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1.
J Anal Toxicol ; 43(1): 36-44, 2019 Jan 01.
Article in English | MEDLINE | ID: mdl-30060005

ABSTRACT

Tris(chloropropyl)phosphate (TCPP) is an organophosphorus flame retardant (OPFR) and plasticizer increasingly used in consumer products and as a replacement for brominated flame retardants. Commercially available TCPP is a mixture of four structural isomers the most abundant of which is tris(1-chloro-2-propyl)phosphate (TCPP-1). Although there is a widespread use of TCPP and potential for human exposure, there is limited data on the safety or toxicity of TCPP. The National Toxicology Program is conducting long-term studies to examine the toxicity of the TCPP in rats after lifetime exposure, including perinatal oral exposure. Quantitative estimates of internal dose are essential to interpret toxicological findings in rodents. To aid in this, a method was fully validated to quantitate the most abundant isomer, TCPP-1, in female Harlan Sprague Dawley (HSD) rat and B6C3F1 mouse plasma with partial validation in male rat plasma, and male and female mouse plasma. The method used protein precipitation using trichloroacetic acid followed by the extraction with toluene, and analysis by gas chromatography with flame photometric detection. The performance of the method was evaluated over 5-70 ng TCPP-1/mL plasma. The method was linear (r ≥ 0.99), accurate (inter-day relative error: ≤ ± -7.2) and precise (inter-batch relative standard deviation: ≤27.5%). The validated method has lower limits of quantitation and detection of ~5 and 0.9 ng/mL, respectively, in female HSD rat plasma and can be used on samples as small as 50 µL demonstrating the applicability to plasma samples from toxicology studies.


Subject(s)
Chromatography, Gas/methods , Flame Retardants/analysis , Organophosphates/blood , Photometry/methods , Plasticizers/analysis , Animals , Calibration , Chromatography, Gas/standards , Female , Flame Ionization , Limit of Detection , Male , Mice , Photometry/standards , Rats, Sprague-Dawley , Reference Standards , Reproducibility of Results
2.
J Chromatogr A ; 652(2): 427-9, 1993 Oct 22.
Article in English | MEDLINE | ID: mdl-8287135

ABSTRACT

Capillary electrophoresis (CE) has proven to be an efficient method for the separation of various charged and neutral analytes. For analytes having limited solubility in water, the CE mode of separation has been micellar electrokinetic capillary chromatography (MECC). However, another approach is the direct addition of an organic solvent to a non-MECC CE separation system. Walbroehl and Jorgenson and also Balchunas and Sepaniak have reported on the use of organics in CE but the focus of their work was using MECC to separate small organic compounds. This work examines the use of aqueous-methanolic buffers in non-MECC CE separations of estrogens and rodenticides.


Subject(s)
Electrophoresis/methods , Estrogens/isolation & purification , Rodenticides/isolation & purification , Buffers , Methanol , Water
3.
Biochim Biophys Acta ; 954(3): 235-43, 1988 Jun 13.
Article in English | MEDLINE | ID: mdl-3370215

ABSTRACT

The kinetics of tubulin assembly were examined in the absence and presence of dimethyl sulfoxide at 37 degrees C. Inclusion of 1.4 M (10%) dimethyl sulfoxide lowered the critical protein concentration about 8-10-fold, from 9.4 microM in the absence of the organic solvent to 1.1 microM in its presence. This decrease was due solely to an effect on k-, the off rate constant. The on rate constant k+, was essentially unaffected. Another effect of dimethyl sulfoxide was in the nucleation process. The pseudo-first-order rate constant of elongation, kapp (k+[m]), was greatly increased by inclusion of dimethyl sulfoxide. This was due to an increase in the microtubule number concentration, [m]. The microtubules formed in the presence of dimethyl sulfoxide were much shorter than those formed in its absence, accounting for the higher number concentration. The nucleation number, n, was calculated by plots of ln kapp vs. ln c0 or ln t10% vs. ln c0, and the value appeared to be about 4 to 5, although some variability was found. It was shown that a plot of kapp vs. c0 to determine n, is not appropriate because of the inability to distinguish between linear and curved plots in the range of tubulin concentration used in assembly studies.


Subject(s)
Dimethyl Sulfoxide/pharmacology , Microtubules , Tubulin/metabolism , Animals , Brain , Cattle , In Vitro Techniques , Kinetics , Protein Binding , Solvents , Thermodynamics
4.
Biochem Biophys Res Commun ; 153(1): 328-33, 1988 May 31.
Article in English | MEDLINE | ID: mdl-2837207

ABSTRACT

A cDNA coding for 378 amino acids from the C-terminus of the human liver bifunctional enzyme, Fructose-6-phosphate,2-kinase:Fructose-2,6-bisphosphatase was isolated, sequenced, and expressed in E. coli K38. The expressed protein, identified by specific immunoassay, showed Fru 2,6-bisphosphatase activity but no Fru 6-P,2-kinase activity, demonstrating directly that the Fru 2,6-bisphosphatase activity resides in the C-terminal region. The Km for Fru 2,6-P2 was 4.3 microM. Fru 6-P was a noncompetitive inhibitor (Ki = 2.9 microM), and formed a phosphorylated intermediate when incubated with Fru 2,6[2-32P]P2. The subunit Mr of the enzyme was 36,600, and the active enzyme showed Mr = 37,000 by gel filtration.


Subject(s)
Cloning, Molecular , DNA/analysis , Gene Expression Regulation , Liver/enzymology , Phosphoric Monoester Hydrolases/genetics , Base Sequence , Escherichia coli/enzymology , Escherichia coli/genetics , Macromolecular Substances , Molecular Sequence Data , Molecular Weight , Phosphofructokinase-2
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