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PubMed1986

High-performance liquid chromatography of aldehydes and acids formed in monoamine oxidase-catalyzed reactions.

A rapid, sensitive, and specific method for the determination of monoamine oxidase (MAO) activities toward different substrates is described. The assay is based on high-performance liquid chromatographic (HPLC) separation and electrochemical detection of the aldehyde or acid products. The aldehyde metabolic intermediates were observed to be quite stable in 0.1 N perchloric acid containing antioxidant and EDTA, and therefore can be used to measure the MAO activity of washed mitochondrial membrane and partially purified or purified MAO. Incomplete conversion of aldehyde to acid was observed when the amine substrates were incubated with the crude enzyme preparations. These aldehydes can be converted to corresponding acids by addition of yeast aldehyde dehydrogenase and beta-NAD and the acid can also be measured by HPLC-electrochemical detection. A deuterium isotope effect in the oxidation of p-[alpha,alpha-2H2]tyramine and [alpha,alpha-2H2]serotonin has been demonstrated by this method.

Acids↗
PubMed1991

3-Methoxy-4-hydroxyphenylethyleneglycol concentrations in discrete hypothalamic nuclei reflect the activity of noradrenergic neurons.

An analytical technique is described which permits the quantitation of picogram concentrations of 3-methoxy-4-hydroxyphenylethylene-glycol (MHPG) in acid hydrolyzed extracts of microdissected regions of the rat brain, and this procedure is used to determine if alterations in the activity of noradrenergic neurons are reflected by changes in the concentrations of MHPG in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the rat hypothalamus. MHPG was not detected in non-hydrolyzed samples of either the PVN or SON, but following acid hydrolysis (heating of samples at 94 degrees C for 5 min in 0.16 M perchloric acid) MHPG was detected in both of these regions. These results indicate that MHPG exists primarily as a conjugate in the PVN and SON. Neurotoxin-induced lesions of the ventral noradrenergic bundle decreased norepinephrine (NE) and MHPG concentrations in the PVN and SON, demonstrating that tissue levels of MHPG in these brain regions are dependent upon the presence of noradrenergic neurons. Electrical stimulation of the locus coeruleus increased MHPG concentrations in the PVN, but not in the SON, whereas electrical stimulation of the medial forebrain bundle increased MHPG concentrations in both of these regions. The alpha 2-adrenergic receptor antagonist idazoxan increased, while the alpha 2-adrenergic receptor agonist clonidine decreased MHPG concentrations in both the PVN and SON, but neither idazoxan nor clonidine altered NE concentrations in these regions. Immobilization of rats in the supine position increased MHPG concentrations in the PVN and SON, and this was accompanied by a decrease in NE concentrations in the SON.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1988

Simple assay procedure for tyrosine hydroxylase activity by high-performance liquid chromatography employing coulometric detection with minimal sample preparation.

A simple assay procedure for tyrosine hydroxylase activity in crude tissue samples was devised that requires minimal sample preparation and use of high-performance liquid chromatography with coulometric electrochemical detection. After incubation of enzyme samples, such as human brain homogenates or rat pheochromocytoma PC12h cells, with L-tyrosine and a tetrahydropterin cofactor, in the presence or absence of p-bromobenzyloxyamine, an inhibitor of aromatic L-amino acid decarboxylase, the reaction was terminated by addition of an equal volume of 0.1 M perchloric acid. For quantitation of L-DOPA produced, the sample was centrifuged, filtered and directly applied to the chromatographic apparatus connected to a coulometric electrochemical detector. This method makes redundant a time-consuming step in the previous methods, purification and concentration of L-DOPA or dopamine using alumina. The reaction conditions for the assay of tyrosine hydroxylase activity in brain homogenates and PC12h cells were re-examined by this method. Both tyrosine hydroxylase samples required a naturally occurring cofactor, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin [(6R)BH4], catalase and NSD-1055 for the full activity, and tyrosine hydroxylase in human brain homogenates required Fe2+ ions for its full activity. (6R)BH4 proved to be a more effective cofactor than a synthetic cofactor, (6RS)-methyl-5,6,7,8-tetrahydropterin, which is commonly used for this assay.

