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941.
Holsclaw CM Muse WB Carroll KS Leary JA 《International journal of mass spectrometry》2011,305(2-3):151-156
Mycothiol (MSH), the primary low-molecular weight thiol produced in mycobacteria, acts to protect the cell from oxidative stress and to maintain redox homeostasis, notably in the pathogenic Mycobacterium tuberculosis in the course of human infection. The mycothiol disulfide reductase (Mtr) enzyme reduces the oxidized form of mycothiol, mycothione (MSSM), back to MSH, however its role in bacterial viability is not clear. In this study, we sought to determine the MSH levels of wild-type (WT) and Mtr mutant mycobacteria during oxidative stress. We describe a rapid method for the relative quantification of MSH using high-sensitivity mass spectrometry (MS) with selected ion monitoring (SIM). This method uses only minimal sample cleanup, and does not require advanced chromatographic equipment or fluorescent compounds. MSH levels decreased in the Mtr mutant only upon treatment with peroxide, and the results were consistent between our method and previously-described thiol quantification methods. Our results indicate that our MS-based method is a useful, high-throughput alternative tool for the quantification of MSH from mycobacteria. 相似文献
942.
943.
Ross J. Ellis Yannick Meridiano Renato Chiarizia Laurence Berthon Julie Muller Laurent Couston Mark R. Antonio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2663-2675
Trends in lanthanide(III) (LnIII) coordination were investigated within nanoconfined solvation environments. LnIII ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n‐heptane by contact with aqueous phases containing nitrate and LnIII; both insert into pre‐organized RM units built up of DMDOHEMA (N,N′‐dimethyl‐N,N′‐dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the LnIII complex formation and the RM morphology were obtained by use of XAS (X‐ray absorption spectroscopy) and SAXS (small‐angle X‐ray scattering). The LnIII coordination environments were determined through use of L3‐edge XANES (X‐ray absorption near edge structure) and EXAFS (extended X‐ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time‐resolved laser‐induced fluorescence spectroscopy). The picture that emerges from a system‐wide perspective of the Ln? O interatomic distances and number of coordinating oxygen atoms for the extracted complexes of LnIII in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9 O for early lanthanides to 8 O for the late ones—a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to LnIII. These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither equivalent to the solid nor bulk solution behaviors. Herein we address atomic‐ and mesoscale phenomena in the under‐explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chemistry of growing importance in technologies as diverse as nanosynthesis and separations science. 相似文献
944.
945.
Jean-Mary Simone Fran?ois Loiseau David Carcache Pavel Bobal Julie Jeanneret-Gris Reinhard Neier 《Monatshefte für Chemie / Chemical Monthly》2007,29(3):141-147
A malonylation/decarbalkoxylation sequence from 2-substituted furans was investigated in view of developing a scalable synthesis
of hydrophobic nonactic acid analogues. 相似文献
946.
The relationship of in-silico predicted physical/chemical properties and human toxicity is analyzed for a statistically significant sample size of chemical compounds. Results for compounds with known toxicity endpoints, as designated by EPA's Toxic Release Inventory (TRI), are compared to a series of commercial chemicals that are not regulated under TRI. Physical properties for all compounds are predicted using Schrodinger's QikProp, an established tool for predicting adsorption, distribution, metabolism, and excretion (ADME) characteristics. The results of this analysis indicate that the physical/chemical property distributions of TRI chemicals are statistically significantly different from those of bulk commercial chemicals, particularly related to properties associated with bioavailability. Using a partitioning analysis, several key physical/chemical properties and ranges are identified that can be used to readily differentiate TRI chemical characteristics from those of bulk commercial chemicals. 相似文献
947.
Protein adsorption onto capillary wall often hampers CE separations, particularly in the CZE mode. Electrostatic interactions are not the only factors affecting adsorption, as hydrophobic interactions and/or protein conformational changes are also involved in the adsorption phenomenon. Numerous methods can be used to reduce or avoid adsorption, such as (i) addition of low molecular weight molecules in the BGE, (ii) use of surfactants, or (iii) capillary coatings. However, most of these methods are not MS-compatible. In this study, we evaluated the addition of organic solvent as an alternative MS-compatible method to decrease protein adsorption. The effect of the solvent addition was emphasized using classical methods for estimating reversible and irreversible adsorption. In many cases, organic solvents were effective at decreasing adsorption. However, the influence of the organic solvent on protein adsorption should be evaluated case-by-case in CE method development. 相似文献
948.
This paper discusses the experience of a preservice secondary mathematics teacher during lesson study. Although the preservice teacher was a strong undergraduate mathematics student, she used compensation “moves” to deflect attention away from her insecurities about her conceptual understanding of secondary mathematics. She feared being labeled as “dumb” and redirected conversations in order to protect her identity as a knower of mathematics. This paper investigates the culture in which preservice teachers develop confidence in their personal mathematics knowledge and how that confidence may influence behavior. 相似文献
949.
950.
Condensation of 1,3-diamines with aldehydes or ketones gives rise to two major products, the hexahydropyrimidine and the bisimine. Experimental studies of the reaction between a range of aromatic aldehydes and 1,3-diaminopropane or 1,3-diamino-2-propanol establish that the hexahydropyrimidine is favoured by the less nucleophilic amine and by the presence of electron withdrawing groups on the aryl ring of the aldehyde. Calculations indicate that the electronic nature of this aryl ring substituent influences both the relative thermodynamic stability of the final products and the reactivity of the aldehyde as an electrophile. 相似文献