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At least 19 recordsLinked to original sources
PubMed1977

Influence of trichloroacetic acid-phosphotungstic acid on the thin layer chromatographic mobility of gangliosides.

Trichloroacetic acid (TCA)-phosphotungstic acid (PTA) precipitation has been used as a faster procedure than dialysis for the isolation of gangliosides, but the TCA-PTA treatment causes striking abnormalities in the thin layer chromatographic mobilities of the gangliosides. However, a normal chromatographic pattern can be restored by treating the precipitated gangliosides with the tetrasodium salt of ethylenediamine tetraacetic acid followed by dialysis. Hence, TCA-PTA treatment does not appear to cause artifacts or hydrolysis of the gangliosides.

Brain Chemistry↗
PubMed1995

Precipitation of Hevea brasiliensis latex proteins with trichloroacetic acid and phosphotungstic acid in preparation for the Lowry protein assay.

Many proteins derived from the latex of Hevea brasiliensis that remain soluble in trichloroacetic acid (TCA) can be precipitated by phosphotungstic acid (PTA). A combination of 5% TCA and 0.2% PTA precipitates a wide range of proteins effectively even when they are present in low concentrations (below 1 microgram ml-1). In addition to its protein purification function, acid precipitation also increases the sensitivity of the subsequent protein assay by allowing the test sample to be concentrated. Another advantage of protein precipitation by TCA and PTA is that very small amounts of protein (of the order of 10 micrograms) can be repeatably recovered without the use of precipitate-bulking agents such as sodium deoxycholate. This general procedure of protein purification and concentration is simple and rapid, but the use of PTA may not be fully compatible with the Bradford protein assay. A modified Lowry microassay is described which enables about 3 micrograms ml-1 to be quantitated at the photometric absorbance of 0.05. When used in conjunction with protein concentration by precipitating with TCA/PTA, approximately 0.4 microgram ml-1 protein present in 6 ml of solution can be assayed.

Chemical Precipitation↗
PubMed1979

Re-examination of effect of paracetamol on serum uric acid measured by phosphotungstic acid reduction.

The drug paracetamol (N-acetyl-p-aminophenol; acetaminophen) caused a spurious increase in serum uric acid measured by phosphotungstic acid reduction methods. However, the increase was less than 0.12 mmol/1 at plasma levels of paracetamol found in overdosage (40 mg/100 ml) and was small at therapeutic concentrations (less than 4 mg/100 ml). It is concluded that few patients with joint pain who have taken paracetamol paracetamol as an analgesic will have clinically misleading values for serum uric acid.

Acetaminophen↗
PubMed1989

A postembedding staining method of intensifying alcian blue reactions of acidic glycoconjugates with phosphotungstic acid in electron microscopy.

For the effective visualization of acidic glycoconjugates in electron microscopy, a post-embedding staining method has been devised for intensifying their alcian blue (AB) reactions by means of phosphotungstic acid (PTA). Tissue samples were prepared by glutaraldehyde-paraformaldehyde fixation of pieces of the trachea, aorta, and colon from adult rats. LR-White resin-embedded ultrathin sections were stained first with AB (pH = 1.0 or 2.5) and then reacted for PTA. In the tissues examined, the AB reaction of acidic glycoconjugates involved was effectively intensified by subsequent PTA staining in nearly all of the ultrastructures known to contain such carbohydrates. The majority of these ultrastructures failed to show any pronounced densities, if stained singly with PTA under the identical staining conditions. In all the ultrastructures, a series of selective methods such as active methylation and digestion with testicular hyaluronidase or neuraminidase have substantiated the selectivity of the PTA intensified AB reactions for acidic glycoconjugates involved. The present PTA intensified AB method resulted virtually in no contaminations of the backgrounds and can be regarded as a reliable and useful technique for the effective visualization of both intra- and extracellular acidic glycoconjugates in electron microscopy.

Alcian Blue↗
PubMed1979

Cytochemical analysis at the fine-structural level of trypanosomatids stained with phosphotungstic acid.

