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At least 19 recordsLinked to original sources
PubMed1998

A comparison of worker exposure to inhalable and total dust, inorganic arsenic, and borates using two types of particulate sampling assemblies in a borate mining and processing facility.

This study describes a comparison of worker exposure to total and inhalable dust, inorganic As, and borates using two types of particulate sampling assemblies as part of a comprehensive industrial hygiene evaluation in a borate mining and processing facility. Employees were segmented into similar exposure groups (SEG) based on work location within the facility, job classification, and type of chemical agent. Approximately 10% of the employees from each SEG wore two personal sampling devices simultaneously for the purpose of collecting total and inhalable particulate fractions using a closed face, 37-mm mixed cellulose ester matched-weight filters (MMW), and Institute of Occupational Medicine (IOM) sampling assembly. Sample results indicated that the IOM concentrations were consistently higher than the corresponding MMW concentrations for all three agents. An analysis was performed to investigate a relationship between MMW and IOM. The data revealed correlation coefficient values of 0.72, 0.82, and 0.84 for total dust (n = 197), inorganic As (n = 137), and borates (n = 194), respectively. These positive correlation coefficients indicate that the IOM and MMW measurements are consistent with each other, and can be used for predicting exposure levels. The total dust and borate large mean ratios should be considered in developing inhalable fraction-based regulatory standards.

Air Pollutants, Occupational↗
PubMed1997

Specific interaction between 5'-aminonucleosides and borates and influence of borates on nucleoside conformations.

The unique conformation and orientational change of 5'-amino-5'-deoxyuridine in Kolthoff's buffer is discussed. From CD and NOE spectra, anomalous syn orientation of Urd-5'-NH2 might be caused by specific interaction between borates and Urd-5'-NH2, which promote the formation of hydrogen bonding between 2-carbonyl oxygen and hydrogen of 5'-amino group. This borates induced syn orientation of Urd-5'-NH2 could be applied to external stimulation control of target RNA/DNA hybridization.

Borates↗
PubMed2000

Lithium potassium borate and lithium rubidium borate: new non-linear optical crystals

The title compounds, LiKB(4)O(7) and LiRbB(4)O(7), are newly developed non-linear optical crystals containing two kinds of anionic groups, namely (B(3)O(8))(7-) and (B(5)O(10))(5-). The (B(3)O(8))(7-) groups form infinite spiral chains parallel to the [100] direction, which are interconnected by sharing O atoms with (B(5)O(10))(5-) groups.

Journal Article↗
PubMed2003

Borate in mummification salts and bones from Pharaonic Egypt.

Mummification processes in Pharaonic Egypt were successful using sodium salts. Quite frequently sodium concentrations in mummified bones ranged from 300 to 4000 micromol/g. In the search for an effective inorganic conservation compound our choice fell on boric acid. The possible presence of borate in mummification salts used in Pharaonic Egypt was of special interest both historically and biochemically. In two salt samples, one from the embalming material of Tutankhamen (18th dynasty, 1336-1327 BC) and the second from Deir el-Bahari (25th dynasty, 700-600 BC) borate was found, amounting to 2.1+/-0.2 and 3.9+/-0.1 micromol/g, respectively. In five of the examined bone fragments from the Junker excavation at Giza (Old Kingdom) similar borate concentrations i.e., 1.2 micromol borate/g bone were seen. It must be emphasized that the usual borate content of contemporary autopsy is far below the detection limit. The elevated borate content in both mummification salt and ancient bone samples support the suggestion that borate-containing salt had been used. There is a striking correlation of both borate concentration and alkaline phosphatase activity. When both sodium salts and borate were essentially absent no activity at all was detectable. With increasing borate concentrations the enzyme activity rises significantly. Attributable to the distinct biochemistry of the tetrahydroxyborate anion it was of interest whether or not borate may stabilize alkaline phosphatase, an important and richly abundant bone enzyme. This enzyme was chosen, as it is known to survive more than 4000 years of mummification. In the presence of borate oligomeric species of this zinc-magnesium-glycoprotein at 400,000 Da became detectable. Attributable to this borate-dependent stabilization of the enzyme molecule a significant temperature resistant increase of the enzymic activity was measured in the presence of up to 2.5 mM borate.

