Structure and Morphology of Silver Nanoparticles on the (111) Surface of Cerium Oxide

The structure of Ag nanoparticles of different size, supported on the cerium oxide (111) surface, was investigated by X-ray absorption fine structure at the Ag K-edge. The results of the data analysis in the near and extended energy range are interpreted with the help of the results obtained by X-ray photoelectron spectroscopy and scanning tunneling microscopy measurements and allow to obtain a detailed atomic scale description of the model system investigated. The Ag nanoparticles have an average size of a few tens of angstroms, which increases with increasing deposited Ag amount. The nanoparticles show a slight tendency to nucleate at the step edges between different cerium oxide layers and they have a face centered cubic structure with an Ag-Ag interatomic distance contracted by 3-4% with respect to the bulk value. The interatomic distance contraction is mainly ascribed to dimensionality induced effects, while epitaxial effects have a minor role. The presence of Ag-O bonds at the interface between the nanoparticles and the supporting oxide is also detected. The Ag-O interatomic distance decreases with decreasing nanoparticle size

No Man's Land : The Photographs of Lynne Cohen = Le no man's land : Les photographies de Lynne Cohen

Changes in phytic acid content, activity of phytase and α-amylase in rye breads were determined during rye bread making. The activity of phytase is highest in grain and flour whereas the activity in the sourdoughs is almost the half of the activity in the flour. The activity was unchanged in the dough after mixing and proofing. Degradation of phytic acid (IP6) into lower inositol-phosphates and free phosphate is almost completed during the production of rye bread with long fermentation time whereas the degradation is less completed when whole grains are included in the recipe. In rye bread made from milled rye (DB00), 99% of IP6 is degraded and IP3 becomes the dominating inositol-phosphate in this bread type presumably resulting in a high level of bioavailable minerals. In rye bread made with 30% grains (SB30), 94% of the IP6 content was reduced with IP4 and IP3 being the dominating lower inositol-phosphates. In rye bread made with 50% whole grains (KB50) the degradation of IP6 was 82%, and the three inositol-phosphates IP5, IP4 and IP3 were found in equal amount in this bread type. Due to significant amounts of phytic acid and remaining IP5, some of the minerals might not be available for human absorption after consumption of this bread type

Interaction of the chaperone calreticulin with proteins and peptides of different structural classes

The interaction of calreticulin with native and denatured forms and polypeptides in proteolytic digests of proteins representing structural classes of all-α-helix (hemoglobin, serum albumin), all-β-sheet (IgG) and α-helix + β-sheets (lysozyme, ovalbumin) was investigated. The binding of calreticulin to denatured proteins was found to depend on conformation and structural class of the protein. No interaction was observed with the native proteins, whereas binding was seen for the denatured proteins, the order of interaction being lysozyme = IgG > ovalbumin hemoglobin = serum albumin. Moreover, the interaction between calreticulin and the heat-denatured proteins depended on the temperature and time used for denaturation and the degree of proteolytic fragmentation. Calreticulin bound well to peptides in proteolytic digests from protease K or chymotrypsin treatment of lysozyme, IgG and ovalbumin but weakly or not at all to peptides in proteolytic digests of hemoglobin and serum albumin. Synthetic peptides from lysozyme and ovalbumin confirmed binding to hydrophobic peptides from these proteins. These results show that calreticulin has the ability to interact with denatured and fragmented forms of proteins with a preference for β-strand structure and hydrophobicity.10 page(s