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Other Acids (other + acid)
Selected AbstractsPrevention of Manganese Precipitation during the Continuous Selective Partial Oxidation of Methyl Aromatics with Molecular Oxygen in Supercritical WaterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Joan Fraga-Dubreuil Abstract Presented here is an investigation of the activity and recovery of the homogeneous manganese/bromide catalyst during the continuous flow oxidation of o -xylene, as model substrate, with molecular oxygen (O2) in supercritical water (scH2O). Two strategies are discussed for preventing catalyst precipitation, mainly in the form of oxides such as manganese(IV) oxide, The first strategy involves varying the manganese:bromide ratio using either manganese(II) acetate or manganese(II) bromide in the presence of hydrobromic and other acids. The results show that the effect of acidity and bromide concentration plays an important role in preventing the manganese/bromide catalyst from precipitating. The second strategy uses aromatic carboxylic acids in combination with the manganese/bromide catalyst, particularly benzoic acid, which improves the catalyst recovery dramatically over a certain range of acid concentrations. Our studies show how the presence of an organic acid and/or its precursors is important in stabilising the catalyst. Our results are rationalised on the basis of a tentative reaction mechanism. [source] Degradation of malic acid in wine by immobilized Issatchenkia orientalis cells with oriental oak charcoal and alginateLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2010S.K. Hong Abstract Aims:, To test degradation of malic acid content in wine by immobilized Issatchenkia orientalis KMBL 5774 cells recently isolated from Korean wine pomace as a malic acid-degrading yeast. Methods and Results:,I. orientalis KMBL 5774 cells were immobilized using a mixture of oriental oak (Quercus variabilis) charcoal with sodium alginate. When the immobilized yeast cells were observed on a scanning electron microscope, cells were efficiently immobilized on the surface area of the charcoal. A Korean wine containing a high level of malic acid was treated with the immobilized yeast cells. The HPLC analysis of the malic acid content in the treated wine showed the malic acid content was reduced to 0·75 mg ml,1 after treatment from the original content of 8·96 mg ml,1, representing 91·6% of the malic acid was degraded during the treatment. Conclusions:, The immobilization of the malic acid-degrading yeasts with oriental oak charcoal and sodium alginate is useful for degradation of malic acid in wines containing a high level of malic acid with no significant increase in other acids. Significance and Impact of the study:, Malic acid is sometimes detrimental to the quality of wines when present at high concentrations in some varieties. The immobilized I. orientalis KMBL5774 cells appear to be a promising candidate in view of developing biotechnological methods for reduction of malic acid contents in wine. [source] Oral and vaginal epithelial cell anti- Candida activity is acid labile and does not require live epithelial cellsMOLECULAR ORAL MICROBIOLOGY, Issue 4 2005J. Yano Background:,Candida albicans is the causative agent of oral and vaginal candidiasis. Innate host defenses against C. albicans are important against each infection. Among these are oral and vaginal epithelial cells that have anti- Candida activity. The mechanism of action includes a requirement for cell contact with no role for soluble factors, and a putative role for carbohydrates based on the sensitivity of the activity to periodic acid. Methods:, Periodic acid treatment of epithelial cells as well as the property of partial resistance of antifungal activity to fixation was used to further dissect the mechanism of action. Results:, The results herein effectively now challenge a role for carbohydrates alone. Firstly, the putative carbohydrate(s) released into supernatants of periodic acid-treated epithelial cells could not compete with fresh epithelial cells for activity, and equivalent abrogation of activity was observed by periodic acid-treated cells irrespective of the amount of carbohydrate released. Instead, the similar abrogation of activity following treatment with other acids or when cocultured under acidic conditions suggests that the activity is acid-labile. Finally, while activity requires intact epithelial cells, it does not require live cells; activity was minimally affected by fixing epithelial cells prior to coculture where the majority of cells remained impermeable to Trypan blue but were defined as non,viable by positive nuclear staining with propidium iodide. Conclusion:, These results suggest that antifungal activity is dependent on contact by intact, but not necessarily live, epithelial cells through an acid-labile mechanism. [source] Effect of