Synthesis,Structure and Reactivity of Organoindium 1,2-Benzenedithiolates and 2-Amidobenzenethiolates

Organoindium compounds of redox active 1,2-benzenedithiolate and 2-amidobenzenethiolate ligands were synthesized and tested for reactivity against mild oxidants. The reaction of Me₃In and (NCN)InMe₂ [NCN=2,6-bis(dimethylaminomethy)phenyl] with 3,4-toluenedithiol (H₂tdt) at room temperature afforded [MeIn(tdt)(py)]₂ ( 1 ) and (NCN)In(tdt) ( 2 ), respectively. A similar reaction of Me₃In with 2-aminobenzenethiol (H₂abt) in toluene under reflux afforded [MeIn(abt)(py)]₂ ( 3 ). The reaction of (NCN)InCl₂ with one equivalent of Li₂(abt) or two equivalents of Li(Habt) afforded the compounds [(NCN)In(abt)]⋅LiCl(thf)₂ ( 4 ⋅LiCl(thf)₂) and (NCN)In(Habt)₂ ( 5 ), respectively. The X-ray crystal structures of 1 and 3 are similar and show dimeric structures via μ-S-(tdt) and μ-N-(abt) ligands, respectively. Compounds 2 and 4 possess similar monomeric structures and tridentate NCN pincer ligands. DFT computational studies have been used to rationalize the observed solid-state structures and discern the potential reactivity of compounds 1 – 4 against oxidants. The reaction of 1 and 2 with excess iodine resulted in loss of the 3,4-toluenedithiolate ligand and the formation of the oligomeric disulfide [tdt]_n, while 3 and 4 showed no reactivity under similar conditions. This contrasts the reactivity of previously reported organoindium o-amidophenolate complexes which undergo oxidative addition of iodine to afford ligand-centered radical species.     

In-depth investigation of protein adsorption on gold surfaces: correlating the structure and density to the efficiency of the sensing layer

Protein A (PrA), mouse monoclonal anti-IgG antibody (SAb) and deglycosylated avidin (NAV) were adsorbed on gold surfaces to capture the model rabbit IgG and build three immunosensing platforms. The assembling of immunosensors, their specificity, and the receptor accessibility were monitored by polarization modulation reflection-absorption infrared spectroscopy (PM-RAIRS) and quartz crystal microbalance with dissipation measurement (QCM-D) at each step. Combining these two techniques allows us to compare both chemical and structural properties of the sensing layers with the former bringing chemical and semiquantitative information on the grafted protein layers, whereas the latter, in addition to the mass uptake, enables us to take the layer rigidity into account. Grafting of the three capture proteins to the transducer surfaces, covered with appropriate self-assembled monolayers, yielded protein layers with variable properties. NAV formed a dense and rigid molecular layer, likely containing protein aggregates, whereas the amount of PrA was below one monolayer resulting in a flexible layer. The amount of immobilized rabbit IgG was different for the three systems with the densest capture protein layer exhibiting the lowest binding capacity. The accessibility of antibodies on the resulting immunosensors measured by interaction with a secondary antirabbit IgG antibody was found to be closely dependent on their coverage as well as on the rigidity of the protein layer. The overall study provides in-depth information on three of the most common immunosensor recognition interfaces and demonstrates the crucial influence of both structure and density of the protein layer on the efficiency of the molecular recognition phenomena.     

Cationic carbon nanotubes bind to CpG oligodeoxynucleotides and enhance their immunostimulatory properties

Functionalized cationic carbon nanotubes are able to form a stable complex with CpG ODN based on charge interaction and to increase the immunostimulatory activity of CpG motifs.     

Substituent effects on indium-phosphorus bonding in (4-RC6H4S)3In.PR'3 adducts (R = H, Me, F; R' = Et, Cy, Ph): a spectroscopic, structural, and thermal decomposition study

The tris(arylthiolate)indium(III) complexes (4-RC(6)H(4)S)(3)In [R = H (5), Me (6), F (7)] were prepared from the 2:3 reaction of elemental indium and the corresponding aryl disulfide in methanol. Reaction of 5-7 with 2 equiv of the appropriate triorganylphosphine in benzene or toluene resulted in isolation of the indium-phosphine adduct series (4-RC(6)H(4)S)(3)In.PR'(3) [R = H, R' = Et (5a), Cy (5b), Ph (5c); R = Me, R' = Et (6a), Cy (6b), Ph (6c); R = F, R' = Et (7a), Cy (7b), Ph (7c)]. These compounds were characterized via elemental analysis, FT-IR, FT-Raman, solution (1)H, (13)C{(1)H}, (31)P{(1)H}, and (19)F (7a-c) NMR spectroscopy, and X-ray crystallography (5c, 6a, 6c, and 7a). NMR spectra show retention of the In-P bond in benzene-d(6) solution, with phosphine (31)P{(1)H} signals shifted downfield compared to the uncoordinated ligand. The X-ray structures show monomeric 1:1 adduct complexes in all cases. The In-P bond distance [2.5863(5)-2.6493(12) A] is influenced significantly by the phosphine substituents but is unaffected by the substituted phenylthiolate ligand. Relatively low melting points (88-130 degrees C) are observed for all adducts, while high-temperature thermal decomposition is observed for the indium thiolate reactants 5-7. DSC/TGA and EI-MS data show a two-step thermal decomposition process, involving an initial loss of the phosphine moiety followed by loss of thiolate ligand.     

