对HSA结合能力的影响及机理。结果发现，PEI与HSA结合形成静态复合物，导致HSA流体动力学直径变小和分子内环境疏水性增强。PEI1.8k和低浓度的PEI25k引起HSA的a-螺旋结构增加，但是高浓度的PEI25k对HSA二级结构具有稳定作用。PEI对HSA结合能力的影响主要归因于PEI的竞争结合和PEI与HSA结合引起的蛋白质构象变化。PEI的竞争结合降低了HSA对ANS和槲皮素的结合效率，但是蛋白质的构象变化增强了HSA与ANS和槲皮素的结合能力。PEI与HSA的相互作用具有明显的分子尺寸效应，增加PEI的相对分子量可以增强对HSA构象和结合能力的影响。

Effects of Polyethyleneimine on the Conformation and Binding Capability of Human Serum Albumin

For a better understanding of the cytotoxicity of polyethyleneimine (PEI), which has long been considered as the "golden standard" for polymeric gene delivery carriers, on the molecular basis, UV-Vis absorption, fluorescence, circular dichroism, dynamic light scattering and zeta-potential measurements were conducted to reveal the interaction between the PEI of average molecular weight 1.8 and 25 kDa (denoted as PEI1.8k and PEI25k, respectively) and human serum albumin (HSA). The effects of interactions on the conformation of HSA and its binding capability to the model compounds, 8-anilino-1-naphthalenesulfonic acid (ANS) and quercetin, were also evaluated. PEI was found to bind to HSA and induce an alteration in the secondary and tertiary structures of the protein and its binding capability toward small compounds. The complex formation with PEI resulted in a more compact and hydrophobic conformation of HSA, accompanying an increase in α-helix content in the case of PEI1.8k and PEI25k at low concentrations. The binding efficacy of ANS and quercetin to HSA was reduced by competitive binding with PEI, however increased by the conformational change of the protein. Higher-molecular-weight PEI was found to interact with HSA more favorably. It was also more efficient in perturbing the conformation and the binding capability of the protein.