In November 1996, I started my PhD research on the soluble hydrogenase of the hyperthermophilic archaeon Pyrococcus furiosus, under the joint supervision of Prof. Baltazar de Castro (Faculty of Sciences, University of Porto, Portugal) and Prof. Fred Hagen (Wageningen Agricultural University, the Netherlands, and later at the Department of Biotechnology, Delft Technical University, the Netherlands). Eventually, the research focus broadened to include other metalloproteins from P. furiosus, which were successively purified and characterized by biochemical, electrochemical and spectroscopic methods (electron paramagnetic resonance, UV-Vis spectroscopy, cofactor analysis, bioinformatics, enzymology, etc.). In March 2001 I graduated as a PhD in Chemistry at the Faculty of Sciences, University of Porto, Portugal. After completing my PhD, I became an Assistant Professor at Universidade Fernando Pessoa (Porto, Portugal). My research focus then moved to the computational study of enzymatic and organic reaction mechanisms using quantum chemistry methods. I have been especially active in the determination of reaction mechanisms of cofactor-free oxygenases, enzymes in the heme biosynthesis pathway and Cu(I)-catalyzed reactions. Lately, I have also turned my attention to the development of enzyme inhibitors and to the critical examination of some alternatives to the chemiosmotic description of oxidative phosphorylation.