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Results for “PERCHLORIC ACID”

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At least 577 records · Page 32Linked to original sources

PubMed1987

Acid-stable protease inhibiting polypeptides formed from denatured horse plasma by proteolysis.

1. Trypsin digestion of perchloric acid precipitated horse plasma yielded polypeptides with inhibitory properties for trypsin, chymotrypsin and, to a small extent, kallikrein. 2. The Mr of the inhibitory polypeptides were 73,000 and 24,000. 3. The number, enzyme specificity and Mr of the inhibitory polypeptides differed from the values known for the human being. 4. The inhibitory polypeptides were purified by affinity chromatography on Sepharose-trypsin and by gel filtration through Sephadex G-75. 5. Protease inhibitory polypeptides were generated in the same manner by chymotrypsin, elastase, proteinase K, pronase, collagenase, papain and subtilisin. 6. The number and electrophoretic migration of the inhibitory polypeptides obtained with the different enzymes were variable. 7. The enzyme specificity was constant since all polypeptides inhibited only trypsin, chymotrypsin and kallikrein to a small extent. 8. None of the inhibitory polypeptides were immunologically related to native plasma proteins or plasma protease inhibitors.

Animals↗

PubMed1996

Determination of amino acids in human serum by capillary gas chromatography.

A simple and rapid method for the determination of serum amino acids by gas chromatography (GC) has been developed. Following deproteinization of serum with perchloric acid, free amino acids in the supernatant were converted into their N(O,S)-isobutoxycarbonyl methyl ester derivatives and measured by GC with flame ionization detection using a DB-17 capillary column. All the derivatives of the 22 protein amino acids were completely resolved as single peaks within 9 min by GC. The calibration curves were linear in the range 0.2-50 micrograms of each amino acid, and the correlation coefficients were above 0.998. By using this method, serum amino acids could be directly analysed without prior clean-up procedure such as ion-exchange column chromatography except for deproteinization of the samples, and without any interference from coexisting substances. Overall recoveries of amino acids added to serum samples were 88-108%. Analytical results for serum amino acids from normal subjects are presented.

Amino Acids↗

PubMed1975

Synthesis of soluble protein in oocytes of Xenopus laevis.

Oocytes of five stages of development were isolated from ovaries of Xenopus laevis and allowed to take up radioactive amino acids. After six hours of labeling the amount of label incorporated into perchloric acid precipitable material from the soluble oocyte fraction and the specific activity of the label free pool was determined. From these figures an estimate of the rate of protein synthesis was calculated. Labeled soluble protein from each oocyte stage was analyzed by electrophoresis on SDS polyacrylamide gels. The gel was dried and autoradiographed to determine the qualitative pattern of soluble protein synthesis during various stages of oogenesis. Our results indicate that no significant differences exist in the rate of protein synthesis among any of the stages of oogenesis investigated. The qualitative pattern of soluble protein synthesized during the labeling period is similar among the oocyte stages. Moreover, this qualitative pattern of soluble protein synthesis is the same as the pattern of soluble protein accumulated up to that time during oogenesis. These results suggest a stable synthesis and accumulation of maternal protein products during Xenopus oogenesis, in marked contrast to the results that have been reported for RNA synthesis during oogenesis in Xenopus. Our results are discussed in terms of the present understanding of the process of maternal information accumulation.

Animals↗

PubMed2006

Liquid chromatography/tandem mass spectrometry assay for the quantification of troxerutin in human plasma.

A simple, rapid, sensitive and specific liquid chromatography/tandem mass spectrometry method was developed and validated to quantify troxerutin in human plasma. The analyte and rutin, used as the internal standard, were analyzed on a Phenomenex Synergi Fusion RP column interfaced with a triple-quadrupole tandem mass spectrometer using positive electrospray ionization. Acetonitrile/water (20:80 v/v) was used as the isocratic mobile phase, with 0.1% formic acid in water. A simple sample preparation method of protein precipitation with perchloric acid was employed. The assay was linear over the concentration range 31.25-4000 pg/mL. Correlation coefficients generated by linear regression with a 1/x(2) weighting factor ranged from 0.9991 to 0.9996. The intra- and inter-day precision over the entire concentration range were less than 12.28%. The method was successfully applied to a pharmacokinetic study after oral administration of a 300 mg troxerutin drop pill to 18 healthy volunteers.

