Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BORATES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 271 records · Page 15Linked to original sources
PubMed2000

Comparison of sodium tetraethylborate and sodium tetra(n-propyl)borate as derivatization reagent for the speciation of organotin and organolead compounds in water samples.

The influence of pH on the propylation with sodium tetra(n-propyl)borate of butyl- and phenyltins as well as for trimethyl- and triethyllead was investigated. Ethylation and propylation with tetraalkylborates were compared with regard to derivatization yields and figures of merit for organotin compounds in real water samples. Similar results for limit of detection (3-12 ng/L as tin), derivatization yield (40-100%) and relative standard deviation of the method (3-10%) were achieved for derivatization with the two tetraalkylborates. Propylation is thus the preferred method for the simultaneous determination of environmentally relevant organotin and organolead compounds. The handling of the hygroscopic and air sensitive reagents NaBEt4 and NaBPr4 was simplified by dissolving them in tetrahydrofurane. The reagent solutions in tetrahydrofurane can be stored for at least one month at 4 degrees C in the dark without observing any decrease in the derivatization efficiency.

Journal Article↗
PubMed1996

An optical spectroscopic study of borate glasses containing uranium ions.

An optical spectroscopic investigation has been performed on some borate glasses containing 1mol % UF(4), UO(2) and UO(3). The optical data confirm the presence of uranium ions in valence stages of +6, +5 and +4. The influence of the composition of the glass matrix and of the gamma-irradiation on the redox equilibrium of uranium ions was discussed.

Journal Article↗
PubMed2004

2-aminoethoxydiphenyl borate inhibits agonist-induced Ca2+ signals by blocking inositol trisphosphate formation in acutely dissociated mouse pancreatic acinar cells.

Evidence suggests that 2-aminoethoxydiphenyl borate (2-APB) modulates intracellular Ca(2+) signals in a complex manner. 2-APB inhibits or potentiates intracellular Ca(2+) signals in different cell types, perhaps through different mechanisms. Here, we report a novel mechanism underlying 2-APB-induced inhibition of agonist-activated Ca(2+) oscillations in mouse pancreatic acinar cells, using patch-clamp and biochemical techniques. Pre-treatment of the cells with 100 microM 2-APB completely abolished ACh- but not inositol trisphosphate (InsP(3))-induced Ca(2+) oscillations, suggesting that the mechanism of inhibition occurs between cytoplasmic receptors and InsP(3) receptor activation. In addition, 100 microM 2-APB significantly inhibited ACh-induced phospholipase C (PLC) activation. These findings indicate that, in mouse pancreatic acinar cells, in addition to modulating InsP(3) receptors and blocking the store-operated Ca(2+) pathway, high concentrations of 2-APB also inhibit agonist-induced Ca(2+) signals by reducing InsP(3) formation.

Acetylcholine↗
PubMed1991

Exploring borate-activated electron-rich glyoxals as the arginine-reactivity probes. The reactivities of functionally critical arginines in some representative enzymes.

4-Substituted styrylglyoxals have been synthesized and found to benefit from borate catalysis to serve as highly reactive arginine modifiers. A study of the mechanism in arginine modification has affirmed: (i) the role of electronic effects in modulating the arginine reactivity in alpha-dicarbonyls, (ii) the intermediacy in the reaction of a reversible arginine-alpha-dicarbonyl complex and (iii) the identity of the nucleophilic attack at ketone as the rate determining step in the arginine reaction with arylglyoxals. 4-Methoxystyrylglyoxal and 4-(N,N-dimethylamino)phenylglyoxal were used as the probes in analyzing some representative enzymes for the reactivities of their susceptible arginyls. The susceptible arginyls in lactate and malate dehydrogenases were thus found to be appreciably reactive while those in carboxypeptidase-A and pyruvate kinase were only moderately reactive.

Animals↗
PubMed1995

Double rotation and magic-angle spinning nuclear magnetic resonance study of 27Al: reexamination of the aluminium borate 9Al2O3.2B2O3.

