Science.gov

Sample records for boronic acids

  1. Fluorescent sensors based on boronic acids

    NASA Astrophysics Data System (ADS)

    Cooper, Christopher R.; James, Tony D.

    1999-05-01

    Sensor systems have long been needed for detecting the presence in solution of certain chemically or biologically important species. Sensors are used in a wide range of applications from simple litmus paper that shows a single color change in acidic or basic environments to complex biological assays that use enzymes, antibodies and antigens to display binding events. With this work the use of boronic acids in the design and synthesis of sensors for saccharides (diols) will be presented. The fluorescent sensory systems rely on photoinduced electron transfer (PET) to modulate the observed fluorescence. When saccharides form cyclic boronate esters with boronic acids, the Lewis acidity of the boronic acid is enhanced and therefore the Lewis acid-base interaction between the boronic acid and a neighboring amine is strengthened. The strength of this acid-base interaction modulates the PET from the amine (acting as a quencher) to anthracene (acting as a fluorophore). These compounds show increased fluorescence at neutral pH through suppression of the PET from nitrogen to anthracene on saccharide binding. The general strategy for the development of saccharide selective systems will be discussed. The potential of the boronic acid based systems will be illustrated using the development of glucose and glucosamine selective fluorescent sensors as examples.

  2. Boron-containing amino carboxylic acid compounds and uses thereof

    DOEpatents

    Kabalka, George W.; Srivastava, Rajiv R.

    2000-03-14

    Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

  3. Boron containing amino acid compounds and methods for their use

    SciTech Connect

    Glass, J.D.; Coderre, J.A.

    2000-01-25

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  4. Boron containing amino acid compounds and methods for their use

    DOEpatents

    Glass, John D.; Coderre, Jeffrey A.

    2000-01-01

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  5. Solid Phase Synthesis of C-Terminal Boronic Acid Peptides.

    PubMed

    Behnam, Mira A M; Sundermann, Tom R; Klein, Christian D

    2016-05-01

    Peptides and peptidomimetics with a C-terminal boronic acid group have prolific applications in numerous fields of research, but their synthetic accessibility remains problematic. A convenient, high yield synthesis of peptide-boronic acids on a solid support is described here, using commercially available 1-glycerol polystyrene resin. The method is compatible with Fmoc chemistry and offers a versatile approach to aryl and alkyl aminoboronic acids without additional purification steps. PMID:27104613

  6. A Boronic Acid Porphyrin Receptor for Ginsenoside Sensing

    PubMed Central

    Hargrove, Amanda E.; Reyes, Ryan N.; Riddington, Ian; Anslyn, Eric V.; Sessler, Jonathan L.

    2010-01-01

    Ginsenoside detection was pursued through the design of a porphyrin receptor containing two boronic acid units. This receptor was found to undergo different degrees of fluorescence quenching with five ginsenoside guests and an acylated derivative. The trends in the 1:1 binding constants, as well as ESI-HRMS analysis, support a binding mode in which the ginsenoside sugar units are bound to the boronic acid groups while the steroid core and porphyrin ring participate in hydrophobic interactions. PMID:20860384

  7. Detection of boronic acid derivatives in cells using a fluorescent sensor.

    PubMed

    Hattori, Yoshihide; Ishimura, Miki; Ohta, Youichirou; Takenaka, Hiroshi; Watanabe, Tsubasa; Tanaka, Hiroki; Ono, Koji; Kirihata, Mitsunori

    2015-07-01

    The detection of boron-containing compounds requires very expensive facilities and/or tedious sample pretreatments. In an effort to develop a convenient detection method for boronic acid derivatives, boron chelating-ligands were synthesized for use as fluorescent sensors. In this paper, the synthesis and properties of fluorescent sensors for boronic acid derivatives are reported. PMID:26022725

  8. Surface Behavior of Boronic Acid-Terminated Silicones.

    PubMed

    Mansuri, Erum; Zepeda-Velazquez, Laura; Schmidt, Rolf; Brook, Michael A; DeWolf, Christine E

    2015-09-01

    Silicone polymers, with their high flexibility, lie in a monolayer at the air-water interface as they are compressed until a critical pressure is reached, at which point multilayers are formed. Surface pressure measurements demonstrate that, in contrast, silicones that are end-modified with polar groups take up lower surface areas under compression because the polar groups submerge into the water phase. Boronic acids have the ability to undergo coordination with Lewis bases. As part of a program to examine the surface properties of boronic acids, we have prepared boronic acid-modified silicones (SiBAs) and examined them at the air-water interface to better understand if they behave like other end-functional silicones. Monolayers of silicones, aminopropylsilicones, and SiBAs were characterized at the air-water interface as a function of end functionalization and silicone chain length. Brewster angle and atomic force microscopies confirm domain formation and similar film morphologies for both functionalized and non-functionalized silicone chains. There is a critical surface pressure (10 mN m(-1)) independent of chain length that corresponds to a first-order phase transition. Below this transition, the film appears to be a homogeneous monolayer, whose thickness is independent of the chain length. Ellipsometry at the air-water interface indicates that the boronic acid functionality leads to a significant increase of film thickness at low molecular areas that is not seen for non-functionalized silicone chains. What differentiates the boronic acids from simple silicones or other end-functionalized silicones, in particular, is the larger area occupied by the headgroup when under compression compared to other or non-end-functionalized silicones, which suggests an in-plane rather than submerged orientation that may be driven by boronic acid self-complexation. PMID:26263385

  9. Boron

    MedlinePlus

    Boron is a mineral that is found in food and the environment. People take boron supplements as medicine. Boron is used for building ... to affect the way the body handles other minerals such as magnesium and phosphorus. It also seems ...

  10. Boronic acid building blocks: tools for self assembly.

    PubMed

    Nishiyabu, Ryuhei; Kubo, Yuji; James, Tony D; Fossey, John S

    2011-01-28

    Dynamic covalent functionality has been acknowledged as a powerful tool for the construction of organised architectures, the reversible nature thermodynamically facilitates self-control and self-correction. The use of boronic acids complexation with diols and their congeners has already shown great promise in realising and developing reversible boron-containing multicomponent systems with dynamic covalent functionality. The structure-directing potential has lead to the development of a variety of self-organisation involving not only macrocycles, cages and capsules, but also porous covalent organic frameworks and polymers. Structure controls as well as remarkable synthesis are highlighted in this feature article. PMID:21113558

  11. Boronic acid as an efficient anchor group for surface modification of solid polyvinyl alcohol.

    PubMed

    Nishiyabu, Ryuhei; Shimizu, Ai

    2016-07-28

    We report the use of boronic acid as an anchor group for surface modification of solid polyvinyl alcohol (PVA); the surfaces of PVA microparticles, films, and nanofibers were chemically modified with boronic acid-appended fluorescent dyes through boronate esterification using a simple soaking technique in a short time under ambient conditions. PMID:27311634

  12. Respiratory and eye irritation from boron oxide and boric acid dusts

    SciTech Connect

    Garabrant, D.H.; Bernstein, L.; Peters, J.M.; Smith, T.J.

    1984-08-01

    Boron oxide has been shown in animals to irritate the respiratory mucosa and conjuctiva. The present study was undertaken to determine whether exposures to boron oxide and its hydration product, boric acid, cau

  13. Synthesis of boron suboxide from boron and boric acid under mild pressure and temperature conditions

    SciTech Connect

    Jiao, Xiaopeng; Jin, Hua; Ding, Zhanhui; Yang, Bin; Lu, Fengguo; Zhao, Xudong; Liu, Xiaoyang; Peng, Liping

    2011-05-15

    Graphical abstract: Well-crystallized and icosahedral B{sub 6}O crystals were prepared by reacting boron and boric acid at milder reaction conditions (1 GPa and 1300 {sup o}C for 2 h) as compared to previous work.. Research highlights: {yields} Well-crystallized icosahedral B{sub 6}O was synthesized by reacting boric acid and boron. {yields} The synthesis conditions (1 GPa and 1300 {sup o}C for 2 h) are milder in comparison with previous work. {yields} The more practical synthesis method may make B{sub 6}O as a potential substitute for diamond in industry. -- Abstract: Boron suboxide (B{sub 6}O) was synthesized by reacting boron and boric acid (H{sub 3}BO{sub 3}) at pressures between 1 and 10 GPa, and at temperatures between 1300 and 1400 {sup o}C. The B{sub 6}O samples prepared were icosahedral with diameters ranging from 20 to 300 nm. Well-crystallized and icosahedral crystals with an average size of {approx}100 nm can be obtained at milder reaction conditions (1 GPa and 1300 {sup o}C for 2 h) as compared to previous work. The bulk B{sub 6}O sample was stable in air at 600 {sup o}C and then slowly oxidized up to 1000 {sup o}C. The relatively mild synthetic conditions developed in this study provide a more practical synthesis of B{sub 6}O, which may potentially be used as a substitute for diamond in industry as a new superhard material.

  14. Boron

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron is an essential micronutrient element required for plant growth. Boron deficiency is wide-spread in crop plants throughout the world especially in coarse-textured soils in humid areas. Boron toxicity can also occur, especially in arid regions under irrigation. Plants respond directly to the...

  15. A solid-state (11)b NMR and computational study of boron electric field gradient and chemical shift tensors in boronic acids and boronic esters.

    PubMed

    Weiss, Joseph W E; Bryce, David L

    2010-04-22

    The results of a solid-state (11)B NMR study of a series of 10 boronic acids and boronic esters with aromatic substituents are reported. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. Data collected at 21.1 T clearly show the effects of chemical shift anisotropy (CSA), with tensor spans (Omega) on the order of 10-40 ppm. Signal enhancements of up to 2.95 were achieved with a DFS-modified QCPMG pulse sequence. To understand the relationship between the measured tensors and the local structure better, calculations of the (11)B EFG and magnetic shielding tensors for these compounds were conducted. The best agreement was found between experimental results and those obtained from GGA revPBE DFT calculations. A positive correlation was found between Omega and the dihedral angle (phi(CCBO)), which describes the orientation of the boronic acid/ester functional group relative to an aromatic system bound to boron. The small boron CSA is discussed in terms of paramagnetic shielding contributions as well as diamagnetic shielding contributions. Although there is a region of overlap, both Omega and the (11)B quadrupolar coupling constants tend to be larger for boronic acids than for the esters. We conclude that the span is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters, and show that the values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of phi(CCBO), and the electron-donating or withdrawing substituents bound to the aromatic ring. PMID:20337440

  16. Fluorescent boronic acid polymer grafted on silica particles for affinity separation of saccharides.

    PubMed

    Xu, Zhifeng; Uddin, Khan Mohammad Ahsan; Kamra, Tripta; Schnadt, Joachim; Ye, Lei

    2014-02-12

    Boronic acid affinity gels are important for effective separation of biological active cis-diols, and are finding applications both in biotech industry and in biomedical research areas. To increase the efficacy of boronate affinity separation, it is interesting to introduce repeating boronic acid units in flexible polymer chains attached on solid materials. In this work, we synthesize polymer brushes containing boronic acid repeating units on silica gels using surface-initiated atom transfer radical polymerization (ATRP). A fluorescent boronic acid monomer is first prepared from an azide-tagged fluorogenic boronic acid and an alkyne-containing acrylate by Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction (the CuAAC click chemistry). The boronic acid monomer is then grafted to the surface of silica gel modified with an ATRP initiator. The obtained composite material contains boronic acid polymer brushes on surface and shows favorable saccharide binding capability under physiological pH conditions, and displays interesting fluorescence intensity change upon binding fructose and glucose. In addition to saccharide binding, the flexible polymer brushes on silica also enable fast separation of a model glycoprotein based on selective boronate affinity interaction. The synthetic approach and the composite functional material developed in this work should open new opportunities for high efficiency detection, separation, and analysis of not only simple saccharides, but also glycopeptides and large glycoproteins. PMID:24444898

  17. Fluorescent Boronic Acid Polymer Grafted on Silica Particles for Affinity Separation of Saccharides

    PubMed Central

    2014-01-01

    Boronic acid affinity gels are important for effective separation of biological active cis-diols, and are finding applications both in biotech industry and in biomedical research areas. To increase the efficacy of boronate affinity separation, it is interesting to introduce repeating boronic acid units in flexible polymer chains attached on solid materials. In this work, we synthesize polymer brushes containing boronic acid repeating units on silica gels using surface-initiated atom transfer radical polymerization (ATRP). A fluorescent boronic acid monomer is first prepared from an azide-tagged fluorogenic boronic acid and an alkyne-containing acrylate by Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction (the CuAAC click chemistry). The boronic acid monomer is then grafted to the surface of silica gel modified with an ATRP initiator. The obtained composite material contains boronic acid polymer brushes on surface and shows favorable saccharide binding capability under physiological pH conditions, and displays interesting fluorescence intensity change upon binding fructose and glucose. In addition to saccharide binding, the flexible polymer brushes on silica also enable fast separation of a model glycoprotein based on selective boronate affinity interaction. The synthetic approach and the composite functional material developed in this work should open new opportunities for high efficiency detection, separation, and analysis of not only simple saccharides, but also glycopeptides and large glycoproteins. PMID:24444898

  18. Protodeboronation of Heteroaromatic, Vinyl, and Cyclopropyl Boronic Acids: pH-Rate Profiles, Autocatalysis, and Disproportionation.

    PubMed

    Cox, Paul A; Leach, Andrew G; Campbell, Andrew D; Lloyd-Jones, Guy C

    2016-07-27

    pH-rate profiles for aqueous-organic protodeboronation of 18 boronic acids, many widely viewed as unstable, have been studied by NMR and DFT. Rates were pH-dependent, and varied substantially between the boronic acids, with rate maxima that varied over 6 orders of magnitude. A mechanistic model containing five general pathways (k1-k5) has been developed, and together with input of [B]tot, KW, Ka, and KaH, the protodeboronation kinetics can be correlated as a function of pH (1-13) for all 18 species. Cyclopropyl and vinyl boronic acids undergo very slow protodeboronation, as do 3- and 4-pyridyl boronic acids (t0.5 > 1 week, pH 12, 70 °C). In contrast, 2-pyridyl and 5-thiazolyl boronic acids undergo rapid protodeboronation (t0.5 ≈ 25-50 s, pH 7, 70 °C), via fragmentation of zwitterionic intermediates. Lewis acid additives (e.g., Cu, Zn salts) can attenuate (2-pyridyl) or accelerate (5-thiazolyl and 5-pyrazolyl) fragmentation. Two additional processes compete when the boronic acid and the boronate are present in sufficient proportions (pH = pKa ± 1.6): (i) self-/autocatalysis and (ii) sequential disproportionations of boronic acid to borinic acid and borane. PMID:27355973

  19. Proteus mirabilis urease. Partial purification and inhibition by boric acid and boronic acids.

    PubMed

    Breitenbach, J M; Hausinger, R P

    1988-03-15

    Urease was purified 800-fold and partially characterized from Proteus mirabilis, the predominant microorganism associated with urinary stones. Boric acid is a rapid reversible competitive inhibitor of urease. The pH-dependence of inhibition exhibited pKa values of 6.25 and 9.3, where the latter value is probably due to the inherent pKa of boric acid. Three boronic acids also were shown to inhibit urease competitively. PMID:3291857

  20. Boron-11 pure quadrupole resonance investigation of peptide boronic acid inhibitors bound to alpha-lytic protease.

    PubMed

    Ivanov, Dmitri; Bachovchin, William W; Redfield, Alfred G

    2002-02-01

    Pure quadrupole resonance is a potentially useful spectroscopic approach to study the coordination of quadrupolar nuclei in biological systems. We used a field-cycling NMR method to observe boron pure quadrupole resonance of two peptide boronic acid inhibitors bound to alpha-lytic protease. The method is similar to our earlier field-cycling experiment [Ivanov, D., and Redfield, A. R. (1998) Z. Naturforsch. A 53, 269-272] but uses a simple Hartmann-Hahn transfer from proton to (11)B before field cycle and direct (11)B observe after it. Pure quadrupole resonance is sensitive to the boron coordination geometry. For example, trigonal boron in neutral phenylboronic acid, which was used as a model compound, resonates at 1450 kHz, while the resonance of the tetrahedral phenylboronic acid anion appears at approximately 600 kHz. In the complex of the MeOSuc-Ala-Ala-Pro-boroVal inhibitor with the enzyme the quadrupole resonance signal was observed at 600-650 kHz, which indicates tetrahedral boron coordination in the active site. The quadrupole frequency of the MeOSuc-Ala-Ala-Pro-boroPhe enzyme-inhibitor complex, in which a boron-histidine bond is known to be formed, was found to be the same within experimental error as in the MeOSuc-Ala-Ala-Pro-boroVal enzyme-inhibitor adduct, suggesting that the boron coordination geometry in the enzyme-MeOSuc-Ala-Ala-Pro-boroPhe adduct is also close to tetrahedral. PMID:11814352

  1. 10-Boronic acid substituted camptothecin as prodrug of SN-38.

    PubMed

    Wang, Lei; Xie, Shao; Ma, Longjun; Chen, Yi; Lu, Wei

    2016-06-30

    Malignant tumor cells have been found to have high levels of reactive oxygen species such as hydrogen peroxide (H2O2), supporting the hypothesis that a prodrug could be activated by intracellular H2O2 and lead to a potential antitumor therapy. In this study, the 7-ethyl-10-boronic acid camptothecin (B1) was synthesized for the first time as prodrug of SN-38, by linking a cleavable aryl carbon-boron bond to the SN-38. Prodrug B1 selectively activated by H2O2, converted rapidly to the active form SN-38 under favorable oxidative conditions in cancer cells with elevated levels of H2O2. The cell survival assay showed that prodrug B1 was equally or more effective in inhibiting the growth of six different cancer cells, as compared to SN-38. Unexpectedly, prodrug B1 displayed even more potent Topo I inhibitory activity than SN-38, suggesting that it was not only a prodrug of SN-38 but also a typical Topo I inhibitor. Prodrug B1 also demonstrated a significant antitumor activity at 2.0 mg/kg in a xenograft model using human brain star glioblastoma cell lines U87MG. PMID:27060760

  2. Metal-free protodeboronation of electron-rich arene boronic acids and its application to ortho-functionalization of electron-rich arenes using a boronic acid as a blocking group.

    PubMed

    Ahn, Su-Jin; Lee, Chun-Young; Kim, Nak-Kyoon; Cheon, Cheol-Hong

    2014-08-15

    The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided. On the basis of this protodeboronation, a new protocol for the synthesis of ortho-functionalized electron-rich arenes from these boronic acids was developed using the boronic acid moiety as a blocking group in the electrophilic aromatic substitution reaction, followed by the removal of the boronic acid moiety via thermal protodeboronation. Mechanistic studies suggested that this protodeboronation might proceed via the complex formation of a boronic acid with a proton source, followed by the carbon-boron bond fission through σ-bond metathesis, to afford the corresponding arene compound and boric acid. PMID:25052375

  3. Boronic acid-modified magnetic materials for antibody purification.

    PubMed

    Dhadge, Vijaykumar L; Hussain, Abid; Azevedo, Ana M; Aires-Barros, Raquel; Roque, Ana C A

    2014-02-01

    Aminophenyl boronic acids can form reversible covalent ester interactions with cis-diol-containing molecules, serving as a selective tool for binding glycoproteins as antibody molecules that possess oligosaccharides in both the Fv and Fc regions. In this study, amino phenyl boronic acid (APBA) magnetic particles (MPs) were applied for the magnetic separation of antibody molecules. Iron oxide MPs were firstly coated with dextran to avoid non-specific binding and then with 3-glycidyloxypropyl trimethoxysilane to allow further covalent coupling of APBA (APBA_MP). When contacted with pure protein solutions of human IgG (hIgG) and bovine serum albumin (BSA), APBA_MP bound 170 ± 10 mg hIgG g(-1) MP and eluted 160 ± 5 mg hIgG g(-1) MP, while binding only 15 ± 5 mg BSA g(-1) MP. The affinity constant for the interaction between hIgG and APBA_MP was estimated as 4.9 × 10(5) M(-1) (Ka) with a theoretical maximum capacity of 492 mg hIgG adsorbed g(-1) MP (Qmax), whereas control particles bound a negligible amount of hIgG and presented an estimated theoretical maximum capacity of 3.1 mg hIgG adsorbed g(-1) MP (Qmax). APBA_MPs were also tested for antibody purification directly from CHO cell supernatants. The particles were able to bind 98% of IgG loaded and to recover 95% of pure IgG (purity greater than 98%) at extremely mild conditions. PMID:24258155

  4. Boronic acids for sensing and other applications - a mini-review of papers published in 2013.

    PubMed

    Lacina, Karel; Skládal, Petr; James, Tony D

    2014-01-01

    Boronic acids are increasingly utilised in diverse areas of research. Including the interactions of boronic acids with diols and strong Lewis bases as fluoride or cyanide anions, which leads to their utility in various sensing applications. The sensing applications can be homogeneous assays or heterogeneous detection. Detection can be at the interface of the sensing material or within the bulk sample. Furthermore, the key interaction of boronic acids with diols allows utilisation in various areas ranging from biological labelling, protein manipulation and modification, separation and the development of therapeutics. All the above uses and applications are covered by this mini-review of papers published during 2013. PMID:25371705

  5. Exposure assessment of boron in Bandırma boric acid production plant.

    PubMed

    Duydu, Yalçin; Başaran, Nurşen; Bolt, Hermann M

    2012-06-01

    Boric acid and sodium borates have been considered as being "toxic to reproduction and development", following results of animal studies with high doses. Experimentally, a NOAEL of 17.5mg B/kg-bw/day (corresponds to ∼2020 ng boron/g blood) has been identified for the (male) reproductive effects of boron in a multigenerational study of rats, and a NOAEL for the developmental effects in rats was identified at 9.6 mg B/kg-bw/day (corresponds to 1270 ng boron/g blood). These values are being taken as the basis of current EU safety assessments. The present study was conducted to assess the boron exposure under extreme exposure conditions in a boric acid production plant located in Bandırma, Turkey. The mean blood boron concentrations of low and high exposure groups were 72.94 ± 15.43 (48.46-99.91) and 223.89 ± 60.49 (152.82-454.02)ng/g respectively. The mean blood boron concentration of the high exposure group is still ≈ 6 times lower than the highest no effect level of boron in blood with regard to the developmental effects in rats and ≈ 9 times lower than the highest no effect level of boron in blood with regard to the reprotoxic effects in male rats. In this context, boric acid and sodium borates should not be considered as toxic to reproduction for humans in daily life. PMID:22658716

  6. A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

    2015-06-01

    Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka = 3582.88 M-1) and selectivity for fructose over glucose at pH = 7.4. The sensor 1 showed a linear response toward D-fructose in the concentrations ranging from 2.5 × 10-5 to 4 × 10-4 mol L-1 with the detection limit of 1.3 × 10-5 mol L-1.

  7. Boronic Acid-modified DNA that Changes Fluorescent Properties upon Carbohydrate Binding†

    PubMed Central

    Yang, Xiaochuan; Dai, Chaofeng; Molina, Angie Dayan Calderon

    2010-01-01

    A long wavelength boronic acid-modified TTP (NB-TTP) has been synthesized and enzymatically incorporated into DNA. Such DNA shows intrinsic fluorescent changes upon carbohydrate addition. PMID:20126717

  8. An Alkyne Diboration/6π-Electrocyclization Strategy for the Synthesis of Pyridine Boronic Acid Derivatives.

    PubMed

    Mora-Radó, Helena; Bialy, Laurent; Czechtizky, Werngard; Méndez, María; Harrity, Joseph P A

    2016-05-01

    A new and efficient synthesis of pyridine-based heteroaromatic boronic acid derivatives is reported through a novel diboration/6π-electrocyclization strategy. This method delivers a range of functionalized heterocycles from readily available starting materials. PMID:27059895

  9. Boron isotopic fractionation related to boron sorption on humic acid and the structure of surface complexes formed

    NASA Astrophysics Data System (ADS)

    Lemarchand, Emmanuel; Schott, Jacques; Gaillardet, Jérôme

    2005-07-01

    Boron isotopic fractionation during adsorption onto Ca-flocculated Aldrich humic acid (HA) has been investigated experimentally as a function of solution pH at 25°C and I = 0.15 M. Boron aqueous concentration and isotopic composition were determined by Cs 2BO 2+ Positive Thermal Ionization Mass Spectrometry analysis, while the structure of B surface complexes on HA was characterized using 11B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). Significant B sorption on HA was observed at 6 < pH < 12 with a maximum value of Kd, the partition coefficient between adsorbed and aqueous boron, equal to 40 at pH = 9.5-10. Combined 11B MAS NMR analysis and FITEQL modeling of B sorption on HA showed that this element forms tetrahedrally coordinated five- or six-membered ring chelates, most likely 1,2-diol and 1,3-diol complexes at alkaline pH (8 < pH < 11) and dicarboxylic complexes at near neutral conditions (6 < pH < 9). Results of this study demonstrate for the first time that boron sorption on HA induces a strong pH-dependent isotope fractionation—with 11B depleted at the surface of HA—that reaches a maximum at 5 < pH < 9 (α = 0.975, Δ = -25‰) and decreases sharply at pH >9. The measured isotope fractionation cannot be modeled assuming that the isotopic composition of the sorbed borate species is identical to that of B(OH) 4- species in the parent solution. It is shown that the extent of isotopic fractionation depends not only on B aqueous speciation but also on the distribution and structure of the borate surface complexes formed. In agreement with energetic constrains, calculation of the isotope fractionation factors between aqueous boric acid and boron surface complexes suggests that the formation of the strained six-membered ring 1,3-diol complex yields a much higher fractionation (α BL P1-III = 0.954-0.960, Δ = -41/-47‰) than that of the very stable five-membered ring 1,2-diol (α BL P2-III = 0.983, Δ = -18‰). The results of this study open

  10. Real-time Measurements of Amino Acid and Protein Hydroperoxides Using Coumarin Boronic Acid*

    PubMed Central

    Michalski, Radoslaw; Zielonka, Jacek; Gapys, Ewa; Marcinek, Andrzej; Joseph, Joy; Kalyanaraman, Balaraman

    2014-01-01

    Hydroperoxides of amino acid and amino acid residues (tyrosine, cysteine, tryptophan, and histidine) in proteins are formed during oxidative modification induced by reactive oxygen species. Amino acid hydroperoxides are unstable intermediates that can further propagate oxidative damage in proteins. The existing assays (oxidation of ferrous cation and iodometric assays) cannot be used in real-time measurements. In this study, we show that the profluorescent coumarin boronic acid (CBA) probe reacts with amino acid and protein hydroperoxides to form the corresponding fluorescent product, 7-hydroxycoumarin. 7-Hydroxycoumarin formation was catalase-independent. Based on this observation, we have developed a fluorometric, real-time assay that is adapted to a multiwell plate format. This is the first report showing real-time monitoring of amino acid and protein hydroperoxides using the CBA-based assay. This approach was used to detect protein hydroperoxides in cell lysates obtained from macrophages exposed to visible light and photosensitizer (rose bengal). We also measured the rate constants for the reaction between amino acid hydroperoxides (tyrosyl, tryptophan, and histidine hydroperoxides) and CBA, and these values (7–23 m−1 s−1) were significantly higher than that measured for H2O2 (1.5 m−1 s−1). Using the CBA-based competition kinetics approach, the rate constants for amino acid hydroperoxides with ebselen, a glutathione peroxidase mimic, were also determined, and the values were within the range of 1.1–1.5 × 103 m−1 s−1. Both ebselen and boronates may be used as small molecule scavengers of amino acid and protein hydroperoxides. Here we also show formation of tryptophan hydroperoxide from tryptophan exposed to co-generated fluxes of nitric oxide and superoxide. This observation reveals a new mechanism for amino acid and protein hydroperoxide formation in biological systems. PMID:24928516

  11. Resistivity reduction of boron-doped multiwalled carbon nanotubes synthesized from a methanol solution containing boric acid

    NASA Astrophysics Data System (ADS)

    Ishii, Satoshi; Watanabe, Tohru; Ueda, Shinya; Tsuda, Shunsuke; Yamaguchi, Takahide; Takano, Yoshihiko

    2008-05-01

    Boron-doped multiwalled carbon nanotubes (MWNTs) were synthesized using a methanol solution of boric acid as a source material. Accurate measurements of the electrical resistivity of an individual boron-doped MWNT was performed with a four-point contact, which was fabricated using an electron beam lithography technique. The doped boron provides conduction carriers, which reduces the resistivity of the MWNT.

  12. Effects of Boronizing Treatment on Corrosion Resistance of 65Mn Steel in two Acid Mediums

    NASA Astrophysics Data System (ADS)

    Wang, Hongyu; Zhao, Yufeng; Yuan, Xiaoming; Chen, Kangmin; Xu, Ruihua

    To explore the soil workability of rotary blade suitable for large tilling depth (over 20 cm) manufactured through boronizing treatment, this work focuses on the corrosion behavior of 65Mn steel after boronizing treatment in two acid mediums, i.e. the strong acidic medium that hydrochloric solution and the weak acidic that fertilizer-containing soil, and the comparison with existing technology of general rotary blade (lonnealing after overall quenching). The result shows that the corrosion resistance in the two acid mediums of 65Mn steel after boronizing treatment is remarkably improved. After 168 hours' corrosion in the hydrochloric acid solution, the weight loss of boronizing-status sample is only 27.9% of that of lonnealing-status sample. Moreover, there is no obvious weight loss in boronizing-status sample after 168 hours' corrosion in the fertilizer-containing soil, while the weight of lonnealing-status sample is lighter than the original weight after about 150 hours' corrosion. The improvement of the corrosion resistance lies in the significant reduction of the anodization speed in strong acid medium and the effective prevention of phosphorization reaction in weak acidic medium.

  13. 11B NMR spectroscopy of peptide boronic acid inhibitor complexes of alpha-lytic protease. Direct evidence for tetrahedral boron in both boron-histidine and boron-serine adduct complexes.

    PubMed

    Tsilikounas, E; Kettner, C A; Bachovchin, W W

    1993-11-30

    We have previously shown, using 15N and 1H NMR spectroscopy, that MeOSuc-Ala-Ala-Pro-boroPhe and certain other boronic acid inhibitors form boron-histidine adducts with alpha-lytic protease instead of transition-state-like tetrahedral boron-serine adducts as is generally supposed [Bachovchin, W. W., Wong, W. Y. L., Farr-Jones, S., Shenvi, A. B., & Kettner, C. (1988) Biochemistry 27, 7689-7697]. An X-ray crystallographic study of the MeOSuc-Ala-Ala-Pro-boroPhe complex with alpha-lytic protease [Bone, R., Frank, D., Kettner, C. A., & Agard, D. A. (1989) Biochemistry 28, 7600-7609] has confirmed the existence of the boron-histidine bond but has concluded that the boron atom is trigonal rather than tetrahedral. Here we report a 11B NMR study at 160.46 MHz of this histidine adduct complex and of two other complexes known to be serine adducts: alpha-lytic protease with MeOSuc-Ala-Ala-Pro-boroVal and chymotrypsin with MeOSucAla-Ala-Pro-boroPhe. The 11B NMR chemical shifts demonstrate that the boron atom is tetrahedral in both the histidine and serine adduct complexes.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8251483

  14. Geometry of trigonal boron coordination sphere in boronic acids derivatives - a bond-valence vector model approach.

    PubMed

    Czerwińska, Karolina; Madura, Izabela D; Zachara, Janusz

    2016-04-01

    The systematic analysis of the geometry of three-coordinate boron in boronic acid derivatives with a common [CBO2] skeleton is presented. The study is based on the bond-valence vector (BVV) model [Zachara (2007). Inorg. Chem. 46, 9760-9767], a simple tool for the identification and quantitative estimation of both steric and electronic factors causing deformations of the coordination sphere. The empirical bond-valence (BV) parameters in the exponential equation [Brown & Altermatt (1985). Acta Cryst. B41, 244-247] rij and b, for B-O and B-C bonds were determined using data deposited in the Cambridge Structural Database. The values obtained amount to rBO = 1.364 Å, bBO = 0.37 Å, rBC = 1.569 Å, bBC = 0.28 Å, and they were further used in the calculation of BVV lengths. The values of the resultant BVV were less than 0.10 v.u. for 95% of the set comprising 897 [CBO2] fragments. Analysis of the distribution of BVV components allowed for the description of subtle in- and out-of plane deviations from the `ideal' (sp(2)) geometry of boron coordination sphere. The distortions specific for distinct groups of compounds such as boronic acids, cyclic and acyclic esters, benzoxaboroles and hemiesters were revealed. In cyclic esters the direction of strains was found to be controlled by the ring size effect. It was shown that the syn or anti location of substituents on O atoms is decisive for the deformations direction for both acids and acyclic esters. The greatest strains were observed in the case of benzoxaboroles which showed the highest deviation from the zero value of the resultant BVV. The out-of-plane distortions, described by the vz component of the resultant BVV, were ascertained to be useful in the identification of weak secondary interactions on the fourth coordination site of the boron centre. PMID:27048726

  15. Glucose selective surface plasmon resonance-based bis-boronic acid sensor.

    PubMed

    Stephenson-Brown, Alex; Wang, Hui-Chen; Iqbal, Parvez; Preece, Jon A; Long, Yitao; Fossey, John S; James, Tony D; Mendes, Paula M

    2013-12-01

    Saccharides - a versatile class of biologically important molecules - are involved in a variety of physiological and pathological processes, but their detection and quantification is challenging. Herein, surface plasmon resonance and self-assembled monolayers on gold generated from bis-boronic acid bearing a thioctic acid moiety, whose intramolecular distance between the boronic acid moieties is well defined, are shown to detect d-glucose with high selectivity, demonstrating a higher affinity than other saccharides probed, namely d-galactose, d-fructose and d-mannose. PMID:24151633

  16. Relative kinetic reactivity of boronic acid and boronate ion towards Tiron, 2,2'-biphenol, and propylene glycol.

    PubMed

    Watanabe, Eisuke; Miyamoto, Chiaki; Tanaka, Asumi; Iizuka, Kenzo; Iwatsuki, Satoshi; Inamo, Masahiko; Takagi, Hideo D; Ishihara, Koji

    2013-06-21

    Reaction systems of boronic acid (RB(OH2), R = phenyl or 3-fluorophenyl) with diols and no proton ambiguity were elaborately set up, and kinetic measurements were conducted to elucidate the relative reactivities of RB(OH)2 and RB(OH)3(-). In the reactions of phenylboronic and 3-fluorophenylboronic acids with propylene glycol, the reactivity order was: RB(OH)2 > RB(OH)3(-), whereas in the reactions of 3-pyridylboronic acid with Tiron and 2,2'-biphenol, the reactivity of RB(OH)2 was comparable to that of RB(OH)3(-). These results are in contrast to those that have been previously reported, and widely accepted for over thirty years, that concluded that the reactivity of RB(OH)3(-) is several orders of magnitude higher than that of RB(OH)2. The reactivity of Tiron with 3-pyridylboronic acid is affected by the protonation of one of its sulfonate groups. PMID:23625094

  17. Gas Adsorption Properties of Graphene-Oxide-Frameworks and Nanoporous Benzene-Boronic Acid Polymers

    NASA Astrophysics Data System (ADS)

    Burress, Jacob; Simmons, Jason; Ford, Jamie; Yildirim, Taner

    2010-03-01

    There has been a recent resurgence in graphene oxide research as a potential route to large scale graphene synthesis. Recent research has also used dehydration reactions of boronic acids for the formation of covalent organic frameworks (COFs) and other new nanoporous materials. We are trying to synthesize graphene-oxide-frameworks (GOFs) by linking the OH groups on graphene oxide with benzene-boronic acids. Our initial x-ray studies indicate that the benzene-boronic acids are successfully incorporated into graphene-oxide (GO) layers expanding the interlayer spacing up to 12 Ang. We also found that the amorphous phases of bare dehydrated benzene-boronic acid polymers (amorphous borocarbons, ABCs) show quite interesting and unusual hydrogen adsorption behavior. The diffusion of hydrogen into the sample is thermally activated. While there is no adsorption at 30 K, the rate of excess adsorption increases with increasing temperature up to 70 K. We will present detailed high-pressure isotherms of H2/CO2/Methane at different temperatures of these interesting new GOF materials and dehydrated boronic acid polymers.

