On-target sample preparation of 4-sulfophenyl isothiocyanate-derivatized peptides using AnchorChip Targets

De novo sequencing of tryptic peptides by post source decay (PSD) or collision induced dissociation (CID) analysis using MALDI TOF-TOF instruments is due to the easy interpretation facilitated by the introduction of N-terminal sulfonated derivatives. Recently, a stable and cheap reagent, 4-sulfophenyl isothiocyanate (SPITC), has been successfully used for N-terminal derivatization. Previously described methods have always used desalting and concentration by reverse-phase chromatography prior to mass spectrometric analysis. Here we present an on-target sample preparation method based on AnchorChip target technology. The method was optimized for reduction of by-products and sensitivity with SPITC-derivatized tryptic BSA peptides, and successfully applied to protein identification from silver-stained two-dimensional electrophoretic gels of fish liver extracts. The method is simple and sensitive and allowed protein identification based on de novo sequencing and BLAST search from species with limited sequence information.     

Thermal behaviour study of some sol-gel TiO2 based materials

Among the great number of sol-gel materials prepared, TiO₂ holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light. This work has studied some un-doped and Pd-doped sol-gel TiO₂ nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous TiO₂ matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between the synthesis conditions and the properties of titania nanosized materials, such as thermal stability, phase composition, crystallinity, morphology and size of particles, and the influence of dopant was investigated. The influence of Pd on TiO₂ crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.     

Palladium nanoparticles supported on an organic-inorganic fluorinated hybrid material. Application to microwave-based heck reaction

Phosphine-free palladium nanoparticles were embedded in a fluorous organic-inorganic hybrid material 6b prepared by the sol-gel process. The use of Pdn.6b in the Heck coupling reaction under microwave irradiation has been investigated. Recycling studies have shown that the catalyst can be readily recovered and reused several times without significant loss of activity. Reactions and recovery of the solid-supported palladium catalyst system can be carried out in the presence of air, without any particular precaution.     

Pesticide analysis by MEKC on a microchip with hydrodynamic injection from organic extract

An integrated microchip for monitoring carbamate pesticides in environmental water using continuous flow chemical processes is under development, i. e., the integration of hydrolysis, azo-derivatization, liquid-liquid extraction, electrophoretic separation, and quantification. The separation of the derivatives of four carbamate pesticides (carbaryl, carbofuran, propoxur, and bendiocarb) extracted in the continuous flow of a 1-butanol phase was studied in a silica microchip using micellar EKC. A baseline separation of four pesticide derivatives was achieved on a silica chip using hydrodynamic injection with electroosmotic gating. Detection using a thermal lens microscope showed good linearity in the concentration range of 10(-6 )-10(-5 )M with an LOD of 5 x 10(-7) M, which is superior to that of conventional CE with UV absorption detection at a level of 10(-4) M.     

Selective partial reduction of quinolines: Hydrosilylation vs. transfer hydrogenation

Two mild and versatile catalytic routes give regioselective hydrogenation of the heterocyclic ring of quinoline derivatives avoiding the high pressures of hydrogen required in the conventional hydrogenation route. Hydrosilylation using H₃SiPh and catalyzed by [Rh(nbd)(PPh₃)₂]PF₆ at room temperature gives dihydroquinoline, a product not obtainable via direct hydrogenation. Hydrosilylation of the CN bond of PhCHNPh is also observed under these conditions while PhCHCHPh is unreactive. Initial in situ disproportionation of phenylsilane to H₂SiPh₂ and SiH₄, catalyzed by the same catalyst, was required for substrate reduction, as SiH₄ proved to be the active reductant. No N-silyl intermediates were ever observed, hydrolysis presumably occurring in situ. This disproportionation reaction is of potential use in gaining access to silane (SiH₄), a material otherwise not readily available. In a separate approach, transfer hydrogenation from isopropanol using [Ir(cod)(NHC)PPh₃]BF₄ (NHC = 1-neopentyl-4-n-butyl triazole-5-ylidene) as catalyst exclusively produces the tetrahydro product.     

