Concentrations Of Magnesium Chloride Research Articles

Purification and characterization of chlorophyllase from algaPhaeodactylum tricornutum by preparative native electrophoresis

The partially purified chlorophyllase, obtained from the algaPhaeodactylum tricornutum, was further purified by preparative native gel electrophoresis. The purification procedure provided the recovery of large amounts of a single purified chlorophyllase fraction. However, the electrophoretic analyses of the purified enzymatic fraction under denaturing conditions demonstrated the presence of two bands with mol wt of 43 ±3 and 46 ±3 kDa. The purification procedure resulted in 2-and 195-fold increases in chlorophyllase activity compared to that of the partially purified and crude enzymatic extracts, respectively. The optimum pH for chlorophyllase hydrolytic activity was found to be 8.0. The optimum incubation time and temperature for the hydrolytic activity of the purified chlorophyllase were found to be 2 h and 31°C, respectively. The optimum concentrations of magnesium chloride and dithiothreitol, used as activators, were 4 and 5 mM, respectively. The addition of individual plant membrane lipids, including phosphatidylcholine, phosphatidylglycerol, and β-carotene, to the reaction media increased the enzyme activity markedly. The purified enzyme fraction displayed preferential specificity toward selective substrates with an order of activity as follows: purified chlorophyllb > purified chlorophylla > partially purified chlorophyll > crude chlorophyll. Diisopropyl fluorophosphate and phytol, respectively, showed noncompetitive and competitive inhibitory effects on chlorophyllase activity with Ki, values of 0.78 mM and 3.75μM, respectively.

Increased buffer pH enhances sensitivity and specificity of human papillomavirus detection using consensus primer based PCR.

Polymerase chain reaction (PCR) buffers were optimized for the specific detection of human papillomavirus (HPV) sequences. The effect of pH, potassium chloride concentration and magnesium chloride concentration of three different consensus primers were examined. Several phylogenetically distinct HPVs (HPV1, HPV2, HPV6, HPV8, HPV16, HPV18, and HPV20) were used to determine the optimal buffer components. Genital types were less sensitive to changes in pH than cutaneous types. Higher buffer pH, with a few exceptions, led to increased sensitivity and specificity of HPV detection.

Reliability of RAPD fingerprinting of three basidiomycete fungi, Laccaria, Hydnangium and Rhizoctonia

Randomly amplified polymorphic DNA (RAPD) profiles are currently being developed for Laccaria and Hydnangium species and Rhizoctonia solani. The technique is increasingly being used to differentiate fungal isolates. As for the polymerase chain reaction (PCR) from which it was derived, the conditions necessary for reproducible RAPD products have received attention. However, in contrast to the PCR reaction, the technique relies on non-specific primers and as a consequence the reaction conditions are not necessarily as specific as they are in PCR. Compared with PCR products, RAPD fingerprints were therefore more sensitive to reaction and thermocycle conditions. RAPD products produced using 10 and 17–23 mer primers were visualized on ethidium bromide stained polyacrylamide electrophoresis gels. Factorial experiments showed RAPD patterns were altered by changes in various reaction mixture components including the concentration of non-DNA impurities, the number and concentration of primers and the DNA polymerase enzyme type, source and concentration. These factors, particularly the enzyme source, reacted differently with the magnesium chloride concentration. Fluorescent dye labelled primers were used with internal lane standards in a DNA sequencing system to assess accurately the molecular weights and relative amounts of reaction products. Attachment of the fluorescent label appeared to favour the synthesis of some fragments compared with others on patterns visualized on ethidium bromide stained non-denaturing polyacrylamide gels. The temperature at which DNA was denatured in the first cycles altered the fingerprints. Reaction mixture temperatures of 94° or higher, compared with 91–93°, caused loss of visual yield of some products, particularly those greater than 500 base pairs, and increased the yield of others. Reproducibility of RAPD patterns, when the reaction mixture and temperature profile factors were varied, was facilitated by cross reference to fluorescently labelled bands separated with internal lane standards in a DNA sequencing system. Reproducibility of fingerprint patterns in a standard reaction mixture was achieved, with different thermocycle programmes and in different thermocyclers when the temperature profile was reproduced, suggesting that particular RAPD fingerprints may be reproduced in any laboratory provided the same set of reaction and thermocycle conditions are used.

