Dicubyl disulfide

Dicubyl disulfide (1) has been prepared in six steps from commercially available dimethyl-1,4-cubanedicarboxylate in 47% overall yield. In the final step, the previously unknown cubanethiol 2 was oxidized to disulfide 1. X-ray crystallography for 1 reveals the shortest tetragonal C-S bond on record (1.771 A). In contrast to previous generalizations, density functional theory calculations predict a low S-S rotation barrier similar to that for t-BuSSBu-t. Low-temperature (13)C NMR (600 MHz) confirms the prediction.     

Reaction of cycloheptatrienes with sulphur dioxide: Formation of benzenealkanesulphinic acids

Cycloheptatriene, 7-methylcycloheptatriene, and 7-phenylcycloeptatriene in liquid SO₂ convert in about 3 d at 18°C to benzenemethanesulphinic acid, 1-benzeneethanesulphinic acid, and dibenzenemethanesulphinic acid respectively; benzonorcaradiene gives in 2 h the α- and β-naphtalenemethanesulphinic acids.     

Partial-wave analysis of backwardly produced three-pion systems in K−p interactions at 4.2 GeV/c

We report on the results of a partial-wave analysis of the 3π system produced by baryon exchange in the reaction K^?p→Σ^?π⁺π⁺π^? at 4.2 GeV/c. We confirm the existence of an enhancement in the 1⁺S(?π) wave as previously established from a Dalitz plot analysis of the same data. The phase variation of this wave is found to be consistent with that expected for a resonance and thus the enhancement is identified with A₁ production. No clear signal for this state is found in either the reaction K^?p→Σ⁺π⁺π⁺π^?π^? or K^?p→Λπ⁺π^?π⁰. We also find production via baryon exchange of the A₂ in all three reactions and the ω and $\text{ω}{}^1$ (1975) in the third reaction.     

Ni-based catalysts obtained from perovskites oxides for ethanol steam reforming

Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose, La_1-xMg_xAl_1-yNi_yO₃ (x = 0.1; y= 0, 0.1, 0.2, 0.3) perovskites were synthetized by the citrate method. Ni segregation is evident for a substitution level higher than 0.2. The segregation of Ni as NiO generated species interacts with different metal-support after the reduction step. The y= 0.1 catalyst presents the highest H₂ yield value about 85% during reaction time, with low mean values of CH₄ and CO selectivities of 3.4% and 11%, respectively and a low carbon formation. The better performance of y= 0.1 catalyst could be attributed to the minor proportion of segregated phases, thus a controlled expulsion of Ni is successfully reached.     

4-Hydroxy-3,5-pyridinedicarboxylic Acids: Synthesis,Complexation Properties Towards Fe(III), Al(III), Cu(II), Zn(II), Human Serum Albumin,and Cellular Toxicity

4-hydroxy-3,5-pyridinedicarboxylic acid (DQ58) and 4-hydroxy-1-methyl-3,5-pyridinedicarboxylic acid (DQ71508) have been synthesized, and their Fe(III), Al(III), Cu(II), and Zn(II) coordination properties have been studied by potentiometry, UV–Vis spectroscopy (in the case of Fe(III), Al(III), Cu(II)), ¹H-NMR (for Al(III)) and EPR (for Cu(II)). The thermodynamic results were used to model the extent of the toxic metal ions decorporation (Fe(III) or Al(III)) in the presence of the essential metal ions (Cu(II) or Zn(II)). DQ58 and DQ71508 were demonstrated to interact with human serum albumin (HSA), which is assumed to be the main serum transporter of the chelators, and binding constants have been obtained by ultrafiltration. IC₅₀ values of 5.185 × 10^?3 and 1.033 × 10^?3 mol·L^?1 were collected after 24 and 48 h of treatment with DQ71508 towards human embryonic kidney HEK-293 cells, demonstrating the relatively low cytotoxicity of this compound. According to these results, both DQ58 and DQ71508 seem to be potential candidates for Fe chelation therapy, and DQ58 is a better Fe(III) chelator than DQ71508.     