Alkaline Phosphatase↗
PubMed1976

The interaction of borate and sulfite with pyridine nucleotides.

The kinetics and equilibria of the borate interaction at ribose with NAD+ and NMN+ have been measured using as a chromophoric probe the perturbation effect borate has on the addition of sulfite to the 4 position of the nicotinamide ring. NAD+ and NMN+ have more favorable borate association constants than do their corresponding sulfite addition complexes. The rate of interaction of the ribose moiety with borate at low borate buffer concentration is dependent on the concentration of both borate and boric acid. At high borate concentration the rate becomes independent of borate concentration, indicating the existence of a two-step process for the interaction of NAD-sulfite with borate with a change of rate-determining step from the interaction of the ribose hydroxyl group with borate at low borate to an elimination of sulfite at high borate concentration. A linear free energy relationship with a slope of 0.94 describes an increased reactivity of the nucleotide for sulfite as the affinity of the nucleotide for sulfite increases.

Binding Sites↗
PubMed2003

Esterification of borate with NAD+ and NADH as studied by electrospray ionization mass spectrometry and 11B NMR spectroscopy.

This paper describes for the first time the direct measurement of boric acid (B(OH)(3)) and borate (B(OH)(4) (-)) adduction to NAD(+) and NADH by electrospray ionization mass spectrometry (ESI-MS) and (11)B NMR spectroscopy. The analysis demonstrates that borate binds to both cis-2,3-ribose diols on NAD(+) forming borate monoesters (1 : 1 addition), borate diesters (1 : 2 addition) and diborate esters (2 : 1 addition), whereas, only borate monoesters were formed with NADH. MS in the negative ion mode showed borate was bound to a cis-2,3-ribose diol and not to the hydroxyl groups on the phosphate backbone of NAD(+), and MS/MS showed that the 1 : 1 addition monoester contained borate bound to the adenosine ribose. Boron shifts of borate monoesters and diesters with NAD(+) were observed at 7.80 and 12.56 ppm at pH 7.0 to 9.0. The esterifications of borate with NAD(+) and NADH were pH dependent with maximum formation occurring under alkaline conditions with significant formation occurring at pH 7.0. Using ESI-MS, the limit of detection was 50 micro M for NAD(+) and boric acid (1 : 1) to detect NAD(+)-borate monoester at pH 7.0. These results suggest esterification of borate with nicotinamide nucleotides could be of biological significance.

Borates↗
PubMed1976

Antifreeze glycoproteins from Antarctic fish. Inactivation by borate.

Antifreeze glycoprotein, which has previously been shown to be inactive in the presence of borate, migrates electrophoretically as the borate complex, presumably through formation of borate complexes with hydroxyl groups on the sugar side chains. Antifreeze glycoprotein (5 mg/ml) has been found to be completely active in the presence of 0.1 M borate at pH 7, but inactive at pH 9. A titration curve of pH versus the antifreeze activity of glycoprotein (5 mg/ml) in 0.1 M borate showed a progressive decrease in antifreeze activity as the pH was increased. Concomitant with decreases in activity were increases in binding of borate. At pH 9.0, nearly 2 mol of borate were complexed per glycotripeptide. Ultracentrifuge analyses showed similar molecular weights and laser quasi-elastic light scattering showed similar diffusions at pH 7.0 and 9.0 in borate and in the absence of borate. The binding of borate, rather than a change in conformation, is thus directly related to the loss of antifreeze activity. Alkaline borate also decreased hemagglutinating activity of Osage orange lectin and decreased the inhibition of the activity by the antifreeze glycoproteins.

Aldehydes↗
PubMed1991

Borate interference in surface-enhanced Raman spectroscopy of amines.

