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Determined Spectrophotometrically (determine + spectrophotometrically)
Selected AbstractsPenetration of propylene glycol into dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2002E. V. Cruz Abstract Cruz EV, Kota K, Huque J, Iwaku M, Hoshino E. Penetration of propylene glycol into dentine. International Endodontic Journal, 35, 330,336, 2002. Aim This study aimed to evaluate penetration of propylene glycol into root dentine. Methodology Safranin O in propylene glycol and in distilled water were introduced into root canals with and without artificial smear layer. Dye diffusion through dentinal tubules was determined spectrophotometrically. The time required for dye to exit through the apical foramen using propylene glycol and distilled water as vehicles was also determined. The extent and areas of dye penetration on the split surfaces of roots were assessed using Adobe Photoshop and NIH Image Software. Results Propylene glycol allowed dye to exit faster through the apical foramen. The area and depth of dye penetration with propylene glycol was significantly greater than with distilled water (P < 0.0001). Smear layer significantly delayed the penetration of dye. Conclusion Propylene glycol delivered dye through the root canal system rapidly and more effectively indicating its potential use in delivering intracanal medicaments. [source] Kinetics of N -bromination of 2-oxazolidinoneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2004F. A. Amoedo The kinetics of N -bromination of 2-oxazolidinone by transfer of Br from sodium hypobromite, N -bromosuccinimide (NBS), or N -bromoacetamide (NBA) were determined spectrophotometrically, at pH between 4.6 and 12.45 (depending on the brominating agent). The reaction with hypobromite was of first order with respect to both the hypobromite and the substrate. The bromination of oxazolidinone with NBS (or NBA) has been found to be a reversible process of order one with respect to both NBA (or NBA) and oxazolidinone in the forward direction, and order one with respect to SI (or ACAM) and the resulting N -bromo-oxazolidinone in the other. The pH dependence of the reaction rate was in keeping with a mechanism in which all the brominating agents (HOBr, BrO,, NBS and NBA) react predominantly with the anion of the substrate. Bimolecular bromination rate constants increased in the order BrO, < NBA < NBS < HOBr. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 642,649, 2004 [source] Antioxidant properties of methanolic extracts from different parts of Sclerocarya birreaINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2008Abdalbasit A. Mariod Summary The methanolic extracts from Sclerocarya birrea leaves (SCL), roots (SCR), barks (SCB), and kernel oil cake (SCK) were examined for radical scavenging capacities and antioxidant activities. The total phenolics of the extracts was determined spectrophotometrically according to the Folin-Ciocalteau method using gallic acid as standard solution. The total phenolic compounds were found as 304.5, 367.5, 593, 148.0 and 258.0 mg g -1 of dry product, respectively. The extracts of SCL, SCR, SCB and SCK were markedly effective in inhibiting the oxidation of linoleic acid and subsequent bleaching of ,-carotene in comparison with the control. Based on oxidation of ,-carotene/linoleic acid, the SCK extract is the most effective followed by SCR, SCL and SCB extract. The antioxidant activity determined by the DPPH (1,1-diphenyl-,-picrylhydrazyl) method revealed that the SCK extract had the highest antioxidant activity on DPPH free radicals followed by SCB, SCR and SCL extracts. The effect of different extracts on the oxidative stability of sunflower oil at 70 °C was tested in the dark and compared with BHA. The oil peroxide values (PVs) were generally lower with the addition of extract in comparison to a control. [source] Chemical composition and toxic trace element composition of some Nigerian edible wild mushroomsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2008Olumuyiwa S. Falade Summary Two essential amino acids (methionine and tryptophan); anti-nutritional factors (tannin and trypsin inhibitor) and toxic elements (Pb, Cd, Ni, As, Hg and Cr) were determined spectrophotometrically from five edible wild mushrooms. The tryptophan content was between 1.00 and 1.82 g (100 g),1 but methionine was low at 0.26,1.38 g (100 g),1. Tannin content was high (30.3,40.0 mg g,1) but trypsin inhibitor was low (22.0,39.5 TIU g,1). Trace elements analysis reviled Pb (0.34,5.06 mg kg,1) to be the highest of all the trace elements. Cd was (0.06,1.70 mg kg,1), Ni (0.26,2.08 mg kg,1), As (0.17,0.92 mg kg,1), Hg (0.01,0.05 mg kg,1) and Cr (0.04,0.22 mg kg,1). These mushrooms are nutritious but must be well processed to eliminate or at least reduce the levels of tannin and Pb to improve their nutritional