Alsalme Ali, Khan Rais Ahmad, Alkathiri Arwa M, Ali Mohd Sajid, Tabassum Sartaj, Jaafar Mohammed, Al-Lohedan Hamad A
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
Surfactant Research Chair, Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
Bioinorg Chem Appl. 2018 Mar 25;2018:9782419. doi: 10.1155/2018/9782419. eCollection 2018.
-Carbolines (Cs) belong to the naturally occurring alkaloid family, derived from 9H-pyrido[3,4-b]indole, also known as norharmane (Hnor). Knowing the importance of the Cs alkaloid family in biological processes, a comprehensive binding study is reported of four Ag(I) compounds containing the ligand Hnor and having different counteranions, namely, NO, ClO, BF, and PF, with human serum albumin (HSA) as a model protein. Different approaches like UV-visible, fluorescence spectroscopy, circular dichroism (CD), and molecular docking studies have been used for this purpose. The fluorescence results establish that the phenomenon of binding of Ag(Hnor) complexes to HSA can be deduced from the static quenching mechanism. The results showed a significant binding propensity of the used Ag(I) compounds towards HSA. The role of the counteranion on the binding of Ag(I) compounds to HSA appeared to be remarkable. Compounds with (ClO) and (NO) were found to have the most efficient binding towards HSA as compared to BFand PF. Circular dichroism (CD) studies made clear that conformational changes in the secondary structure of HSA were induced by the presence of Ag(I) compounds. Also, the -helical structure of HSA was found to get transformed into a -sheeted structure. Interestingly, (ClO) and (NO) compounds were found to induce most substantial changes in the secondary structure of HSA. The outcome of this study may contribute to understanding the propensity of proteins involved in neurological diseases (such as Alzheimer's and Parkinson's diseases) to undergo a similar transition in the presence of Ag--carboline compounds.
咔啉（Cs）属于天然存在的生物碱家族，源自9H-吡啶并[3,4-b]吲哚，也称为去甲哈尔满（Hnor）。鉴于咔啉生物碱家族在生物过程中的重要性，本文报道了一项以人血清白蛋白（HSA）为模型蛋白，对四种含有配体Hnor且具有不同抗衡阴离子（即NO、ClO、BF和PF）的Ag（I）化合物进行的全面结合研究。为此使用了紫外可见光谱、荧光光谱、圆二色性（CD）和分子对接研究等不同方法。荧光结果表明，Ag（Hnor）配合物与HSA的结合现象可由静态猝灭机制推导得出。结果显示，所用的Ag（I）化合物对HSA具有显著的结合倾向。抗衡阴离子对Ag（I）化合物与HSA结合的作用似乎很显著。与BF和PF相比，含有（ClO）和（NO）的化合物对HSA的结合效率最高。圆二色性（CD）研究表明，Ag（I）化合物的存在会诱导HSA二级结构的构象变化。此外，还发现HSA的α-螺旋结构转变为β-折叠结构。有趣的是，发现含有（ClO）和（NO）的化合物会引起HSA二级结构最显著的变化。这项研究的结果可能有助于理解参与神经疾病（如阿尔茨海默病和帕金森病）的蛋白质在存在Ag-咔啉化合物时发生类似转变的倾向。
