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  • 1
    Article
    Article
    Language: English
    In: Mythlore, Fall-Winter, 2013, Vol.32(1), p.21(13)
    Keywords: English Literature ; Twentieth Century ; Authors ; Tolkien, J. R. R ; The Lord of the Rings ; Fairies ; Trees ; Languages & Literatures;
    ISSN: 0146-9339
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  • 2
    Language: English
    In: Journal of Chromatography A, 2010, Vol.1217(4), pp.540-549
    Description: The addition of the homologous series of perfluorinated acids-trifluoroacetic acid (TFAA), pentafluoropropionic acid (PFPA), heptafluorobutyric acid (HFBA) to mobile phases for reversed-phase high-performance liquid chromatography (RP-HPLC) of β-blockers was tested. Acidic modifiers were responsible for acidification of mobile phase (pH 3) ensuring the protonation of the β-blockers and further ion pairs creation. The effect of the type and concentration of mobile phase additives on retention parameters, the efficiency of the peaks, their symmetry and separation selectivity of the β-blockers mixture were all studied. It appeared that at increasing acid concentration, the retention factor, for all compounds investigated, increased to varying degrees. It should be stressed that the presence of acids more significantly affected the retention of the most hydrophobic β-blockers. Differences in hydrophobicity of drugs can be maximized through variation of the hydrophobicity of additives. Thus, the relative increase in the retention depends on either concentration and hydrophobicity of the anionic mobile phase additive or hydrophobicity of analytes. According to QSRR (quantitative structure retention relationship) methodology, chromatographic lipophilicity parameters: isocratic log and log values (extrapolated retention to pure water) were correlated with the molecular (log ) and apparent (log ) octanol–water partition coefficients obtained experimentally by countercurrent chromatography (CCC) or predicted by Pallas software. The obtained, satisfactory retention-hydrophobicity correlations indicate that, in the case of the basic drugs examined in RP-HPLC systems modified with perfluorinated acids, the retention is mainly governed by their hydrophobicity.
    Keywords: Β-Blockers ; Perfluorinated Acids ; Rp-Hplc ; Selectivity ; Retention Hydrophobicity Relationships ; Chemistry
    ISSN: 0021-9673
    E-ISSN: 18733778
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  • 3
    Language: English
    In: Food Chemistry, Jan 1, 2015, Vol.166, p.150(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.foodchem.2014.06.037 Byline: J. Flieger, A. Czajkowska-A'elazko Abstract: acents Use of ionic liquids for aqueous two phase system (ATP) creation. acents Extraction of quinine from human plasma sample by ATP system. acents Influence of ionic liquid components for improvement of recovery. acents Optimisation and validation of ATP and HPLC. acents Quantification of quinine in plasma after drinking of tonic water. Article History: Received 18 August 2013; Revised 24 February 2014; Accepted 8 June 2014
    ISSN: 0308-8146
    Source: Cengage Learning, Inc.
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  • 4
    Article
    Article
    Language: English
    In: Malahat Review, Summer, 2011, Issue 175, p.73(9)
    ISSN: 0025-1216
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Journal of Chromatography A, 18 April 2014, Vol.1338, pp.188-196
    Description: A chromatographic and thermodynamic study of the derivatives of 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazole-3-thiones (and their Mannich bases) was undertaken. Three reversed-phase materials: a Zorbax Extend-C18, Cogent UDC Cholesterol and Regis IAM. PC. DD. 2 were studied. Plots of log vs. the volume fraction of organic solvent in the mobile phase ( ) and the van’t Hoff relationships were constructed. The van’t Hoff plots revealed at least one phase transition on Cogent UDC Cholesterol and Regis IAM. PC. DD. 2. Obtained results indicated that adsorption was enthalpy–entropy driven. Cholesterol phase and Regis IAM. PC. DD. 2 in contrast to conventional octadecyl silica phase at aqueous-organic mobile phase demonstrated some liquid crystals behavior at defined conditions.