27Al nuclear magnetic resonance spectra of polycrystalline aluminium borate 9Al2O3.2B2O3 have been measured in double rotation at 11.7 and 7.0 T and high-speed magic-angle spinning at 7.0, 9.4, 11.7, 14.1 and 17.6 T. Spinning sidebands from the satellite transitions were observed at 7.0 and 14.1 T. Each of the four structural aluminium sites [Al(IV), Al(V)(1), Al(V)(2) and Al(VI)] are observed, characterised and assigned in the spectra. The obtained parameter set gives a fully consistent interpretation in agreement with the crystal structure of the compound.

Aluminum Compounds↗
PubMed2005

2-Aminoethoxydiphenyl borate perturbs hormone-sensitive calcium stores and blocks store-operated calcium influx pathways independent of cytoskeletal disruption in human A549 lung cancer cells.

Recent studies have identified novel actions for 2-aminoethoxydiphenyl borate (2-APB) in triggering calcium release and enhancing calcium influx induced by the depletion of intracellular calcium stores. In this study, we have examined the effects of 2-APB on the human lung adenocarcinoma A549 cell line, which we have previously shown displays a unique calcium influx response, when ER calcium stores are depleted by thapsigargin (TG) treatment. Here, we show that low concentrations of 2-APB failed to induce the rapid augmentation of TG-activated calcium influx previously reported for other cell types. We observed that store-operated calcium (SOC) channels in the A549 cell line exhibited short-term sensitivity to low doses of 2-APB, perhaps reflecting a delayed augmentation of SOC channel activity or the recruitment of 2-APB-insensitive SOC channels. In both intact and permeabilized cells, 2-APB effectively discharged a subset of A549 calcium pools corresponding to the hormone-sensitive intracellular calcium stores. The 2-APB-induced calcium release produced a long-lasting perturbation of the adenosine triphosphate (ATP)-releasable calcium pools, effectively uncoupling ATP-activated calcium release even, when stores are replenished with calcium. In contrast to previous reports, we found that disruption of either the actin or microtubule-based cytoskeleton failed to block the 2-APB-induced effects on calcium signaling in A549 cells. Our study describes novel cytoskeletal-independent effects of 2-APB on Ca2+-signaling pathways, revealing differentially sensitive Ca2+-influx pathways and long-term perturbation of hormone-sensitive Ca2+ stores.

Actins↗
PubMed2006

2-Aminoethoxydiphenyl borate inhibits KCl-induced vascular smooth muscle contraction.

K(+)-depolarization (KCl)-activated Ca(2+) entry permitting sustained force-maintenance in tonic vascular smooth muscle has long been attributed solely to activation of L-type voltage-operated Ca(2+) channels (VOCs). We used the transient receptor potential channel (TRP) blocker, 2-aminoethoxydiphenyl borate (2-APB), to test the hypothesis that KCl activates additional Ca(2+) entry pathways. 2-APB alone caused a transient weak increase in force, a sustained weak increase in basal [Ca(2+)](i) and myosin light chain phosphorylation, and inhibition of KCl-induced force, [Ca(2+)](i) and myosin light chain phosphorylation. 2-APB did not appear to block VOCs, because 2-APB did not inhibit 30 nM Bay k 8644-induced increases in [Ca(2+)](i). Moreover, although 1 microM nifedipine abolished the increase in [Ca(2+)](i) produced by alpha-adrenergic receptor activation, 2-APB produced an additional reduction in [Ca(2+)](i) below the basal level. These data support the conclusion that membrane depolarization activates 2-APB-sensitive TRPs in addition to VOCs to permit strong force-maintenance in tonic vascular smooth muscle.

Animals↗
PubMed2005

2-Aminoethoxydiphenyl borate (2-APB) stimulates a conformationally coupled calcium release pathway in the NG115-401L neuronal cell line.

We report in this study a 2-aminoethoxydiphenyl borate (2-APB) activated Ca2+ pathway in NG115-401L (401L) neuronal cells bearing resemblance to hormonal and ryanodine receptor activated pathways. We observed that 2-APB, in contrast to much earlier work, did not inhibit store operated Ca2+ channel (SOC) function, but rather induced potent Ca2+ discharge responses that robustly activated SOC-mediated Ca2+ influx. Further, these studies intriguingly revealed that the 2-APB-induced Ca2+ release pathway likely couples conformationally to targets in the plasma membrane, as membrane permeabilization or actin perturbation abolished the ability of the compound to stimulate Ca2+ signals. These findings suggest that conformationally sensitive complexes form between endoplasmic reticulum and plasma membrane components that not only regulate Ca2+ influx, previously proposed as the conformational coupling hypothesis, but are also required to promote Ca2+ release from intracellular stores. These observations further characterize the 401L neuronal cell line as having unique characteristics that may prove useful in gaining insight into the nature of the coupling mechanism linking Ca2+ release to Ca2+ influx.