values. [source] Effect of galactose and glucose on the exopolysaccharide production and the activities of biosynthetic enzymes in Lactobacillus casei CRL 87JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2001F. Mozzi Aims: The objective of this work was to study the influence of the sugar source on exopolysaccharide (EPS) production and the activities of the enzymes involved in the synthesis of sugar nucleotides in Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined. Methods and Results: The concentration of EPS was estimated by the phenol/sulphuric acid method while the chemical composition of purified EPS was investigated using gas-liquid chromatography. Biosynthetic enzyme activities were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. Polysaccharide production by Lb. casei CRL 87 was 1·7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS, mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain. Conclusions: The carbon source present in the culture medium affects EPS production by Lb. casei CRL 87. The greater polymer synthesis by galactose-grown cells is correlated with the higher UDP-glucose-pyrophosphorylase, dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities. Initial sugar metabolism is also an important step for the synthesis of EPS precursors by this strain. Significance and Impact of the Study: Knowledge of the effect of the sugar source on EPS production and the activities of biosynthetic enzymes provides information about the mechanisms of regulation of the synthesis of EPS which can contribute to improving polymer production. [source] Effect of selected alcohol dehydrogenase inhibitors on human hepatic lactate dehydrogenase activity , an in vitro studyJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2005Jaroslaw Dudka Abstract Metabolic acidosis severely complicates methanol and ethylene glycol intoxications. Acidosis is caused by acid metabolites and can be intensified by lactate elevation. Lactate concentration depends on the NADH2/NAD ratio. Lactate dehydrogenase (LDH, E.C.1.1.1.27.) supplies more lactate when the level of NADH2 is elevated. The aim of the study was to evaluate the effect of alcohol dehydrogenase (ADH) inhibitors and substrates: cimetidine, EDTA, 4-methylpyrazole (4-MP), Ukrain and ethanol on LDH activity. The activity of LDH was determined spectrophotometrically in human liver homogenates incubated with cimetidine, EDTA, 4-MP and Ukrain at concentrations of 2 × 10,6, 10,5 and 5 × 10,5m as well as ethanol at concentrations of 12.50, 25.00, 50.00 mm. The LDH activity was significantly increased by 10,5 and 5 × 10,5m concentrations of cimetidine and 4-MP, and by all concentrations of ethanol. The most effective change of LDH activity of about 26% (P < 0.01) was observed at the highest concentration of ethanol. Ukrain inhibited LDH activity at both concentrations, i.e. 10,5 and 5 × 10,5m (P < 0.05). However, EDTA did not significantly influence LDH activity. The data showed that ethanol and 4-MP, the main antidotes in methanol or ethylene glycol poisoning, may increase liver LDH activity , an undesirable effect during the therapy of patients intoxicated with these alcohols. On the other hand, the decrease of LDH activity in the presence of Ukrain is a promising finding but definitely requires further investigation. Copyright © 2005 John Wiley & Sons, Ltd. [source] Solute crystallization in mannitol,glycine systems,implications on protein stabilization in freeze-dried formulationsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2003Abira Pyne Abstract The use of mannitol in combination with glycine has resulted in stable freeze-dried protein formulations. Our objectives were to (1) study solute crystallization in ternary systems containing mannitol, glycine, and water during all the stages of freeze drying as a function of processing conditions and formulation variables; (2) investigate the effect of sodium phosphate buffer salts on the crystallization of both mannitol and glycine and vice versa; and (3) investigate the effects of these excipients in a freeze-dried lactate dehydrogenase (LDH) formulation. X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC) were used to study the frozen aqueous solutions. Phase transitions during primary and secondary drying were monitored by simulating the entire freeze-drying process in situ in the sample chamber of the diffractometer. LDH activity after freeze drying was determined spectrophotometrically. In frozen aqueous solutions containing mannitol and glycine, each solute influenced the extent of crystallization of the other. The solutes crystallized as ,-mannitol and ,-glycine during primary drying. Glycine had a stronger tendency to crystallize, while it was easier to influence mannitol crystallization. The buffer salts inhibited the crystallization of mannitol and glycine. However, in some cases, during primary drying, glycine crystallization was followed by that of disodium hydrogen phosphate dodecahydrate. The latter underwent dehydration forming an amorphous anhydrate. It was possible to correlate the extent of crystallization of mannitol and glycine in the lyophile with the retention of protein activity. An increase in buffer concentration decreased the crystallinity of mannitol and glycine. This translated to increased retention of protein activity. