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Acid Conditions (acid + condition)
Selected AbstractsStudy on Decoloration of Acidic Scarlet GR by Pyrolusite Oxidation under an Acid ConditionACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2006CHEN Gang Abstract, Decoloration of acidic scarlet GR by pyrolusite is studied in this paper. The effects of pH in solution, dosage and granularity of pyrolusite, reaction temperature, and vibration speed on decoloration efficiency are discussed. According to experiment results, the decoloration efficiency may exceed 95% for 40 mg/L GR solution by pyrolusite. pH is most important among all factors which impact the decoloration of acidic scarlet GR. Dosage and granularity of pyrolusite, reaction temperature, and vibration speed have a little benitfit on decoloration. The high decoloration efficiency and low removal efficiency of COD as well as FT-IR spectra of products between pyrolusite and acidic scarlet GR indicate that acidic scarlet GR undergoes the redox reaction on the interface of mineral and its chromophore is oxidated and decolored, but it is not removed thoroughly by oxidation. [source] The Ritter Reaction under Truly Catalytic Brønsted Acid ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 28 2007Roberto Sanz Abstract Simple organic acids like 2,4-dinitrobenzenesulfonic acid (DNBSA) catalyze the Ritter reaction of secondary benzylic alcohols giving rise to the corresponding N -benzylacetamides in usually high yields. Reactions can be conducted without exclusion of oxygen and without the need of dry solvents. With tertiary ,,,-dimethylbenzylic alcohols a different pathway involving a formal dimerization reaction takes place under the acid-catalytic conditions used. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] ChemInform Abstract: Furan Ring Recyclization in 2-Furfurylthieno[2,3-b]pyridines: An Intramolecular N-Alkylation of Pyrrole Ring under Acid Conditions.CHEMINFORM, Issue 34 2010Darya Yu. Abstract Depending on reaction conditions, the new heterocycles (V) and (VII) are formed from the 4-unsubstituted derivative (IVa). [source] Carry-over effects of embryonic acid conditions on development and growth of Rana temporaria tadpolesFRESHWATER BIOLOGY, Issue 1 2002K. RÄsänen 1.,Conditions experienced during the early stages of development may have carry-over effects on performance during later life. The egg laying period and embryonic development of temperate and boreal zone amphibians often coincides with peak acidity resulting from spring snow-melt, but the effects of acid conditions during embryonic stage on subsequent performance are unknown. 2.,We investigated the potential carry-over effects of acidity during the embryonic stage on performance up to metamorphosis in the common frog (Rana temporaria) tadpoles. There were four combinations of acid (4.5) and neutral (7.5) pH treatments applied to the egg and larval stages in a factorial laboratory experiment. In addition, we studied the difference in embryonic and larval tolerance of acidity between two populations originating from circumneutral (pH 6.6) and acidic conditions (pH 4.8). 3.,The effects of acid conditions during the embryonic stage were sublethal, as indicated by delayed development and reduced size. Under acid conditions, tadpoles that had been raised in neutral water as embryos at first grew more slowly than tadpoles raised under acid conditions as embryos. At metamorphosis, no effects of embryonic acidity were detectable indicating that tadpoles were able to compensate fully for the initial reduction in growth. 4.,Acid conditions during the larval period had a strongly negative effect on survival, size and age at metamorphosis. The amount of food consumed was lower under acid conditions, suggesting that reduced food consumption was at least partly responsible for the negative effects. 5.,Although the two populations differed in the length of larval period, there was no indication of a differential response to the treatments in any of the metamorphic traits studied. 6.,These results suggest that, although moderate acid conditions during embryonic development affect growth and development negatively, this influence does not persist after conditions have returned to normal. However, even moderately acid conditions during the larval period may have a strong negative influence on survival and performance of the tadpoles. [source] Unusual Rearrangements of cis -4,7-Disubstituted 4,7-Dihydro4,7-dihydroxy[2.2]paracyclophanes on Dehydration: Stereoselective Formation of Planar Chiral CyclohexadienonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2003Natalia Vorontsova Abstract Under acid conditions, cis -4,7-disubstituted 4,7-dihydro-4,7-dihydroxy[2.2]paracyclophanes undergo dehydration accompanied by rearrangement, affording cyclohexadienone derivatives as major products and with polysubstituted phenols being formed as minor products. The formation of either an ortho or a para semiquinoid system, as well as the configuration of the newly formed asymmetric center, depended strictly on the nature of the substituent (alkyl, allyl, or phenyl). The structures of 3,4-dihydro-3,7-dimethyl[2.2]paracyclophane-4-one (10), 3,7-diallyl-3,4-dihydro[2.2]paracyclophane-4-one (12), and 4,7-dihydro-7,8-diphenyl[2.2]paracyclophane-4-one (22) were determined by X-ray structural analysis. [2.2]Paracyclophane-4,7-quinone (1) was obtained in optically active form. