Mallick Arabinda, Haldar Basudeb, Chattopadhyay Nitin
Department of Chemistry, Jadavpur University, Calcutta-700 032, India.
J Phys Chem B. 2005 Aug 4;109(30):14683-90. doi: 10.1021/jp051367z.
Interaction of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), a biologically active molecule, with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA) have been studied using steady state and picosecond time-resolved fluorescence and fluorescence anisotropy. The polarity dependent intramolecular charge transfer (ICT) process is responsible for the remarkable sensitivity of this biological fluorophore to the protein environments. The CT fluorescence exhibits appreciable hypsochromic shift along with an enhancement in the fluorescence yield, fluorescence anisotropy (r) and fluorescence lifetime upon binding with the proteins. The reduction in the rate of ICT within the hydrophobic interior of albumins leads to an increase in the fluorescence yield and lifetime. Marked increase in the fluorescence anisotropy indicates that the probe molecule is located in a motionally constrained environment within the proteins. Micropolarities in the two proteinous environments have been determined following the polarity sensitivity of the CT emission. Addition of urea to the protein-bound systems leads to a reduction in the fluorescence anisotropy indicating the denaturation of the proteins. Polarity measurements and fluorescence resonance energy transfer (FRET) studies throw light in assessing the location of the fluorophore within the two proteinous media.
利用稳态和皮秒时间分辨荧光以及荧光偏振，研究了具有生物活性的分子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）和人血清白蛋白（HSA）的相互作用。极性依赖的分子内电荷转移（ICT）过程导致这种生物荧光团对蛋白质环境具有显著的敏感性。与蛋白质结合后，CT荧光表现出明显的蓝移，同时荧光产率、荧光偏振（r）和荧光寿命增强。白蛋白疏水内部ICT速率的降低导致荧光产率和寿命增加。荧光偏振的显著增加表明探针分子位于蛋白质内运动受限的环境中。根据CT发射的极性敏感性，测定了两种蛋白质环境中的微极性。向蛋白质结合系统中添加尿素会导致荧光偏振降低，表明蛋白质发生了变性。极性测量和荧光共振能量转移（FRET）研究有助于评估荧光团在两种蛋白质介质中的位置。
