SEARCH · PubMed Health

Results for “BORIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources

PubMedDate not supplied

High-performance capillary electrophoretic separation of carbohydrates with indirect UV detection using diethylamine and borate as electrolyte additives.

The separation of underivatized carbohydrates was investigated using capillary zone electrophoresis with indirect UV detection based on sorbic acid or riboflavin. In comparison with sodium hydroxide, the separation of carbohydrates was greatly improved using diethylamine (DEA) as an electrolyte additive. Since the conductivity of DEA is much lower than that of sodium hydroxide, a stable baseline and a 3-5 times improvement in separation efficiency was observed at a pH as high as 12.6. It was found that DEA reduced the electrophoretic mobility of carbohydrates by formation of ion-pairs, and also reduced the electroosmotic flow by masking the silanol groups at the capillary surface. Many monosaccharides, including glucose, rhamnose, mannose, and fructose, which have very similar pKa values, were completely separated using 5% DEA at pH 12.6. The separation of di- and trisaccharides using indirect detection with a borate buffer at pH 9.5 was also investigated. The separation of disaccharides was greatly improved with borate complexation using riboflavin as a background electrolyte (BGE) over the sodium hydroxide and DEA electrolyte system with sorbic acid as BGE. The resolution of carbohydrates increased as pH increased, and sucrose, trehalose, raffinose, and maltotriose were successfully separated at pH 11.8.

Boric Acids↗

PubMed2002

A non-cryogenic method for the preparation of 2-(indolyl) borates, silanes, and silanols.

2-Indolyl borates are prepared via addition of LDA to a mixture of N-Boc-indole and triisopropyl borate at 0-5 degrees C. Following acidic hydrolysis, the boronic acids are isolated by crystallization in good to excellent yield (73-99%). The method is quite general, tolerating a wide range of functional groups, and also provides access to 2-silyl derivatives (80-91%).

Boric Acids↗

PubMed1986

Recovery of soluble proteins from glanded cotton tissues with amines.

A simple soluble protein extraction method was developed for glanded cotton (Gossypium hirsutum L.) tissues. Gossypol, a major component of glands, is known to crosslink and precipitate proteins in cotton tissue homogenates. Established phenolic removal reagents were evaluated as gossypol binding agents and found to be less than effective in enhancing cotton leaf-soluble protein recovery. Several other amines, including a number of affinity support bound amines, were tested and found relatively ineffectual when compared with urea as cotton protein protectants. Urea and (NH4)2SO4, the next most active agent found in the study, were compared on both whole-leaf homogenates and artificial mixtures containing known quantities of poly-L-lysine and a clathrate of gossypol and acetic acid. Urea treatment resulted in both an increased number of stained bands and more concentrated staining of bands than any other treatment on polyacrylamide gels. Selected enzymes demonstrated increased activities in urea homogenates compared with other treatments.

Amines↗

PubMed1991

Inactivation of the RTEM-1 cysteine beta-lactamase by iodoacetate. The nature of active-site functional groups and comparisons with the native enzyme.

The pH-rate profile for inactivation of the RTEM-1 cysteine beta-lactamase by iodoacetate supports previous evidence [Knap & Pratt (1989) Proteins Struct. Funct. Genet. 6, 316-323] for the activation of the active-site thiol group by adjacent functional groups. The enhanced reactivity of iodoacetate, with respect to that of iodoacetamide, suggests the influence of a positive charge in the active site. The reactivity of iodoacetate is not affected by dissociation of an active-site functional group of pKa 6.7, which increases the reactivity of neutral reagents, probably because of a compensation phenomenon; it is, however, lost on dissociation of an acid of pKa 8.1. It is concluded that the active cysteine beta-lactamase has four functional groups at the active site, one nucleophilic thiolate of Cys-70, one neutral acid (most probably the carboxy group of Glu-166, from the crystal structures) and two cationic residues (most probably Lys-73 and Lys-234). A comparison of these results with the pH-dependence of reactivity of the native RTEM-2 beta-lactamase suggests that the active form of the latter enzyme is also monocationic, although the nucleophile (Ser-70) is likely to be neutral in this case and the carboxylic acid dissociated. A mechanism of class A beta-lactamase catalysis is discussed where the Glu-166 carboxylate acts as a general base/acid catalyst and Lys-73 is principally required for electrostatic stabilization of the anionic tetrahedral intermediate.

