Chemotaxis in Methanospirillum hungatei

Methanospirillum hungatei gave a positive chemotactic response to acetate.     

N-succinimidyl methoxyphenylacetic acid ester, an amine-directed chiral derivatizing reagent suitable for enzymatic scale resolutions

A chiral derivatizing reagent, N-succinimidyl-2-(S)-methoxy-2-phenylacetic acid ester (SMPA), directed toward reaction with primary amine-containing compounds has been synthesized and characterized. This reagent is suitable for HPLC resolution from enzymatic-scale reactions where only microgram quantities of chiral products may be obtainable. SMPA derivatization was shown to be effective in the resolution of the enantiomers of a number of different racemic compounds. SMPA was used to resolve the diastereoisomeric derivatives of a previously unknown enzymatically oxygenated product, allowing determination of the stereochemical course of the enzymatic reaction. SMPA is easily prepared from an inexpensive, commercially available, and enantiomerically pure precursor with the formation of a shelf-stable crystalline product which is utilizable in water-containing solutions. In addition to its usefulness for micro-determinations, SMPA is useful for preparative-scale resolutions of enantiomers since the reagent is cleaved from the diastereoisomeric derivative by acid hydrolysis.     

Instability of orthophthalaldehyde reagent for amino acid analysis

Determination of amino acids by reversed-phase chromatography of the adduct with orthophthalaldehyde and a thiol is rapid and sensitive. The major recognized adverse feature of this method is the instability of the reaction product, which requires precise control of reaction timing and chromatographic parameters for reliable quantitative application. We report another source of major variability: reagent instability. Deterioration of reagent was noted as low peak heights and peak broadening and was predictable if the premixed reagent was left at room temperature. Restoration of sharp chromatograms was accomplished by addition of mercaptoethanol or sodium metabisulfite. Reagent which was chromatographically inert contained minimal free thiol by direct assay. Free thiol disappearance was markedly slowed by addition of a chelating agent. Excess mercaptoethanol was deleterious. We conclude that reagent deterioration represents oxidation of the thiol, may be reversed by rereduction with minimal thiol or bisulfite, and may be minimized by inclusion of a metal chelator in the reagent.     

Segmentation and moral status in vivo and in vitro: a scientific perspective

A basic consideration in research on human embryos is the controversy about when the embryo acquires moral status. The author refutes the contention that segmentation is the determinant of moral status. She notes that segmentation, as a stage in embryonic development, does not coincide with the development of "irreversible individuality" upon which the segmentation argument depends. Dawson also finds a lack of clarity in the meaning of "individuality." These problems, she maintains, prevent segmentation from being morally important and render the proposed 14-day limit on embryo research unnecessary. Dawson concludes that to introduce a time restriction on embryo research is premature because it is based on an inadequate philosophical argument.     

In vitro detachment of bacteria from ruminal digesta by buffered sodium oleate solutions

The effectiveness of a buffered sodium oleate solution was evaluated for detaching bacteria from ruminal digesta samples. A response surface derived from an octagonal design was used to determine the pH and concentration combination for maximum detachment of total and cellulolytic bacteria. The total number of bacteria detached increased up to 81% over control with treatment of a pH 8.8 and 1.5% sodium oleate solution. The recovery of cellulolytic bacteria was decreased to 35% of control with treatment of a pH 9.0 and 0.1% sodium oleate solution. Attempts to improve the recovery of viable bacteria exposed to sodium oleate solutions were unsuccessful. This response surface design identified an optimal pH and concentration that were consistent with existing information regarding detachment of total bacteria, and suggested that sodium oleate, at the concentrations tested, was toxic to the cellulolytic population of the rumen.