  18. OsNIP3;1, a rice boric acid channel, regulates boron distribution and is essential for growth under boron-deficient conditions.

    PubMed

    Hanaoka, Hideki; Uraguchi, Shimpei; Takano, Junpei; Tanaka, Mayuki; Fujiwara, Toru

    2014-06-01

    Boron is an essential micronutrient for higher plants. Boron deficiency is an important agricultural issue because it results in loss of yield quality and/or quantity in cereals and other crops. To understand boron transport mechanisms in cereals, we characterized OsNIP3;1, a member of the major intrinsic protein family in rice (Oryza sativa L.), because OsNIP3;1 is the most similar rice gene to the Arabidopsis thaliana boric acid channel genes AtNIP5;1 and AtNIP6;1. Yeast cells expressing OsNIP3;1 imported more boric acid than control cells. GFP-tagged OsNIP3;1 expressed in tobacco BY2 cells was localized to the plasma membrane. The accumulation of OsNIP3;1 transcript increased fivefold in roots within 6 h of the onset of boron starvation, but not in shoots. Promoter-GUS analysis suggested that OsNIP3;1 is expressed mainly in exodermal cells and steles in roots, as well as in cells around the vascular bundles in leaf sheaths and pericycle cells around the xylem in leaf blades. The growth of OsNIP3;1 RNAi plants was impaired under boron limitation. These results indicate that OsNIP3;1 functions as a boric acid channel, and is required for acclimation to boron limitation. Boron distribution among shoot tissues was altered in OsNIP3;1 knockdown plants, especially under boron-deficient conditions. This result demonstrates that OsNIP3;1 regulates boron distribution among shoot tissues, and that the correct boron distribution is crucial for plant growth. PMID:24654769

  19. Boronic Acid Group: A Cumbersome False Negative Case in the Process of Drug Design.

    PubMed

    Katsamakas, Sotirios; Papadopoulos, Anastasios G; Hadjipavlou-Litina, Dimitra

    2016-01-01

    Herein we present, an exhaustive docking analysis considering the case of autotaxin (ATX). HA155, a small molecule inhibitor of ATX, is co-crystallized. In order to further extract conclusions on the nature of the bond formed between the ligands and the amino acid residues of the active site, density functional theory (DFT) calculations were undertaken. However, docking does not provide reproducible results when screening boronic acid derivatives and their binding orientations to protein drug targets. Based on natural bond orbital (NBO) calculations, the formed bond between Ser/Thr residues is characterized more accurately as a polar covalent bond instead of a simple nonpolar covalent one. The presented results are acceptable and could be used in screening as an active negative filter for boron compounds. The hydroxyl groups of amino acids are bonded with the inhibitor's boron atom, converting its hybridization to sp³. PMID:27617984

  20. Boronic Acid-Based Approach for Separation and Immobilization of Glycoproteins and Its Application in Sensing

    PubMed Central

    Wang, Xiaojin; Xia, Ning; Liu, Lin

    2013-01-01

    Glycoproteins influence a broad spectrum of biological processes including cell-cell interaction, host-pathogen interaction, or protection of proteins against proteolytic degradation. The analysis of their glyco-structures and concentration levels are increasingly important in diagnosis and proteomics. Boronic acids can covalently react with cis-diols in the oligosaccharide chains of glycoproteins to form five- or six-membered cyclic esters. Based on this interaction, boronic acid-based ligands and materials have attracted much attention in both chemistry and biology as the recognition motif for enrichment and chemo/biosensing of glycoproteins in recent years. In this work, we reviewed the progress in the separation, immobilization and detection of glycoproteins with boronic acid-functionalized materials and addressed its application in sensing. PMID:24141187

  1. Iterative reactions of transient boronic acids enable sequential C-C bond formation

    NASA Astrophysics Data System (ADS)

    Battilocchio, Claudio; Feist, Florian; Hafner, Andreas; Simon, Meike; Tran, Duc N.; Allwood, Daniel M.; Blakemore, David C.; Ley, Steven V.

    2016-04-01

    The ability to form multiple carbon-carbon bonds in a controlled sequence and thus rapidly build molecular complexity in an iterative fashion is an important goal in modern chemical synthesis. In recent times, transition-metal-catalysed coupling reactions have dominated in the development of C-C bond forming processes. A desire to reduce the reliance on precious metals and a need to obtain products with very low levels of metal impurities has brought a renewed focus on metal-free coupling processes. Here, we report the in situ preparation of reactive allylic and benzylic boronic acids, obtained by reacting flow-generated diazo compounds with boronic acids, and their application in controlled iterative C-C bond forming reactions is described. Thus far we have shown the formation of up to three C-C bonds in a sequence including the final trapping of a reactive boronic acid species with an aldehyde to generate a range of new chemical structures.

  2. Qualitative identification of carboxylic acids, boronic acids, and amines using cruciform fluorophores.

    PubMed

    Schwaebel, Thimon; Lirag, Rio Carlo; Davey, Evan A; Lim, Jaebum; Bunz, Uwe H F; Miljanić, Ognjen Š

    2013-01-01

    Molecular cruciforms are X-shaped systems in which two conjugation axes intersect at a central core. If one axis of these molecules is substituted with electron-donors, and the other with electron-acceptors, cruciforms' HOMO will localize along the electron-rich and LUMO along the electron-poor axis. This spatial isolation of cruciforms' frontier molecular orbitals (FMOs) is essential to their use as sensors, since analyte binding to the cruciform invariably changes its HOMO-LUMO gap and the associated optical properties. Using this principle, Bunz and Miljanić groups developed 1,4-distyryl-2,5-bis(arylethynyl)benzene and benzobisoxazole cruciforms, respectively, which act as fluorescent sensors for metal ions, carboxylic acids, boronic acids, phenols, amines, and anions. The emission colors observed when these cruciform are mixed with analytes are highly sensitive to the details of analyte's structure and - because of cruciforms' charge-separated excited states - to the solvent in which emission is observed. Structurally closely related species can be qualitatively distinguished within several analyte classes: (a) carboxylic acids; (b) boronic acids, and (c) metals. Using a hybrid sensing system composed from benzobisoxazole cruciforms and boronic acid additives, we were also able to discern among structurally similar: (d) small organic and inorganic anions, (e) amines, and (f) phenols. The method used for this qualitative distinction is exceedingly simple. Dilute solutions (typically 10(-6) M) of cruciforms in several off-the-shelf solvents are placed in UV/Vis vials. Then, analytes of interest are added, either directly as solids or in concentrated solution. Fluorescence changes occur virtually instantaneously and can be recorded through standard digital photography using a semi-professional digital camera in a dark room. With minimal graphic manipulation, representative cut-outs of emission color photographs can be arranged into panels which permit quick naked

  3. Ammonolysis of esters of hydroxybenzoic acids on a boron phosphate catalyst

    SciTech Connect

    Suvorov, B.V.; Bukeikhanov, N.R.; Li, L.V.; Zulkasheva, A.Z.

    1987-09-10

    In this investigation boron phosphate catalyst was used for ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids. It was shown that ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids in presence of boron phosphate catalyst at a ratio of 3-7 moles of ammonia per mole of ester in a contact time of 1-5 sec at 380-400/sub 0/ can be used for obtaining o- and p- hydroxybenzonitriles in yields of over 90% of the theoretical.

  4. Hyaluronic acid as a potential boron carrier for BNCT: Preliminary evaluation.

    PubMed

    Zaboronok, A; Yamamoto, T; Nakai, K; Yoshida, F; Uspenskii, S; Selyanin, M; Zelenetskii, A; Matsumura, Akira

    2015-12-01

    Hyaluronic acid (HA), a nonimmunogenic, biocompatible polymer found in different biological tissues, has the potential to attach to CD44 receptors on the surface of certain cancer cells, where the receptor is overexpressed compared with normal cells. Boron-hyaluronic acid (BHA) was tested for its feasibility as a potential agent for BNCT. BHA with low-viscosity 30 kDa HA could be administered by intravenous injection. The compound showed a certain degree of cytotoxicity and accumulation in C6 rat glioma cells in vitro. Instability of the chelate bonds between boron and HA and/or insufficient specificity of CD44 receptors on C6 cells to BHA could account for the insufficient in vitro accumulation. To ensure the future eligibility of BHA for BNCT experiments, using alternative tumor cell lines and chemically securing the chelate bonds or synthesizing BHA with boron covalently attached to HA might be required. PMID:26302663

  5. Boron

    SciTech Connect

    Cozen, L.F. )

    1991-05-01

    This paper reports that borate minerals and refined borates are used extensively for the manufacture of vitreous materials such as insulation and textile fiberglasses, borosilicate glass, and porcelain enamels and frits. In North America, these applications are estimated to account for over 54% of the borate consumption. Other substantial uses are in soaps and detergents, metallurgy, fire retardants, industrial biocides, agriculture, and various miscellaneous applications. Reported domestic borate consumption in 1990 was estimated by the U.S. Bureau of Mines to be 320 000 metric tons B{sub 2}O{sub 3} versus 354 000 metric tons B{sub 2}O{sub 3} in 1989. Consumption is projected to remain essentially static in 1991. Imports were estimated by the Bureau to be 50 000 metric tons B{sub 2}O{sub 3} in 1990. Exports of boric acid and refined borates were approximately 650 000 metric tons of product, a 15 000 metric ton increase from the 1989 level. This increase partially offsets the drop in the 1990 consumption level.

  6. Boronic acid flux synthesis and crystal growth of uranium and neptunium boronates and borates: a low-temperature route to the first neptunium(V) borate.

    PubMed

    Wang, Shuao; Alekseev, Evgeny V; Miller, Hannah M; Depmeier, Wulf; Albrecht-Schmitt, Thomas E

    2010-11-01

    Molten methylboronic acid has been used as a reactive flux to prepare the first neptunium(V) borate, NpO(2)[B(3)O(4)(OH)(2)] (NpBO-1), and the first actinide boronate, UO(2)(CH(3)BO(2))(H(2)O) (UCBO-1). NpBO-1 contains cation-cation interactions between the neptunyl units. In contrast, the presence of the methyl groups in the uranyl boronate leads to a one-dimensional structure. PMID:20919728

  7. Antitumor effects of tyropeptin-boronic acid derivatives: New proteasome inhibitors

    PubMed Central

    Momose, Isao; Abe, Hikaru; Watanabe, Takumi; Ohba, Shun-ichi; Yamazaki, Kanami; Dan, Shingo; Yamori, Takao; Masuda, Tohru; Nomoto, Akio

    2014-01-01

    The proteasome degrades numerous regulatory proteins that are critical for tumor growth. Thus, proteasome inhibitors are promising antitumor agents. New proteasome inhibitors, such as tyropeptins and tyropeptin-boronic acid derivatives, have a potent inhibitory activity. Here we report the antitumor effects of two new tyropeptin-boronic acid derivatives, AS-06 and AS-29. AS-06 and AS-29 significantly suppress the degradation of the proteasome-sensitive fluorescent proteins in HEK293PS cells, and induce the accumulation of ubiquitinated proteins in human multiple myeloma cells. We show that these derivatives also suppress the degradation of the NF-κB inhibitor IκB-α and the nuclear translocation of NF-κB p65 in multiple myeloma cells, resulting in the inhibition of NF-κB activation. Furthermore, we demonstrate that AS-06 and AS-29 induce apoptosis through the caspase-8 and caspase-9 cascades. In a xenograft mouse model, i.v. administration of tyropeptin-boronic acid derivatives inhibits proteasome in tumors and clearly suppresses tumor growth in mice bearing human multiple myeloma. Our results indicate that tyropeptin-boronic acid derivatives could be lead therapeutic agents against human multiple myeloma. PMID:25251038

  8. Hierarchical carbon nanotube assemblies created by sugar-boric or boronic acid interactions.

    PubMed

    Tamesue, Shingo; Numata, Munenori; Kaneko, Kenji; James, Tony D; Shinkai, Seiji

    2008-10-01

    We previously found that polysaccharide "schizophyllan (SPG)" can entrap as-grown and cut single-walled carbon nanotubes (as-SWNTs and c-SWNTs, respectively): we here reported that the c-SWNT-s-SPG (single stranded SPG) composites thus obtained can be aligned regularly using the covalent bond formation between boric acid or boronic acid derivatives and the 4,6-dihydroxyl group of the glucose side-chain unit. PMID:18802596

  9. The boron oxide{endash}boric acid system: Nanoscale mechanical and wear properties

    SciTech Connect

    Ma, X.; Unertl, W.N.; Erdemir, A.

    1999-08-01

    The film that forms spontaneously when boron oxide (B{sub 2}O{sub 3}) is exposed to humid air is a solid lubricant. This film is usually assumed to be boric acid (H{sub 3}BO{sub 3}), the stable bulk phase. We describe the nanometer-scale surface morphology, mechanical properties, and tribological properties of these films and compare them with crystals precipitated from saturated solutions of boric acid. Scanning force microscopy (SFM) and low-load indentation were the primary experimental tools. Mechanical properties and their variation with depth are reported. In all cases, the surfaces were covered with a layer that has different mechanical properties than the underlying bulk. The films formed on boron oxide showed no evidence of crystalline structure. A thin surface layer was rapidly removed, followed by slower wear of the underlying film. The thickness of this initial layer was sensitive to sample preparation conditions, including humidity. Friction on the worn surface was lower than on the as-formed surface in all cases. In contrast, the SFM tip was unable to cause any wear to the surface film on the precipitated crystals. Indentation pop-in features were common for precipitated crystals but did not occur on the films formed on boron oxide. The surface structures were more complex than assumed in models put forth previously to explain the mechanism of lubricity in the boron oxide{endash}boric acid{endash}water system. {copyright} {ital 1999 Materials Research Society.}

  10. Growth of boric acid crystallites on the surface of boron-doped silicon carbide samples

    SciTech Connect

    Vassen, R.; Stoever, D.

    1996-06-01

    White crystallites were visually observed on fractured or polished surfaces of SiC samples (grain sizes below {approx}500 nm) during exposure to air at room temperature for several days. Characterization of the crystallites by scanning electron microscopy, secondary ion mass spectroscopy, and X-ray diffraction identified B(OH){sub 3} crystals with a strong (002) texture. The rate of boric acid formation was determined by a gravimetric experiment. The rate of weight gain increased significantly after an incubation period of 1 week. Nucleation is initially the rate-limiting process. Subsequently small B(OH){sub 3} crystals form on the surface, whose growth rate is determined by grain boundary diffusion of boron to the SiC surface. An estimated grain boundary boron to the SiC surface. An estimated grain boundary diffusion coefficient of boron in SiC was many orders of magnitude higher than extrapolated literature values.

  11. Boron reclamation

    SciTech Connect

    Smith, R.M.

    1980-07-01

    A process to recover high purity /sup 10/B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron.

  12. Facile synthesis of boronic acid-functionalized magnetic carbon nanotubes for highly specific enrichment of glycopeptides

    NASA Astrophysics Data System (ADS)

    Ma, Rongna; Hu, Junjie; Cai, Zongwei; Ju, Huangxian

    2014-02-01

    A stepwise strategy was developed to synthesize boronic acid functionalized magnetic carbon nanotubes (MCNTs) for highly specific enrichment of glycopeptides. The MCNTs were synthesized by a solvothermal reaction of Fe3+ loaded on the acid-treated CNTs and modified with 1-pyrenebutanoic acid N-hydroxysuccinimidyl ester (PASE) to bind aminophenylboronic acid (APBA) via an amide reaction. The introduction of PASE could bridge the MCNT and APBA, suppress the nonspecific adsorption and reduce the steric hindrance among the bound molecules. Due to the excellent structure of the MCNTs, the functionalization of PASE and then APBA on MCNTs was quite simple, specific and effective. The glycopeptides enrichment and separation with a magnetic field could be achieved by their reversible covalent binding with the boronic group of APBA-MCNTs. The exceptionally large specific surface area and the high density of boronic acid groups of APBA-MCNTs resulted in rapid and highly efficient enrichment of glycopeptides, even in the presence of large amounts of interfering nonglycopeptides. The functional MCNTs possessed high selectivity for enrichment of 21 glycopeptides from the digest of horseradish peroxidase demonstrated by MALDI-TOF mass spectrometric analysis showing more glycopeptides detected than the usual 9 glycopeptides with commercially available APBA-agarose. The proposed system showed better specificity for glycopeptides even in the presence of non-glycopeptides with 50 times higher concentration. The boronic acid functionalized MCNTs provide a promising selective enrichment platform for precise glycoproteomic analysis.A stepwise strategy was developed to synthesize boronic acid functionalized magnetic carbon nanotubes (MCNTs) for highly specific enrichment of glycopeptides. The MCNTs were synthesized by a solvothermal reaction of Fe3+ loaded on the acid-treated CNTs and modified with 1-pyrenebutanoic acid N-hydroxysuccinimidyl ester (PASE) to bind aminophenylboronic acid

  13. Kinetic flow-injection analysis of boron using 5-fluorosalicylaldehyde and H-acid.

    PubMed

    Sarenqiqige; Kodani, Takamasa; Kajiwara, Mari; Takehara, Kô; Yoshimura, Kazuhisa

    2014-01-01

    Boric acid reacts with 5-fluorosalicylaldehyde (F-SA) and 8-amino-1-naphthol-3,6-disulfonic acid (HA) to form the boric acid-fluoroazomethine H complex (F-AzB) that is now being used for the flow-injection analysis (FIA) of boric acid. At pH 6.5, the F-AzB complexation proceeded fairly fast, whereas the fluoroazomethine H (F-AzH) formation was slow. Thus, highly sensitive measurement of F-AzB was possible if the reaction time was controlled using the FIA method to decrease the background absorbance of F-AzH at the analytical wavelength. The optimum conditions for the color developing reaction were investigated for single and dual channel systems. The former system was simple, applicable to the determination of boron in reversed osmosis (RO) desalination water with a detection limit (LOD) of 4 μg B dm(-3). For the latter system, the calibration range was 0.005 to 10 mg B dm(-3) with an LOD of 1 μg B dm(-3), which can be applicable to natural water analyses of boron. These methods could analyze 15 - 20 samples in one hour. The results of the boron concentration measurement for water samples from an RO desalination plant, industrial wastewater and river water were in fairly good agreement with those obtained by other methods. PMID:25213816

  14. Nickel-Catalyzed Cross-Coupling of Redox-Active Esters with Boronic Acids.

    PubMed

    Wang, Jie; Qin, Tian; Chen, Tie-Gen; Wimmer, Laurin; Edwards, Jacob T; Cornella, Josep; Vokits, Benjamin; Shaw, Scott A; Baran, Phil S

    2016-08-01

    A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross-coupling between alkyl-carboxylic acids and boronic acids is described. This Ni-catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox-active ester derivatives, specifically N-hydroxy-tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2 ⋅6 H2 O-$9.5 mol(-1) , Et3 N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption. PMID:27380912

  15. Synthesis of substituted benzooxaborinin-1-ols via palladium-catalysed cyclisation of alkenyl- and alkynyl-boronic acids.

    PubMed

    Benhamou, Laure; Walker, Daniel W; Bučar, Dejan-Krešimir; Aliev, Abil E; Sheppard, Tom D

    2016-09-14

    Two new palladium-catalysed reactions have been developed for the synthesis of stable 4-substituted benzooxaborinin-1-ols. A palladium-catalysed cyclisation of ortho-alkenylbenzene boronic acids can be used to access 4-chlorobenzooxaborinin-1-ols via a Wacker-type oxidation and chlorination. Alternatively, ortho-alkynylbenzene boronic acids undergo a palladium-catalysed oxyallylation reaction to provide 4-allylbenzooxaborinin-1-ols. PMID:27506186

  16. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

    PubMed

    Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao

    2008-08-01

    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure. PMID:18585727

  17. A boronic acid chalcone analog of combretastatin A-4 as a potent anti-proliferation agent

    PubMed Central

    Kong, Yali; Wang, Kan; Edler, Michael C.; Hamel, Ernest; Mooberry, Susan L.; Paige, Mikell A.; Brown, Milton L.

    2010-01-01

    Chalcones represent a class of natural products that inhibits tubulin assembly. In this study we designed and synthesized boronic acid analogs of chalcones in an effort to compare biological activities with combretastatin A-4, a potent inhibitor of tubulin polymerization. Systematic evaluation of the positional effects of the carbonyl moiety towards inhibition of tubulin polymerization, cancer cell proliferation and angiogenesis revealed that placement of the carbonyl adjacent to the trimethoxybenzene A-ring resulted in more active compounds than when the carbonyl group was placed adjacent to the C-ring. Our study identified a boronic acid chalcone with inhibition towards 16 human cancer cell lines in the 10–200 nM range, and another three cell lines with GI50-values below 10 nM. Furthermore, this drug has significant anti-angiogenesis effects demonstrated by HUVEC tube formation and aortic ring assay. PMID:20006519

  18. Chemoselective Boron-Catalyzed Nucleophilic Activation of Carboxylic Acids for Mannich-Type Reactions.

    PubMed

    Morita, Yuya; Yamamoto, Tomohiro; Nagai, Hideoki; Shimizu, Yohei; Kanai, Motomu

    2015-06-10

    The carboxyl group (COOH) is an omnipresent functional group in organic molecules, and its direct catalytic activation represents an attractive synthetic method. Herein, we describe the first example of a direct catalytic nucleophilic activation of carboxylic acids with BH3·SMe2, after which the acids are able to act as carbon nucleophiles, i.e. enolates, in Mannich-type reactions. This reaction proceeds with a mild organic base (DBU) and exhibits high levels of functional group tolerance. The boron catalyst is highly chemoselective toward the COOH group, even in the presence of other carbonyl moieties, such as amides, esters, or ketones. Furthermore, this catalytic method can be extended to highly enantioselective Mannich-type reactions by using a (R)-3,3'-I2-BINOL-substituted boron catalyst. PMID:26011419

  19. Fluorination of boronic acids mediated by silver(I) triflate.

    PubMed

    Furuya, Takeru; Ritter, Tobias

    2009-07-01

    A regiospecific Ag-mediated fluorination reaction of aryl- and alkenylboronic acids and esters is reported. The fluorination reaction uses commercially available reagents, does not require the addition of exogenous ligands, and can be performed on a multigram scale. This report discloses the first practical reaction sequence from arylboronic acid to aryl fluorides. PMID:19507870

  20. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids.

    PubMed

    Fu, Ming-Chen; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-07-27

    A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts. PMID:26150397

  1. A multi-stimuli responive, self-assembling, boronic acid dipeptide

    DOE PAGESBeta

    Jones, Brad Howard; Martinez, Alina Marissa; Wheeler, Jill S.; McKenzie, Bonnie B.; Miller, Lance Lee; Wheeler, David R.; Spoerke, Erik David

    2015-08-11

    Modification of the dipeptide of phenylalanine, FF, with a boronic acid (BA) functionality imparts unique aqueous self-assembly behavior that responds to multiple stimuli. Changes in pH and ionic strength are used to trigger hydrogelation via the formation of nanoribbon networks. Thus, we show for the first time that the binding of polyols to the BA functionality can modulate a peptide between its assembled and disassembled states.

  2. Radical C-H alkylation of BODIPY dyes using potassium trifluoroborates or boronic acids.

    PubMed

    Verbelen, Bram; Cunha Dias Rezende, Lucas; Boodts, Stijn; Jacobs, Jeroen; Van Meervelt, Luc; Hofkens, Johan; Dehaen, Wim

    2015-09-01

    A one-step synthetic procedure for the radical CH alkylation of BODIPY dyes has been developed. This new reaction generates alkyl radicals through the oxidation of boronic acids or potassium trifluoroborates and allows the synthesis of mono-, di-, tri-, and tetraalkylated fluorophores in a good to excellent yield for a broad range of organoboron compounds. Using this protocol, multiple bulky alkyl groups can be introduced onto the BODIPY core thus creating solid-state emissive BODIPY dyes. PMID:26215785

  3. Determination of boron in produced water using the carminic acid assay.

    PubMed

    Floquet, Cedric F A; Sieben, Vincent J; MacKay, Bruce A; Mostowfi, Farshid

    2016-04-01

    Using the carminic acid assay, we determined the concentration of boron in oilfield waters. We investigated the effect of high concentrations of salts and dissolved metals on the assay performance. The influence of temperature, development time, reagent concentration, and water volume was studied. Ten produced and flowback water samples of different origins were measured, and the method was successfully validated against ICP-MS measurements. In water-stressed regions, produced water is a potential source of fresh water for irrigation, industrial applications, or consumption. Therefore, boron concentration must be determined and controlled to match the envisaged waste water reuse. Fast, precise, and onsite measurements are needed to minimize errors introduced by sample transportation to laboratories. We found that the optimum conditions for our application were a 5:1 mixing volume ratio (reagent to sample), a 1 g L(-1) carminic acid concentration in 99.99% sulfuric acid, and a 30 min reaction time at ambient temperature (20 °C to 23 °C). Absorption values were best measured at 610 nm and 630 nm and baseline corrected at 865 nm. Under these conditions, the sensitivity of the assay to boron was maximized while its cross-sensitivity to dissolved titanium, iron, barium and zirconium was minimized, alleviating the need for masking agents and extraction methods. PMID:26838405

  4. Removal of boron from aqueous solution using magnetic carbon nanotube improved with tartaric acid

    PubMed Central

    2014-01-01

    Boron removal capacity of multi-walled carbon nanotubes (MWCNTs) modified with tartaric acid was investigated in this study. Modification of MWCNTs with tartaric acid was confirmed by Boehm surface chemistry method and fourier transform infra-red (FT-IR) spectroscopy. Experiments were performed to determine the adsorption isotherm and adsorption thermodynamic parameters of boron adsorption on tartaric acid modified MWCNTs (TA-MWCNTs). The effect of variables including initial pH, dosage of adsorbent, contact time and temperature was investigated. Analysis of data showed that adsorption equilibrium could be better described by Freundlich isotherm and the maximum adsorption capacities obtained at the pH of 6.0 was 1.97 mg/g. The estimated thermodynamic values of free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) indicated a spontaneous and an endothermic process. Furthermore, the TA-MWCNTs was magnetized for separation of boron-contaminated adsorbent from aqueous solution by applying magnetic field. The results showed that magnetic TA-MWCNTs particles were separated effectively after adsorption from contaminated water. PMID:24393401

  5. Boronic Acid Flux Synthesis and Crystal Growth of Uranium and Neptunium Boronates and Borates: A Low Temperature Route to the First Neptunium(V) Borate

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Miller, Hannah M.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-10-04

    Molten methylboronic acid has been used as a reactive flux to prepare the first neptunium(V) borate, NpO2[B3O4(OH)2] (NpBO-1), and the first actinide boronate, UO2(CH3BO2)(H2O) (UCBO-1). NpBO-1 contains cation-cation interactions between the neptunyl units. In contrast, the presence of the methyl groups in the uranyl boronate leads to a one-dimensional structure.

  6. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    PubMed

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated. PMID:25084408

  7. Isomer-sensitive deboronation in reductive aminations of aryl boronic acids

    SciTech Connect

    Jones, Brad Howard; Wheeler, David R.; Wheeler, Jill S.; Miller, Lance Lee; Alam, Todd M.; Spoerke, Erik David

    2015-09-05

    Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

  8. Isomer-sensitive deboronation in reductive aminations of aryl boronic acids

    DOE PAGESBeta

    Jones, Brad Howard; Wheeler, David R.; Wheeler, Jill S.; Miller, Lance Lee; Alam, Todd M.; Spoerke, Erik David

    2015-09-05

    Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

  9. Boronic Acid functionalized core-shell polymer nanoparticles prepared by distillation precipitation polymerization for glycopeptide enrichment.

    PubMed

    Qu, Yanyan; Liu, Jianxi; Yang, Kaiguang; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2012-07-16

    The boronic acid-functionalized core-shell polymer nanoparticles, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@4-vinylphenylboronic acid (poly(MBA-co-MAA)@VPBA), were successfully synthesized for enriching glycosylated peptides. Such nanoparticles were composed of a hydrophilic polymer core prepared by distillation precipitation polymerization (DPP) and a boronic acid-functionalized shell designed for capturing glycopeptides. Owing to the relatively large amount of residual vinyl groups introduced by DPP on the core surface, the VPBA monomer was coated with high efficiency, working as the shell. Moreover, the overall polymerization route, especially the use of DPP, made the synthesis of nanoparticles facile and time-saving. With the poly(MBA-co-MAA)@VPBA nanoparticles, 18 glycopeptides from horseradish peroxidase (HRP) digest were captured and identified by MALDI-TOF mass spectrometric analysis, relative to eight glycopeptides enriched by using commercially available meta-aminophenylboronic acid agarose under the same conditions. When the concentration of the HRP digest was decreased to as low as 5 nmol, glycopeptides could still be selectively isolated by the prepared nanoparticles. Our results demonstrated that the synthetic poly(MBA-co-MAA)@VPBA nanoparticles might be a promising selective enrichment material for glycoproteome analysis. PMID:22707097

  10. Design and synthesis of boronic acid inhibitors of endothelial lipase.

    PubMed

    O'Connell, Daniel P; LeBlanc, Daniel F; Cromley, Debra; Billheimer, Jeffrey; Rader, Daniel J; Bachovchin, William W

    2012-02-01

    Endothelial lipase (EL) and lipoprotein lipase (LPL) are homologous lipases that act on plasma lipoproteins. EL is predominantly a phospholipase and appears to be a key regulator of plasma HDL-C. LPL is mainly a triglyceride lipase regulating (V)LDL levels. The existing biological data indicate that inhibitors selective for EL over LPL should have anti-atherogenic activity, mainly through increasing plasma HDL-C levels. We report here the synthesis of alkyl, aryl, or acyl-substituted phenylboronic acids that inhibit EL. Many of the inhibitors evaluated proved to be nearly equally potent against both EL and LPL, but several exhibited moderate to good selectivity for EL. PMID:22225633

  11. Boronic acid-containing aminopyridine- and aminopyrimidinecarboxamide CXCR1/2 antagonists: Optimization of aqueous solubility and oral bioavailability.

    PubMed

    Schuler, Aaron D; Engles, Courtney A; Maeda, Dean Y; Quinn, Mark T; Kirpotina, Liliya N; Wicomb, Winston N; Mason, S Nicholas; Auten, Richard L; Zebala, John A

    2015-09-15

    The chemokine receptors CXCR1 and CXCR2 are important pharmaceutical targets due to their key roles in inflammatory diseases and cancer progression. We have previously identified 2-[5-(4-fluoro-phenylcarbamoyl)-pyridin-2-ylsulfanylmethyl]-phenylboronic acid (SX-517) and 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide (SX-576) as potent non-competitive boronic acid-containing CXCR1/2 antagonists. Herein we report the synthesis and evaluation of aminopyridine and aminopyrimidine analogs of SX-517 and SX-576, identifying (2-{(benzyl)[(5-boronic acid-2-pyridyl)methyl]amino}-5-pyrimidinyl)(4-fluorophenylamino)formaldehyde as a potent chemokine antagonist with improved aqueous solubility and oral bioavailability. PMID:26248802

  12. Effect of initial composition on boron carbide production by SHS process followed by acid leaching

    NASA Astrophysics Data System (ADS)

    Alkan, Murat; Sonmez, M. Seref; Derin, Bora; Yücel, Onuralp

    2012-11-01

    In this study, iron-free boron carbide powders (B4C) were produced from the milled SHS (self-propagating high temperature synthesis) products followed by leaching in an aqueous hydrochloric acid (HCl) media. The SHS mixtures were composed of boron oxide (B2O3), carbon black and magnesium. Thermochemical simulations were performed to estimate the effect of initial composition on the SHS process. In the SHS experiments, it was found that the formations of boron carbide and magnesium borates were directly related with B2O3 and carbon black contents in the initial SHS mixture. The aqueous HCl leaching of the SHS products did not only eliminate the unwanted byproducts (i.e. MgO, Mg3B2O6 and Mg2B2O5) but also enhanced substantially the pore structure of the particles. Even though the leached SHS particles (d0.5 = 7.96 μm) were much coarser than that of the commercial powder (d0.5 = 1.73 μm), the surface area of the leached product (15.56 m2/g) was found to be larger than that of commercial one (4.92 m2/g).

  13. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: kinetic, isotherm and thermodynamic studies.