Adrenal Gland Neoplasms↗
PubMed2005

High-performance liquid chromatography determination of alpha1-acid glycoprotein in small volumes of plasma from neonates.

In order to investigate how the alpha1-acid glycoprotein (AGP) concentrations of neonates change in response to surgical stress, a simple high-performance liquid chromatography (HPLC)-assay for the measurement of alpha1-acid glycoprotein levels was developed. A fraction containing alpha1-acid glycoprotein was isolated from the bulk of plasma protein by addition of 0.6M perchloric acid and was then analysed directly on a short PLRP-S 4000A reversed phase column column. The method was validated by analysis of pooled plasma from healthy adults both in comparison with a calibration curve and by standard additions. The procedure was able to isolate alpha1-acid glycoprotein rapidly (<30 min) and required only 50 microl of plasma. The mean extraction recovery was 79.1% (CV 6.4%). The within-run precision for the analysis of three replicates of quality control sample ranged from +/-1.2 to +/-3.8% and the between-run precision was +/-6.1%. The method was linear (r(2)=0.988) over a concentration range from 6 to 100.0 mg/100 ml. The AGP levels in neonatal samples ranged from 25 to 93 mg/100 ml.

Adult↗
PubMed1983

Determination of urinary 5-S-cysteinyldopa by high-performance liquid chromatography.

A high-performance ion-pair liquid chromatographic method with electrochemical detection is described, which is suitable for routine determination of urinary 5-S-cysteinyldopa. The clean-up procedure includes a first purification step on the cation exchanger AG 50 W (H +). After desorption from the resin at moderately raised pH the catecholic amino acid is adsorbed on alumina at pH 8.6, washed and finally desorbed by elution with perchloric acid. By the combined clean-up procedures, easily oxidized compounds are eliminated, which otherwise cause a number of interfering peaks in the chromatography. The synthesis of 5-S-cysteinyl-L-3,4-dihydroxyphenyl [2,3-3H]alanine is described, and this tritium-labelled 5-S-cysteinyldopa is used to determine the recovery in the sample. The precision (C.V. = 5.7% at low and C.V. = 4.9% at high 5-S-cysteinyldopa concentration) and recovery (105.0 +/- 8.6%) were satisfactory. The mean urinary excretion was 0.34 +/- 0.13 (S.D.) mumol per 24 h (range 0.02-0.58 mumol per 24 h) in healthy subjects (n = 24) and in patients with melanoma metastates (n = 13) the excretion ranged from 0.9 to 4.8 mumol per 24 h.

Chromatography, High Pressure Liquid↗
PubMed1995

Automated determination of inorganic mercury in blood after sulfuric acid treatment using cold vapour atomic absorption spectrometry and an inductively heated gold trap.

Inorganic mercury (InoHg) in whole blood and erythrocytes was determined by cold vapour atomic absorption spectrometry (CVAAS) after overnight treatment with sulfuric acid at 45 degrees C and reduction with SnII in the acidic mixture. Total mercury (TotHg) was determined after digestion with a mixture of nitric and perchloric acids. Mercury vapour was preconcentrated on an amalgamation trap made of gold wire. The mercury was rapidly released by inductive heating of the trap. InoHg could be determined specifically in the presence of methylmercury (MeHg). The concentration of MeHg could be calculated by subtracting the concentration of InoHg from that of TotHg. Calculated concentrations of MeHg in erythrocytes showed a strong correlation with the results of a gas chromatographic method, though a discrepancy in calibration was indicated. The detection limits (3 s) in blood (0.5 g) were 0.06 ng g-1 for TotHg and 0.04 ng g-1 for InoHg and S(r) for a 5 ng g-1 whole blood sample was 2% (n = 10) for both TotHg and InoHg.

