Valutazione dell’efficacia protettiva di trattamenti di passivazione a base Cr(III) condotti su acciai zincati per impieghi in campo automobilistico

Due diversi trattamenti di passivazione entrambi a base di cromo trivalente sono stati applicati su acciai nonlegati utilizzati in campo automobilistico, zincati per via galvanica. Sono state studiate sia le caratteristichedegli strati passivanti ottenuti sia la loro efficacia protettiva.Il comportamento a corrosione degli acciai zincati e passivati è stato valutato mediante l’impiego di tecnicheelettrochimiche quali rilievo di curve di polarizzazione, misure del potenziale di libera corrosione e diimpedenza elettrochimica in funzione del tempo, condotte in soluzione di NaCl 0.1 M a 25°C. Analogacaratterizzazione è stata condotta su acciai zincati sottoposti a passivazione di tipo tradizionale medianteimmersione in bagno contenente cromo esavalente. Gli strati passivanti sono stati caratterizzati sia prima chedopo i test di corrosione mediante microscopia elettronica a scansione (SEM) accoppiata a microanalisi EDS.Il contenuto in cromo degli strati è stato determinato mediante spettrometria di assorbimento atomico (AAS).I risultati ottenuti hanno permesso di evidenziare l’efficacia protettiva dei due trattamenti e di metterla aconfronto con quella ottenuta per effetto del trattamento di passivazione con Cr(VI). I test elettrochimici hannoevidenziato una maggiore efficacia protettiva degli strati passivanti originatisi in seguito al trattamento inbagno contenente Cr(III) e sali di Co, rispetto alla classica cromatazione, al contrario di quelli formatisi inseguito al trattamento in bagno con solo Cr(III)

Structural Conformers of (1,3-Dithiol-2-ylidene)ethanethioamides: The Balance Between Thioamide Rotation and Preservation of Classical Sulfur-Sulfur Hypervalent Bonds

The reaction of N-(2-phthalimidoethyl)-N-alkylisopropylamines and S2Cl2 gave 4-N-(2-phthalimidoethyl)-N-alkylamino-5-chloro-1,2-dithiol-3-thiones that quantitatively cycloadded to dimethyl or diethyl acetylenedicarboxylate to give stable thioacid chlorides, which in turn reacted with one equivalent of aniline or a thiole to give thioanilides or a dithioester. Several compounds of this series showed atropisomers that were studied by a combination of dynamic NMR, simulation of the signals, conformational analysis by DFT methods, and single crystal X-ray diffraction, showing a good correlation between the theoretical calculations, the experimental values of energies, and the preferred conformations in the solid state. The steric hindering of the crowded substitution at the central amine group was found to be the reason for the presence of permanent atropisomers in this series of compounds and the cause of a unique disposition of the thioxo group at close-to-right angles with respect to the plane defined by the 1,3-dithiole ring in the dithiafulvene derivatives, thus breaking the sulfur–sulfur hypervalent bond that is always found in this kind of compounds.Ministerio de Economıá y Competitividad, Spain (Project CTQ2012- 31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1), and the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411

Structural Analysis of a Peptide Fragment of Transmembrane Transporter Protein Bilitranslocase

Using a combination of genomic and post-genomic approaches is rapidly altering the number of identified human influx carriers. A transmembrane protein bilitranslocase (TCDB 2.A.65) has long attracted attention because of its function as an organic anion carrier. It has also been identified as a potential membrane transporter for cellular uptake of several drugs and due to its implication in drug uptake, it is extremely important to advance the knowledge about its structure. However, at present, only the primary structure of bilitranslocase is known. In our work, transmembrane subunits of bilitranslocase were predicted by a previously developed chemometrics model and the stability of these polypeptide chains were studied by molecular dynamics (MD) simulation. Furthermore, sodium dodecyl sulfate (SDS) micelles were used as a model of cell membrane and herein we present a high-resolution 3D structure of an 18 amino acid residues long peptide corresponding to the third transmembrane part of bilitranslocase obtained by use of multidimensional NMR spectroscopy. It has been experimentally confirmed that one of the transmembrane segments of bilitranslocase has alpha helical structure with hydrophilic amino acid residues oriented towards one side, thus capable of forming a channel in the membrane

Transcriptional Responses of Resistant and Susceptible Fish Clones to the Bacterial Pathogen Flavobacterium psychrophilum

Flavobacterium psychrophilum is a bacterial species that represents one of the most important pathogens for aquaculture worldwide, especially for salmonids. To gain insights into the genetic basis of the natural resistance to F. psychrophilum, we selected homozygous clones of rainbow trout with contrasted susceptibility to the infection. We compared the transcriptional response to the bacteria in the pronephros of a susceptible and a resistant line by micro-array analysis five days after infection. While the basal transcriptome of healthy fish was significantly different in the resistant and susceptible lines, the transcriptome modifications induced by the bacteria involved essentially the same genes and pathways. The response to F. psychrophilum involved antimicrobial peptides, complement, and a number of enzymes and chemokines. The matrix metalloproteases mmp9 and mmp13 were among the most highly induced genes in both genetic backgrounds. Key genes of both pro- and anti-inflammatory response such as IL1 and IL10, were up-regulated with a greater magnitude in susceptible animals where the bacterial load was also much higher. While higher resistance to F. psychrophilum does not seem to be based on extensive differences in the orientation of the immune response, several genes including complement C3 showed stronger induction in the resistant fish. They may be important for the variation of susceptibility to the infection