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Another Molecule (another + molecule)
Selected AbstractsStudies on the oxygen atom transfer reactions of peroxomonosulfate: Catalytic effect of hemiacetalINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2009S. Shailaja The reaction of peroxomonosulfate (PMS) with glycolic acid (GLYCA), an alpha hydroxy acid, in the presence of Ni(II) ions and formaldehyde was studied in the pH range 4.05,5.89 and at 31°C and 38°C. When formaldehyde and Ni(II) ions concentrations are ,5.0 × 10,4 M to 10.0 × 10,4 M, the reaction is second order in PMS concentration. The rate is catalyzed by formaldehyde, and the observed rate equation is (,d[PMS])/dt = (k,2[HCHO][Ni(II)][PMS]2)/{[H+](1+K2[GLYCA])}. The number of PMS decomposed for each mole of formaldehyde (turnover number) is 5,10, and the major reaction product is oxygen gas. The first step of the reaction mechanism is the formation of hemiacetal by the interaction of HCHO with the hydroxyl group of nickel glycolate. The peroxomonosulfate intermediate of the Ni-hemiacetal reacts with another molecule of PMS in the rate-limiting step to give the product. This reaction is similar to the thermal decomposition of PMS catalyzed by Ni(II) ions. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 642,649, 2009 [source] Kinetic evidence for the copper peroxide intermediate with two copper ions in proximityINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2006S. Selvarani The decomposition of caroate (peroxomonosulfate, PMS) is catalyzed by Cu(II) ions even at 5 × 10,5 M in aqueous alkaline solution. The rate is second order in copper(II) ions concentrations and first order in [PMS]. The rate constant values are found to decrease with increase in hydroxide ion concentrations. The turnover number for the reaction is estimated as >1000. The experimental results suggest that the formation of peroxide type intermediate with two copper(II) ions is the rate-determining step. This peroxide intermediate reacts with another molecule of PMS to give the products oxygen, SO and copper ions. The overall entropy of activation is positive with a value of ,20 cals/mol/K. The very high turnover number suggests that Cu(II) ion is one of the best catalysts for the decomposition of caroate ions in alkaline medium. The reaction also represents a system in which metal ion catalyzed decomposition of caroate does not involve radical intermediates. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 439,443, 2006 [source] Osmium-Catalyzed Olefin Dihydroxylation and Aminohydroxylation in the Second Catalytic CycleADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2006Peng Wu Abstract Two catalytic cycles operate in the osmium-catalyzed olefin dihydroxylation and aminohydroxylation. Slow hydrolysis of the Os(VI) monoglycolate (or monoazaglycolate in aminohydroxylation) intermediate often results in the addition of another molecule of olefin thereby shunting the catalysis into the second catalytic cycle. As a result, both enantio- and chemoselectivity are reduced. A series of new chelating ligands were devised, which force the catalysis into the second cycle while maintaining enantiocontrol in the olefin addition step. Excellent catalytic turnover and moderate to good enantioselectivity were achieved. [source] The aggregation-promoting factor of Lactobacillus crispatus M247 and its genetic locusJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2004H. Marcotte Abstract Aims:, Characterization of the aggregation-promoting factor (APF) of the human intestinal isolate Lactobacillus crispatus M247 and its homologous nonaggregating mutant Mu5. Methods and Results:, Western blot analysis revealed that the supernatant of both M247 and Mu5 contains a 28-kDa protein which cross reacts with the antiserum produced against the APF of Lact. gasseri 4B2. The apf genes of M247 and Mu5 strains were identical and were shown to be 672 nucleotides in length and encoding a protein of 223 amino acids with a predicted molecular weight of 24·0 kDa. Conclusion:, Our results shows that the lost of aggregation in Mu5 is not related to a defect in secretion of the APF protein or a mutation in the apf gene. Significance and Impact of the Study:, These results suggest that the mutation in Mu5 may be contained in another molecule involved in aggregation such as a possible receptor for APF. [source] Intermolecular H-bond in propan-2-ol and its solutions with acetonitrileJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2007F. H. Tukhvatullin Abstract Formation of propan-2-ol,acetonitrile dimers is manifested in the Raman spectra as an appearance of a band of aggregates in the high-wavenumber side of the CN vibrational band of liquid acetonitrile (,2 cm,1). The intensity of the band of aggregates changes with a change in the concentration of the mixture (1,0.05 mole fraction). For propan-2-ol we carried out nonempirical calculations of a structure of isolated dimer aggregates. The formation of an intramolecular H-bond between the H and the O atom of the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by -8pt \raise0.5pc\hbox{$\matrix{\hskip-1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip-1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group of length 2.045 Å is possible in the monomer molecule. The CH3 groups of alcohol are not equivalent. In the dimer formation, intramolecular H-bond in the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by -8pt \raise0.5pc\hbox{$\matrix{\hskip-1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip-1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group is preserved. An intermolecular H-bond of length 2.045 Å and energy 15 kJ/mole is formed between the H atom of one molecule and the O atom of another molecule of the OH. The length and energy of the H-bond for the propan-2-ol,acetonitrile dimer formations calculate to 2.27 Å and 12.9 kJ/mole, respectively. The H-bond is formed by ,-electrons of nitrogen. The experimental data and the results of calculations are in good agreement. Copyright © 2007 John Wiley & Sons, Ltd. [source] Parahydrogen-induced polarization in imaging: Subsecond 13C angiographyMAGNETIC RESONANCE IN MEDICINE, Issue 1 2001K. Golman Abstract High nuclear spin polarization of 13C was reached in organic molecules. Enhancements of up to 104, compared to thermal polarization at 1.5 T, were achieved using the parahydrogen-induced polarization technique in combination with a field cycling method. While parahydrogen has no net polarization, it has a high spin order, which is retained when hydrogen is incorporated into another molecule by a chemical reaction. By subjecting this molecule to a sudden change of the external magnetic field, the spin order is transferred into net polarization. A 13C angiogram of an animal was generated in less than a second. Magn Reson Med 46:1,5, 2001. © 2001 Wiley-Liss, Inc. [source] Introduction of a leucine half-zipper engenders multiple high-quality crystals of a recalcitrant tRNA synthetaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2010Min Guo Although Escherichia coli alanyl-tRNA synthetase was among the first tRNA synthetases to be sequenced and extensively studied by functional analysis, it has proved to be recalcitrant to crystallization. This challenge remained even for crystallization of the catalytic fragment. By mutationally introducing three stacked leucines onto the solvent-exposed side of an ,-helix, an engineered catalytic fragment of the synthetase was obtained that yielded multiple high-quality crystals and cocrystals with different ligands. The engineered ,-helix did not form a leucine zipper that interlocked with the same ,-helix from another molecule. Instead, using the created hydrophobic spine, it interacted with other surfaces of the protein as a leucine half-zipper (LHZ) to enhance the crystal lattice interactions. The LHZ made crystal lattice contacts in all crystals of different space groups. These results illustrate the power of introducing an LHZ into helices to facilitate crystallization. The authors propose that the method can be unified with surface-entropy reduction and can be broadly used for protein-surface optimization in crystallization. [source] | ||||||||||