acids on in situ polyaniline film formationPOLYMER INTERNATIONAL, Issue 8 2004Prof MM Ayad Abstract The chemical oxidation of aniline with ammonium persulfate (APS) to form polyaniline (PANI) films has been studied in different aqueous acid media such as sulfuric, nitric, phosphoric and acetic acids. A comparison was made between the yields of PANI film deposition during the polymerization from these media with the corresponding one obtained previously from aqueous HCl solution. The degradation of the formed PANI films at the beginning of polymerization obtained at the higher concentrations of HCl is absent when the other acids under consideration were used. The effect of acid concentration on the yield and growth rate of the PANI film was studied. The variation in the yield and growth rate of the polymer films at different acid concentrations was explained on the basis of the electrostatic repulsion and the screening effects. Copyright © 2004 Society of Chemical Industry [source] Lipid analysis of the sex pheromone gland of the moth Heliothis virescensARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2005S.P. Foster Abstract The sex pheromone gland of female Heliothis virescens was analyzed for fatty acid and lipid content. Base methanolysis of the gland showed a large amount of methyl (Z)-11-hexadecenoate (Z11-16:Acyl), the fatty acyl analog of the major pheromone component, (Z)-11-hexadecenal, as well as a small amount of methyl (Z)-11-octadecenoate. Methyl esters of various common fatty acids were also observed. HPTLC analysis of the glandular lipids revealed large quantities of triacylglycerols (TGs), and lesser amounts of 1,2-diacylglycerols (1,2-DGs), 2- monoacylglycerols (2-MGs), phosphatidyl ethanolamines, and phosphatidyl cholines. The greatest amount of Z11-16:Acyl in these lipids was in the TGs, with lesser amounts in the two phospholipid classes and only trace amounts in the other neutral lipids. The glands of females at various ages and photoperiodic times were extracted, fractionated into neutral and polar fractions by silica SPE, and fatty acid titers in these fractions determined. All fatty acids, but notably Z11-16:Acyl, showed significant total and neutral lipid fraction peaks at mid scotophase for 2-day-old females; a less dramatic, but significant, Z11-16:Acyl peak in the polar fraction was also observed. However, only a relatively small proportion (<50%) of this acid was recovered from the silica at all times. This "non-recoverable" Z11-16:Acyl showed a dramatic and significant peak at mid scotophase for 2-day females, corresponding roughly with maximal pheromone titer. All other acids in the gland were recovered in high proportions, and their respective "non-recoverable" titers were not different at any of the times analyzed. Based on previous work, this non-recoverable Z11-16:Acyl is likely the CoA ester. Therefore, it appears that the pheromone gland of H. virescens maintains pools of Z11-16:Acyl in both CoA ester and TG forms, which are available for biosynthesis of pheromone. These pools are greatest during maximal pheromone production when the biosynthetic enzymes, possibly the fatty acid reductase, are unable to utilize rapidly enough the quantities of Z11-16:Acyl biosynthesized. Arch. Insect Biochem. Physiol. 59:80,90, 2005. © 2005 Wiley-Liss, Inc. [source] Application of mixtures of tartaric acid derivatives in resolution via supercritical fluid extractionCHIRALITY, Issue 6 2007Ildikó Kmecz Abstract Racemic N -methylamphetamine (rac -MA) was resolved with 2R,3R -tartaric acid (TA) and its derivatives (O,O,-dibenzoyl-(2R,3R)-tartaric acid monohydrate (DBTA) and O,O,-di- p -toluoyl-(2R,3R)-tartaric acid (DPTTA)), individually and using them in different combinations. After partial diastereomeric salt formation, the free enantiomers were extracted by supercritical fluid extraction using carbon dioxide as solvent. DBTA and DPTTA are efficient resolving agents for rac -MA, the best chiral separation being obtained at a molar ratio of 0.25 resolving agent to racemic compound for both resolving agents (eeE = 82.5% and eeE = 57.9%, respectively). Compared with the two other acids, TA is practically unsuitable for enantiomer separation (eeE < 5%). Applying a mixture of one individually active and one ineffective acid in half the equivalent molar ratio, when the acids are in 1:1 ratio in the mixture, the resolution efficiency values obtained exceeded those obtained by using the components individually. Decreasing the molar ratio of resolving agent mixture to 0.25, at which the individual resolving agents give the best chiral separation, the obtained resolution efficiency values did not differ significantly from those expected. The outcome of the resolution process depended only on the amount of the individually active resolving agents in the mixture. Chirality, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||