新型羧酸卟啉锌（Ⅱ）配合物与人血清蛋白的作用

摘要

卟啉是一种潜在有效的光动力治疗癌症的光敏剂,部分已用于临床实验中。人血清蛋白(HSA)是药物的运输载体,详细研究两者的相互作用对于阐述卟啉类药物的药代动力学行为具有重要的意义。合成了一种新型水溶性羧酸锌(Ⅱ)卟啉配合物(2-Zn),并通过紫外可见吸收光谱、荧光光谱、圆二色(CD)光谱和分子对接模拟研究了其与人血清蛋白(HSA)的相互作用。结果表明：2-Zn以静态猝灭的方式猝灭了 HSA的内源荧光,通过计算得到其与 HSA 在298和310 K 下相互作用的猝灭常数分别为1.96×104和1.37×104 L·mol-1、结合常数分别为1.93×104和1.50×104 L·mol-1、结合位点数均为1,两者间的结合作用力以静电作用为主,同时也存在氢键和疏水作用。位点竞争实验表明2-Zn主要结合在位点Ⅱ处；根据 For-ster非辐射能量理论得到两者的结合距离和能量转移效率分别为4.01 nm和0.163。紫外吸收光谱,同步荧光和CD光谱显示2-Zn与 HSA的相互作用影响了 HSA 的构象,表现为α-螺旋的含量降低；分子对接模拟结果表明2-Zn通过疏水、静电和氢键作用嵌入 HSA分子的亚结构域IIIA(site Ⅱ)的疏水腔内,与位点竞争实验和热力学判据所得的结果相一致。%Porphyrin is a kind of photosensitizer for photodynamic therapy of cancer.Many porphyrin derivatives have been used in clinical treatment.Human Serum Albumin (HSA)is the carrier of drug transportation.Therefore,investigation on the inter-action of porphyrin with HSA is very important to understand the pharmacokinetic of the porphyrin.In this paper,a new water-soluble carboxyl porphyrins,meso-tetrakis(carboxyl)zinc(Ⅱ)porphyrin (2-Zn),was synthesized and characterized.Its interac-tion with human serum albumin (HSA)was investigated by UV-Vis absorption spectra,fluorescence spectra,circular dichroism (CD)spectra and molecular modeling.The results indicated that the fluorescence quenching of HSA by 2-Zn was a static process with the quenching constants are 1.96×104 L·mol-1 (298 K)and 1.37×104 L·mol-1 (310 K)and the binding constants were calculated to be 1.93×104 L·mol-1(298 K)and 1.50×104 L·mol-1 (310 K).According to the Van’t Hoff equation,the thermodynamic parameters were characterized by negative enthalpy (ΔH=-16.132 kJ·mol-1 )and positive entropy (ΔS=27.905 J·mol-1 ·K-1 ),which indicated that 2-Zn binds with HSA mainly via electrostatic interaction along with the hydrogen bonding and hydrophobic interaction.Site marker competitive binding experiment confirmed that 2-Zn mainly binds at site Ⅱ. The distance between HSA and the receptor (2-Zn)and the efficiency energy transfer were obtained to be 4.01 nm and 0.163 re-spectively,based on the Forster theory on resonance energy transfer.Synchronous fluorescence,absorption and CD spectroscopy showed that the interaction of HSA with 2-Zn induced a conformational change of protein,and the amount ofα-helical structures were decrease.Furthermore,the binding details between 2-Zn and HSA were further studied with the molecular docking,which was in good agreement with the site marker competitive binding experiments and thermodynamic parameters.