Maiti Tushar Kanti, Ghosh Kalyan Sundar, Debnath Joy, Dasgupta Swagata
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Int J Biol Macromol. 2006 May 30;38(3-5):197-202. doi: 10.1016/j.ijbiomac.2006.02.015. Epub 2006 Mar 6.
All-trans retinoic acid derived from vitamin A is an essential component for the modulation of angiogenesis, the process of blood vessel formation. We have investigated the binding of all-trans retinoic acid to the carrier protein, human serum albumin (HSA) under physiological conditions. Fluorescence quenching methods in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy were used for the biophysical studies. The binding parameters were determined by a Scatchard plot and the results found to be consistent with those obtained from a modified Stern-Volmer equation. From the thermodynamic parameters calculated according to the van't Hoff equation, the enthalpy change DeltaH(0) and entropy change DeltaS(0) are found to be 106.17 and 106.14J/molK, respectively. These values suggest that apart from hydrophobic interactions electrostatic interactions are present. Changes in the CD spectra and FT-IR spectra were observed upon ligand binding along with a significant degree of tryptophan fluorescence quenching on complex formation. Docking studies performed substantiated our experimental findings and it was observed that all-trans retinoic acid hydrogen bonded with Trp 214 and Asp 451 residues of subdomain IIA and IIIA of HSA, respectively.
源自维生素A的全反式维甲酸是调节血管生成（即血管形成过程）的一种重要成分。我们已经研究了在生理条件下全反式维甲酸与载体蛋白人血清白蛋白（HSA）的结合情况。结合荧光猝灭法、傅里叶变换红外（FT-IR）光谱和圆二色性（CD）光谱进行生物物理研究。通过Scatchard图确定结合参数，结果发现与从修正的Stern-Volmer方程获得的结果一致。根据范特霍夫方程计算的热力学参数显示，焓变ΔH(0)和熵变ΔS(0)分别为106.17和106.14J/molK。这些值表明除了疏水相互作用外还存在静电相互作用。配体结合后观察到CD光谱和FT-IR光谱发生变化，同时复合物形成时色氨酸荧光有显著程度的猝灭。进行的对接研究证实了我们的实验结果，并且观察到全反式维甲酸分别与HSA亚结构域IIA和IIIA的Trp 214和Asp 451残基形成氢键。
