Aniline incorporated silica nanobubbles

We report the synthesis of stearate functionalized nanobubbles of SiO2 with a few aniline molecules inside, represented as C6H5NH2@SiO2@stearate, exhibiting fluorescence with red-shifted emission. Stearic acid functionalization allows the materials to be handled just as free molecules, for dissolution, precipitation, storage etc. The methodology adopted involves adsorption of aniline on the surface of gold nanoparticles with subsequent growth of a silica shell through monolayers, followed by the selective removal of the metal core either using sodium cyanide or by a new reaction involving halocarbons. The material is stable and can be stored for extended periods without loss of fluorescence. Spectroscopic and voltammetric properties of the system were studied in order to understand the interaction of aniline with the shell as well as the monolayer, whilst transmission electron microscopy has been used to study the silica shell

Altered thymic differentiation and modulation of arthritis by invariant NKT cells expressing mutant ZAP70

Various subsets of invariant natural killer T (iNKT) cells with different cytokine productions develop in the mouse thymus, but the factors driving their differentiation remain unclear. Here we show that hypomorphic alleles of Zap70 or chemical inhibition of Zap70 catalysis leads to an increase of IFN-gamma-producing iNKT cells (NKT1 cells), suggesting that NKT1 cells may require a lower TCR signal threshold. Zap70 mutant mice develop IL-17-dependent arthritis. In a mouse experimental arthritis model, NKT17 cells are increased as the disease progresses, while NKT1 numbers negatively correlates with disease severity, with this protective effect of NKT1 linked to their IFN-gamma expression. NKT1 cells are also present in the synovial fluid of arthritis patients. Our data therefore suggest that TCR signal strength during thymic differentiation may influence not only IFN-gamma production, but also the protective function of iNKT cells in arthritis

Characterization of Bodipy Dimers Formed in a Molecularly Confined Environment

Recently, Johansson and co-workers provided the first direct evidence for the existence of nonfluorescent bodipy (4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene) H dimers in double-labeled proteins and fluorescent J dimers in labeled lipid vesicles (Bergstrom, F.; et al. J. Am. Chem. Soc. 2002, 124, 196), allowing for the calculation of many of the properties of the dimers. Herein, we report on the use of molecular confinement within a sodium silicate derived glass to provide a highly reproducible system wherein nonfluorescent bodipy H dimers can be formed from the free probe essentially quantitatively without any interference from higher-order aggregates or fluorescent J dimers. The formation of the H dimer followed an unexpected first order kinetic process. On the basis of analysis of the fluorescence anisotropy of the entrapped monomer, it was concluded that the H-dimer formation was promoted by adsorption of monomers onto the silica surface (rate limiting step), followed by rapid dimerization. Using exciton coupling theory, it was determined that the H dimer consisted of two strongly coupled monomers that were stacked in a parallel orientation with a distance of 7.6 Å between the monomer units. The transition dipole moment of the monomer was determined to be 26.6 × 10-30 C m (8.1 D), the emission quantum yield of the H dimer was found to be close to zero, and the Förster distance for energy transfer between the monomer and H dimer was calculated to be 56 ± 2 Å. All of these values are in excellent agreement with those determined by Johansson et al

Direct and Indirect Monitoring of Peptide−Silica Interactions Using Time-Resolved Fluorescence Anisotropy

The present work extends the application of time-resolved fluorescence anisotropy (TRFA) of a cationic probe rhodamine 6G (R6G) in aqueous Ludox to in situ monitoring of peptide adsorption onto the silica particles. Steady-state anisotropy and TRFA of R6G in Ludox sols were measured to characterize the extent of the ionic binding of the probe to silica particles in the presence of varying levels of tripeptides of varying charge, including Lys−Trp−Lys (KWK), N-acetylated Lys−Trp−Lys (Ac-KWK), Glu−Trp−Glu (EWE), and N-acetylated Glu−Trp−Glu (Ac-EWE). The results were compared to those obtained by direct observation of peptide adsorption using the steady-state anisotropy of the intrinsic tryptophan residue. Ionic binding of the peptides to Ludox particles produced an increase in the steady-state Trp anisotropy that was dependent on the number of cationic groups present, but the limiting anisotropy values were relatively low, indicating significant rotational freedom of the indole residue in the adsorbed peptides. On the other hand, R6G showed significant decreases in anisotropy in the presence of cationic peptides, consistent with the cationic peptides blocking the adsorption of the dye to the silica surface. Thus, R6G is able to indirectly report on the binding of peptides to Ludox particles. It was noteworthy that, while there were similar trends in the data obtained from steady-state anisotropy and TRFA studies of R6G, the use of steady-state anisotropy to assess binding of peptides overestimated the degree of peptide adsorption relative to the value obtained by TRFA. The study shows that the competitive binding method can be used to assess the binding of various biologically relevant compounds onto silica surfaces and demonstrates the potential of TRFA for probing peptide−silica and protein−silica interactions