Adult↗

PubMed1990

In vitro 31P-NMR spectroscopic studies of rat liver subjected to chronic ethanol administration.

31P-NMR spectroscopy of rat liver perchloric acid extracts was utilized to assess hepatic levels of major phosphorylated metabolites with and without ethanol administration from 0 to 51 days. The results are: (1) 3-phosphoglycerate was largely decreased starting from the first day of ethanol ingestion, (2) in ethanol-treated rats, phosphoethanolamine exhibited a significant decrease relative to the control rats until around day 30, (3) glycerophosphocholine and glycerophosphoethanolamine decreased over the entire period of ethanol ingestion, (4) ATP, AMP, Pi and energy charge showed significant changes due to ethanol effects when a 40-50 s exposure to CO2 was used prior to freeze-clamping, but ADP did not change, and (5) the other observable metabolites did not show statistically significant change. Some time-dependent changes in metabolite concentration, although not dramatic, were observed from day 1 to day 51 of ethanol administration. Our results indicate that chronic ethanol ingestion results in an inhibition of glycolysis and gluconeogenesis, a decrease in phospholipid breakdown and a lowering of hepatic energy charge.

Adenosine Diphosphate↗

PubMed2000

Determination of 18alpha-glycyrrhizin and 18beta-glycyrrhizin in dog plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic method has been developed for the separation and determination of 18alpha-glycyrrhizin (alpha-GZ) and 18beta-glycyrrhizin (beta-GZ) in dog plasma. The two compounds were separated on a reversed-phase column and detected by UV absorption at 254 nm. The mobile phase was a mixture of water-methanol-60% perchloric acid (45:55:0.5, v/v) and was adjusted to pH 8.0 with 25% ammonia solution. Indomethacin was added to the plasma as an internal standard. Methanol was selected for the extraction of both the compounds and internal standard. Alpha-GZ and beta-GZ could be precisely determined in concentration of 1 mg/ml in a 0.1 ml sample.

Ammonia↗

PubMed2005

Guanidinium-based ionic liquids.

Cyclic (subset=N+<, subset = imidazolidine 3 and 4, hexahydro-pyrimidine 7 and 8, tetrahydro-1,3,5-oxadiazine 12, and triazoline 15 and 16) and acyclic [(R2N)2C=N+<, 19] guanidinium-based salts were synthesized via the quaternization of guanidine derivatives with nitric or perchloric acid or with iodomethane followed by metathesis reaction with silver nitrate, silver perchlorate, or ammonium dinitroamide. The structure of 15d was confirmed by single-crystal X-ray analysis. Most of the salts exhibited low melting points and good thermal stabilities. Their densities range between 1.2 and 1.5 g/cm3. Standard molar enthalpies of formation were calculated from experimentally determined constant-volume combustion energies obtained using an oxygen bomb calorimeter.

Journal Article↗

PubMed1990

Digestion method for the determination of mercury in vegetable matrices by cold vapour atomic absorption spectrometry.

A simple and rapid wet-digestion procedure is described for the determination of total mercury in botanical samples by cold vapour atomic absorption spectrometry. The method is based on the oxidising properties of potassium dichromate in dilute sulphuric acid and was tested on two National Institute of Standards and Technology Standard Reference Materials. The mass of the samples taken for analysis was about 0.5 g in all instances, corresponding to an amount of mercury of the order of 0.075-0.040 micrograms depending on the material. The results were compared with those obtained using the Association of Official Analytical Chemists official digestion technique, which involves the use of nitric and sulphuric acids, and a second technique based on the action of nitric and perchloric acids. The proposed method provided better accuracy and showed good precision. Its ability to achieve the decomposition of two organomercurials for full mercury recovery was verified.