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2272,2283, 2003 [source] PHYSICAL, SENSORY AND CHEMICAL EVALUATION OF COOKED SPAGHETTIJOURNAL OF TEXTURE STUDIES, Issue 6 2007CRISTINA S. MARTINEZ ABSTRACT The objectives of this research were to estimate the ability of chemical analysis, cooking properties, sensory evaluation and instrumental texture assays as descriptive quality parameters, and to evaluate the association between sensory and instrumental measurements on commercial pasta samples. Five commercial samples, Com1 to Com5, were analyzed. Moisture, protein and ash contents were determined from raw materials, while cooking loss, water absorption and leached amylose were measured in cooked samples. Color parameters (L*, a* and b*) were determined spectrophotometrically and color scores were calculated from raw and cooked samples. Three instrumental texture assays by a texture analyzer (TA-xT2i) and seven sensory parameters were evaluated. Chemical analysis, cooking properties, sensory evaluation and texture measurement were found to be sensitive quality parameters. From the analysis of the results, Com1 showed the best quality. A significant relationship between the sensory and instrumental measurements according to Pearson correlation and the principal component analysis was also observed. PRACTICAL APPLICATIONS In this work, the quality of different commercial pastas was assessed by means of chemical analysis, cooking properties, sensory evaluation and instrumental texture. The goal of this study was to identify the most important determinations related to pasta quality, and it allowed the establishment of the relationship between the sensory properties and texture measurements. [source] Activity of NADPH-Cytochrome P-450 Reductase of the Human Heart, Liver and Lungs in the Presence of (-)-Epigallocatechin Gallate, Quercetin and Resveratrol: An in vitro StudyBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2005Jaroslaw Dudka The enzyme is also involved in the toxicity of some clinically important antitumour drugs (doxorubicin) and pesticides (paraquat). P-450 reductase activates them to their more toxic metabolites via one electron reduction which triggers free radical cascade. In some cases however, such transformation is essential to produce therapeutic effect in anticancer drugs. The main purpose of the paper was to evaluate the effect of three natural compounds found in human diet: (-)-epigallocatechin gallate (EGCG), quercetin and resveratrol on P-450 reductase activity. The activity of the enzyme was determined spectrophotometrically by measurement of the rate of cytochrome c reduction at 550 nm, in vitro, using human heart, liver and lung microsomes. It was found that quercetin increased the P-450 reductase activity in human organs at all tested doses. The activity of microcosms in all organs was enhanced according to the concentrations of quercetin, which increased the activity in the order lung>heart>liver. Addition of EGCG to the reaction mixture enhanced the P-450 reductase activity in the following order: liver>heart>lung. However, no significant effect of resveratrol on P-450 reductase activity was observed. It seems that the presence of quercetin and EGCG in the diet may increase P-450 reductase activity during doxorubicin therapy with subsequent increased risk of toxicity. A beneficial effect may be obtained in anticancer therapy with bioreductive agents like tirapazamine. [source] Oxidation of carotenoids by heat and tobacco smokeBIOFACTORS, Issue 1 2004John S. Hurst Abstract The stability to autoxidation of the polar carotenoids, lutein and zeaxanthin, was compared to that of the less polar carotenoids, ,-carotene and lycopene at physiologically or pathophysiologically relevant concentrations of 2 and 6 ,M, after exposure to heat or cigarette smoke. Three methodological approaches were used: 1) Carotenoids dissolved in solvents with different polarities were incubated at 37 and 80°C for different times. 2) Human plasma samples were subjected to the same temperature conditions. 