Filipe Tiago de Oliveira, Collaborator
Iron is the most abundant transition metal in biological systems. Iron–containing proteins have the most ubiquitous roles in all three life domains, including transcriptional regulation, sensoring, and an enormous number of catalytic activities in anabolic or catabolic processes, oxidative stress responses, DNA protection, and oxygen transport. Furthermore, iron metabolism is very tightly controlled; e.g. iron excess or deficiencies lead to severe diseases, such as anemia or hemochromatosis, and mutations on iron enzymes may cause a plethora of other diseases. Therefore, a detailed study of iron containing proteins continues to be a fundamental topic in life sciences, strongly related to biomedicine due to its importance for human health, including the combat of invading pathogens.
The biophysical technique best suited to the study of iron proteins is 57Fe Mössbauer spectroscopy (ME), which is based on the recoilless absorption of gamma rays by 57Fe nuclei. This technique is one of the most sensitive methods to determine the chemical characteristics of metal sites, and has been on the basis of the discovery of many novel iron centers, as well on the determination of their enzymatic mechanisms.
We are interested in the flavodiiron proteins (FDPs) which are involved in the protection against oxidative and/or nitrosative stress. FDPs from different micro organisms show distinct specificities for NO or O2 reductase activity (NOR or O2R activity, respectively); some just show NOR or O2R activity, and others both NOR and O2R activities. However, no significant structural differences on the active site environment were found to explain this behavior. These enzymes are present both in prokaryotes and lower eukaryotes, such as pathogenic protozoa and play a decisive role in the detoxification of those two small molecules, and are believed to play an important role in host-pathogen interactions.
Our research is focus on the characterization of trapped intermediates in catalytic reactions of these novel prokaryotic enzymes by Mössbauer and Electron Paramagnetic Resonance spectroscopies together with theoretical studies based on Density Functional Theory. The main goal is to determine their catalytic mechanisms and to address the question of specificity for each one of the substrates. These studies are performed in vitro (purified proteins) and in the whole cells.
- Tiago de Oliveira, F.; Chanda, A.; Banerjee, D.; Shan X.; Mondal, S.; Que L.; Bominaar, E. L.; Münck, E.; Collins, T. J. (2007) “Chemical and Spectroscopic Evidence for an FeV-Oxo Complex.” Science, 315: 835-838.
- Ghosh, A.; Tiago de Oliveira, F.; Yano, T.; Nishioka, T.; Beach, E. S.; Kinoshita, I.; Münck, E.; Ryabov, A. D.; Horwitz, C. P.; Collins, T. J. (2005). "Catalytically Active mu-Oxodiiron(IV) Oxidants from Iron(III) and Dioxygen." J. Am. Chem. Soc. 127(8): 2505-2513.
- Chanda, A., Tiago de Oliveira, F., T. J. Collins, E. Münck and E. L. Bominaar (2008). "Density Functional Theory Study of the Structural, Electronic, and Magnetic Properties of a mu-oxo Bridged Dinuclear Fe(IV) Complex Based on a Tetra-Amido Macrocyclic Ligand." Inorg. Chem. 47 (20): 9372-9379
Em 1958 Rudolf Mössbauer descobriu que a radiação gama (fotões de alta energia) pode ser emitida/absorvida sem perda de energia para o núcleo emissor/receptor, dando origem à espectroscopia de Mössbauer (EM).
Na EM de 57Fe, observa-se a transição entre o estado fundamental nuclear do 57Fe e do nível nuclear a 14.4 keV. O espectro do núcleo isolado seria apenas uma linha sem informação relevante. No entanto, os electrões em torno do núcleo podem fazer com que os níveis energéticos se desdobrem, originando várias transições hiper-finas que contêm muita informação.
O Ferro é extremamente importante para a vida. As metaloproteínas que contêm um ou mais sítios activos com ferro estão envolvidas, por exemplo, no armazenamento/transporte de oxigénio, no transporte de electrões, no metabolismo do azoto e do hidrogénio.
O grupo de EM estuda metaloproteínas que contêm ferro para compreender melhor os seus mecanismos enzimáticos.