    Keywords: Hplc ; Zorbax Extend-C18 ; Cogent Udc Cholesterol ; Regis Iam. PC. DD. 2 ; Chromatographic Study ; Thermodynamic Study ; Antiepileptic Compounds ; Chemistry
    ISSN: 0021-9673
    E-ISSN: 18733778
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  • 6
    Language: English
    In: Food chemistry, 01 January 2015, Vol.166, pp.150-7
    Description: Aqueous two phase system was applied for selective extraction of quinine from human plasma. Bi-phase was constructed from ionic liquid: butyl-methyl-imidazolium chloride after addition kosmotropic salts K₃PO₄ or KH₂PO₄. Quinine was determined in plasma samples after drinking of tonic containing quinine. Determination was performed by HPLC on 5-μm Zorbax SB-CN column and eluent containing 40% acetonitrile (v/v), 20 mM phosphate buffer at pH 3 and 40 mM NaPF₆ using external standard method. The spectrophotometric detection was set λ=214 nm. Selective fluorescence detection was performed at excitation of 325 nm and emission of 375 nm. Proposed strategy provides suitable sample purification and gives extraction yields in the range of 89-106%. The determination coefficient (R(2)) has a value ≥0.997 in the range of 50-800 ng/ml quinine concentration. The limit of quantification was set at 27.9 ng/ml and the detection limit was found to be 8.4 ng/ml under fluorescence detection.
    Keywords: Chaotropic Effect ; Human Plasma ; Ionic Liquids ; Quinine ; Chromatography, High Pressure Liquid -- Methods ; Ionic Liquids -- Chemistry ; Quinine -- Blood
    ISSN: 03088146
    E-ISSN: 1873-7072
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  • 7
    Language: English
    In: Physical Review B, 12/2013, Vol.88(24)
    Description: By ab initio based tight-binding calculations, we show that nontrivial electronic states exist at an interface of a [scriptF] topological insulator and a topological crystalline insulator. At the exemplary (111) interface between Bi sub(2) Te sub(3) and SnTe, the two Dirac surface states at the Brillouin zone center [Gamma] annihilate upon approaching the semi-infinite subsystems but one topologically protected Dirac surface state remains at each time-reversal invariant momentum M. This leads to a highly conducting spin-momentum-locked channel at the interface but insulating bulk regions. For the Sb sub(2) Te sub(3)/Bi sub(2) Te sub(3) interface, we find complete annihilation of Dirac states because both subsystems belong to the same topology class. Our proof of principle may have impact on planar electric transport in future spintronics devices with topologically protected conducting channels.
    Keywords: Channels ; Invariants ; Topology ; Crystal Structure ; Insulators ; Conduction ; Condensed Matter ; Mathematical Analysis ; Condensed Matter Physics (General) (So) ; Electronics and Communications Milieux (General) (Ea) ; Solid-State Physics (Ah);
    ISSN: 1098-0121
    E-ISSN: 1550-235X
    Source: American Physical Society (APS) (via CrossRef)
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  • 8
    Language: English
    In: Physical Review B, 9/2014, Vol.90(12)
    Description: The electronic structure of Bi sub(2) Te sub(3) covered by noble metals is investigated by first-principles calculations. The Dirac surface state of the topological insulator Bi sub(2) Te sub(3) hybridizes with the sp states of the noble metal, which gives rise to strong reorganization of the surface electronic structure. Striking features of the modified Dirac surface state are (i) the introduction of new Dirac points within the fundamental band gap of Bi sub(2) Te sub(3), (ii) a very weak dispersion, and (iii) a multisheeted Fermi surface which results in an orientation-dependent number of conducting channels in the fundamental band gap of Bi sub(2) Te sub(3). Our findings have impact for spin-dependent surface transport.