    PubMed

    Kara, Ali; Demirbel, Emel; Tekin, Nalan; Osman, Bilgen; Beşirli, Necati

    2015-04-01

    Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)-vinylphenyl boronic acid(VPBA)) [m-poly(EG-VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG-VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG-VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG-VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin-Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG-VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, ΔG(0) enthalpy change, ΔH(0); and entropy change, ΔS(0)) for the adsorption have been evaluated. PMID:25666882

  14. Chan-Evans-Lam Amination of Boronic Acid Pinacol (BPin) Esters: Overcoming the Aryl Amine Problem.

    PubMed

    Vantourout, Julien C; Law, Robert P; Isidro-Llobet, Albert; Atkinson, Stephen J; Watson, Allan J B

    2016-05-01

    The Chan-Evans-Lam reaction is a valuable C-N bond forming process. However, aryl boronic acid pinacol (BPin) ester reagents can be difficult coupling partners that often deliver low yields, in particular in reactions with aryl amines. Herein, we report effective reaction conditions for the Chan-Evans-Lam amination of aryl BPin with alkyl and aryl amines. A mixed MeCN/EtOH solvent system was found to enable effective C-N bond formation using aryl amines while EtOH is not required for the coupling of alkyl amines. PMID:27045570

  15. Electrochemical incineration of sulfanilic acid at a boron-doped diamond anode.

    PubMed

    El-Ghenymy, Abdellatif; Arias, Conchita; Cabot, Pere Lluís; Centellas, Francesc; Garrido, José Antonio; Rodríguez, Rosa María; Brillas, Enric

    2012-06-01

    The anodic oxidation of sulfanilic acid solutions has been studied in acidic medium using a divided cell with a boron-doped diamond (BDD) anode and a stainless steel cathode. Overall mineralization was achieved under all experimental conditions tested due to the efficient destruction of sulfanilic acid and all its by-products with hydroxyl radicals generated at the BDD anode from water oxidation. The alternative use of an undivided cell with the same electrodes gave rise to the coating of the cathode with polymeric compounds, thus preventing the complete electrochemical incineration of sulfanilic acid. The solutions treated in the anodic compartment of the divided cell were degraded at similar rate under pH regulation within the pH interval 2.0-6.0. The mineralization current efficiency was enhanced when the applied current decreased and the initial substrate concentration increased. The decay of sulfanilic acid was followed by reversed-phase HPLC, showing a pseudo first-order kinetics. Hydroquinone and p-benzoquinone were identified as aromatic intermediates by gas chromatography-mass spectrometry and/or reversed-phase HPLC. Maleic, acetic, formic, oxalic and oxamic acids were detected as generated carboxylic acids by ion-exclusion HPLC. Ionic chromatographic analysis of electrolyzed solutions revealed that the N content of sulfanilic acid was mainly released as NH(4)(+) ion and in much smaller proportion as NO(3)(-) ion. PMID:22365277

  16. A General, Simple Catalyst for Enantiospecific Cross Couplings of Benzylic Ammonium Triflates and Boronic Acids: No Phosphine Ligand Required

    PubMed Central

    Basch, Corey H.; Song, Ye-Geun; Watson, Mary P.

    2014-01-01

    Highly improved conditions for the enantiospecific cross coupling of benzylic ammonium triflates with boronic acids are reported. This method relies on the use of Ni(cod)2 without ancillary phosphine or N-heterocyclic carbene ligands as catalyst. These conditions enable the coupling of new classes of boronic acids and benzylic ammonium triflates. In particular, both heteroaromatic and vinyl boronic acids are well tolerated as coupling partners. In addition, these conditions enable the use of ammonium triflates with a variety of substituents at the benzylic stereocenter. Further, naphthyl-substitution is not required on the benzylic ammonium triflate; ammonium triflates with simple aromatic substituents also undergo this coupling. Good to high yields and levels of stereochemical fidelity are observed. This new catalyst system greatly expands the utility of enantiospecific cross couplings of these amine-derived substrates for the preparation of highly enantioenriched products. PMID:25364060

  17. Boronic acid-containing proteasome inhibitors: alert to potential pharmaceutical bioactivation.

    PubMed

    Li, Austin C; Yu, Erya; Ring, Steven C; Chovan, James P

    2013-04-15

    Medicinal chemists try to avoid certain organic functional groups, summarized in an ever-growing list, in order to avoid the potential bioactivation to reactive metabolites. To add to that alert list, we report herein that boronic acid-containing compound structures, such as those found in proteasome inhibitors bortezomib and ixazomib, can become bioactivated to chemically reactive imine amide metabolites. Test compounds, ixazomib and bortezomib, were incubated in vitro using human liver fractions containing cytosol and microsomes (S9) under conventional conditions in the presence of GSH. Metabolites were then analyzed using LC-MS(n) with or without online hydrogen-deuterium exchange (HDX) liquid chromatography coupled with an LTQ-Orbitrap. The exact mass measurements of both the precursor and product ions were acquired through data dependent acquisition and compared with theoretical values of proposed fragment ions. Upon deboronation catalyzed by cytochrome P450 enzymes, both test compounds formed imine amide metabolites that were identified by high resolution exact mass measurements in both normal aqueous and HDX HPLC-MS analysis. GSH conjugates were also identified and were postulated as nucleophilic addition of GSH to the imine amide metabolites. All mass spectrometric and HDX measurements of these GSH conjugates proved that the GSH unit was added to the carbon atom of the imine amide partial structure, hence demonstrating the electrophilic property of these imine amide metabolites. The awareness of the formation of electrophilic imine amide metabolites from boronic acid-containing compounds, where the boron atom is bonded to a carbon atom adjacent to an amide nitrogen, should help in drug candidate design and optimization with regard to avoiding potential bioactivation. PMID:23514361

  18. Palladium(II)-Catalyzed Synthesis of Sulfinates from Boronic Acids and DABSO: A Redox-Neutral, Phosphine-Free Transformation.

    PubMed

    Deeming, Alex S; Russell, Claire J; Willis, Michael C

    2016-01-11

    A redox-neutral palladium(II)-catalyzed conversion of aryl, heteroaryl, and alkenyl boronic acids into sulfinate intermediates, and onwards to sulfones and sulfonamides, has been realized. A simple Pd(OAc)2 catalyst, in combination with the sulfur dioxide surrogate 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO), is sufficient to achieve rapid and high-yielding conversion of the boronic acids into the corresponding sulfinates. Addition of C- or N-based electrophiles then allows conversion into sulfones and sulfonamides, respectively, in a one-pot, two-step process. PMID:26596861

  19. Fluorinated Boronic Acid-Appended Bipyridinium Salts for Diol Recognition and Discrimination via (19)F NMR Barcodes.

    PubMed

    Axthelm, Jörg; Görls, Helmar; Schubert, Ulrich S; Schiller, Alexander

    2015-12-16

    Fluorinated boronic acid-appended benzyl bipyridinium salts, derived from 4,4'-, 3,4'-, and 3,3'-bipyridines, were synthesized and used to detect and differentiate diol-containing analytes at physiological conditions via (19)F NMR spectroscopy. An array of three water-soluble boronic acid receptors in combination with (19)F NMR spectroscopy discriminates nine diol-containing bioanalytes--catechol, dopamine, fructose, glucose, glucose-1-phosphate, glucose-6-phosphate, galactose, lactose, and sucrose--at low mM concentrations. Characteristic (19)F NMR fingerprints are interpreted as two-dimensional barcodes without the need of multivariate analysis techniques. PMID:26595191

  20. Design, synthesis, crystal structures and antimicrobial activity of sulfonamide boronic acids as β-lactamase inhibitors

    PubMed Central

    Eidam, Oliv; Romagnoli, Chiara; Caselli, Emilia; Babaoglu, Kerim; Pohlhaus, Denise Teotico; Karpiak, Joel; Bonnet, Richard; Shoichet, Brian K.; Prati, Fabio

    2010-01-01

    We investigated a series of sulfonamide boronic acids that resulted from the merging of two unrelated AmpC β-lactamase inhibitor series. The new boronic acids differed in the replacement of the canonical carboxamide, found in all penicillin and cephalosporin antibiotics, with a sulfonamide. Surprisingly, these sulfonamides had a highly distinct structure-activity relationship from the previously explored carboxamides, high ligand efficiencies (up to 0.91), Ki values down to 25 nM and up to 23 times better for smaller analogs. Conversely, Ki values were 10 to 20 times worse for larger molecules than in the carboxamide congener series. X-ray crystal structures (1.6–1.8 Å) of AmpC with three of the new sulfonamides suggest that this altered structure-activity relationship results from the different geometry and polarity of the sulfonamide versus the carboxamide. The most potent inhibitor reversed β-lactamase-mediated resistance to third generation cephalosporins, lowering their minimum inhibitory concentrations up to 32-fold in cell culture. PMID:20945905

  1. Click Chemistry in Lead Optimization of Boronic Acids as β-Lactamase Inhibitors.

    PubMed

    Caselli, Emilia; Romagnoli, Chiara; Vahabi, Roza; Taracila, Magdalena A; Bonomo, Robert A; Prati, Fabio

    2015-07-23

    Boronic acid transition-state inhibitors (BATSIs) represent one of the most promising classes of β-lactamase inhibitors. Here we describe a new class of BATSIs, namely, 1-amido-2-triazolylethaneboronic acids, which were synthesized by combining the asymmetric homologation of boronates with copper-catalyzed azide-alkyne cycloaddition for the stereoselective insertion of the amido group and the regioselective formation of the 1,4-disubstituted triazole, respectively. This synthetic pathway, which avoids intermediate purifications, proved to be flexible and efficient, affording in good yields a panel of 14 BATSIs bearing three different R1 amide side chains (acetamido, benzylamido, and 2-thienylacetamido) and several R substituents on the triazole. This small library was tested against two clinically relevant class C β-lactamases from Enterobacter spp. and Pseudomonas aeruginosa. The K(i) value of the best compound (13a) was as low as 4 nM with significant reduction of bacterial resistance to the combination of cefotaxime/13a. PMID:26102369

  2. Arginase-boronic acid complex highlights a physiological role in erectile function.

    PubMed

    Cox, J D; Kim, N N; Traish, A M; Christianson, D W

    1999-11-01

    The crystal structure of the complex between the binuclear manganese metalloenzyme arginase and the boronic acid analog of L-arginine, 2(S)-amino-6-boronohexanoic acid (ABH), has been determined at 1.7 A resolution from a crystal perfectly twinned by hemihedry. ABH binds as the tetrahedral boronate anion, with one hydroxyl oxygen symmetrically bridging the binuclear manganese cluster and a second hydroxyl oxygen coordinating to Mn2+A. This binding mode mimics the transition state of a metal-activated hydroxide mechanism. This transition state structure differs from that occurring in NO biosynthesis, thereby explaining why ABH does not inhibit NO synthase. We also show that arginase activity is present in the penis. Accordingly, the tight binding and specificity of ABH allows us to probe the physiological role of arginase in modulating the NO-dependent smooth muscle relaxation required for erection. Strikingly, ABH causes significant enhancement of nonadrenergic, noncholinergic nerve-mediated relaxation of penile corpus cavernosum smooth muscle, suggesting that arginase inhibition sustains L-arginine concentrations for NO synthase activity. Therefore, human penile arginase is a potential target for therapeutic intervention in the treatment of erectile dysfunction. PMID:10542097

  3. A novel fluorescent vesicular sensor for saccharides based on boronic acid-diol interaction.

    PubMed

    Zhang, Yujian; He, Zhenfeng; Li, Guowen

    2010-04-15

    A novel amphiphile containing two functional groups of both naphthalene and boronic acid, 2-(hexadecyloxy)-naphthalene-6-boronic acid (HNBA), has been synthesized. Scanning electron microscopy (SEM) indicated the formation of bilayer vesicles in the ethanol/water solution (Phi=0.6). Differential scanning calorimetry (DSC) established the presence of crystal-to-liquid crystal transition at 63.36 degrees C. The vesicular fluorescence properties upon binding with carbohydrates have been studied in ethanol/water buffer at pH 7.4. Addition of saccharides to the vesicular solution, the fluorescent intensities of naphthalene in HNBA vesicles centered at 348 nm decreased dramatically with increasing concentration of saccharides. The change tendency of fluorescent intensities of the HNAB vesicles with concentration of saccharides followed in the order of fructose>galactose>maltose>glucose. The pH profiles of the fluorescence intensity were studied in the absence and in the presence of sugars. Also, the urine sample induced spectral changes of the HNBA vesicles were studied. These results suggest that the HNBA vesicles may be developed as a continuous monitoring and implantable fluorescence vesicular sensor, which might be applied in the practical field. PMID:20188967

  4. Nitrogen-15 NMR spectroscopy of the catalytic-triad histidine of a serine protease in peptide boronic acid inhibitor complexes

    SciTech Connect

    Bachovchin, W.W.; Wong, W.Y.L.; Farr-Jones, S. ); Shenvi, A.B.; Kettner, C.A. )

    1988-10-04

    {sup 15}N NMR spectroscopy was used to examine the active-site histidyl residue of {alpha}-lytic protease in peptide boronic acid inhibitor complexes. Two distinct types of complexes were observed: (1) Boronic acids that are analogues of substrates form complexes in which the active-site imidazole ring is protonated and both imidazole N-H protons are strongly hydrogen bonded. (2) Boronic acids that are not substrate analogues form complexes in which N{sup {epsilon}2} of the active-site histidine is covalently bonded to the boron atom of the inhibitor. The proton bound to N{sup {delta}1} of the histidine in these histidine-boronate adducts remains strongly hydrogen bonded, presumably to the active-site aspartate. In both types of complexes the N-H protons of His-57 exchange unusually slowly as evidenced by the room temperature visibility of the low-field {sup 1}H resonances and the {sup 15}N-H spin couplings. These results indicate that occupancy of the specificity subsites may be required to fully form the transition-state binding site. The significance of these findings for understanding inhibitor binding and the catalytic mechanism of serine proteases is discussed.

  5. Synthesis and Evaluation of Aryl Boronic Acids as Fluorescent Artificial Receptors for Biological Carbohydrates

    PubMed Central

    Craig, Sandra

    2011-01-01

    Carbohydrates in various forms play a vital role in numerous critical biological processes. The detection of such saccharides can give insight into the progression of such diseases such as cancer. Boronic acids react with 1,2 and 1,3 diols of saccharides in non-aqueous or basic aqueous media. Herein, we describe the design, synthesis and evaluation of three bisboronic acid fluorescent probes, each having about ten linear steps in its synthesis. Among these compounds that were evaluated, 9b was shown to selectively label HepG2, liver carcinoma cell line within a concentration range of 0.5–10 μM in comparison to COS-7, a normal fibroblast cell line. PMID:22177855

  6. Nitrogen-15 NMR spectroscopy of the catalytic-triad histidine of a serine protease in peptide boronic acid inhibitor complexes.

    PubMed

    Bachovchin, W W; Wong, W Y; Farr-Jones, S; Shenvi, A B; Kettner, C A

    1988-10-01

    15N NMR spectroscopy was used to examine the active-site histidyl residue of alpha-lytic protease in peptide boronic acid inhibitor complexes. Two distinct types of complexes were observed: (1) Boronic acids that are analogues of substrates form complexes in which the active-site imidazole ring is protonated and both imidazole N-H protons are strongly hydrogen bonded. With the better inhibitors of the class this arrangement is stable over the pH range 4.0-10.5. The results are consistent with a putative tetrahedral intermediate like complex involving a negatively charged, tetrahedral boron atom covalently bonded to O gamma of the active-site serine. (2) Boronic acids that are not substrate analogues form complexes in which N epsilon 2 of the active-site histidine is covalently bonded to the boron atom of the inhibitor. The proton bound to N delta 1 of the histidine in these histidine-boronate adducts remains strongly hydrogen bonded, presumably to the active-site aspartate. Benzeneboronic acid, which falls in this category, forms an adduct with histidine. In both types of complexes the N-H protons of His-57 exchange unusually slowly as evidenced by the room temperature visibility of the low-field 1H resonances and the 15N-H spin couplings. These results, coupled with the kinetic data of the preceding paper [Kettner, C. A., Bone, R., Agard, D. A., & Bachovchin, W. W. (1988) Biochemistry (preceding paper in this issue)], indicate that occupancy of the specificity subsites may be required to fully form the transition-state binding site. The significance of these findings for understanding inhibitor binding and the catalytic mechanism of serine proteases is discussed. PMID:3207700

  7. Kinetic properties of the binding of alpha-lytic protease to peptide boronic acids.

    PubMed

    Kettner, C A; Bone, R; Agard, D A; Bachovchin, W W

    1988-10-01

    The kinetic parameters for peptide boronic acids in their interaction with alpha-lytic protease were determined and found to be similar to those of other serine proteases [Kettner, C., & Shenvi, A. B. (1984) J. Biol. Chem. 259, 15106-15114]. alpha-Lytic protease hydrolyzes substrates with either alanine or valine in the P1 site and has a preference for substrate with a P1 alanine. The most effective inhibitors are tri- and tetrapeptide analogues that have a -boroVal-OH residue in the P1 site. At pH 7.5, MeOSuc-Ala-Ala-Pro-boroVal-OH has a Ki of 6.4 nM and Boc-Ala-Pro-boroVal-OH has a Ki of 0.35 nM. Ac-boroVal-OH and Ac-Pro-boroVal-OH are 220,000- and 500-fold less effective, respectively, than the tetrapeptide analogue. The kinetic properties of the tri- and tetrapeptide analogues are consistent with the mechanism for slow-binding inhibition, E + I in equilibrium EI in equilibrium EI*, while the less effective inhibitors are simple competitive inhibitors. MeO-Suc-Ala-Ala-Pro-boroAla-OH is a simple competitive inhibitor with a Ki of 67 nM at pH 7.5. Other peptide boronic acids, which are analogues of nonsubstrates, are less effective than substrate analogues but still are effective competitive inhibitors. For example, MeOSuc-Ala-Ala-Pro-boroPhe-OH has a Ki of 0.54 microM although substrates with a phenylalanine in the P1 position are not hydrolyzed. Binding for boronic acid analogues of both substrate and nonsubstrate analogues is pH dependent with higher affinity near pH 7.5. Similar binding properties have been observed for pancreatic elastase. Both enzymes have almost identical requirements for an extended peptide inhibitor sequence in order to exhibit highly effective binding and slow-binding characteristics.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3207699

  8. Pd-Catalyzed, Cu(I)-Mediated Cross-Couplings of Bisarylthiocyclobutenediones with Boronic Acids and Organostannanes

    PubMed Central

    Aguilar-Aguilar, Angélica; Liebeskind, Lanny S.; Peña-Cabrera, Eduardo

    2009-01-01

    Bisarylthiocyclobutenedione 7 reacted smoothly with a variety of both organostannanes and (hetero)aryl boronic acids in the presence of a catalytic amount of Pd and a stoichiometric amount of CuTC, to produce symmetrical disubstituted cyclobutenediones in yields that range from 37 to 94% (18 examples). PMID:17892299

  9. Dipeptide boronic acid inhibitors of dipeptidyl peptidase IV: determinants of potency and in vivo efficacy and safety.

    PubMed

    Connolly, Beth A; Sanford, David G; Chiluwal, Amrita K; Healey, Sarah E; Peters, Diane E; Dimare, Matthew T; Wu, Wengen; Liu, Yuxin; Maw, Hlaing; Zhou, Yuhong; Li, Youhua; Jin, Zhiping; Sudmeier, James L; Lai, Jack H; Bachovchin, William W

    2008-10-01

    Dipeptidyl peptidase IV (DPP-IV; E.C. 3.4.14.5), a serine protease that degrades the incretin hormones GLP-1 and GIP, is now a validated target for the treatment of type 2 diabetes. Dipeptide boronic acids, among the first, and still among the most potent DPP-IV inhibitors known, suffer from a concern over their safety. Here we evaluate the potency, in vivo efficacy, and safety of a selected set of these inhibitors. The adverse effects induced by boronic acid-based DPP-IV inhibitors are essentially limited to what has been observed previously for non-boronic acid inhibitors and attributed to cross-reactivity with DPP8/9. While consistent with the DPP8/9 hypothesis, they are also consistent with cross-reactivity with some other intracellular target. The results further show that the potency of simple dipeptide boronic acid-based inhibitors can be combined with selectivity against DPP8/9 in vivo to produce agents with a relatively wide therapeutic index (>500) in rodents. PMID:18783201

  10. Effect of water stress and foliar boron application on seed protein oil fatty acids and nitrogen metabolism in soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to investigate the effects of water stress and FB on seed protein, oil, fatty acids, nitra...

  11. Direct Access to α,α-Difluoroacylated Arenes by Palladium-Catalyzed Carbonylation of (Hetero)Aryl Boronic Acid Derivatives.

    PubMed

    Andersen, Thomas L; Frederiksen, Mette W; Domino, Katrine; Skrydstrup, Troels

    2016-08-22

    A palladium-catalyzed carbonylative coupling of (hetero)aryl boronates or boronic acid salts with carbon monoxide and α-bromo-α,α-difluoroamides and bromo-α,α-difluoroesters is described herein. The method is useful for the synthesis of a diverse selection of (hetero)aryl α,α-difluoro-β-ketoamides and α,α-difluoro-β-ketoesters, which are useful building blocks for the generation of functionalized difluoroacylated and difluoroalkyl arenes. The method could be further extended to a one-pot protocol for the formation of difluoroacetophenones. PMID:27346239

  12. Polymeric Cryogel-Based Boronate Affinity Chromatography for Separation of Ribonucleic Acid from Bacterial Extracts.

    PubMed

    Shakya, Akhilesh Kumar; Srivastava, Akshay; Kumar, Ashok

    2015-01-01

    Three-dimensional monolithic columns are preferred stationary phase in column chromatography. Conventional columns based on silica or particles are efficient in bioseparation though associated with limitations of nonspecific interaction and uneven porosity that causes high mass transfer resistance for the movement of big molecules. Cryogels as a monolith column have shown promising application in bioseparation. Cryogels column can be synthesized in the form of a monolith at sub-zero temperature through gelation of pre-synthesized polymers or polymerization of monomers. Cryogels are macroporous and mechanically stable materials. They have open interconnected micron-sized pores with a wide range of porosity (10-200 μm). Current protocol demonstrated the ability of poly(hydroxymethyl methacrylate)-co-vinylphenyl boronic acid p(HEMA-co-VPBA) cryogel matrix for selective separation of RNA from the bacterial crude extract. PMID:26623972

  13. Potent inhibitors of HCV-NS3 protease derived from boronic acids

    SciTech Connect

    Venkatraman, Srikanth; Wu, Wanli; Prongay, Andrew; Girijavallabhan, Viyyoor; Njoroge, F. George

    2009-07-23

    Chronic hepatitis C infection is the leading causes for cirrhosis of the liver and hepatocellular carcinoma, leading to liver failure and liver transplantation. The etiological agent, HCV virus produces a single positive strand of RNA that is processed with the help of serine protease NS3 to produce mature virus. Inhibition of NS3 protease can be potentially used to develop effective drugs for HCV infections. Numerous efforts are now underway to develop potent inhibitors of HCV protease that contain ketoamides as serine traps. Herein we report the synthesis of a series of potent inhibitors that contain a boronic acid as a serine trap. The activity of these compounds were optimized to 200 pM. X-ray structure of compound 17 bound to NS3 protease is also discussed.

  14. Rapid Formation of Cell Aggregates and Spheroids Induced by a "Smart" Boronic Acid Copolymer.

    PubMed

    Amaral, Adérito J R; Pasparakis, George

    2016-09-01

    Cell surface engineering has emerged as a powerful approach to forming cell aggregates/spheroids and cell-biomaterial ensembles with significant uses in tissue engineering and cell therapeutics. Herein, we demonstrate that cell membrane remodeling with a thermoresponsive boronic acid copolymer induces the rapid formation of spheroids using either cancer or cardiac cell lines under conventional cell culture conditions at minute concentrations. It is shown that the formation of well-defined spheroids is accelerated by at least 24 h compared to non-polymer-treated controls, and, more importantly, the polymer allows for fine control of the aggregation kinetics owing to its stimulus response to temperature and glucose content. On the basis of its simplicity and effectiveness to promote cellular aggregation, this platform holds promise in three-dimensional tissue/tumor modeling and tissue engineering applications. PMID:27571512

  15. Correlating Physicochemical Properties of Boronic Acid-Chitosan Conjugates to Glucose Adsorption Sensitivity

    PubMed Central

    Asantewaa, Yaa; Aylott, Jonathan; Burley, Jonathan C.; Billa, Nashiru; Roberts, Clive J.

    2012-01-01

    Phenyl boronic acid (PBA), which is known to interact with glucose, was covalently bonded to chitosan by direct reductive N-alkylation of chitosan with 4-formylphenylboronic acid (4-FPBA). Evidence of PBA bonding on chitosan was assessed by FTIR, ToF-SIMS, SEM, DSC and glucose adsorption sensitivity measurements. FTIR spectra showed strong signals at 1560 and 630 cm−1 indicating the formation of p-substituted benzene. Similarly, ToF-SIMS analyses on the conjugates registered fragments of boron ion (B−) at 11.0 m/z whose intensity increased in proportion to 4-FPBA loading. The degree to which PBA was bonded to chitosan was related to the 4-FPBA load used in the reaction (termed F1 through to F6 with increasing 4-FPBA load). Glucose adsorption sensitivity to PBA-bonded chitosan was directly related to the amount of PBA functionality within the conjugates and the physical nature of the matrices (porous or crystalline). Topographic analysis by SEM revealed that PBA-chitosan conjugates F1, F2 and F3 have porous matrices and their sensitivity to glucose adsorption was directly proportional to the degree of PBA substitution onto chitosan. Conversely, conjugates F4, F5 and F6 appeared crystalline under SEM and glucose adsorption sensitivity decreased in proportion to amount of PBA bonded to chitosan. The crystalline nature of the conjugates was confirmed by DSC, where the exothermic event related to the melting of the bonded PBA moiety, occurred at 338 °C. Thus, decreased sensitivity to glucose adsorption by the conjugates can be ascribed to the crystallinity imparted by increased content of the bonded PBA moiety, providing an optimal loading of PBA in terms of maximizing response to glucose. PMID:24300397

  16. Palladium-Catalyzed Room-Temperature Acylative Suzuki Coupling of High-Order Aryl Borons with Carboxylic Acids.

    PubMed

    Si, Shufen; Wang, Chen; Zhang, Nan; Zou, Gang

    2016-05-20

    This note describes a dimethyl dicarbonate-assisted, Pd(OAc)2/PPh3-catalyzed acylative Suzuki coupling of carboxylic acids with diarylborinic acids or tetraarylboronates for practical and efficient synthesis of sterically undemanding aryl ketones at room temperature. More than just cost-effective alternatives to aryl boronic acids, diarylborinic acids and tetraarylboronates displayed higher reactivity in the acylative Suzuki coupling. A variety of alkyl aryl ketones, including those bearing a hydroxy, bromo, or carbonyl group, could be readily obtained in modest to excellent yields. PMID:27100118

  17. Corrosion resistance of inconel 690 to borax, boric acid, and boron nitride at 1100{degrees}C

    SciTech Connect

    Imrich, K.J.

    1996-12-12

    Significant general and localized corrosion was observed on Inconel 690 coupons following exposure to borax, boric acid and boron nitride at 1100{degrees}C. Severe localized attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack (IGA) of the Inconel 690 was also observed. Severe internal void formation and IGA (30 mils penetration after 3 days) was observed in the coupon exposed to boric acid. Both borax and boric acid remove the protective chromium oxide; however, this layer can be reestablished by heating the Inconel 690 to 975 {degrees}C in air for several hours. Inconel 690 in direct contact with boron nitride resulted in the formation of a thick chromium borate layer, a general corrosion rate of 50 to 90 mils per year, and internal void formation of 1 mil per day.

  18. Determination of boron in blood, urine and bone by electrothermal atomic absorption spectrometry using zirconium and citric acid as modifiers

    NASA Astrophysics Data System (ADS)

    Burguera, Marcela; Burguera, José Luis; Rondón, Carlos; Carrero, Pablo

    2001-10-01

    A comparative study of various potential chemical modifiers (Au, Ba, Be, Ca, Cr, Ir, La, Lu, Mg, Ni, Pd, Pt, Rh, Ru, Sr, V, W, and Zr), and different 'coating' treatments (Zr, W, and W+Rh) of the pyrolytic graphite platform of a longitudinally heated graphite tube atomizer for thermal stabilization and determination of boron was undertaken. The use of Au, Ba, Be, Cr, Ir, Pt, Rh, Ru, Sr and V as modifiers, and of W+Rh coating produced erratic, and noisy signals, while the addition of La, Ni and Pd as modifiers, and the W coating had positive effects, but with too high background absorption signals, rendering their use unsuitable for boron determination even in aqueous solutions. The atomic absorption signal for boron was increased and stabilized when the platform was coated with Zr, and by the addition of Ca, Mg, Lu, W or Zr as modifiers. Only the addition of 10 μg of Zr as a modifier onto Zr-treated platforms allowed the use of a higher pyrolysis temperature without analyte losses. The memory effect was minimized by incorporating a cleaning step with 10 μl of 50 g l -1 NH 4F HF after every three boron measurements. The addition of 10 μl of 15 g l -1 citric acid together with Zr onto Zr-treated platforms significantly improved the characteristic mass to m0=282 pg, which is adequate for biological samples such as urine and bone, although the sensitivity was still inadequate for the determination of boron in blood of subjects without supplementary diet. Under optimized conditions, the detection limit (3σ) was 60 μg l -1. The amount of boron found in whole blood, urine and femur head samples from patients with osteoporosis was in agreement with values previously reported in the literature.

  19. Pentapeptide Boronic Acid Inhibitors of Mycobacterium tuberculosis MycP1 Protease

    PubMed Central

    Frasinyuk, Mykhaylo S.; Kwiatkowski, Stefan; Wagner, Jonathan M.; Evans, Timothy J.; Reed, Robert W.; Korotkov, Konstantin V.; Watt, David S.

    2014-01-01

    Mycosin protease-1 (MycP1) cleaves ESX secretion-associated protein B (EspB) that is a virulence factor of Mycobacterium tuberculosis, and accommodates an octapeptide, AVKAASLG, as a short peptide substrate. Because peptidoboronic acids are known inhibitors of serine proteases, the synthesis and binding of a boronic acid analog of the pentapeptide cleavage product, AVKAA, was studied using MycP1 variants from M. thermoresistible (MycP1mth), M. smegmatis (MycP1msm) and M. tuberculosis (MycP1mtu). We synthesized the boropentapeptide, HAlaValLysAlaAlaB(OH)2 (1) and the analogous pinanediol PD-protected HAlaValLysAlaAlaBO2(PD) (2) using an Fmoc/Boc peptide strategy. The pinanediol boropentapeptide 2 displayed IC50 values 121.6±25.3 μM for MycP1mth, 93.2±37.3 μM for MycP1msm and 37.9±5.2 μM for MycP1mtu. Such relatively strong binding creates a chance for crystalizing the complex with 2 and finding the structure of the unknown MycP1 catalytic site that would potentially facilitate the development of new anti-tuberculosis drugs. PMID:24915878

  20. Tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization between vinyl ether boronates and vinyl halides: a concise approach to polysubstituted furans.

    PubMed

    Butkevich, Alexey N; Meerpoel, Lieven; Stansfield, Ian; Angibaud, Patrick; Corbu, Andrei; Cossy, Janine

    2013-08-01

    Polysubstituted 2-(ω-hydroxyalkyl)furans were prepared by tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization starting from appropriately substituted 3-haloallylic alcohols and dihydrofuran-, dihydropyran- or glycal-derived pinacol boronates. PMID:23855589

  1. Crystal versus solution structure of enzymes: NMR spectroscopy of a peptide boronic acid-serine protease complex in the crystalline state.

    PubMed

    Farr-Jones, S; Smith, S O; Kettner, C A; Griffin, R G; Bachovchin, W W

    1989-09-01

    The effectiveness of boronic acids as inhibitors of serine proteases has been widely ascribed to the ability of the boronyl group to form a tetrahedral adduct with the active-site serine that closely mimics the putative tetrahedral intermediate or transition state formed with substrates. However, recent 15N NMR studies of alpha-lytic protease (EC 3.4.21.12) in solution have shown that some boronic acids and peptide boronic acids form adducts with the active-site histidine instead of with the serine. Such histidine-boron adducts have not thus far been reported in x-ray diffraction studies of boronic acid-serine protease complexes. Here, we report an 15N NMR study of the MeOSuc-Ala-Ala-Pro-boroPhe complex of alpha-lytic protease in the crystalline state using magic-angle spinning. Previous 15N NMR studies have shown this complex involves the formation of a histidine-boron bond in solution. The 15N NMR spectra of the crystalline complex are essentially identical to those of the complex in solution, thereby showing that the structure of this complex is the same in solution and in the crystal and that both involve formation of a histidine-boron adduct. PMID:2780549

  2. A Three‐Component Assembly Promoted by Boronic Acids Delivers a Modular Fluorophore Platform (BASHY Dyes)†

    PubMed Central

    Santos, Fábio M. F.; Rosa, João N.; Candeias, Nuno R.; Carvalho, Cátia Parente; Matos, Ana I.; Ventura, Ana E.; Florindo, Helena F.; Silva, Liana C.

    2015-01-01

    Abstract The modular assembly of boronic acids with Schiff‐base ligands enabled the construction of innovative fluorescent dyes [boronic acid salicylidenehydrazone (BASHY)] with suitable structural and photophysical properties for live cell bioimaging applications. This reaction enabled the straightforward synthesis (yields up to 99 %) of structurally diverse and photostable dyes that exhibit a polarity‐sensitive green‐to‐yellow emission with high quantum yields of up to 0.6 in nonpolar environments. These dyes displayed a high brightness (up to 54 000 m −1 cm−1). The promising structural and fluorescence properties of BASHY dyes fostered the preparation of non‐cytotoxic, stable, and highly fluorescent poly(lactide‐co‐glycolide) nanoparticles that were effectively internalized by dendritic cells. The dyes were also shown to selectively stain lipid droplets in HeLa cells, without inducing any appreciable cytotoxicity or competing plasma membrane labeling; this confirmed their potential as fluorescent stains. PMID:26691630

  3. Incidence of boron deficiency in bedding plants caused by drought stress or abscicic acid application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growers have reported boron (B) deficiency in pansy (Viola ×wittrockiana) plug production, specifically in plugs grown in the high heat and humidity conditions of summer. Past studies have reported that soil moisture has an impact on boron availability. To simulate drought conditions, 'Dynamite Ye...

  4. The Hypolipidemic and Anti-Inflammatory Activity of Boronated Aromatic Amino Acids in CF1 Male Mice

    PubMed Central

    Miller, Merrill C.; Sood, A.; Spielvogel, Bernard F.

    1999-01-01

    The boronated aromatic amino acids were shown to be potent hypolipidemic agents in mice lowering both serum cholesterol and triglycerides after 16 days. Selective compounds were as effective as the clinical standards. Furthermore, the compounds were effective anti-inflammatory agents reducing local and central pain as well as suppressing LPS induced endotoxic shock in mice. These agents inhibited lysosomal and proteolytic enzymes of the liver and macrophages as a part of their mechanism of action. PMID:18475910

  5. Dual Catalysis Using Boronic Acid and Chiral Amine: Acyclic Quaternary Carbons via Enantioselective Alkylation of Branched Aldehydes with Allylic Alcohols.

    PubMed

    Mo, Xiaobin; Hall, Dennis G

    2016-08-31

    A ferrocenium boronic acid salt activates allylic alcohols to generate transient carbocations that react with in situ-generated chiral enamines from branched aldehydes. The optimized conditions afford the desired acyclic products embedding a methyl-aryl quaternary carbon center with up to 90% yield and 97:3 enantiomeric ratio, with only water as the byproduct. This noble-metal-free method complements alternative methods that are incompatible with carbon-halogen bonds and other sensitive functional groups. PMID:27518200

  6. Targeting class A and C serine β-lactamases with a broad-spectrum boronic acid derivative.

    PubMed

    Tondi, Donatella; Venturelli, Alberto; Bonnet, Richard; Pozzi, Cecilia; Shoichet, Brian K; Costi, Maria Paola

    2014-06-26

    Production of β-lactamases (BLs) is the most widespread resistance mechanism adopted by bacteria to fight β-lactam antibiotics. The substrate spectrum of BLs has become increasingly broad, posing a serious health problem. Thus, there is an urgent need for novel BL inhibitors. Boronic acid transition-state analogues are able to reverse the resistance conferred by class A and C BLs. We describe a boronic acid analogue possessing interesting and potent broad-spectrum activity vs class A and C serine-based BLs. Starting from benzo(b)thiophene-2-boronic acid (BZBTH2B), a nanomolar non-β-lactam inhibitor of AmpC that can potentiate the activity of a third-generation cephalosporin against AmpC-producing resistant bacteria, we designed a novel broad-spectrum nanomolar inhibitor of class A and C BLs. Structure-based drug design (SBDD), synthesis, enzymology data, and X-ray crystallography results are discussed. We clarified the inhibitor binding geometry responsible for broad-spectrum activity vs serine-active BLs using double mutant thermodynamic cycle studies. PMID:24882105

  7. A Metal and Base-Free Chemoselective Primary Amination of Boronic Acids Using Cyanamidyl/Arylcyanamidyl Radical as Aminating Species: Synthesis and Mechanistic Studies by Density Functional Theory.