Binding Sites↗

PubMed1971

Four-directional-development thin-layer chromatography of lipids using trimethyl borate.

Solvent mixtures containing trimethyl borate virtually eliminated the pronounced interconversion of 1,2- and 1,3-dipalmitins during their resolution by thin-layer chromatography on Silica Gel G. With trimethyl borate, an average of 1-2% of 1,2-dipalmitin was converted to 1,3-dipalmitin. A four-directional-development TLC procedure incorporating trimethyl borate resolves cholesteryl glucoside, ceramides, monogalactosyl diglyceride, 1- and 2-monopalmitin, palmitic acid, cholesterol, 1,2- and 1,3-dipalmitin, tripalmitin, methyl palmitate, cholesteryl palmitate, beta-carotene and some of its degradation products, squalene, and tetracosane. Digalactosyl diglyceride, phosphatidic acid, phosphatidylglucose, cerebrosides, and other phospholipids remain near the origin. A mixture containing triolein, 1,2- and 1,3-diolein, 1- and 2- monoolein, oleic acid, and cholesterol was resolved in one dimension. A similar series of palmitic-containing neutral lipids was also resolvable in one dimension. These procedures were applied to the TLC of human sera lipids.

Acetates↗

PubMed2002

Selective detection of biogenic amines using capillary electrochromatography with an on-column derivatization technique.

A selective detection method for biogenic amines present in highly complex matrixes was devised by employing both electrokinetic injection and on-column-derivatization capillary electrochromatographic methods. The on-column derivatization capillary electrochromatography system was evaluated by use of a capillary column (total length of 45 cm, effective length of 25 cm) fabricated using a 100-mcirom (i.d.) fused-silica capillary tube packed with 5-microm (i.d.) ODS particles that were tolerant of an alkaline environment. The column was filled with a run buffer consisting of a derivatization reagent, o-phthalaldehyde/2-mercaptoethanol, in a mixture of borate buffer (pH 10). After electrokinetic injection of a mixture of five biogenic amines (histamine, serotonin, tyramine, putrescine, cadaverine) as a test sample, the free amines entered into the anodic site of the capillary column and started to travel along the column, during which time the analytes reacted with the derivatization reagent, separated out, and were detected with an absorbance at 340 nm when high voltage was applied to the column. When this system was applied to a mixture containing 5 biogenic amines and 17 amino acids, the 5 biogenic amines plus arginine selectively entered into the capillary with the electrokinetic injection and were observed on the electrochromatogram, but none of the amino acids lacking arginine were detected. The designated method was also tested for its ability to determine the presence of biogenic amines in the crude extracts obtained from two types of aged fish.

Acetonitriles↗

PubMed2000

DNA and buffers: are there any noninteracting, neutral pH buffers?

The interaction of DNA with various neutral pH, amine-based buffers has been analyzed by free solution capillary electrophoresis, using a mixture of a plasmid-sized DNA molecule and a small DNA oligonucleotide as the reporter system. The two DNAs migrate as separate, nearly Gaussian-shaped peaks in 20-80 mM TAE (TAE, Tris-acetate-EDTA; Tris, tris[hydroxymethyl]aminomethane) buffer. The separation between the peaks gradually increases with increasing TAE buffer concentration because of differences in solvent friction between large and small DNA molecules. The two DNAs form complexes with the borate ions in TBE (Tris-borate-EDTA) buffer, with mobilities that depend on the DNA/borate ratio. In 45 mM TBE buffer, the two DNAs comigrate as a single sharp peak, with a mobility that is faster than either of the constituent DNAs in the same buffer. Hence, the mixed DNA-borate complex is stabilized by the binding of additional borate ions, possibly forming bridges between the different DNAs. The mixed DNA-borate complex is gradually dissociated into its component DNAs by increasing the TBE concentration, possibly because the borate binding sites become saturated at high buffer concentrations. Other neutral pH, amine-based buffers, such as Mops (3-[N-morpholino]propanesulfonic acid), Hepes (N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]), Bes (N,N-bis[2-hydroxyethyl]-2-aminoethanesulfonic acid), Tes (N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid), and tricine (N-tris[hydroxymethyl]methylglycine) also form complexes with DNA, giving distorted peaks in the electropherograms. The combined results indicate that borate buffers and most neutral pH, amine-based buffers interact with DNA.

Acetates↗

PubMed1991

The separation of chondroitin sulfate disaccharides and hyaluronan oligosaccharides by capillary zone electrophoresis.