Autoanalysis↗
PubMed1990

Analysis of purine nucleotides in muscle tissue by HPLC.

Optimal conditions for simultaneous analysis of the purine nucleotides adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine, adenosine, hypoxanthine, xanthine and uric acid in muscle samples by high-performance liquid chromatography (HPLC) were evaluated. A neutralized perchloric acid extract of freeze-dried human or rat skeletal muscle tissue was injected on to a reversed-phase silica column and eluted by a gradient composed of ammonium dihydrogen phosphate buffer and methanol. Good resolution for all the nucleotides was achieved within a retention time of about 20 min. Linearity for each of the nucleotides within the concentration intervals obtained in the samples was demonstrated. Purity of each peak was verified by use of the photodiode array technique. Reproducibility for biological samples with variation coefficients below 3.6% for ATP, ADP, AMP, inosine and hypoxanthine and 6.7% for IMP was obtained. The stability of the compounds after extraction was specifically addressed. Storing of frozen extracts at -20 degrees C for 24 h gave acceptable values, while storage for 7 days cannot be recommended. Storage of unfrozen extracts at 4 degrees C was acceptable for (up to) 7 h. This technique provides a sensitive, convenient and reliable method for simultaneous analysis of a large number of purine nucleotides in small skeletal muscle biopsies, provided that certain precautions are taken with respect to the instability of these metabolites.

Animals↗
PubMed1984

[Significance of certain neoplastic markers in a series of patients with lung cancer].

Perchloric acid soluble proteins (PPS) and their content of N-acetylneuraminic acid (NANA) may serve as valuable tumor markers for a variety of malignant neoplasms. To evaluate their clinical significance, PPS, NANA and carcino-embryonic antigen (CEA) were measured in 32 patients with lung cancer. High PPS (greater than or equal to 0,73 mg/ml) and NANA (greater than or equal to 96 micrograms/ml) levels occurred in 8 of 50 (16%) healthy volunteers and respectively in 22% and 54% of patients. CEA levels were high (greater than or equal to 3 ng/ml) in 1 out of 21 (5%) healthy volunteers and in 83% of the patients; 84% of the patients showed an elevation of NANA and of CEA. The highest values of the three markers seem to be associated with extensive disease but no statistically significant difference has emerged from the comparison of patients with limited disease with the ones with extensive involvement. Changes of the tumor mass correlate with changes of serum levels of PPS, NANA and CEA. It is concluded that CEA determination is clinically valuable in lung cancer, while PPS and NANA do not provide greater information.

Adult↗
PubMed1993

Extraction and determination of biogenic amines in fermented sausages and other meat products using reversed-phase-HPLC.

A convenient method is described for the analysis of biogenic amines (BA) by means of reversed-phase-HPLC. The method is characterized by multi-channel UV detection (diodearray), subsequent post-column derivatization with o-phthaldialdehyde and 3-mercaptopropionic acid, and fluorescence detection. For the analysis of meat products and especially fermented sausages an optimized perchloric acid extraction process was introduced to determine putrescine, cadaverine, histamine, tyramine and 2-phenylethylamine. BA recoveries from meat ranged between 96 and 113% with a detection limit for amines of 0.5 mg/kg.

Amino Acids↗
PubMed2005

The determination of ferric iron in plants by HPLC using the microbial iron chelator desferrioxamine E.