Mercury↗

PubMed1967

A spectrophotometric method for the direct determination of cysteine in the presence of other naturally occurring amino acids.

1. An acid ninhydrin reagent was found to react specifically in forming a pink product (E(max.) 560mmu) with cysteine. 2. The method was highly sensitive for the determination of cysteine (in 28.0x10(3)). Homocysteine, glutathione, proline, ornithine and other naturally occurring amino acids tested did not give a similar reaction. 3. The reaction product was stable for at least 3-4hr. at room temperature and the extinction was proportional to the concentration in the range 0.05-0.5mumole of cysteine. 4. The acid ninhydrin reagent also gave yellow products (E(max.) 370-404mmu) with tryptophan, 5-hydroxytryptophan, 5-hydroxytryptamine and indol-3-ylacetic acid. 5. The method was applied for the determination of cysteine in perchloric acid extracts of rat brain, liver and blood.

Amino Acids↗

PubMed1979

Ribonucleoprotein staining of centrioles and kinetochores in newt lung cell spindles.

The distribution of ribonucleoprotein (RNP) within the mitotic spindle of newt lung epithelial cells was studied with the high voltage electron microscope (HVEM) using Bernhard's uranyl-EDTA-lead staining of thick sections in conjunction with the ribonuclease digestion of fixed cells. The results indicate that aside from ribosomes, the major RNP-containing components of the spindle are the kinetochores and centrioles, both of which stain electron-opaque after EDTA treatment. In both cases, the electron-opaque material associated with these microtubule organizing centers (MTOC's) can be removed by RNAse digestion and cold perchloric acid (PCA) extraction under conditions which leave the spindle microtubules (Mts) centrioles, and kinetochores intact. The staining reaction is not abolished by cold PCA extraction alone or by substituting other positively charged proteins (i.e., cytochrome c or lysozyme) for RNAse. The RNP component of the kinetochore is closely associated with the bases of the kinetochore microtubules. The RNP component of the centriole can be seen to surround the microtubules of the triplet blades. No evidence was found to indicate the presence of RNP in the pericentriolar material. The possible function of both kinetochore and centriolar RNP is discussed.

Animals↗

PubMed1985

Simultaneous determination of homovanillic acid, 3,4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid in brain tissue, using a double-column procedure.

A double-column procedure for simultaneous determination of homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) in brain tissue was described. These compounds extracted with perchloric acid were adsorbed on Sephadex G-10 in the column. HVA and DOPAC were desorbed from Sephadex G-10 with 0.01 N HCl and then retained on QAE-Sephadex A-25 (acetate form) placed beneath the Sephadex G-10 column. HVA and DOPAC were eluted with small volume of 0.2 mol/l NaCl. 5-HIAA remaining on the Sephadex G-10 was eluted with 0.05 mol/l phosphate buffer at pH 7.5. Each substance was determined fluorometrically. The recovery rates of HVA, DOPAC and 5-HIAA were more than 80, 80 and 85%, respectively. Effects of oxypertine on dopamine (DA) neurons in the rat brain were investigated using the method described here. Oxypertine caused marked increases in the levels of HVA and DOPAC in cortex and striatum of the rat brain, without any obvious change in the level of 5-HIAA after the intraperitoneal administration of 10 mg/kg oxypertine. These findings suggest that the favorable antipsychotic action of oxypertine may be due not only to a marked reduction in brain norepinephrine level, but to a blockade of DA receptors.

3,4-Dihydroxyphenylacetic Acid↗

PubMedDate not supplied

Colorimetric determination of total iodine in foods by iodide-catalyzed reduction of Ce+4.

