The principal difficulty in experimental exploration of the folding and stability of membrane proteins (MPs) is their aggregation outside of the native environment of the lipid bilayer. To circumvent this problem, we recently applied fluorinated nondetergent surfactants that act as chemical chaperones. The ideal chaperone surfactant would 1), maintain the MP in solution; 2), minimally perturb the MP's structure; 3), dissociate from the MP during membrane insertion; and 4), not partition into the lipid bilayer. Here, we compare how surfactants with hemifluorinated (HFTAC) and completely fluorinated (FTAC) hydrophobic chains of different length compare to this ideal. Using fluorescence correlation spectroscopy of dye-labeled FTAC and HFTAC, we demonstrate that neither type of surfactant will bind lipid vesicles. Thus, unlike detergents, fluorinated surfactants do not compromise vesicle integrity even at concentrations far in excess of their critical micelle concentration. We examined the interaction of surfactants with a model MP, DTT, using a variety of spectroscopic techniques. Site-selective labeling of DTT with fluorescent dyes indicates that the surfactants do not interact with DTT uniformly, instead concentrating in the most hydrophobic patches. Circular dichroism measurements suggest that the presence of surfactants does not alter the structure of DTT. However, the cooperativity of the thermal unfolding transition is reduced by the presence of surfactants, especially above the critical micelle concentration (a feature of regular detergents, too). The linear dependence of DTT's enthalpy of unfolding on the surfactant concentration is encouraging for future application of (H)FTACs to determine the stability of the membrane-competent conformations of other MPs. The observed reduction in the efficiency of Förster resonance energy transfer between donor-labeled (H)FTACs and acceptor-labeled DTT upon addition of lipid vesicles indicates that the protein sheds the layer of surfactant during its bilayer insertion. We discuss the advantages of fluorinated surfactants over other types of solubilizing agents, with a specific emphasis on their possible applications in thermodynamic measurements.

A new family of glycodendrimer scaffolds containing 12 and 18 peripheral alpha-d-mannopyranosidic units has been synthesized by Cu(I)-catalyzed [1,3]-dipolar cycloadditions using sulfurated dendritic scaffolds bearing alkyne functionalities and novel TRIS derivatives.

An efficient process for the recovery of palladium from waste printed circuits boards (PCBs) is detailed. Palladium is employed as an electrode material in multi-layer ceramic capacitors (MLCCs). These components can be easily removed from PCBs by desoldering. As palladium is alloyed with silver, its dissolution is readily achieved using dilute nitric acid. As a result, a solution containing palladium along with base metals, mostly copper and iron, is obtained. This solution is then processed through solvent extraction (SX) with a solvent based on N,N'-dimethyl,N,N'-dibutyltetradecylmalonamide (BDMA), a robust extracting molecule previously developed in the frame of the reprocessing of waste nuclear fuel. The volume of effluents generated during the SX sequence is limited: iron scrubbing is operated with a very low aqueous to organic phase volume ratio, no specific metal chelator is required for palladium stripping, and no shift from acidic to basic media is required. Finally, a ca 1 g/L Pd(II) aqueous solution with 99,4% purity is obtained, from which palladium is directly isolated as dichlorodiammine palladium(II) salt (Pd(NH 3 ) 2 Cl 2 ) after precipitation with ammonia. Overall, palladium is quantitatively recovered from the leaching solution, and no palladium was detected in the remaining solid residue. Purity is high, as no contaminating metal could be detected in the final palladium salt. The proposed approach is simple and complementary to existing hydrometallurgical processes dedicated to gold and copper recovery.

We aim to produce emulsions that can act as contrast agents and drug carriers for cancer imaging and therapy. To increase tumor detection and decrease drug side effects, it is desirable to take advantage of the enhanced permeability and retention effect that allows nanoparticles to accumulate in tumor tissues.To do so, the emulsion droplets need to be small enough and stable over time in addition to enhancing image contrast and carrying a drug payload. In the present study, we have investigated the properties and potentiality as theranostic agents of perfluorocarbon emulsions stabilized by a biocompatible fluorinated surfactant called FTAC. To obtain better control of our system, the synthesis of those surfactants was studied and their physico-chemical properties were explored in different configurations such as micelles, in the perfluorocarbon droplet shell and at water/air and water/perfluorocarbon interfaces. The originality of this work lies in the determination of numerous characteristics of emulsions and fluorinated surfactants including surface tension, interfacial tension, critical micelle concentration, adiabatic compressibility, density, size distribution (aging studies), and ultrasonic echogenicity. These characterization studies were conducted using different types of FTAC and several perfluorocarbons (perfluoropentane, perfluorohexane, and perfluorooctyl bromide). We have also shown that a hydrophobic drug could be encapsulated in the FTAC-stabilized perfluorocarbon droplets thanks to triacetin addition. Finally, the perfluorocarbon emulsions were detectable in vitro by a clinical 3 T MRI scanner, equipped with a double frequency 19 F/ 1 H transmit-receive coil.