Department of Biochemistry and Biophysics, University of Kalyani, Nadia, WB 741235, India.
Department of Chemistry, Indian Institute of Technology Indore, Khandwa Road, Indore 453552, India.
Int J Biol Macromol. 2019 Feb 15;123:221-227. doi: 10.1016/j.ijbiomac.2018.11.012. Epub 2018 Nov 4.
The intermolecular interactions of a homoaromatic tripeptide, H-Tyr-Tyr-Tyr-OH (YYY) with model double-stranded (ds) DNA (ct-DNA) have been investigated by isothermal titration calorimetric (ITC) method along with various biophysical techniques such as fluorescence, time correlated single photon counting (TCSPC) and circular dichroism (CD) spectroscopy. The binding affinity [log (K) at 25 °C] of the YYY to ct-DNA is calculated as ≈4.3. The binding mode of the YYY to ds-DNA is elucidated by fluorescence intercalator displacement (FID) assay, melting temperature analysis, viscosity measurement and salt-induced fluorescence quenching study. The studies establish that the YYY recognizes the groove of the ct-DNA. The temperature dependent ITC studies show that the binding interaction is thermodynamically favourable. The compensation between enthalpy and entropy leads to the overall Gibbs free energy change almost invariant. Finally, the generality of the YYY to recognize ds-DNA has been analyzed with other model ds-DNA, ds26, which reveals almost similar binding affinity of the YYY as ct-DNA. The studies elucidate both the spectroscopic and calorimetric insight of the interactions of a homoaromatic tripeptide with ds-DNA and hold the promise of future applications as DNA targeting drug.
通过等温滴定量热法（ITC）以及荧光、时间相关单光子计数（TCSPC）和圆二色性（CD）光谱等各种生物物理技术，研究了同芳香三肽 H-Tyr-Tyr-Tyr-OH（YYY）与模型双链 DNA（ct-DNA）的分子间相互作用。计算出 YYY 与 ct-DNA 的结合亲和力[25°C 时的 log（K）]约为 4.3。通过荧光插入剂置换（FID）测定、熔点分析、粘度测量和盐诱导荧光猝灭研究阐明了 YYY 与 ds-DNA 的结合模式。研究表明，YYY 识别 ct-DNA 的沟。依赖温度的 ITC 研究表明，结合相互作用在热力学上是有利的。焓和熵之间的补偿导致整体吉布斯自由能变化几乎不变。最后，用其他模型 ds-DNA ds26 分析了 YYY 识别 ds-DNA 的通用性，结果表明 YYY 与 ct-DNA 的结合亲和力几乎相同。这些研究阐明了同芳香三肽与 ds-DNA 相互作用的光谱和量热学见解，并有望作为靶向 DNA 的药物在未来得到应用。
