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The Journal of Clinical Investigation Sep 1985Cortical collecting ducts (CCD) from rabbits treated with deoxycorticosterone (DOC) actively secrete bicarbonate at high rates. To investigate the mechanism of...
Cortical collecting ducts (CCD) from rabbits treated with deoxycorticosterone (DOC) actively secrete bicarbonate at high rates. To investigate the mechanism of bicarbonate secretion, we measured bicarbonate and chloride transport in CCD from rabbits treated with DOC for 9-24 d. Removal of chloride (replaced with gluconate) from both perfusate and bath inhibited bicarbonate secretion without changing transepithelial voltage. Removal of chloride only from the bath increased bicarbonate secretion, while removal of chloride only from the perfusate inhibited secretion. In contrast to the effect of removing chloride, removal of sodium from both the perfusate and bath (replacement with N-methyl-D-glucamine) did not change the rate of bicarbonate secretion. The rate of bicarbonate secretion equaled the rate of chloride absorption in tubules bathed with 0.1 mM ouabain to inhibit any cation-dependent chloride transport. Under these conditions, chloride absorption occurred against an electrochemical gradient. Removal of bicarbonate from both the perfusate and bath inhibited chloride absorption. Removal of bicarbonate only from the bath inhibited chloride absorption, while removal of bicarbonate from the lumen stimulated chloride absorption. We conclude that CCD from DOC-treated rabbits actively secrete bicarbonate and actively absorb chloride by an electroneutral mechanism involving 1:1 chloride/bicarbonate exchange. The process is independent of sodium.
Topics: Absorption; Animals; Bicarbonates; Biological Transport, Active; Carbon Dioxide; Chlorides; Desoxycorticosterone; Epithelium; Female; Kidney Cortex; Kidney Tubules; Kidney Tubules, Collecting; Rabbits; Sodium
PubMed: 3930570
DOI: 10.1172/JCI112067 -
Acta Crystallographica. Section E,... Nov 2015The title compounds, (N-methyl-N-phenyl-amino)(N-methyl-N-phenyl-car-bam-oyl)sulfide, C15H16N2OS, (I), and...
The title compounds, (N-methyl-N-phenyl-amino)(N-methyl-N-phenyl-car-bam-oyl)sulfide, C15H16N2OS, (I), and (N-methyl-N-phenyl-amino)-(N-methyl-N-phenyl-carbamo-yl)disulfane, C15H16N2OS2, (II), are stable derivatives of (chloro-carbon-yl)sulfenyl chloride and (chloro-carbon-yl)disulfanyl chloride, respectively. The torsion angle about the S-S bond in (II) is -92.62 (6)°, which is close to the theoretical value of 90°. In the crystal of (II), non-classical inter-molecular C-H⋯O hydrogen bonds form centrosymmetric cyclic dimers [graph set R 2 (2)(10)], while inter-dimer C-H⋯S inter-actions generate chains extending along the b axis.
PubMed: 26594513
DOI: 10.1107/S2056989015018289 -
Materials Today. Bio Sep 2020Nucleic acids are relevant biopolymers in therapy and diagnosis, for which their purity and biological activity are of crucial relevance. However, these features are...
Nucleic acids are relevant biopolymers in therapy and diagnosis, for which their purity and biological activity are of crucial relevance. However, these features are difficult to achieve by cost-effective methods. Herein, we report the functionalization of a macroporous chromatographic support functionalized with an ionic liquid (IL) with remarkable performance to purify nucleic acids. An initial screening with distinct IL chemical structures supported in silica was carried out, allowing to identify the IL 1-methyl-3-propylimidazolium chloride as the most promising ligand. A chromatographic macroporous matrix able to be used in preparative liquid chromatography was then functionalized and binding/elution studies were performed. The IL 1-methyl-3-propylimidazolium chloride acts as a multimodal ligand with a remarkable dynamic binding capacity. This macroporous support allows the (one-step) purification of nucleic acids, namely small RNAs, ribosomal RNA, and genomic DNA, from a bacterial lysate, and can be regenerated and reused without compromising its separation performance.