Biocatalysis of chlorophyllase from Phaeodactylum tricornutum in a biphasic organic system

AbstractThe hydrolytic activity of a partially purified chlorophyllase, obtained from the alga Phaeodactylum tricornutum, was determined in a biphasic organic system using different mixtures of hexane and Tris–HCl buffer solution (20 mmol dm−3, pH 7·5). The most appropriate kinetic parameters were determined for the optimum hydrolytic activity of chlorophyllase including hexane concentration (45%), optimum pH (7·5), time of incubation (7 h), incubation temperature (25°C) and enzyme concentration (10 μg cm−3). The optimum concentrations of magnesium chloride and dithiothreitol, used as activators, were determined to be 4 mmol dm−3 and 5 mmol dm−3, respectively. The results also indicated that diisopropyl fluorophosphate (DIFP) had a mixed competitive–non‐competitive inhibitory effect on chlorophyllase activity. The end‐products of the chlorophyllase hydrolytic reaction were identified and confirmed, using thin‐layer and high‐performance liquid chromatographies, spectrophotometric scanning and Fourier transform infrared spectroscopy.

Rapid Detection of Salmonellae by Means of a New Impedance-Splitting Method

An Impedance-Splitting method is proposed for the rapid detection of salmonellae in foods. The measuring System, BacTrac™ 4100, permits the registration of changes, caused by bacterial metabolism, not only of the impedance of the culture medium but also of changes in the ionic layers at the measuring electrodes, which has advantages in case of high salt concentrations. These changes are expressed as percentage decreases of the initial values, M-value and E-value, respectively. Food samples were pre-enriched 14 to 16 h at 37°C in peptone water by addition of mannitol, which facilitated the detection of salmonellae on selective culture media. Following this, 0.1 mi of the preenrichment culture was transferred to 9.9 ml of Impedance-Splitting Salmonellae (ISS) medium which consisted of magnesium chloride (hydrated), malachite green oxalate, novobiocin, phosphate buffer, mannitol, peptone and yeast extract. Despite the high magnesium chloride concentration in this medium, salmonellae produced changes of the E-value up to 100%, while the changes in M-values were limited to a few percent. The impedance changes were automatically recorded during incubation in the measuring system for up to 22 h at 40°C, and the time required to exceed a threshold value of 15% (E reaction time) was evaluated. Comparative testing of the ISS method with standard cultural analysis of 250 unknown food samples showed high sensitivity and selectivity in detecting salmonellae. From all of the 122 Salmonella-positive samples, the largest number (119) was obtained by the ISS method, as compared to that obtained by conventional testing with the selenite-cystine (106), Rappaport Vassiliadis soya (95), Rappaport Vassiliadis (92) and tetrathionate brilliant green medium (64). Six samples were false positive by Enterobacter cloaceae. One strain each of Salmonella enteritidis PT8 and Salmonella panama were not recorded. The ISS method is very suitable as a screening test, all the more since a negative investigation result will be obtained within 38 h. In view of the practicability, this method is superior to the enzyme-immunological and molecular-biological procedures.

Immunoaffinity Chromatographic Purification of Russell′s Viper Venom Factor X Activator Using Elution in High Concentrations of Magnesium Chloride

RVV-X, the factor X activator from Russell′s viper venom, has been isolated using affinity chromatography on agarose columns of a monoclonal antibody specific for this enzyme. Upon testing acid, alkaline, and high concentrations of MgCl 2 for elution, it was found that use of high concentrations of MgCl 2 was most effective in elution of RVV-X. It was nondenaturing and yielded 90% recovery of homogeneous enzyme without measurable contamination by other proteins of the venom.

Growth of Salmonella and competing flora in five commercial Rappaport-Vassiliadis (RV)-media

Growth of 18 Salmonella strains belonging to 11 serotypes and the bacterial flora of deep-frozen broiler carcasses was examined in five commercial Rappaport-Vassiliadis (RV) media. Growth was measured by an automated turbidometer (Bioscreen R). Significant differences in performance between the media investigated were observed. The unequal performances were ascribed to differences in the concentration of magnesium chloride (MgCl 2) and the type of peptone used.