An earlier acid digestion determination of iodine in foods was modified to provide an improved detection limit and to allow for the analysis of a greater variety and larger amounts of foods. The organic material in the sample was oxidized overnight by concentrated nitric acid, followed by digestion in a mixture of concentrated sulfuric and 70% perchloric acid. The iodine was determined by an automated colorimetric method based on the iodide-catalyzed reduction of Ce+4 by As+3. The method had an average relative standard deviation of 3.1% for the samples analyzed, and a detection limit of 0.1 ng/mL in the digested solution and 5 ng/g in a 2 g sample prior to digestion. The recovery of added iodine ranged from 90.3 to 101.3%, using external standards. Samples analyzed included NBS Standard Reference Material 1549, and composites of a variety of dairy products, meat, eggs and fish, cereals, and potatoes. The iodine detected in these samples ranged from 9 ng/g for the potato group to 3360 ng/g for the standard reference material.

Autoanalysis↗

PubMed1988

A spectrophotometric assay for the degradation of the siderophore deferrioxamine B.

A spectrophotometric assay using ferric perchlorate in a perchloric acid solution has been developed to monitor the degradation of the trihydroxamate siderophore deferrioxamine B to monohydroxamates. Using the ferric perchlorate solution and employing various concentrations of acetohydroxamic acid (as the model monohydroxamic acid) while maintaining a constant amount of deferrioxamine B resulted in the shifting of the absorption maximum from that of ferrioxamine B to longer wavelengths and toward that of a pure ferri-acetomonohydroxamic acid solution. A similar result was noted when a cell-free extract, from a bacterium capable of using deferrioxamine B as its sole carbon source, was given the siderophore in a phosphate buffer and aliquots of the enzyme-deferrioxamine B solution were removed for analysis. The assay may thus be used to monitor the formation of the monohydroxamic acid degradation products of the siderophore by the enzyme(s) in the cell-free extract.

Deferoxamine↗

PubMed1980

A critical evaluation of a serum sermucoid assay and its replacement by a serum alpha 1 acid glycoprotein assay.

The composition of serum seromucoid, the protein fraction of serum not precipitated by 0.6 M perchloric acid, has been shown to vary with the technique of preparation. Immunochemical examination revealed that 91.5% of the protein present in the seromucoid fraction of serum was alpha 1 acid glycoprotein, the remainder consisting of alpha 1 antitrypsin, alpha 1 antichymotrypsin, beta 2 glycoprotein, haemopexin, albumin, and pre-albumin. Serum alpha 1 acid glycoprotein concentration determined by radial immunodiffusion correlated well with serum seromucoid concentration although the former was usually 0.4 g/l lower. The determination of serum alpha 1 acid glycoprotein by an immunological method is more precise than the seromucoid method and is not subject to interference from other proteins.

Adolescent↗

PubMed1999

1H-NMR analysis of microbial-derived organic acids in primary root carious lesions and saliva.

In addition to lowered pH values, the molecular profile and concentrations of microbial-derived organic acids in carious dentin are important demineralization parameters involved in the induction, development and progression of dental caries. High-resolution proton ((1)H) NMR spectroscopy was employed to examine the organic acid status of primary root carious lesions. (1)H-NMR analysis of post-neutralized perchloric acid extracts of active carious lesions revealed that at an operating frequency of 600 MHz, the (1)H-NMR-detectable organic acid composition of carious dentin samples (mean molecular percentage content +/- standard error; the mean molecular percentage content is defined here as the mean of the concentration of each (1)H-NMR-visible organic acid/anion expressed as a percentage of total (1)H-NMR-detectable organic acid/anion level in each sample) was acetate 51 +/- 2%, formate 37 +/- 2%, lactate 5 +/- 1%, propionate 3 +/- 0.8%, pyruvate 2.4 +/- 0.3%, n-butyrate 1.2 +/- 0.2%; succinate 0.1 +/- 0.1%; iso-butyrate, n- and iso-valerate, and n- and iso-caproate (total) <0.2%. Further components detectable included alanine, glycine, choline, phosphorylcholine, trimethylamine oxide, methanol, glycolate and assorted saccharides. In view of their high dissociation constants (K(a)), our results demonstrate that formic and pyruvic acids (K(a) = 1.77 x 10(-4) and 3.20 x 10(-3) mol/dm(3), respectively) contribute substantially to the decreased pH values associated with active caries lesions (cf. lactate K(a) = 1.40 x 10(-4) mol/dm(3)), and hence the pathogenesis of primary root caries.