Animals↗
PubMed2005

Medium-range order in cesium borate glasses probed by double-resonance NMR.

Rotational-echo double-resonance NMR is used to probe the proximity of Cs+ network modifiers to network-forming boron in binary cesium borate glasses. Low- and high-alkali glasses show distinctly different dephasing curves, which indicate preferential association of Cs+ with four-co-ordinate boron ([4]degrees )B) at low-alkali contents only. Different [4]B sites within a given glass appear to be subject to the same 133Cs dipolar field, thus placing constraints on the possible assignments of multiple tetrahedral boron peaks to different types of medium-range order and guiding future structural modeling studies.

Journal Article↗
PubMed2003

2-Aminoethoxydiphenyl borate (2-APB) antagonises inositol 1,4,5-trisphosphate-induced calcium release, inhibits calcium pumps and has a use-dependent and slowly reversible action on store-operated calcium entry channels.

The action of 2-aminoethoxydiphenyl borate (2-APB) on Ca(2+) signalling in HeLa cells and cardiac myocytes was investigated. Consistent with other studies, we found that superfusion of cells with 2-APB rapidly inhibited inositol 1,4,5-trisphosphate (InsP(3))-mediated Ca(2+) release and store-operated Ca(2+) entry (SOC). In addition to abrogating hormone-evoked Ca(2+) responses, 2-APB could antagonise Ca(2+) signals evoked by a membrane permeant InsP(3) ester. 2-APB also slowed the recovery of intracellular Ca(2+) signals consistent with an effect on Ca(2+) ATPases. The inhibitory action of 2-APB on InsP(3) receptors (InsP(3)Rs), SOC channels and Ca(2+) pumps persisted for several minutes after washout of the compound. Application of 2-APB to unstimulated cells had no effect on subsequent Ca(2+) responses suggesting that it has a use-dependent action. Mitochondria in cells treated with 2-APB showed a rapid and slowly reversible swelling. 2-APB did not cause the mitochondria to depolarise, but it reduced the extent of mitochondrial calcium uptake. Although 2-APB has been demonstrated not to affect voltage-operated Ca(2+) channels or ryanodine receptors, we found that it gave a concentration-dependent long-lasting inhibition of Ca(2+) signalling in electrically-stimulated cardiac myocytes, where InsP(3)Rs and SOC channels do not play a significant role. Our data suggest that 2-APB has multiple cellular targets, a use-dependent action, is difficult to reverse and may affect Ca(2+) signalling in cell types where InsP(3) and SOC are not active.

Boron Compounds↗
PubMed2002

2-Aminoethoxydiphenyl borate inhibits inositol 1,4,5-trisphosphate receptor function, ubiquitination and downregulation, but acts with variable characteristics in different cell types.

2-Aminoethoxydiphenyl borate (2-APB) is a putative, membrane-permeable inhibitor of inositol 1,4,5-trisphosphate (InsP(3)) receptors, but it is the case that little is known about its action at the InsP(3) receptor level. Thus, we examined the effects of 2-APB on InsP(3) receptor-mediated effects in a range of cell types expressing different complements of InsP(3) receptor types. In experiments with permeabilized cells we found that 2-APB could inhibit InsP(3)-induced release of stored Ca(2+), but also that it released Ca(2+), and that the prevalence of these two effects varied between different cell types and did not correlate with the expression of a particular receptor type. These effects of 2-APB reflected an interaction distal to the ligand binding site of InsP(3) receptors, since InsP(3) binding was unaffected by 2-APB. In intact cells, we found only inhibitory effects of 2-APB on Ca(2+) mobilization, and that variation between cell types in the characteristics of this inhibition appeared to be due to differential entry of 2-APB. 2-APB also inhibited InsP(3) receptor ubiquitination and proteasomal degradation, which again was cell type dependent. In total, these data reveal a remarkable degree of variation between cell types in the effects of 2-APB, showing that its usefulness as a specific and universal inhibitor of InsP(3) receptors is limited. However, the ability of 2-APB to inhibit InsP(3) receptor ubiquitination and degradation indicates that 2-APB may block InsP(3)-induced conformational changes in the receptor, resulting in perturbation of multiple regulatory events.