    PubMed

    Chatterjee, Nachiketa; Arfeen, Minhajul; Bharatam, Prasad V; Goswami, Avijit

    2016-06-17

    An efficient, metal and base-free, chemoselective synthesis of aryl-, heteroaryl-, and alkyl primary amines from the corresponding boronic acids has been achieved at ambient temperature mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA) and N-bromosuccinimide (NBS) using cyanamidyl/arylcyanamidyl radicals as the aminating species. The primary amine compounds were initially obtained as their corresponding ammonium trifluoroacetate salts which, on treatment with aq NaOH, provide the free amines. Finally, the primary amines were isolated through column chromatography over silica-gel using hexane-EtOAc solvent system as the eluent. The reactions are sufficiently fast, completing within 1 h. Quantum chemical calculations in combination with experimental observations validate that the ipso amination of substituted boronic acids involves the formation of cyanamidyl/arylcyanamidyl radical, followed by regiospecific interaction of its nitrile-N center with boron atom of the boronic acids, leading to chemoselective primary amination. PMID:27182931

  8. Validation and scale-up of plasmid DNA purification by phenyl-boronic acid chromatography.

    PubMed

    Gomes, A Gabriela; Azevedo, Ana M; Aires-Barros, M Raquel; Prazeres, D Miguel F

    2012-11-01

    This study addresses the feasibility of scaling-up the removal of host cell impurities from plasmid DNA (pDNA)-containing Escherichia coli lysates by phenyl-boronic (PB) acid chromatography using columns packed with 7.6 and 15.2 cm(3) of controlled porous glass beads (CPG) derivatized with PB ligands. Equilibration was performed with water at 10 cm(3) /min and no conditioning of the lysate feed was required. At a ratio of lysate feed to adsorbent volume of 1.3, 93-96% of pDNA was recovered in the flow through while 66-71% of impurities remained bound (~2.5-fold purification). The entire sequence of loading, washing, elution, and re-equilibration was completed in 20 min. Run-to-run consistency was observed in terms of chromatogram features and performance (yield, purification factor, agarose electrophoresis) across the different amounts of adsorbent (0.75-15.2 cm(3) ) by performing successive injections of lysates prepared independently and containing 3.7 or 6.1 kbp plasmids. The column productivity at large scale was 4 dm(3) of alkaline lysate per hour per dm(3) of PB-CPG resin. The method is rapid, reproducible, simple, and straightforward to scale-up. Furthermore, it is capable of handling heavily contaminated samples, constituting a good alternative to purification techniques such as isopropanol precipitation, aqueous two-phase systems, and tangential flow filtration. PMID:23175141

  9. Evaluation of the radiolabeled boronic acid-based FAP inhibitor MIP-1232 for atherosclerotic plaque imaging.

    PubMed

    Meletta, Romana; Müller Herde, Adrienne; Chiotellis, Aristeidis; Isa, Malsor; Rancic, Zoran; Borel, Nicole; Ametamey, Simon M; Krämer, Stefanie D; Schibli, Roger

    2015-01-01

    Research towards the non-invasive imaging of atherosclerotic plaques is of high clinical priority as early recognition of vulnerable plaques may reduce the incidence of cardiovascular events. The fibroblast activation protein alpha (FAP) was recently proposed as inflammation-induced protease involved in the process of plaque vulnerability. In this study, FAP mRNA and protein levels were investigated by quantitative polymerase chain reaction and immunohistochemistry, respectively, in human endarterectomized carotid plaques. A published boronic-acid based FAP inhibitor, MIP-1232, was synthetized and radiolabeled with iodine-125. The potential of this radiotracer to image plaques was evaluated by in vitro autoradiography with human carotid plaques. Specificity was assessed with a xenograft with high and one with low FAP level, grown in mice. Target expression analyses revealed a moderately higher protein level in atherosclerotic plaques than normal arteries correlating with plaque vulnerability. No difference in expression was determined on mRNA level. The radiotracer was successfully produced and accumulated strongly in the FAP-positive SK-Mel-187 melanoma xenograft in vitro while accumulation was negligible in an NCI-H69 xenograft with low FAP levels. Binding of the tracer to endarterectomized tissue was similar in plaques and normal arteries, hampering its use for atherosclerosis imaging. PMID:25633335

  10. Experimental and DFT studies on the vibrational spectra of 1H-indene-2-boronic acid

    NASA Astrophysics Data System (ADS)

    Alver, Özgur; Kaya, Mehmet Fatih

    2014-11-01

    Stable conformers and geometrical molecular structures of 1H-indene-2-boronic acid (I-2B(OH)2) were studied experimentally and theoretically using FT-IR and FT-Raman spectroscopic methods. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm-1, and 3700-400 cm-1, respectively. The optimized geometric structures were searched by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-31++G(d,p) basis set. Vibrational wavenumbers of I-2B(OH)2 were calculated using B3LYP density functional methods including 6-31++G(d,p) basis set. Experimental and theoretical results show that density functional B3LYP method gives satisfactory results for predicting vibrational wavenumbers except OH stretching modes which is probably due to increasing unharmonicity in the high wave number region and possible intra and inter molecular interaction at OH edges. To support the assigned vibrational wavenumbers, the potential energy distribution (PED) values were also calculated using VEDA 4 (Vibrational Energy Distribution Analysis) program.

  11. Boronic Acid-Appended Molecular Glues for ATP-Responsive Activity Modulation of Enzymes.

    PubMed

    Okuro, Kou; Sasaki, Mizuki; Aida, Takuzo

    2016-05-01

    Water-soluble linear polymers GumBAn (m/n = 18/6, 12/12, and 6/18) with multiple guanidinium ion (Gu(+)) and boronic acid (BA) pendants in their side chains were synthesized as ATP-responsive modulators for enzyme activity. GumBAn polymers strongly bind to the phosphate ion (PO4(-)) and 1,2-diol units of ATP via the Gu(+) and BA pendants, respectively. As only the Gu(+) pendants can be used for proteins, GumBAn is able to modulate the activity of enzymes in response to ATP. As a proof-of-concept study, we demonstrated that trypsin (Trp) can be deactivated by hybridization with GumBAn. However, upon addition of ATP, Trp was liberated to retrieve its hydrolytic activity due to a higher preference of GumBAn toward ATP than Trp. This event occurred in a much lower range of [ATP] than reported examples. Under cellular conditions, the hydrolytic activity of Trp was likewise modulated. PMID:27087468

  12. Boron-containing acids: preliminary evaluation of acute toxicity and access to the brain determined by Raman scattering spectroscopy.

    PubMed

    Soriano-Ursúa, Marvin A; Farfán-García, Eunice D; López-Cabrera, Yessica; Querejeta, Enrique; Trujillo-Ferrara, José G

    2014-01-01

    Boron-containing compounds (BCCs), particularly boron containing acids (BCAs), have become attractive moieties or molecules in drug development. It has been suggested that when functional groups with boron atoms are added to well-known drugs, the latter are conferred with greater potency and efficacy in relation to their target receptors. However, the use of BCAs in drug development is limited due to the lack of a toxicological profile. Consequently, the aim of the present study was to evaluate the acute toxicity of boric and boronic acids. Thus, a determination was made of the lethal dose (LD50) of test compounds in male CD1 mice, as well as the effective dose required to negatively affect spontaneous motor activity and to produce notable behavioral abnormalities. After treatment of animals at different doses, macroscopic observations were made from a necropsy, and Raman scattering spectroscopic studies were carried out on brain tissue samples. In general, the results show that most of the tested BCAs have very low toxicity, evidenced by the high doses required to induce notable toxic effects (greater than 100 mg/kg of body weight for all compounds, except for 3-thyenilboronic acid). Such toxic effects, presumably mediated by action on the CNS, include eye damage, gastrointestinal effects (e.g., gastric-gut dilatation and fecal retention), sedation, hypnosis and/or trembling. This preliminary toxicological profile suggests that BCAs can be considered potential therapeutic agents or moieties to be added to other compounds in the development of new drugs. Future studies are required to explore possible chronic toxicity of BCCs. PMID:24189445

  13. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, Cressie E.; Morrow, Marvin S.

    1993-01-01

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  14. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  15. Reversible Bacterial Adhesion on Mixed Poly(dimethylaminoethyl methacrylate)/Poly(acrylamidophenyl boronic acid) Brush Surfaces.

    PubMed

    Xiong, Xinhong; Wu, Zhaoqiang; Yu, Qian; Xue, Lulu; Du, Jun; Chen, Hong

    2015-11-10

    A simple and versatile method for the preparation of surfaces to control bacterial adhesion is described. Substrates were first treated with two catechol-based polymerization initiators, one for thermal initiation and one for visible-light photoinitiation. Graft polymerization in sequence of dimethylaminoethyl methacrylate (DMAEMA) and 3-acrylamidebenzene boronic acid (BA) from the surface-bound initiators to form mixed polymer brushes on the substrate was then carried out. The PDMAEMA grafts were thermally initiated and the PBA grafts were visible-light-photoinitiated. Gold, poly(vinyl chloride) (PVC), and poly(dimethylsiloxane) (PDMS) were used as model substrates. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and ellipsometry analysis confirmed the successful grafting of PDMAEMA/PBA mixed brushes. We demonstrated that the resulting surfaces showed charge-reversal properties in response to change of pH. The transition in surface charge at a specific pH allowed the surface to be reversibly switched from bacteria-adhesive to bacteria-resistant. At pH 4.5, below the isoelectric points (IEP, pH 5.3) of the mixed brushes, the surfaces are positively charged and the negatively charged Gram-positive S. aureus adheres at high density (2.6 × 10(6) cells/cm(2)) due to attractive electrostatic interactions. Subsequently, upon increasing the pH to 9.0 to give negatively charged polymer brush surface, ∼90% of the adherent bacteria are released from the surface, presumably due to repulsive electrostatic interactions. This approach provides a simple method for the preparation of surfaces on which bacterial adhesion can be controlled and is applicable to a wide variety of substrates. PMID:26509287

  16. Kinetics of the electrochemical mineralization of perfluorooctanoic acid on ultrananocrystalline boron doped conductive diamond electrodes.

    PubMed

    Urtiaga, Ane; Fernández-González, Carolina; Gómez-Lavín, Sonia; Ortiz, Inmaculada

    2015-06-01

    This work deals with the electrochemical degradation and mineralization of perfluorooctanoic acid (PFOA). Model aqueous solutions of PFOA (100mg/L) were electro-oxidized under galvanostatic conditions in a flow-by undivided cell provided with a tungsten cathode and an anode formed by a commercial ultrananocrystalline boron doped diamond (BDD) coating on a niobium substrate. A systematic experimental study was conducted in order to analyze the influence of the following operation variables: (i) the supporting electrolyte, NaClO4 (1.4 and 8.4g/L) and Na2SO4 (5g/L); (ii) the applied current density, japp, in the range 50-200 A/m(2) and (iii) the hydrodynamic conditions, in terms of flowrate in the range 0.4×10(-4)-1.7×10(-4)m(3)/s and temperature in the range 293-313K. After 6h of treatment and at japp 200A/m(2), PFOA removal was higher than 93% and the mineralization ratio, obtained from the decrease of the total organic carbon (TOC) was 95%. The electrochemical generation of hydroxyl radicals in the supporting electrolyte was experimentally measured based on their reaction with dimethyl sulfoxide. The enhanced formation of hydroxyl radicals at higher japp was related to the faster kinetics of PFOA removal. The fitting of experimental data to the proposed kinetic model provided the first order rate constants of PFOA degradation, kc(1) that moved from 2.06×10(-4) to 15.58×10(-4)s(-1), when japp varied from 50 to 200A/m(2). PMID:24981910

  17. Innovative method for boron extraction from iron ore containing boron

    NASA Astrophysics Data System (ADS)

    Wang, Guang; Wang, Jing-song; Yu, Xin-yun; Shen, Ying-feng; Zuo, Hai-bin; Xue, Qing-guo

    2016-03-01

    A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction behavior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be enriched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100°C, the slag crystallized well and the efficiency of extraction of boron (EEB) of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled boron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40°C, and liquid-to-solid ratio of 8 mL/g.

  18. Electrochemical sensor for dopamine based on imprinted silica matrix-poly(aniline boronic acid) hybrid as recognition element.

    PubMed

    Li, Jian; Zhang, Ning; Sun, Qingqing; Bai, Zhanming; Zheng, Jianbin

    2016-10-01

    A novel imprinted silica matrix-poly(aniline boronic acid) hybrid for electrochemical detection of dopamine (DA) was developed. Boronic acid functionalized conducting polymer was electrochemically prepared on Au electrode. The number of covalent binding sites toward DA templates was controlled by potential cycles. A precursory sol solution of ammonium fluorosilicate (as cross-linking monomer) containing DA was spin-coated on the polymer modified electrode. Under NH3 atmosphere, the hydroxyl ions were generated in the solution and catalyzed the hydrolysis of fluorosilicate to form silica matrix. After this aqueous sol-gel process, an inorganic framework around the DA template was formed and the imprinted hybrid for DA was also produced. As revealed by scanning electron microscopy, UV-vis spectroscopy and cyclic voltammetry characterization, DA was embedded in the imprinted hybrid successfully. The affinity and selectivity of the imprinted hybrid were also characterized by cyclic voltammetry. The imprinted hybrid showed higher affinity for DA than that for epinephrine, and little or no affinity for ascorbic acid and uric acid due to the combined effects of covalent interaction, cavities matching and electrostatic repulsion. The imprinted hybrid sensor exhibited a quick response (within 5min) to DA in the concentration range from 0.05 to 500μmolL(-1) with a detection limit of 0.018μmolL(-1). The prepared sensor was also applied to detect DA in real samples with a satisfactory result. PMID:27474321

  19. Boronic acid fluorescent sensors for monosaccharide signaling based on the 6-methoxyquinolinium heterocyclic nucleus: progress toward noninvasive and continuous glucose monitoring.

    PubMed

    Badugu, Ramachandram; Lakowicz, Joseph R; Geddes, Chris D

    2005-01-01

    The synthesis, characterization, and spectral properties of strategically designed boronic acid containing fluorescent sensors, o-, m-, p-BMOQBA, for the potential detection of tear glucose concentrations when immobilized in plastic disposable contact lenses is described. The new probes, BMOQBAs, consist of the 6-methoxyquinolinium nucleus as a fluorescent indicator, and the boronic acid moiety as a glucose chelating group. A control compound BMOQ, which has no boronic acid group and therefore does not bind monosaccharides has also been prepared. In this paper, we show that structural design considerations of the new probes have afforded for their compatibility within the lenses, with reduced probe sugar-bound pK(a) favorable with the mildly acidic lens environment. In addition, the new probes are readily water soluble, have high quantum yields, and can be prepared by a simple one-step synthetic procedure. PMID:15582456

  20. Respiratory irritation associated with inhalation of boron trifluoride and fluorosulfonic acid.

    PubMed

    Rusch, George M; Bowden, Anthony M; Muijser, Hans; Arts, Josje

    2008-05-01

    The objectives of this study were to examine the respiratory irritancy of boron trifluoride (BF(3)) and fluorosulfonic acid (FSA) following acute inhalation exposure. Testing was conducted using groups of 10 male and 10 female rats (BF(3)) or groups of 6 male rats (FSA). Rats were exposed for a single 4-h period (BF(3)) or a single 1-h period (FSA) and necropsied 1 or 14 days after exposure (BF(3)) or 14 days after exposure (FSA). Measurements consisted of clinical signs, body weight, kidney and lung weight, histopathology (BF(3)), and breathing parameters (FSA) and were used to evaluate the possible irritating effects of these compounds. The results indicated treatment-related findings in the larynx and trachea in the rats exposed to 74.4 mg/m(3) BF(3), consisting of ventral cartilage necrosis, hemorrhage, and an increase in ventral epithelial hyperplasia and ventral inflammatory cell inflammation 24 h postexposure. In the animals sacrificed 14 days postexposure, the only notable observation was ventral cartilage necrosis, present in 2 animals. The next lower level tested, 24.6 mg/m(3) BF, was considered a no-observed-adverse-effects level (NOAEL). A concentration of 4125 mg/m(3) FSA resulted in a clearly decreased breathing rate during and shortly after exposure with 67% (4/6) mortality on days 5-9 after exposure. A concentration of 845 mg/m(3) FSA resulted in only minor signs of irritation, consisting of slight changes in breathing pattern shorlty after exposure. The results of the present 4-h inhalation study with BF(3) indicated that respiratory irritation was present at a level of 74.4 mg/m(3) whereas 24.6 mg/m(3) was a NOAEL. A single 1-h exposure to 845 mg/m(3) FSA resulted in only minor signs of respiratory irritation, indicating that on a mass basis FSA is no more toxic or irritating than hydrogen fluoride (HF) or sulfuric acid. PMID:18464054

  1. Palladium-Catalyzed Defluorinative Coupling of 1-Aryl-2,2-Difluoroalkenes and Boronic Acids: Stereoselective Synthesis of Monofluorostilbenes.

    PubMed

    Thornbury, Richard T; Toste, F Dean

    2016-09-12

    The palladium-catalyzed defluorinative coupling of 1-aryl-2,2-difluoroalkenes with boronic acids is described. Broad functional-group tolerance arises from a redox-neutral process by a palladium(II) active species which is proposed to undergo a β-fluoride elimination to afford the products. The monofluorostilbene products were formed with excellent diastereoselectivity (≥50:1) in all cases, and it is critical, as traditional chromatographic techniques often fail to separate monofluoroalkene isomers. As a demonstration of this method's unique combination of reactivity and functional-group tolerance, a Gleevec® analogue, using a monofluorostilbene as an amide isostere, was synthesized. PMID:27511868

  2. Characterization and in vitro activity of a branched peptide boronic acid that interacts with HIV-1 RRE RNA.

    PubMed

    Wynn, Jessica E; Zhang, Wenyu; Tebit, Denis M; Gray, Laurie R; Hammarskjold, Marie-Louise; Rekosh, David; Santos, Webster L

    2016-09-01

    A branched peptide containing multiple boronic acids was found to bind RRE IIB selectively and inhibit HIV-1 p24 capsid production in a dose-dependent manner. Structure-activity relationship studies revealed that branching in the peptide is crucial for the low micromolar binding towards RRE IIB, and the peptide demonstrates selectivity towards RRE IIB in the presence of tRNA. Footprinting studies suggest a binding site on the upper stem and internal loop regions of the RNA, which induces enzymatic cleavage of the internal loops of RRE IIB upon binding. PMID:27091070

  3. Palladium-Catalyzed Oxidative Sulfenylation of Indoles and Related Electron-Rich Heteroarenes with Aryl Boronic Acids and Elemental Sulfur.

    PubMed

    Li, Jianxiao; Li, Chunsheng; Yang, Shaorong; An, Yanni; Wu, Wanqing; Jiang, Huanfeng

    2016-09-01

    An efficient and convenient palladium-catalyzed C-H bond oxidative sulfenylation of indoles and related electron-rich heteroarenes with aryl boronic acids and elemental sulfur has been described. This procedure provides a useful and direct approach for the assembly of a wide range of structurally diverse 3-sulfenylheteroarenes with moderate to excellent yields from simple and readily available starting materials. Moreover, this synthetic protocol is suitable for N-protected and unprotected indoles. Notably, the construction of two C-S bonds in one step was also achieved in this transformation. PMID:27500941

  4. Ru-Catalysed C–H Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies

    PubMed Central

    Sollert, Carina; Devaraj, Karthik; Orthaber, Andreas; Gates, Paul J; Pilarski, Lukasz T

    2015-01-01

    The Ru-catalysed C2–H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole-based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on-cycle intermediates do not possess a para-cymene ligand and that the on-cycle metalation occurs through an electrophilic attack by the Ru centre. PMID:25689052

  5. Boron-Based Drug Design.

    PubMed

    Ban, Hyun Seung; Nakamura, Hiroyuki

    2015-06-01

    The use of the element boron, which is not generally observed in a living body, possesses a high potential for the discovery of new biological activity in pharmaceutical drug design. In this account, we describe our recent developments in boron-based drug design, including boronic acid containing protein tyrosine kinase inhibitors, proteasome inhibitors, and tubulin polymerization inhibitors, and ortho-carborane-containing proteasome activators, hypoxia-inducible factor 1 inhibitors, and topoisomerase inhibitors. Furthermore, we applied a closo-dodecaborate as a water-soluble moiety as well as a boron-10 source for the design of boron carriers in boron neutron capture therapy, such as boronated porphyrins and boron lipids for a liposomal boron delivery system. PMID:25800654

  6. Inhibition of IgA1 proteinases from Neisseria gonorrhoeae and Hemophilus influenzae by peptide prolyl boronic acids.

    PubMed

    Bachovchin, W W; Plaut, A G; Flentke, G R; Lynch, M; Kettner, C A

    1990-03-01

    The alpha-aminoboronic acid analog of proline has been synthesized and incorporated into a number of peptides as the COOH-terminal residue. These peptide prolyl boronic acids are potent inhibitors of both the type 1 and type 2 IgA proteinases from Neisseria gonorrhoeae and Hemophilus influenzae, but not of the functionally similar IgA proteinase from Streptococcus sanguis. The best inhibitors synthesized thus far have Ki values in the nanomolar range (4.0 to 60 nM). These results indicate that the N. gonorrhoeae and the H. influenzae enzymes belong to the serine protease family of proteolytic enzymes while that from S. sanguis does not. As a group, the IgA proteinases have been noted for their remarkable specificity; thus, the peptide prolyl boronic acids reported here are the first small synthetic molecules to exhibit a relatively high affinity for the active site of an IgA proteinase and are therefore the first to yield some insight into the active site structure and specificity requirements of these enzymes. PMID:2105953

  7. Boronic acid-functionalized core-shell-shell magnetic composite microspheres for the selective enrichment of glycoprotein.

    PubMed

    Pan, Miaorong; Sun, Yangfei; Zheng, Jin; Yang, Wuli

    2013-09-11

    In this work, core-shell-shell-structured boronic acid-functionalized magnetic composite microspheres Fe3O4@SiO2@poly (methyl methacrylate-co-4-vinylphenylbornoic acid) (Fe3O4@SiO2@P(MMA-co-VPBA)) with a uniform size and fine morphology were synthesized. Here, Fe3O4 magnetic particles were prepared by a solvothermal reaction, whereas the Fe3O4@SiO2 microspheres with a core-shell structure were obtained by a sol-gel process. 3-(Trimethoxysilyl) propyl methacrylate (MPS)-modified Fe3O4@SiO2 was used as the seed in the emulsion polymerization of MMA and VPBA to form the core-shell-shell-structured magnetic composite microspheres. As the boronic acid groups on the surface of Fe3O4@SiO2@P(MMA-co-VPBA) could form tight yet reversible covalent bonds with the cis-1,2-diols groups of glycoproteins, the magnetic composite microspheres were applied to enrich a standard glycoprotein, horseradish peroxidase (HRP), and the results demonstrated that the composite microspheres have a higher affinity for the glycoproteins in the presence of the nonglycoprotein bovine serum albumin (BSA) over HRP. Additionally, different monomer mole ratios of MMA/VPBA were studied, and the results implied that using MMA as the major monomer could reduce the amount of VPBA with a similar glycoprotein enrichment efficiency but a lower cost. PMID:23924282

  8. Development of Sensitive Analytical Approach for the Quantification of α-Lipoic Acid Using Boron Doped Diamond Electrode.

    PubMed

    Stankovic, Dalibor M; Mehmeti, Eda; Kalcher, Kurt

    2016-01-01

    A boron doped diamond (BDD) electrode was investigated for use as an electrochemical sensor for α-lipoic acid (LA) using amperometric and differential pulse voltammetric detection. LA displays a well expressed oxidation peak at +0.9 V vs. Ag/AgCl in solutions with a pH value of 3. It was found that signals obtained are linearly related to the concentration range from 0.3 to 105 μM with detection limit of 0.088 μM. Interferences by common compounds such as ascorbic acid, uric acid and dopamine were tested and the method was successfully applied to the determination of LA in human body fluids where it gave recoveries in the range from 95 to 97%. PMID:27506710

  9. A universal procedure for the [¹⁸F]trifluoromethylation of aryl iodides and aryl boronic acids with highly improved specific activity.

    PubMed

    van der Born, Dion; Sewing, Claudia; Herscheid, J Koos D M; Windhorst, Albert D; Orru, Romano V A; Vugts, Danielle J

    2014-10-01

    Herein, we describe a valuable method for the introduction of the [(18)F]CF3 group into arenes with highly improved specific activity by the reaction of [(18)F]trifluoromethane with aryl iodides or aryl boronic acids. This [(18)F]trifluoromethylation reaction is the first to be described in which the [(18)F]CF3 products are generated in actual trace amounts and can therefore effectively be used as PET tracers. The method shows broad scope with respect to possible aryl iodide and aryl boronic acid substrates, as well as good to excellent conversion. In particular, the [(18)F]trifluoromethylation of boronic acids was found to outperform [(18)F]trifluoromethylation reactions of halogenated aryl precursors with regard to conversion, reaction conditions, and kinetics. PMID:25155042

  10. Palladium(II)‐Catalyzed Synthesis of Sulfinates from Boronic Acids and DABSO: A Redox‐Neutral, Phosphine‐Free Transformation

    PubMed Central

    Deeming, Alex S.; Russell, Claire J.

    2015-01-01

    Abstract A redox‐neutral palladium(II)‐catalyzed conversion of aryl, heteroaryl, and alkenyl boronic acids into sulfinate intermediates, and onwards to sulfones and sulfonamides, has been realized. A simple Pd(OAc)2 catalyst, in combination with the sulfur dioxide surrogate 1,4‐diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO), is sufficient to achieve rapid and high‐yielding conversion of the boronic acids into the corresponding sulfinates. Addition of C‐ or N‐based electrophiles then allows conversion into sulfones and sulfonamides, respectively, in a one‐pot, two‐step process. PMID:26596861

  11. Boronic Acid: A Bio-Inspired Strategy To Increase the Sensitivity and Selectivity of Fluorescent NADH Probe.

    PubMed

    Wang, Lu; Zhang, Jingye; Kim, Beomsue; Peng, Juanjuan; Berry, Stuart N; Ni, Yong; Su, Dongdong; Lee, Jungyeol; Yuan, Lin; Chang, Young-Tae

    2016-08-24

    Fluorescent probes have emerged as an essential tool in the molecular recognition events in biological systems; however, due to the complex structures of certain biomolecules, it remains a challenge to design small-molecule fluorescent probes with high sensitivity and selectivity. Inspired by the enzyme-catalyzed reaction between biomolecule and probe, we present a novel combination-reaction two-step sensing strategy to improve sensitivity and selectivity. Based on this strategy, we successfully prepared a turn-on fluorescent reduced nicotinamide adenine dinucleotide (NADH) probe, in which boronic acid was introduced to bind with NADH and subsequently accelerate the sensing process. This probe shows remarkably improved sensitivity (detection limit: 0.084 μM) and selectivity to NADH in the absence of any enzymes. In order to improve the practicality, the boronic acid was further modified to change the measurement conditions from alkalescent (pH 9.5) to physiological environment (pH 7.4). Utilizing these probes, we not only accurately quantified the NADH weight in a health care product but also evaluated intracellular NADH levels in live cell imaging. Thus, these bio-inspired fluorescent probes offer excellent tools for elucidating the roles of NADH in biological systems as well as a practical strategy to develop future sensitive and selective probes for complicated biomolecules. PMID:27500425

  12. Discovery of 2-[5-(4-Fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic Acid (SX-517): Noncompetitive Boronic Acid Antagonist of CXCR1 and CXCR2

    PubMed Central

    2015-01-01

    The G protein-coupled chemokine receptors CXCR1 and CXCR2 play key roles in inflammatory diseases and carcinogenesis. In inflammation, they activate and recruit polymorphonuclear cells (PMNs) through binding of the chemokines CXCL1 (CXCR1) and CXCL8 (CXCR1 and CXCR2). Structure–activity studies that examined the effect of a novel series of S-substituted 6-mercapto-N-phenyl-nicotinamides on CXCL1-stimulated Ca2+ flux in whole human PMNs led to the discovery of 2-[5-(4-fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic acid (SX-517), a potent noncompetitive boronic acid CXCR1/2 antagonist. SX-517 inhibited CXCL1-induced Ca2+ flux (IC50 = 38 nM) in human PMNs but had no effect on the Ca2+ flux induced by C5a, fMLF, or PAF. In recombinant HEK293 cells that stably expressed CXCR2, SX-517 antagonized CXCL8-induced [35S]GTPγS binding (IC50 = 60 nM) and ERK1/2 phosphorylation. Inhibition was noncompetitive, with SX-517 unable to compete the binding of [125I]-CXCL8 to CXCR2 membranes. SX-517 (0.2 mg/kg iv) significantly inhibited inflammation in an in vivo murine model. SX-517 is the first reported boronic acid chemokine antagonist and represents a novel pharmacophore for CXCR1/2 antagonism. PMID:25254640

  13. Silicone boronates reversibly crosslink using Lewis acid-Lewis base amine complexes.

    PubMed

    Dodge, Laura; Chen, Yunqing; Brook, Michael A

    2014-07-21

    Silicone elastomers are normally thermosets, which are not readily recycled or repurposed. The few examples of thermoplastic silicone elastomers depend on reversible covalent and non-covalent molecular interactions. It is demonstrated that amine-boronate complex formation provides a simple and flexible route to reversible crosslinked silicones. A variety of network structures were prepared by use of terminal and pendantly functionalised silicone boronates and amines. The crosslink density was quantified using a combination of Shore-hardness measurements, swelling, and rheological analyses. Stress induced by compressive force could be relieved through dynamic B-N bond reformation at 60 °C. Materials could be fully disassembled through introduction of n-butylamine and successfully reformed upon removal of the monofunctional amine by evaporation. PMID:24986574

  14. Voltammetric study of the boric acid-salicylaldehyde-H-acid ternary system and its application to the voltammetric determination of boron.

    PubMed

    Kajiwara, Mari; Ito, Yoshio N; Miyazaki, Yoshinobu; Fujimori, Takao; Takehara, Kô; Yoshimura, Kazuhisa

    2015-02-14

    The ternary system of boric acid, salicylaldehyde (SA) and H-acid (HA) was voltammetrically studied from kinetic and equilibrium points of view. The effect of the SA substituents was also studied by using two analogs, 5-fluorosalicylaldehyde (F-SA) and 5-methylsalicylaldehyde (Me-SA). The three cathodic peaks of Azomethine H (AzH), Azomethine H-boric acid complex (AzB), and free SA were observed in the solution containing boric acid, SA and HA. The peak potentials of AzH and SA were shifted to negative potentials with increasing pH, while the peak potential of AzB was pH-independent. This difference indicates that a proton participates in the charge-transfer steps of the AzH and SA reductions, but not in that of the AzB reduction. The formation constants for the AzB complexation were similar among all the examined analogs. In the kinetic study, the reaction rate was higher in an acidic condition for the AzH formation, but in a neutral condition for the AzB formation. The rate constants for the AzB complexes were in the order of F-SA > SA ≈ Me-SA, indicating that the fluoro group accelerates the F-AzB complexation. The AzB complexation mechanism is considered to consist of more than three steps, i.e., the pre-equilibrium of the salicylaldehyde-boric acid complex (SA-B) formation, the nucleophilic attack of HA on SA-B, and the remaining some steps to form AzB. Based on these results, the voltammetric determination method of boron using F-SA was optimized, which allowed the boron concentration to be determined within only 5 min with a 0.03 mg B dm(-3) detection limit. PMID:25584642

  15. Tribological properties of boric acid and boric-acid-forming surfaces: Part 2, Formation and self-lubrication mechanisms of boric acid films on boron- and boric-oxide-containing surfaces

    SciTech Connect

    Erdemir, A.; Fenske, G.R.; Erck, R.A.; Nichols, F.A.; Busch, D.

    1990-01-01

    This paper describes the formation and self-lubricating mechanisms of boric acid films on boron- and boric oxide-containing surfaces. As reported in part I, boric acid, owing to a layered triclinic crystal structure and weak interlayer bonds, enjoys an unusual lubrication capability. RF-magnetron sputtering and vacuum evaporation techniques were used to produce thin coatings of boron and boric oxides on steel substrates. The results of tribological experiments indicate that the room temperature friction coefficient of tribosystems that include boron and/or boric oxide coatings ranges from 0.05 to 0.07, depending on the coating type. Laser-Raman spectroscopy of these surfaces revealed that this low friction is associated with a thin boric acid film that forms on the surfaces of these coatings. The fabrication and potential importance of boric acid and boric acid-forming surfaces for practical applications are enumerated. Surface engineering of tribomaterials, such as these demonstrated in this paper, is suggested as a new lubrication concept for use in present and future tribological industries. 16 refs.

  16. Thermodynamic Analysis of the Selectivity Enhancement Obtained by Using Smart Hydrogels That Are Zwitterionic When Detecting Glucose With Boronic Acid Moieties

    PubMed Central

    Horkay, F.; Cho, S. H.; Tathireddy, P.; Rieth, L.; Solzbacher, F.; Magda, J.

    2011-01-01

    Because the boronic acid moiety reversibly binds to sugar molecules and has low cytotoxicity, boronic acid-containing hydrogels are being used in a variety of implantable glucose sensors under development, including sensors based on optical, fluorescence, and swelling pressure measurements. However, some method of glucose selectivity enhancement is often necessary, because isolated boronic acid molecules have a binding constant with glucose that is some forty times smaller than their binding constant with fructose, the second most abundant sugar in the human body. In many cases, glucose selectivity enhancement is obtained by incorporating pendant tertiary amines into the hydrogel network, thereby giving rise to a hydrogel that is zwitterionic at physiological pH. However, the mechanism by which incorporation of tertiary amines confers selectivity enhancement is poorly understood. In order to clarify this mechanism, we use the osmotic deswelling technique to compare the thermodynamic interactions of glucose and fructose with a zwitterionic smart hydrogel containing boronic acid moieties. We also investigate the change in the structure of the hydrogel that occurs when it binds to glucose or to fructose using the technique of small angle neutron scattering. PMID:22190765

  17. Identification of serine and histidine adducts in complexes of trypsin and trypsinogen with peptide and nonpeptide boronic acid inhibitors by 1H NMR spectroscopy.

