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At least 19 recordsLinked to original sources
PubMedDate not supplied

Stereoselective reduction of C-2 substituted steroid C-3 ketones with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride and sodium borohydride.

The effect of C-2 substitution on the stereoselective reduction of steroid C-3 ketones with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride and sodium borohydride was investigated. The C-2 mono- and di-substituted chloro and methyl derivatives were predominantly reduced to one of the epimeric alcohols. The 2 alpha-chloro and 2 alpha-methyl derivatives of 17 beta-acetoxy-5 alpha-androstan-3-one undergo stereoselective reduction with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride to the axial (3 alpha) alcohol as observed in the unsubstituted compound, whereas sodium borohydride gives predominantly the equatorial (3 beta) alcohol. The 2 beta-chloro, 2 beta-methyl, 2,2-dichloro, and 2,2-dimethyl derivatives are reduced predominantly to the equatorial (3 beta) alcohol by both reagents.

Borohydrides↗
PubMed1984

The effect of mild alkali and alkaline borohydride on the carbohydrate and peptide moieties of fetuin.

In the light of recent reports, based on radioactive labelling studies, that substantial amounts of N-linked oligosaccharides are released from protein under the mild-alkaline borohydride degradation conditions that are usually used to release O-linked oligosaccharides, we have investigated by chemical methods the effects of alkali alone and alkaline borohydride on the carbohydrate and peptide moieties of fetuin. The chromatographic profiles on Sephadex G50 columns, of the hexose- and ninhydrin-positive components of the native and Pronase-treated glycoprotein have been compared with those obtained after treatment with mild alkali alone (0.05 M-NaOH, 50 degrees C, 16 h) or mild-alkaline borohydride (0.05 M-NaOH containing 1 M-NaBH4, 50 degrees C, 16 h). Composition and methylation analyses have been performed on carbohydrate-containing peaks and the following conclusions were drawn: mild alkali treatment alone liberated a minor hexose- and ninhydrin-positive component and mild-alkaline borohydride treatment gave a major hexose-containing peak: both of these co-chromatographed on a Sephadex G50 column with Pronase glycopeptides. The polypeptide backbone was totally broken down by the alkaline borohydride treatment. The presence of released N-linked chains after alkaline borohydride treatment was confirmed. However, from the carbohydrate composition it was calculated that no more than 10-20% of the N-linked chains were released from protein. The results of methylation analysis have raised the possibility that this release is in part due to cleavage of the chitobiosyl core.

Asialoglycoproteins↗
PubMed1989

The effect of alkaline borohydride treatment on N-linked carbohydrates of glycoproteins.

The effects of treatments of the glycoprotein ribonuclease-B, the proteins ribonuclease-A and myoglobin, and the glyco-amino acid GlcNAc beta(1-N)Asn with alkali, alkaline sodium borohydride, and aqueous sodium borohydride were systematically studied as a function of the concentration of the reagents, the temperature, and the length of the treatment. High-field 1H-NMR spectroscopy, chromatographic methods and amino-acid analysis were used to characterize products of the treatments of the various compounds. Our results indicate that mild alkaline borohydride treatment, as well as aqueous borohydride treatment alone, is capable of extensively degrading polypeptides and of partially releasing the N-linked glycans from ribonuclease-B. Initially, glycopeptides are produced, the peptide portion of which consists of several amino acids, which are further hydrolyzed to yield a mixture of glyco-asparagines and oligosaccharide-alditols in the ratio of approximately 4:1. Strong alkaline borohydride treatment of ribonuclease-B is capable of completely releasing the N-linked carbohydrates as oligosaccharide-alditols.

Acetylglucosamine↗
PubMed1987

Effect of borohydride reduction on antibodies.

The effect of borohydride reducing reagents on monoclonal and polyclonal antibodies was examined by enzyme-linked immunosorbent assay (ELISA). Each antibody showed different stability characteristics to the reducing reagents. Sodium cyanoborohydride was at least five times milder toward immunological activity than sodium borohydride, however, sodium cyanoborohydride with a catalytic amount of metal ion (Zn2+ or Al3+) can be as harsh as sodium borohydride. Activated hydrophobic borohydrides, 9BBN-pyridine, did not have any advantages in respect to the stabilities of antibodies. Antibodies to be used for immunosorbent purification must be evaluated individually to determine whether their structure is stable to immobilization reagents and conditions prior to their linkage to the column support.

