Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.     

Dynamics of a surface phase transition as monitored by in situ second harmonic generation

The dynamics of the (2 x 2)-3CO <--> dilute phase transition involving CO adsorbed on Pt(111) microfacets has been monitored in situ in a CO-saturated acidic electrolyte using potential step-second harmonic generation techniques. Apparent time constants derived strictly from the optical data were found to be orders of magnitude slower for the forward process as compared to those of the reverse process. This behavior is consistent with the activated nature of CO electrooxidation, which requires the presence of a neighboring adsorbed oxygenated species, for example, hydroxyl, for the process to ensue.     

Syntheses of seven-membered rings: ruthenium-catalyzed intramolecular [5+2] cycloadditions

The Ru-catalyzed intramolecular [5+2] cycloaddition of cyclopropylenynes is investigated with respect to the regio- and diastereoselectivity as well as the functional group compatibility of the reaction. Evidence for the mechanism as occurring through a ruthenacyclopentene intermediate is elucidated from 1) the study of the diastereoselectivity of the cycloaddition; 2) the effect of variation of substituents on the regioselectivity of cyclopropyl bond cleavage in 1,2-trans- and 1,2-cis-disubstituted cyclopropanes and 3) examples that clearly do not involve ruthenacyclohexene as intermediates as products still incorporate the cyclopropyl moiety. The scope and limitations of the Ru-catalyzed cycloaddition are discussed and compared with the Rh-catalyzed reaction. The potential power of this methodology towards natural product total synthesis is demonstrated by the formation of several polycyclic systems with the chosen reaction conditions and readily available cyclopropylenyne substrates.     

Ultrasensitive single-cell proteomics workflow identifies >1000 protein groups per mammalian cell

We report on the combination of nanodroplet sample preparation, ultra-low-flow nanoLC, high-field asymmetric ion mobility spectrometry (FAIMS), and the latest-generation Orbitrap Eclipse Tribrid mass spectrometer for greatly improved single-cell proteome profiling. FAIMS effectively filtered out singly charged ions for more effective MS analysis of multiply charged peptides, resulting in an average of 1056 protein groups identified from single HeLa cells without MS1-level feature matching. This is 2.3 times more identifications than without FAIMS and a far greater level of proteome coverage for single mammalian cells than has been previously reported for a label-free study. Differential analysis of single microdissected motor neurons and interneurons from human spinal tissue indicated a similar level of proteome coverage, and the two subpopulations of cells were readily differentiated based on single-cell label-free quantification.

The combination of nanodroplet sample preparation, ultra-low-flow nanoLC, high-field asymmetric ion mobility spectrometry (FAIMS) and latest-generation mass spectrometry instrumentation provides dramatically improved single-cell proteome profiling.     

Heats of adsorption of linear CO species adsorbed on the Au degrees and Ti+delta sites of a 1% Au/TiO2 catalyst using in situ FTIR spectroscopy under adsorption equilibrium

The heats of adsorption of two linear CO species adsorbed on the Au degrees particles (denoted L(Au degrees)) and on the Ti(+delta) sites (denoted L(Ti+delta)) of a 1% Au/TiO(2) catalyst are determined as the function of their respective coverage by using the AEIR procedure (adsorption equilibrium infrared spectroscopy) previously developed. Mainly, the evolutions of the IR band area of each adsorbed species (2184 cm(-1) for L(Ti+delta) and at 2110 cm(-1) for L(Au degrees)) as a function of the adsorption temperature T(a), at a constant CO adsorption pressure P(CO), provide the evolutions of the coverages theta(LTi+delta) and theta(LAu degrees ) of each adsorbed CO species with T(a) in isobar conditions that give the individual heats of adsorption. It is shown that they linearly vary from 74 to 47 kJ/mol for L(Au degrees ) and from 50 to 40 kJ/mol for L(Ti+delta) at coverages 0 and 1, respectively. These values are consistent with literature data on model Au particles and TiO(2). In particular, it is shown that the mathematical formalism supporting the AEIR procedure can be applied to literature data on Au-containing solids (single crystals and model particles).     

Nouveaux heterocycles tricycliques synthese de derives de l'aza-2 pyrrolo[1,2-a]indole

The synthesis of aza-2 pyrrolo[1,2-a]indole derivatives was achieved by a 1,3-dipolar cycloaddition reaction of dimethylacetylenedicarboxylate with a mesoionic ion.     

Long-range magnetic ordering in iron jarosites prepared by redox-based hydrothermal methods

The iron jarosites, plumbojarosite, Pb0.5Fe3(OH)6(SO4)2, argentojarosite, AgFe3(OH)6(SO4)2, and thallium jarosite, TlFe3(OH)6(SO4)2, along with the selenate-capped jarosite analogues of potassium, KFe3(OH)6(SeO4)2, and rubidium, RbFe3(OH)6(SeO4)2, have been prepared in their analytically pure forms by employing redox-based hydrothermal methods. The crystal structures of these materials have been determined, and all are found to be essentially isostructrual including Pb0.5Fe3(OH)6(SO4)2, which is distinct from the structure reported for naturally mined samples. All iron jarosites show long-range order (LRO), signified by a sharp transition temperature, T(N), which falls in the narrow temperature range of 61.4 +/- 5 K. The mechanism responsible for this ordering has been established by examining magnetostructural correlations for the jarosites possessing various interlayer cation and capping groups. We show that all magnetic properties of jarosites, including LRO, find their origin in the basic magnetic unit, the intralayer Fe3(mu-OH)3 triangle. Field-dependent magnetization experiments are consistent with the antiferromagnetic stacking of an out of plane moment developed from spin canting within Fe3(mu-OH)3 triangles. Together with the previously reported AFe3(OH)6(SO4)2 (A = Na+, K+, Rb+ and NH4+) jarosites, these compounds provide a framework for probing magnetic ordering in a spin frustrated lattice of the largest series of isoelectronic and isostructural kagomé systems yet discovered.     

Aquaporin-11: A channel protein lacking apparent transport function expressed in brain

Background  

The aquaporins are a family of integral membrane proteins composed of two subfamilies: the orthodox aquaporins, which transport only water, and the aquaglyceroporins, which transport glycerol, urea, or other small solutes. Two recently described aquaporins, numbers 11 and 12, appear to be more distantly related to the other mammalian aquaporins and aquaglyceroporins.     

Substituent control of hydrogen bonding in palladium(II)-pyrazole complexes

Inter- and intramolecular hydrogen bonding of an N-H group in pyrazole complexes was studied using ligands with two different groups at pyrazole C-3 and C-5. At C-5, groups such as methyl, i-propyl, phenyl, or tert-butyl were present. At C-3, side chains L-CH(2)- and L-CH(2)CH(2)- (L = thioether or phosphine) ensured formation of chelates to a cis-dichloropalladium(II) fragment through side-chain atom L and the pyrazole nitrogen closest to the side chain. The significance of the ligands is that by placing a ligating side chain on a ring carbon (C-3), rather than on a ring nitrogen, the ring nitrogen not bound to the metal and its attached proton are available for hydrogen bonding. As desired, seven chelate complexes examined by X-ray diffraction all showed intramolecular hydrogen bonding between the pyrazole N-H and a chloride ligand in the cis position. In addition, however, intermolecular hydrogen bonding could be controlled by the substituent at C-5: complexes with either a methyl at C-5 or no substituent there showed significant intermolecular hydrogen bonding interactions, which were completely avoided by placing a tert-butyl group at C-5. The acidity of two complexes in acetonitrile solutions was estimated to be closer to that of pyridinium ion than those of imidazolium or triethylammonium ions.