Showing papers on "Phosphotungstic acid published in 1976"

Mercaptans by catalytic cleavage of organic sulfides

Abstract: A method is provided for preparing mercaptans by catalytic cleavage of organic sulfides with hydrogen sulfide in the presence of a supported phosphotungstic acid catalyst. The process is particularly advantageous with n-alkyl sulfide feedstock and being highly selective for producing n-alkyl mercaptan product. In one embodiment the presence of carbon disulfide in the reaction mixture increases the conversion at low temperature as compared to the process without the presence of carbon disulfide.

Split chromatographic spot produced by supposedly single gangliosides treated with trichloroacetic acid-phosphotungstic acid reagent.

Abstract: GANGLIOSIDES are currently separated from water soluble, non lipid contaminants by methods that include dialysis after Folch’s partition (FOLCH et a[., 1957). passage through Sephadex G-25 in organic solvents (WELLS & DITTMFR. 1963; ARCF et al.. 1966). paper chromatography or electrophoresis in borate buffer (KAUFMAN et al., 1966) and trichloroacetic acid-phosphotungstic acid (TCA-PTA) precipitation (DE VRIFS & BARONDES. 1971; MACCIONI et al., 1974; PATT & GRIMES. 1974; MFSTRALLET et a/., 1974; DUNN, 1974). Because of its simplicity the last method is being used with increasing frequency for metabolic studies. For this reason we deem of interest to call attention to chromatographic changes that occur to some gangliosides after TCA-PTA treatment. We became aware of these changes while attempting to account for an unexpected chromatographic component which appeared when the TCA-PTA method was used as a substitute for a previously used method in the study of the enzymatic synthesis of G, (MFSTRALLFT et al.. 1974).

Cytochemical studies on RNP complexes produced by puff 2-48BC in Drosophila hydei: uranyl acetate and phosphotungstic acid staining

Abstract: Differential staining of the core and RNP particles of RNP complexes in puff 2--48 BC in salivary gland chromosomes of Drosophila hydei was achieved with aqueous uranyl acetate (UA) at low pH, with UA in acetone, with phosphotungstic acid (PTA) in organic solvents, and with aqueous PTA at pH 5 And 6. A comparison of the results of UA and PTA staining under various conditions indicate that the proteins in the core region and in the RNP particles connected to it differ with respect to their amino-acid composition (arginine and lysine residues).--The staining mechanism of PTA and UA is discussed.

Phosphotungstic acid-chromic acid: a selective stain for algal plasma membranes1,2

Abstract: SUMMARY A phosphotungstic acid-chromic acid mixture selectively stains the plasma membrane of whole cells of selected members of the Chlorophyceae, Charophyceae, Euglenophyceae, Xanthophyceae, Bacillariophyceae, Chrysophyceae, and Rhodophyceae, and the plasma membrane in cell-free fractions of Mougeotia (Chlorophyceae). The procedure is not effective on the plasma membrane of the cyanophycean Scytonema or the cyanophycean endosymbiont of Glaucocystis. Staining of the cell walls of Chlamydomonas, Bangia, and Scytonema and the pellicle and sliding junction of Euglena and Astasia suggest that PTA-CrO3 reactivity may be associated with glycoproteins in the cell walls and plasma membranes.

Preparation of carbonyl sulfide and production of methyl mercaptan therefrom

Abstract: Methyl mercaptan is prepared by hydrogenating carbonyl sulfide in the presence of a sulfactive catalyst The carbonyl sulfide is prepared by reacting carbon dioxide and carbon disulfide in the presence of a supported phosphotungstic acid catalyst

Electron microscopy of interphase chromosomes in situ; binding of permanganate to chicken erythrocytes.

Abstract: From quantitative electron-microscope observations on the binding of permanganate to regions of erythrocytes and reticulocytes of known chemical composition, it is concluded that KMnO4, like phosphotungstic acid (PTA), binds preferentially to sites on proteins. Compared with PTA, KMnO4 binding exhibits less anomalous behaviour. The data support the hypothesis previously put forward that the 2 regions, or phases, in condensed chromatin differ in both molecular composition and concentration. The increase in binding to protein which occurs during nuclear haemolysis is interpreted in terms of protein-protein interaction in the chromatin of the intact cell.

An alcohol-soluble Schiff's reagent: a histochemical application of the complex between Schiff's reagent and phosphotungstic acid.

Abstract: A schedule for staining partially hydrated PAS-positive structures using non-aqueous solutions has been devised. Tissues are dewaxed, taken down to 70% alcohol, oxidised for 10 min in a 1% w/v alcoholic solution of periodic acid, treated with an alcoholic solution of phosphotungstic acid-Schiff reagent complex (PTA-Schiff reagent) for 25 min, washed in alcohol, cleared in xylene and mounted in a synthetic medium. The PTA-Schiff reagent complex prepared from de Tomasi Schiff reagent by precipitation with PTA may be stored in the deep freeze for many months and dissolved freshly in alcohol for use. The PTA-Schiff reagent sued as above allows staining of highly water soluble materials such as dextran. From blocking and digestion studies the mode of action seems similar to de Tomasi Schiff reagent. The partial hydration of the tissues prior to reaction was found to be essential for effective staining.

[Acid mucopolysaccharide detection on ultra-thin sections by alcian blue in dental tissues embedded in Epon].

Abstract: Ultra-thin sections of dental tissues, fixed in glutaraldehyde and osmium tetroxide, embedded without previous demineralization in Epon, were contrasted the grids with an alcian blue solution after previous oxidation periodic acid or hydrogen peroxide. Correlations with histochemical results obtained with the optical microscope, other results obtained with ruthenium red and phosphotungstic acid and controls made after enzymatic digestion with chondroitinase AC suggest that this technique is specific for the detection of acid mucopolysaccharides in those calcified tissues studied.

C onditions for Negative Staining of Influenza Virus on Carbon Coated Microgrids

Abstract: The negative staining for the electronmicroscopic preparation of virus particles was made by adjusting the surface tension of carbon-coated grids with potasium hydroxide. The fine structure with good contrast appeared in the smooth background of the film, when the specimen was stained with the 2% phosphotungstic acid solution containing 1/30 N potasium hydroxide.