Animals↗
PubMed2002

2-Aminoethoxydiphenyl borate inhibits phototransduction and blocks voltage-gated potassium channels in Limulus ventral photoreceptors.

2-Aminoethoxydiphenyl borate (2-APB) is a membrane-permeable modulator that inhibits the activation of inositol (1,4,5) trisphosphate (InsP(3)) receptors, store operated channels (SOCs) and TRP channels in cells that utilize the phosphoinositide cascade for cellular signaling. In Limulus ventral photoreceptors, light-induced calcium release via the phosphoinositide cascade is thought to activate the photocurrent. Injection of either exogenous InsP(3) or calcium ions can therefore mimic excitation by light. One hundred micromolar 2-APB reversibly inhibited the photocurrent of ventral photoreceptors in a concentration-dependent manner, acting on at least two processes thought to mediate the visual cascade. 2-APB reversibly inhibited both light and InsP(3)-induced calcium release, consistent with its role as an inhibitor of the InsP(3) receptor. In addition, 2-APB reversibly inhibited the activation of depolarizing current flow through the plasma membrane caused by pulsed pressure injection of calcium ions into the light-sensitive lobe of the photoreceptor. We also found that 100 micro M 2-APB reversibly inhibited both transient and sustained voltage-activated potassium current during depolarizing steps. 2-APB has previously been shown to block phototransduction in Drosophila photoreceptors. The lack of specificity of the action of 2-APB in Limulus indicates that this blockade need not necessarily arise from inhibition of InsP(3)-induced calcium release.

Animals↗
PubMed1999

Generation and biomimetic chemistry of tungsten-dithiolene complexes containing the hydrotris(3,5-dimethylpyrazol-1-yl)borate ligand.

Reactions of bis(thio)-W(VI) complexes, LWS2X (L = hydrotris (3,5-dimethylpyrazol-1-yl)borate, X = monoanion), with alkynes produce dithiolene complexes, LWX(dithiolene). The synthesis and characterization of orange LW(OPh){S2C2(CO2Me)2} (1) and burgundyred LW(SePh) {S2C2(Ph)(2-quinoxalinyl)} (2) and the X-ray crystal structure of 1.0.5CH2Cl2, are described in detail. Crystals of 1.0.5CH2Cl2 are orthorhombic, space group Pbcn, with a = 29.826(6), b = 13.291(4), c = 16.078(4) A, V = 6373(5) A3, and Z = 8. The six-coordinate, distorted-octahedral complex features a tridentate L ligand, a monodentate phenoxide ligand, and a bidentate dithiolene ligand. The short W-S bonds (2.267(4) and 2.279(4) A) and the parameters associated with the phenoxide ligand (W-O = 1.850(8) A, W-O-C = 146(1) degree), point to a considerable degree of W-ligand multiple bonding in the [W(OPh)(dithiolene)]+ unit. For 2, W-Se and average W-S distances of 2.49(2) A and 2.30(2) A, respectively, have been obtained from EXAFS studies. The formation of yellow 3,3'-dithiobis[2-(phenyl)thieno[2,3-b]quinoxaline] (3) upon oxidation of 2 supports the likely generation of urothione upon oxidative degradation of molybdopterin-containing tungsten enzymes from hyperthermophilic organisms.

Boric Acids↗
PubMed2005

Desorption/ionization on porous silicon mass spectrometry studies on pentose-borate complexes.