Common methods for plant iron determination are based on atomic absorption spectroscopy, radioactive measurements or extraction with subsequent spectrophotometry. However, accuracy is often a problem due to background, contamination and interfering compounds. We here describe a novel method for the easy determination of ferric iron in plants by chelation with a highly effective microbial siderophore and separation by high performance liquid chromatography (HPLC). After addition of colourless desferrioxamine E (DFE) to plant fluids, the soluble iron is trapped as a brown-red ferrioxamine E (FoxE) complex which is subsequently separated by HPLC on a reversed phase column. The formed FoxE complex can be identified due to its ligand-to-metal charge transfer band at 435 nm. Alternatively, elution of both, DFE and FoxE can be followed as separate peaks at 220 nm wavelength with characteristic retention times. The extraordinarily high stability constant of DFE with ferric iron of K = 10(32) enables extraction of iron from a variety of ferrous and ferric iron compounds and allows quantitation after separation by HPLC without interference by coloured by-products. Thus, iron bound to protein, amino acids, citrate and other organic acid ligands and even insoluble ferric hydroxides and phosphates can be solubilized in the presence desferrioxamine E. The "Ferrioxamine E method" can be applied to all kinds of plant fluids (apoplasmic, xylem, phloem, intracellular) either at physiological pH or even at acid pH values. The FoxE complex is stable down to pH 1 allowing protein removal by perchloric acid treatment and HPLC separation in the presence of trifluoroacetic acid containing eluents.

Chelating Agents↗
PubMed1987

Determination of fluorescent diamidines in plasma of experimental animals by high-performance liquid chromatography.

The fluorescent diamidines (E)-2,2'-vinylenedi-1-benzo [b] furane-5-carboxamidine dihydrochloride (I) and 2-[2-(6-amidinoindole-2-yl)-(E)-vinyl]-1-benzofurane-5-ca rbo xamidine dihydrochloride (II) were determined in the plasma of experimental animals by high-performance liquid chromatography with a mobile phase of methanol-water (60:40, v/v) containing 0.005 M octanesulphonic acid and 0.003 M dimethyloctylamine. Samples were prepared by precipitation of plasma proteins with methanol-perchloric acid. Quantitation was performed by measuring the peak heights after monitoring the native fluorescence. The assay was linear over the range 5-750 ng/ml for I and 5-500 ng/ml for II, with limits of determination of 2.5 ng/ml for I and 1.5 ng/ml for II. Coefficients of variation were below 10% at all concentrations studied.

Amidines↗
PubMed1984

High-performance liquid chromatographic analysis of S-adenosylmethionine and its metabolites in rat tissues: interrelationship with changes in biogenic catechol levels following treatment with L-dopa.

A method is described for the simultaneous analysis of S-adenosylmethionine (SAM) and its metabolites, S-adenosylhomocysteine (SAH) and decarboxylated S-adenosylmethionine along with the natural polyamines, putrescine, spermidine and spermine. The separation is obtained by a reversed-phase ion-pair liquid chromatographic procedure with gradient elution followed by dual detection. The UV absorbance at 254 nm is used for the analysis of SAM and of the SAM metabolites, whereas the polyamines and some major amino acids, e.g., methionine, tyrosine and tryptophan, are analyzed by fluorescence detection after UV-cell derivatization with o-phthalaldehyde. A separate ion-pair reversed-phase high-performance liquid chromatographic (HPLC) procedure using isocratic elution and electrochemical detection is employed to analyse in the same tissue extracts the catechols and 5-hydroxyindoles, 3,4-dihydroxyphenylalanine (DOPA), dopamine, norepinephrine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 4-hydroxy-3- methoxyphenylalanine , tryptophan, 5-hydroxytryptophan, serotonin and 5- hydroxyindolacetic acid. The sample preparation for the two HPLC procedures requires only homogenization of the tissues in perchloric acid and centrifugation before injection onto the column. The two chromatographic procedures have been applied to study the interrelationship, in various tissues of rats, between the SAM and SAH levels and the biogenic catechols after different treatments with L-DOPA alone or in combination with alpha- monofluoromethyl -DOPA, a potent enzyme-activated irreversible inhibitor of aromatic L-amino acid decarboxylase.

Adrenal Glands↗
PubMed1996

Highly sensitive and simple liquid chromatographic determination in plasma of B6 vitamers, especially pyridoxal 5'-phosphate.