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] GEOGRAPHIC VARIATION IN ACID STRESS TOLERANCE OF THE MOOR FROG, RANA ARVALIS.EVOLUTION, Issue 2 2003Abstract Spatially varying directional selection together with restricted gene flow among populations is expected to lead to local adaptation. One environmental factor that potentially causes strong directional selection, but is little explored in evolutionary terms, is naturally and anthropogenically induced acidity. We studied local adaptation to acidity in four Swedish populations (two originating from areas that have suffered from severe anthropogenic acidification during the 1900s and two from areas which have remained neutral due to higher buffering capacity) of the moor frog Rana arvalis in a laboratory experiment by investigating whether differences in acid tolerance correspond to population origin. Embryos were raised from fertilization to hatching at three different pH levels (pH 4.0, 4.25 and 7.5), corresponding to levels experienced by these populations in nature, and acid stress tolerance was measured in terms of embryonic survival, hatchling size, and age. Evidence for local adaptation in all of these traits was found, the acid origin embryos having higher survival and less impaired growth performance under acid conditions than the neutral origin embryos. Our estimated rates of divergence (0.007,0.102 haldanes) suggest a rapid adaptation process in response to anthropogenic environmental change, and that the different traits have evolved at relatively similar rates. [source] Carry-over effects of embryonic acid conditions on development and growth of Rana temporaria tadpolesFRESHWATER BIOLOGY, Issue 1 2002K. RÄsänen 1.,Conditions experienced during the early stages of development may have carry-over effects on performance during later life. The egg laying period and embryonic development of temperate and boreal zone amphibians often coincides with peak acidity resulting from spring snow-melt, but the effects of acid conditions during embryonic stage on subsequent performance are unknown. 2.,We investigated the potential carry-over effects of acidity during the embryonic stage on performance up to metamorphosis in the common frog (Rana temporaria) tadpoles. There were four combinations of acid (4.5) and neutral (7.5) pH treatments applied to the egg and larval stages in a factorial laboratory experiment. In addition, we studied the difference in embryonic and larval tolerance of acidity between two populations originating from circumneutral (pH 6.6) and acidic conditions (pH 4.8). 3.,The effects of acid conditions during the embryonic stage were sublethal, as indicated by delayed development and reduced size. Under acid conditions, tadpoles that had been raised in neutral water as embryos at first grew more slowly than tadpoles raised under acid conditions as embryos. At metamorphosis, no effects of embryonic acidity were detectable indicating that tadpoles were able to compensate fully for the initial reduction in growth. 4.,Acid conditions during the larval period had a strongly negative effect on survival, size and age at metamorphosis. The amount of food consumed was lower under acid conditions, suggesting that reduced food consumption was at least partly responsible for the negative effects. 5.,Although the two populations differed in the length of larval period, there was no indication of a differential response to the treatments in any of the metamorphic traits studied. 6.,These results suggest that, although moderate acid conditions during embryonic development affect growth and development negatively, this influence does not persist after conditions have returned to normal. However, even moderately acid conditions during the larval period may have a strong negative influence on survival and performance of the tadpoles. [source] Shifts in the ecological behaviour of plant species between two distant regions: evidence from the base richness gradient in miresJOURNAL OF BIOGEOGRAPHY, Issue 2 2008Petra Hájková Abstract Aim, Water pH and conductivity are known to be major environmental factors controlling the species composition of nutrient-poor wetlands. Based on the analysis of two large data sets of species co-occurrence, sampled along the entire pH/calcium gradient, we explored whether species exhibit similar or different ecological behaviour in the two regions. Location, West Carpathians (central Europe) and Bulgaria (south-eastern Europe), situated 800 km