We have developed techniques for the separation of unsulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-alpha-L-threo- hex-4-enopyranosyluronicacid)-D-galactose and -D-glucose), monosulfated (2-acetamido-2-deoxy-3- O-(4-deoxy-2-O-sulfo-alpha-L-threo-hex-4-enopyranosyluronic acid)-D-galactose and 2-acetamido-2-deoxy-3-O-(4-deoxy-alpha-L-threo-hex- 4-enopyranosyluronic acid)-4-sulfo-D-galactose and -6-sulfo-D-galactose),disulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-2-O-sulfo-alpha-L-threo-hex-4- enopyranosyluronic acid)-4-sulfo-D-galactose and -6-sulfo-D-galactose and 2-acet-amido-2-deoxy-3-O-(4-deoxy-alpha-L-threo-hex-4-enopy- ranosyluronic acid)-4,6-di-O-sulfo-D-galactose), and trisulfated (2-acetamido-2-deoxy-3-O-(4-deoxy-2-O- sulfo-alpha-L-threo-hex-4-enopyranosyluronic acid)-4,6-di-O-sulfo-D-galactose) isomers of chondroitin using capillary zone electrophoresis. In addition, it is possible to separate oligomers of hyaluronan by similar protocols. These techniques represent a rapid, sensitive, and reproducible technique for the assay of these molecules from digests of connective tissues.

Boric Acids↗

PubMed1976

Colorimetry of carbohydrates with m-aminophenol, and its proposed use in measurement of serum amylase activity.

In the reaction of m-aminophenol with carbohydrates in a thiourea/acetic acid reagent, addition of borate suppresses chromogen formation for hexoses and pentoses, and enhances it for disaccharides. All reaction products absorb maximally at 520 nm. The relatively greater intensity of the m-aminophenol/maltose reaction product was used in a saccharogenic method for amylase, with low blank readings. This method is compared with two dye/starch procedures.

Amylases↗

PubMed1992

Determination of diborane by adsorption sampling using modified silica gel and the chromotropic acid-HPLC method.

A method for determining atmospheric diborane in concentrations higher than 1/10 of TLV, i.e., 0.01 ppm, has been developed using the adsorption sampling method. Silica gel impregnated with potassium permanganate, synthetic resin activated carbon impregnated with or without mercury(II) chloride and activated carbon impregnated with chromate salt showed adsorption capacities larger than 18 l of 3 ppm diborane test gas when the test gas was drawn at 300 ml/min. Complete desorption of the adsorbed diborane was possible only from silica gel impregnated with potassium permanganate into a hydroxylamine hydrochloride solution. As methods for determining the desorbed boron, both the chromotropic acid-HPLC method and ICP-AES were applied. The former was more sensitive, but the latter was less influenced by coexistent substances. The most sensitive and reproducible procedure for diborane determination was as follows: diborane is collected with silica gel impregnated with potassium permanganate (0.05% (w/w)) and desorbed into hydroxylamine hydrochloride solution (400 micrograms/ml) followed by the determination of boron by the chromotropic acid-HPLC method. When diborane in 3 l of 0.1 ppm test gas was collected, the desorption efficiency was 105.3% with an RSD of 13.5%. The limit of quantitation of this method was 0.0026 ppm in 3 l air. Much lower concentrations can be determined by sampling larger amounts of air.

Adsorption↗

PubMed2005

[Restriction enzyme pattern analysis of mycobacteria DNA by capillary electrophoresis with laser induced fluorescence detection].

A new method for rapidly detecting restriction enzyme pattern of mycobacterium deoxyribonucleic acid (DNA) by capillary electrophoresis with laser induced fluorescence detection (CE-LIFD) was developed. Polymerase chain reaction was used to amplify a 439 bp fragment of 65,000 (Mr) heat shock protein gene (hsp65) of mycobacterium. After digesting the amplification products by BstE II and Hae III respectively, the patterns of enzyme cleavaged products were detected by both CE-LIFD and agarose gel electrophoresis (AGE). The experimental parameters of CE were optimized. The restriction enzyme patterns of mycobacterium DNA can be detected under the optimum electrophoresis conditions: a coated capillary column with the length of 50 cm and 100 microm i. d., electrophoresis buffer of 45 mmol/L TBE (trihydroxymethyl aminomethane (Tris)-boric acid-ethylenediaminetetraacetic acid (EDTA)) and 11 kV running voltage. The restriction enzyme patterns for eight species of mycobacteria were studied. Relative standard deviations of the relative migration times of the DNA segments were less than 3.6%. Compared with AGE, CE is more outstanding in resolution and detection time, and it can be applied as a more effective means for DNA restriction enzyme pattern analysis.

