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Reagent Concentrations (reagent + concentration)
Selected AbstractsDetermination of biogenic amines in HeLa cell lysate by 6-oxy-(N -succinimidyl acetate)-9-(2',methoxycarbonyl) fluorescein and micellar electrokinetic capillary chromatography with laser-induced fluorescence detectionELECTROPHORESIS, Issue 4 2006Liwei Cao Abstract An MEKC-LIF method using 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxy-carbonyl) fluorescein (SAMF) newly synthesized in our lab as a labeling reagent for the separation and determination of eight typical biogenic amines was proposed. After careful study of the derivatization condition such as pH value, reagent concentration, temperature, and reaction time, derivatization reaction was accomplished as quickly as 10,min with stable yield. Optimal separation of SAMF-labeled amines was achieved with a running buffer (pH,9.3) containing 30,mM boric acid, 25,mM SDS, and 20%,v/v ACN. The proposed method allowed biogenic amines to be determined with LODs as low as 0.25,2.5,nmol/L and RSD values from 0.4 to 4.5%. The present method has been successfully used to monitor biogenic amines in HeLa cells and fish samples. This study exploits the potential of MEKC-LIF with SAMF labeling as a tool for monitoring biogenic amines involved in complex physiological and behavioral processes in various matrices. [source] Fluoropolyethers end-capped by polar functional groups.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Abstract The kinetics of the dibutyltin dilaurate (DBTDL)-catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z-DOL H-1000 of various molecular weights (100,1084 g mol,1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30,60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl-containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero-order, first-order, second-order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771,3795, 2002 [source] Influence of oxidation and crosslinking on oxygen binding properties of mouse erythrocytesCELL BIOCHEMISTRY AND FUNCTION, Issue 2 2001L. A. Lotero Abstract Different chemical treatments for mouse erythrocyte modification has been used. Oxidation treatments with Ascorbate/Fe3+, a system able to react with intracellular proteins, produced a displacement of the O2 binding equilibrium curve to a higher affinity behaviour with loss of the haemoglobin cooperativity for oxygen binding. Incubation of mouse erythrocytes with diamide showed that at low reagent concentration (0.8,mM) no modification on oxygen binding equilibrium curves was observed. At higher reagent concentration (2.0,mM), an increased affinity and a disappearance of the cooperative behaviour can be observed. Additionally, crosslinking reactions on mouse erythrocytes with band 3 crosslinkers seemed to affect oxygen binding properties when used at a crosslinker concentration of 5,mM. Oxyhaemoglobin levels in crosslinked and diamide-treated erythrocytes are similar to those found in control cells. In contrast, ascorbate/Fe3+ treatments produced an increment in the proportion of methaemoglobin, decreasing the oxyhaemoglobin levels in these oxidized erythrocytes. Copyright © 2001 John Wiley & Sons, Ltd. [source] Analysis of dideoxyadenosine triphosphate by CE with fluorescence detection.ELECTROPHORESIS, Issue 21 2007Abstract A CZE method was developed, which separates 2,,3,-dideoxyadenosine-5,-triphosphate (ddATP) from other metabolites and endogenous nucleotides at high concentrations (20,200,,g/mL) to allow UV detection. To enhance sensitivity, fluorescence detection which requires prior derivatization of compounds was examined. Precapillary derivatization of ddATP in the presence of N -(3-dimethylaminopropyl)- N,-ethylcarbodiimide hydrochloride (EDAC) with dansyl ethylenediamine (dansyl EDA) was faster and stable compared to that of 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza- s -indacene-3-propionyl ethylenediamine (BODIPY FL EDA). Reaction conditions, reagent concentrations and detection parameters were optimized and highest derivatization efficiency was achieved in 0.1,M 1-methylimidazole buffer (pH,8.0) with 140,mM EDAC in 1-methylimidazole buffer and 30,mM dansyl EDA in DMF for 90,min at 60°C. Dansyl EDA derivatives of ddATP, 2,-deoxyadenosine-5,-triphosphate (dATP) and ATP were comigrating with the CZE method; therefore, a MEKC method was developed and optimized