Aged↗

PubMed2006

Energetic bicyclic azolium salts.

Bicyclic azoles, 2-methyl-5-(imidazol-1-yl)-2H-tetrazole (1), 2-methyl-5-(1,2,4-triazol-1-yl)-2H-tetrazole (4), 1-methyl-5-(imidazol-1-yl)-1H-tetrazole (7), 1-methyl-5-(1,2,4-triazol-1-yl)-1H-tetrazole (10), 1-methyl-4-nitro-2-(imidazol-1-yl)-1H-imidazole (13), and 1-methyl-4-nitro-2-(1,2,4-triazol-1-yl)-1H-imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18-21, with densities ranging between 1.519-1.674 g cm-3, were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12 b and 21 b were confirmed by single-crystal X-ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from DeltaHdegreef=209.9 (21 a) to 412.3 (12 b) kJ mol-1 in which the experimental densities are >1.515 g cm-3.

Journal Article↗

PubMed1992

High-resolution 1H NMR spectroscopy studies of extracts of human cerebral neoplasms.

High-resolution 1H NMR spectroscopy has been used to measure the concentrations of metabolites (alanine, N-acetylaspartate, gamma-aminobutyric acid, glutamate, glutamine, aspartate, taurine, glycine, succinate, creatine, cholines, inositol, and glucose) in perchloric acid extracts of human epileptic cortex and brain tumors. All tissue was obtained by surgical biopsy, excised before thermal coagulation, and immediately frozen in liquid nitrogen. Lower levels of N-acetylaspartate and gamma-aminobutyric acid and a shift in the glutamate/glutamine ratio toward glutamine in the tumors reflect neuronal loss. Abnormal glucose metabolism (aerobic glycolysis) in the tumors gives decreased levels of succinate, glutamate, aspartate, glutamine, and creatine and generally increased concentrations of glycine and alanine. Differences in metabolite concentrations that may be of use in differential tumor diagnosis include lower creatine and inositol in meningiomas than in astrocytomas. Lower taurine differentiates benign from malignant astrocytomas. Malignant astrocytomas and metastatic tumors are more regionally heterogeneous than meningiomas or benign astrocytomas. Mannitol, administered perioperatively to all patients from whom tissue was obtained, was observed only in the spectra of extracts of tissue from tumors which enhanced on computerized tomographic imaging.

Adolescent↗

PubMed1994

A convenient access to beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl fluoride oligosaccharides and beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides by fluorolysis and fluorohydrolysis of chitosan.

beta-(1-->4)-Linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides, in the form of their alpha-glucopyranosyl fluorides at the reducing end, were obtained by fluorolysis of chitosan in anhydrous hydrogen fluoride at room temperature. The average dp depended on the reaction time and was conveniently monitored by 13C NMR spectroscopy, using the signal ratios for beta-(1-->4) bonded C-1 at approximately 98.5 ppm and the C-1 doublet for the terminal glycosyl fluoride moiety at approximately 104 ppm. Preparative fractionation of dp 2-11 glycosyl fluoride oligosaccharides, obtained after 18 h of fluorolysis, was achieved by gel-permeation chromatography on Bio-Gel P-4 with aqueous acetic acid-ammonium acetate as eluent. Hydrolysis of the anomeric fluoride, with either aqueous perchloric acid, or by a sequence involving formation of the C-2 N-trifluoroacetate and subsequent simultaneous hydrolysis of the glycosyl fluoride and the amide substituent with aqueous methanol, yielded the free beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides which were separated, for dp 2-11, by the same gel-exclusion technique. Both oligosaccharide series, either free or in the form of their alpha-glycopyranosyl fluorides, were fully characterized.

Carbohydrate Conformation↗