Animals↗

PubMed2005

Determination of traces of chloride and fluoride in H2SO4, H3PO4 and H3BO3 by in situ analyte distillation-ion chromatography.

A simple dual vessel in situ analyte distillation (IAD) system has been developed for suppressed ion chromatographic determination of chloride and fluoride ions in complex matrices. In IAD system, water vapours generated from the outer vessel reacts with sulfuric acid generating heat, thus favouring the quantitative distillation of chloride and fluoride within 30 min on water bath temperature (approximately 80 degrees C). The distilled analytes, as their respective acids in water, were directly injected into an ion-chromatograph. This newly developed method has been applied for analysis of trace impurities in H2SO4, H3PO4 and H3BO3. The detection limits for chloride is 8, 80 and 70ppb (w/w) for H2SO4, H3PO4 and H3BO3, respectively. For fluoride the detection limits are 6 and 60 ppb (w/w) for H2SO4 and H3PO4, respectively. The recovery of spikes for both the analytes ranged between 87 and 100%.

Boric Acids↗

PubMed1995

Capillary electrophoresis of carboxylated carbohydrates. Part 2. Selective precolumn derivatization of sialooligosaccharides derived from gangliosides with 7-aminonaphthalene-1,3-disulfonic acid fluorescing tag.

The most suitable conditions for selective precolumn derivatization of sialooligosaccharides, derived from gangliosides, with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) and the subsequent separation of the derivatives by capillary electrophoresis are described. ANDSA-sialooligosaccharide derivatives, which fluoresce at 420 nm when excited at 315 nm, were readily detected in capillary electrophoresis using an on-column lamp-operated fluorescence detector. In addition, the precolumn derivatization described here, which exploited the reactivity of the carboxylic acid group of the sialic acid residue of the oligosaccharides, replaced each weak carboxylic acid group of the parent sugar by two strong sulfonic acid groups. This allowed for electrophoresis over a wide range of pH and improved the resolution of the derivatives when compared to those obtained with underivatized sialooligosaccharides under identical separation conditions. The separation of sialooligosaccharides was best achieved when 75 mM borate, pH 10.0, was used as the running electrolyte. The derivatization and separation conditions described herein are expected to be readily transposed to the capillary electrophoresis of other sialooligosaccharides such as those derived from glycoproteins.

2-Naphthylamine↗

PubMed2005

Cationic surfactant-based polyfluorate salts: phase separation and analytical applications in the extraction and preconcentration of ionic species prior to liquid chromatography.

The liquid-solid phase separation originating from the formation of cationic surfactant-based polyfluorate salts (CSBPS) has been explored for extracting and preconcentrating ionic species. Two cationic surfactants were tested; one with aliphatic hydrocarbon tail [Cetyltrimethylammonium bromide (CTAB)]and the other containing a heterocyclic ring [Hexadecylpyridinium bromide (HPyBr)]. Phase separation possibility was investigated with the use of hexafluorophosphates (PF6-) and tetrafluoroborates (BF4-). The effect of added acid, base and salt on the phase separation and analyte extraction was also investigated. In all cases the obtained phase diagrams consisted of two regions: a homogeneous liquid region and a solid-liquid region. Analytes of hydrophilic and hydrophobic nature such as amines, amino acids and organic chromophores were used as test compounds in both their anionic and cationic forms. The respective recoveries ranged from over 90% for anionic species and in the proximity of 50% for cationic species, remaining below 20% for neutral species. Extracts from alkaline aqueous and plasma samples spiked with tyrosine and phenylalanine were also subjected to HPLC separation with UV detection with satisfactory results. On line application was also enabled using a flow through-solid phase extraction-HPLC hyphenated apparatus, thus adding the element of automatization and increased reproducibility.

Borates↗

PubMed2002

On-line coupling of capillary isotachophoresis and capillary zone electrophoresis for the determination of flavonoids in methanolic extracts of Hypericum perforatum leaves or flowers.