PubMed: 33319188
DOI: 10.1016/j.mtbio.2020.100086 -
The Journal of Physical Chemistry. B Nov 2020The H NMR spectra of 10 mole fraction solutions of 1-decyl-3-methyl-imidazolium chloride ionic liquid in water, acetonitrile, and dichloromethane have been measured. The...
The H NMR spectra of 10 mole fraction solutions of 1-decyl-3-methyl-imidazolium chloride ionic liquid in water, acetonitrile, and dichloromethane have been measured. The chemical shift of the proton at position 2 in the imidazolium ring of 1-decyl-3-methyl-imidazolium (H2) is rather different for all three samples, reflecting the shifting equilibrium between the contact pairs and free fully solvated ions. Classical molecular dynamics simulations of the 1-decyl-3-methyl-imidazolium chloride contact ion pair as well as of free ions in water, acetonitrile, and dichloromethane have been conducted, and the quantum mechanics/molecular mechanics methods have been applied to predict NMR chemical shifts for the H2 proton. The chemical shift of the H2 proton was found to be primarily modulated by hydrogen bonding with the chloride anion, while the influence of the solvents-though differing in polarity and capabilities for hydrogen bonding-is less important. By comparing experimental and computational results, we deduce that complete disruption of the ionic liquid into free ions takes place in an aqueous solution. Around 23% of contact ion pairs were found to persist in acetonitrile. Ion-pair breaking into free ions was predicted not to occur in dichloromethane.
PubMed: 33183008
DOI: 10.1021/acs.jpcb.0c07450 -
The Journal of Physical Chemistry. B Jun 2011Recent years have seen tremendous effort in the development of approaches with which to obtain quantum mechanics/molecular mechanics (QM/MM) free energies for reactions...
Recent years have seen tremendous effort in the development of approaches with which to obtain quantum mechanics/molecular mechanics (QM/MM) free energies for reactions in the condensed phase. Nevertheless, there remain significant challenges to address, particularly, the high computational cost involved in performing proper configurational sampling and, in particular, in obtaining ab initio QM/MM (QM(ai)/MM) free-energy surfaces. One increasingly popular approach that seems to offer an ideal way to progress in this direction is the elegant metadynamics (MTD) approach. However, in the current work, we point out the subtle efficiency problems associated with this approach and illustrate that we have at hand what is arguably a more powerful approach. More specifically, we demonstrate the effectiveness of an updated version of our original idea of using a classical reference potential for QM(ai)/MM calculations [J. Phys. Chem. 1995, 99, 17516)], which we refer to as paradynamics (PD). This approach is based on the use of an empirical valence bond (EVB) reference potential, which is already similar to the real ab initio potential. The reference potential is fitted to the ab initio potential by an iterative and, to a great degree, automated refinement procedure. The corresponding free-energy profile is then constructed using the refined EVB potential, and the linear response approximation (LRA) is used to evaluate the QM(ai)/MM activation free-energy barrier. The automated refinement of the EVB surface (and thus the reduction of the difference between the reference and ab initio potentials) is a key factor in accelerating the convergence of the LRA approach. We apply our PD approach to a test reaction, namely, the S(N)2 reaction between a chloride ion and methyl chloride, and demonstrate that, at present, this approach is far more powerful and cost-effective than the metadynamics approach (at least in its current implementation). We also discuss the general features of the PD approach in terms of its ability to explore complex systems and clarify that it is not a specialized approach limited to only accelerating QM(ai)/MM calculations with proper sampling, but rather can be used in a wide variety of applications. In fact, we point out that the use of a reference (CG) potential coupled with its PD refinement, as well as our renormalization approach, provides very general and powerful strategies that can be used very effectively to explore any property that has been studied by the MTD approach.
