Surface-modified magnetic colloids for affinity adsorption of immunoglobulins

This work describes the preparation, characterization and in vitro adsorption tests of surface-modified magnetoliposomes for affinity binding of (i) anticardiolipin (isotype G) antibodies and (ii) specific isotype E antibodies generated by hypersensitivity reactions in humans with respiratory allergy. In the first case, cardiolipin embedded in the bilayer of magnetoliposomes was used as specific ligand. In the second case, antigenic proteins present in an extract of Dermatophagoids pteronyssinus and Blomia tropicalis mites were covalently coupled on the surface of magnetoliposomes via a diglycolic spacer arm, and used as specific ligands for IgE. Antibody adsorption was performed in a high-gradient magnetophoresis system, using either sera of healthy individuals or a pool of sera from autoimmune or allergic patients. The selectivity and capacity of the system were quantified by a frontal analysis in a capillary column, and by constructing breakthrough curves. The results show that the highest yield and selectivity were obtained if the ligand was extended into the aqueous layer surrounding the magnetoliposome surface. A 100% selectivity was obtained for adsorption of specific IgE, and 8% for IgG. These results demonstrate the potentialities of both types of surface-modified magnetic biocolloids in the field of in vitro diagnosis tests for allergic or autoimmune conditions.     

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Near-critical adsorption of CO2 on 13X zeolite and N2O on silica gel: lack of evidence of critical phenomena

The excess adsorption of CO₂ on 13X zeolite and of N₂O on silica gel has been studied at high pressure using a magnetic suspension balance, i.e. a gravimetric method. Recently, a detailed study on the density distribution in the measuring cell of the magnetic suspension balance showed that a proper approach to thermostatting the unit should be used in order to obtain reliable and accurate excess adsorption measurements. This is particularly important in the vicinity of the critical point of the fluid, where the density is strongly dependent on pressure and temperature. In the past, several effects were observed in our laboratory when measuring near-critical adsorption on 13X zeolite and on silica gel, namely critical adsorption and critical depletion. In the present study, these effects have been checked using the balance in the new thermostatting configuration, and the conclusion can be drawn that the accuracy of the measurement is not sufficient to prove that they indeed occur. More accurate adsorption data for the two systems have been measured and reported.     

Gold Catalysis: Catalyst Oxidation State Dependent Dichotomy in the Cyclization of Furan–Yne Systems with Aromatic Tethers

Four different synthetic strategies led to a variety of furan–yne systems that contained an aryl system in the tether. Due to the short routes to these systems (four steps or less), a small library of substrates could easily be prepared. These were treated with AuCl₃ or with the Gagosz’s catalyst Ph₃PAuNTf₂ complex. The AuCl₃‐catalyzed reactions delivered highly substituted fluorene derivatives, a class of compounds of great importance as precursors for luminophores with extraordinary abilities. Conversely, a different mechanistic pathway was observed with the cationic gold(I) catalyst. In the latter case, a mechanistically interesting reaction cascade initiated a formal alkyne insertion into the furyl‐sp³‐C bond, which gave indene derivatives as the final products. This new reaction pathway depends on the aromatic moiety in the tether, which stabilizes a crucial cationic intermediate as a benzylic cation.     

Unified approach for determining the enthalpic fictive temperature of glasses with arbitrary thermal history

We propose a unified routine to determine the enthalpic fictive temperature of a glass with arbitrary thermal history under isobaric conditions. The technique is validated both experimentally and numerically using a novel approach for modeling of glass relaxation behavior. The technique is applicable to glasses of any thermal history, as proved through a series of numerical simulations where the enthalpic fictive temperature is precisely known within the model. Also, we demonstrate that the enthalpic fictive temperature of a glass can be determined at any calorimetric scan rate in excellent agreement with modeled values.     

High-temperature in situB NMR study of network dynamics in boron-containing glass-forming liquids

In situ high-temperature nuclear magnetic resonance (NMR) spectroscopy can be very useful for probing changes in structure and dynamics in glass-forming liquids, and is a unique method for observing chemical exchange among structural species (e.g. BO₃–BO₄, Qⁿ–Qⁿ⁺¹, and NBO–BO) at the seconds to microseconds time scales. High-temperature ¹¹B MAS NMR line shape measurements were made at about 100 K above the glass transitions on (Na₂O)_0.3(B₂O₃)_0.7 and (Na₂O)_0.2(B₂O₃)_0.21(Al₂O₃)_0.08(SiO₂)_0.51 glass-forming liquids. BO₃ and BO₄ groups are well resolved in ¹¹B MAS NMR spectra at 14.1 T with sample spinning at 5000 Hz. At higher temperatures, partial peak coalescence occurred due to exchange of BO₃ and BO₄. Temperature effects on borate speciation were also determined by varying the fictive temperature (T_f) of glasses, where T_f estimated from differential scanning calorimetry measurements. We combined these complementary data sets to model structural exchange in the liquid state. The time scale of BO₃–BO₄ exchange from NMR data, τ_NMR, appears to be “decoupled” from that of the macroscopic shear relaxation process τ_s derived from the viscosity, however, at higher temperatures, τ_s approaches τ_NMR. The “decoupling” at lower temperature may be related to intermediate-range compositional heterogeneities, and/or fast modifier cation diffusivities which trigger “unsuccessful” network exchange events.     

Monofunctionalized Gold Nanoparticles Stabilized by a Single Dendrimer Form Dumbbell Structures upon Homocoupling

The assembly of dumbbell structures as organic-inorganic hybrid materials is presented. Gold nanoparticles (NPs) with a mean diameter of 1.3 nm were synthesized in very good yields using a stabilizing dendrimer based on benzylic thioether subunits. The extended dendritic ligand covers the NP surface and contains a peripheral protected acetylene, providing coated and monofunctionalized NPs. These NPs themselves can be considered as large molecules, and thus, applying a wet-chemical deprotection/oxidative acetylene coupling protocol exclusively provides dimers of NPs interlinked by a diethynyl bridge. The concept not only enables access to novel organic/inorganic hybrid architectures but also promises new approaches in labeling technology.