High-performance liquid chromatographic monitoring of metabolic products resulting from the treatment of mouse hepatoma cells with N6-cycloalkylated nucleosides.

High-performance liquid chromatography was used to analyze cell lysates and growth medium of mouse hepatoma cells, separately treated with N6-cyclopropyl-, N6-cyclobutyl-, and N6-cyclopentyladenosines, in an effort to gain insight into the mechanism by which these modified nucleosides exert their cytotoxic effect(s). The corresponding 5'-monophosphate of the respective modified nucleoside was detected in the separate cell lysate samples. Both the modified nucleoside and its corresponding 5'-monophosphate were detected in the separate growth medium samples and their relative concentrations therein were determined. These results indicate that the cytotoxicity of these N6-cycloalkylated nucleosides may be attributed to their 5'-monophosphates within the cells.     

Enthalpies of dilution of urea solutions in six polar solvents at several temperatures

Using the isothermal displacement calorimeter, enthalpies of dilution are obtained for solutions of urea in water, methanol, ethanol, formamide, N,N-dimethyl-formamide, and dimethyl sulfoxide. The results are discussed in terms of solute-solvent and solute-solute interactions.Now Diane Beaumont.     

Flow-resonant sound interaction in a duct containing a plate,part I: Semi-circular leading edge

The interaction between flow and flow-induced acoustic resonances near rigid plates with semi-circular leading edges located in a hard-walled duct is described. These plates generate acoustic resonances over flow velocity ranges depending on thickness, chord and trailing edge geometry, together with rigidity, internal dimensions, length of the working section and shape of the terminations of the working section. A potential flow model for the plate with a smooth leading edge is developed, and the acoustic power generated by vortices growing and shedding from the trailing edge is calculated. The rate of growth of the vortices is determined by an instantaneous Kutta condition applied over part of the cycle. This technique simulates the influence of the sound field on vortex growth.     

Some results on the analysis of asymmetric stress

The structure of the principal directions of stress is characterized for the general case of asymmetric stress. It is shown that, for asymmetric stress, the principal directions can comprise either only one direction, or only two directions, or only three directions, or a plane of directions, or a plane of directions together with a direction external to this plane. The asymmetric stress obtained by combining a one-dimensional stress field with a skew-symmetric stress field is analyzed in detail.     

Self-assembled bismuth nanocrystallites

Using a high-temperature organic solution reduction method, highly crystalline and single domain bismuth nanoparticles have been synthesized and self-assembled.     

Capabilities of HPLC with APEX-Q nebulisation ICP-MS and ESI MS/MS to compare selenium uptake and speciation of non-malignant with different B cell lymphoma lines

The formation of intracellular dimethylselenide (DMSe) as a product of exposure of non-malignant (PBMCs) and lymphoma (RL and DHL-4) cell lines to methylseleninic acid (MSA) at clinical levels is suggested here for the first time. This was achieved by analysis of cell lysates by HPLC coupled to ICP-MS via APEX-Q nebulisation, enabling limits of detection for target methyl-Se species which are up to 12-fold lower than those obtained with conventional nebulisation. Methyl-Se-glutathione (CH₃Se-SG), although detected in lysates of cells exposed to MSA, was found to be a reaction product of MSA with glutathione. This was confirmed by HPLC-ESI MS (MS) analysis of lysates of control cells (unexposed to Se) spiked with MSA. The MS/MS data obtained by collision-induced dissociation fragmentation of the ion m/z 402 (for [M+H]^{+ 80}Se) were consistent with the presence of CH₃Se-SG. Formation of DMSe was not detected by HPLC-ICP-MS in these spiked lysates, and it was found to require live cells in cell media containing MSA. Interestingly, the ratio of DMSe to CH₃Se-SG was significantly higher in lymphoma cells exposed to MSA in comparison to non-malignant cells. Moreover, maximum Se uptake levels in lymphoma cell lines seemed to be reached much earlier (after 10 min of MSA exposure) than in non-malignant cells. Finally, the GC-TOF-MS speciation data obtained for cell headspace suggested that the major Se species (dimethyldiselenide) appeared to be present in lymphoma cell headspace at significantly higher concentrations than in non-malignant cell headspace after only 10 min of exposure to MSA. Evidence for the presence of dimethylselenidesulfide in lymphoma cell headspace is also provided for the first time.     

A quadruply-bonded [Cr2(guanidinate)4]4- tetraanion

The reaction of chromocene, Cp(2)Cr, with dilithiated 2,3-diphenylguanidine [(PhNH)(2)C=NH = L(2)H(3)] gives the novel, quadruply-bonded tetraanion [Cr(2)(L(2)H)(4)](4-).