Synthesis of protected derivatives of O-phosphotyrosine incorporation in a heptapeptide

The solid phase synthesis of the phosphopeptide Leu-Arg-Arg-Ala-Tyr(P)-Leu-Gly is reported via the stepwise incorporation of the protected phosphoamino acid Nα -tert-butyloxycarbonyl-O-dimethyl-phosphono-L-tyrosine.     

Indirect photomeric detection of anions in capillary electrophoresis using dyes as probes and electrolytes buffered with an isoelectric ampholyte

The use of highly absorbing anionic dyes as probes and isoelectric ampholytes as buffers in background electrolytes (BGEs) combined with the use of a light emitting diode (LED) as a light source has been studied for ultrasensitive indirect photometric detection in capillary electrophoresis (CE). Potential dyes and buffers were evaluated based on characteristics relevant to indirect photometric detection principles, such as the electrophoretic mobility of the probe dye, its solubility and adsorption behaviour, and the isoelectric point and buffering capacity of the ampholytic buffer. Two dyes, tartrazine and naphthol yellow S, and histidine as the ampholytic buffer, were selected for detailed investigation. Purification of the probes was vital to avoid anionic impurities interfering with the detection. For the electrolytes containing a purified probe (0.5 mM) and histidine as the isoelectric buffer (p/ 7.7), hydroxypropylmethyl cellulose (approximately 0.05%) was effective in suppression of the electroosmotic flow (EOF). Analytical method performance characteristics were determined. For both probes, experimentally determined mobilities were generally close to literature values, excellent peak shapes and separation efficiencies of up to 298 000 theoretical plates were obtained, and detection limits were generally at the sub-microM level. For the naphthol yellow S-histidine BGE, linearity and reproducibility were also evaluated, with excellent linearity being observed over a range of 5-500 microM, and reproducibility (relative standard deviation, RSD) less than 1% for migration times and 2-8% for normalised peak areas. The approach developed was applied successfully to several real samples including tap water, mineral waters, and beer.     

The theory of dispersion of chemically active solutes in a rectilinear flow field: The vector problem

In this paper and its sequel we seek an understanding of diffusion and reaction processes in multicomponent systems under convective conditions. To do this, we construct dispersion approximations to c, the solution of the vector convective diffusion equation, and to its transverse average, . Dispersion coefficients are not the direct route to dispersion approximations in the vector problem. Yet constant long time dispersion coefficients exist and imply a rearrangement of the Hermite expansion of . We deduce the rearrangement and introduce useful approximations thereto.     

Simultaneous determination of fluorine and chlorine in silicate rocks by a rapid spectrophotometric method

A rapid accuiate method is described for simultaneous determination of fluorine and chlorine in silicate rocks by taking, separate aliquots of the single sample dissolution. Fluorine, without separation, was determined by means of the zirconium-criochrome cyanine R complex, whereas chlorine was determined by means of the stable iron (III) thiocyanate complex. The mctliod was tested with standard rocks. Results with geochemical standards were comparable with analyses reported by others. Application to several acidic, mafic, and ultramafic rock samples, gave results with a relative standard deviation of less than 5 %.     

Tautomerism in the 5-pyrazolone series 1(H)-5-pyrazolones and indazolones

Structure (I) is shown to be the correct formulation for the compound hitherto considered to be the “azine” of ethyl acetoacetate; I rearranges to IV. Both IV, 1(H)-3-methyl, and 1(H)-3-phenyl, 5-pyrazolones and related compounds are shown to exist in the enolic form (VII) in the solid state and predominantly so in the solvents in which they are soluble. Similarly the indazolones are found to be represented exclusively by the enolized structure XII. The acetates of both series are reformulated where necessary on the basis of spectroscopic data, and the high frequencies found for the carbonyl groups in the IR are shown to reflect a lack of conjugation with the π-electrons of the heterocyclic ring.