apart. Bulgaria represents a range margin for many mire species. Methods, The probability of occurrence of the 41 most common species along the pH and conductivity gradients was assessed using logistic regression fitted by means of generalized additive models. The species optimum and amplitude were determined. To check the possible effect of competitive release, we estimated where the potential maximum number of species (maximum overlap in realized niches) occurs along the base richness gradient. Results, Most of the 41 frequently occurring species showed a significant response to water pH and ln-transformed conductivity (approximating total mineral richness) in both regions. Eight species showed a shift in pH optimum greater than one unit, while 12 species showed the same or a larger shift along the conductivity gradient. Nearly all these striking shifts were connected to an extension of species tolerance towards mineral-poor acid habitats in Bulgaria, which causes links between species and measured factors to be conspicuously weaker in Bulgaria than in the West Carpathians. Regarding ecological amplitude, 24 species exhibited a wider tolerance to water conductivity in the West Carpathians, whereas 17 species exhibited a wider tolerance in Bulgaria. Main conclusions, A distinctive variation in the realized niche was observed in a large portion of the species examined. Niche shifts between local populations of the same species were similar to those of closely related vicariant species. Ecotypic adaptation within species is a possible explanation for this pattern. Other possible explanations (competitive release, specific habitat conditions, compensation for climate) seem to be less justified. The local populations of rich-fen species may have adapted to mineral-poor acid conditions in the high crystalline mountains of Bulgaria during dry periods of pleniglacials. Nomenclature,Marhold & Hindák (1998); for Balkan elements not included in this source, Andreev et al. (1992). [source] Synthesis of new fused isoquinolines via reissert compoundsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2008Christian Fuchs Reissert compounds 2 derived from isoquinoline, chloroformates and TMS-cyanide were alkylated in position 1. The resulting alkylation products 3 as well as the precursors 2 reacted with Grignard reagents affording imidazoisoquinolines 4, 5, 7 and 8 by addition to the cyano group and Grignard reduction or by twofold addition to the cyano group, respectively. In both cases the alcohol of the 2-alkoxycarbonyl moiety was eliminated by attack of the N-atom at the carbonyl carbon atom. Under acid conditions, 1-benzylated Reissert compound 3h cyclised by attack of the resulting N-acyliminium C-atom at the o -position of the benzyl ring to form tetracyclic 1,3-bridged tetrahydroisoquinolines 10 and 11. Bromocyclisation of 1-allyl-2-menthyloxycarbonyl-substituted Reissert compounds 3b, c led to tricyclic dibromo products 12, in which the menthol moiety was split off and addition to the enamine double bond occurred. A 2-menthyloxycarbonyl group in Reissert compounds 2a and 3 failed to exert an asymmetric induction in all cases. [source] An efficient and regiospecific preparation of trifluoromethyl substituted 4-( 1H -pyrazol-1 -yl)-7-chloroquinolinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2005Helio G. Bonacorso A new series of 4-[3-alkyl(aryl)(heteroaryl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H -pyrazol-1-yl]-7-chloroquinolines, where [alkyl = CH3; aryl = C6H5, 4-CH3C6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 4-CH3OCgH4, 4-NO2CgH4, 4-biphenyl, 1-naphthyl; heteroaryl = 2-furyl and 2-thienyl] has been regiospecifi-caly obtained from the reaction of 7-chloro-4-hydrazinoquinoline with 4-substituted-l,1,1-trifluoro-4-methoxybut-3-en-2-ones in 61 - 96 % yield. Subsequently, dehydration reaction of 4,5-dihydropyra-zolylquinolines under acid conditions furnished a new series of 4-(3-substituted-5-trifluoromethyl-1H -pyra-zol-1-yl)-7-chloroquinolines in 73 - 96 % yield. [source] EFFECT OF LACTIC ACID AND LACTIC ACID BACTERIA TREATMENT ON MYOFIBRILLAR PROTEIN DEGRADATION AND DYNAMIC RHEOLOGY OF BEEFJOURNAL OF TEXTURE STUDIES, Issue 3 2007M. SIGNORINI ABSTRACT Lactic acid has been used as an efficient decontaminant in meats aimed for direct consumption or product fabrication. However, reports on the functionality of proteins extracted from lactic acid-treated meat are scattered. The objective of this work was to study the degradation and gelling ability of myofibrillar protein extracts obtained from beef treated with lactic acid of chemical and microbial origins, stored at 4 and 20C. The gelling ability was considerably reduced by lactic acid treatment as a result of protein denaturation in acid conditions at both storage temperatures. Scanning electron microscopy showed loose structures resulting in low penetration resistance and storage modulus. Treatments with lactic acid or lactic acid bacteria (LAB) had similar effect on tan,, affecting gel rigidity but not elasticity. Penetration in gels obtained from LAB-treated meat was highly correlated with myosin degradation. Lactobacillus carnis -treated meat produced compact gels with high penetration resistance and storage modulus, although the structure became looser with storage time. LAB treatment, although not as efficient as lactic acid as a meat preservative, is a milder process causing less severe changes in meat structure rheology. PRACTICAL APPLICATIONS The potential of lactic fermentation by selected strains is somewhat limited as compared to lactic acid preservation of meat substrates, regarding pH reduction and its consequence on pathogens and spoilage microorganism population reduction. However, lactic acid bacteria (LAB) treatments are milder; therefore, changes in protein structure and rheology are less severe. Lactic acid in its chemical form promotes protein changes, whereas LAB does not. As myofibrillar protein configuration is responsible for most meat functional properties, such as gel and emulsion formation, it is important that protein structure remains unchanged as much as possible. Using nonproteolytic strains, protein degradation can only be altered by endogenous or bacteria-produced enzymes, which can be inhibited by several means. Meat preservation by lactic fermentation with selected strains can be an alternative when keeping meat protein functional properties unaltered. [source] Biodegradable Water Absorbent Synthesized from Bacterial Poly(amino acid)sMACROMOLECULAR BIOSCIENCE, Issue 3 2004Masao Kunioka Abstract Summary: Biodegradable hydrogels prepared by , -irradiation from microbial poly(amino acid)s have been studied. pH-Sensitive hydrogels were prepared by the , -irradiation of poly(, -glutamic acid) (PGA) produced by Bacillus subtilis and poly(, -lysine) (PL) produced by Streptomyces albulus in aqueous solutions. When the , -irradiation dose was 19 kGy or more, and the concentration of PGA in water was 2 wt.-% or more, transparent hydrogels could be produced. For the 19 kGy dose, the produced hydrogel was very weak, however, the specific water content (wt. of absorbed water/wt. of dry hydrogel) of this PGA hydrogel was approximately 3,500. The specific water content decreased to 200, increasing when the , -irradiation dose was over 100 kGy. Under acid conditions or upon the addition of electrolytes, the PGA hydrogels shrunk. The PGA hydrogel was pH-sensitive and the change in the volume of the hydrogel depended on the pH value outside the hydrogel in the swelling medium. This PGA hydrogel was hydrodegradable and biodegradable. A new novel purifier reagent (coagulant), made from the PGA hydrogels, for contaminated turbid water has been found and developed by Japanese companies. A very small amount of this coagulant (only 2 ppm in turbid water) with poly(aluminum chloride) can be used for the purification of turbid water. A PL aqueous solution also can change into a hydrogel by , -irradiation. The specific water content of the PL hyrdogel ranged from 20 to 160 depending on the preparation conditions. Under acid conditions, the PL hydrogel swelled because of the ionic repulsion of the protonated amino groups in the PL molecules. The rate of enzymatic degradation of the respective PL hydrogels by a neutral protease was much faster than the rate of simple hydrolytic degradation. [source] Recombinant expression and characterization of a lysozyme from the midgut of Triatoma brasiliensis (Hemiptera, Reduviidae) in comparison with intestinal muramidase activityPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2009PETER J. WANIEK Abstract. Insect c-type lysozymes are antibacterial proteins that are synthesized in different organs with high activity against Gram-positive bacteria. Because lysozymes possess muramidase activity, they also play an important role in the digestion of bacteria in Diptera. Triatomines express lysozyme-encoding genes constitutively in the anterior region (cardia and stomach) of the midgut and the fat body after injection of bacteria into the haemocoel. The present study describes the overexpression of the Triatoma brasiliensis lysozyme 1 (lys1) in Escherichia coli. Recombinant T. brasiliensis Lys1 (TbLys1) is purified after solubilization of the inclusion bodies. The protein refolds successfully, showing muramidase activity against Micrococcus lysodeikticus lyophilized cells, after enterokinase cleavage of its thioredoxin fusion protein. In in-gel zymograms and turbidimetric liquid assays TbLys1 is broadly active under alkaline and acid conditions, indicating a possible digestive function in the two physiologically different midgut regions of the bug: the stomach and small intestine. Muramidase activity is shown in the stomach and small intestine content of unfed bugs and bugs at different days after feeding, respectively. Western blot analysis identifies TbLys1 as lysozyme. [source] | |||||||||||||