A simple and sensitive high-performance liquid chromatographic method for measuring the major vitamers of vitamin B6, i.e. pyridoxal and pyridoxal 5'-phosphate (PLP), and 4-pyridoxic acid (4-PA) in plasma was developed. The vitamers and 4-PA from plasma were extracted with 0.8 mol/l perchloric acid. The separation by HPLC is accomplished using an ODS reversed-phase column and a mobile phase of 0.1 mol/l potassium dihydrogen phosphate containing 0.1 mol/l sodium perchlorate, 0.5 g/l sodium bisulfite adjusted to pH 3, at a flow-rate of 1.0 ml/min. The vitamers and 4-PA were eluted within 13 min and their concentration is determined with a fluorometric detector (excitation, 300 nm; emission, 400 nm). In this method, PLP in plasma can be determined with high sensitivity using derivatization with sodium bisulfite in the mobile phase.

Animals↗
PubMed2004

Protic acid (HClO4 supported on silica gel)-mediated synthesis of 2,3-unsaturated-O-glucosides and a chiral furan diol from 2,3-glycals.

Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good alpha selectivity. Primary, secondary, and allylic alcohols, phenols, and thiols react with 3,4,6-tri-O-acetyl glucal with equal ease. In addition to this, a chiral furan diol is obtained from unprotected D-glucal or D-galactal in good yields.

Calcium Gluconate↗
PubMed1973

The use of sodium perchlorate in deproteinization during the preparation of nucleic acids.

Sodium perchlorate in high concentrations will remove from solution the detergent sodium dodecyl sulphate and protein complexed with it. This and the failure of proteins to be precipitated by ethanol from solutions containing a high concentration of sodium perchlorate can be utilized as efficient, rapid and simple deproteinization procedures during the preparation of nucleic acids.

Adenine↗
PubMedDate not supplied

Uncovering the unfoldome: enriching cell extracts for unstructured proteins by acid treatment.

A method to enrich cell extracts in totally unfolded proteins was investigated. A literature search revealed that 14 of 29 proteins isolated by their failure to precipitate during perchloric acid (PCA) or trichloroacetic acid (TCA) treatment where also shown experimentally to be totally disordered. A near 100 000-fold reduction in yield was observed after 5% or 9% PCA treatment of total soluble E. coli protein. Despite this huge reduction, 158 and 142 spots were observed from the 5% and the 9% treated samples, respectively, on silver-stained 2-D SDS-PAGE gels loaded with 10 microg of protein. Treatment with 1% PCA was less selective with more visible spots and a greater than 3-fold higher yield. A substantial yield of unprecipitated protein was obtained after 3% TCA treatment, suggesting that the common use of TCA precipitation prior to 2-D gel analysis may result in loss of unstructured protein due to their failure to precipitate. Our preliminary analysis suggests that treating total protein extracts with 3-5% PCA and determining the identities of soluble proteins could be the starting point for uncovering unfoldomes (the complement of unstructured proteins in a given proteome). The 100 000-fold reduction in yield and concomitant reduction in number of proteins achieved by 5% PCA treatment produced a fraction suitable for analysis in its entirety using standard proteomic techniques. In this way, large numbers of totally unstructured proteins could be identified with minimal effort.

Bacterial Proteins↗
PubMed1999

The Influence of Iodide Adsorption on Copper Underpotential Deposition on Polycrystalline Palladium Electrodes in Mildly Acidic Solutions.

The effects of I- adsorption on the electrodeposition (under and overpotential deposition) of Cu on polycrystalline Pd electrodes were studied in dilute perchloric acid solutions at 18 degreesC. It had been found that Cu underpotential deposition on polycrystalline Pd exhibits different potentiodynamic features, which are characteristic of defined crystallographic planes of Pd. However, these features varied when the voltammograms were performed in the presence of strongly adsorbable anions, such as I-. In spite of having found a partial inhibition of the Cu voltammetric features in the presence of I-, we calculated integer numbers in the electron transfer to Cu2+ and I- ions. The change in the values of Cu massive deposition potential due to the presence of I- was caused by the appearence of a new electrode, that is, the Cu/CuI/I- interface. Copyright 1999 Academic Press.

Journal Article↗