    PubMed

    Tsilikounas, E; Kettner, C A; Bachovchin, W W

    1992-12-29

    We have previously shown, in 15N NMR studies of the enzyme's active site histidine residue, that boronic acid inhibitors can form two distinct types of complexes with alpha-lytic protease. Inhibitors that are structural analogs of good alpha-lytic protease substrates form transition-state-like tetrahedral complexes with the active site serine whereas those that are not form complexes in which N epsilon 2 of the active site histidine is covalently bonded to the boron of the inhibitor. This study also demonstrated that the serine and histidine adduct complexes exhibit quite distinctive and characteristic low-field 1H NMR spectra [Bachovchin, W. W., Wong, W. Y. L., Farr-Jones, S., Shenvi, A. B., & Kettner, C. A. (1988) Biochemistry 27, 7689-7697]. Here we have used low-field 1H NMR diagnostically for a series of boronic acid inhibitor complexes of trypsin and trypsinogen. The results show that H-D-Val-Leu-boroArg and Ac-Gly-boroArg, analogs of good trypsin substrates, form transition-state-like serine adducts with trypsin, whereas the nonsubstrate analog inhibitors boric acid, methane boronic acid, butane boronic acid, and triethanolamine borate all form histidine adducts, thereby paralleling the previous results obtained with alpha-lytic protease. However, with trypsinogen, Ac-Gly-boroArg forms predominantly a histidine adduct while H-D-Val-Leu-boroArg forms both histidine and serine adducts, with the histidine adduct predominating below pH 8.0 and the serine adduct predominating above pH 8.0.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1463754

  18. Boronic acid-modified lipid nanocapsules: a novel platform for the highly efficient inhibition of hepatitis C viral entry

    NASA Astrophysics Data System (ADS)

    Khanal, Manakamana; Barras, Alexandre; Vausselin, Thibaut; Fénéant, Lucie; Boukherroub, Rabah; Siriwardena, Aloysius; Dubuisson, Jean; Szunerits, Sabine

    2015-01-01

    The search for viral entry inhibitors that selectively target viral envelope glycoproteins has attracted increasing interest in recent years. Amongst the handful of molecules reported to show activity as hepatitis C virus (HCV) entry inhibitors are a variety of glycan-binding proteins including the lectins, cyanovirin-N (CV-N) and griffithsin. We recently demonstrated that boronic acid-modified nanoparticles are able to reduce HCV entry through a similar mechanism to that of lectins. A major obstacle to any further development of these nanostructures as viral entry inhibitors is their only moderate maximal inhibition potential. In the present study, we report that lipid nanocapsules (LNCs), surface-functionalized with amphiphilic boronic acid (BA) through their post-insertion into the semi-rigid shell of the LNCs, are indeed far superior as HCV entry inhibitors when compared with previously reported nanostructures. These 2nd generation particles (BA-LNCs) are shown to prevent HCV infection in the micromolar range (IC50 = 5.4 μM of BA moieties), whereas the corresponding BA monomers show no significant effects even at the highest analyzed concentration (20 μM). The new BA-LNCs are the most promising boronolectin-based HCV entry inhibitors reported to date and are thus observed to show great promise in the development of a pseudolectin-based therapeutic agent.The search for viral entry inhibitors that selectively target viral envelope glycoproteins has attracted increasing interest in recent years. Amongst the handful of molecules reported to show activity as hepatitis C virus (HCV) entry inhibitors are a variety of glycan-binding proteins including the lectins, cyanovirin-N (CV-N) and griffithsin. We recently demonstrated that boronic acid-modified nanoparticles are able to reduce HCV entry through a similar mechanism to that of lectins. A major obstacle to any further development of these nanostructures as viral entry inhibitors is their only moderate maximal

  19. Voltammetric determination of mixtures of caffeine and chlorogenic acid in beverage samples using a boron-doped diamond electrode.

    PubMed

    Yardım, Yavuz; Keskin, Ertugrul; Şentürk, Zühre

    2013-11-15

    Herein, a boron-doped diamond (BDD) electrode that is anodically pretreated was used for the simultaneous determination of caffeine (CAF) and chlorogenic acid (CGA) by cyclic and adsorptive stripping voltammetry. The dependence of peak current and potential on pH, scan rate, accumulation parameters and other experimental variables were studied. By using square-wave stripping mode after 60 s accumulation under open-circuit voltage, the BDD electrode was able to separate the oxidation peak potentials of CAF and CGA present in binary mixtures by about 0.4V in Britton-Robinson buffer at pH 1.0. The limits of detection were 0.107 µg mL(-1) (5.51×10(-7) M) for CAF, and 0.448 µg mL(-1) (1.26×10(-6) M) for CGA. The practical applicability of this methodology was tested in commercially available beverage samples. PMID:24148509

  20. Spectroscopic studies on 9H-carbazole-9-(4-phenyl) boronic acid pinacol ester by DFT method

    NASA Astrophysics Data System (ADS)

    Sas, E. B.; Kurt, M.; Can, M.; Horzum, N.; Atac, A.

    2016-08-01

    9H-Carbazole-9-(4-phenyl) boronic acid pinacol ester (9-CPBAPE) molecule was investigated by FT-IR, Raman, UV-vis, 1H and 13C NMR spectra. FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. 1H, 13C NMR and UV-vis spectra were recorded in dimethyl sulfoxide (DMSO) solution. The results of theoretical calculations for the spectra of the title molecule were compared with the experimental spectra. The highest occupied molecular orbital (HOMO) the lowest unoccupied molecular orbital (LUMO) and molecular electrostatic potential (MEP) analyses were performed. The theoretical calculations for the molecular structure and spectroscopic studies were performed with DFT (B3LYP) and 6-311G (d,p) basis set calculations using the Gaussian 09 program. The total (TDOS), partial (PDOS) density of state and overlap population density of state (OPDOS) diagrams analyses were performed using GaussSum 2.2 program.

  1. Chemometric study on the electrochemical incineration of nitrilotriacetic acid using platinum and boron-doped diamond anode.

    PubMed

    Zhang, Chunyong; He, Zhenzhu; Wu, Jingyu; Fu, Degang

    2015-07-01

    This study investigated the electrochemical incineration of nitrilotriacetic acid (NTA) at boron-doped diamond (BDD) and platinum (Pt) anodes. Trials were performed in the presence of sulfate electrolyte media under recirculation mode. The parameters that influence the degradation efficiency were investigated, including applied current density, flow rate, supporting electrolyte concentration and reaction time. To reduce the number of experiments, the system had been managed under chemometric technique named Doehlert matrix. As a consequence, the mineralization of NTA demonstrated similar behavior upon operating parameters on these two anodes. Further kinetic study indicated that the degradations followed pseudo-first-order reactions for both BDD and Pt anodes, and the reaction rate constant of the former was found to be higher than that of the latter. Such difference could be interpreted by results from fractal analysis. In addition, a reaction sequence for NTA mineralization considering all the detected intermediates was also proposed. PMID:25747300

  2. Carbohydrate-interactive pDNA and siRNA gene vectors based on boronic acid functionalized poly(amido amine)s.

    PubMed

    Piest, Martin; Ankoné, Marc; Engbersen, Johan F J

    2013-08-10

    In order to evaluate the influence of incorporation of boronic acid groups on the properties of poly(amido amine)s as gene vectors, a novel poly(amido amine) copolymer p(CBA-ABOL/2AMPBA) containing ortho-aminomethylphenylboronic acid (2AMPBA) moieties was prepared by Michael-type polyaddition of a mixture of 1,4-aminobutanol (ABOL) and 2-((4-aminobutylamino)methyl)phenyl boronic acid to N,N'-cystamine bisacrylamide (CBA). It appeared that the presence of the boronic acid moieties as side groups along the polymer chain strongly enhances the stability of the self-assembled nanoparticles and nanosized polyplexes formed from this polymer; no aggregation was observed after storage for 6days at 37°C. This strong stabilization can be attributed to intermolecular Lewis acid-base interactions between the 2AMPBA groups and the alcohol and amine groups present in the polymer, leading to dynamical (reversible) crosslinking in the nanoparticles. Moreover, since the boronic acids can reversibly form boronic esters with vicinal diol groups, the presence of the 2AMPBA groups add carbohydrate-interactive properties to these polymers that strongly influence their behavior as gene delivery vectors. DNA transfection with p(CBA-ABOL/2AMPBA) polyplexes gave transfection efficiencies that were approximately similar to commercial PEI in different cell lines (COS-7, HUH-6 and H1299-Fluc), but lower than those obtained with reference polyplexes from p(CBA-ABOL). It is hypothesized that the uptake of the boronated polyplexes is suppressed by binding to the glycocalyx of the cells. This is supported by the observation that addition of sorbitol or dextran to the transfection medium significantly enhances the transfection efficiency, which can be attributed to increased cellular uptake of the polyplexes due to boronic ester formation with these agents. AFM, SEM and confocal microscopy showed that polyplexes of p(CBA-ABOL/2AMPBA) become decorated with a dextran layer in the presence of 0.9% (w

  3. Efficient nuclear drug translocation and improved drug efficacy mediated by acidity-responsive boronate-linked dextran/cholesterol nanoassembly.

    PubMed

    Zhu, Jing-Yi; Lei, Qi; Yang, Bin; Jia, Hui-Zhen; Qiu, Wen-Xiu; Wang, Xuli; Zeng, Xuan; Zhuo, Ren-Xi; Feng, Jun; Zhang, Xian-Zheng

    2015-06-01

    The present study reported a lysosome-acidity-targeting bio-responsive nanovehicle self-assembled from dextran (Dex) and phenylboronic acid modified cholesterol (Chol-PBA), aiming at the nucleus-tropic drug delivery. The prominent advantage of this assembled nanoconstruction arose from its susceptibility to acidity-labile dissociation concurrently accompanied with the fast liberation of encapsulated drugs, leading to efficient nuclear drug translocation and consequently favorable drug efficacy. By elaborately exploiting NH4Cl pretreatment to interfere with the cellular endosomal acidification progression, this study clearly evidenced at a cellular level the strong lysosomal-acidity dependency of nuclear drug uptake efficiency, which was shown to be the main factor influencing the drug efficacy. The boronate-linked nanoassembly displayed nearly no cytotoxicity and can remain structural stability under the simulated physiological conditions including 10% serum and the normal blood sugar concentration. The cellular exposure to cholesterol was found to bate the cellular uptake of nanoassembly in a dose-dependent manner, suggesting a cholesterol-associated mechanism of the intracellular internalization. The in vivo antitumor assessment in xenograft mouse models revealed the significant superiority of DOX-loaded Dex/Chol-PBA nanoassembly over the controls including free DOX and the DOX-loaded non-sensitive Dex-Chol, as reflected by the more effective tumor-growth inhibition and the better systematic safety. In terms of the convenient preparation, sensitive response to lysosomal acidity and efficient nuclear drug translocation, Dex/Chol-PBA nanoassembly derived from natural materials shows promising potentials as the nanovehicle for nucleus-tropic drug delivery especially for antitumor agents. More attractively, this study offers a deeper insight into the mechanism concerning the contribution of acidity-responsive delivery to the enhanced chemotherapy performance. PMID

  4. Simultaneous Disulfide and Boronic Acid Ester Exchange in Dynamic Combinatorial Libraries

    PubMed Central

    Diemer, Sanna L.; Kristensen, Morten; Rasmussen, Brian; Beeren, Sophie R.; Pittelkow, Michael

    2015-01-01

    Dynamic combinatorial chemistry has emerged as a promising tool for the discovery of complex receptors in supramolecular chemistry. At the heart of dynamic combinatorial chemistry are the reversible reactions that enable the exchange of building blocks between library members in dynamic combinatorial libraries (DCLs) ensuring thermodynamic control over the system. If more than one reversible reaction operates in a single dynamic combinatorial library, the complexity of the system increases dramatically, and so does its possible applications. One can imagine two reversible reactions that operate simultaneously or two reversible reactions that operate independently. Both these scenarios have advantages and disadvantages. In this contribution, we show how disulfide exchange and boronic ester transesterification can function simultaneous in dynamic combinatorial libraries under appropriate conditions. We describe the detailed studies necessary to establish suitable reaction conditions and highlight the analytical techniques appropriate to study this type of system. PMID:26378519

  5. Simultaneous voltammetric determination of paracetamol and ascorbic acid using a boron-doped diamond electrode modified with Nafion and lead films.

    PubMed

    Tyszczuk-Rotko, Katarzyna; Bęczkowska, Ilona; Wójciak-Kosior, Magdalena; Sowa, Ireneusz

    2014-11-01

    The paper describes the fabrication and application of a novel sensor (a boron-doped diamond electrode modified with Nafion and lead films) for the simultaneous determination of paracetamol and ascorbic acid by differential pulse voltammetry. The main advantage of the lead film and polymer covered boron-doped diamond electrode is that the sensitivity of the stripping responses is increased and the separation of paracetamol and ascorbic acid signals is improved due to the modification of the boron-doped diamond surface by the lead layer. Additionally, the repeatability of paracetamol and ascorbic acid signals is improved by the application of the Nafion film coating. In the presence of oxygen, linear calibration curves were obtained in a wide concentration range from 5×10(-7) to 2×10(-4) mol L(-1) for paracetamol and from 1×10(-6) to 5×10(-4) mol L(-1) for ascorbic acid. The analytical utility of the differential pulse voltammetric method elaborated was tested in the assay of paracetamol and ascorbic acid in commercially available pharmaceutical formulations and the method was validated by high performance liquid chromatography coupled with diode array detector. PMID:25127609

  6. Site and chirality selective chemical modifications of boron nitride nanotubes (BNNTs) via Lewis acid-base interactions.

    PubMed

    Sundaram, Rajashabala; Scheiner, Steve; Roy, Ajit K; Kar, Tapas

    2015-02-01

    The pristine BNNTs contain both Lewis acid (boron) and Lewis base (nitrogen) centers at their surface. Interactions of ammonia and borane molecules, representatives of Lewis base and acid as adsorbates respectively, with matching sites at the surface of BNNTs, have been explored in the present DFT study. Adsorption energies suggest stronger chemisorption (about 15-20 kcal mol(-1)) of borane than ammonia (about 5-10 kcal mol(-1)) in both armchair (4,4) and zigzag (8,0) variants of the tube. NH3 favors (8,0) over the (4,4) tube, whereas BH3 exhibits the opposite preference, indicating some chirality dependence on acid-base interactions. A new feature of bonding is found in BH3/AlH3-BNNTs (at the edge site) complexes, where one hydrogen of the guest molecule is involved in three-center two-electron bonding, in addition to dative covalent bond (N: → B). This interaction causes a reversal of electron flow from borane/alane to BNNT, making the tube an electron acceptor, suggesting tailoring of electronic properties could be possible by varying strength of incoming Lewis acids. On the contrary, BNNTs always behave as electron acceptor in ammonia complexes. IR, XPS and NMR spectra show some characteristic features of complexes and can help experimentalists to identify not only structures of such complexes but also the location of the guest molecules and design second functionalizations. Interaction with several other neutral BF3, BCl3, BH2CH3 and ionic CH3(+) acids as well as amino group (CH3NH2 and NH2COOH) were also studied. The strongest interaction (>100 kcal mol(-1)) is found in BNNT-CH3(+) complexes and H-bonds are the only source of stability of NH2COOH-BNNT complexes. PMID:25559141

  7. Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F(-) Ions.

    PubMed

    Suresh, Venkata M; Bandyopadhyay, Arkamita; Roy, Syamantak; Pati, Swapan K; Maji, Tapas Kumar

    2015-07-20

    Reversible and selective capture/detection of F(-) ions in water is of the utmost importance, as excess intake leads to adverse effects on human health. Highly robust Lewis acidic luminescent porous organic materials have potential for efficient sequestration and detection of F(-) ions. Herein, the rational design and synthesis of a boron-based, Lewis acidic microporous organic polymer (BMOP) derived from tris(4-bromo-2,3,5,6-tetramethylphenyl)boron nodes and diethynylbiphenyl linkers with a pore size of 1.08 nm for selective turn-on sensing and capture of F(-) ion are reported. The presence of a vacant pπ orbital on the boron center of BMOP results in intramolecular charge transfer (ICT) from the linker to boron. BMOP shows selective turn-on blue emission for F(-) ions in aqueous mixtures with a detection limit of 2.6 μM. Strong B-F interactions facilitate rapid sequestration of F(-) by BMOP. The ICT emission of BMOP can be reversibly regenerated by addition of an excess of water, and the polymer can be reused several times. PMID:26074403

  8. Fluorescence sensors for monosaccharides based on the 6-methylquinolinium nucleus and boronic acid moiety: potential application to ophthalmic diagnostics

    PubMed Central

    Badugu, Ramachandram; Lakowicz, Joseph R.; Geddes, Chris D.

    2016-01-01

    Continuous monitoring of glucose levels in human physiology is important for the long-term management of diabetes. New signaling methods/probes may provide an improved technology to monitor glucose and other physiologically important analytes. The glucose sensing probes, BMQBAs, fabricated using the 6-methylquinolinium moiety as a fluorescent indicator, and boronic acid as a chelating group, may have versatile applications in glucose sensing because of their unique properties. In this paper we discuss the design logic, synthesis, characterization and spectral properties of three new isomeric glucose sensors (BMQBAs), and a control compound (BMQ) in the presence and absence of sugars. The sensing ability of the new probes is based on a charge neutralization and stabilization mechanism upon sugar binding. The new probes have attractive fluorescence quantum yields, are highly water-soluble, and have spectral characteristics compatible with cheap and portable LEDs and LDs. One of the probes, o-BMQBA, has a sugar bound pKa of 6.1, and a dissociation constant KD of 100 mM glucose. These probes have been designed specifically to respond to tear glucose in a contact lens polymer for ophthalmic glucose monitoring, where the reduced sugar bound pKa affords for sensing, in a lens environment that we have previously shown to be mildly acidic. PMID:18969865

  9. Palladium-catalyzed cross-coupling of sterically demanding boronic acids with α-bromocarbonyl compounds.

    PubMed

    Zimmermann, Bettina; Dzik, Wojciech I; Himmler, Thomas; Goossen, Lukas J

    2011-10-01

    A catalyst system generated in situ from Pd(dba)(2) and tri(o-tolyl)phosphine mediates the coupling of arylboronic acids with alkyl α-bromoacetates under formation of arylacetic acid esters at unprecedented low loadings. The new protocol, which involves potassium fluoride as the base and catalytic amounts of benzyltriethylammonium bromide as a phase transfer catalyst, is uniquely effective for the synthesis of sterically demanding arylacetic acid derivatives. PMID:21863787

  10. A boron phosphate-phosphoric acid composite membrane for medium temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Mamlouk, M.; Scott, K.

    2015-07-01

    A composite membrane based on a non-stoichiometric composition of BPO4 with excess of PO4 (BPOx) was synthesised and characterised for medium temperature fuel cell use (120-180 °C). The electrolyte was characterised by FTIR, SS-NMR, TGA and XRD and showed that the B-O is tetrahedral, in agreement with reports in the literature that boron phosphorus oxide compounds at B:P < 1 are exclusively built of borate and phosphate tetrahedra. Platinum micro electrodes were used to study the electrolyte compatibility and stability towards oxygen reduction at 150 °C and to obtain kinetic and mass transport parameters. The conductivities of the pure BPOx membrane electrolyte and a Polybenzimidazole (PBI)-4BPOx composite membrane were 7.9 × 10-2 S cm-1 and 4.5 × 10-2 S cm-1 respectively at 150 °C, 5%RH. Fuel cell tests showed a significant enhancement in performance of BPOx over that of typical 5.6H3PO4-PBI membrane electrolyte. The enhancement is due to the improved ionic conductivity (3×), a higher exchange current density of the oxygen reduction (30×) and a lower membrane gas permeability (10×). Fuel cell current densities at 0.6 V were 706 and 425 mA cm-2 for BPOx and 5.6H3PO4-PBI, respectively, at 150 °C with O2 (atm).

  11. Studies on the adsorption of cell impurities from plasmid-containing lysates to phenyl boronic acid chromatographic beads.

    PubMed

    Gomes, A Gabriela; Azevedo, Ana M; Aires-Barros, M Raquel; Prazeres, D Miguel F

    2011-12-01

    Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins. PMID:22024344

  12. Fine-Tuning of Lewis Acidity: The Case of Borenium Hydride Complexes Derived from Bis(phosphinimino)amide Boron Precursors.

    PubMed

    Jaiswal, Kuldeep; Prashanth, Billa; Singh, Sanjay

    2016-07-25

    Reactions of bis(phosphinimino)amines LH and L'H with Me2 S⋅BH2 Cl afforded chloroborane complexes LBHCl (1) and L'BHCl (2), and the reaction of L'H with BH3 ⋅Me2 S gave a dihydridoborane complex L'BH2 (3) (LH=[{(2,4,6-Me3 C6 H2 N)P(Ph2 )}2 N]H and L'H=[{(2,6-iPr2 C6 H3 N)P(Ph2 )}2 N]H). Furthermore, abstraction of a hydride ion from L'BH2 (3) and LBH2 (4) mediated by Lewis acid B(C6 F5 )3 or the weakly coordinating ion pair [Ph3 C][B(C6 F5 )4 ] smoothly yielded a series of borenium hydride cations: [L'BH](+) [HB(C6 F5 )3 ](-) (5), [L'BH](+) [B(C6 F5 )4 ](-) (6), [LBH](+) [HB(C6 F5 )3 ](-) (7), and [LBH](+) [B(C6 F5 )4 ](-) (8). Synthesis of a chloroborenium species [LBCl](+) [BCl4 ](-) (9) without involvement of a weakly coordinating anion was also demonstrated from a reaction of LBH2 (4) with three equivalents of BCl3 . It is clear from this study that the sterically bulky strong donor bis(phosphinimino)amide ligand plays a crucial role in facilitating the synthesis and stabilization of these three-coordinated cationic species of boron. Therefore, the present synthetic approach is not dependent on the requirement of weakly coordinating anions; even simple BCl4 (-) can act as a counteranion with borenium cations. The high Lewis acidity of the boron atom in complex 8 enables the formation of an adduct with 4-dimethylaminopyridine (DMAP), [LBH⋅(DMAP)](+) [B(C6 F5 )4 ](-) (10). The solid-state structures of complexes 1, 5, and 9 were investigated by means of single-crystal X-ray structural analysis. PMID:27351275

  13. Autochelation in dipeptide boronic acids: pH-dependent structures and equilibria of Asp-boroPro and His-boroPro by NMR spectroscopy.

    PubMed

    Sudmeier, James L; Zhou, Yuhong; Lai, Jack H; Maw, Hlaing H; Wu, Wengen; Bachovchin, William W

    2005-06-01

    Many dipeptide boronic acids of the type H(2)N-X-Y-B(OH)(2) are potent protease inhibitors. Interest in these compounds as drugs for cancer, diabetes, and other diseases is growing. Because of the great mutual B-N affinity, cyclization through the N- and B-termini, forming six-membered rings, is a common occurrence at neutral pH and higher where the terminal amino group is unprotonated. Here we report the discovery that when X, the N-terminal amino acid, contains a side chain having a functional group with boron affinity and suitable geometry, additional cyclization in the form of bidentate intramolecular chelation or "autochelation" may occur, predominantly at mid pH. NMR studies of two compounds, l-Aspartyl-l-boroProline (Asp-boroPro) and l-Histidyl-l-boroProline (His-boroPro), are reported here from pH 0.5 to pH 12 by (1)H, (15)N, (13)C, and (11)B NMR. Both of these previously unreported autochelates contain two fused six-membered rings, cis-proline, chiral boron, and -NH(2)(+) protons in slow exchange with water, even at 25 degrees C and pH as high as 4. Using microscopic acid-base equilibrium constants, we show that at high pH (>8 for Asp-boroPro and >10 for His-boroPro) hydroxide competes with the side chains for boron, reducing the chelates from bidentate to monodentate. At low pH (<0.5), proton competition for N-terminal nitrogens causes both compounds to become noncyclic. High chelate stability causes a reduction of the apparent acidic dissociation constant of the protonated N-terminal amino group greater than eight units. In the His-boroPro autochelate, imidazolate anion is produced at the extraordinarily low pH value of approximately 9. PMID:15926838

  14. Nickel-Catalyzed Cross Couplings of Benzylic Ammonium Salts and Boronic Acids: Stereospecific Formation of Diarylethanes via C–N Bond Activation

    PubMed Central

    Maity, Prantik; Shacklady-McAtee, Danielle M.; Yap, Glenn P. A.; Sirianni, Eric R.; Watson, Mary P.

    2014-01-01

    We have developed a nickel-catalyzed cross coupling of benzylic ammonium triflates with aryl boronic acids to afford diarylmethanes and diarylethanes. This reaction proceeds under mild reaction conditions and with exceptional functional group tolerance. Further, it transforms branched benzylic ammonium salts to diarylethanes with excellent chirality transfer, offering a new strategy for the synthesis of highly enantioenriched diarylethanes from readily available chiral benzylic amines. PMID:23268734

  15. Structure-activity relationships of boronic acid inhibitors of dipeptidyl peptidase IV. 1. Variation of the P2 position of Xaa-boroPro dipeptides.

    PubMed

    Coutts, S J; Kelly, T A; Snow, R J; Kennedy, C A; Barton, R W; Adams, J; Krolikowski, D A; Freeman, D M; Campbell, S J; Ksiazek, J F; Bachovchin, W W

    1996-05-10

    A series of prolineboronic acid (boroPro) containing dipeptides were synthesized and assayed for their ability to inhibit the serine protease dipeptidyl peptidase IV (DPPIV). Inhibitory activity, which requires the (R)-stereoisomer of boroPro in the P1 position, appears to tolerate a variety of L-amino acids in the P2 position. Substitution at the P2 position which is not tolerated include the D-amino acids, alpha,alpha-disubstituted amino acids, and glycine. Specificity against DPPII and proline specific endopeptidase is reported. A correlation between the ability to inhibit DPPIV in cell culture and in the human mixed lymphocyte reaction is demonstrated. A synthesis of prolineboronic acid is reported as well as conditions for generating the fully unprotected boronic acid dipeptides in either their cyclic or acyclic forms. PMID:8642568

  16. Highly sensitive detection of influenza virus by boron-doped diamond electrode terminated with sialic acid-mimic peptide.

    PubMed

    Matsubara, Teruhiko; Ujie, Michiko; Yamamoto, Takashi; Akahori, Miku; Einaga, Yasuaki; Sato, Toshinori

    2016-08-01

    The progression of influenza varies according to age and the presence of an underlying disease; appropriate treatment is therefore required to prevent severe disease. Anti-influenza therapy, such as with neuraminidase inhibitors, is effective, but diagnosis at an early phase of infection before viral propagation is critical. Here, we show that several dozen plaque-forming units (pfu) of influenza virus (IFV) can be detected using a boron-doped diamond (BDD) electrode terminated with a sialic acid-mimic peptide. The peptide was used instead of the sialyloligosaccharide receptor, which is the common receptor of influenza A and B viruses required during the early phase of infection, to capture IFV particles. The peptide, which was previously identified by phage-display technology, was immobilized by click chemistry on the BDD electrode, which has excellent electrochemical characteristics such as low background current and weak adsorption of biomolecules. Electrochemical impedance spectroscopy revealed that H1N1 and H3N2 IFVs were detectable in the range of 20-500 pfu by using the peptide-terminated BDD electrode. Our results demonstrate that the BDD device integrated with the receptor-mimic peptide has high sensitivity for detection of a low number of virus particles in the early phase of infection. PMID:27457924

  17. Synthesis and application of boronic acid-functionalized magnetic adsorbent for sensitive analysis of salbutamol residues in pig tissues.

    PubMed

    Fan, Hua; Wang, Chaozhan; Wei, Yinmao

    2015-12-01

    Salbutamol (SAL) is the most widely used β2 -agonist drug for asthma and chronic obstructive pulmonary patients, but it is also often abused as feed additive. In recent years, the abuse of SAL has led to a large number of food safety incidents. Therefore, the monitoring of SAL residues in animal products is very important. A highly selective boronate affinity magnetic adsorbent was synthesized and developed for detection of trace levels of SAL residues in pig tissue samples. The obtained Fe3O4@SiO2@FPBA(4-formylphenylboronic acid) magnetic adsorbent showed good adsorption ability to catechol and SAL, and then it was successfully applied as special magnetic solid-phase phase extraction adsorbent coupled with high-performance liquid chromatography (HPLC) for simultaneous isolation and determination of cis-diol compounds. The binding capacity of catechol and SAL reached 96 and 50 µmol/g, respectively. The method was successfully established for the detection of trace levels of SAL in pig tissue samples. The linear range extended from 0.32 to 800 µg/kg (R(2) = 0.9994). The limit of detection of SAL was 0.19 µg/kg. The recoveries were satisfactory (89.5-108.0%) at three spiked levels with RSD between 2.1 and 11.3%. These results indicated that the method has potential for enrichment and detection of trace levels of SAL residual in animal food products. PMID:26061980

  18. Discovery of a Cyclic Boronic Acid β-Lactamase Inhibitor (RPX7009) with Utility vs Class A Serine Carbapenemases.

    PubMed

    Hecker, Scott J; Reddy, K Raja; Totrov, Maxim; Hirst, Gavin C; Lomovskaya, Olga; Griffith, David C; King, Paula; Tsivkovski, Ruslan; Sun, Dongxu; Sabet, Mojgan; Tarazi, Ziad; Clifton, Matthew C; Atkins, Kateri; Raymond, Amy; Potts, Kristy T; Abendroth, Jan; Boyer, Serge H; Loutit, Jeffrey S; Morgan, Elizabeth E; Durso, Stephanie; Dudley, Michael N

    2015-05-14

    The increasing dissemination of carbapenemases in Gram-negative bacteria has threatened the clinical usefulness of the β-lactam class of antimicrobials. A program was initiated to discover a new series of serine β-lactamase inhibitors containing a boronic acid pharmacophore, with the goal of finding a potent inhibitor of serine carbapenemase enzymes that are currently compromising the utility of the carbapenem class of antibacterials. Potential lead structures were screened in silico by modeling into the active sites of key serine β-lactamases. Promising candidate molecules were synthesized and evaluated in biochemical and whole-cell assays. Inhibitors were identified with potent inhibition of serine carbapenemases, particularly the Klebsiella pneumoniae carbapenemase (KPC), with no inhibition of mammalian serine proteases. Studies in vitro and in vivo show that RPX7009 (9f) is a broad-spectrum inhibitor, notably restoring the activity of carbapenems against KPC-producing strains. Combined with a carbapenem, 9f is a promising product for the treatment of multidrug resistant Gram-negative bacteria. PMID:25782055

  19. Specific interactions of alcohols and non-alcohols with a biologically active boronic acid derivative: a spectroscopic study.

    PubMed

    Geethanjali, H S; Melavanki, R M; Nagaraja, D; Patil, N R; Thipperudrappa, J; Kusanur, R A

    2016-08-01

    The photophysical properties of 4-fluoro-2-methoxyphenyl boronic acid (4FMPBA) are characterized using absorption and fluorescence techniques in series of non-alcohols and alcohols. The results are analyzed using different solvent polarity functions and Kamlet and Catalan's multiple regression approaches. The excited state dipole moment and change in dipole moment are calculated using both the solvatochromic shift method and Reichardt's microscopic solvent polarity parameter ETN. The ground state dipole moment is evaluated using quantum chemical calculations. It is found that general solute-solvent and hydrogen bond interactions are operative in this system. A red shift of ~ 9 nm in the emission spectra is observed with an increase in the solvent polarity, which depicts π→π(*) transitions, as well as the possibility of an intramolecular charge transfer (ICT) character in the emitting singlet state of 4FMPBA. The relative quantum yield, radiative and non-radiative decay constants are calculated in alkanes and alcohols using the single point method. It is found that the quantum yield of the molecule varies from 16.81% to 50.79% with the change in solvent polarity, indicating the dependence of fluorescence on the solvent environment. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26626020

  20. Inhibiting the β-Lactamase of Mycobacterium tuberculosis (Mtb) with Novel Boronic Acid Transition-State Inhibitors (BATSIs).

    PubMed

    Kurz, Sebastian G; Hazra, Saugata; Bethel, Christopher R; Romagnoli, Chiara; Caselli, Emilia; Prati, Fabio; Blanchard, John S; Bonomo, Robert A

    2015-06-12

    BlaC, the single chromosomally encoded β-lactamase of Mycobacterium tuberculosis, has been identified as a promising target for novel therapies that rely upon β-lactamase inhibition. Boronic acid transition-state inhibitors (BATSIs) are a class of β-lactamase inhibitors which permit rational inhibitor design by combinations of various R1 and R2 side chains. To explore the structural determinants of effective inhibition, we screened a panel of 25 BATSIs to explore key structure-function relationships. We identified a cefoperazone analogue, EC19, which displayed slow, time-dependent inhibition against BlaC with a potency similar to that of clavulanate (Ki* of 0.65 ± 0.05 μM). To further characterize the molecular basis of inhibition, we solved the crystallographic structure of the EC19-BlaC(N172A) complex and expanded our analysis to variant enzymes. The results of this structure-function analysis encourage the design of a novel class of β-lactamase inhibitors, BATSIs, to be used against Mycobacterium tuberculosis. PMID:27622739

  1. Process for recovering boron trifluoride from an impure gaseous boron trifluoride residue

    SciTech Connect

    Evans, F.E.; Schroeder, K.H.; Wagner, W.J.

    1990-07-24

    This patent describes a method for removing sulfur dioxide from a boron trifluoride stream. It comprises: condensing a gaseous boron trifluoride stream; distilling the condensed boron trifluoride stream to yield pure boron trifluoride and a liquid boron trifluoride residue wherein the liquid boron trifluoride residue comprises by weight: about 40 to about 95% boron trifluoride, about 5 to about 30% sulfur dioxide, about 0 to 19% sulfur trioxide, about 0 to about 0.2% silicon fluoride, about 0 to about 1.0% arsenic fluoride, and about 0 to about 0.1% antimony fluoride; vaporizing the liquid boron trifluoride residue; feeding the gaseous boron trifluoride residue into a mixture of boric and sulfuric acids; and removing the unabsorbed sulfur dioxide from the acid mixture.

