Güette Fernández Jorge R, Pita Xiomara Narváez, Meléndez Enrique, Parés Matos Elsie I
Department of Chemistry, University of Puerto Rico, USA.
Int J Mol Biol (Edmond). 2020;5(3):79-109. Epub 2020 Jul 31.
Metallocene dichlorides (CpM(IV)Cl) are the first class of small and hydrophobic organometallic compounds classified as anticancer agents against numerous cancer cell lines and tumors. In this study, the antiproliferative activities of CpVCl,CpNbCl, CpHfCl and CpZrClwere assessed on two human cancer cell lines (HT-29 and MCF-7) using MTT assay. Spectroscopic studies were also conducted using these and other known metallocene dichlorides on apo-human transferrin (apo-hTf) at pH 7.4. UV-Vis and CD showed that their interaction with apo-hTf could induce conformational changes of its secondary structure during binding process. In fluorescence, a decrease in intensity of the emission peak was observed when the apo-hTf:CpM(IV)Cl complex is being formed, probably due to changes in the microenvironment of its tyrosine and tryptophan residues. Among all metallocene dichlorides studied, CpVCl has the strong ability to quench the intrinsic fluorescence of apo-hTf through a static quenching mechanism. The association constants for each protein-compound complex were also determined at different temperatures (296 K, 303 K, 310 K, and 317 K) based on fluorescence quenching results. Positive enthalpy changes () and entropy changes () as well as negative free energies () suggest that hydrophobic interactions are the main intermolecular forces involved in the binding process, probably via an endothermic and spontaneous reaction mechanism. The distance, , between donor (apo-hTf) and acceptor (CpM(IV)Cl) obtained according to Forster's theory of non-radiation energy transfer suggest that the energy transfer from apo-hTf to CpM(IV)Cl occurs with high probability and distances obtained by FRET with high accuracy.
二氯茂金属（CpM(IV)Cl）是第一类被归类为抗癌剂的小型疏水性有机金属化合物，对多种癌细胞系和肿瘤具有抗癌作用。在本研究中，使用MTT法评估了CpVCl、CpNbCl、CpHfCl和CpZrCl对两种人类癌细胞系（HT - 29和MCF - 7）的抗增殖活性。还使用这些以及其他已知的二氯茂金属在pH 7.4条件下对脱铁人转铁蛋白（apo - hTf）进行了光谱研究。紫外可见光谱（UV - Vis）和圆二色光谱（CD）表明，它们与apo - hTf的相互作用在结合过程中可诱导其二级结构的构象变化。在荧光方面，当形成apo - hTf:CpM(IV)Cl复合物时，观察到发射峰强度降低，这可能是由于其酪氨酸和色氨酸残基的微环境发生了变化。在所有研究的二氯茂金属中，CpVCl具有通过静态猝灭机制猝灭apo - hTf固有荧光的强大能力。还根据荧光猝灭结果在不同温度（296 K, 303 K, 310 K和317 K）下测定了每种蛋白质 - 化合物复合物的缔合常数。正的焓变（）和熵变（）以及负的自由能（）表明，疏水相互作用是结合过程中主要的分子间作用力，可能通过吸热和自发反应机制实现。根据福斯特非辐射能量转移理论获得的供体（apo - hTf）和受体（CpM(IV)Cl）之间的距离表明，从apo - hTf到CpM(IV)Cl的能量转移具有很高的概率，并且通过荧光共振能量转移（FRET）获得的距离具有很高的准确性。