Antibodies↗
PubMed1995

Partial restoration of inactivated ribosomes with sodium borohydride or amino acids.

The aldehyde radical of ribose C1' at position 4324 in rat liver 28S rRNA generated by RNA N-glycosidase was either reduced to an hydroxyl group by sodium borohydride or converted into aldimine through a nucleophilic addition of amino acid used as a primary amine. Analysis of the R-fragment of 28S rRNA by polyacrylamide gel electrophoresis showed that the reduction of aldehyde to an hydroxyl group with sodium borohydride was highly specific. The protein synthesis activity of modified ribosomes was partially restored with the removal of the active aldehyde by sodium borohydride or amino acid. Reduction of aldehyde with sodium borohydride restored 43.1% of the protein synthesis activity. Among the twenty natural amino acids tested, tryptophan and histidine could restore 57.4% and 42.1% of the ribosome activity when brome mosaic virus RNA was used as mRNA. We came to the conclusion that the active aldehyde radical at position 4324 of 28S rRNA in modified ribosome may cause the inactivation of the ribosome for protein synthesis.

Algal Proteins↗
PubMed1986

Mechanism of ubiquitin carboxyl-terminal hydrolase. Borohydride and hydroxylamine inactivate in the presence of ubiquitin.

Ubiquitin (Ub) carboxyl-terminal hydrolase (E) catalyzes the hydrolysis, at the Ub-carboxyl terminus, of a wide variety of C-terminal Ub derivatives. We show that the enzyme is inactivated by millimolar concentrations of either sodium borohydride or hydroxylamine, but only if Ub is present. We have interpreted these results on the assumption that the hydrolase mechanism is one of nucleophilic catalysis with an acyl-Ub-E intermediate. The borohydride-inactivated enzyme has the following properties. It is a stoichiometric complex of E and Ub containing tritium from sodium boro[3H]hydride. This complex is stable at neutral pH in 5 M urea and can be isolated on the basis of size on a sieving column, but a labeled product the size of Ub is released under more strongly denaturing conditions. The "Ub" released in acid is Ub-carboxyl-terminal aldehyde, based on the observations that: it contains the tritium present in the reduced complex and it is able to form the inactive enzyme from a stoichiometric amount of fresh enzyme, and inactivation is accompanied by E-Ub adduct formation; it has chemical properties expected of an aldehyde: after a second reduction of the Ub released with boro[3H]hydride and complete acid hydrolysis, tritium counts are found in ethanolamine (the carboxyl-terminal residue of Ub is glycine). These results suggest that enzyme and Ub combine in an equilibrium reaction to form an ester or thiol ester adduct (at the Ub-carboxyl terminus), and that this adduct is trapped by borohydride to give a very stable inactive E-Ub (thio) hemiacetal which is unable to undergo a second reduction step and which can release Ub-aldehyde in mild acid. Inactivation in the presence of hydroxylamine of hydrolase occurs once during hydrolysis of 1200 molecules of Ub-hydroxamate by the enzyme. The hydrolysis/inactivation ratio is constant over the range of 10-50 mM hydroxylamine showing that forms of E-Ub with which hydroxylamine and water react are different and not in rapid equilibrium. The inactive enzyme may be an acylhydroxamate formed from an E-Ub mixed anhydride generated from the E-Ub (thiol) ester inferred from the borohydride study. A direct radioactive assay for the hydrolase has been developed using the Ub-C-terminal amide of [3H]butanol-4-amine as substrate.

Animals↗
PubMed1979

The pH dependence of borohydride as an aldehyde reductant.

The aldehyde-reducing capacity of borohydride has been investigated in the sequence periodic acid-borohydride-periodic acid-Schiff and variants. Densitometric studies on rat colonic mucins show that borohydride incompletely blocks periodate-engendered aldehydes unless the pH is above 8.2. Below this value, some aldehydes are not reduced and continue to be Schiff-stainable, while others are subsequently gerenated by the second exposure to periodic acid. The effect is more pronounced in paraffin than in cryostat sections, but does not apply to human colonic mucins.

Aldehydes↗
PubMed1991

Removal of hydroperoxides by immobilized borohydride: a good method for purification of biochemical materials.