  2. Mechanism of Boron-Catalyzed N-Alkylation of Amines with Carboxylic Acids.

    PubMed

    Zhang, Qi; Fu, Ming-Chen; Yu, Hai-Zhu; Fu, Yao

    2016-08-01

    Mechanistic study has been carried out on the B(C6F5)3-catalyzed amine alkylation with carboxylic acid. The reaction includes acid-amine condensation and amide reduction steps. In condensation step, the catalyst-free mechanism is found to be more favorable than the B(C6F5)3-catalyzed mechanism, because the automatic formation of the stable B(C6F5)3-amine complex deactivates the catalyst in the latter case. Meanwhile, the catalyst-free condensation is constituted by nucleophilic attack and the indirect H2O-elimination (with acid acting as proton shuttle) steps. After that, the amide reduction undergoes a Lewis acid (B(C6F5)3)-catalyzed mechanism rather than a Brønsted acid (B(C6F5)3-coordinated HCOOH)-catalyzed one. The B(C6F5)3)-catalyzed reduction includes twice silyl-hydride transfer steps, while the first silyl transfer is the rate-determining step of the overall alkylation catalytic cycle. The above condensation-reduction mechanism is supported by control experiments (on both temperature and substrates). Meanwhile, the predicted chemoselectivity is consistent with the predominant formation of the alkylation product (over disilyl acetal product). PMID:27441997

  3. Minerals Yearbook 1989: Boron

    SciTech Connect

    Lyday, P.A.

    1990-08-01

    U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position as a source of sodium borate products and boric acid exported to foreign markets. Supplementary U.S. imports of Turkish calcium borate and calcium-sodium borate ores, borax, and boric acid, primarily for various glass uses, continued.

  4. Epoxy resin composition containing metal tetrafluoroborate and boron ester

    SciTech Connect

    Morehead, G.T.

    1990-06-12

    This patent describes a curable composition. It comprises: a polyepoxide; a metal tetrafluoroborate; and at least one boron ester selected from the group consisting of triesters of boric acid and diesters of boronic acid.

  5. N,N-Dimethyl formamide facilitated formation of hexagonal boron nitride from boric acid

    NASA Astrophysics Data System (ADS)

    Xue, Yanming; Elsanousi, Ammar; Fan, Ying; Lin, Jing; Li, Jie; Xu, Xuewen; Lu, Yang; Zhang, Lei; Zhang, Tingting; Tang, Chengchun

    2013-10-01

    In this paper, we report on a promoting novel process for the formation of h-BN plates by using N,N-dimethyl formamide-treated boric acid (DMF-BA). Using this B source, the formation of h-BN can be indeed improved greatly compared to using pure boric acid (BA). This method effectively reduces the content of boric acid and amorphous boric oxide, enhancing the transformation rate of h-BN. For preparation of pure h-BN, it can obviously lower the resultant temperature without further purification process. Via graphitization index (G.I.) calculation and thermostability analysis, the pure h-BN plates obtained from the DMF-BA would be a promising candidate for raw material of c-BN and low-temperature applications in the air.

  6. Mineralization of salicylic acid in acidic aqueous medium by electrochemical advanced oxidation processes using platinum and boron-doped diamond as anode and cathodically generated hydrogen peroxide.

    PubMed

    Guinea, Elena; Arias, Conchita; Cabot, Pere Lluís; Garrido, José Antonio; Rodríguez, Rosa María; Centellas, Francesc; Brillas, Enric

    2008-01-01

    Solutions containing 164 mg L(-1) salicylic acid of pH 3.0 have been degraded by electrochemical advanced oxidation processes such as anodic oxidation, anodic oxidation with electrogenerated H(2)O(2), electro-Fenton, photoelectro-Fenton and solar photoelectro-Fenton at constant current density. Their oxidation power has been comparatively studied in a one-compartment cell with a Pt or boron-doped diamond (BDD) anode and a graphite or O(2)-diffusion cathode. In the three latter procedures, 0.5mM Fe(2+) is added to the solution to form hydroxyl radical (()OH) from Fenton's reaction between Fe(2+) and H(2)O(2) generated at the O(2)-diffusion cathode. Total mineralization is attained for all methods with BDD and for photoelectro-Fenton and solar photoelectro-Fenton with Pt. The poor decontamination achieved in anodic oxidation and electro-Fenton with Pt is explained by the slow removal of most pollutants by ()OH formed from water oxidation at the Pt anode in comparison to their quick destruction with ()OH produced at BDD. ()OH generated from Fenton's reaction oxidizes rapidly all aromatic pollutants, but it cannot destroy final Fe(III)-oxalate complexes. Solar photoelectro-Fenton treatments always yield quicker degradation rate due to the very fast photodecarboxylation of these complexes by UVA irradiation supplied by solar light. The effect of current density on the degradation rate, efficiency and energy cost of all methods is examined. The salicylic acid decay always follows a pseudo-first-order kinetics. 2,3-Dihydroxybenzoic, 2,5-dihydroxybenzoic, 2,6-dihydroxybenzoic, alpha-ketoglutaric, glycolic, glyoxylic, maleic, fumaric, malic, tartronic and oxalic acids are detected as oxidation products. A general reaction sequence for salicylic acid mineralization considering all these intermediates is proposed. PMID:17692891

  7. Comparing atrazine and cyanuric acid electro-oxidation on mixed oxide and boron-doped diamond electrodes.

    PubMed

    Malpass, Geoffroy R P; Salazar-Banda, Giancarlo R; Miwa, Douglas W; Machado, Sérgio A S; Motheo, Artur J

    2013-01-01

    The breakdown of pesticides has been promoted by many methods for clean up of contaminated soil and wastewaters. The main goal is to decrease the toxicity of the parent compound to achieve non-toxic compounds or even, when complete mineralization occurs, carbon dioxide and water. Therefore, electrochemical degradation (potentiostatic and galvanostatic) of both the pesticide atrazine and cyanuric acid (CA) at boron-doped diamond (BDD) and Ti/Ru0.3Ti0.7O2 dimensionally stable anode (DSA) electrodes, in different supporting electrolytes (NaCl and Na2SO4), is presented with the aim of establishing the influence of the operational parameters on the process efficiency. The results demonstrate that both the electrode material and the supporting electrolyte have a strong influence on the rate of atrazine removal. In the chloride medium, the rate of atrazine removal is always greater than in sulfate under all conditions employed. Furthermore, in the sulfate medium, atrazine degradation was significant only at the BDD electrode. The total organic carbon (TOC) load decreased by 79% and 56% at the BDD and DSA electrodes, respectively, in the chloride medium. This trend was maintained in the sulfate medium but the TOC removal was lower (i.e. 33% and 13% at BDD and DSA electrodes, respectively). CA, a stable atrazine degradation intermediate, was also studied and it is efficiently removed using the BDD electrode in both media, mainly when high current densities are employed. The use of the BDD electrode in the chloride medium not only degrades atrazine but also mineralized cyanuric acid leading to the higher TOC removal. PMID:23837356

  8. Chemoselective Boronic Ester Synthesis by Controlled Speciation**

    PubMed Central

    Fyfe, James W B; Seath, Ciaran P; Watson, Allan J B

    2014-01-01

    Control of boronic acid solution speciation is presented as a new strategy for the chemoselective synthesis of boronic esters. Manipulation of the solution equilibria within a cross-coupling milieu enables the formal homologation of aryl and alkenyl boronic acid pinacol esters. The generation of a new, reactive boronic ester in the presence of an active palladium catalyst also facilitates streamlined iterative catalytic C=C bond formation and provides a method for the controlled oligomerization of sp2-hybridized boronic esters. PMID:25267096

  9. Crystal structure of (2′,3,6′-tri­chloro­biphenyl-2-yl)boronic acid tetra­hydro­furan monosolvate

    PubMed Central

    Durka, Krzysztof; Kliś, Tomasz; Serwatowski, Janusz

    2015-01-01

    The title compound, C12H8BCl3O2·C4H8O, crystallizes as a tetra­hydro­furan monosolvate. The boronic acid group adopts a syn–anti conformation and is significantly twisted along the carbon–boron bond by 69.2 (1)°, due to considerable steric hindrance from the 2′,6′-di­chloro­phenyl group that is located ortho to the boronic acid substituent. The phenyl rings of the biphenyl are almost perpendicular to one another, with a dihedral angle of 87.9 (1)° between them. In the crystal, adjacent mol­ecules are linked via O—H⋯O inter­actions to form centrosymmetric dimers with R 2 2(8) motifs, which have recently been shown to be energetically very favourable. The hy­droxy groups are in an anti conformation and are also engaged in hydrogen-bonding inter­actions with the O atom of the tetra­hydro­furan solvent mol­ecule. Cl⋯Cl halogen-bonding inter­actions [Cl⋯Cl = 3.464 (1) Å] link neigbouring dimers into chains running along [010]. Further aggregation occurs due to an additional Cl⋯Cl halogen bond [Cl⋯Cl = 3.387 (1) Å]. PMID:26870407

  10. Crystal structure of (2',3,6'-tri-chloro-biphenyl-2-yl)boronic acid tetra-hydro-furan monosolvate.

    PubMed

    Durka, Krzysztof; Kliś, Tomasz; Serwatowski, Janusz

    2015-12-01

    The title compound, C12H8BCl3O2·C4H8O, crystallizes as a tetra-hydro-furan monosolvate. The boronic acid group adopts a syn-anti conformation and is significantly twisted along the carbon-boron bond by 69.2 (1)°, due to considerable steric hindrance from the 2',6'-di-chloro-phenyl group that is located ortho to the boronic acid substituent. The phenyl rings of the biphenyl are almost perpendicular to one another, with a dihedral angle of 87.9 (1)° between them. In the crystal, adjacent mol-ecules are linked via O-H⋯O inter-actions to form centrosymmetric dimers with R 2 (2)(8) motifs, which have recently been shown to be energetically very favourable. The hy-droxy groups are in an anti conformation and are also engaged in hydrogen-bonding inter-actions with the O atom of the tetra-hydro-furan solvent mol-ecule. Cl⋯Cl halogen-bonding inter-actions [Cl⋯Cl = 3.464 (1) Å] link neigbouring dimers into chains running along [010]. Further aggregation occurs due to an additional Cl⋯Cl halogen bond [Cl⋯Cl = 3.387 (1) Å]. PMID:26870407

  11. Autoradiographic and histopathological studies of boric acid-mediated BNCT in hepatic VX2 tumor-bearing rabbits: Specific boron retention and damage in tumor and tumor vessels.

    PubMed

    Yang, C H; Lin, Y T; Hung, Y H; Liao, J W; Peir, J J; Liu, H M; Lin, Y L; Liu, Y M; Chen, Y W; Chuang, K S; Chou, F I

    2015-12-01

    Hepatoma is a malignant tumor that responds poorly to conventional therapies. Boron neutron capture therapy (BNCT) may provide a better way for hepatoma therapy. In this research, (10)B-enriched boric acid (BA, 99% (10)B) was used as the boron drug. A multifocal hepatic VX2 tumor-bearing rabbit model was used to study the mechanisms of BA-mediated BNCT. Autoradiography demonstrated that BA was selectively targeted to tumors and tumor vessels. Histopathological examination revealed the radiation damage to tumor-bearing liver was concentrated in the tumor regions during BNCT treatment. The selective killing of tumor cells and the destruction of the blood vessels in tumor masses may be responsible for the success of BA-mediated BNCT for liver tumors. PMID:26372198

  12. Separation of glycols from dilute aqueous solutions via complexation with boronic acids

    SciTech Connect

    Randel, L.A.; King, C.J.

    1991-07-01

    This work examines methods of separating low molecular weight glycols from dilute aqueous solution. Extraction into conventional solvents is generally not economical, since, in the literature reviewed, distribution ratios for the two- to four-carbon glycols are all less than one. Distribution ratios can be increased, however, by incorporating into the organic phase an extracting agent that will complex with the solute of interest. The extracting agent investigated in this work is 3-nitrophenylboronic acid (NPBA). NPBA, a boric acid derivative, reversibly complexes with many glycols. The literature on complexation of borate and related compounds with glycols, including mechanistic data, measurement techniques, and applications to separation processes, provides information valuable for designing experiments with NPBA and is reviewed herein. 88 refs., 15 figs., 24 tabs.

  13. Catalytic conversion of cellulose to fuels and chemicals using boronic acids

    SciTech Connect

    Raines, Ronald; Caes, Benjamin; Palte, Michael

    2015-10-20

    Methods and catalyst compositions for formation of furans from carbohydrates. A carbohydrate substrate is heating in the presence of a 2-substituted phenylboronic acid (or salt or hydrate thereof) and optionally a magnesium or calcium halide salt. The reaction is carried out in a polar aprotic solvent other than an ionic liquid, an ionic liquid or a mixture thereof. Additional of a selected amount of water to the reaction can enhance the yield of furans.

  14. Carbonylative Suzuki Couplings of Aryl Bromides with Boronic Acid Derivatives under Base-Free Conditions

    PubMed Central

    2015-01-01

    The carbonylative Suzuki–Miyaura reaction between aryl bromides and arylboronic acid equivalents is herein reported, using base-free conditions and a limited excess of carbon monoxide generated ex situ from stable CO-precursors. Under these conditions, unsymmetrical biaryl ketones were obtained in modest to excellent yields. This method was adapted to the synthesis of the triglyceride and cholesterol regulator drug, fenofibrate, and its 13C-labeled derivative in good yields from the appropriate CO-precursor. PMID:24635142

  15. Development of improved analytical procedures for boron purification: Final report

    SciTech Connect

    Larson, J.D.; Fossey, J.L.; Hinds, S.C.; Lantz, L.L.; Smith, R.E.

    1988-06-01

    Three new analytical methods for boron powder certification were developed and evaluated during this project. First, the boric acid content of the powder was determined by an acid-base titration method. Second, the moisture content of boron samples was measured with a moisture evolution analyzer. Third, boron powder samples were acid digested in a microwave oven. 11 refs., 1 fig., 8 tabs.

  16. Highly boron deficiency-tolerant plants generated by enhanced expression of NIP5;1, a boric acid channel.

    PubMed

    Kato, Yuichi; Miwa, Kyoko; Takano, Junpei; Wada, Motoko; Fujiwara, Toru

    2009-01-01

    Boron (B) is an essential element for plants, and B deficiency is a worldwide agricultural problem. In B-deficient areas, B is often supplied as fertilizer, but excess B can be toxic to both plants and animals. Generation of B deficiency-tolerant plants could reduce B fertilizer use. Improved fertility under B-limiting conditions in Arabidopsis thaliana by overexpression of BOR1, a B transporter, has been reported, but the root growth was not improved by the BOR1 overexpression. In this study, we report that enhanced expression of NIP5;1, a boric acid channel for efficient B uptake, resulted in improved root elongation under B-limiting conditions in A. thaliana. An NIP5;1 activation tag line, which has a T-DNA insertion with enhancer sequences near the NIP5;1 gene, showed improved root elongation under B limitation. We generated a construct which mimics the tag line: the cauliflower mosaic virus 35S RNA promoter was inserted at 1,357 bp upstream of the NIP5;1 transcription initiation site. Introduction of this construct into the nip5;1-1 mutant and the BOR1 overexpresser resulted in enhanced expression of NIP5;1 and improved root elongation under low B supply. Furthermore, one of the transgenic lines exhibited improved fertility and short-term B uptake. Our results demonstrate successful improvement of B deficiency tolerance and the potential of enhancing expression of a mineral nutrient channel gene to improve growth under nutrient-limiting conditions. PMID:19017629

  17. Design and Exploration of Novel Boronic Acid Inhibitors Reveals Important Interactions with a Clavulanic Acid-Resistant Sulfhydryl-Variable (SHV) β-Lactamase

    PubMed Central

    Winkler, Marisa L.; Rodkey, Elizabeth A.; Taracila, Magdalena A.; Drawz, Sarah M.; Bethel, Christopher R.; Papp-Wallace, Krisztina M.; Smith, Kerri M.; Xu, Yan; Dwulit-Smith, Jeffrey R.; Romagnoli, Chiara; Caselli, Emilia; Prati, Fabio; van den Akker, Focco; Bonomo, Robert A.

    2014-01-01

    Inhibitor resistant (IR) class A β-lactamases pose a significant threat to many current antibiotic combinations. The K234R substitution in the SHV β-lactamase, from Klebsiella pneumoniae, results in resistance to ampicillin/clavulanate. After site-saturation mutagenesis of Lys-234 in SHV, microbiological and biochemical characterization of the resulting β-lactamases revealed that only –Arg conferred resistance to ampicillin/clavulanate. X-ray crystallography revealed two conformations of Arg-234 and Ser-130 in SHV K234R. The movement of Ser-130 is the principal cause of the observed clavulanate resistance. A panel of boronic acid inhibitors was designed and tested against SHV-1 and SHV K234R. A chiral ampicillin analogue was discovered to have a 2.4 ± 0.2 nM Ki for SHV K234R; the chiral ampicillin analogue formed a more complex hydrogen-bonding network in SHV K234R vs SHV-1. Consideration of the spatial position of Ser-130 and Lys-234 and this hydrogen-bonding network will be important in the design of novel antibiotics targeting IR β-lactamases. PMID:23252553

  18. Development of boronic acid grafted random copolymer sensing fluid for continuous glucose monitoring

    PubMed Central

    Li, Siqi; Davis, Erin N; Anderson, Jordan; Lin, Qiao; Wang, Qian

    2009-01-01

    We have previously presented a MEMS viscometric sensor for continuous glucose monitoring using protein Concanavalin A (Con A). To address its drawbacks including immunotoxicity and instability issues, we have synthesized stable, biocompatible copolymers poly(acrylamide-ran-3- acrylamidophenylboronic acid) (PAA-ran-PAAPBA) for viscosity based glucose sensing. We found that PAA-ran-PAAPBA showed very high binding specificity to glucose. Several key factors such as polymer compositions, polymer molecular weights and polymer concentrations have been investigated to optimize viscometric responses. This polymer is able to detect glucose under physiological conditions in a reversible manner. Therefore, it has the potential to enable the highly reliable, continuous monitoring of glucose in subcutaneous tissue using the MEMS device. PMID:19067585

  19. High-efficiency extraction of nucleosides based on the combination of self-assembly ionic liquid layer and boronic acid-functionalized attapulgite.

    PubMed

    Li, Huihui; Cheng, Ting; Wang, Shuxia; Zhu, Xinyue; Zhang, Haixia

    2016-06-01

    Boronate affinity materials have been widely used for selective capture of cis-diol-containing molecules, but most do not have sufficient extraction efficiency. We have prepared boronic acid-functionalized attapulgite, and then it was coated with imidazolium-based ionic liquid, 1-dodecyl-3-methylimidazolium bromide (C12mimBr), via physical self-assembly process. The extraction efficiency of the material increased dramatically after coated with C12mimBr, and its enrichment ratios for nucleosides increased by 9- to 282-fold. Besides, the C12mimBr-coated adsorbent did not lose selectivity and was able to capture cis-diols in the presence of a 100-fold excess of interferences. C12mimBr-coated material was applied to selective enrichment of nucleosides from human urine. The limits of detection and the limits of quantification were in the range of 0.06-0.46ngmL(-1) and 0.20-1.53ngmL(-1), respectively. Reproducibility of the method was determined with relative standard deviations≤9.9%. The recoveries of the target nucleosides from spiked human urine were in the range of 87.8-109.6%. In our preception, self-assembly ionic liquid layer can serve as a promising alternative to improve the extraction efficiency of boronate affinity materials. PMID:27130092

  20. Characterization of peptidyl boronic acid inhibitors of mammalian 20 S and 26 S proteasomes and their inhibition of proteasomes in cultured cells.

    PubMed Central

    Gardner, R C; Assinder, S J; Christie, G; Mason, G G; Markwell, R; Wadsworth, H; McLaughlin, M; King, R; Chabot-Fletcher, M C; Breton, J J; Allsop, D; Rivett, A J

    2000-01-01

    Proteasomes are large multisubunit proteinases which have several distinct catalytic sites. In this study a series of di- and tri-peptidyl boronic acids have been tested on the chymotrypsin-like activity of purified mammalian 20 S and 26 S proteasomes assayed with succinyl-Leu-Leu-Val-Tyr-amidomethylcoumarin (suc-Leu-Leu-Val-Tyr-AMC) as substrate. The inhibition of 20 S proteasomes is competitive but only slowly reversible. The K(i) values for the best inhibitors were in the range 10-100 nM with suc-Leu-Leu-Val-Tyr-AMC as substrate, but the compounds tested were much less effective on other proteasome activities measured with other substrates. Free boronic acid inhibitors exhibited equivalent potency to their pinacol esters. Both benzoyl (Bz)-Phe-boroLeu and benzyloxycarbonyl (Cbz)-Leu-Leu-boroLeu pinacol ester inhibited 20 S and 26 S proteasomes with non-ideal behaviour, differences in inhibition of the two forms of proteasomes becoming apparent at high inhibitor concentrations (above 3xK(i)). Both of these compounds were also potent inhibitors of 20 S and 26 S proteasomes in cultured cells. However, gel filtration of cell extracts prepared from cells treated with radiolabelled phenacetyl-Leu-Leu-boroLeu showed that only 20 S proteasomes were strongly labelled, demonstrating differences in the characteristics of inhibition of 20 S and 26 S proteasomes. The usefulness of peptidyl boronic acid inhibitors for investigations of proteasome-mediated protein degradation was confirmed by the observation that Bz-Phe-boroLeu and Cbz-Leu-Leu-boroLeu pinacol ester inhibited NFkappaB activation with IC(50) values comparable to their K(i) values for purified proteasomes. The latter result supports the view that the chymotrypsin-like activity of proteasomes assayed with suc-Leu-Leu-Val-Tyr-AMC is a critical one for protein degradation in cells. PMID:10677365

  1. The development of copper-catalyzed aerobic oxidative coupling of H-tetrazoles with boronic acids and an insight into the reaction mechanism.

    PubMed

    Liu, Chao-You; Li, Yu; Ding, Jin-Ying; Dong, De-Wen; Han, Fu-She

    2014-02-17

    The development of a highly efficient and practical protocol for the direct C-N coupling of H-tetrazole and boronic acid was presented. A careful and patient optimization of a variety of reaction parameters revealed that this conventionally challenge reaction could indeed proceed efficiently in a very simple system, that is, just by stirring the tetrazoles and boronic acids under oxygen in the presence of different Cu(I) or Cu(II) salts with only 5 mol % loading in DMSO at 100 °C. Most significantly, the reaction could proceed very smoothly in a regiospecific manner to afford the 2,5-disubstituted tetrazoles in high to excellent yields. A mechanistic study revealed that both tetrazole and DMSO are crucial for the generation of catalytically active copper species in the reaction process in addition to their role as reactant and solvent, respectively. It is demonstrated that in the reaction cycle, the Cu(I) catalyst could be oxidized to Cu(II) by oxygen to form a [CuT2D] complex (T = tetrazole anion; D = DMSO) through an oxidative copper amination reaction. The Cu(II) complex thus formed was confirmed to be the real catalytically active copper species. Namely, the Cu(II) complex disproportionates to aryl Cu(III) and Cu(I) in the presence of boronic acid. Facile elimination of the Cu(III) species delivers the C-N-coupled product. The results presented herein not only provide a reliable and efficient protocol for the synthesis of 2,5-disubstituted tetrazoles, but most importantly, the mechanistic results would have broad implications for the de novo design and development of new methods for Cu-catalyzed coupling reactions. PMID:24449340

  2. A ratiometric fluorescent probe based on boron dipyrromethene and rhodamine Förster resonance energy transfer platform for hypochlorous acid and its application in living cells.

    PubMed

    Liu, Ying; Zhao, Zhi-Min; Miao, Jun-Ying; Zhao, Bao-Xiang

    2016-05-19

    We have developed a ratiometric fluorescent probe BRT based on boron dipyrromethene (BODIPY) and rhodamine-thiohydrazide Förster resonance energy transfer (FRET) platform for sensing hypochlorous acid (HOCl) with high selectivity and sensitivity. The probe can detect HOCl in 15 s with the detection limit of 38 nM. Upon mixing with HOCl the fluorescence colour of probe BRT changed from green to orange. Moreover, probe BRT was applied to successfully monitor HOCl in living RAW 264.7 cells. PMID:27126792

  3. Horseradish peroxidase-catalyzed synthesis of poly(thiophene-3-boronic acid) biocomposites for mono-/bi-enzyme immobilization and amperometric biosensing.

    PubMed

    Huang, Yi; Wang, Wen; Li, Zou; Qin, Xiaoli; Bu, Lijuan; Tang, Zhiyong; Fu, Yingchun; Ma, Ming; Xie, Qingji; Yao, Shouzhuo; Hu, Jiming

    2013-06-15

    We report here on a facile enzymatic polymerization protocol to prepare enzyme-poly(thiophene-3-boronic acid) (PTBA) polymeric biocomposites (PBCs) for high-performance mono-/bi-enzyme amperometric biosensing. Horseradish peroxidase (HRP)-catalyzed polymerization of thiophene-3-boronic acid (TBA) monomer was conducted in aqueous solution containing HRP (or plus glucose oxidase (GOx)) by either directly added or GOx-glucose generated oxidant H2O2. The mono-/bi-enzyme amperometric biosensors were prepared simply by casting the dialysis-isolated PBCs on Au-plated Au electrode (Auplate/Au), followed by coating with an outer-layer chitosan (CS) film. The boronic acid residues are capable of covalent bonding with enzyme at the glycosyl sites (boronic acid-diols interaction), which should less affect the enzymatic activity as compared with the common cases of covalent bonding at the peptide chains, and UV-vis spectrophotometric tests confirmed that the encapsulated HRP almost possesses its pristine enzymatic specific activity. The enzyme electrodes were studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry in the presence of Fe(CN)6(4-) mediator. The CS/HRP-PTBA/Auplate/Au electrode responded linearly to H2O2 concentration from 1 to 300 μM with a sensitivity of 390 μA mM(-1)cm(-2) and a limit of detection (LOD) of 0.1 μM. The bienzyme CS/GOx-HRP-PTBA(H2O2)/Auplate/Au electrode responded linearly to glucose concentration from 5 μM to 0.83 mM with a sensitivity of 75.1 μA mM(-1)cm(-2) and a LOD of 1 μM, and it is found here that the use of Fe(CN)6(4-) that can only efficiently mediate HRP favorably avoids the "unusual amperometric responses" observed when other mediators that can efficiently turn over both HRP and GOx are used. PMID:23391705

  4. A pH-responsive drug nanovehicle constructed by reversible attachment of cholesterol to PEGylated poly(l-lysine) via catechol-boronic acid ester formation.

    PubMed

    Yang, Bin; Lv, Yin; Zhu, Jing-Yi; Han, Yun-Tao; Jia, Hui-Zhen; Chen, Wei-Hai; Feng, Jun; Zhang, Xian-Zheng; Zhuo, Ren-Xi

    2014-08-01

    The present work reports the construction of a drug delivery nanovehicle via a pH-sensitive assembly strategy for improved cellular internalization and intracellular drug liberation. Through spontaneous formation of boronate linkage in physiological conditions, phenylboronic acid-modified cholesterol was able to attach onto catechol-pending methoxypoly(ethylene glycol)-block-poly(l-lysine). This comb-type polymer can self-organize into a micellar nanoconstruction that is able to effectively encapsulate poorly water-soluble agents. The blank micelles exhibited negligible in vitro cytotoxicity, yet doxorubicin (DOX)-loaded micelles could effectively induce cell death at a level comparable to free DOX. Owing to the acid-labile feature of the boronate linkage, a reduction in environmental pH from pH 7.4 to 5.0 could trigger the dissociation of the nanoconstruction, which in turn could accelerate the liberation of entrapped drugs. Importantly, the blockage of endosomal acidification in HeLa cells by NH4Cl treatment significantly decreased the nuclear uptake efficiency and cell-killing effect mediated by the DOX-loaded nanoassembly, suggesting that acid-triggered destruction of the nanoconstruction is of significant importance in enhanced drug efficacy. Moreover, confocal fluorescence microscopy and flow cytometry assay revealed the effective internalization of the nanoassemblies, and their cellular uptake exhibited a cholesterol dose-dependent profile, indicating the contribution of introduced cholesterol functionality to the transmembrane process of the nanoassembly. PMID:24879311

  5. Identification of a novel boronic acid as a potent, selective, and orally active hormone sensitive lipase inhibitor.

    PubMed

    Ogiyama, Tomoko; Yamaguchi, Mitsuhiro; Kurikawa, Nobuya; Honzumi, Shoko; Yamamoto, Yuka; Sugiyama, Daisuke; Inoue, Shinichi

    2016-08-15

    Hormone sensitive lipase (HSL) is an attractive therapeutic target of dyslipidemia. We designed and synthesized several compounds as reversible HSL inhibitors with a focus on hydrophobic interactions, which was thought to be effective upon the HSL inhibitory activity. In these efforts, we identified boronated compound 12 showing a potent HSL inhibitory activity with an IC50 value of 7nM and a high selectivity against cholinesterases. Furthermore, compound 12 is the first boron containing HSL inhibitor that has shown an antilipolytic effect in rats after oral administration at 3mg/kg. PMID:27338659

  6. Boron incorporation into mullite

    NASA Astrophysics Data System (ADS)

    Griesser, K. J.; Beran, A.; Voll, D.; Schneider, H.

    2008-03-01

    Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol gel process with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the mullite structure in form of planar three-fold coordinated BO3 groups.

  7. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish; Anthonysamy, S.; Ghosh, C.; Ravindran, T.R.; Divakar, R.; Mohandas, E.

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ∼ 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  8. Crystal Structures of KPC-2 and SHV-1 β-Lactamases in Complex with the Boronic Acid Transition State Analog S02030.

    PubMed

    Nguyen, Nhu Q; Krishnan, Nikhil P; Rojas, Laura J; Prati, Fabio; Caselli, Emilia; Romagnoli, Chiara; Bonomo, Robert A; van den Akker, Focco

    2016-03-01

    Resistance to expanded-spectrum cephalosporins and carbapenems has rendered certain strains of Klebsiella pneumoniae the most problematic pathogens infecting patients in the hospital and community. This broad-spectrum resistance to β-lactamases emerges in part via the expression of KPC-2 and SHV-1 β-lactamases and variants thereof. KPC-2 carbapenemase is particularly worrisome, as the genetic determinant encoding this β-lactamase is rapidly spread via plasmids. Moreover, KPC-2, a class A enzyme, is difficult to inhibit with mechanism-based inactivators (e.g., clavulanate). In order to develop new β-lactamase inhibitors (BLIs) to add to the limited available armamentarium that can inhibit KPC-2, we have structurally probed the boronic acid transition state analog S02030 for its inhibition of KPC-2 and SHV-1. S02030 contains a boronic acid, a thiophene, and a carboxyl triazole moiety. We present here the 1.54- and 1.87-Å resolution crystal structures of S02030 bound to SHV-1 and KPC-2 β-lactamases, respectively, as well as a comparative analysis of the S02030 binding modes, including a previously determined S02030 class C ADC-7 β-lactamase complex. S02030 is able to inhibit vastly different serine β-lactamases by interacting with the conserved features of these active sites, which includes (i) forming the bond with catalytic serine via the boron atom, (ii) positioning one of the boronic acid oxygens in the oxyanion hole, and (iii) utilizing its amide moiety to make conserved interactions across the width of the active site. In addition, S02030 is able to overcome more distantly located structural differences between the β-lactamases. This unique feature is achieved by repositioning the more polar carboxyl-triazole moiety, generated by click chemistry, to create polar interactions as well as reorient the more hydrophobic thiophene moiety. The former is aided by the unusual polar nature of the triazole ring, allowing it to potentially form a unique C-H…O 2

  9. Synthesis, characterization and fuel cell performance tests of boric acid and boron phosphate doped, sulphonated and phosphonated poly(vinyl alcohol) based composite membranes

    NASA Astrophysics Data System (ADS)

    Şahin, Alpay; Ar, İrfan

    2015-08-01

    The aim of this study is to synthesize a composite membrane having high proton conductivity, ion exchange capacity and chemical stability. In order to achieve this aim, poly(vinyl alcohol) (PVA) based composite membranes are synthesized by using classic sol-gel method. Boric acid (H3BO3) and boron phosphate (BPO4) are added to the membrane matrix in different ratios in order to enhance the membrane properties. Characterization tests, i.e; FT-IR analysis, mechanical strength tests, water hold-up capacities, swelling properties, ion exchange capacities, proton conductivities and fuel cell performance tests of synthesized membranes are carried out. As a result of performance experiments highest performance values are obtained for the membrane containing 15% boron phosphate at 0.6 V and 750 mA/cm2. Water hold-up capacity, swelling ratio, ion exchange capacity and proton conductivity of this membrane are found as 56%, 8%, 1.36 meq/g and 0.37 S/cm, respectively. These values are close to the values obtained ones for perfluorosulphonic acid membranes. Therefore this membrane can be regarded as a promising candidate for usage in fuel cells.

  10. Chemical and biological evaluation of dipeptidyl boronic acid proteasome inhibitors for use in prodrugs and pro-soft drugs targeting solid tumors.

    PubMed

    Milo, Lawrence J; Lai, Jack H; Wu, Wengen; Liu, Yuxin; Maw, Hlaing; Li, Youhua; Jin, Zhiping; Shu, Ying; Poplawski, Sarah E; Wu, Yong; Sanford, David G; Sudmeier, James L; Bachovchin, William W

    2011-07-14

    Bortezomib, a dipeptidyl boronic acid and potent inhibitor of the 26S proteasome, is remarkably effective against multiple myeloma (MM) but not against solid tumors. Dose-limiting adverse effects from "on target" inhibition of the proteasome in normal cells and tissues appear to be a key obstacle. Achieving efficacy against solid tumors therefore is likely to require making the inhibitor more selective for tumor tissue over normal tissues. The simplest strategy that might provide such tissue specificity would be to employ a tumor specific protease to release an inhibitor from a larger, noninhibitory structure. However, such release would necessarily generate an inhibitor with a free N-terminal amino group, raising a key question: Can short peptide boronic acids with N-terminal amino groups have the requisite properties to serve as warheads in prodrugs? Here we show that dipeptides of boroLeu, the smallest plausible candidates for the task, can indeed be sufficiently potent, cell-penetrating, cytotoxic, and stable to degradation by cellular peptidases to serve in this capacity. PMID:21634429

  11. Multilayer Hydrophilic Poly(phenol-formaldehyde resin)-Coated Magnetic Graphene for Boronic Acid Immobilization as a Novel Matrix for Glycoproteome Analysis.

    PubMed

    Wang, Jiaxi; Wang, Yanan; Gao, Mingxia; Zhang, Xiangmin; Yang, Pengyuan

    2015-07-29

    Capturing glycopeptides selectively and efficiently from mixed biological samples has always been critical for comprehensive and in-depth glycoproteomics analysis, but the lack of materials with superior capture capacity and high specificity still makes it a challenge. In this work, we introduce a way first to synthesize a novel boronic-acid-functionalized magnetic graphene@phenolic-formaldehyde resin multilayer composites via a facile process. The as-prepared composites gathered excellent characters of large specific surface area and strong magnetic responsiveness of magnetic graphene, biocompatibility of resin, and enhanced affinity properties of boronic acid. Furthermore, the functional graphene composites were shown to have low detection limit (1 fmol) and good selectivity, even when the background nonglycopeptides has a concentration 100 fold higher. Additionally, enrichment efficiency of the composites was still retained after being used repeatedly (at least three times). Better yet, the practical applicability of this approach was evaluated by the enrichment of human serum with a low sample volume of 1 μL. All the results have illustrated that the magG@PF@APB has a great potential in glycoproteome analysis of complex biological samples. PMID:26161682

  12. A non enzymatic glucose biosensor based on an ultrasensitive calix[4]arene functionalized boronic acid gold nanoprobe for sensing in human blood serum.