Multi-class pesticide analysis in human hair by gas chromatography tandem (triple quadrupole) mass spectrometry with solid phase microextraction and liquid injection

A method for the simultaneous detection and quantification of 22 pesticides from different chemical classes was developed using solid-phase microextraction (SPME) and gas chromatography tandem (triple quadrupole) mass spectrometry. Pesticides were extracted from 50 mg of pulverized hair with acetonitrile. The extract was submitted to two successive steps of direct immersion-SPME at 30 °C and 90 °C or to a liquid injection without SPME in order to obtain optimized conditions for each of the 22 analytes investigated. Validation parameters were significantly influenced by both the injection mode (SPME vs liquid injection) and the temperature of SPME. Limits of quantification ranged from 0.05 pg mg⁻¹ for trifluralin to 10 pg mg⁻¹ for pentachlorophenol. The application of the validated method to the analysis of samples collected from non-occupationally exposed volunteers demonstrated the presence of pesticides in all the samples tested. Altogether, 13 different analytes were detected at concentration above the limit of quantification.     

Bis-imine primary amine protection of the dialkyltriamine,norspermidine

This Letter details the particular use of salicylaldehyde (2-hydroxybenzaldehyde) for the regiospecific protection of primary amines in a representative polyamine, norspermidine (N-(3-aminopropyl)propane-1,3-diamine) under mild reaction conditions in high yield. The lack of intramolecular hexahydropyrimidine formation allowed for subsequent N²-acylation and N²-alkylation reactions, typical of polyamine synthetic strategies.     

Preferred bonding motif for indium aminoethanethiolate complexes: structural characterization of (Me2NCH2CH2S)2InX/SR (X = Cl, I; R = 4-MeC6H4, 4-MeOC6H4)

The metathesis reaction of InCl3 with Me2NCH2CH2SNa or the redox reaction of indium metal with elemental iodine and the disulfide (Me2NCH2CH2S)2 yield the indium bis(thiolate) complexes (Me2NCH2CH2S)2InX [X = Cl (3) and I (4)], respectively. Compounds 3 and 4 may be further reacted with the appropriate sodium thiolate salts to afford the heteroleptic tris(thiolate) complexes (Me2NCH2CH2S)2InSR [R = 4-MeC6H4 (5), 4-MeOC6H4 (6), and Pr (7)]. Reaction of 2,6-Me2C6H3SNa with 4 affords (Me2NCH2CH2S)2InS(2,6-Me2C6H3) (8), while no reaction is observed with 3, suggesting a greater reactivity for 4. All isolated compounds were characterized by elemental analysis, melting point, and Fourier transform IR and 1H and 13C{1H} NMR spectroscopies. X-ray crystallographic analyses of 3-6 show a bicyclic arrangement and a distorted trigonal-bipyramidal geometry for In in all cases. The two sulfur and one halogen (3 and 4) or three sulfur (5 and 6) atoms occupy equatorial positions, while the nitrogen atoms of the chelating (dimethylamino)ethanethiolate ligands occupy the axial positions. The metric parameters of the (Me2NCH2CH2S)2In framework were found to change minimally upon variation of the X/SR ligand, while the solubility of the corresponding compounds in organic solvents varied greatly. 1H NMR studies in D2O showed that 6 and 7 react slowly with an excess of the tripeptide l-glutathione and that the rate of reaction is affected by the pendant thiolate ligand -SR.     

FTIR, SEM and fractal dimension characterization of lipase B from Candida antarctica immobilized onto titania at selected conditions

Lipase B from Candida Antarctica (also known as Candida antarctica lipase B or CALB) was immobilized onto titanium dioxide (TiO₂) in a buffer-free, bidistilled aqueous medium. The adsorption isotherm was determined by UV-vis analysis of supernatant solution at 280 nm, revealing that in 7 h 98% of the theoretical lipase monolayer on the TiO₂ (with 45.7 m²/g BET area) was achieved.Samples withdrawn from the supernatant immobilization medium were analyzed by Fourier-transform infrared spectroscopy in the 1700-1600 cm⁻¹ range (where the Amide I Proteins band appears) in order to obtain quantitative information on the evolution of the secondary-structure elements of the protein. The analysis performed revealed that lipase conformation suffers only minor changes during its adsorption onto TiO₂. However, water associated to the lipase may interact of several ways with the surface of the hydrated oxide.Characterization of the immobilized biocatalyst (CALB/TiO₂) implied SEM, fractal dimension analysis and FTIR techniques. A proposal of lipase-hydrated oxide interaction is presented.     

BSDE with quadratic growth and unbounded terminal value

In this paper, we study the existence of solution to BSDE with quadratic growth and unbounded terminal value. The main idea consists in using a localization procedure together with a priori bounds.     

Microcalorimetric study of the binding of methotrexate and its metabolites to thymidylate synthase

Direct microcalorimetric measurements allow determination of both the δH and association constant of biological complexes ifK _a value does not exceed 10⁶ M ^?1. For higherK _a values, δH can obviously be determined; this paper describes an original microcalorimetric method that permits determination of such high association constants. This method is based on the analysis of the competitive effect between two ligands having the same binding site in their receptor. As an example, the affinity constant for thymidylate synthase of a novel antifolate, CB 3717. was found to be 1.4 · 10⁷ M ^?1 using methotrexate polyglutamate MTX-G2 (K _a=2.3·10⁵ M ^?1) as competitor.