for repeatable separations. Upon dansylation, sensitivity of ddATP with fluorescence detection (LOQ,=,12,ng/mL) was 160 times higher than UV detection (LOQ,=,1.9,,g/mL). [source] Kinetic studies of hydrazine and 2-hydroxyethylhydrazine alkylation by 2-chloroethanol: Influence of a strong base in the mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2009V. Goutelle To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N2H4 by 2-chloroethanol (CletOH) was carried out with and without sodium hydroxide. In both cases, the main reaction of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or dialkylation of N2H4), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkylations followed SN2 reactions triggered directly by CletOH or indirectly in the presence of a strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the influence of a strong base present in the medium on the reaction mechanisms were established. A global mathematical treatment was applied for each alternative. It allowed modeling the reactions as a function of reagent concentrations and temperature. In the case of direct alkylation by CletOH, simulation was established for semi-batch and batch syntheses and was confirmed in experiments for concentrated mediums (1.0 M , [CletOH]0 , 3.2 M and 15.7 M , [N2H4]0 , 18.8 M). Simulation therefore permits the prediction of the instantaneous concentration of reagents and products, in particular ethylene oxide concentration in the case of indirect alkylation, which must be as weak as possible. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 382,393, 2009 [source] Separation of cobalt and nickel from acidic sulfate solutions using mixtures of di(2-ethylhexyl)phosphoric acid (DP-8R) and hydroxyoxime (ACORGA M5640)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2004Arisbel Cerpa Abstract DP-8R and ACORGA M5640 extractants diluted in Exxsol D100 were used to co-extract cobalt and nickel from aqueous acidic sulfate media. The influences of equilibration time, temperature, equilibrium pH and reagent concentrations on the extraction of both metals have been studied. It was observed that both cobalt and nickel extraction are slightly sensitive to temperature but are pH dependent. Metal extraction equilibria are reached within about 5 min contact time. In addition, cobalt extraction depends on the extractant concentration in the organic phase. For a solution containing 0.5 g dm,3 each of cobalt and nickel and an initial pH of 4.1, conditions were established for the co-extraction of both metals and selective stripping (with H2SO4) of cobalt and nickel. Using the appropriate reagent concentrations the yield (extraction stage) for both metals exceeded 90%, and stripping of cobalt and nickel was almost quantitative. Copyright © 2004 Society of Chemical Industry [source] A di(bisphosphonic acid) for protein coupling and targeting to boneJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2004Geeti Bansal Abstract Proteins intended for treatment of bone diseases should ideally exhibit a high bone affinity, so that they are preferentially deposited to bones after systemic administration. This can be achieved by combining molecules having a high affinity to bone with the proteins. Bisphosphonates (BPs) are chemical analogs of pyrophosphate that possess exceptional bone mineral affinity. To this end, we synthesized a novel BP, 3,5-di(ethylamino-2,2-bisphosphono)benzoic acid (6), which contains two BP moieties on a single molecule, unlike conventional BPs that contain one BP moiety per molecule. 6 was then conjugated to two model proteins, bovine serum albumin and nonspecific bovine immunoglobulin G by the carbodiimide chemistry. By varying the reagent concentrations, the conjugation efficiency (i.e., number of 6 per protein) was readily controlled under the experimental conditions. The protein- 6 conjugates exhibited an in vitro mineral affinity that was proportional to the number of conjugated 6. The 6 -conjugates of both bovine serum albumin and immunoglobulin G were found to be bone seeking in rats, based on the increased concentration of 6 -conjugated proteins in bone tissue after intravenous administration. We conclude that the novel BP synthesized (6) can serve as a carrier for bone delivery while reducing the extent of protein modification necessary for bone targeting. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2788,2799, 2004 [source] | |||||||||||||