Column-switching high-performance liquid chromatographic analysis of BO-2727, a new carbapenem antibiotic, in human plasma and urine by direct injection

A column-switching high-performance liquid chromatographic method has been developed for the simple and sensitive analysis of BO-2727 (I) in human plasma and urine. Plasma samples were diluted with an equal volume of a stabilizer, and the mixture was directly injected onto the HPLC system. The analyte was enriched in a pre-treatment column, while endogenous components were eluted to waste. The analyte was then backflushed onto an analytical column and quantified with ultraviolet detection. Urinary concentrations were determined in a similar way except that the enriched analyte was eluted in the foreflush mode to a cation-exchange column used for chromatographic separation. The standard curves for the drug were linear in the range of 0.05–50 μg/ml in plasma and 0.5–100 μg/ml in urine. The limits of quantification for plasma and urine were found to be 0.05 μg/ml and 0.5 μg/ml, respectively. This method was used to support Phase I clinical pharmacokinetic studies.     

Stolephorus insignus,a new anchovy from the western Pacific,and redescription of Stolephorus apiensis (Jordan and Seale 1906) (Clupeiformes: Engraulidae)

Ichthyological Research - Stolephorus insignus sp. nov. is described from 10 specimens from Taiwan, the Philippines, and the Moluccas, Indonesia. The new species is closely related to S. apiensis...     

The interaction of L-ascorbic acid with the active center of myrosinase.

Only L-ascorbic acid activated plant myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1), whereas ascorbic acid analogs did not. The enzyme protein was conformationally changed by the addition of L-ascorbic acid to the spectrophotometric analysis, approx. 1.5 amino residues appeared on the surface of the enzyme and about 2.3 tryptophan residues were buried in the molecule when 1 mM L-ascorbic acid was added. Optimum temperature for the myrosinase activity was approx. 55 degrees C without L-ascorbic acid, but with L-ascorbic acid it was about 35 degrees C; that for beta-glucosidase activity was the same (55 degrees C) with or without L-ascorbic acid. The effect of chemical modification of the functional groups of myrosinase on the interaction of L-ascorbic acid was investigated and the interaction of L-ascorbic acid with the active center of the enzyme is proposed.     

BLADE-ON-PETIOLE genes are not involved in the transition from protonema to gametophore in the moss Physcomitrella patens

Journal of Plant Research - The timing of the transition between developmental phases is a critical determinant of plant form. In the moss Physcomitrella patens, the transition from protonema to...     

Measurement of iodide in urine using the iodide-selective ion electrode

A simple and rapid way to measure the concentration of iodide in urine with an iodide-selective ion electrode was described. Potentiometric equilibrium was attained in less than 5 min, and a linear calibration curve was obtained over the potassium iodide (KI) concentration range of 10(-2) to 10(-6) M. The coefficients of variation ranged from 6.2 to 10.0% within assay, and 5.4 to 14.4% between assays. The serial dilution of 3 urine samples with different concentration of iodide showed good linear correlations passing through zero. In practice, the chloride ions in urine did not cause serious errors in the measurement of iodide at molar ratios of chloride ion to iodide up to 2 X 10(4). A good linear correlation was obtained between iodide concentrations in urine determined by the electrode method and by the conventional chemical method (r = 0.92). A linear correlation was also observed between the iodide concentrations of 24 h collected urine and those of single morning urine (r = 0.91). The normal iodide content in single morning urine specimens from 127 Japanese people was 5.3 to 62.0 X 10(-6) moles/g creatinine.     

Effects of Site-directed Mutagenesis of Conserved Lys606 Residue on Catalytic and Regulatory Functions of Maize C4-form Phosphoenolpyruvate Carboxylase

Lys606, one of the two highly conserved lysine residues in maizeC₄-form phosphoenolpyruvate carboxylase (PEPC), was convertedto Asn, GIu or Arg by site-directed mutagenesis. Resulted mutantenzymes expressed using pET system [Dong, L.-Y. et al (1997)Biosci. Biotech. Bio-chem. 61: 545] were purified by one stepprocedure through nickel-chelate affinity chromatograghy toa purity of about 95%. The replacement of Lys606 by Arg hadlittle effect on the kinetic and allosteric properties of theresulting mutant enzyme. In contrast, the maximum velocities(V_max were decreased to 22% and 2% of that of wild-type PEPCupon the substitution of Lys606 by Asn and Glu, respectively.The value of S_0.5(HCO^–₃) was increased 21—25 foldby the replacements, whereas the S_0.5(Mg²⁺) and S_0.5(PEP) valueswere increased only 5—8 fold. The extents of activationof mutant enzymes by glucose 6-phosphate and glycine were 2to 3-fold higher than those of wild-type enzyme. The mutantenzymes showed less sensitivity to malate inhibition, comparedwith the wild-type enzyme. The results suggested that the Lys606is not obligatory for the enzyme activity, but may be involvedin the bicarbonate-binding and contribute somehow to the allostericregulatory properties. (Received June 12, 1997; Accepted October 1, 1997)