2 resultados para Lipoprotein oxidation

em AMS Tesi di Dottorato - Alm@DL - Università di Bologna


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The Reverse Vaccinology (RV) approach allows using genomic information for the delineation of new protein-based vaccines starting from an in silico analysis. The first powerful example of the application of the RV approach is given by the development of a protein-based vaccine against serogroup B Meningococcus. A similar approach was also used to identify new Staphylococcus aureus vaccine candidates, including the ferric hydroxamate-binding lipoprotein FhuD2. S. aureus is a widespread human pathogen, which employs various different strategies for iron uptake, including: (i) siderophore-mediated iron acquisition using the endogenous siderophores staphyloferrin A and B, (ii) siderophore-mediated iron acquisition using xeno-siderophores (the pathway exploited by FhuD2) and (iii) heme-mediated iron acquisition. In this work the high resolution crystal structure of FhuD2 in the iron (III)-siderophore-bound form was determined. FhuD2 belongs to the Periplasmic Binding Protein family (PBP ) class III, and is principally formed by two globular domains, at the N- and C-termini of the protein, that make up a cleft where ferrichrome-iron (III) is bound. The N- and C-terminal domains, connected by a single long α-helix, present Rossmann-like folds, showing a β-stranded core and an α-helical periphery, which do not undergo extensive structural rearrangement when they interact with the ligand, typical of class III PBP members. The structure shows that ferrichrome-bound iron does not come directly into contact with the protein; rather, the metal ion is fully coordinated by six oxygen donors of the hydroxamate groups of three ornithine residues, which, with the three glycine residues, make up the peptide backbone of ferrichrome. Furthermore, it was found that iron-free ferrichrome is able to subtract iron from transferrin. This study shows for the first time the structure of FhuD2, which was found to bind to siderophores ,and that the protein plays an important role in S. aureus colonization and infection phases.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This work deals with the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) using metal supported catalysts. Catalysts were prepared from the immobilisation of preformed monometallic (Au, Pd) and bimetallic (AuCu, AuPd) nanoparticles on commercial oxides (TiO2, CeO2). Au-TiO2 catalyst was found to be very active for HMF oxidation; however, this system deactivated very fast. For this reason, we prepared bimetallic gold-copper nanoparticles and an increase in the catalytic activity was observed together with an increase in catalyst stability. In order to optimise the interaction of the metal active phase with the support, Au and AuCu nanoparticles were supported onto CeO2. Au-CeO2 catalyst was found to be more active than the bimetallic one, leading to the conclusion that in this case the most important feature is the interaction between gold and the support. Catalyst pre-treatments (calcination and washing) were carried out to maximise the contact between the metal and the oxide and an increase in the FDCA production could be observed. The presence of ceria defective sites was crucial for FDCA formation. Mesoporous cerium oxide was synthesised with the hard template method and was used as support for Au nanoparticles to promote the catalytic activity. In order to study the role of active phase in HMF oxidation, PdAu nanoparticles were supported onto TiO2. Au and Pd monometallic catalysts were very active in the formation of HMFCA (5-hydroxymethyl-2-furan carboxylic acid), but Pd was not able to convert it, leading to a low FDCA yield. The calcination of PdAu catalysts led to Pd segregation on the particles surface, which changed the reaction pathway and included an important contribution of the Cannizzaro reaction. PVP protected PdAu nanoparticles, synthesised with different morphologies (core-shell and alloyed structure), confirmed the presence of a different reaction mechanism when the metal surface composition changes.