Kinetics of the reaction of U(VI) with benzene-1,2-diphosphonic acid

The kinetics of the reaction between dioxouranium(VI) and benzene-1,2-diphosphonic acid (BzDPA) has been investigated by stopped-flow spectrophotometry. The rate of reaction of uranyl ions with Arsenazo III (2,7-bis(2,2'-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid) in 50:50 methanol-water solutions was also determined. Both formation and dissociation rate constants for the 1:1 complex between uranyl-BzDPA in acidic solutions were resolved. To gain insight into the effect of solvation on the progress of the reaction, the system was studied in triply distilled water, in 50:50 methanol-water, 80:20 methanol-water and in 50:50 tert-butanol-water as a function of temperature at pH 1.0. The rates of complex formation and dissociation reactions decrease as methanol substitutes for water in the medium and further decrease as tert-butanol replaces methanol as co-solvent. Activation parameters are most consistent with an associative process governing the progress of both complex formation and dissociation reactions. Introduction of alcoholic co-solvents results in notably more negative activation entropies for both complex formation and dissociation reactions, while the activation enthalpies are only slightly reduced in the mixed methanol-water medium. These results are compared with the kinetic features of other U(VI) systems.     

Synthesis and Structural Studies of Porous Organobridged Silicate Amorphous Powder

Novel amorphous organobridged polysilsesquioxane porous powders have been prepared via hydrolytic precipitation from solutions of 1,4-bis(trichlorosilylmethyl)benzene. These new porous materials have been characterized by SEM, nitrogen sorption measurements and solid state 13C and 29Si NMR spectroscopy. The internal structure and porosity of the amorphous materials are correlated to the process conditions.     

Determination of ephedra alkaloids by liquid chromatography/tandem mass spectrometry

In conjunction with an AOAC Task Group on dietary supplements, a liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was validated for measurement of 6 major alkaloids in raw ephedra sinica herb, ephedra extracts, ephedra tablets, complex dietary supplements containing ephedra, and a high-protein drink mix containing ephedra. The amount of ephedrine-type alkaloids present was determined by LC with mass selective detection. Six replicates of each matrix were analyzed on 3 separate occasions. The presence of 6 ephedrine-type alkaloids was detected at a level > 0.5 microg/g based on a 0.5 g sample. The standard curve range for this assay is from 0.02 to 1.0 microg/mL. Appropriate dilutions covered a wide range of specific alkaloid concentrations. The calibration curves for all 6 analytes had correlation coefficients > 0.995.     

Vibrational spectra and normal coordinate analysis of germylazide-do and -d3

The infrared spectra (4000–20 cm^?1) of gaseous and solid GeH₃NNN and GeD₃NNN and the Raman spectra (3000–0 cm^?1) of liquid and solid GeH₃NNN and GeD₃NNN have been recorded. The vibrational spectrum has been assigned on the basis of C_s symmetry. The GeNN bend was observed in the Raman spectrum of the gas at ~150 cm^?1; however, the frequency of the GeH₃ torsion could not be determined. A normal coordinate calculation has been carried out by utilizing a modified valence force field. The GeN stretching force constant was found to have a significantly smaller value than the corresponding force constant in GeH₃NCO and GeH₃NCS. A considerable amount of mixing was found between the GeN stretch and the NNN in-plane bend. The frequencies of the normal modes and the normal coordinate analysis of GeH₃NNN are discussed in view of the recent results reported for GeH₃NCO and GeH₃NCS.     

Coexistence curve of 2,6-lutidine + water,near its lower critical point

Measurements of the refractive index of both phases of the mixture 2,6-lutidina + water, near the lower critical point, are reported. For T-T_c < 0.5 K, a simple power law, Δn = (0.0471±0.001)(T-T_c)^{(0.338±0.003)}, describes the data. For 0.5 K <T-T_c < 15 K, a decorated lattice model better describes the data.     

Determination of "net carbohydrates" using high-performance anion exchange chromatography

For labeling purposes, the carbohydrate content of foods has traditionally been determined by difference. This value includes sugars, starches, fiber, dextrins, sugar alcohols, polydextrose, and various other organic compounds. In some cases, the current method may lack sufficient specificity, precision, and accuracy. These are subsequently quantitated by high performance anion exchange chromatography with pulsed amperometric detection and expressed as total nonfiber saccharides or percent "net carbohydrates." In this research, a new method was developed to address this need. The method consists of enzyme digestions to convert starches, dextrins, sugars, and polysaccharides to their respective monosaccharide components. These are subsequently quantified by high-performance anion exchange chromatography with pulsed amperometric detector and expressed as total nonfiber saccharides or percent "net carbohydrates." Hydrolyzed end products of various novel fibers and similar carbohydrates have been evaluated to ensure that they do not register as false positives in the new test method. The data generated using the "net carbohydrate" method were, in many cases, significantly different than the values produced using the traditional methodology. The recoveries obtained in a fortified drink matrix ranged from 94.9 to 105%. The coefficient of variation was 3.3%.     

Synthesis of indolo[2,3-a]carbazole glycoside analogs of rebeccamycin: inhibitors of cyclin D1-CDK4

The synthesis and structure-activity relationships of a new series of indolo[2,3-a]carbazole glycosides, analogs of rebeccamycin, derived from the natural sugars (glucose, fucose, mannose, xylose, rhamnose, and galactose) is described.     

A rapid polymerase chain reaction method for identifying fixed specimens.

DNA profiling analysis of preserved tissue samples was achieved by using an extraction method which incorporated the use of a chelating resin "Chelex" to chelate inhibitory polyvalent metal ions. An automated sequencer was used to estimate sizes of low molecular weight trimeric and tetrameric microsatellites labelled with fluorescent dyes. The entire analysis can be completed within 48h. Probabilities of chance association using two microsatellites were calculated as ranging between 10(-2) and 10(-4). The methods described have considerable potential for use in routine genetic analysis of preserved samples.