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Habilitation Thesis
DOI
10.11606/T.41.2011.tde-19122011-110658
Document
Author
Full name
Luis Eduardo Soares Netto
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2004
Committee
Ribeiro, Alberto Augusto Gonçalves de Freitas Castro (President)
Mascio, Paolo Di
Matioli, Sergio Russo
Menck, Carlos Frederico Martins
Nobrega, Francisco Gorgonio da
Title in Portuguese
Estratégias de defesa antioxidante e o papel de peroxidases dependente de tiól
Keywords in Portuguese
Antioxidante
Peroxidase
Peróxido
Peroxirredoxina
Tiól
Abstract in Portuguese
A importância do O2 na história evolutiva dos seres vivos pode ser compreendida quando analisamos o aparecimentos desse gás na atmosfera terrestre. Durante a história geológica, verificamos que nem sempre a concentração desse gás foi alta como atualmente. A concentração de O2 na atmosfera somente atingiu níveis significativas a cerca de 2,3 bilhões de anos, no período pré-cambriano. Esse período quase coincidiu com o surgimento de cianobactérias, os primeiros organismos fotossintetisadores. Atualmente, as cianobactérias são os únicos procariontes que são capazes de realizar fotossíntese e, portanto, de liberar O2 para a atmosfera. As cianobactérias surgiram a cerca de 2,7 bilhões de anos atrás, mas os níveis de O2 na atmosfera só atingiram os valores atuais 400 milhões de anos depois. Existem várias hipóteses para explicar essa diferença de tempo entre o surgimento de organismos fotossintetisadores e o aumento dos níveis de O2 na atmosfera. Uma delas é que minerais existentes na face da Terra continham metais como o ferro no estado reduzido (Fe+2) e dessa forma O2 inicialmente produzido pelas cianofíceas, teria reagido com esses metais e não se acumulou na atmosfera. Somente quando uma parcela considerável desse metal foi oxidada a Fe+3, é que o O2 começou a acumular na atmosfera. Esse período teria demorado cerca de 400 milhões de anos.
Title in English
Strategies of antioxidant defense and the role of thiol-dependent peroxidades
Keywords in English
Antioxidant
Peroxidase
Peroxide
Peroxiredoxin
Thiol
Abstract in English
The importance of O2 in the evolutionary history of living beings can be understood by analyzing the appearance of this gas in the atmosphere. During the geologic history, we find that not always the concentration of this gas was high as today. The concentration of O2 in the atmosphere only reached significant levels at about 2.3 billion years ago, in pre-Cambrian. This period almost coincided with the emergence of cyanobacteria, the first organisms fotossintetisadores. Currently, cyanobacteria are the only prokaryotes that are capable of photosynthesis and thus releasing O2 into the atmosphere. Cyanobacteria appeared about 2.7 billion years ago, but the levels of O2 in the atmosphere only the current values ​​reached 400 million years later. There are several hypotheses to explain this difference in time between the emergence of organisms fotossintetisadores and increased levels of O2 in the atmosphere. One is that minerals in earth metals such as iron contained in the reduced state (Fe +2) and thus O2 initially produced by cyanobacteria, have reacted to these metals and does not accumulate in the atmosphere. Only when a considerable portion of the metal was oxidized to Fe +3, is that the O2 began to accumulate in the atmosphere. This period would have taken about 400 million years.
 
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Publishing Date
2011-12-19
 
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