ROMO, Adolfo Ignacio Barros. Complexos de cobre com o ligante 2cp-bz-sme, um derivado sulfurado da base clip-phen. Síntese, caracterização e estudos de geração de radicais e clivagem de DNA. 2015. 86 f. Dissertação (Mestrado em Química)-Universidade Federal do Ceará, Fortaleza, 2015. / Submitted by Celia Sena (celiasena@dqoi.ufc.br) on 2017-07-20T17:39:05Z No. of bitstreams: 1 2015_dis_aibromo.pdf: 2488610 bytes, checksum: 2569053eabcca5c69c4678ab7eccc69e (MD5) / Approved for entry into archive by Jairo Viana (jairo@ufc.br) on 2017-08-29T20:42:39Z (GMT) No. of bitstreams: 1 2015_dis_aibromo.pdf: 2488610 bytes, checksum: 2569053eabcca5c69c4678ab7eccc69e (MD5) / Made available in DSpace on 2017-08-29T20:42:39Z (GMT). No. of bitstreams: 1 2015_dis_aibromo.pdf: 2488610 bytes, checksum: 2569053eabcca5c69c4678ab7eccc69e (MD5) Previous issue date: 2015 / Coordination compounds of copper have been invoked as major actors in processes involving the reduction of molecular oxygen, mostly with the generation of radical species whose assignment have so far not been unanimously addressed. In the present work we have joined results acquired on surface and solution to get insights on the radical oxygen species (ROS) generated by a copper(II) coordination compound containing a thioether clip-phen derivative, 1,3-bis(1,10-phenanthrolin-2-yloxy)-N-(4-(methylthio) benzyli-dene)propan-2-amine (2CP-Bz-SMe). The adsorption of the copper(II) complex on gold surface was spontaneously by simple immersion of the metallic substrate in aqueous solution of the complex. The characterization of the modified gold electrode, which was performed by electrochemistry and surface Raman spectroscopy (SERS – Surface Enhanced Raman Scattering), indicated that the adsorption occurs through the sulfur atom of the thioether fragment of the molecule. While surface plasmon resonance (SPR) and electrochemistry of the adsorbed complex indicated the formation of a dimeric Cu(I) intermediate containing molecular oxygen as bridging ligand, scanning electrochemical microscopy images (SECM) pointed for OH• radical generation. Spin trapping measurements acquired by electron paramagnetic resonance (EPR) and nuclease assays run in the presence of radical scavengers, reinforced such conclusions showing that the radical production is dependent on the amount of oxygen and H2O2. Therefore, it is reasonable to assume a catalytic mechanism involving Fenton-like reaction in which the copper(II) complex is, at first, reduced to copper(I). Accordingly, in the presence of oxygen and in acid medium, the reduced compound is oxidized by H2O2 resulting in the recovering of the parent complex and in the generation of OH• that, in turn, must be the ROS responsible for the DNA cleavage. The results obtained during the developing of this proposal were presented at the XVII Brazilian Meeting on Inorganic Chemistry and are in the final compilation stage for publication in peer-reviewed journal / Compostos de coordenação de cobre têm sido considerados peças fundamentais em processos que envolvem a redução de oxigênio molecular, particularmente com a geração de espécies radicalares cujas atribuições, até a atualidade, não são unanimidade. Neste trabalho, foram reunidos resultados obtidos em superfície e em solução a fim de obter informações sobre a espécie reativa de oxigênio (ROS – Reactive Oxygen Species) gerada por um composto de coordenação de cobre(II) contendo um derivado tioéter do ligante clip-phen, 1,3-bis(1,10-fenantrolin-2-iloxi)-N-(4-(metiltio)benzilideno)propan-2-amina (2CP-Bz-SMe). A adsorção do complexo de cobre(II) sobre superfície de ouro foi realizada de forma espontânea por simples imersão do substrato metálico em solução aquosa do complexo. A caracterização do eletrodo de ouro modificado foi feita por eletroquímica e espectroscopia Raman de superfície (SERS – Surface Enhanced Raman Scattering) onde se concluiu que a adsorção ocorre através do átomo de enxofre do fragmento tioéter da molécula. Enquanto os resultados de ressonância de plásmons de superfície (SPR – Surface Plasmon Resonance) e eletroquímica sugeriram a formação de um intermediário