Imidazolium carboxylates as versatile and selective N-heterocyclic carbene transfer agents: synthesis, mechanism, and applications

N,N'-Disubstituted imidazolium carboxylates, readily synthetically available, isolable, air- and water-stable reagents, efficiently transfer N-heterocyclic carbene (NHC) groups to Rh, Ir, Ru, Pt, and Pd, to give novel NHC complexes, e.g., [Pd(NHC)3OAc]OAc and [Pt(NHC)3Cl]Cl (NHC = 1,3-dimethyl imidazol-2-ylidene). The NHC esters are also effective. Tuning the reaction conditions for NHC transfer can give either mono- or bis-NHCs, or bis- and tris-NHCs. A net N to C rearrangement of the N-alkyl imidazole complex to the corresponding NHC complex was seen with (MeO)2CO (DMC). DFT calculations identify the steps needed to form the carboxylate from imidazole and DMC: SN2 methyl transfer from DMC to imidazole, followed by proton transfer from the imidazolium CH to the carboxylate counterion, produces the free NHC H-bonded to MeOH with a weakly associated CO2. The nucleophilic NHC attacks CO2 to form NHC-CO2. NHC transfer to the metal with loss of CO2 has been calculated for Rh(cod)Cl. A proposed two-cis-site reactivity model rationalizes the experimental data: two such vacant sites at the metal are needed to allow coordination of the NHC-CO2 carboxylate and subsequent CC cleavage with NHC transfer. Partial cod decoordination or chloride loss is thus required for Rh(cod)Cl. Chloride dissociation, calculated to be easier in polar solvent, is confirmed experimentally from the retarding effect of excess chloride.     

On the Integrability of Generalized Almost para-Norden and para-Hermitian Structures

In this paper, we investigate the \(\nabla \) integrability of generalized almost para-Norden/para-Hermitian structures on the big-tangent bundle of smooth manifolds endowed with some additional structures. We also study their invariance under a B-field transformation of the first and second types, respectively. Finally, we obtain a relation between \(\nabla \) integrability and the standard Courant integrability of generalized almost para-Norden or para-Hermitian structures, and we give some conditions for the equivalence of these kinds of integrability, in some particular cases.     

Sol–gel doped TiO<Subscript>2</Subscript> nanomaterials: a comparative study

Among the great number of sol–gel prepared nanomaterials, TiO₂ has attracted significant interest due to its high photocatalytic activity, excellent functionality, thermal stability and non-toxicity. The photocatalytic degradation of pollutants using un-doped and doped TiO₂ nanopowders or thin films is very attractive for applications in environmental protection, as a possible solution for water purification. The present work describes a comparative structural and chemical study of un-doped TiO₂ and the corresponding S- and Ag-doped materials. The photocatalytic activity was established by testing the degradation of organic chloride compounds from aqueous solutions. Sol–gel Ag-doped TiO₂ coatings, prepared by co-gelation and sol–gel Ag-doped TiO₂ coatings obtained from nanopowders were also compared. Their structural evolution and crystallization behaviour (lattice parameters, crystallite sizes, internal strains) with thermal treatment were followed by thermal analysis, X-ray diffraction, transmission electron microscopy, atomic force microscopy and specific surface areas measurements. X-ray photoelectron spectroscopy analyses were performed to characterize the surface composition and S or Ag speciation, which was used to interpret the catalytic data.     

An FT-IR study of sarcoplasmic reticulum solubilization by triton X-100

Low concentrations of the non-ionic detergent Triton X-100 increase the activity of sarcoplasmic reticulum Ca⁺⁺-ATPase without major changes in protein conformation, according to FT-IR spectroscopy in H₂O and D₂O. At higher surfactant concentrations the enzyme activity is inhibited, while changes in protein conformation are seen: The proportion of unordered structure increases at the expenses of-turns and parallel-sheet.