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) was used to investigate the binding affinities between aldopentose isomers and boron. Boron has been recognized for its importance in pentose synthesis and stabilization in prebiotic conditions. Boron may also account for the fact that ribose, among other aldopentoses, is the favored building block in RNA synthesis. This research started with the detection of aldopentoses in the positive mode through cationization and the aldopentose-borate complexes in the negative mode. Then two competition schemes, one using a pentose structure analogue and the other using 13C-labeled ribose, were designed to compare the relative binding affinities of four aldopentoses (xylose, lyxose, arabinose, and ribose) to boron. Both approaches determined the binding preference to be ribose > lyxose > arabinose > xylose. This work illustrates the potential of DIOS-MS in the analyses of nonvolatile, small molecules in delicate chemical equilibria. Without externally introduced matrices, background signals are not a limiting factor. Furthermore, the possible dramatic change of pH associated with the matrix introduction, which may disturb the equilibria of interest, is avoided.

Boron↗
PubMed2006

Wide electrochemical window at the interface between water and a hydrophobic room-temperature ionic liquid of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.

Ionic liquids composed of a hydrophobic anion, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB-), and various aromatic and aliphatic ammonium have been prepared. TFPB salts of N-octadecylisoquinolinium (C18Iq+) and trioctylmethylammonium (TOMA+) show low melting points of 31 and 36 degrees C, respectively, whereas TFPB-based ionic liquids of 1-alkyl-3-methylimidazolium with the alkyl chain length of 5-12 show melting points lower than 90 degrees C. The [C(18)Iq][TFPB]|water (W) and [TOMA][TFPB]|W interfaces have the polarized potential window (ppw) of 0.8 V at 56 degrees C, which is twice as wide as the ppw at the interface between W and room-temperature ionic liquids of bis(perfluoroalkylsulfonyl)imide so far reported. The extension of the ppw by more than 0.4 V to the positive direction enables voltammetric measurements of the ion transfer of relatively hydrophobic anions such as bis(trifluoromethylsulfonyl)imide and bis(pentafluoroethylsulfonyl)imide and of hydrophilic cations such as tetraethylammonium and acetylcholine ions.

Journal Article↗
PubMed2001

Synthesis and characterization of fluorinated tris(pyrazolyl)borate complexes. Observation of an (eta 5-pyrazole)-K+ interaction in the solid state.

Cyclopentadienyl (Cp) ligands have received considerable attention mainly because of their pi six-electron donation capability. Tris(pyrazolyl)borate ligands (Tp) are often compared with Cp because of their identical charge, number of donated electrons, and similar facial coordinating geometry. Their six-electron donation, however, is formally sigma-type. The X-ray structure of the [TpCF3,CH3CuK(mu 4-CO3)KTpCF3,CH3]2 aggregate, 1, reveals for the first time an unprecedented eta 5-TpCF3,CH3 potassium bonding interaction. 1 crystallizes in the triclinic space group P1 with a = 12.0411(2) A, b = 14.9791(2) A, c = 16.0567(3) A, alpha = 71.301(1) degrees, beta = 69.785(1) degrees, gamma = 66.539(1) degrees, and Z = 2. Both K-F and K-mu 4-CO3(2-) interactions stabilize the aggregate, as suggested by the lack of hexanuclear aggregation and K incorporation in the absence of fluorine groups or when O=CO2(2-) is replaced by CH3-CO2-. In the latter case we have isolated the complex [CuTpCF3,CH3(CH3CO2)], 2, which retains a Cu coordination sphere similar to that encountered in the TpCF3,CH3Cu subset of 1. The mononuclear complex 2 crystallizes in the monoclinic space group P2(1)/c with a = 14.1474(2) A, b = 14.1474(2) A, c = 19.0456(6) A, beta = 99.012(2) degrees, and Z = 4. The novel eta 5-coordination mode revealed in 1 suggests that Tp ligands might function not only as sigma donors but also as Cp-like pi donors. The eta 5-coordination mode might therefore constitute a new potential common denominator of these two important classes of ligands.

Boron Compounds↗
PubMed2002

Synthesis of tris- and tetrakis(pyrazol-1-yl)borate gold(III) complexes. Crystal structures of [Au[kappa(2)-N,N'-BH(Pz)(3)]Cl(2)] (pz = pyrazol-1-yl) and [Au[kappa(2)-N,N'-B(Pz)(4)](kappa(2)-C,N-C(6)H(4)CH(2)NMe(2)-2)]ClO(4).CHCl(3).

