Aluminum is the third most abundant element in earth’s crust, but its chemical properties have prevented its presence in the biological cycle of living organisms. Nevertheless, the acidification of the environment due mainly to human intervention has facilitated its solubilitation, thus increasing its bioavailability. Toxic effects of aluminum in the human body have been reported, and this element has been related with neurodegerentative diseases such as Alzheimer Disease. Aluminum has also been claimed to exert an important pro-oxidant activity.

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 The interest in free-radical processes in living systems has increased exponentially during the last decade. The huge complexity of the evolved processes makes necessary the analysis of the problem from a fundamental point of view. Radicals are ubiquitous intermediates in a variety of ordinary biochemical reactions. Some of the radicals that are most abundantly produced in natural biochemical reactions are Reactive Oxygen Species (ROS) such as hydroxyl, hydroperoxyl and superoxide anion, and Reactive Nitrogen Species (RNS), such as nitrogen monoxide and peroxynitrite.

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In the last years has been highlighted the relevance of transition metals as catalysts in oxidative damage processes involving biological macromolecules. Recent studies have shown that transition metals like Fe, Cu, Cd, Cr, Pb, Hg, Ni and V possess the ability to generate reactive oxygen and nitrogen species, ROS and RNS, that is, radicals concerned in biological reactions which may cause severe damage in a wide range of molecules, producing, among other effects, lipid peroxidation, DNA damage, dramatic sulfhydryl decrease, protein alteration, etc., symptomatic of different diseases such as cancer, vascular affections, neurological disorders (Alzheimer’s and Parkinson’s disease), etc.

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The amide bond is the essential structural motif of the protein backbone. The hydrolysis reaction of amides, often used as a model for the cleavage of peptide bonds, is thus of primary concern for living systems. The hydrolysis of non-activated amides is very slow and in most cases undetectable. An amide bond’s stability is ascribed to its partial double bond character, caused by the delocalization between the nitrogen lone pair and the π* orbital of CO bond. As a consequence, amides show a characteristic short C-N bond length and a rigid planar conformation. This stability also has important chemical consequences, a low reactivity toward nucleophilic attacks on the carbon and important basicity shifts of the nitrogen with respect to amines. (more…)

Many proteins are synthesized in biologically inactive forms, and are activated in post-translational processes such as proteolytic cleavage. This process is usually catalyzed by external proteins, but some proteins are able to self-catalyze the reactions without the need for any other protein or cofactor. We are interested in one of this post-translational process, known as protein splicing. In protein splicing, a segment of an inactive protein, the intein (internal protein), is excised from the rest of the protein, and the two flanking domains, the C- and N-exteins, join each other, forming a biologically active protein (see Figure).

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Contact person: Xabier Lopez. email: xabier.lopez@ehu.es