In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and... more In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and aconitase, require a complex machinery to assemble and insert their associated [Fe-S] clusters. So far, three different types of [Fe-S] cluster biosynthetic systems have been identified and these have been designated nif, isc and suf. In the present work, we show that the nif-specific [Fe-S] cluster biosynthetic system from Azotobacter vinelandii, which is required for nitrogenase maturation, cannot functionally replace the isc [Fe-S] cluster system used for the maturation of other [Fe-S] proteins, such as aconitase. The results indicate that, in certain cases, [Fe-S] cluster biosynthetic machineries have evolved to perform only specialized functions.
Mobilization of the L-cysteine sulfur for the persulfuration of the rhodanese of Azotobacter vine... more Mobilization of the L-cysteine sulfur for the persulfuration of the rhodanese of Azotobacter vinelandii, RhdA, can be mediated by the A. vinelandii cysteine desulfurases, IscS and NifS. The amount of cysteine was higher in mutant strains lacking rhdA (MV474) than in wild type. The diazotrophic growth of MV474 was impaired. Taking into account the functional results about rhodanese-like proteins and RhdA itself, it is suggested that RhdA-dependent modulation of L-cysteine levels must deal with a redox-related process.
Lignin, the second most abundant organic natural compound in the world is a promising source of n... more Lignin, the second most abundant organic natural compound in the world is a promising source of new materials derived from renewable resources. Currently, lignin is used in low value-added applications and for energy production of pulp and paper processes. Only a small amount is being used for other applications. The aim of this study was to analyse the effects of acid gradient precipitation on the composition of lignin, extracted from black liquor produced by CMPC Celulose Riograndense, Brazil. Lignins were precipitated at different pH conditions by using hydrochloric acid (HCl) and sulphuric acid (H2SO4). Obtained lignin samples were characterised by X-ray diffraction in order to study the possibility of crystalline phases formation and the purity determination of precipitated lignin samples. The structure of lignins showed a variable composition according to the acid and the pH value used for its precipitation. Presence of crystalline phase was detected in precipitated Kraft lign...
In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and... more In recent years, it has become evident that [Fe-S] proteins, such as hydrogenase, nitrogenase and aconitase, require a complex machinery to assemble and insert their associated [Fe-S] clusters. So far, three different types of [Fe-S] cluster biosynthetic systems have been identified and these have been designated nif, isc and suf. In the present work, we show that the nif-specific [Fe-S] cluster biosynthetic system from Azotobacter vinelandii, which is required for nitrogenase maturation, cannot functionally replace the isc [Fe-S] cluster system used for the maturation of other [Fe-S] proteins, such as aconitase. The results indicate that, in certain cases, [Fe-S] cluster biosynthetic machineries have evolved to perform only specialized functions.
Mobilization of the L-cysteine sulfur for the persulfuration of the rhodanese of Azotobacter vine... more Mobilization of the L-cysteine sulfur for the persulfuration of the rhodanese of Azotobacter vinelandii, RhdA, can be mediated by the A. vinelandii cysteine desulfurases, IscS and NifS. The amount of cysteine was higher in mutant strains lacking rhdA (MV474) than in wild type. The diazotrophic growth of MV474 was impaired. Taking into account the functional results about rhodanese-like proteins and RhdA itself, it is suggested that RhdA-dependent modulation of L-cysteine levels must deal with a redox-related process.
Lignin, the second most abundant organic natural compound in the world is a promising source of n... more Lignin, the second most abundant organic natural compound in the world is a promising source of new materials derived from renewable resources. Currently, lignin is used in low value-added applications and for energy production of pulp and paper processes. Only a small amount is being used for other applications. The aim of this study was to analyse the effects of acid gradient precipitation on the composition of lignin, extracted from black liquor produced by CMPC Celulose Riograndense, Brazil. Lignins were precipitated at different pH conditions by using hydrochloric acid (HCl) and sulphuric acid (H2SO4). Obtained lignin samples were characterised by X-ray diffraction in order to study the possibility of crystalline phases formation and the purity determination of precipitated lignin samples. The structure of lignins showed a variable composition according to the acid and the pH value used for its precipitation. Presence of crystalline phase was detected in precipitated Kraft lign...
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Papers by Patricia Dos Santos