Phosphotungstic Acid

The insulin receptor (IR) is a four-chain, transmembrane dimer held together by disulfide bonds. To gain information about the molecular envelope and the organization of its domains, single-molecule images of the IR ectodomain and its complexes with three Fabs have been analyzed by electron microscopy. The data indicate that the IR ectodomain resembles a U-shaped prism of approximate dimensions 90

The differential association of the lipoproteins with risk of coronary artery disease necessitates quantification of the ... Northwest Lipid Research Clinic, Harborview Medical Center, Seattle, WA 98104; and the Department of Medicine, University of Washington, Seattle, ...

A homogeneous HDL-c assay (HDL-H), which uses polyethylene glycol-modified enzymes and sulfated alpha-cyclodextrin, was assessed for precision, accuracy, and cholesterol and triglyceride interference. In addition, its analytical performance was compared with that of a phosphotungstic acid (PTA)/MgCl2 precipitation method (HDL-P). Within-run CVs were < or = 1.87%; total CVs were < or = 3.08%. Accuracy was evaluated in fresh normotriglyceridemic sera using the Designated Comparison Method (HDL-H = 1.037 Designated Comparison Method + 4 mg/L; n = 63) and in moderately hypertriglyceridemic sera by using the Reference Method (HDL-H = 1.068 Reference Method - 17 mg/L; n = 41). Mean biases were 4.5% and 2.2%, respectively. In hypertriglyceridemic sera (n = 85), HDL-H concentrations were increasingly positively biased with increasing triglyceride concentrations. The method comparison between HDL-H and HDL-P yielded the following equation: HDL-H = 1.037 HDL-P + 15 mg/L; n = 478. We con...

Cubic cage compounds composed of Co-CN-Ru linkages have been prepared which illustrate the following features: (i) new motifs for alkali metal ion complexation (i.e., cationic receptors for cations), (ii) a new family of triaza-metalloligands, and (iii) a double box-like cage. The cages are synthesized by the condensation of [CpCo(CN)3] and [Cp*Ru(NCMe)3]+ (cyclopentadienyl, Cp; pentamethylcyclopentadienyl, Cp*) the presence of Cs+. The species {Cs subset {[CpCo(CN)3]4[Cp*Ru]4}+ and {Cs subset {[CpCo(CN)3]4[Cp*Ru]3[Cp*Rh]}2+ illustrate the box-completion reaction Cs subset Co4Ru3 + M (M = Cp*Rh2+, Cp*Ru+). With the naked ion precursors [Na(NCMe)6]+ and [Fe(NCMe)6]2+, the box-completion reactions afforded {Na{Cs subset [CpCo(CN)3]4[Cp*Ru]3]}2}+ and {Fe{Cs subset [CpCo(CN)3]4[Cp*Ru]3]}2}2+. These cages provide the first examples, to our knowledge, of the double-box motif.

ABSTRACT We compared six methods for isolating high-density lipoproteins from normal and lipemic serum. Cholesterol was determined by two different enzymic methods. The values for high-density lipoprotein cholesterol obtained with two (centrifugation-speed) modifications of the heparin/Mn2+ method and with the phosphotungstate/Mg2+, the dextran sulfate/Mg2+, and the polyethylene glycol methods were compared with those obtained by ultracentrifugation. One cholesterol method, in which each determination was blank-corrected, was not interfered with by the various precipitation reagents. The other, in which there was no blank correction, was considerably interfered with by Mn2+ and dextran sulfate. Neither method was interfered with by phosphotungstate/Mg2+ or by polyethylene glycol. Use of ethylenediaminetetraacetate in either cholesterol reagent was unhelpful (or deleterious). After correction for all interferences caused by the precipitation reagents and EDTA, values obtained for high-density lipoprotein cholesterol agreed well with those by ultracentrifugation (corrected for apo B-containing lipoproteins in the d>1.063 kg/L fraction). Rocket immunoelectrophoresis showed no significant co-precipitation of high-density lipoproteins in any method. Various methods for complete removal of apo B-containing lipoproteins from lipemic serum appeared to vary widely in efficiency, but the optimized phosphotungstate method and the polyethylene glycol method appeared best. With them, only sera with triglyceride concentrations of 7.6 and 18.5 mmol/L or greater, respectively, could not be fractionated successfully. However, after ultrafiltration, accurate values were also obtained with the other methods. We conclude that the phosphotungstate method and the polyethylene glycol method are the best methods for HDL-cholesterol analysis when enzymic cholesterol analysis is used.

