Mallick Arabinda, Bera Subhash Chandra, Maiti Subhendu, Chattopadhyay Nitin
Department of Chemistry, Jadavpur University, Calcutta-700 032, India.
Biophys Chem. 2004 Dec 1;112(1):9-14. doi: 10.1016/j.bpc.2004.06.009.
Interaction of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ) with a model transport protein, bovine serum albumin (BSA), has been studied using steady state fluorescence and fluorescence anisotropy experiments. Upon binding with BSA, the charge transfer (CT) fluorescence exhibits appreciable hypsochromic shift along with an enhancement in the fluorescence intensity. Gradual addition of BSA leads to the marked increase in the fluorescence anisotropy (r). From the high value of fluorescence anisotropy (r=0.30) it is argued that the probe molecule is located in motionally restricted environment of the protein. Addition of urea to the protein bound AODIQ leads to the decrease in fluorescence intensity as well as fluorescence anisotropy (r) indicating the release of AODIQ molecule to the aqueous buffer medium, thus supporting the idea that the protein, in its native form, binds with the probe. The binding constant and free energy change (DeltaG(0)) for the interaction of AODIQ with BSA have been evaluated from relevant fluorescence data. Polarity of the microenvironment has been determined from a comparison of the variation of fluorescence property of the probe in dioxane-water mixture with varying composition.
利用稳态荧光和荧光偏振实验研究了3-乙酰基-4-氧代-6,7-二氢-12H吲哚并-[2,3-a]喹嗪（AODIQ）与模型转运蛋白牛血清白蛋白（BSA）的相互作用。与BSA结合后，电荷转移（CT）荧光表现出明显的紫移以及荧光强度增强。逐步加入BSA会导致荧光偏振（r）显著增加。从高荧光偏振值（r = 0.30）可以推断，探针分子位于蛋白质的运动受限环境中。向与蛋白质结合的AODIQ中加入尿素会导致荧光强度和荧光偏振（r）降低，这表明AODIQ分子释放到水性缓冲介质中，从而支持了蛋白质以天然形式与探针结合的观点。根据相关荧光数据评估了AODIQ与BSA相互作用的结合常数和自由能变化（ΔG(0)）。通过比较探针在不同组成的二氧六环-水混合物中的荧光性质变化，确定了微环境的极性。