    Keywords: Dispersions ; Channels ; Noble Metals ; Topology ; Electronic Structure ; Covering ; Insulators ; Condensed Matter ; Mathematical Analysis ; Condensed Matter Physics (General) (So) ; Solid-State Physics (Ah);
    ISSN: 1098-0121
    E-ISSN: 1550-235X
    Source: American Physical Society (APS) (via CrossRef)
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  • 9
    Language: English
    In: The Journal of biological chemistry, 04 July 2014, Vol.289(27), pp.18657-66
    Description: The intracellularly replicating lung pathogen Legionella pneumophila consists of an extraordinary variety of phospholipases, including at least 15 different phospholipases A (PLA). Among them, PlaB, the first characterized member of a novel lipase family, is a hemolytic virulence factor that exhibits the most prominent PLA activity in L. pneumophila. We analyzed here protein oligomerization, the importance of oligomerization for activity, addressed further essential regions for activity within the PlaB C terminus, and the significance of PlaB-derived lipolytic activity for L. pneumophila intracellular replication. We determined by means of analytical ultracentrifugation and small angle x-ray scattering analysis that PlaB forms homodimers and homotetramers. The C-terminal 5, 10, or 15 amino acids, although the individual regions contributed to PLA activity, were not essential for protein tetramerization. Infection of mouse macrophages with L. pneumophila wild type, plaB knock-out mutant, and plaB complementing or various mutated plaB-harboring strains showed that catalytic activity of PlaB promotes intracellular replication. We observed that PlaB was most active in the lower nanomolar concentration range but not at or only at a low level at concentration above 0.1 μm where it exists in a dimer/tetramer equilibrium. We therefore conclude that PlaB is a virulence factor that, on the one hand, assembles in inactive tetramers at micromolar concentrations. On the other hand, oligomer dissociation at nanomolar concentrations activates PLA activity. Our data highlight the first example of concentration-dependent phospholipase inactivation by tetramerization, which may protect the bacterium from internal PLA activity, but enzyme dissociation may allow its activation after export.
    Keywords: Bacteria ; Enzyme Purification ; Pathogenesis ; Phospholipase A ; Protein Structure ; Protein Multimerization ; Legionella Pneumophila -- Enzymology ; Phospholipases -- Chemistry
    E-ISSN: 1083-351X
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  • 10
    Language: English
    In: The Journal of biological chemistry, 06 July 2012, Vol.287(28), pp.23464-78
    Description: Enzymes secreted by Legionella pneumophila, such as phospholipases A (PLAs) and glycerophospholipid:cholesterol acyltransferases (GCATs), may target host cell lipids and therefore contribute to the establishment of Legionnaires disease. L. pneumophila possesses three proteins, PlaA, PlaC, and PlaD, belonging to the GDSL family of lipases/acyltransferases. We have shown previously that PlaC is the major GCAT secreted by L. pneumophila and that the zinc metalloproteinase ProA is essential for GCAT activity. Here we characterized the mode of PlaC GCAT activation and determined that ProA directly processes PlaC. We further found that not only cholesterol but also ergosterol present in protozoa was palmitoylated by PlaC. Such ester formations were not induced by either PlaA or PlaD. PlaD was shown here to possess lysophospholipase A activity, and interestingly, all three GDSL enzymes transferred short chain fatty acids to sterols. The three single putative catalytic amino acids (Ser-37, Asp-398, and His-401) proved essential for all PlaC-associated PLA, lysophospholipase A, and GCAT activities. A further four cysteine residues are important for the PLA/GCAT activities as well as their oxidized state, and we therefore conclude that PlaC likely forms at least one disulfide loop. Analysis of cleavage site and loop deletion mutants suggested that for GCAT activation deletion of several amino acids within the loop is necessary rather than cleavage at a single site. Our data therefore suggest a novel enzyme inhibition/activation mechanism where a disulfide loop inhibits PlaC GCAT activity until the protein is exported to the external space where it is ProA-activated.
    Keywords: Acyltransferases -- Metabolism ; Bacterial Proteins -- Metabolism ; Legionella Pneumophila -- Enzymology ; Metalloproteases -- Metabolism
    E-ISSN: 1083-351X
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