dimérico de Cu(I) contendo oxigênio molecular como ligante ponte, imagens de microscopia de varredura eletroquímica (SECM – Scanning Electrochemical Microscopy) indicaram a geração do radical hidroxil, OH•. Os experimentos de captura de spin por ressonância paramagnética de elétrons (EPR – Electron Paramagnetic Resonance) e ensaios de nuclease de DNA, os quais envolveram a utilização de inibidores de ROS, mostram que a geração do radical depende da quantidade de oxigênio e H2O2. Assim, é razoável admitir um mecanismo catalítico envolvendo reações do tipo Fenton onde o complexo de cobre(II) é, inicialmente, reduzido a cobre(I). Na presença de oxigênio e em meio ácido, o composto reduzido é oxidado por H2O2 resultando na regeneração do complexo de partida e na formação do radical OH• que, por sua vez, deve ser a espécie ROS responsável pela clivagem do DNA. Os resultados deste projeto foram apresentados no XVII Brazilian Meeting on Inorganic Chemistry e estão em fase final de compilação para publicação em periódico indexado

Targeting DNA has the advantage over proteins for cancer remediation because of the fewer copies of the ligands required for the desired therapeutic effect. Traditionally, covalent DNA binders like alkylating agents have been used to induce genetic instability through the formation of DNA lesions and strand breaks, leading to cellular apoptosis. The primary drawback of this treatment is the non-specific binding that affects both cancerous and non-cancerous cells. G-quadruplexes are the DNA secondary structures that are present in abundance near the promoter regions of the oncogenes and are involved in the regulation of their activities. A ligand-mediated stabilization of G-quadruplexes in the promoter regions and down-regulation of the associated oncogenes have been validated. In contrast to alkylating agents, G-quadruplex ligands induce genetic stabilization through non-covalent interactions. They can be designed to interact specifically with G-quadruplex DNA over duplex DNA, which reduce side effects arising from the off-targeting. G-quadruplex ligands invariably have the large planar aromatic moiety to interact with G-quadruplexes through π- π stacking interactions. For determining the size effect of the aromatic moiety on stabilization of G-quadruplexes, a series of ligands were synthesized by conjugating nucleobases or 1,10-phenanthroline with an aminoglycoside, neomycin. The resulting conjugates increased the binding affinity synergistically and enabled us to study the effect of the stacking moiety required for G-quadruplex stabilization. Nucleobase-neomycin conjugates did not show stabilization stabilize of human telomeric G-quadruplex. 1,10-Phenanthroline-neomycin conjugate (7b) on the other hand binds to human telomeric G-quadruplex with a Ka of (8.92.4)×108 M-1 and inhibits telomerase activity at 1.56 µM probably through G-quadruplex stabilization. Moving forward, we further enlarged the aromatic moiety by tethering two 1,10-phenantholine molecules together through a five-atom linker. The resulting molecule (2-Clip-phen) was conjugated with various amino-containing side chains. 2-Clip-phen derivatives showed at least 30 times weaker binding to duplex DNA over G-quadruplex DNA. In addition, compounds showed a preference for the antiparallel G-quadruplex conformation over parallel and hybrid G-quadruplex conformations, as shown in the CD spectroscopy studies. Ligands 11 and 13 induced the formation of an antiparallel G-quadruplex from random coils and stabilize it to 60 oC (Tm) in a salt-free condition. Mass spectrometry study showed the formation of a two-tetrad G-quadruplex with the 2-Clip-phen ligand. Docking study showed that the ligand interacts most favorably with antiparallel G-quadruplex conformation, which is supported further by the larger thermal stabilization effect on antiparallel G-quadruplex compared with other G-quadruplex conformations. Our study suggests that 2-Clip-phen can be used as a scaffold for designing G-quadruplex binding ligands that preferentially bind to antiparallel G-quadruplexes, which has never been reported before.