Differential staining of glycosaminoglycans in the predentine and dentine of rat incisor using cuprolinic blue at various magnesium chloride concentrations.

Rat incisors were fixed with a solution of 0.05% Cuprolinic Blue and 2.5% glutaraldehyde in the presence of various concentrations of MgCl2 according to the critical electrolyte concentration (CEC) principle. This method allows glycosaminoglycans (GAG) to be properly preserved and visualized. Small granules were stained by the cationic dye in the predentine in the absence of MgCl2. These granules grew in size and became more electron-dense when the concentration of the electrolyte was increased. Larger ribbon-like structures and granules were seen when 0.3 M MgCl2 was used. In the dentine, tiny dots in close association with the surface of the collagen fibres, or their periodic striations, were positively stained. A thick electron-dense band located on the dentine side at the predentine-dentine junction was seen both with and without 0.05 M MgCl2. With higher concentrations of the electrolyte (0.1-0.3 M), this band was reduced to a very thin line located at the border of the dentine, along with mineralizing collagen fibres. This demonstrated the presence of GAG at the dentine surface and therefore indicated that GAG may play a role as nucleator agent.

Application of an organic solvent extraction to the determination of catechol-O-methyltransferase activity by high-performance liquid chromatography in human mononuclear cells

We report here a method for measuring mononuclear cell catechol-O-methyltransferase (COMT) activity which is ideally adapted to clinical studies. The method measures the O-methylation of dopamine to 3-methoxytyramine and 4-methoxy-3-hydroxyphenethylamine. Whole mononuclear cell sonicate is incubated with saturating concentrations of dopamine, S-adenosyl- l-methionine and magnesium chloride in sodium—potassium phosphate buffer at pH 7.3. An organic solvent extraction using ethyl acetate is then used for product separation, followed by high-performance liquid chromatography with electrochemical detection for product separation and quantification. This method allows both O-methylated products, 3-methoxytyramine and 4-methoxy-3-hydroxyphenethylamine, to be isolated and quantified separately. The apparent Michaelis constants for dopamine and S-adenosyl- l-methionine using this method are similar to values reported previously (0.51 and 14 μ M, respectively). The optimal concentration of magnesium chloride is eight to ten times higher than previously reported. No endogenous inhibitors were apparent using this assay. The within-day coefficient of variation using this method is 7% when measuring 3-methoxytyramine and 5% when measuring 4-methoxy-3-hydroxyphenethylamine. The between-day coefficient of variation is 11%. Mononuclear cell COMT activity can be detected using protein concentrations as low as 0.75 mg/ml, corresponding to 2–3 ml of whole blood. The small amount of blood required per sample allows multiple sample analysis from a single patient, including infants.

Analysis of the structure of photosystem I in cyanobacterial thylakoid membranes

Using electron microscopy of negatively stained specimens, we have investigated the shape and degree or association or photosystem (PS) I complexes in cyanobacterial thylakoid membranes. When incubated at high concentrations of magnesium chloride (>0.15 M), the PSI complexes from small ordered arrays in the membrane composed of monomeric complexes in a PI square lattice of dimensions a= b=11 nm. Averaged projections of the complex resemble chose found for the purified PSI reaction centre arter reconstitution (Ford, R.C, Hefti, A. and Engel, A. (1990) EMBO J. 9, 3067-3075). Some small differences in its shape are discussed, with particular reference to the differences in the polypeptide composition of the 2 preparations. We find that the complex remains in the monomeric form in the thylakoid membrane under all the conditions tested.

The recovery of pure lithium chloride from “brines” containing higher contents of calcium chloride and magnesium chloride

Lithium chloride can be extracted from brines which accompany natural gas. The extracts contain residual concentrations of calcium chloride and magnesium chloride. The separation of these associated components is performed using differences in the solubilities of the carbonates and hydrogen carbonates, followed by binding the remaining alkaline earth ions to a chelating resin.

