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全氟羧酸(PFCAs)由于具有既亲水又疏水的表面活性剂特性,被广泛应用于工业和生活产品中。全氟十一酸(PFUnA)和全氟十三酸(PFTriA)是长链PFCAs类的典型代表,但近年来它们越来越频繁的在人体中检测到,并且发现表现出内分泌干扰效应、发育毒性和致畸性。本文以光谱学和分子对接为基础,探索PFUnA和PFTriA与人体最丰富的蛋白人血清白蛋白(HSA)的结合模式。结果表明,PFUnA和PFTriA均通过动静态猝灭过程猝灭HSA的内源荧光,与HSA只有一个强亲和位点,且PFUnA与HSA的结合比PFTriA更紧密。根据热力学计算结果,可知PFUnA与HSA结合的焓变、熵变分别为-26.32 kJ·mol~(-1)和21.76 J·mol~(-1)·K~(-1),其结合作用主要依靠静电引力,而PFTriA主要通过范德华力和卤键与HSA结合,是放热熵减过程,其焓变和熵变分别为-39.69 kJ·mol~(-1)和-25.66 J·mol~(-1)·K~(-1)。计算得到的结合距离(r<8 nm)显示从HSA到PFUnA和PFTriA发生了非辐射能量转移。三维荧光光谱和圆二色谱表明,PFUnA和PFTriA与HSA的结合不仅可以改变HSA的构象和微环境,还可以引起α-螺旋稳定性降低。取代实验和分子对接进一步显示PFUnA和PFTriA通过极性键、疏水作用力和卤键等与HSA的亚域ⅡA疏水腔有高亲和性,且荧光团Trp残基处于结合位置中,进一步证明PFUnA和PFTriA可以猝灭HSA的荧光。本文研究结果为阐明长链PFCAs在机体内与血清蛋白的结合机理提供了完整可靠的数据,并为长链PFCAs的毒性评价和毒理学研究提供了理论依据。
Perfluorocarboxylic acids (PFCAs) are widely used in industrial and domestic products because of their hydrophilic and hydrophobic surfactant properties. Perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTriA) are typical representatives of long-chain PFCAs, but in recent years they have been detected more and more frequently in humans and have been found to exhibit endocrine disrupting effects, development Toxicity and teratogenicity. Based on spectroscopy and molecular docking, this article explores the binding patterns of PFUnA and PFTriA to the most abundant human serum albumin (HSA) in the human body. The results showed that both PFUnA and PFTriA quenched the endogenous fluorescence of HSA through the dynamic and static quenching process, which had only one strong affinity site with HSA. PFUnA and HSA bound more tightly than PFTriA. According to the results of thermodynamic calculation, the enthalpy change and entropy change of PFUnA binding to HSA are -26.32 kJ · mol -1 and 21.76 J · mol -1 · K -1, respectively, and their binding is mainly Relying on the electrostatic attraction, PFTriA is mainly composed of van der Waals forces and halogen bonds with HSA, which is an exothermic entropy subtraction process with enthalpy change and entropy change of -39.69 kJ · mol -1 and -25.66 J · mol ~ (-1) -1) · K -1 (-1). Calculated binding distances (r <8 nm) showed a non-radiative energy transfer from HSA to PFUnA and PFTriA. Three-dimensional fluorescence spectroscopy and circular dichroism showed that the binding of PFUnA and PFTriA to HSA not only changed the conformation and microenvironment of HSA, but also caused the decrease of α-helix stability. Substitution experiments and molecular docking further show that PFUnA and PFTriA have high affinity to the sub-domain IIA hydrophobic cavity of HSA via polar bond, hydrophobic interaction and halogen bond, and the fluorophore Trp residues are in the binding sites, further demonstrating that PFUnA And PFTriA quench HSA fluorescence. The results of this study provide complete and reliable data for elucidating the mechanism of long-chain PFCAs binding to serum proteins and provide a theoretical basis for toxicity assessment and toxicology studies of long-chain PFCAs.