Interference from borate is observed in surface-enhanced Raman (SER) spectra of lysine and propylamine obtained with borohydride-reduced silver colloids. Borate bands are also observed in the spectra of other basic analytes, as well as when certain variations are made in the silver colloid preparation. The relative intensities of the analyte and borate bands depend on the pH of the colloid, the extent of oxidation of the colloid surface, and the relative adsorptivities of the analyte and borate. Benzylamine adsorbs more readily than propylamine and also competes more effectively with borate for adsorption sites. On the other hand, borate virtually excludes lysine from the surface when the solution pH is greater than or equal to 8. The formation of silver oxide in basified colloids may facilitate borate adsorption. For some basic analytes, eliminating the adsorption of borate ion and the resulting spectral interference may require using alternative SERS substrates.

Amines↗
PubMed2002

Potential binding of borate ions to mono- and oligonucleotides: a capillary electrophoresis investigation.

The potential binding of borate to oligonucleotides and DNA fragments is here investigated. In case of free nucleotides, such as AMP, there appears to be a weak binding, although no free versus complexed species could ever be separated under any experimental condition. The binding was suggested by the strong peak asymmetry and by the fact that, at progressively lower borate molarities in the background electrolyte, the peak shape suddenly switched from fronting to tailing. This indicated, as also confirmed by theoretical simulations, that the AMP-borate complex was the slow, not the fast moving species. On the contrary, in the case of free adenosine, strong binding ensued, since in Tris-acetate buffer this compound was only eluted with the electroendoosmotic flux, being neutral, whereas in Tris-borate it had a much higher mobility, comparable to, although lower than, that of AMP. When running oligonucleotides, at standard borate molarities (ca. 45 mM), and under strict iso-ionic strength conditions, no binding to borate could be demonstrated, since the free mobility of a 24-mer DNA was identical in TA and TB buffers. However, at very high borate molarities (200 mM) and high pH values (pH 8.92), some binding to oligonucleotides could occur, since in these latter conditions the mobility of a 24-mer was seen to be ca. 20% lower than at pH 7.69, a pH value that should discourage any complex formation.

Borates↗
PubMed1999

Low-level calibration study for a new ion chromatographic column to determine borate in deionized water.

In the semiconductor industry, there is interest in determining borate at sub-ppb levels in ultrapure water, since borate is an early breakthrough ion from ion-exchange resin beds. Although dissolved silica is the most common species currently used to monitor the breakdown of the deionization systems, it is thought that borate probably breaks through earlier than silicate. To be of use as an early-warning indicator, borate must be determined at ppt levels. This paper discusses benchtop results with several new column products designed to deliver low-ppt detection limits for boron as borate. The system uses a prototype borate-specific concentrator column that is coupled to an ion-exclusion separator and suppressed-conductivity detection. The acidic eluent, containing mannitol, quantitatively elutes the borate from the concentrator. The analytical separation is performed using a specially designed ion-exclusion column. Data presented are from two multilevel calibration studies. Included is a discussion of detection-limit calculations and recommended formats for reporting results.

Benchmarking↗
PubMed1976

Borate inhibition of yeast alcohol dehydrogenase.

Yeast alcohol dehydrogenase is inhibited competitively by borate with respect to NAD+. An unusual mechanism of competitive inhibition prevails: the competition for the substrate NAD+ by borate and enzyme. The following evidence supports this conclusion. (1) Much greater inhibition is observed with respect to NAD+ as compared with NADH as substrates. (2) Borate decreases the equilibrium constant of the overall reaction in the direction of ethanol oxidation, therefore, borate enters directly into the overall reaction rather than merely decreases the effectiveness of the catalyst. (3) The Ki values for unrelated enzyme reactions are identical for NAD+. (4) Stopped-flow experiments show burst kinetics only when NAD+ and borate are not premixed. (5) The Ki value is identical with the inverse of the borate-NAD+ complexation constant. (6) The pH dependence of the inhibitor demonstrates that only the B(OH)4-species is inhibiting. These results are consistent with the preferable binding of borate to NAD+ as compared with NADH. These two binding constants were found to be equal to 2000 +/- 60 and 130 +/- 8 M-1, respectively. In contrast to the liver enzyme, the yeast enzyme does not show pre-steady-state burst reactions in the reduction of NAD+. This would indicate that the interconversion of ternary complexes is at least partially rate limiting for the yeast enzyme.

Alcohol Oxidoreductases↗