Cubic cage compounds composed of Co-CN-Ru linkages have been prepared which illustrate the following features: (i) new motifs for alkali metal ion complexation (i.e., cationic receptors for cations), (ii) a new family of triaza-metalloligands, and (iii) a double box-like cage. The cages are synthesized by the condensation of [CpCo(CN)3] and [Cp*Ru(NCMe)3]+ (cyclopentadienyl, Cp; pentamethylcyclopentadienyl, Cp*) the presence of Cs+. The species {Cs subset {[CpCo(CN)3]4[Cp*Ru]4}+ and {Cs subset {[CpCo(CN)3]4[Cp*Ru]3[Cp*Rh]}2+ illustrate the box-completion reaction Cs subset Co4Ru3 + M (M = Cp*Rh2+, Cp*Ru+). With the naked ion precursors [Na(NCMe)6]+ and [Fe(NCMe)6]2+, the box-completion reactions afforded {Na{Cs subset [CpCo(CN)3]4[Cp*Ru]3]}2}+ and {Fe{Cs subset [CpCo(CN)3]4[Cp*Ru]3]}2}2+. These cages provide the first examples, to our knowledge, of the double-box motif.

Prions are composed solely of an alternatively folded isoform of the prion protein (PrP), designated PrPSc. The polyoxometalate phosphotungstic acid has been used to separate PrPSc from its precursor PrPC by selective precipitation; notably, native PrPSc has not been solubilized by using nondenaturing detergents. Because of the similarities between PrPSc and lipoproteins with respect to hydrophobicity and formation of phosphotungstic acid complexes, we asked whether these molecules are bound to each other in blood. Here we report that prions from the brains of patients with sporadic Creutzfeldt-Jakob disease (CJD) bind to very low-density (VLDL) and low-density (LDL) lipoproteins but not to high-density lipoproteins (HDL) or other plasma components, as demonstrated both by affinity assay and electron microscopy. Immunoassays demonstrated that apolipoprotein B (apoB), which is the major protein component of VLDL and LDL, bound PrPSc through a highly cooperative process. Approximately 50% of the PrPSc bound to LDL particles was released after exposure to 4 M guanidine hydrochloride at 80°C for 20 min. The apparent binding constants of native human (Hu) PrPSc or denatured recombinant HuPrP(90-231) for apoB and LDL ranged from 28 to 212 pM. Whether detection of PrPSc in VLDL and LDL particles can be adapted into an antemortem diagnostic test for prions in the blood of humans, livestock, and free-ranging cervids remains to be determined. prion protein | apolipoprotein B | blood | Creutzfeldt-Jakob disease <HR ALIGN=LEFT WIDTH=50% NOSHADE SIZE=1>

The ultrastructural cytochemical study of the neck region of human spermatids and spermatozoa revealed that, besides the centrioles, the basal plate, the lateral cupshaped junction body and the annulus material showed affinity for both ethylene diamine tetra-acetic acid (EDTA) stain (a preferential staining method for ribonucleoproteins) and ethanolic phosphotungstic acid (PTA) stain (for cellular localisation of basic proteins). The capitulum and the surface of the striated columns were also stained with ethanolic PTA. The chromatoid body and annulate lamellae-which were frequently encountered in the neck region--stained with both EDTA and ethanolic PTA techniques. This suggests a possible participation of the chromatoid body and annulate lamellae in the formation of the neck region structures.

The phosphotungstate anion (PTA) is widely used to facilitate the precipitation of disease-causing prion protein (PrP(Sc)) from infected tissue for applications in structural studies and diagnostic approaches. However, the mechanism of this precipitation is not understood. In order to elucidate the nature of the PTA interaction with PrP(Sc) under physiological conditions, solutions of PTA were characterized by NMR spectroscopy at varying pH. At neutral pH, the parent [PW12O40](3-) ion decomposes to give a lacunary [PW11O39](7-) (PW11) complex and a single orthotungstate anion [WO4](2-) (WO4). To measure the efficacy of each component of PTA, increasing concentrations of PW11, WO4, and mixtures thereof were used to precipitate PrP(Sc) from brain homogenates of scrapie prion-infected mice. The amount of PrP(Sc) isolated, quantified by ELISA and immunoblotting, revealed that both PW11 and WO4 contribute to PrP(Sc) precipitation. Incubation with sarkosyl, PTA, or individual components o...

Actinomyces israelii is the most common cause of human actinomycosis, a chronic granulomatous infection. Periapical actinomycosis involving A. israelii has been identified as an important cause of failure of conventional endodontic treatment. Structures on the bacterial cell surface have been implicated in the pathogenicity of Actinomyces. In this study the ultrastructure of A. israelii was investigated by electron microscopy. Negatively stained preparations revealed the presence of hairlike fimbriae protruding through a thick surface coat on some species, whilst thin sectioning disclosed a Gram-positive cell wall surrounded by a fuzzy outer coat. These structures may be important for the pathogenicity of A. israelii.