The hydrodesulfurization activity and characterization of cobalt Chevrel phase sulfides

Hydrodesulfurization activity of cobalt Chevrel phase sulfide catalysts has been investigated in a fixed-bed flow reactor. Single phase cobalt Chevrel phase sulfides exhibited catalytic activity for hydrodesulfurization. Supported cobalt Chevrel phase sulfides catalysts indicated much higher hydrodesulfurization activity and even higher than commercial CoMoS/Al₂O₃ catalysts. The existence of Mo₆S₈ and the reduced oxidation state of Mo in the cobalt Chevrel phase sulfides has been observed by XRD, LRS, and XPS. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inter- and intramolecular N-terminal methyl–side chain interactions in N-acetyl-L-glutamic acid oligomeric benzyl ester solutions. 1H NMR study

Oligomeric N-acetyl-L-glutamic acid benzyl esters with exact residue number (2, 3 or 4) have been synthesized by a stepwise procedure. The aggregational behavior of these oligomeric molecules in dioxane and benzene has been investigated by use of ¹H NMR. In particular, the concentration dependence of the ¹H signals for the N-terminal CH₃ protons has provided evidence that an intermolecular CH₃···? interaction plays a critical role in the formation of aggregates and that an intramolecular CH₃···? interaction occurs in the monomolecular state.     

Molecular dynamics simulation of clustered DNA damage sites containing 8-oxoguanine and abasic site

Clustered DNA damage sites induced by ionizing radiation have been suggested to have serious consequences to organisms, such as cancer, due to their reduced probability to be repaired by the enzymatic repair machinery of the cell. Although experimental results have revealed that clustered DNA damage sites effectively retard the efficient function of repair enzymes, it remains unclear as to what particular factors influence this retardation. In this study, approaches based on molecular dynamics (MD) simulation have been applied to examine conformational changes and energetic properties of DNA molecules containing clustered damage sites consisting of two lesioned sites, namely 7,8-dihydro-8-oxoguanine (8-oxoG) and apurinic/apyrimidinic (AP) site, located within a few base pairs of each other. After 1 ns of MD simulation, one of the six DNA molecules containing a clustered damage site develops specific characteristic features: sharp bending at the lesioned site and weakening or complete loss of electrostatic interaction energy between 8-oxoG and bases located on the complementary strand. From these results it is suggested that these changes would make it difficult for the repair enzyme to bind to the lesions within the clustered damage site and thereby result in a reduction of its repair capacity.     

Formation of isoindoline derivatives from o-bromoacetylbenzophenones

o-Dibromoacetylbenzophenone, 2 or o-bromoacetylbenzophenone 3 reacted with aqueous ammonia to produce 3-phenylisoindolin-1-one 5. The reaction of 3 with methylamine afforded 3-hydroxy-2-methyl-3-phenyl-isoindolin-1-one 4 and 2-methyl-3-phenylisoindolin-1-one 5. Whereas from 2 with methylamine only 5 was obtained.     

Palladium-catalyzed coupling reaction of propargylic oxiranes with arylboronic acids in aqueous media

A novel type of coupling reaction has been developed by the palladium-catalyzed reaction of propargylic oxiranes with arylboronic acids, in which anti-substituted 4-aryl-2,3-allenols were produced in a highly diastereoselective manner. A chiral-substituted allene has been synthesized from the reaction of a chiral propargylic oxirane without loss of the chirality.     

Phase equilibrium in the system Y-Fe-O at 1100°C

Phase equilibrium was established in the Y-Fe-O system at 1100°C by varying the oxygen partial pressure from −log(P_O2/atm)=15.00 to 0, allowing construction of a phase diagram at 1100°C for the system Y₂O₃-Fe-Fe₂O₃. In the system, two ternary compounds, YFeO₃ and Y₃Fe₅O₁₂, were stable and had nonstoichiometric composition, whereas YFe₂O₄ was not found to be stable. The present result was different from that of previous studies at 1200°C, in which YFe₂O₄ was stable, along with the above two ternary compounds. Lattice constants of YFeO₃ and Y₃Fe₅O₁₂, prepared in air by a quenching method, were determined and compared with previous values, and showed close agreement. The standard Gibbs energy changes of the reactions in the Fe-O system, Fe+1/2O₂=FeO, 3FeO+1/2O₂=Fe₃O₄, and 2/3Fe₃O₄+1/6O₂=Fe₂O₃, were determined, and the obtained values were compared with the previous values. The standard Gibbs energy changes of the reactions, Fe+1/2Y₂O₃+3/4O₂=YFeO₃, and 3YFeO₃+2/3Fe₃O₄+1/6O₂=Y₃Fe₅O₁₂, were calculated from the oxygen partial pressures in equilibrium.     

The Effects of Cyclodextrins on Autoinducer Activities of Quorum Sensing in Pseudomonas aeruginosa

Inclusion complex formation between cyclodextrin and autoinducer of gram negative bacteria in aqueous solution was investigated by 1D ¹H-NMR and ROESY spectra. An inhibitioneffect was observed on autoinducer activities of quorum sensing in Pseudomonas aeruginosa by adding cyclodextrins to the bacterial culture medium.     

Removal of proteins from natural rubber with urea

Removal of proteins from natural rubber was achieved by incubation of the rubber latex with urea in the presence of a surfactant to prevent the latex‐allergy caused with thin film products. Temperature, pH and time for the incubation were investigated to remove the proteins effectively, in which nitrogen content of the rubber was reduced to 0.02 from 0.38 wt% under the optimum condition. To remove further the proteins, deproteinization of natural rubber was made by incubation of the latex with proteolytic enzyme in the presence of a surfactant followed by incubation with urea. Amount of allergen decreased through the procedure to less than 0.7 μg/ml, which is a small amount of allergen compared to that for the commercial, deproteinized natural rubber. Copyright © 2004 John Wiley & Sons, Ltd.     

Generation and cycloaddition of polymer-supported azomethine ylide via a 1,2-silatropic shift of alpha-silylimines: traceless synthesis of pyrrolidine derivatives

The 1,3-dipolar cycloaddition of polymer-supported azomethine ylides to dipolarophiles gave pyrrolidine derivatives in good yields. The azomethine ylides were generated from resin-bound alpha-silylimines via a 1,2-silatropic shift. The features of this method are not only a traceless synthesis but also a unique solid-phase route to pyrrolidines with extensive diversity. [reaction: see text]