    PubMed

    Pandya, Alok; Sutariya, Pinkesh G; Menon, Shobhana K

    2013-04-21

    We developed a new, advanced, simple and non enzymatic approach for the colorimetric detection of glucose based on calix[4]arene/phenyl boronic acid (CX-PBA)functionalized gold nanoparticles (AuNPs). This molecular receptor proficiently and selectively recognizes glucose due to its ability to reversibly bind diol-containing compounds. The assembly was characterized by transmission electron micrograph (TEM), dynamic light scattering (DLS), UV-Vis, FT-IR, ESI-MS and (1)H NMR spectrometry, which demonstrates the binding affinity for glucose via a boronic acid-diol interaction. The linear range for glucose was found to be 5-100 nM with phosphate buffer pH 10, with a lower detection limit of 4.3 nM. Interference by other saccharides was negligible. The biosensor has been successfully applied to estimate the glucose in human blood serum samples and the results compared well to an automatic analyzer. With the advantages of high sensitivity, selectivity and low sample volume, this method is potentially suitable for the on-site monitoring of glucose. PMID:23476922

  13. Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

    PubMed

    Pullamsetty, Ashok; Sundara, Ramaprabhu

    2016-10-01

    Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. PMID:27393888

  14. The Effects of Boron Derivatives on Lipid Absorption from the Intestine and on Bile Lipids and Bile Acids of Sprague Dawley Rats

    PubMed Central

    Hall, Iris H.; Reynolds, David J.; Wong, O. T.; Sood, A.; Spielvogel, B. F.

    1995-01-01

    N,N-dimethyl-n-octadecylamine borane 1 at 8 mg/kg/day, tetrakis-u-(trimethylamine boranecarboxylato)-bis(trimethyl-carboxyborane)-dicopper(II) 2 at 2.5 mg/kg/day and trimethylamine-carboxyborane 3 at 8 mg/kg/day were evaluated for their effects on bile lipids, bile acids, small intestinal absorption of cholesterol and cholic acid and liver and small intestinal enzyme activities involved in lipid metabolism. The agent administered orally elevated rat bile excretion of lipids, e.g. cholesterol and phospholipids, and compounds 2 and 3 increased the bile flow rate. These agents altered the composition of the bile acids, but there was no significant increase in lithocholic acid which is most lithogenic agent in rats. The three agents did decrease cholesterol absorption from isolated in situ intestinal duodenum loops in the presence of drug. Hepatic and small intestinal mucosa enzyme activities, e.g. ATP-dependent citrate lyase, acyl CoA cholesterol acyl transferase, cholsterol-7-α -hydroxylase, sn glycerol-3-phosphate acyl transferase, phosphatidylate phosphohydrolase, and lipoprotein lipase, were reduced. However, the boron derivatives 1 and 3 decreased hepatic HMG-CoA reductase activity, the regulatory enzyme for cholesterol synthesis, but the compounds had no effects on small intestinal mucosa HMG-CoA reductase activity. There was no evidence of hepatic cell damage afforded by the drugs based on clinical chemistry values which would induce alterations in bile acid concentrations after treatment of the rat. PMID:18472747

  15. Crystal structures of KPC-2 β-lactamase in complex with 3-nitrophenyl boronic acid and the penam sulfone PSR-3-226.

    PubMed

    Ke, Wei; Bethel, Christopher R; Papp-Wallace, Krisztina M; Pagadala, Sundar Ram Reddy; Nottingham, Micheal; Fernandez, Daniel; Buynak, John D; Bonomo, Robert A; van den Akker, Focco

    2012-05-01

    Class A carbapenemases are a major threat to the potency of carbapenem antibiotics. A widespread carbapenemase, KPC-2, is not easily inhibited by β-lactamase inhibitors (i.e., clavulanic acid, sulbactam, and tazobactam). To explore different mechanisms of inhibition of KPC-2, we determined the crystal structures of KPC-2 with two β-lactamase inhibitors that follow different inactivation pathways and kinetics. The first complex is that of a small boronic acid compound, 3-nitrophenyl boronic acid (3-NPBA), bound to KPC-2 with 1.62-Å resolution. 3-NPBA demonstrated a K(m) value of 1.0 ± 0.1 μM (mean ± standard error) for KPC-2 and blocks the active site by making a reversible covalent interaction with the catalytic S70 residue. The two boron hydroxyl atoms of 3-NPBA are positioned in the oxyanion hole and the deacylation water pocket, respectively. In addition, the aromatic ring of 3-NPBA provides an edge-to-face interaction with W105 in the active site. The structure of KPC-2 with the penam sulfone PSR-3-226 was determined at 1.26-Å resolution. PSR-3-226 displayed a K(m) value of 3.8 ± 0.4 μM for KPC-2, and the inactivation rate constant (k(inact)) was 0.034 ± 0.003 s(-1). When covalently bound to S70, PSR-3-226 forms a trans-enamine intermediate in the KPC-2 active site. The predominant active site interactions are generated via the carbonyl oxygen, which resides in the oxyanion hole, and the carboxyl moiety of PSR-3-226, which interacts with N132, N170, and E166. 3-NPBA and PSR-3-226 are the first β-lactamase inhibitors to be trapped as an acyl-enzyme complex with KPC-2. The structural and inhibitory insights gained here could aid in the design of potent KPC-2 inhibitors. PMID:22330909

  16. Crystal Structures of KPC-2[beta]-Lactamase in Complex with 3-Nitrophenyl Boronic Acid and the Penam Sulfone PSR-3-226

    SciTech Connect

    Ke, Wei; Bethel, Christopher R.; Papp-Wallace, Krisztina M.; Pagadala, Sundar Ram Reddy; Nottingham, Micheal; Fernandez, Daniel; Buynak, John D.; Bonomo, Robert A.; van den Akker, Focco

    2012-08-01

    Class A carbapenemases are a major threat to the potency of carbapenem antibiotics. A widespread carbapenemase, KPC-2, is not easily inhibited by {beta}-lactamase inhibitors (i.e., clavulanic acid, sulbactam, and tazobactam). To explore different mechanisms of inhibition of KPC-2, we determined the crystal structures of KPC-2 with two {beta}-lactamase inhibitors that follow different inactivation pathways and kinetics. The first complex is that of a small boronic acid compound, 3-nitrophenyl boronic acid (3-NPBA), bound to KPC-2 with 1.62-{angstrom} resolution. 3-NPBA demonstrated a Km value of 1.0 {+-} 0.1 {micro}M (mean {+-} standard error) for KPC-2 and blocks the active site by making a reversible covalent interaction with the catalytic S70 residue. The two boron hydroxyl atoms of 3-NPBA are positioned in the oxyanion hole and the deacylation water pocket, respectively. In addition, the aromatic ring of 3-NPBA provides an edge-to-face interaction with W105 in the active site. The structure of KPC-2 with the penam sulfone PSR-3-226 was determined at 1.26-{angstrom} resolution. PSR-3-226 displayed a K{sub m} value of 3.8 {+-} 0.4 {micro}M for KPC-2, and the inactivation rate constant (kinact) was 0.034 {+-} 0.003 s{sup -1}. When covalently bound to S70, PSR-3-226 forms a trans-enamine intermediate in the KPC-2 active site. The predominant active site interactions are generated via the carbonyl oxygen, which resides in the oxyanion hole, and the carboxyl moiety of PSR-3-226, which interacts with N132, N170, and E166. 3-NPBA and PSR-3-226 are the first {beta}-lactamase inhibitors to be trapped as an acyl-enzyme complex with KPC-2. The structural and inhibitory insights gained here could aid in the design of potent KPC-2 inhibitors.

  17. JAGUAR Procedures for Detonation Behavior of Explosives Containing Boron

    NASA Astrophysics Data System (ADS)

    Stiel, Leonard; Baker, Ernest; Capellos, Christos

    2009-06-01

    The JAGUAR product library was expanded to include boron and boron containing products. Relationships of the Murnaghan form for molar volumes and derived properties were implemented in JAGUAR. Available Hugoniot and static volumertic data were analyzed to obtain constants of the Murnaghan relationship for solid boron, boron oxide, boron nitride, boron carbide, and boric acid. Experimental melting points were also utilized with optimization procedures to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX - boron mixtures calculated with these relationships using JAGUAR are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that boron mixtures may exhibit eigenvalue detonation behavior, as observed by aluminized combined effects explosives, with higher detonation velocities than would be achieved by a classical Chapman-Jouguet detonation. Analyses of calorimetric measurements for RDX - boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the energy output obtained from the detonation of the formulation.

  18. Boron doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don; Reynolds, Jeffrey Scott; Brown, Louanne Kay

    1998-06-09

    A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

  19. Boron doping a semiconductor particle

    SciTech Connect

    Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

    1998-06-09

    A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

  20. Suzuki-Miyaura coupling of halophenols and phenol boronic acids: systematic investigation of positional isomer effects and conclusions for the synthesis of phytoalexins from pyrinae.

    PubMed

    Schmidt, Bernd; Riemer, Martin

    2014-05-01

    The Suzuki-Miyaura couplings of o-, m-, and p-halophenols with o-, m-, and p-phenol boronic acids were investigated for all combinations under standardized conditions, using Pd/C as a heterogeneous catalyst and water as a solvent. In the case of iodophenols, conventional heating was used, while for bromophenols significantly better results could be obtained using microwave irradiation. This systematic study revealed that 2,4'-biphenol is particularly difficult to access, irrespective of the starting materials used, but that these difficulties can be overcome by using different additives. The conclusions drawn from this investigation allowed us to identify conditions for the protecting group-free or minimized total synthesis of biaryl-type phytoalexins. These compounds possess antibacterial activity and are produced by fruit trees as a response to microbial infection. PMID:24724893

  1. Boronic acid-containing CXCR1/2 antagonists: Optimization of metabolic stability, in vivo evaluation, and a proposed receptor binding model.

    PubMed

    Maeda, Dean Y; Peck, Angela M; Schuler, Aaron D; Quinn, Mark T; Kirpotina, Liliya N; Wicomb, Winston N; Auten, Richard L; Gundla, Rambabu; Zebala, John A

    2015-06-01

    Blockade of undesired neutrophil migration to sites of inflammation remains an area of substantial pharmaceutical interest. To effect this blockade, a validated therapeutic target is antagonism of the chemokine receptor CXCR2. Herein we report the discovery of 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide 6, an antagonist with activity at both CXCR1 and CXCR2 receptors (IC50 values 31 and 21 nM, respectively). Compound 6 exhibited potent inhibition of neutrophil influx in a rat model of pulmonary inflammation, and is hypothesized to interact with a unique intracellular binding site on CXCR2. Compound 6 (SX-576) is undergoing further investigation as a potential therapy for pulmonary inflammation. PMID:25933594

  2. 3D-QSAR-aided design, synthesis, in vitro and in vivo evaluation of dipeptidyl boronic acid proteasome inhibitors and mechanism studies.

    PubMed

    Lei, Meng; Feng, Huayun; Wang, Cheng; Li, Hailing; Shi, Jingmiao; Wang, Jia; Liu, Zhaogang; Chen, Shanshan; Hu, Shihe; Zhu, Yongqiang

    2016-06-01

    Proteasome had been clinically validated as an effective target for the treatment of cancers. Up to now, many structurally diverse proteasome inhibitors were discovered. And two of them were launched to treat multiple myeloma (MM) and mantle cell lymphoma (MCL). Based on our previous biological results of dipeptidyl boronic acid proteasome inhibitors, robust 3D-QSAR models were developed and structure-activity relationship (SAR) was summarized. Several structurally novel compounds were designed based on the theoretical models and finally synthesized. Biological results showed that compound 12e was as active as the standard bortezomib in enzymatic and cellular activities. In vivo pharmacokinetic profiles suggested compound 12e showed a long half-life, which indicated that it could be administered intravenously. Cell cycle analysis indicated that compound 12e inhibited cell cycle progression at the G2M stage. PMID:27117691

  3. Synthesis, Chemical and Enzymatic Hydrolysis, and Aqueous Solubility of Amino Acid Ester Prodrugs of 3-Carboranyl Thymidine Analogues for Boron Neutron Capture Therapy of Brain Tumors

    PubMed Central

    Hasabelnaby, Sherifa; Goudah, Ayman; Agarwal, Hitesh K.; Abd alla, Mosaad S. M.; Tjarks, Werner

    2012-01-01

    Various water-soluble L-valine-, L-glutamate-, and glycine ester prodrugs of two 3-Carboranyl Thymidine Analogues (3-CTAs), designated N5 and N5-2OH, were synthesized for Boron Neutron Capture Therapy (BNCT) of brain tumors since the water solubilities of the parental compounds proved to be insufficient in preclinical studies. The amino acid ester prodrugs were prepared and stored as hydrochloride salts. The water solubilities of these amino acid ester prodrugs, evaluated in phosphate buffered saline (PBS) at pH 5, pH 6 and pH 7.4, improved 48 to 6600 times compared with parental N5 and N5-2OH. The stability of the amino acid ester prodrugs was evaluated in PBS at pH 7.4, Bovine serum, and Bovine cerebrospinal fluid (CSF). The rate of the hydrolysis in all three incubation media depended primarily on the amino acid promoiety and, to a lesser extend, on the site of esterification at the deoxyribose portion of the 3-CTAs. In general, 3'-amino acid ester prodrugs were less sensitive to chemical and enzymatic hydrolysis than 5'-amino acid ester prodrugs and the stabilities of the latter decreased in the following order: 5'-valine > 5'-glutamate > 5'-glycine. The rate of the hydrolysis of the 5'-amino acid ester prodrugs in Bovine CSF was overall higher than in PBS and somewhat lower than in Bovine serum. Overall, 5'-glutamate ester prodrug of N5 and the 5'-glycine ester prodrugs of N5 and N5-2OH appeared to be the most promising candidates for preclinical BNCT studies. PMID:22889558

  4. Biodistribution and subcellular localization of an unnatural boron-containing amino acid (cis-ABCPC) by imaging secondary ion mass spectrometry for neutron capture therapy of melanomas and gliomas.

    PubMed

    Chandra, Subhash; Barth, Rolf F; Haider, Syed A; Yang, Weilian; Huo, Tianyao; Shaikh, Aarif L; Kabalka, George W

    2013-01-01

    The development of new boron-delivery agents is a high priority for improving the effectiveness of boron neutron capture therapy. In the present study, 1-amino-3-borono-cyclopentanecarboxylic acid (cis-ABCPC) as a mixture of its L- and D-enantiomers was evaluated in vivo using the B16 melanoma model for the human tumor and the F98 rat glioma as a model for human gliomas. A secondary ion mass spectrometry (SIMS) based imaging instrument, CAMECA IMS 3F SIMS Ion Microscope, was used for quantitative imaging of boron at 500 nm spatial resolution. Both in vivo and in vitro studies in melanoma models demonstrated that boron was localized in the cytoplasm and nuclei with some cell-to-cell variability. Uptake of cis-ABCPC in B16 cells was time dependent with a 7.5:1 partitioning ratio of boron between cell nuclei and the nutrient medium after 4 hrs. incubation. Furthermore, cis-ABCPC delivered boron to cells in all phases of the cell cycle, including S-phase. In vivo SIMS studies using the F98 rat glioma model revealed an 8:1 boron partitioning ratio between the main tumor mass and normal brain tissue with a 5:1 ratio between infiltrating tumor cells and contiguous normal brain. Since cis-ABCPC is water soluble and can cross the blood-brain-barrier via the L-type amino acid transporters (LAT), it may accumulate preferentially in infiltrating tumor cells in normal brain due to up-regulation of LAT in high grade gliomas. Once trapped inside the tumor cell, cis-ABCPC cannot be metabolized and remains either in a free pool or bound to cell matrix components. The significant improvement in boron uptake by both the main tumor mass and infiltrating tumor cells compared to those reported in animal and clinical studies of p-boronophenylalanine strongly suggest that cis-ABCPC has the potential to become a novel new boron delivery agent for neutron capture therapy of gliomas and melanomas. PMID:24058680

  5. Biodistribution and Subcellular Localization of an Unnatural Boron-Containing Amino Acid (Cis-ABCPC) by Imaging Secondary Ion Mass Spectrometry for Neutron Capture Therapy of Melanomas and Gliomas

    PubMed Central

    Chandra, Subhash; Barth, Rolf F.; Haider, Syed A.; Yang, Weilian; Huo, Tianyao; Shaikh, Aarif L.; Kabalka, George W.

    2013-01-01

    The development of new boron-delivery agents is a high priority for improving the effectiveness of boron neutron capture therapy. In the present study, 1-amino-3-borono-cyclopentanecarboxylic acid (cis-ABCPC) as a mixture of its L- and D- enantiomers was evaluated in vivo using the B16 melanoma model for the human tumor and the F98 rat glioma as a model for human gliomas. A secondary ion mass spectrometry (SIMS) based imaging instrument, CAMECA IMS 3F SIMS Ion Microscope, was used for quantitative imaging of boron at 500 nm spatial resolution. Both in vivo and in vitro studies in melanoma models demonstrated that boron was localized in the cytoplasm and nuclei with some cell-to-cell variability. Uptake of cis-ABCPC in B16 cells was time dependent with a 7.5:1 partitioning ratio of boron between cell nuclei and the nutrient medium after 4 hrs. incubation. Furthermore, cis-ABCPC delivered boron to cells in all phases of the cell cycle, including S-phase. In vivo SIMS studies using the F98 rat glioma model revealed an 8:1 boron partitioning ratio between the main tumor mass and normal brain tissue with a 5:1 ratio between infiltrating tumor cells and contiguous normal brain. Since cis-ABCPC is water soluble and can cross the blood-brain-barrier via the L-type amino acid transporters (LAT), it may accumulate preferentially in infiltrating tumor cells in normal brain due to up-regulation of LAT in high grade gliomas. Once trapped inside the tumor cell, cis-ABCPC cannot be metabolized and remains either in a free pool or bound to cell matrix components. The significant improvement in boron uptake by both the main tumor mass and infiltrating tumor cells compared to those reported in animal and clinical studies of p-boronophenylalanine strongly suggest that cis-ABCPC has the potential to become a novel new boron delivery agent for neutron capture therapy of gliomas and melanomas. PMID:24058680

  6. Direct current sputtering of boron from boron/boron mixtures

    DOEpatents

    Timberlake, J.R.; Manos, D.; Nartowitz, E.

    1994-12-13

    A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod. 2 figures.

  7. A long-wavelength fluorescent squarylium cyanine dye possessing boronic acid for sensing monosaccharides and glycoproteins with high enhancement in aqueous solution.

    PubMed

    Saito, Shingo; Massie, Tara L; Maeda, Takeshi; Nakazumi, Hiroyuki; Colyer, Christa L

    2012-01-01

    Fluorescence sensing of saccharides and glycoproteins using a boronic acid functionalized squarylium cyanine dye ("SQ-BA") is characterized in terms of synthetic, fluorometric, thermodynamic and kinetic parameters. In our previous work, this newly synthesized dye was successfully applied to the separation and quantification of Gram-positive bacteria by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF); however, the fundamental properties of the dye and its saccharide complexes still required elucidation, as presented in this paper. The dye itself forms nonemissive, soluble aggregates in aqueous solution. With the addition of a monosaccharide, the dye aggregate dissociates to form an emissive monomer accompanied by the formation of a cyclic cis-diol ester with long-wavelength emission (λ(ex) = 630 nm, λ(em) = 660 nm). A very large fluorescence enhancement factor of 18× was observed for the sensing dye as a fructose complex at pH 10, yielding a limit of detection of 10 μM fructose. The relative order of fluorescence enhancement of SQ-BA with other monosaccharides was found to be: fructose > ribose > arabinose ≈ galactose > xylose > mannose > rhamnose > fucose ≈ glucose; and apparent affinity constants of 10(2.80), 10(2.08) and 10(0.86) M(-1) were determined for fructose, ribose and glucose, respectively. Formation of the emissive complexes occurred within minutes, proving the kinetics of the sugar-dye interactions to be suitable for on-column labeling methods in CE-LIF. Furthermore, the sensing dye was successfully applied to glycoproteins, mucin type I-S and type III, which were detected with high sensitivity in batch aqueous solution as a result of the sugar-selective boronic acid-diol esterification as well as hydrophobic interactions. PMID:22778592

  8. A Long-Wavelength Fluorescent Squarylium Cyanine Dye Possessing Boronic Acid for Sensing Monosaccharides and Glycoproteins with High Enhancement in Aqueous Solution

    PubMed Central

    Saito, Shingo; Massie, Tara L.; Maeda, Takeshi; Nakazumi, Hiroyuki; Colyer, Christa L.

    2012-01-01

    Fluorescence sensing of saccharides and glycoproteins using a boronic acid functionalized squarylium cyanine dye (“SQ-BA”) is characterized in terms of synthetic, fluorometric, thermodynamic and kinetic parameters. In our previous work, this newly synthesized dye was successfully applied to the separation and quantification of Gram-positive bacteria by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF); however, the fundamental properties of the dye and its saccharide complexes still required elucidation, as presented in this paper. The dye itself forms nonemissive, soluble aggregates in aqueous solution. With the addition of a monosaccharide, the dye aggregate dissociates to form an emissive monomer accompanied by the formation of a cyclic cis-diol ester with long-wavelength emission (λex = 630 nm, λem = 660 nm). A very large fluorescence enhancement factor of 18× was observed for the sensing dye as a fructose complex at pH 10, yielding a limit of detection of 10 μM fructose. The relative order of fluorescence enhancement of SQ-BA with other monosaccharides was found to be: fructose > ribose > arabinose ≈ galactose > xylose > mannose > rhamnose > fucose ≈ glucose; and apparent affinity constants of 102.80, 102.08 and 100.86 M−1 were determined for fructose, ribose and glucose, respectively. Formation of the emissive complexes occurred within minutes, proving the kinetics of the sugar-dye interactions to be suitable for on-column labeling methods in CE-LIF. Furthermore, the sensing dye was successfully applied to glycoproteins, mucin type I–S and type III, which were detected with high sensitivity in batch aqueous solution as a result of the sugar-selective boronic acid-diol esterification as well as hydrophobic interactions. PMID:22778592

  9. Chronic boron exposure and human semen parameters.

    PubMed

    Robbins, Wendie A; Xun, Lin; Jia, Juan; Kennedy, Nola; Elashoff, David A; Ping, Liu

    2010-04-01

    Boron found as borates in soil, food, and water has important industrial and medical applications. A panel reviewing NTP reproductive toxicants identified boric acid as high priority for occupational studies to determine safe versus adverse reproductive effects. To address this, we collected boron exposure/dose measures in workplace inhalable dust, dietary food/fluids, blood, semen, and urine from boron workers and two comparison worker groups (n=192) over three months and determined correlations between boron and semen parameters (total sperm count, sperm concentration, motility, morphology, DNA breakage, apoptosis and aneuploidy). Blood boron averaged 499.2 ppb for boron workers, 96.1 and 47.9 ppb for workers from high and low environmental boron areas (p<0.0001). Boron concentrated in seminal fluid. No significant correlations were found between blood or urine boron and adverse semen parameters. Exposures did not reach those causing adverse effects published in animal toxicology work but exceeded those previously published for boron occupational groups. PMID:19962437

  10. Characterization of electrodeposited elemental boron

    SciTech Connect

    Jain, Ashish; Anthonysamy, S. Ananthasivan, K.; Ranganathan, R.; Mittal, Vinit; Narasimhan, S.V.; Vasudeva Rao, P.R.

    2008-07-15

    Elemental boron was produced through electrowinning from potassium fluoroborate dissolved in a mixture of molten potassium fluoride and potassium chloride. The characteristics of the electrodeposited boron (raw boron) as well as the water and acid-leached product (processed boron) were studied. The chemical purity, specific surface area, size distribution of particles and X-ray crystallite size of the boron powders were investigated. The morphology of the deposits was examined using scanning electron microscopy (SEM). The chemical state of the matrix, as well as the impurity phases present in them, was established using X-ray photoelectron spectroscopy (XPS). In order to interpret and understand the results obtained, a thermodynamic analysis was carried out. The gas-phase corrosion in the head space as well as the chemistry behind the leaching process were interpreted using this analysis. The ease of oxidation of these powders in air was investigated using differential thermal analysis (DTA) coupled with thermogravimetry (TG). From the results obtained in this study it was established that elemental boron powder with a purity of 95-99% could be produced using a high temperature molten salt electrowinning process. The major impurities were found to be oxygen, carbon, iron and nickel.

  11. Multiwell Assay for the Analysis of Sugar Gut Permeability Markers: Discrimination of Sugar Alcohols with a Fluorescent Probe Array Based on Boronic Acid Appended Viologens.

    PubMed

    Resendez, Angel; Panescu, Priera; Zuniga, Ruth; Banda, Isaac; Joseph, Jorly; Webb, Dominic-Luc; Singaram, Bakthan

    2016-05-17

    With the aim of discerning between different sugar and sugar alcohols of biomedical relevance, such as gut permeability, arrays of 2-component probes were assembled with up to six boronic acid-appended viologens (BBVs): 4,4'-o-BBV, 3,3'-o-BBV, 3,4'-o-BBV, 4,4'-o,m-BBV, 4,7'-o-PBBV, and pBoB, each coupled to the fluorophore 8-hydroxypyrene, 1,3,6-trisulfonic acid trisodium salt (HPTS). These probes were screened for their ability to discriminate between lactulose, l-rhamnose, 3-O-methyl-d-glucose, and xylose. Binding studies of sugar alcohols mannitol, sorbitol, erythritol, adonitol, arabitol, galactitol, and xylitol revealed that diols containing threo-1,2-diol units have higher affinity for BBVs relative diols containing erythro-1,2 units. Those containing both threo-1,2- and 1,3-syn diol motifs showed high affinity for boronic acid binding. Fluorescence from the arrays were examined by principle component analysis (PCA) and linear discriminant analysis (LDA). Arrays with only three BBVs sufficed to discriminate between sugars (e.g., lactulose) and sugar alcohols (e.g., mannitol), establishing a differential probe. Compared with 4,4'-o-BBV, 2-fold reductions in lower limits of detection (LOD) and quantification (LOQ) were achieved for lactulose with 4,7-o-PBBV (LOD 41 μM, LOQ 72 μM). Using a combination of 4,4'-o-BBV, 4,7-o-PBBV, and pBoB, LDA statistically segregated lactulose/mannitol (L/M) ratios from 0.1 to 0.5, consistent with values encountered in small intestinal permeability tests. Another triad containing 3,3'-o-BBV, 4,4'-o-BBV, and 4,7-o-PBBV also discerned similar L/M ratios. This proof-of-concept demonstrates the potential for BBV arrays as an attractive alternate to HPLC to analyze mixtures of sugars and sugar alcohols in biomedical applications and sheds light on structural motifs that make this possible. PMID:27116118

  12. The boron trifluoride nitromethane adduct

    NASA Astrophysics Data System (ADS)

    Ownby, P. Darrell

    2004-02-01

    The separation of the boron isotopes using boron trifluoride·organic-donor, Lewis acid·base adducts is an essential first step in preparing 10B enriched and depleted crystalline solids so vital to nuclear studies and reactor applications such as enriched MgB 2, boron carbide, ZrB 2, HfB 2, aluminum boron alloys, and depleted silicon circuits for radiation hardening and neutron diffraction crystal structure studies. The appearance of this new adduct with such superior properties demands attention in the continuing search for more effective and efficient means of separation. An evaluation of the boron trifluoride nitromethane adduct, its thermodynamic and physical properties related to large-scale isotopic separation is presented. Its remarkably high separation factor was confirmed to be higher than the expected theoretical value. However, the reportedly high acid/donor ratio was proven to be an order of magnitude lower. On-going research is determining the crystal structure of deuterated and 11B enriched 11BF 3·CD 3NO 2 by X-ray and neutron diffraction.

  13. Utilization of Boron Compounds for the Modification of Suberoyl Anilide Hydroxamic Acid as Inhibitor of Histone Deacetylase Class II Homo sapiens

    PubMed Central

    Bakri, Ridla; Parikesit, Arli Aditya; Satriyanto, Cipta Prio; Kerami, Djati; Tambunan, Usman Sumo Friend

    2014-01-01

    Histone deacetylase (HDAC) has a critical function in regulating gene expression. The inhibition of HDAC has developed as an interesting anticancer research area that targets biological processes such as cell cycle, apoptosis, and cell differentiation. In this study, an HDAC inhibitor that is available commercially, suberoyl anilide hydroxamic acid (SAHA), has been modified to improve its efficacy and reduce the side effects of the compound. Hydrophobic cap and zinc-binding group of these compounds were substituted with boron-based compounds, whereas the linker region was substituted with p-aminobenzoic acid. The molecular docking analysis resulted in 8 ligands with ΔGbinding value more negative than the standards, SAHA and trichostatin A (TSA). That ligands were analyzed based on the nature of QSAR, pharmacological properties, and ADME-Tox. It is conducted to obtain a potent inhibitor of HDAC class II Homo sapiens. The screening process result gave one best ligand, Nova2 (513246-99-6), which was then further studied by molecular dynamics simulations. PMID:25214833

  14. Electronic communication of cells with a surface mediated by boronic acid saccharide interactions† †Electronic supplementary information (ESI) available: Experimental detail and supporting figures. See DOI: 10.1039/c5cc04311e Click here for additional data file.

    PubMed Central

    Stephenson-Brown, Alex; Yong, Sue; Mansor, Muhammad H.; Hussein, Zarrar; Yip, Nga-Chi; Mendes, Paula M.; Fossey, John S.

    2015-01-01

    The fabrication of a molecularly tailored surface functionalised with a saccharide binding motif, a phenyl boronic acid derivative is reported. The functionalised surface facilitated the transfer of electrons, via unique electronic interactions mediated by the presence of the boronic acid, from a macrophage cell line. This is the first example of eukaryotic cellular-electrical communication mediated by the binding of cells via their cell–surface saccharide units. PMID:26413585

  15. On-column labeling of gram-positive bacteria with a boronic acid functionalized squarylium cyanine dye for analysis by polymer-enhanced capillary transient isotachophoresis.

    PubMed

    Saito, Shingo; Massie, Tara L; Maeda, Takeshi; Nakazumi, Hiroyuki; Colyer, Christa L

    2012-03-01

    A new asymmetric, squarylium cyanine dye functionalized by boronic acid ("SQ-BA") was designed and synthesized for on-capillary labeling of gram-positive bacteria to provide for high sensitivity detection by way of a modified form of capillary electrophoresis with laser induced fluorescence detection (CE-LIF). The CE-based separation employed a polymer-enhanced buffer with capillary transient isotachophoresis in a new hybrid method dubbed "PectI." It was found that the addition of various monosaccharides to SQ-BA in a batch aqueous solution greatly enhanced the emission of the boronic acid functionalized dye by a factor of up to 18.3 at a long wavelength (λ(ex) = 630 nm, λ(em) = 660 nm) with a high affinity constant (K = ~10(2.80) M(-1)) superior to other sugar probes. Semiempirical quantum mechanics calculations suggest that the mechanism for this high enhancement may involve the dissociation of initially nonemissive dye associates (stabilized by an intramolecular hydrogen bond) upon complex formation with sugars. The fluorescence emission of SQ-BA was also significantly enhanced in the presence of a gram-positive bacterial spore, Bacillus globigii (Bg), which serves as a simulant of B. anthracis (or anthrax) and which possesses a peptidoglycan (sugar)-rich spore coat to provide ample sites for interaction with the dye. Several peaks were observed for a pure Bg sample even with polyethyleneoxide (PEO) present in the CE separation buffer, despite the polymer's previously demonstrated ability to focus microoorganisms to a single peak during migration. Likewise, several peaks were observed for a Bg sample when capillary transient isotachophoresis (ctITP) alone was employed. However, the new combination of these techniques as "PectI" dramatically and reproducibly focused the bacteria to a single peak with no staining procedure. Using PectI, the trace detection of Bg spores (corresponding to approximately three cells per injection) along with separation efficiency

  16. Copper catalyzed N-arylation of amidines with aryl boronic acids and one-pot synthesis of benzimidazoles by a Chan-Lam-Evans N-arylation and C-H activation/C-N bond forming process.

    PubMed

    Li, Jihui; Bénard, Sébastien; Neuville, Luc; Zhu, Jieping

    2012-12-01

    Mono-N-arylation of benzamidines 1 with aryl boronic acids 2 was effectively achieved in the presence of a catalytic amount of Cu(OAc)(2) and NaOPiv under mild aerobic conditions. Combining this step with an intramolecular direct C-H bond functionalization, catalyzed by the same catalytic system but under oxygen at 120 °C, afforded benzimidazoles 3 in good to excellent yields. PMID:23151245

  17. Evolutionary Divergence of Plant Borate Exporters and Critical Amino Acid Residues for the Polar Localization and Boron-Dependent Vacuolar Sorting of AtBOR1.

    PubMed

    Wakuta, Shinji; Mineta, Katsuhiko; Amano, Taro; Toyoda, Atsushi; Fujiwara, Toru; Naito, Satoshi; Takano, Junpei

    2015-05-01

    Boron (B) is an essential micronutrient for plants but is toxic when accumulated in excess. The plant BOR family encodes plasma membrane-localized borate exporters (BORs) that control translocation and homeostasis of B under a wide range of conditions. In this study, we examined the evolutionary divergence of BORs among terrestrial plants and showed that the lycophyte Selaginella moellendorffii and angiosperms have evolved two types of BOR (clades I and II). Clade I includes AtBOR1 and homologs previously shown to be involved in efficient transport of B under conditions of limited B availability. AtBOR1 shows polar localization in the plasma membrane and high-B-induced vacuolar sorting, important features for efficient B transport under low-B conditions, and rapid down-regulation to avoid B toxicity. Clade II includes AtBOR4 and barley Bot1 involved in B exclusion for high-B tolerance. We showed, using yeast complementation and B transport assays, that three genes in S. moellendorffii, SmBOR1 in clade I and SmBOR3 and SmBOR4 in clade II, encode functional BORs. Furthermore, amino acid sequence alignments identified an acidic di-leucine motif unique in clade I BORs. Mutational analysis of AtBOR1 revealed that the acidic di-leucine motif is required for the polarity and high-B-induced vacuolar sorting of AtBOR1. Our data clearly indicated that the common ancestor of vascular plants had already acquired two types of BOR for low- and high-B tolerance, and that the BOR family evolved to establish B tolerance in each lineage by adapting to their environments. PMID:25619824

  18. Enantioselective Synthesis of 1,2-Dihydronaphthalene-1-carbaldehydes by Addition of Boronates to Isochromene Acetals Catalyzed by Tartaric Acid

    PubMed Central

    Luan, Yi; Barbato, Keith S.; Moquist, Philip N.; Kodama, Tomohiro; Schaus, Scott E.

