Collecge of Life and Environmental Science, Minzu University of China, Beijing, 100081, China.
Luminescence. 2013 Nov-Dec;28(6):933-41. doi: 10.1002/bio.2462. Epub 2012 Dec 12.
This study was designed to examine the interaction of methacyline (METC) with human serum albumin (HSA) by multispectroscopy and a molecular modeling method under simulative physiological conditions. The quenching mechanism was suggested to be static quenching based on fluorescence and ultraviolet-visible (UV-Vis) spectroscopy. According to the Vant' Hoff equation, the values of enthalpy (∆H) and entropy change (∆S) were calculated to be -95.29 kJ/mol and -218.13 J/mol/K, indicating that the main driving force of the interaction between HSA and METC were hydrogen bonds and van der Waals's forces. By performing displacement measurements, the specific binding of METC in the vicinity of Sudlow's site I of HSA was clarified. An apparent distance of 3.05 nm between Trp214 and METC was obtained via the fluorescence resonance energy transfer (FRET) method. Furthermore, the binding details between METC and HSA were further confirmed by molecular docking studies, which revealed that METC was bound at subdomain IIA through multiple interactions, such as hydrophobic effect, polar forces, hydrogen bonding, etc. The results of three-dimensional fluorescence and Fourier transform infrared (FTIR) spectroscopy showed that METC caused conformational and some microenvironmental changes in HSA and reduced the α-helix significantly in the range of 52.3-40.4% in HSA secondary structure. Moreover, the coexistence of metal ions such as Ca(2+), Al(3+), Fe(3+), Zn(2+), Cu(2+), Cr(3+) and Cd(2+) can decrease the binding constants of METC-HSA.
本研究旨在模拟生理条件下，通过多光谱和分子建模方法研究美他环素（METC）与人体血清白蛋白（HSA）的相互作用。荧光和紫外-可见（UV-Vis）光谱研究表明，猝灭机制为静态猝灭。根据范特霍夫方程，计算得到焓变（∆H）和熵变（∆S）的值分别为-95.29 kJ/mol 和-218.13 J/mol/K，表明 HSA 与 METC 相互作用的主要驱动力是氢键和范德华力。通过进行置换测量，明确了 METC 在 HSA 中 Sudlow 位点 I 附近的特异性结合。荧光共振能量转移（FRET）方法得出色氨酸（Trp214）与 METC 之间的表观距离为 3.05nm。此外，通过分子对接研究进一步证实了 METC 与 HSA 之间的结合细节，结果表明 METC 通过多种相互作用（如疏水作用、极性力、氢键等）结合在亚域 IIA 上。三维荧光和傅里叶变换红外（FTIR）光谱的结果表明，METC 导致 HSA 的构象和一些微环境发生变化，并使 HSA 二级结构中 52.3-40.4%的α-螺旋显著减少。此外，金属离子如 Ca(2+)、Al(3+)、Fe(3+)、Zn(2+)、Cu(2+)、Cr(3+)和 Cd(2+)的共存会降低 METC-HSA 的结合常数。
