Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, Punjab, India.
School of Pharmaceutical Science and Technology,Tianjin University, Tianjin 300072, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Feb 15;191:259-270. doi: 10.1016/j.saa.2017.10.017. Epub 2017 Oct 9.
The current work aims to explore the thermodynamic and conformational aspects for the binding of fluoroquinolone antibacterial drug, levofloxacin (LFC), with bovine serum albumin (BSA) using calorimetric, spectroscopic (UV-visible, fluorescence, circular dichroism, and H NMR), dynamic light scattering (DLS) and computational methods (molecular docking). The binding of LFC with BSA at two sequential sites with higher affinity (~10M) at the first site has been explored by calorimetry whereas the binding at a single site with affinity of the order of ~10M has been observed from fluorescence spectroscopy. The calorimetric study in the presence of additives along with docking analysis reveals the significant role of electrostatic, hydrogen bonding, and hydrophobic interactions in the association process. The slight conformational changes in protein as well as the changes in the water network structure around the binding cavity of protein have been observed from spectroscopic and DLS measurements. The LFC induced quenching of BSA fluorescence was observed to be initiated mainly through the static quenching process and this suggests the formation of ground state LFC-BSA association complex. The stronger interactions of LFC in the cavity of Sudlow site I (subdomain IIA) of protein have been explored from site marker calorimetric and molecular docking study.
本研究旨在采用量热法、光谱法（紫外-可见、荧光、圆二色性和核磁共振）、动态光散射（DLS）和计算方法（分子对接），探索氟喹诺酮类抗菌药物左氧氟沙星（LFC）与牛血清白蛋白（BSA）结合的热力学和构象特征。通过量热法研究发现，LFC 与 BSA 首先在高亲和力（10M）的两个连续结合位点上结合，而荧光光谱法则观察到在单一结合位点上以10M 的亲和力结合。结合添加剂的量热研究和对接分析揭示了静电、氢键和疏水相互作用在结合过程中的重要作用。从光谱和 DLS 测量中观察到蛋白质的轻微构象变化以及结合腔周围的水网络结构的变化。观察到 LFC 诱导 BSA 荧光猝灭主要是通过静态猝灭过程，这表明形成了基态 LFC-BSA 缔合复合物。通过位点标记量热法和分子对接研究，探索了 LFC 在蛋白质 Sudlow 位点 I（亚域 IIA）腔中的更强相互作用。