Na[BH(pz)(3)] and Na[AuCl(4)].2H(2)O react in water (1:1) to give [Au[kappa(2)-N,N'-BH(pz)(3)]Cl(2)] (1) or, in the presence of NaClO(4) (2:1:1), the cationic complex [Au[kappa(2)-N,N'-BH(pz)(3)](2)]ClO(4) (2). The reactions of Na[B(pz)(4)] with the cyclometalated gold complexes [AuRCl(2)] and NaClO(4) (1:1:1) produce [Au[kappa(2)-N,N'-B(pz)(4)](R)]ClO(4) [R = kappa(2)-C,N-C(6)H(4)CH(2)NMe(2)-2 (3)] or [Au[kappa(2)-N,N'-B(pz)(4)](R)Cl] [R = C(6)H(3)(N=NC(6)H(4)Me-4')-2-Me-5 (4)], respectively, although 4 is better obtained in the absence of NaClO(4). The crystal structures of 1 and 3.CHCl(3) are reported. Both complexes display the gold center in square planar environments, two coordination sites being occupied by the chelating poly(pyrazolyl)borate ligands.

Journal Article↗
PubMed2002

Heterometal cubane-type MFe(3)S(4) clusters (M = Mo, V) trigonally symmetrized with hydrotris(pyrazolyl)borate(1-) and tris(pyrazolyl)methanesulfonate(1-) capping ligands.

A series of heterometal cubane-type clusters containing [VFe(3)S(4)](2+) and [MoFe(3)S(4)](3+,2+) cores has been prepared. Ligand substitution of [(DMF)(3)VFe(3)S(4)Cl(3)](-) affords [(Tpms)VFe(3)S(4)L(3)](2)(-) (L = Cl(-) (8), EtS(-) (9), p-MeC(6)H(4)S(-), p-MeC(6)H(4)O(-)). A new procedure for the preparation of molybdenum single cubanes is introduced by the reaction of recently reported [(Tp)MoS(S(4))](-) with FeCl(2)/NaSEt to afford [(Tp)MoFe(3)S(4)Cl(3)](-) (1, 75% yield). This procedure is more efficient that the existing multistep synthesis of single cubanes, which generally affords clusters of mirror symmetry. Also prepared were [(Tp)MoFe(3)S(4)L(3)](-) (L = EtS(-) (2), p-MeC(6)H(4)S(-)). Reduction of 1 with borohydride gives [(Tp)MoFe(3)S(4)Cl(3)](2-) (5, 67%). Owing to the nature of the heterometal ligand, all clusters have idealized trigonal symmetry, reflected in their (1)H NMR spectra. Trigonal structures are demonstrated by crystallography of (Bu(4)N)[1,2], (Bu(4)N)(2)[5] x MeCN, and (Me(4)N)(2)[8,9]. The availability of 1 and 5 allows the first comparison of structures and (57)Fe isomer shifts of [MoFe(3)S(4)](3+,2+) in a constant ligand environment. Small increases in most bond distances indicate that an antibonding electron is added in the reduction of 1. Collective synthetic and electrochemical results from this and other studies demonstrate the existence of the series of oxidation states [VFe(3)S(4)](3+,2+,1+) and [MoFe(3)S(4)](4+,3+,2+) whose relative stabilities within a given series are strongly ligand dependent. Isomer shifts indicate that the reduction of 1 largely affects the Fe(3) subcluster and are consistent with the formal descriptions [MoFe(3+)(2)Fe(2+)S(4)](3+) (1) and [MoFe(3+)Fe(2+)(2)S(4)](2+) (5). Reaction of 1 with excess Li(2)S in acetonitrile affords the double cubane [[(Tp)MoFe(3)S(4)Cl(2)](2)(mu(2)(-)S)](2)(-), whose sulfide-bridged structure is supported by two sequential reductions separated by 290 mV, in analogy with previously reported double cubanes of higher charge. Trigonally symmetric single cubanes eliminate isomers in the formation of double cubanes and other cluster structures, and may be of considerable value in the preparation of new types of M-Fe-S clusters. (Tpms = tris(pyrazolyl)methanesulfonate(1-); Tp = hydrotris(pyrazolyl)borate(1-).)

Boron Compounds↗