The synthesis and the structural characterization of dipeptides composed of unnatural fluorine-substituted β(2,3)-diarylamino acid and L-alanine are reported. Depending on the stereochemistry of the β amino acid, these dipeptides are able to self-assemble into proteolytic stable nanotubes. These architectures were able to enter the cell and locate in the cytoplasmic/perinuclear region and represent interesting candidates for biomedical applications.
Plants, algae, and their derivatives (paper, textiles, etc.) are complex systems that are chiefly composed of a web of cellulose fibers. The arrangement of solvents within the polymeric structure is of great importance since cellulose degradation is strongly influenced by water accessibility and external agents. In this paper we develop a model that is able to deconvolve the scattering contributions of both polymeric structures and solvent clusters trapped along the polymeric fibers. The surface morphology of cellulose fibers and the spatial distribution of water-filled pores and their dimensions have been recovered from small angle neutron scattering and atomic force microscopy data in function with paper degradation. In addition to providing a boost to the effort to preserve cellulose-supported material (included cultural heritage), the relevance of our model resides in the exploitation of a large number of biopolymer networks that are known to share structures similar to that of cellulose.
We report an extended x-ray absorption fine-structure investigation on the Mn K absorption edge in La 1−x Ca x MnO 3 as a function of temperature and magnetic field. The results provide microscopic evidence that the modifications in the local structure around Mn atomic sites, as a function of temperature and applied magnetic field, are directly related to the magneto-transport properties of these materials.
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