The ethanolic phosphotungstic acid (PTA) technic was used to detect, at the fine-structural level, basic proteins in various developmental stages of pathogenic Trypanosoma cruzi, and nonpathogenic Herpetomonas samuelpessoai, Leptomonas samueli, and Crithidia deanei, trypanosomatids. Reactions were observed in the nucleus of all stages. In the kinetoplast of epimastigote and promastigote forms reactions were noted mainly at the periphery. In trypomastigotes and choanomastigotes forms, however, an intense reacion was observed thorughout the kinetoplast. Reactions were present in cytoplasmic vesicles related to protein storage in T. cruzi and in membrane-bounded peroxisome-like organelles of H. samuelpessoai, L. samueli and C. deanei. The network of filaments which forms the paraxial rod did not react. In the flagellum, reaction was noted only at the peripheral doublet microtubules. PTA reacts also with structures related to the junction between the flagellar and cell body membranes.

Animals↗
PubMed1981

[Colorimetric determination of plasma vitamin C: comparison between 2,4-dinitrophenylhydrazine and phosphotungstic acid methods (author's transl)].

The evaluation of a recently published colorimetric method for plasma ascorbic acid determination, using phosphotungstic acid (PTA), was performed by comparison with the largely employed 2,4-dinitrophenylhydrazine (DNPH) procedure. The method has been evaluated according to International Federation of Clinical Chemistry (I.F.C.C.) recommendations. In particular, calibration procedures have been performed and precision, accuracy, linearity, specificity and sensitivity have been studied in biological samples. Linear regression analysis indicates that the two methods do not correlate completely. The PTA method shows a better recovery. The PTA method shares with the DNPH procedure a poor precision at low concentrations of vitamin C in plasma such as to make results less reliable at the clinically significative levels.

Ascorbic Acid↗
PubMed1976

Demonstration of mast cell granules by the cetylpyridinium chloride-acid dye (CPC-AD) and cetylpyridinium chloride-phosphotungstic acid (CPC-PTA) methods.

Cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CETAB) are bound to polyanionic substances by ionic bonds between the positively charged nitrogen of the quaternary salts and the negative groups of polyanions. The mast cell granules and some other structures treated with CPC or CETAB react selectively with acid dyes and fluorochromes. In ultrathin sections treated with CPC, phosphotungstic acid (PTA) greatly enhances the electron density of the granules of mast cells. The possible mechanism of acid dye and PTA binding by CPC or CETAB treated tissues is discussed.

Animals↗
PubMed2005

Ab initio and microcalorimetric investigations of alkene adsorption on phosphotungstic acid.

The adsorption of ethene, propene, 1-butene, trans-2-butene, and isobutene on phosphotungstic acid has been characterized by density functional theory (DFT) calculations and microcalorimetric experiments. The DFT-calculated chemisorption energies to form the corresponding alkoxides for ethene, propene, 1-butene, trans-2-butene, and isobutene were -86.8, -90.3, -102.6, -79.9, and -91.4 kJ mol(-1), respectively (for their most-favorable binding modes). The relative chemisorption energies to form the alkoxides are dictated by the strength of interaction of the acidic proton with the carbon atom of the double bond that becomes protonated. The activation barrier for chemisorption was greatest for alkenes with primary (1 degrees) carbenium-like transition states followed by secondary (2 degrees) and tertiary (3 degrees) transition states. The adsorption enthalpy established from microcalorimetric experiments with propene and isobutene was approximately -100 kJ mol(-1), which is close to the DFT-calculated values. Chemisorption of ethene on phosphotungstic acid during microcalorimetric experiments was minimal, presumably because of the large activation barrier associated with a 1 degrees carbenium-like transition state. The results from this study are compared with those in the literature for the adsorption of alkenes on zeolites, which have a similar adsorption mechanism. Our results suggest that alkene adsorption is stronger on phosphotungstic acid than on zeolites, as supported by the more exothermic chemisorption energies. Additionally, activation barriers for alkene adsorption are lower over phosphotungstic acid than over zeolites.

Journal Article↗