Borohydride was immobilized on a quaternary ammonium type anion exchange resin, Amberlite IRA-400, by an exchange reaction in N,N-dimethylformamide. The reducing ability of borohydride on the polymer beads was examined; 0.1 g resin was applied for about 30 min to 3 ml solutions of hydrogen peroxide, ethyl hydrogen peroxide, and peracetic acid, at a concentration of approximately 40 mM, m-chloroperbenzoic acid (3.13 mM), and 5-phenyl-4-pentenyl-1-hydroperoxide (1 mM), respectively. The solutions were then assayed for remaining hydroperoxide by use of horseradish peroxidase or prostaglandin H synthase. In addition, the effect of treatment on the ability of 5-phenyl-4-pentenyl-1-hydroperoxide to initiate the cyclooxygenase activity of prostaglandin H synthase was investigated. Results indicated that immobilized borohydride is very efficient in removing hydroperoxides. It can be used in either organic or aqueous media. It is convenient for both large and small scales, particularly important for purification of biochemical materials.

Borohydrides↗
PubMed1987

Detection of oxidized lipid-modified erythrocyte membrane proteins by radiolabeling with tritiated borohydride.

Human erythrocyte ghosts treated with tert-butyl hydroperoxide or ADP-Fe3+ incorporated radioactivity on reduction with tritiated borohydride. The tritium incorporation closely correlated with membrane lipid oxidation as assessed by the formation of thiobarbituric acid-reactive substances and fluorescent substances. Treatment of ghosts with the inducers in the presence of butylated hydroxytoluene, thiourea, or desferrioxamine suppressed the tritium incorporation in the subsequent reduction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the tritiated ghost proteins showed that the label was incorporated into the intermolecularly cross-linked and the uncross-linked proteins of bands 1, 2, 3, 4.1, 4.2, 5 and 6, and into the noncross-linked glycophorin A (PAS-1). Glycophorin A was hardly cross-linkable but modified during membrane lipid oxidation. Possible candidates for producing borohydride-reducible functions in the proteins are various mono- and bifunctional aldehydes, as well as those for producing fluorescence and cross-links. A part of thiobarbituric acid-reactive or fluorescent substances may be involved in borohydride reduction and tritium labeling.

Aldehydes↗
PubMed1982

The resistance of glyoxylic acid induced catecholamine fluorescence to sodium borohydride reduction.

The borohydride reduction of glyoxylic acid induced fluorescence in noradrenergic and DOPA-minergic nervous structures and in amines in model experiments was studied. Both DOPAmine and noradrenaline fluorescences were resistant to borohydride reduction differing thus from the formaldehyde-induced fluorescence. Thus when the specificity of glyoxylic acid induced fluorescence is in doubt, other tests than borohydride reduction of the fluorescence must be employed.

Animals↗
PubMedDate not supplied

Application of pelletized sodium borohydride in the spectrophotometric determination of arsenic.

The spectrophotometric determination of arsenic using sodium borohydride in pellet form, with excipients as the reducing agent and arseine former, has been studied. The use of pelletized sodium borohydride allows the formation of arsenic diethyldithiocarbamate and enables an accurate application of the method without the use of other reagents. The gradual reducing action of the pelletized sodium borohydride, together with the release of hydrogen thus forming arsine with As(III), is the main advantage of this procedure. The arsine thus formed bubbles through the chloroform solution of silver diethyldithiocarbamate to form the complex that allows the determination of the arsenic by visible spectrophotometry.

Animals↗
PubMed1972

Specific radioactive labeling of terminal n-acetylgalactosamine of glycosphingolipids by the galactose oxidase-sodium borohydride method.

The galactose oxidase-sodium borohydride method was used to specifically label the terminal N-acetylgalactosamine of three glycosphingolipids, Gm2-ganglioside, asialo-Gm2-ganglioside, and globoside. All of the compounds showed a minimum of 95% radiopurity, and generally more than 90% of the total radioactivity was located in the terminal galactosamine moiety. Globoside and asialo-Gm2-ganglioside were labeled to high specific activities comparable with those of the sphingolipids with a terminal galactose moiety, labeled with the same procedure. These labeled compounds were well suited as substrates for the study of specific sphingolipid N-acetylgalactosaminidase. Gm2-ganglioside, however, was a poor substrate for galactose oxidase, and its specific activity was only a small percentage of the others. Furthermore, because of the low specific activity of the galactosamine moiety, it was necessary to pretreat Gm2-ganglioside with unlabeled sodium borohydride to reduce the nonspecific labeling of other portions of the molecule. The use of labeled sodium borohydride of a very high specific activity may yield specifically labeled Gm2-ganglioside suitable for metabolic studies. Thus, the method is useful for labeling not only terminal galactose but also terminal N-acetylgalactosamine of glycosphingolipids.

