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Various pH Conditions (various + ph_condition)
Selected AbstractsSubstrate Channelling in a Creatine Kinase System of Rat Skeletal Muscle Under Various pH ConditionsEXPERIMENTAL PHYSIOLOGY, Issue 1 2003M. Gregor The aim of this study was to evaluate myofibrillar creatine kinase (CK) activity and to quantify the substrate channelling of ATP between CK and myosin ATPase under different pH conditions within the integrity of myofibrils. A pure myofibrillar fraction was prepared using differential centrifugation. The homogeneity of the preparation and the purity of the fraction were confirmed microscopically and by enzymatic assays for contaminant enzyme activities. The specific activity of myofibrillar CK reached 584 ± 33 nmol PCr min,1 mg,1 at pH 6.75. Two methods were used to detect CK activity: (1) measurement of direct ATP production, and (2) measurement of PCr consumption. This method of evaluation has been tested in experiments with isolated creatine kinase. No discrepancy in CK activity between the methods was observed in the pH range tested (6.0-7.5). However, the same procedures resulted in a significant discrepancy between the amounts of reacted PCr and produced ATP within the pure myofibrillar fraction. This discrepancy represents the portion of ATP produced by the CK reaction, which is preferentially channelled to the myosin ATPase before diffusing into the bulk solution. The maximum evaluated difference reached 42.3 % at pH 6.95. The substrate channelling between myofibrillar-bound CK and myosin ATPase was evaluated under various pH levels within the physiological range and it reached a maximum value in a slightly acidic environment. These results suggest that ATP/ADP flux control by the CK system is more important at lower pH, corresponding to the physiological state of muscle fatigue. [source] Comparative evaluation of 99mTc-ethylene bis-l-cysteine and 99mTc-ethylene bis-l-,-homocysteine during reversed phase HPLC analysis and electrophoresis at various pH conditionsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2001K.O. Mang'era Ethylene bis- L -,-homocysteine (L,L -EH) differs from ethylene bis- L -cysteine (L,L -EC) in having an extra methylene group between each pair of amine and carboxyl groups. The objective of this study was to determine the effect of the extra methylene groups on the characteristics of the complex of these compounds with technetium-99m during analysis by reversed phase HPLC and by electrophoresis at various pH values. Up to pH 5.5, 99mTc- L,L -EH exhibits a substantially longer retention time during reversed phase HPLC than 99mTc- L,L -EC, suggesting a more lipophilic character for 99mTc- L,L -EH under these conditions. On the other hand, 99mTc- L,L -EH clearly possesses a higher negative charge in the pH range 3-6.5 as shown by the markedly greater migration towards the anode in electrophoresis experiments. A rational explanation for these seemingly opposing observations can not yet be offered. Copyright © 2001 John Wiley & Sons, Ltd. [source] Effect of pH on synthesis and properties of perovskite oxide via a citrate processAICHE JOURNAL, Issue 2 2006Zhentao Wu Abstract A series of La0.6Sr0.4Co0.4Fe0.6O3-, (LSCF) perovskite-type oxides were synthesized using a modified citrate process under various pH conditions (pH =1, 3, 5, 7, and 9, respectively). The effect of pH on the chelate process, crystal development, morphology, and oxygen permeability of LSCF oxides were investigated. FT-IR analysis showed that the chelate processes for pH = 1 and 3 were different from those for pH = 5, 7, and 9. XRD and SEM observations revealed that the crystal formation and morphology of LSCF oxides were dependent on the precursors with different pH conditions. The LSCF membranes derived from the precursors with lower pH values (pH = 1 and 3) exhibited larger apparent activation energy for oxygen permeation than the other samples (pH = 5, 7, and 9) in the range of 1073-1123K. This study indicated that properties such as crystallinity and oxygen permeability of LSCF oxide could be tailored by controlling the pH values in the synthesis process. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Effect of pH on the Carbonate Incorporation into the Hydroxyapatite Prepared by an Oxidative Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Yusuf Yusufoglu In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline-sodium and carbonate-containing calcium HAp (NaCO3HAp) powders were prepared using an oxidative decomposition of calcium,EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 ,m in diameter or hexagonal prismatic particles measuring 3,9 ,m in length were obtained. Various characterization techniques showed that the precipitates were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as-prepared samples are B-type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965°C, most of the carbonate is removed from the HAp lattice. [source] | ||||||||||