Adsorption of N,N-dimethylamine from aqueous solutions by a metal organic framework,MOF – 235

Water-resistant MOF-235 was used to adsorb N,N-dimethylamine (DMA) from aqueous solutions. It was synthesized from terephthalic acid and FeCl₃.6H₂O under air-free conditions and characterized by its crystalline structure, functional groups and temperature resistance. The kinetic data results were best adjusted to the pseudo-second order model (R²>0.963). The best-fit isotherm, Langmuir model, suggested the adsorption of DMA is localized on homogenously distributed active sites on the surface. This fit was confirmed by the value of β?=?1 on the Redlich-Peterson model. Our study suggests that the manipulation of novel materials such as MOF-235 promises new avenues for water treatment solutions.

Schematic structure of MOF-235 and its application as adsorbent.     

Quantitative analysis of triacylglycerol regioisomers in fats and oils using reversed-phase high-performance liquid chromatography and atmospheric pressure chemical ionization mass spectrometry

Positional distribution of fatty acyl chains of triacylglycerols (TGs) in vegetable oils and fats (palm oil, cocoa butter) and animal fats (beef, pork and chicken fats) was examined by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to atmospheric pressure chemical ionization using a quadrupole mass spectrometer. Quantification of regioisomers was achieved for TGs containing two different fatty acyl chains (palmitic (P), stearic (S), oleic (O), and/or linoleic (L)). For seven pairs of 'AAB/ABA'-type TGs, namely PPS/PSP, PPO/POP, SSO/SOS, POO/OPO, SOO/OSO, PPL/PLP and LLS/LSL, calibration curves were established on the basis of the difference in relative abundances of the fragment ions produced by preferred losses of the fatty acid from the 1/3-position compared to the 2-position. In practice the positional isomers AAB and ABA yield mass spectra showing a significant difference in relative abundance ratios of the ions AA(+) to AB(+). Statistical analysis of the validation data obtained from analysis of TG standards and spiked oils showed that, under repeatability conditions, least-squares regression can be used to establish calibration curves for all pairs. The regression models show linear behavior that allow the determination of the proportion of each regioisomer in an AAB/ABA pair, within a working range from 10 to 1000 microg/mL and a 95% confidence interval of +/-3% for three replicates.     

Triple channel sensing of Pb(II) ions by a simple multiresponsive ferrocene receptor having a 1-deazapurine backbone

A new redox, chromogenic, and fluorescent chemosensor molecule based on a deazapurine ring selectively senses aqueous Pb2+ in acetonitrile over other metal ions examined: redox shift (DeltaE1/2 = 0.15 V of the Fe(II)/Fe(III) redox couple), the colorless to orange color change, and an emission change of 620-fold, with an unprecedented detection limit of 2.7 microg L-1. The signal transduction occurs via a reversible CHEF with this inherent quenching metal ion.     

A nanoparticulate drug-delivery system for rivastigmine: physico-chemical and in vitro biological characterization

The preparation and characterization of surface-PEGylated polymeric nanoparticles are described. These systems were obtained by UV irradiation of PHM and PHM-PEG(2000) as an inverse microemulsion, using an aqueous solution of the PHM/PHM-PEG(2000) copolymer mixture as the internal phase and triacetin saturated with water as the external phase, and characterized by dimensional analysis, zeta-potential measurements and XPS. in vitro biological tests demonstrated their cell compatibility and their ability to escape from phagocytosis. Rivastigmine was encapsulated into the nanoparticle structure and drug-release profiles from loaded samples were investigated in PBS at pH = 7.4 and human plasma.     

Hydrogels for potential colon drug release by thiol-ene conjugate addition of a new inulin derivative

Inulin was chosen as a starting polymer for biocompatible, pH-sensitive and biodegradable hydrogels. Three INUDVSA-TT hydrogels were obtained by crosslinking inulin derivatives with trimethylolpropane tris(3-mercaptopropionate) under varying conditions. The resulting hydrogels were cell compatible, as demonstrated by MTS and trypan blue exclusion assays acting on Caco-2 cells, and were biodegraded by inulinase and esterase, thus suggesting their use as colonic drug delivery systems. 2-Methoxyestradiol, an anti-cancer drug, was soaked in INUDVSA-TT hydrogels and its in vitro release and apoptotic effect on Caco-2 cells were evaluated.