Alcohol Oxidoreductases↗
PubMed1977

The use of borohydrides of alkaline metals in the volumetric analysis of medicaments.

The possibility and conditions of determination of weak acid type medicaments were examined, using aqueous and non-aqueous sodium borohydride volumetric solutions. The process and control of titration were carried out potentiometrically and visually using acido-basic indicators. It was shown that for practical applications sodium borohydride aqueous solutions are more suitable. Analytical methods of determination for medicaments from the group of sulphonamides and barbiturates and their sodium salts, for phenylbutazone and kebuzone, salicylamide, nalidixic acid and theophylline were elaborated. All results were in good agreement with methods used in CsL 3, or other alternative methods. The advantages of the proposed method are good stability of sodium borohydride volumetric solution and insensitivity of titrated systems to CO2 from the atmosphere, which is unavoidable with alkalimetric titrations in aqueous and non-aqueous systems. An hypothesis has been suggested to explain the probable reactive mechanism of determination, supported by results obtained with the proposed analytical methods using a medium of suitable organic solvents with a maximum content of ca. 15% water near the final point of titration.

Barbiturates↗
PubMed1978

Differential borohydride assay for conjugated ketosteroids: improvement with propylene glycol.

A previously developed differential UV assay for 3-one-4-ene steroids involving reduction with sodium borohydride was frequently found to be less than 100% complete. Such incomplete reduction can be mimicked by additions of sodium metaborate, a product of the hydrolysis of sodium borohydride, to the reaction system. Complete reduction can be achieved by adding propylene glycol to the reduction system. The phenomenon was studied using halcinonide as a model.

Administration, Topical↗
PubMed1994

Thiobarbiturate and fructosamine assays: significance and interest of the borohydride blank.

The acute-phase reaction (APR) induces the production by the liver of short-lived glycoproteins. The carbohydrate moiety of these proteins is thought to interfere with the thiobarbiturate (TBA) and nitroblue tetrazolium colorimetric tests which are used for assaying non-enzymatic glycosylation (NEG) of serum proteins. The aim of the present study was to assess the effect of the APR on the specificity of the colorimetric tests in non-diabetic and diabetic subjects. A positive correlation was found between C-reactive protein (CRP), an APR glycoprotein, and non-specific TBA reactivity as determined after borohydride reduction (BH4-resistant TBA, BR-TBA), both in non-diabetics (r = 0.61; P < 0.01) and diabetics (r = 0.68; P < 0.01). The BH4-sensitive specific TBA (SP-TBA) was not influenced by glycoproteins, and its increase in diabetics was correlated with the nitroblue tetrazolium assay (r = 0.89; P < 0.01). An independent effect of diabetes and APR on non-specific TBA was also demonstrated, suggesting an effect of hyperglycaemia on both protein glycation and glycosylation. TBA with borohydride reduction is an attractive tool for the study of complex glycoproteins in diabetes.

Acute-Phase Reaction↗
PubMed1995

Analysis of serine/threonine-linked oligosaccharides derived by alkaline-borohydride treatment of mucin glycoproteins electroblotted onto membranes: comparison of the saccharide profiles of the 390 kDa and 350 kDa forms of epitectin.

Alkaline borohydride treatment is widely used for the release of carbohydrate moieties from O-glycosylated glycoproteins and mucins. We have adapted this procedure to micro quantities of glycoproteins blotted on membranes. After electrophoresis and transfer to nitrocellulose, nylon or polyvinylidene difluoride membrane, alkaline borohydride treatment was done directly on glycoprotein containing areas of membrane which were cut out with the aid of guide strips stained with Coomassie Blue or lectin-digoxigenin. In combination with standard saccharide fractionation techniques, this procedure can be used to characterize the oligosaccharides of mucins or mucin-type glycoproteins that are separated by gel electrophoresis from crude sources. Using this approach we have characterized the saccharides derived from the two species of epitectin, a malignancy-associated mucin type glycoprotein, isolated from metabolically labelled H.Ep2 cells.

Antigens, Tumor-Associated, Carbohydrate↗