1,354,502 research outputs found
Interazione tra B1-INTEGRINA e SEL1L nello sviluppo del pancreas
No full textBeta1-Integrin and SEL1L interaction in pancreas development Diaferia Giuseppe In the present study we looked at the role of beta1-integrin and SEL1L in beta-cell differentiation through ECM interaction. Using beta-cell specific beta1-integrin KO we showed a dramatic defect in cell-adhesion on extracellular matrixes and a marked reduction in beta-cell mass due to a defect in beta-cell proliferation confirmed by the loss of cyclin D1 expression and the upregulation of the inhibitors p21 and p27. In contrast glucose tolerance was enhanced due to the increased insulin sensitivity. Using an in vitro model of human pancreas development we found SEL1L highly expressed in the developing islet cell clusters and at the basal membrane of undifferentiated acini of the fetal pancreatic tissue while restricted to islet cells in the adult pancreas. In vitro expansion of fetal and adult islet cell clusters on extracellular matrixes as netrin-1 led to a significative upregulation of insulin and PDX-1 expression as well as SEL1L. Coimmunoprecipitation experiments of SEL1L with beta1-integrin suggest that this effect, mediated by ECM, are likely to be integrin dependent. These results point to the essential role of beta1 integrin and SEL1L signaling in pancreatic cell development and proliferatio
Fmoc-diphenylalanine as a suitable building block for the preparation of hybrid materials and their potential applications
No full textDue to its capability to self-assemble in self-supporting hydrogels (HG) under physiological conditions, Fmoc-FF is one of the most studied ultra-short peptide. The structural properties of the resulting hydrogel (mechanical rigidity, entanglement of the fibrillary network, and the thickness of the fibers) strictly depend on the experimental conditions used during the preparation. In the past few years, a broad range of applications in different fields, such as biomedical and industrial fields, have been proposed. However, the research on novel materials with enhanced mechanical properties, stability, and biocompatibility has brought about the development of novel Fmoc-FF-based hybrid systems, in which the ultra-short hydrogelator is combined with others entities such as polysaccharides, polymers, peptides, or organic molecules. The structural features and the potential applications of these novel hybrid materials, with particular attention to tissue engineering, drug delivery, and catalysis, are described here. The aim is to give the readers a tool to design new hybrid nanomaterials based on the Fmoc-FF dipeptide hydrogelator, with appropriate properties for specific applications
Peptide-based building blocks as structural elements for supramolecular Gd-containing MRI contrast agents
No full textMagnetic resonance imaging (MRI) is one of the most important clinic diagnostic tool
used to obtain high‐quality body images. The administration of low‐molecular‐weight
Gd complex–based MRI contrast agents (CAs) permits to increase the 1H relaxation
rate of nearby water molecules, thus modulating signal intensity and contrast
enhancement. Even if highly accurate, MRI modality suffers from its low sensitivity.
Moreover, low‐molecular‐weight CAs rapidly equilibrate between the intravascular
and extravascular spaces after their administration. In order to improve their sensitivity
and limit the extravasation phenomenon, several macromolecular and supramolecular
multimeric gadolinium complexes (dendrimers, polymers, carbon nanostructures,
micelles, and liposomes) have been designed until now. Because of their biocompatibility,
low immunogenicity, low cost, and easy synthetic modification, peptides are
attractive building blocks for the fabbrication of novel materials for biomedical
applications. We report on the state of the art of supramolecular CAs obtained by
self‐assembly of three different classes of building blocks containing a peptide
sequence, a gadolinium complex, and, if necessary, a third functional portion achieving
the organization process
Self-Assembly of PEGylated Diphenylalanines into Photoluminescent Fibrillary Aggregates
No full textDiphenylalanine (FF) represents one of the most studied self-assembling peptides. As a consequence of non-covalent interactions (aromatic stacking and hydrogen bonds), FF is able to generate different nanoarchitectures, proposed in the last years as innovative tools for several applications. The identification of the relationship between the chemical building block composition and the supramolecular structure of final material is the objective of intense research. Different FF analogues were synthetized and studied. At the state of art, in the high number of FF derivatives, PEGylation has not been studied yet, notwithstanding its role has been demonstrated for longer poly-phenylalanine peptides. Herein, we describe the synthesis and the supramolecular behavior of two PEGylated-FF derivatives, PEG2-FF and PEG6-FF, in which the zwitterionic FF has been derivatized at the N-terminus with two or six ethoxylic moieties, respectively. Spectroscopic methodologies (fluorescence, circular dichroism, Fourier transform infrared) allowed the identification of their secondary structure and the calculation of the critical aggregation concentration. PEGylation of the dipeptide induces a modification of the conformational organization from nanotubes with hexagonal symmetry to β-sheet rich fibrils. This structural organization confers photoluminescence features to the supramolecular structures
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