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Acid pH (acid + ph)
Selected AbstractsACID PH PRODUCED BY LACTIC ACID BACTERIA PREVENT THE GROWTH OF BACILLUS CEREUS IN BOZA, A TRADITIONAL FERMENTED TURKISH BEVERAGEJOURNAL OF FOOD SAFETY, Issue 2 2005KIYMET GÜVEN ABSTRACT The growth and survival of Bacillus cereus, a known pathogen commonly found in cereals, during lactic acid fermentation of boza, a traditional Turkish cereal beverage, was studied. In the boza base inoculated with both the starter culture and B. cereus, the acidity developed to pH 2.6 and 0.8% titratable acidity after 72 h; the growth of B. cereus was reduced from 3.9 log cfu/mL to 1 log cfu/mL within 72 h. The control boza base to which starter was not added had a pH of 3, titratable acidity of 0.8%. The B. cereus in this boza base to which no starter culture was added dropped to 1 log cfu/mL after 72 h. No strains of lactic acid bacteria were found to produce bacteriocins antagonistic to B. cereus. Low pH and acidity were found to be the major factors inhibiting growth of B. cereus in boza. [source] Haemoglobin Etobicoke, an incidental finding in an Irish diabeticINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 4 2003D. A. O'Brien Summary It is well recognized that haemoglobin variants can be detected during the measurement of HbA1c by high-performance liquid chromatography (HPLC). A number of variants have been reported as compromising the quantification of HbA1c, a marker used in the assessment of glycaemic control in diabetes. We describe a case of haemoglobin Etobicoke, a rare alpha chain variant detected in an Irish diabetic during HbA1c analysis. Its identity was confirmed using a series of investigations. These included haemoglobin electrophoresis at alkaline and acid pH, isoelectric focusing and globin chain electrophoresis. Ultimately mass spectrometry isolated the mutation at position alpha 84 (F5). Haemoglobin Etobicoke, first described in Canada in 1969 has not previously been detected on HbA1c analysis. In the presence of this rare variant, HbA1c, a standard method using HPLC to assess glycaemic control in diabetes is unreliable and alternatives such as fructosamine need to be considered. HbA1c measured by automated HPLC will effectively screen populations where haemoglobin variants were not previously known. Precise identity of these variants when they are detected is crucial to the reliable interpretation of HbA1c analyses. [source] Ion-pair mediated transport of angiotensin, neurotensin, and their metabolites in liquid phase microextraction under acidic conditionsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2005J. Léon E. Reubsaet Abstract This paper discusses the behaviour of angiotensin 1 and neurotensin together with their metabolites in a three-phase liquid phase microextraction under acidic conditions. Variations in donor phase, organic phase, and acceptor phase are studied with extraction recovery as response variable. It is proved that for all peptides the transport across the organic phase is mediated by heptane-1-sulphonic acid. n -Octanol gave overall best results as organic phase. A donor phase volume of 1.0 mL was chosen as a compromise between optimal recovery and robustness of the LPME device. The optimal pH of the donor phase (using acceptor phase of pH 2) was found to be different for the peptides, which opens opportunities for selective sample preparation. Decreasing the acceptor phase pH to 1.0 resulted in increased extraction recoveries. On using 1.0 mL of donor phase containing 50 mM heptane-1-sulphonic acid pH 3, n -octanol as organic phase immobilized in the pores of the fibre, and 20 ,L of acceptor phase containing 0.1 mol/L HCl, extraction recoveries up to 82% (enrichment factor = 41) were achieved. To our knowledge this is the first report on liquid phase microextraction of angiotensins and neurotensins. [source] Role of Mg2+ and pH in the modification of Salmonella lipid A after endocytosis by macrophage tumour cellsMOLECULAR MICROBIOLOGY, Issue 2 2005Henry S. Gibbons Summary Lipid A of Salmonella typhimurium is covalently modified with additional acyl and/or polar substituents in response to activation of the PhoP/PhoQ and/or PmrA/PmrB signalling systems, which are induced by growth at low Mg2+ concentrations and mild acid pH respectively. Although these conditions are thought to exist within macrophage phagolysosomes, no direct evidence for lipid A modification after endocytosis has been presented. To address this issue, we grew S. typhimurium inside RAW264.7 cells in the presence of 32Pi, and then isolated the labelled lipid A fraction, which was found to be extensively derivatized ,with phosphoethanolamine, aminoarabinose, 2-hydroxymyristate and/or palmitate moieties. S. typhimurium grown in tissue culture medium synthesized lipid A molecules lacking all these substituents with the exception of the 2-hydroxymyristate chain, which was still present. Using defined minimal media to simulate