Chromatographic fractionation of nucleic acids using microcapsules made from plant cells

The chromatographic fractionation of nucleic acids and oligodeoxyribonucleotides on a vesicular packing (VP) material has been investigated. As the VP material consists of microcapsules with a negatively charged ultrafiltration membrane, the experiments were focused on permeation chromatography in aqueous buffers of different ionic compositions. The adsorption of oligonucleotides and nucleic acids by the VP material occurring at pH values below 7 and especially in the presence of divalent cations, was negligible in neutral or weakly alkaline buffers. In such buffers the separation principle is based only on the permeation of polyanions into the stationary liquid within the vesicles. Polydisperse samples may be separated into an excluded peak fraction (at 40% of bed volume), fractions with intermediate elution volumes and a permeating peak fraction (at 95% of bed volume). The ratio between these fractions can be varied gradually by changing the salt concentration. Using defined oligonucleotides the maximum chain length for permeation into the whole stationary phase was smaller than the minimum chain length for complete exclusion. Both values were dependent on the salt concentration and pH. They could be varied gradually and reversibly over a wide range by altering the magnesium chloride concentration from 0 to 10 m M. In contrast to ion-exclusion effects known from gel permeation chromatography, in vesicle permeation chromatography there is no salt effect on the elution volume of the permeable fraction. Preparative applications for the fractionation of oligodeoxyribonucleotides and nucleic acids are presented.

Theophylline and magnesium inhibit the contraction elicited with ciclosporin and angiotensin II in mesangial cell cultures.

One serious side effect of ciclosporin (CS) therapy is its acute nephrotoxicity characterized by a marked decrease in glomerular filtration rate (GFR). A main determinant of GFR is the ultrafiltration coefficient which is thought to be regulated by the contractile state of the cells of the mesangium. CS enhances contractions of mesangial cells elicited with angiotensin II. By way of a lowered ultrafiltration coefficient this effect of CS may be partly responsible for its acute nephrotoxicity. We have therefore examined the effect of compounds that may attenuate the enhanced contractile response of the smooth-muscle-like mesangial cells. Prostaglandin E2 (10(-8)-10(-5) mol/l) and dibutyryl cyclic AMP (10(-4) mol/l) reduced the number of contracting cells from more than 50% to about 10%. The clinically used agent theophylline (10(-5) g/ml) decreased the number of contractions of CS-pretreated mesangial cells from 80.0 to 28.4% (p less than 0.001). Additionally, a marked decrease in the percentage of contractions (83.3 to 33.3%; p less than 0.001) was observed when the concentration of magnesium chloride was elevated from 0 to 2 mmol/l. The finding that the enhanced contractile response of CS-pretreated mesangial cells can be overcome by theophylline and/or high magnesium levels may be of clinical interest with a view to acute CS nephrotoxicity.

Characterization of polymerase chain reaction amplification of specific alleles

Under certain conditions, polymerase chain reaction (PCR) can be used to differentially amplify one allele over another. To characterize the phenomenon, we have made a series of PCR primers and determined whether differential amplification could be detected after agarose gel electrophoresis. Two allele pairs were examined; one pair represents a transversion and one pair represents a transition. The following conclusions emerge: (i) when the 3′ or the 3′ penultimate base of the oligonucleotide mismatched an allele, no amplification product could be detected; (ii) when the mismatches were 3 and 4 bases from the 3′ end of the primer, differential amplification was still observed, but only at certain concentrations of magnesium chloride; (iii) the mismatched allele can be detected in the presence of a 40-fold excess of the matched allele; (iv) primers as short as 13 nucleotides were effective; and (v) the specificity of the amplification could be overwhelmed by greatly increasing the concentration of target DNA.

Effects on egg production and quality of supplementing the diet of hens laying brown eggs with blood meal and magnesium chloride

SUMMARYIn a 2 × 4 factorial experiment, the laying performance of hens given diets with or without blood meal and four concentrations (0, 5·71, 11·43 and 17·14 g/kg) of added magnesium chloride was measured for 280 days. The inclusion of 50 g/kg blood meal in the laying diet reduced the rate of laying (P < 0·05), egg weight (P < 0·01), egg output (P < 0·01), food intake (P < 0·01), body weight gain (P < 0·01) and body weight at 457 days (P < 0·05). It increased the height of albumen (P < 0·05), Haugh unit score (P < 0·01) and shell colour intensity (P < 0·05) of fresh eggs. The inclusion of increasing dietary concentrations of magnesium chloride reduced (P < 0·01) the specific gravity of eggs but had no significant effect on any of the other egg quality or production characteristics. The dietary treatments had no significant effect on Haugh units of stored eggs.

