Detection of pathogenic Staphylococcus aureus bacteria by gold based immunosensors

We describe the elaboration of ultra-sensitive immunosensors, to detect the bacterial pathogen Staphylococcus aureus. We utilized commercially available polyclonal anti-S. aureus antibody as receptor. Immunosensors were elaborated by building a self-assembled monolayer (SAM) of thiolamine onto planar gold-coated sensor chips. Then, Protein A was covalently linked to the thiolated SAM using glutaraldehyde as cross-linking agent. After a blocking step by Bovine Serum Albumin (BSA), the antibody was immobilized by affinity to Protein A. This step-by-step construction was monitored by Polarization Modulation Reflection Absorption Infrared Spectroscopy (PM-RAIRS) and Quartz Crystal Microbalance with Dissipation (QCM-D). In a first stage, the parameters of immunosensor elaboration were optimized using a model rabbit IgG. The accessibility of receptors and the homogeneity of their distribution were checked by PM-RAIRS, QCM-D, and by immuno-gold scanning electron microscopy. Then, the specific rabbit anti-S. aureus antibody was immobilized and the resulting sensing layer was applied to the detection of the pathogen target. Independent detection of bacteria immobilized on the sensors by fluorescent imaging allowed validation of the specificity of recognition toward the pathogen as well as a quantitative response of the sensor. Using PM-RAIRS as transducing technique allowed us to enhance sensitivity and reach a very competitive detection level (10⁵ CFU mL^?1).     

Crystallization-driven constitutional changes of dynamic polymers in response to neat/solution conditions

Dynamic polymers (dynamers) based on reversible imine interactions were generated and found to respond to changes in neat/solution environment, thus displaying adaptive behavior through modification of their constitution in order to maximize the stability of their mesoscopic state as a function of conditions.     

Chirality induction and protonation-induced molecular motions in helical molecular strands

The long oligopyridinedicarboxamide strand 9, containing 15 heterocyclic rings has been synthesized and its helical structure determined by X-ray crystallography. It was shown that the shorter analogue 6 displays induced circular dichroism and amplification of induced chirality upon dissolution in an optically active solvent, diethyl-L-tartrate. A novel class of helical foldamers was prepared, strands 14-16, based on two oligopyridine carboxamide segments linked through a L-tartaric acid derived spacer. These tartro strands display internal chirality induction as well as chirality amplification. NMR spectroscopy (on 8 and 9) and circular dichroism (on 16) studies show that the oligopyridine carboxamide strands undergo reversible unfolding/folding upon protonation. The protonation-induced unfolding has been confirmed by X-ray crystallographic determination of the molecular structure of the extended protonated heptameric form 8(+). The molecular-scale mechano-chemical motions of the protonation-induced structural switching consist of a change of the length of the molecule, from 6 angstroms (6, coiled form) to 29 angstroms (8(+), uncoiled form) for the heptamer and from 12.5 angstroms (9, coiled form, X-ray structure) to 57 angstroms (9(+), uncoiled form, from modeling) for the pentadecamer. Similar unfolding/folding motional processes take place in the L-tartro strands 15 and 16 upon protonation/deprotonation, with loss of helicity-induced circular dichroism on unfolding as shown for the protonated form 16(+).     

Modifying the reactivity in the homologation of propane by introducing aryloxide ligands on a silica supported zirconium alkyl system

Grafting the well-defined molecular complexes [(ArO)Zr(CH2tBu)3], , and [(ArO)2Zr(CH2tBu)2], , on SiO2-(700) (ArO=2,6-Ph2C6H3O) gives the corresponding monosiloxy surface complexes [([TRIPLE BOND]SiO)Zr(CH2tBu)2(OAr)] and [([TRIPLE BOND]SiO)Zr(CH2tBu)(OAr)2] as major surface species as evidenced by mass balance analysis, IR and NMR spectroscopies. In both cases, minor cyclometallated species (ca. 20%) are also probably formed during the grafting process. While /SiO2-(700) catalytically transforms propane into its lower and higher homologues, /SiO2-(700) remains inactive. Moreover, the formation of butane as the major higher homologues is consistent with the formation of metallocarbene intermediates in this system in contrast to what was observed for the corresponding homologation reaction on silica supported zirconium hydrides.     

Complexation Properties and Synthesis of 1,2-Bis(2,2'-bipyridinyl)ethylene and 1,2-Bis(2,2' -bipyridinyl)ethane Ligands with Cu(I)

l,2-Bis(2,2'-bipyridinyl)ethylene(1) ligand was synthesized by Wittig-Horner reaction and 1, 2-Bis(2, 2'-bipyridinyl)ethane(2) ligand(which can be obtained via another route ) was prepared by hydrogenation of (1). The formation of complexes of (1) and (2) with copper (I) has been studied. The influence of the different bridge chains (CH =CH, CH2CH2) on complexation is discussed on the basis of 1H NMR spectra. Keywords Dipyridine aldehyde, Dipyridine derivative, Copper complex