Roy Swarup, Nandi Raj Kumar, Ganai Sintu, Majumdar K C, Das Tapan K
Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India.
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India.
J Pharm Anal. 2017 Feb;7(1):19-26. doi: 10.1016/j.jpha.2016.05.009. Epub 2016 Jun 15.
Interaction between bovine serum albumin (BSA) and phosphorus heterocycles (PHs) was studied using multi-spectroscopic techniques. The results indicated the high binding affinity of PHs to BSA as it quenches the intrinsic fluorescence of BSA. The experimental data suggested the fluorescence quenching mechanism between PHs and BSA as a dynamic quenching. From the UV-vis studies, the apparent association constant (K) was found to be 9.25×10, 1.27×10 and 9.01×10 L/mol for the interaction of BSA with PH-1, PH-2 and PH-3 respectively. According to the Förster's non-radiation energy transfer (FRET) theory, the binding distances between BSA and PHs were calculated. The binding distances (r) of PH-1, PH-2 and PH-3 were found to be 2.86, 3.03, and 5.12 nm, respectively, indicating energy transfer occurs between BSA and PHs. The binding constants of the PHs obtained from the fluorescence quenching data were found to be decreased with increase of temperature. The negative values of the thermodynamic parameters ΔH, ΔS and ΔG at different temperatures revealed that the binding process is spontaneous; hydrogen bonds and van der Waals interaction were the main force to stabilize the complex. The microenvironment of the protein-binding site was studied by synchronous fluorescence and circular dichroism (CD) techniques and data indicated that the conformation of BSA changed in the presence of PHs. Finally, we studied the BSA-PHs docking using Autodock and results suggest that PHs is located in the cleft between the domains of BSA.
利用多种光谱技术研究了牛血清白蛋白（BSA）与磷杂环（PHs）之间的相互作用。结果表明，PHs对BSA具有高结合亲和力，因为它能淬灭BSA的固有荧光。实验数据表明，PHs与BSA之间的荧光淬灭机制为动态淬灭。通过紫外可见光谱研究发现，BSA与PH-1、PH-2和PH-3相互作用的表观缔合常数（K）分别为9.25×10、1.27×10和9.01×10 L/mol。根据Förster非辐射能量转移（FRET）理论，计算了BSA与PHs之间的结合距离。发现PH-1、PH-2和PH-3的结合距离（r）分别为2.86、3.03和5.12 nm，表明BSA与PHs之间发生了能量转移。从荧光淬灭数据获得的PHs结合常数随温度升高而降低。不同温度下热力学参数ΔH、ΔS和ΔG的负值表明结合过程是自发的；氢键和范德华相互作用是稳定复合物的主要作用力。通过同步荧光和圆二色性（CD）技术研究了蛋白质结合位点的微环境，数据表明在PHs存在下BSA的构象发生了变化。最后，我们使用Autodock研究了BSA-PHs对接，结果表明PHs位于BSA结构域之间的裂隙中。