the intracellular pH and Mg2+ concentrations of endosomes, we found that lipid A of S. typhimurium grown in an acidic, low-Mg2+ medium closely resembled lipid A isolated from bacteria internalized by RAW264.7 cells. A subset of S. typhimurium lipid A modifications were induced by low Mg2+ alone. Escherichia coli K-12 W3110 modified its lipid A molecules in response to growth under acidic but not low-Mg2+ conditions. Growth in a high-Mg2+, mildly alkaline medium resulted in suppression of most lipid A modifications with the exception of the 2-hydroxymyristate in S. typhimurium. Although lpxO transcription was stimulated by growth on low Mg2+, the biosynthesis of lipid A species containing 2-hydroxymyristate was independent of PhoP/PhoQ and PmrA/PmrB in S. typhimurium. Our labelling methods should be applicable to studies of lipid A modifications induced by endocytosis of diverse bacteria. [source] Effect of Electrolyzed Water on Wound HealingARTIFICIAL ORGANS, Issue 12 2000Naoki Yahagi Abstract: Electrolyzed water accelerated the healing of full-thickness cutaneous wounds in rats, but only anode chamber water (acid pH or neutralized) was effective. Hypochlorous acid (HOCl), also produced by electrolysis, was ineffective, suggesting that these types of electrolyzed water enhance wound healing by a mechanism unrelated to the well-known antibacterial action of HOCl. One possibility is that reactive oxygen species, shown to be electron spin resonance spectra present in anode chamber water, might trigger early wound healing through fibroblast migration and proliferation. [source] Crystallization and preliminary X-ray crystallographic analysis of a highly specific serpin from the beetle Tenebrio molitorACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Sun Hee Park The Toll signalling pathway, which is crucial for innate immunity, is transduced in insect haemolymph via a proteolytic cascade consisting of three serine proteases. The proteolytic cascade is downregulated by a specific serine protease inhibitor (serpin). Recently, the serpin SPN48 was found to show an unusual specific reactivity towards the terminal serine protease, Spätzle-processing enzyme, in the beetle Tenebrio molitor. In this study, the mature form of SPN48 was overexpressed in Escherichia coli and purified. The purified SPN48 protein was crystallized using 14% polyethylene glycol 8000 and 0.1,M 2-(N -morpholino)ethanesulfonic acid pH 6.0 as the precipitant. The crystals diffracted X-rays to 2.1,Å resolution and were suitable for structure determination. The crystals belonged to space group P21. The crystal structure will provide information regarding how SPN48 achieves its unusual specificity for its target protease. [source] Extraction and analysis of colourful eggshell pigments using HPLC and HPLC/electrospray ionization tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009A. Gorchein Abstract The literature on the pigments of avian eggshells is critically reviewed. Methods using methanolic sulfuric acid or hydrochloric acid to extract eggshell pigments are unsuitable to detect the occurrence of zinc protoporphyrin or zinc biliverdin because they demetallate these compounds. Extraction methods are described here using EDTA and acetonitrile,acetic acid or acetonitrile,dimethyl sulfoxide, which do not demetallate zinc protoporphyrin. Such extracts were prepared from eggshell of the common nighthawk, Chordeiles minor, and from another six bird species. Protoporphyrin and biliverdin were identified and fully characterized by HPLC/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) in all samples, but none contained zinc protoporphyrin. The zinc complex of biliverdin, claimed to be an additional pigment responsible for eggshell background colours, was labile to EDTA and acid pH and if occurring naturally could not be extracted intact by the published or the modified protocols. An explanation is advanced for the exceptional report that all porphyrins from uroporphyrin to protoporphyrin were found in eggshells of the fowl Gallus domesticus. Copyright © 2009 John Wiley & Sons, Ltd. [source] Conformations of DNA strands containing GAGT, GACA, or GAGC tetranucleotide repeatsBIOPOLYMERS, Issue 4 2007Jaroslav Kypr Abstract The (GA)n microsatellite has been known from previous studies to adopt unusual, ordered, cooperatively melting secondary structures in neutral aqueous solutions containing physiological concentrations of salts, at acid pH values or in aqueous ethanol solutions. To find more about the primary structure specificity of these structures, we performed parallel comparative studies of related tetranucleotide repeats (GAGC)5, (GAGT)5, and (GACA)5. The general conclusion following from these comparative studies is that the primary structure specificity is fairly high, indicating that not only guanines but also adenines play a significant role in the stabilization of these unusual structures. (GAGC)5 is a hairpin or a duplex depending on DNA concentration. Neither acid pH nor ionic strength or the presence of ethanol changed the secondary structure of (GAGC)5 in a significant way. (GACA)5 forms a weakly stable hairpin in neutral aqueous solutions but forms a duplex at acid pH where cytosine is protonated. (GAGT)5 behaves most similar to (GAGA)5. Salt induces its hairpin to duplex transition at neutral pH and an isomerization into another, probably parallel stranded, duplex takes place at acid pH. (GAGT)5 is the only of the three present 20-mers that responds to ethanol like (GAGA)5. © 2007 Wiley Periodicals, Inc. Biopolymers 87: 218,224, 2007. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Characterization of allergens secreted by Anisakis simplex parasite: clinical relevance in comparison with somatic allergensCLINICAL & EXPERIMENTAL ALLERGY, Issue 2 2004M. L. Baeza Summary Background Diagnostic methods for the study of allergic reactions to Anisakis simplex (A.s.) based on whole-body extracts of the larva are clearly insufficient. Objectives To study the allergenicity of the proteins secreted by the parasite. Comparison with somatic antigens and determination of their clinical importance in allergic patients were also addressed. Methods An excretory/secretory (E/S) extract was produced by culturing third-stage A.s. larvae. It was used to perform immediate skin tests and to determine specific IgE in 10 patients diagnosed with allergy to A.s. Both tests were compared with the results obtained with the whole-body extract (somatic (S)). The molecular weight (MW) of their allergens was determined by immunoblotting, and a single-blind placebo-controlled oral challenge with E/S proteins was performed. Finally, allergens' resistance to gastric pepsin and acid pH was explored. Results A.s. larvae secreted allergens more potent than those present in the S extract. The skin prick test wheal area produced by E/S molecules and the absorbance obtained in the determination of specific IgE with these allergens (ELISA) were 5.8 times bigger than those obtained with S extract. MW allergens of 72 and 56 kDa in E/S extracts and those of 56, 48 and 43 kDa in S extract were recognized by more than 50% of the patients. Partial cross-reactivity between them was revealed by immunoblotting inhibition studies. Oral challenge with E/S extract (up to 479 ,g) was negative in all the patients. Treatment of E/S proteins with gastric pepsin inhibited the binding of the E/S allergens for specific IgE. The acid pH did not affect the overall binding of IgE to E/S extract. It decreased by 15.23% and 19.96% at pH 4 and 2, but the difference was not statistically significant. Conclusion A.s. secretes allergens more potent than somatic antigens and should be used in the diagnostic procedures. These allergens are inactivated by the pepsin, which supports the theory that live larva is necessary to induce an allergic reaction in most of the patients. [source] Characterization of ,- d -glucosidase extracted from soil fractionsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2000M. D. Busto Summary One way to study the state in which stabilized extracellular enzymes persist and are active in the soil is by extraction from the soil, with subsequent fractionation of enzyme,organomineral complexes and characterization of such complexes. In order to investigate the location and characteristics of soil ,-glucosidase, three soil fractions were obtained both from real (undisturbed) soil aggregates and from structural (dispersed in water and physically disrupted) aggregates using two different granulometric procedures. The ,-glucosidase activity of the fraction was then assayed. When the aggregates were dispersed, more than 73% of activity was in the soil microaggregates with diameters of less than 50 ,m (SF50). These aggregates were associated with strongly humified organic matter. Solutions of diluted pyrophosphate at neutral pH liberated active ,-glucosidase from all fractions, although the efficacy of extraction varied according to the type of fraction. The SF50 fraction and aggregates of 2000,100 ,m obtained by sieving (SF2000) showed the greatest ,-glucosidase activity (34.5 and 36.0%, respectively). Micro- and ultrafiltration of SF50 extracts increased the total ,-glucosidase activity, whereas these procedures, applied to the RF2000 fraction, decreased it. Humus,,-glucosidase complexes in the SF50 fraction, between 0.45 ,m and 105 nominal molecular weight limit ( nmwl) (SF50II) and < 105nmwl (SF50III) showed an optimum pH at 5.4, and in the SF50I fraction (> 0.45 ,m) the optimum was 4.0. The stability of ,-glucosidase in the aggregates of the smallest size SF50II and SF50III decreased at acid pHs. The presence of two enzymes (or two forms of the same enzyme) catalysing the same reaction with different values of Michaelis constant and maximum velocity was observed in all but one of the ,-glucosidase complexes extracted and partially purified from the SF50 aggregates. [source] | |||||||||||||