Diffusion of Cesium Ions in Agar Gel Containing Alkali Metal Bromides

The present paper gives an account of different aspects of the tracer diffusion of Cs⁺ ions in alkali metal bromides. We have measured the diffusion coefficients, D, of cesium ions in 1% agar gel medium at 25 ^∘C using a zone-diffusion technique over a concentration range of 5 × 10⁻⁵ to 0.1 mol,dm⁻³. The values of the diffusion coefficients were found to deviate from theory, which are explained on the basis of different types of interactions occurring in the ion-gel-water system. The study is also focused on the effect of alkali metal bromides on the obstruction effect and activation energy for the tracer-diffusion of cesium ions in agar gel medium. It is observed that both parameters, extent of obstruction, ∝, and activation energy, E, decrease with increasing charge density of the cation of the supporting electrolyte. The influence of these trends is explained on the basis of competitive hydration between the ions and agar molecules, and the relative distortion in the water structure that is brought about by these different ions and agar molecules.     

Separation and identification of organic acid-coenzyme A thioesters using liquid chromatography/electrospray ionization-mass spectrometry

A method has been developed for the direct determination of coenzyme A (CoA) and organic acid-CoA thioesters in mixtures using directly combined liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). Mixtures of CoA and organic acid-CoA thioesters were analyzed by LC/ESI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of the CoA-thioesters were established based on LC retention times and simultaneously recorded mass spectra. Monitoring of the CoA specific fragment ion at m/z 428 throughout the chromatogram provides a unique fingerprint for CoA content in the samples that corroborates the identification of organic acid-CoA thioesters in the mixtures. Furthermore, fragment ions arising from the ester linkage portion of the molecule allow unambiguous identification of the CoA esters in the samples. A second LC elution system was developed that allows the simultaneous separation and identification of 2-hydroxypropionyl-CoA (lactyl-CoA) and 3-hydroxypropionyl CoA (3HP-CoA), which have the same mass and identical MS fragmentation behavior. The utility of LC/ESI-MS employing this elution system is demonstrated by the determination of 3HP-CoA and lactyl-CoA (converted to CoA-thioesters from their corresponding free acids using CoA-transferase) in fermentation broths from Escherichia coli strains engineered for the production of 3-hydroxypropionic acid (3HP). External calibration employing a purified 3HP-CoA standard allowed indirect quantification of 3HP content in the broth with a precision of 1% (RSD). The feasibility of extending the method described above to perform LC/selected reaction monitoring-tandem mass spectrometry for direct determination of organic acid-CoA thioesters in cells was also demonstrated.     

HPTLC Method for Quantification of Apigenin in the Dried Root Powder of Gmelina arborea Linn.

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive high-performance thin-layer chromatographic method has been established for quantification of apigenin in dried root...     

Deactivation of jack bean urease in urea hydrolysis

Deactivation studies of jack bean urease immobilized on porous alumina beads in the hydrolysis of urea were conducted in a continuously stirred tank reactor (CSTR) at a temperature of 25°C and pH 7.0. Though the mechanism of poisoning of urease by product ammonia is fairly well understood from the literature, the nature of the poisoning of urease by urea is presented in this article. These studies were conducted by adsorbing the ammonia formed in the hydrolysis reaction. The results indicate that, in the presence of the adsorbent Zeolite W, the deactivation rate is reduced by a factor of almost two, and thus provide a technique for prolonging the life of the enzyme. The deactivation model suggests that the free form of the enzyme is most susceptible to attack by the substrate urea. The experimental data suggest that deactivation by combined ammonia and urea is fairly complex.     

HPTLC Quantitation of Camptothecin in Nothapodytes foetida (Wight) Sleumer Stem Powder

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive and reliable high-performance thin layer chromato-graphic method has been developed for quantitation of camp-tothecin...     

Diffusion of Cesium Ions Labeled with 134 Cs in Agar Gel Containing Alkali Metal Iodides: Obstruction Effect and Activation Energy

The effect of some alkali metal iodides on the obstruction effect and activation energy for tracer-diffusion of cesium ions in an agar gel medium was studied using the zone-diffusion technique. It to be observed that both the extent of obstruction (α) and the activation energy (E) decrease with the increasing charge density of the cation of the supporting electrolyte. These trends are explained on the basis of competitive hydration between ions and agar molecules and the relative distortion in the water structure that is brought about by these different ions and agar molecules, respectively.     

Production of succinate from glucose, cellobiose, and various cellulosic materials by the ruminai anaerobic bacteriaFibrobacter succinogenes andRuminococcus flavefaciens

The production of organic acids by two anaerobic ruminal bacteria,Fibrobacter succinogenes S85 andRuminococcus flavefaciens FD-1, was compared with glucose, cellobiose, microcrystalline cellulose, Walseth cellulose (acid swollen cellulose), pulped paper, and steam-exploded yellow poplar as substrates. The major end product produced byF. succinogenes from each of these substrates was succinate (69.5–83%), the principal secondary product was acetate (16–30.5%). Maximum succinate productivity ranged from 14.1 mg/L · h for steam-exploded yellow Poplar to 59.7 mg/L · h for pulped paper. ForR. flavefaciens, the major end product from cellobiose, microcrystalline cellulose, and acid-swollen Walseth cellulose was acetate (39–46%), pulped paper and steam-exploded yellow poplar yielded succinate (42–54%) as the major product. Maximum succinate productivity byR. flavefaciens ranged from 9.21 mg/L · h for cellobiose to 43.1 mg/L · h for pulped paper. In general, much less succinate was produced at a lower maximum productivity byR. flavefaciens than byF. succinogenes under similar fermentation conditions. The maximum succinate productivities by these two organisms are comparable to the previously reported value of 59 mg/L · h forAnderobiospirillum succiniciproducens grown on glucose and corn steep liquor.     

Application of NAA in diffusion studies

The diffusion of Mn₂+ ions in CoSO₄ , NiSO₄ and ZnSO₄ containing 1% agar gel as well as that of MnSO₄ in 1% agar gel was studied at 25 °C. The diffusion coefficientsat selected concentrations were determined by the zone diffusion techniqueand by measuring the concentration of diffusing ions using neutron activationanalysis.