    2015-01-01

    Tartaric acid is an ideal asymmetric catalyst as it is abundant, cheap, and environmentally friendly. (+)-Tartaric acid was found to catalyze a novel enantioselective [4 + 2] cycloaddition of isochromene acetals and vinylboronates. A variety of substituted isochromene acetals were tolerated, furnishing the desired dihydronaphthalenes and dihydrobenzofluorene products in good yields. High enantiomeric ratios (up to 98.5:1.5) and excellent diastereoselectivities (all >99:1) were observed employing 10 mol % of (+)-tartaric acid as the catalyst, in combination with 5 mol % of Ho(OTf)3. PMID:25715172

  19. Organometallic chemistry of ethynyl boronic acid MIDA ester, HC≡CB(O2CCH2)2NMe.

    PubMed

    Hill, Anthony F; Stewart, Craig D; Ward, Jas S

    2015-03-28

    The reactions of HC≡CBMIDA (BMIDA = B(O2CCH2)2NMe) with a range of ruthenium complexes afford the first isolated examples of σ-alkynyl, σ-alkenyl and vinylidene complexes bearing 4-coordinate boron substituents. Specifically, the reactions of HC≡CBMIDA with [RuH(S2CNR2)(CO)(PPh3)2] (R = Me, Et) and [Ru(CO)2(PPh3)3] afford the alkynyl complexes [Ru(C≡CBMIDA)(S2CNR2)(CO)(PPh3)2] and [RuH(C≡CBMIDA)(CO)2(PPh3)2], the latter being converted to [Ru(C≡CBMIDA)Cl(CO)2(PPh3)2] on treatment with chloroform. With [RuCl(dppe)2]PF6 the vinylidene salt [RuCl(=C=CHBMIDA)(dppe)2]PF6 is obtained, which reacts with Et3N to afford the neutral alkynyl derivative [Ru(C≡CBMIDA)Cl(dppe)2]. Hydrometallation of HC≡CBMIDA by [RuHCl(CO)(PPh3)3] affords the coordinatively unsaturated σ-alkenyl complex [RuCl(CH=CHBMIDA)(CO)(PPh3)2] which in turn reacts with CO, CNC6H2Me3-2,4,6, [Et2NH2][S2CNEt2] or K[HB(pz)3] (pz = pyrazol-1-yl) to afford the coordinatively saturated complexes [Ru(CH=CHBMIDA)Cl(CO)2(PPh3)2], [Ru(CH=CHBMIDA)Cl(CO)(CNC6H2Me3)(PPh3)2], [Ru(CH=CHBMIDA)(S2CNEt2)(CO)-(PPh3)2] and [Ru(CH=CHBMIDA)(CO)(PPh3){HB(pz)3}]. In all cases, the transannular N→B dative bond is retained in the BMIDA substituent. PMID:25711678

  20. Modular Attachment of Appended Boron Lewis Acids to a Ruthenium Pincer Catalyst: Metal-Ligand Cooperativity Enables Selective Alkyne Hydrogenation.

    PubMed

    Tseng, Kuei-Nin T; Kampf, Jeff W; Szymczak, Nathaniel K

    2016-08-24

    A new series of bifunctional Ru complexes with pendent Lewis acidic boranes were prepared by late-stage modification of an active hydrogen-transfer catalyst. The appended boranes modulate the reactivity of a metal hydride as well as catalytic hydrogenations. After installing acidic auxiliary groups, the complexes become multifunctional and catalyze the cis-selective hydrogenation of alkynes with higher rates, conversions, and selectivities compared with the unmodified catalyst. PMID:27472301

  1. Synthesis of [18F]Arenes via the Copper-Mediated [18F]Fluorination of Boronic Acids.

    PubMed

    Mossine, Andrew V; Brooks, Allen F; Makaravage, Katarina J; Miller, Jason M; Ichiishi, Naoko; Sanford, Melanie S; Scott, Peter J H

    2015-12-01

    A copper-mediated radiofluorination of aryl- and vinylboronic acids with K(18)F is described. This method exhibits high functional group tolerance and is effective for the radiofluorination of a range of electron-deficient, -neutral, and -rich aryl-, heteroaryl-, and vinylboronic acids. This method has been applied to the synthesis of [(18)F]FPEB, a PET radiotracer for quantifying metabotropic glutamate 5 receptors. PMID:26568457

  2. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W.; Jordan, Kevin; Park, Cheol

    2012-06-06

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  3. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  4. A simple chip free-flow electrophoresis for monosaccharide sensing via supermolecule interaction of boronic acid functionalized quencher and fluorescent dye.

    PubMed

    Yin, Xiao-Yang; Dong, Jing-Yu; Wang, Hou-Yu; Li, Si; Fan, Liu-Yin; Cao, Cheng-Xi

    2013-08-01

    Here, a simple micro free-flow electrophoresis (μFFE) was developed for fluorescence sensing of monosaccharide via supermolecule interaction of synthesized boronic acid functionalized benzyl viologen (ο-BBV) and fluorescent dye. The μFFE contained two open electrode cavities and an ion-exchange membrane was sandwiched between two polymethylmethacrylate plates. The experiments demonstrated the following merits of developed μFFE: (i) up to 90.5% of voltage efficiency due to high conductivity of ion-exchange membrane; (ii) a strong ability against influence of bubble produced in two electrodes due to open design of electrode cavities; and (iii) reusable and washable separation chamber (45 mm × 17 mm × 100 μm, 77 μL) avoiding the discard of μFFE due to blockage of solute precipitation in chamber. Remarkably, the μFFE was first designed for the sensing of monosaccharide via the supermolecule interaction of synthesized ο-BBV, fluorescent dye, and monosaccharide. Under the optimized conditions, the minimum concentration of monosaccharide that could be detected was 1 × 10(-11) M. Finally, the developed device was used for the detection of 0.3 mM glucose spiked in human urine. All of the results demonstrated the feasibility of monosaccharide detection via the μFFE. PMID:23712879

  5. Structure analysis and spectroscopic characterization of 2-Fluoro-3-Methylpyridine-5-Boronic Acid with experimental (FT-IR, Raman, NMR and XRD) techniques and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Alver, Özgür; Dikmen, Gökhan

    2016-03-01

    Possible stable conformers, geometrical molecular structures, vibrational properties as well as band assignments, nuclear magnetic shielding tensors of 2-Fluoro-3-Methylpyridine-5-Boronic Acid (2F3MP5BA) were studied experimentally and theoretically using FT-IR, Raman, (CP/MAS) NMR and XRD spectroscopic methods. FT-IR and Raman spectra were evaluated in the region of 3500-400 cm-1, and 3200-400 cm-1, respectively. The optimized geometric structures, vibrational wavenumbers and nuclear magnetic shielding tensors were examined using Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-311++G(d, p) basis set. 1H, 13C NMR chemical shifts were calculated using the gauge invariant atomic orbital (GIAO) method. 1H, 13C, APT and HETCOR NMR experiments of title molecule were carried out in DMSO solution. 13C CP/MAS NMR measurement was done with 4 mm zirconium rotor and glycine was used as an external standard. Single crystal of 2F3MP5BA was also prepared for XRD measurements. Assignments of vibrational wavenumbers were also strengthened by calculating the total energy distribution (TED) values using scaled quantum mechanical (SQM) method.

  6. Pro-soft Val-boroPro: a strategy for enhancing in vivo performance of boronic acid inhibitors of serine proteases.

    PubMed

    Poplawski, Sarah E; Lai, Jack H; Sanford, David G; Sudmeier, James L; Wu, Wengen; Bachovchin, William W

    2011-04-14

    Val-boroPro, 1, is a potent, but relatively nonspecific inhibitor of the prolyl peptidases. It has antihyperglycemic activity from inhibition of DPPIV but also striking anticancer activity and a toxicity for which the mechanisms are unknown. 1 cyclizes at physiological pH, which attenuates its inhibitory potency >100-fold, which is a "soft drug" effect. Here we show that this phenomenon can be exploited to create prodrugs with unique properties and potential for selective in vivo targeting. Enzyme-mediated release delivers 1 to the target in the active form at physiological pH; cyclization attenuates systemic pharmacological effects from subsequent diffusion. This "pro-soft" design is demonstrated with a construct activated by and targeted to DPPIV, including in vivo results showing improved antihyperglycemic activity and reduced toxicity relative to 1. Pro-soft derivatives of 1 can help to illuminate the mechanisms underlying the three biological activities, or to help localize 1 at a tumor and thereby lead to improved anticancer agents with reduced toxicity. The design concept can also be applied to a variety of other boronic acid inhibitors. PMID:21388136

  7. Methods of forming boron nitride

    SciTech Connect

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  8. Mechanism of Enhanced Electrochemical Oxidation of 2,4-dichlorophenoxyacetic Acid with in situ Microwave Activated Boron-doped Diamond and Platinum Anodes

    NASA Astrophysics Data System (ADS)

    Gao, Junxia; Zhao, Guohua; Liu, Meichuan; Li, Dongming

    2009-09-01

    Remarkable enhancement in degradation effect is achieved at in situ activated boron-doped diamond (BDD) and Pt anodes with different extent through electrochemical oxidation (EC) of 2,4-dichlorophenoxyacetic acid (2,4-D) with microwave (MW) radiation in a flow system. Results show that when EC is activated with MW radiation, the complete mineralization time of 2,4-D at the BDD is reduced quickly from 10 to 4 h while Chemical oxygen demand (COD) removal at Pt is increased from 37.7 to 58.3% at 10 h; the initial current efficiency is both improved about 1.5 times while the pseudo-first-order rate constant is increased by 153 and 119% at the BDD and Pt, respectively. To gain insight into the higher efficiency in microwave activated EC, the mechanism has therefore been systematically evaluated from the essence of electrochemical reaction and the accumulated hydroxyl radical concentration. 2,4-Dichlorophenol, catechol, benquinone, and maleic and oxalic acids are the main intermediates on the Pt anode measured by high performance liquid chromatography (HPLC), while the intermediates on the BDD electrode include 2,4-dichlorophenol, hydroquinone, and maleic and oxalic acids. The reaction pathway with microwave radiation is the same as that in a conventional electrochemical oxidation on both electrodes. While less and lower aromatic intermediates produce at the BDD with MW, which suggests the higher ring-open ratio and the faster oxidation of carboxylic acids. With microwave radiation, the ring-open ratio at the BDD is increased to 98.8% from 85.6%; the value at Pt is increased to 67.3% from 35.9%. So microwave radiation can activate the electrochemical oxidation, which leads to the higher efficiency. This promotion is mainly due to the higher accumulated hydroxyl radical concentration and the effects by microwave radiation. All the results prove that the BDD electrode presents much better mineralization performance with MW. To the best of our knowledge, it is the first

  9. Tandem Cycloisomerization/Suzuki Coupling of Arylethynyl MIDA Boronates

    PubMed Central

    Chan, Julian M. W.; Amarante, Giovanni W.; Toste, F. Dean

    2011-01-01

    A tandem gold-catalyzed cycloisomerization/Suzuki cross coupling sequence involving arylethynyl-N-methyliminodiacetic acid boronates is described. Combining the mildness of homogeneous gold catalysis with the versatility of N-methyliminodiacetic acid (MIDA) boronates, this tandem two-step method enables the rapid assembly of various aryl-substituted heterocycles without having to isolate or purify any heterocyclic MIDA boronate intermediates. Another major advantage of this method is that a wide range of heterocycles bearing different aryl groups may be made from a single MIDA boronate alkyne precursor. PMID:21765556

  10. Biological activity of N(4)-boronated derivatives of 2'-deoxycytidine, potential agents for boron-neutron capture therapy.

    PubMed

    Nizioł, Joanna; Uram, Łukasz; Szuster, Magdalena; Sekuła, Justyna; Ruman, Tomasz

    2015-10-01

    Boron-neutron capture therapy (BNCT) is a binary anticancer therapy that requires boron compound for nuclear reaction during which high energy alpha particles and lithium nuclei are formed. Unnatural, boron-containing nucleoside with hydrophobic pinacol moiety was investigated as a potential BNCT boron delivery agent. Biological properties of this compound are presented for the first time and prove that boron nucleoside has low cytotoxicity and that observed apoptotic effects suggest alteration of important functions of cancer cells. Mass spectrometry analysis of DNA from cancer cells proved that boron nucleoside is inserted into nucleic acids as a functional nucleotide derivative. NMR studies present very high degree of similarity of natural dG-dC base pair with dG-boron nucleoside system. PMID:26344594

  11. Palladium-Catalyzed 1,3-Difunctionalization Using Terminal Alkenes with Alkenyl Nonaflates and Aryl Boronic Acids.

    PubMed

    McCammant, Matthew S; Shigeta, Takashi; Sigman, Matthew S

    2016-04-15

    A Pd-catalyzed 1,3-difunctionalization of terminal alkenes using 1,1-disubstituted alkenyl nonaflates and arylboronic acid coupling partners is reported. This transformation affords allylic arene products that are difficult to selectively access using traditional Heck cross-coupling methodologies. The evaluation of seldom employed 1,1-disubstituted alkenyl nonaflate coupling partners led to the elucidation of subtle mechanistic features of π-allyl stabilized Pd-intermediates. Good stereo- and regioselectivity for the formation of 1,3-addition products can be accessed through a minimization of steric interactions that emanate from alkenyl nonaflate substitution. PMID:27019228

  12. Effect of consumption of fatty acids, calcium, vitamin D and boron with regular physical activity on bone mechanical properties and corresponding metabolic hormones in rats.

    PubMed

    Naghii, M R; Ebrahimpour, Y; Darvishi, P; Ghanizadeh, G; Mofid, M; Torkaman, G; Asgari, A R; Hedayati, M

    2012-03-01

    The consumption of fatty acids, nutrients, and regular physical activity, individually influence bone mechanical properties in rats. To investigate their effects in combination, male rats were divided into the seven groups: G1: regular food and drinking water; G2: same as Gr.1 + physical activity (Whole body vibration; WBV); G3: same as Gr.2 + Calcium, Vit. D, Boron; G4: same as Gr.3 + canola oil; G5: same as Gr.3 + sunflower oil; G6: same as Gr.3 + mix of sunflower oil and canola oil; and G7: same as Gr.3 + coconut oil; and treated for 8 weeks. Analysis between the control with the groups 2 and 3 revealed that vibration in the G2 increased the body weight (P = 0.04), with no other major difference in plasma and bone indices. Comparison between the control with the G4-G7 (the oil groups) revealed that the rats in the G5 had a lower body weight (15 % less) and a significant increase in plasma levels of Estradiol in the G7 was noted. In addition, levels of Testosterone in the G4 and G7, and Free Testosterone in the G7 had a remarkable increase. Similar trend was observed for plasma levels of Vit. D in the G4 and G5. The stiffness and the breaking strength of the femur in the G7, and the breaking strength of the lumbar in the G7 compared to the control and the G4 and G5 was significantly higher and tended to increase in comparison to the G6. Better and stronger measurements observed for coconut oil is warranted to further study its effect on biomechanical properties of bones. PMID:22439438

  13. Novel Insights Into The Mode of Inhibition of Class A SHV-1 Beta-Lactamases Revealed by Boronic Acid Transition State Inhibitors

    SciTech Connect

    W Ke; J Sampson; C Ori; F Prati; S Drawz; C Bethel; R Bonomo; F van den Akker

    2011-12-31

    Boronic acid transition state inhibitors (BATSIs) are potent class A and C {beta}-lactamase inactivators and are of particular interest due to their reversible nature mimicking the transition state. Here, we present structural and kinetic data describing the inhibition of the SHV-1 {beta}-lactamase, a clinically important enzyme found in Klebsiella pneumoniae, by BATSI compounds possessing the R1 side chains of ceftazidime and cefoperazone and designed variants of the latter, compounds 1 and 2. The ceftazidime and cefoperazone BATSI compounds inhibit the SHV-1 {beta}-lactamase with micromolar affinity that is considerably weaker than their inhibition of other {beta}-lactamases. The solved crystal structures of these two BATSIs in complex with SHV-1 reveal a possible reason for SHV-1's relative resistance to inhibition, as the BATSIs adopt a deacylation transition state conformation compared to the usual acylation transition state conformation when complexed to other {beta}-lactamases. Active-site comparison suggests that these conformational differences might be attributed to a subtle shift of residue A237 in SHV-1. The ceftazidime BATSI structure revealed that the carboxyl-dimethyl moiety is positioned in SHV-1's carboxyl binding pocket. In contrast, the cefoperazone BATSI has its R1 group pointing away from the active site such that its phenol moiety moves residue Y105 from the active site via end-on stacking interactions. To work toward improving the affinity of the cefoperazone BATSI, we synthesized two variants in which either one or two extra carbons were added to the phenol linker. Both variants yielded improved affinity against SHV-1, possibly as a consequence of releasing the strain of its interaction with the unusual Y105 conformation.

  14. Boronic acid recognition based-gold nanoparticle-labeling strategy for the assay of sialic acid expression on cancer cell surface by inductively coupled plasma mass spectrometry.

    PubMed

    Zhang, Xing; Chen, Beibei; He, Man; Zhang, Yuan; Peng, Lu; Hu, Bin

    2016-02-01

    Sialic acids are special sugars widely expressed at the termini of glycan chains on the cell surface, and their expression level on the cancer cell surface is much higher than on the normal cell surface. Herein, we reported an inductively coupled plasma mass spectrometry (ICP-MS) based method with elemental tags for the analysis of sialic acids on the cancer cell surface. The method is based on the selective recognition of sialic acids by biotinylated phenylboronic acid (biotin-APBA) at physiological pH and signal enhancement of gold nanoparticles (AuNPs) in ICP-MS when AuNPs were used as elemental tags labeled on biotin-APBA. A specificity test reveals that the proposed method has high specificity towards cancer cells. Taking HepG2 and MCF-7 cells as two model cancer cells, competitive experiments were performed to estimate the expression level of sialic acids on the cancer cell surface, and it was found that the average numbers of sialic acids expressed on the single MCF-7 and HepG2 cell surface were 7.0 × 10(9) and 5.4 × 10(9), respectively. With sialic acid as the biomarker for cancer cells, the method was further used for cell detection. The limits of detection in terms of cell number for HepG2 and MCF-7 cells were 120 and 64, respectively. And the relative standard deviations for nine replicate determinations of ca. 1000 HepG2 and MCF-7 cells were 9.6% and 8.9%, respectively. The linear ranges for HepG2 cells and MCF-7 cells were 300-10 000 and 170-11 000, respectively. The proposed approach is sensitive as well as selective for the analysis of sialic acids on the cancer cell surface, and is potentially applicable for the study of tumor malignancy and metastasis, which is helpful for biological research and clinical diagnostics. PMID:26811850

  15. Selective recognition of protein tetraserine motifs with a cell-permeable, pro-fluorescent bis-boronic acid.

    PubMed

    Halo, Tiffany L; Appelbaum, Jacob; Hobert, Elissa M; Balkin, Daniel M; Schepartz, Alanna

    2009-01-21

    There is considerable interest in novel cell imaging tools that avoid the use of fluorescent proteins. One widely used class of such reagents are "pro-fluorescent" biarsenical dyes such as FlAsH, ReAsH, CrAsH, and Cy3As. Despite their utility, biarsenicals are plagued by high background labeling and cytotoxicity and are challenging to apply in oxidizing cellular locale. Here we demonstrate that [(3-oxospiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3',6'-diyl)bis(iminomethylene-2,1-phenylene)]bis-(9CI), a rhodamine-derived bisboronic acid (RhoBo) described initially as a monosaccharide sensor, functions as a cell-permeable, turn-on fluorescent sensor for tetraserine motifs in recombinant proteins. RhoBo binds peptides or proteins containing Ser-Ser-Pro-Gly-Ser-Ser with affinities in the nanomolar concentration range and prefers this sequence to simple monosaccharides by >10,000-fold. RhoBo fails to form fluorescent complexes with constituents of the mammalian cell surface, as judged by epifluorescent, confocal, and TIRF microscopy, but fluoresces brightly within the Ser-Ser-Pro-Gly-Ser-Ser-rich cell interior. These results suggest that current efforts to identify optimal serine-rich sequences for RhoBo will allow it to function effectively as a selective small-molecule label for appropriately tagged proteins either upon or within living cells. PMID:19105691

  16. Boron nitride converted carbon fiber

    DOEpatents

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  17. Chemical disposition of boron in animals and humans.

    PubMed Central

    Moseman, R F

    1994-01-01

    Elemental boron was isolated in 1808. It typically occurs in nature as borates hydrated with varying amounts of water. Important compounds are boric acid and borax. Boron compounds are also used in the production of metals, enamels, and glasses. In trace amounts, boron is essential for the growth of many plants, and is found in animal and human tissues at low concentrations. Poisoning in humans has been reported as the result of accidental ingestion or use of large amounts in the treatment of burns. Boron as boric acid is fairly rapidly absorbed and excreted from the body via urine. The half-life of boric acid in humans is on the order of 1 day. Boron does not appear to accumulate in soft tissues of animals, but does accumulate in bone. Normal levels of boron in soft tissues, urine, and blood generally range from less than 0.05 ppm to no more than 10 ppm. In poisoning incidents, the amount of boric acid in brain and liver tissue has been reported to be as high as 2000 ppm. Recent studies at the National Institute of Environmental Health Sciences have indicated that boron may contribute to reduced fertility in male rodents fed 9000 ppm of boric acid in feed. Within a few days, boron levels in blood and most soft tissues quickly reached a plateau of about 15 ppm. Boron in bone did not appear to plateau, reaching 47 ppm after 7 days on the diet. Cessation of exposure to dietary boron resulted in a rapid drop in bone boron.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7889870

  18. A highly selective turn-on fluorescent probe for hypochlorous acid based on hypochlorous acid-induced oxidative intramolecular cyclization of boron dipyrromethene-hydrazone.

    PubMed

    Chen, Wei-Chieh; Venkatesan, Parthiban; Wu, Shu-Pao

    2015-07-01

    A BODIPY-based fluorescent probe, HBP, was developed for the detection of hypochlorous acid based on the specific hypochlorous acid-promoted oxidative intramolecular cyclization of heterocyclic hydrazone in response to the amount of HOCl. The reaction is accompanied by a 41-fold increase in the fluorescent quantum yield (from 0.004 to 0.164). The fluorescence intensity of the reaction between HOCl and HBP is linear in the HOCl concentration range of 1-8 μM with a detection limit of 2.4 nM (S/N=3). Confocal fluorescence microscopy imaging using RAW264.7 cells showed that the new probe HBP could be used as an effective fluorescent probe for detecting HOCl in living cells. PMID:26043093

  19. An application of polymer-enhanced capillary transient isotachophoresis with an emissive boronic acid functionalized squarylium dye as an on-capillary labeling agent for gram-positive bacteria.

    PubMed

    Saito, Shingo; Maeda, Takeshi; Nakazumi, Hiroyuki; Colyer, Christa L

    2013-01-01

    In this paper, the characterization and application of the "PectI" (polymer-enhanced capillary transient isotachophoresis) technique for the separation and detection of same genus, gram-positive bacteria, Bacillus globigii (Bg) and Bacillus subtilis, is demonstrated by employing a boronic acid-functionalized squarylium dye (SQ-BA) as an on-capillary labeling agent, including the quantitative performance and applicability to crude samples. The effect of borate in the separation buffer was also investigated, which revealed that borate strongly affects the separation behavior of bacteria. PMID:23303103

  20. Excellent electrical conductivity of the exfoliated and fluorinated hexagonal boron nitride nanosheets

    PubMed Central

    2013-01-01

    The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demonstrate a typical semiconductor characteristic which were studied on a new scanning tunneling microscope-transmission electron microscope holder. Since this property changes from an insulator to a semiconductor of the boron nitride, these nanosheets will be able to extend their applications in designing and fabricating electronic nanodevices. PMID:23347409

  1. Excellent electrical conductivity of the exfoliated and fluorinated hexagonal boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Xue, Yafang; Liu, Qian; He, Guanjie; Xu, Kaibing; Jiang, Lin; Hu, Xianghua; Hu, Junqing

    2013-01-01

    The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demonstrate a typical semiconductor characteristic which were studied on a new scanning tunneling microscope-transmission electron microscope holder. Since this property changes from an insulator to a semiconductor of the boron nitride, these nanosheets will be able to extend their applications in designing and fabricating electronic nanodevices.

  2. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

    2015-05-01

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

  3. Characterization of a Gene Encoding Clathrin Heavy Chain in Maize Up-Regulated by Salicylic Acid, Abscisic Acid and High Boron Supply

    PubMed Central

    Zeng, Mu-Heng; Liu, Sheng-Hong; Yang, Miao-Xian; Zhang, Ya-Jun; Liang, Jia-Yong; Wan, Xiao-Rong; Liang, Hong

    2013-01-01

    Clathrin, a three-legged triskelion composed of three clathrin heavy chains (CHCs) and three light chains (CLCs), plays a critical role in clathrin-mediated endocytosis (CME) in eukaryotic cells. In this study, the genes ZmCHC1 and ZmCHC2 encoding clathrin heavy chain in maize were cloned and characterized for the first time in monocots. ZmCHC1 encodes a 1693-amino acid-protein including 29 exons and 28 introns, and ZmCHC2 encodes a 1746-amino acid-protein including 28 exons and 27 introns. The high similarities of gene structure, protein sequences and 3D models among ZmCHC1, and Arabidopsis AtCHC1 and AtCHC2 suggest their similar functions in CME. ZmCHC1 gene is predominantly expressed in maize roots instead of ubiquitous expression of ZmCHC2. Consistent with a typical predicted salicylic acid (SA)-responsive element and four predicted ABA-responsive elements (ABREs) in the promoter sequence of ZmCHC1, the expression of ZmCHC1 instead of ZmCHC2 in maize roots is significantly up-regulated by SA or ABA, suggesting that ZmCHC1 gene may be involved in the SA signaling pathway in maize defense responses. The expressions of ZmCHC1 and ZmCHC2 genes in maize are down-regulated by azide or cold treatment, further revealing the energy requirement of CME and suggesting that CME in plants is sensitive to low temperatures. PMID:23880865

  4. Boron control system for a nuclear power plant

    SciTech Connect

    Brown, W.W.; Van der Schoot, M.R.

    1980-09-30

    Ion exchangers which reversibly store borate ions in a temperature dependent process are combined with evaporative boric acid recovery apparatus to provide a boron control system for controlling the reactivity of nuclear power plants. A plurality of ion exchangers are operated sequentially to provide varying amounts of boric acid to a nuclear reactor for load follow operations. Evaporative boric acid recovery apparatus is utilized for major changes in the boron concentration within the nuclear reactor.

  5. Effect of combination therapy of fatty acids, calcium, vitamin D and boron with regular physical activity on cardiovascular risk factors in rat.

    PubMed

    Naghii, M R; Darvishi, P; Ebrahimpour, Y; Ghanizadeh, G; Mofid, M; Hedayati, M; Asgari, A R

    2012-01-01

    The effect of consumption of fatty acids and selected nutrients, along with regular physical activity, on cardiovascular risk factors in rats was investigated.Male rats were divided into the seven groups: Group 1: regular food and drinking water, Group 2: same as Group. 1 + physical activity (whole body vibration; WBV), Group 3: same as Group. 2 + calcium, vitamin D, boron, Group 4: same as Group. 3 + canola oil, Group 5: same as Group. 3 + sunflower oil, Group 6: same as Group. 3 + mix of sunflower oil and canola oil, Group 7: same as Group. 3 + coconut oil. Rats were treated for 8 weeks, and analysis of the frozen plasmas was performed. A- Analysis between the treatment groups and control revealed that vibration training in Group 2 increased body weight (P = 0.04), plasma creatin kinase (CK), (P = 0.02), and estradiol (E2), (P = 0.03). Rats in Group 5 consumed less food and plasma levels of cholesterol and LDL-cholesterol (LDL-C) increased significantly (P = 0.02) in Group 6 and in Group 7 (p<0.05). B- Analysis of data among Group 4 - 7 (the oil consuming groups) and Group 3 revealed significant differences in cholesterol (Chol), LDL-C, HDL-cholesterol (HDL-C), triglycerides (TG), C- reactive protein (hs-CRP), estradiol (E2), atherogenic index (AI), and risk factor (RF), (p<0.05). In addition, plasma levels of testosterone (T) and free testosterone (FT) in Group 7 had a remarkable but non-significant increase. As a result of vibration training, a similar trend was observed for vitamin D in Group 2-7. The findings show that WBV is effective in improving health status by influencing cardiovascular disease (CVD) risk factors. Moreover, canola oil and sunflower oil, separately, showed beneficial impacts on CVD risk factors; whereas their combination had negative impacts on lipid profile. Coconut oil revealed to be efficient to provide health benefits in terms of CVD treatments. PMID:22277894

  6. Boronic Acid Transition State Inhibitors Active against KPC and Other Class A β-Lactamases: Structure-Activity Relationships as a Guide to Inhibitor Design.

    PubMed

    Rojas, Laura J; Taracila, Magdalena A; Papp-Wallace, Krisztina M; Bethel, Christopher R; Caselli, Emilia; Romagnoli, Chiara; Winkler, Marisa L; Spellberg, Brad; Prati, Fabio; Bonomo, Robert A

    2016-03-01

    Boronic acid transition state inhibitors (BATSIs) are competitive, reversible β-lactamase inhibitors (BLIs). In this study, a series of BATSIs with selectively modified regions (R1, R2, and amide group) were strategically designed and tested against representative class A β-lactamases of Klebsiella pneumoniae, KPC-2 and SHV-1. Firstly, the R1 group of compounds 1a to 1c and 2a to 2e mimicked the side chain of cephalothin, whereas for compounds 3a to 3c, 4a, and 4b, the thiophene ring was replaced by a phenyl, typical of benzylpenicillin. Secondly, variations in the R2 groups which included substituted aryl side chains (compounds 1a, 1b, 1c, 3a, 3b, and 3c) and triazole groups (compounds 2a to 2e) were chosen to mimic the thiazolidine and dihydrothiazine ring of penicillins and cephalosporins, respectively. Thirdly, the amide backbone of the BATSI, which corresponds to the amide at C-6 or C-7 of β-lactams, was also changed to the following bioisosteric groups: urea (compound 3b), thiourea (compound 3c), and sulfonamide (compounds 4a and 4b). Among the compounds that inhibited KPC-2 and SHV-1 β-lactamases, nine possessed 50% inhibitory concentrations (IC50s) of ≤ 600 nM. The most active compounds contained the thiopheneacetyl group at R1 and for the chiral BATSIs, a carboxy- or hydroxy-substituted aryl group at R2. The most active sulfonamido derivative, compound 4b, lacked an R2 group. Compound 2b (S02030) was the most active, with acylation rates (k2/K) of 1.2 ± 0.2 × 10(4) M(-1) s(-1) for KPC-2 and 4.7 ± 0.6 × 10(3) M(-1) s(-1) for SHV-1, and demonstrated antimicrobial activity against Escherichia coli DH10B carrying blaSHV variants and blaKPC-2 or blaKPC-3 and against clinical strains of Klebsiella pneumoniae and E. coli producing different class A β-lactamase genes. At most, MICs decreased from 16 to 0.5 mg/liter. PMID:26729496

  7. Lipase-catalyzed highly enantioselective kinetic resolution of boron-containing chiral alcohols.

    PubMed

    Andrade, Leandro H; Barcellos, Thiago

    2009-07-16

    The first application of enzymes as catalysts to obtain optically pure boron compounds is described. The kinetic resolution of boron-containing chiral alcohols via enantioselective transesterification catalyzed by lipases was studied. Aromatic, allylic, and aliphatic secondary alcohols containing a boronate ester or boronic acid group were resolved by lipase from Candida antartica (CALB), and excellent E values (E > 200) and high enantiomeric excesses (up to >99%) of both remaining substrates and acetylated product were obtained. PMID:19552446

  8. Benzodipyrrole-based Donor-Acceptor-type Boron Complexes as Tunable Near-infrared-Absorbing Materials.

    PubMed

    Nakamura, Tomoya; Furukawa, Shunsuke; Nakamura, Eiichi

    2016-07-20

    Benzodipyrrole-based donor-acceptor boron complexes were designed and synthesized as near-infrared-absorbing materials. The electron-rich organic framework combined with the Lewis acidic boron co-ordination enabled us to tune the LUMO energy level and the HOMO-LUMO gap (i.e.,the absorption wavelength) by changing the organic acceptor units, the number of boron atoms, and the substituents on the boron atoms. PMID:27311060

  9. Fabrication of boron articles

    DOEpatents

    Benton, Samuel T.

    1976-01-01

    This invention is directed to the fabrication of boron articles by a powder metallurgical method wherein the articles are of a density close to the theoretical density of boron and are essentially crackfree. The method comprises the steps of admixing 1 to 10 weight percent carbon powder with amorphous boron powder, cold pressing the mixture and then hot pressing the cold pressed compact into the desired article. The addition of the carbon to the mixture provides a pressing aid for inhibiting the cracking of the hot pressed article and is of a concentration less than that which would cause the articles to possess significant concentrations of boron carbide.

  10. Boron-based nanostructures: Synthesis, functionalization, and characterization

    NASA Astrophysics Data System (ADS)

    Bedasso, Eyrusalam Kifyalew

    Boron-based nanostructures have not been explored in detail; however, these structures have the potential to revolutionize many fields including electronics and biomedicine. The research discussed in this dissertation focuses on synthesis, functionalization, and characterization of boron-based zero-dimensional nanostructures (core/shell and nanoparticles) and one-dimensional nanostructures (nanorods). The first project investigates the synthesis and functionalization of boron-based core/shell nanoparticles. Two boron-containing core/shell nanoparticles, namely boron/iron oxide and boron/silica, were synthesized. Initially, boron nanoparticles with a diameter between 10-100 nm were prepared by decomposition of nido-decaborane (B10H14) followed by formation of a core/shell structure. The core/shell structures were prepared using the appropriate precursor, iron source and silica source, for the shell in the presence of boron nanoparticles. The formation of core/shell nanostructures was confirmed using high resolution TEM. Then, the core/shell nanoparticles underwent a surface modification. Boron/iron oxide core/shell nanoparticles were functionalized with oleic acid, citric acid, amine-terminated polyethylene glycol, folic acid, and dopamine, and boron/silica core/shell nanoparticles were modified with 3-(amino propyl) triethoxy silane, 3-(2-aminoethyleamino)propyltrimethoxysilane), citric acid, folic acid, amine-terminated polyethylene glycol, and O-(2-Carboxyethyl)polyethylene glycol. A UV-Vis and ATR-FTIR analysis established the success of surface modification. The cytotoxicity of water-soluble core/shell nanoparticles was studied in triple negative breast cancer cell line MDA-MB-231 and the result showed the compounds are not toxic. The second project highlights optimization of reaction conditions for the synthesis of boron nanorods. This synthesis, done via reduction of boron oxide with molten lithium, was studied to produce boron nanorods without any