3) Methanolic carotenoid solutions and plasma were also exposed to whole tobacco smoke from 1,5 unfiltered cigarettes. The concentrations of individual carotenoids in different solvents were determined spectrophotometrically. Carotenoids from plasma were extracted and analyzed using high performance liquid chromatography. Carotenoids were generally more stable at 37 than at 80°C. In methanol and dichloromethane the thermal degradation of ,-carotene and lycopene was faster than that of lutein and zeaxanthin. However, in tetrahydrofuran ,-carotene and zeaxanthin degraded faster than lycopene and lutein. Plasma carotenoid levels at 37°C did not change, but decreased at 80°C. The decrease of ,-carotene and lycopene levels was higher than those for lutein and zeaxanthin. Also in the tobacco smoke experiments the highest autoxidation rates were found for ,-carotene and lycopene at 2 ,M, but at 6 ,M lutein and zeaxanthin depleted to the same extent as ,-carotene. These data support our previous studies suggesting that oxidative stress degrade ,-carotene and lycopene faster than lutein and zeaxanthin. The only exception was the thermal degradation of carotenoids solubilized in tetrahydrofuran, which favors faster breakdown of ,-carotene and zeaxanthin. [source] Nucleophilicities and Carbon Basicities of PyridinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Frank Brotzel Dipl.-Chem. Abstract Rate and equilibrium constants for the reactions of pyridines with donor-substituted benzhydrylium ions have been determined spectrophotometrically. The correlation equation log,k(20,°C)=s(N+E), in which s and N are nucleophile-specific parameters and E is an electrophile-specific parameter, has been used to determine the nucleophilicity parameters of various pyridines in CH2Cl2 and aqueous solution and to compare them with N of other nucleophiles. It is found that the nucleophilic organocatalyst 4-(dimethylamino)pyridine (DMAP) and tertiary phosphanes have comparable nucleophilicities and carbon basicities despite widely differing Brønsted basicities. For that reason, these reactivity parameters are suggested as guidelines for the development of novel organocatalysts. The Marcus equation is employed for the determination of the intrinsic barriers of these reactions. Geschwindigkeits- und Gleichgewichtskonstanten der Reaktionen von Pyridinen mit Donor-substituierten Benzhydrylium-Ionen wurden spektralphotometrisch bestimmt. Die Korrelationsgleichung log,k(20,°C)=s(N+E), die mit s und N Nucleophil-spezifische und mit E einen Elektrophil-spezifischen Parameter enthält, wurde verwendet, um die Nucleophilie-Parameter von verschiedenen Pyridinen in CH2Cl2 und in wässrigen Lösungen zu bestimmen und um diese mit N anderer Nucleophile zu vergleichen. Es wurde gefunden, dass der nucleophile Organokatalysator 4-(Dimethylamino)pyridin (DMAP) und tertiäre Phosphane vergleichbare Nucleophilien und Kohlenstoffbasizitäten haben, obwohl ihre Brønsted-Basizitäten sehr unterschiedlich sind. Daher wird vorgeschlagen, die Reaktivitätsparameter als Richtgrößen zur Entwicklung neuer Organokatalysatoren heranzuziehen. Die Marcus-Gleichung wird eingesetzt, um die intrinsischen Barrieren dieser Reaktionen zu bestimmen. [source] Use of regression methods for determining the relation between theoretical,linear and spectrophotometrical colour values of bicolour woven structuresCOLORATION TECHNOLOGY, Issue 2 2009Helena Gabrijel In this paper, new approaches for evaluating the entire colour effect of optical mixing of bicolour woven structures are presented. Simple woven structures with constant colour in the warp direction and different colours in the weft direction were prepared and analysed. The constructional parameters of these woven fabrics were systematically changed, which resulted in the variations of the fractions of colour components and, consequently, also in the changes of colour properties (lightness, hue, chroma) of bicolour optical mixtures. The position of colours of the bicolour structures and the approximate direction (linear) of colour changes in CIELAB colour space were theoretically determined with a simple geometrical model and additive method. Furthermore, the bicolour optical effects were determined spectrophotometrically. The differences between the linear,theoretical and the spectrophotometrical colour values of bicolour woven fabrics were mathematically analysed with linear and non-linear regression methods to determine the positions of colour coordinates L*, a* and b* of bicolour woven fabrics in the a*b* plane by increasing or reducing the cover factors of warp and weft threads (addition or reduction of colour components). The results present, on the one hand, the strong influence of original colours of warp and weft threads and, on the other hand, the minor influence of constructional parameters on the form of linear/non-linear behaviour of colours of bicolour compositions. When the characteristics of a specific colour combination are taken into account, the spectrophotometrical colour values of bicolour woven fabrics can be also mathematically determined with additive,theoretical colour values and, to some extent, with predictable colour deviations. [source] | ||||||||||||||||