Magnesium-25(2+) and chloride-35 quadrupolar relaxation in aqueous magnesium chloride solutions at 25.degree.C. 2. Relaxation at finite magnesium chloride concentrations

Magnesium-25(2+) and chloride-35 quadrupolar relaxation in aqueous magnesium chloride solutions at 25.degree.C. 2. Relaxation at finite magnesium chloride concentrations

The effect of incubation temperature and magnesium chloride concentration on growth of salmonella in home‐made and in commercially available dehydrated Rappaport‐Vassiliadis broths

Growth rate of salmonellas in Rappaport-Vassiliadis broth (RV) decreased with higher temperature when incubated at 40, 42 and 43 degrees C. Home-made RV and RV-Merck were less inhibitory than RV-Oxoid and RV-lab m. At 43 degrees C growth of all strains of Salmonella dublin were almost completely inhibited in all types of RV. In home-made RV and RV-Merck incubated at 42 degrees C, Salm. dublin was not inhibited any more than other serotypes tested. Variations in growth rate between different types of RV could be explained by differences in concentration of MgCl2. RV with higher MgCl2-concentration were most inhibitory. It is proposed that RV should be incubated at 41.5 +/- 0.5 degrees C (42.0 +/- 0.1 degrees C in a waterbath) and that the amount of MgCl2.6H2O should be approximately 28.6 g/l of the ready-to-use medium, which corresponds to the formula in the original description.

The effect of incubation temperature and magnesium chloride concentration on growth of salmonella in home‐made and in commercially available dehydrated Rappaport‐Vassiliadis broths

The combined effect of ultrasonic (20 KHz, 150 W) and heat treatment on the survival of two strains of Bacillus subtilis in three suspending media (distilled water, glycerol and milk) has been studied. When spores suspended in water or milk were subjected to ultrasonic waves before heat treatments a little or no decrease of the heat resistance was observed. However, both sporicidal agents applied simultaneously (thermo-ultrasonication) decreased by 63% (B. subtilis, var. niger-40) and 74% (B. subtilis ATCC 6051) the decimal reduction times for the heat treatment when the spores were suspended in glycerol and by 79% and 40%, respectively when suspended in milk. The thermo-ultrasonication of spores in water markedly reduced the heat resistance of them (between 99.9% and 70%) in the range 70-95 degrees C but the effect of the thermo-ultrasonication significantly diminished as the temperature of the treatment was approached to the boiling point of the water.

Isothermal diffusion coefficients for sodium chloride-magnesium chloride-water at 25.degree.C. 3. Low magnesium chloride concentrations with a wide range of sodium chloride concentrations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsothermal diffusion coefficients for sodium chloride-magnesium chloride-water at 25.degree.C. 3. Low magnesium chloride concentrations with a wide range of sodium chloride concentrationsRoy Mathew, Luigi Paduano, John G. Albright, Donald G. Miller, and Joseph A. RardCite this: J. Phys. Chem. 1989, 93, 10, 4370–4374Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 May 1989https://doi.org/10.1021/j100347a091RIGHTS & PERMISSIONSArticle Views179Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (622 KB) Get e-Alerts

Isothermal diffusion coefficients for sodium chloride-magnesium chloride-water at 25.degree.C. 2. Low concentrations of sodium chloride with a wide range of magnesium chloride concentrations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsothermal diffusion coefficients for sodium chloride-magnesium chloride-water at 25.degree.C. 2. Low concentrations of sodium chloride with a wide range of magnesium chloride concentrationsLuigi Paduano, Roy Mathew, John G. Albright, Donald G. Miller, and Joseph A. RardCite this: J. Phys. Chem. 1989, 93, 10, 4366–4370Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 May 1989https://doi.org/10.1021/j100347a090RIGHTS & PERMISSIONSArticle Views78Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (645 KB) Get e-Alerts