Five flavonoids (hyperoside, isoquercitrin, quercitrin, quercetin and rutin) were separated and determined in extracts of Hypericum perforatum leaves or flowers by capillary zone electrophoresis (CZE) with isotachophoretic (ITP) sample pre-treatment using on-line column coupling configuration. The background electrolyte (BGE) used in the CZE step was different from the leading and terminating ITP electrolytes but all the electrolytes contained 20% (v/v) of methanol. The optimal leading electrolyte was 10 mM HCl of pH* approximately 7.2 (adjusted with Tris) and the terminating electrolyte was 50 mM H3BO3 of pH* approximately 8.2 (adjusted with barium hydroxide). This operational system allowed to concentrate and pre-separate selectively the flavonoid fraction from other plant constituents before the introduction of the flavonoids into the CZE capillary. The BGE for the CZE step was 50 mM Tris buffer of pH* approximately 8.75 containing 25 mM N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid as co-ion and 55 mM H3BO3 as complex-forming agent. The ITP-CZE method with spectrophotometric detection at 254 nm was suitable for the quantitation of the flavonoids in real natural samples; kaempferol was used as internal standard. The limit of detection for quercetin-3-O-glycosides was 100 ng ml(-1) and calibration curves were rectilinear in the range 1-10 microg ml (-1) for most of the analytes. The RSD values ranged between 0.9 and 2.7% (n=3) when determining approximately 0.07-1.2% of the individual flavonoids in dried medicinal plants.

Boric Acids↗

PubMedDate not supplied

A new boron compound (guanidine biboric acid adduct) as an antitumour agent against Ehrlich ascites carcinoma in mice.

The inhibitory effects of a new boron compound of guanidine biboric acid adduct (GB) and guanidium chloride (L1) on the growth of ascites tumour in female Swiss mice were studied by monitoring the survival, tumour weight, tumour cell count, transplantability of Ehrlich ascites cells, precursor incorporation and the haematological parameters of the treated mice. 5-Fluorouracil, a known anticancer drug, was used as a positive control. The most important parameter was the survival time, which increased significantly when tumour-bearing mice were treated with the boron compound. Haematological parameters of the treated animals showed minimum toxic effects when boron was coupled with guanidine.

Animals↗

PubMed1989

Crystallographic analysis of the inhibition of porcine pancreatic elastase by a peptidyl boronic acid: structure of a reaction intermediate.

The crystal structure of porcine pancreatic elastase (PPE) complexed to carbobenzoxy-alanylisoleucine-boronic acid (ZAIB) is reported to 2.09-A resolution and refined to an R factor of 0.15. This is the first reported structural analysis of PPE with an isoleucine residu in the primary specificity pocket. The results include (1) marked displacement of the inhibitor out of the active site leading to (2) a close (2.2 A) direct contact between B (boron atom of the inhibitor) and N epsilon of His-57 and also (3) covalent bonding (1.5 A) to O gamma of Ser-195. A scheme for the mechanism of inhibition of PPE by ZAIB is proposed. A comparison with a peptidyl difluoromethyl ketone-PPE complex (Ki = 9.5 microns) is made to explain the strong inhibition of PPE by ZAIB (Ki = 0.3 micron). These results lead us to characterize this structure as a time- and space-averaged reaction intermediate, providing fresh insight into the cramped dimensions available in enzymatic catalyses.

Animals↗

PubMed2005

Capillary electrophoresis separation of a mixture of chitin and chitosan oligosaccharides derivatized using a modified fluorophore conjugation procedure.

A capillary electrophoresis (CE) method was developed for the simultaneous analysis of small chitin and chitosan oligosaccharides. For detection purposes, the oligomers were derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS), a well known fluorophore for oligosaccharides analysis. The detection was performed by laser-induced fluorescence (LIF) with an argon ion laser having an excitation wavelength of 488 nm and with emission monitored at 520 nm. Derivatization parameters such as reaction time and conditions were examined. Separation conditions were also varied by testing a range of buffer pHs and concentrations. The best conditions were found using an 80 mM borate buffer at pH 8.4. This CE-LIF optimized method was used for the analysis of an enzymatically produced oligo-chitosan sample composed of a complex mixture and having an average degree of polymerization of 3.7 monomer units and 80% deacetylation. The oligo-chitosan sample was treated with a chitin deacetylase-like enzyme, the products were derivatized with APTS, and then analyzed without purification. The goal was to determine whether the deacetylase-like enzyme could increase the extent of deacetylation of the oligo-chitosan sample.

Amidohydrolases↗