Topics: Models, Molecular; Quantum Theory; Thermodynamics
PubMed: 21618985
DOI: 10.1021/jp201217b -
Current Biology : CB Oct 2003Methyl chloride (CH(3)Cl) and methyl bromide (CH(3)Br) are the primary carriers of natural chlorine and bromine, respectively, to the stratosphere, where they catalyze... (Comparative Study)
Comparative Study
Methyl chloride (CH(3)Cl) and methyl bromide (CH(3)Br) are the primary carriers of natural chlorine and bromine, respectively, to the stratosphere, where they catalyze the destruction of ozone, whereas methyl iodide (CH(3)I) influences aerosol formation and ozone loss in the boundary layer. CH(3)Br is also an agricultural pesticide whose use is regulated by international agreement. Despite the economic and environmental importance of these methyl halides, their natural sources and biological production mechanisms are poorly understood. Besides CH(3)Br fumigation, important sources include oceans, biomass burning, tropical plants, salt marshes, and certain crops and fungi. Here, we demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides and that the enzyme primarily responsible for the production is encoded by the HARMLESS TO OZONE LAYER (HOL) gene. The encoded protein belongs to a group of methyltransferases capable of catalyzing the S-adenosyl-L-methionine (SAM)-dependent methylation of chloride (Cl(-)), bromide (Br(-)), and iodide (I(-)) to produce methyl halides. In mutant plants with the HOL gene disrupted, methyl halide production is largely eliminated. A phylogenetic analysis with the HOL gene suggests that the ability to produce methyl halides is widespread among vascular plants. This approach provides a genetic basis for understanding and predicting patterns of methyl halide production by plants.
Topics: Amino Acid Sequence; Arabidopsis; Blotting, Northern; Chromosome Mapping; Hydrocarbons, Brominated; Hydrocarbons, Iodinated; Methyl Chloride; Methylation; Methyltransferases; Molecular Sequence Data; Phylogeny
PubMed: 14561407
DOI: 10.1016/j.cub.2003.09.055 -
Synthesis of Oxidant Functionalised Cationic Polymer Hydrogel for Enhanced Removal of Arsenic (III).Gels (Basel, Switzerland) Nov 2021A cationic polymer gel (-[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary)(DMAPAA-Q gel)-supported oxidising agent (KMnO or KCrO) was proposed to remove...
A cationic polymer gel (-[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary)(DMAPAA-Q gel)-supported oxidising agent (KMnO or KCrO) was proposed to remove As from water. The gel could adsorb arsenite, As(III), and arsenate, As(V), through the ion exchange method, where the oxidising agent oxidised As(III) to As(V). theoretically speaking, the amount of oxidant in the gels can reach 73.7 Mol%. The maximal adsorption capacity of the D-Mn gel (DMAPAA-Q gel carrying MnO) and D-Cr gel (DMAPAA-Q gel carrying CrO) for As(III) could reach 200 mg g and 263 mg g, respectively; moreover, the As(III) removal rate of the gels could still be maintained above 85% in a neutral or weak acid aquatic solution. Studies on the kinetic and adsorption isotherms indicated that the As adsorption by the D-Mn and D-Cr gels was dominated by chemisorption. The thermodynamic parameters of adsorption confirmed that the adsorption was an endothermic process. The removal of As is influenced by the co-existing high-valence anions. Based on these results, the gels were found to be efficient for the As(III) adsorption and could be employed for the As(III) removal from the industrial wastewater.
PubMed: 34842691
DOI: 10.3390/gels7040197 -
Acta Crystallographica. Section E,... Feb 2012The asymetric unit of the title salt, 3CH(5)N(2)S(+)·3Cl(-)·2CH(4)N(2)S, contains two mol-ecules of thio-urea, three (diamino-methyl-idene)sulfonium cations and three...
The asymetric unit of the title salt, 3CH(5)N(2)S(+)·3Cl(-)·2CH(4)N(2)S, contains two mol-ecules of thio-urea, three (diamino-methyl-idene)sulfonium cations and three chloride anions. The crystal packing is stabilized by N-H⋯Cl, N-H⋯S, S-H⋯Cl and S-H⋯S hydrogen bonds, forming a three-dimensional network.
PubMed: 22346903
DOI: 10.1107/S1600536811052809 -
Journal of Bacteriology Jul 2012Besides acetogenic bacteria, only Desulfitobacterium has been described to utilize and cleave phenyl methyl ethers under anoxic conditions; however, no ether-cleaving...
Besides acetogenic bacteria, only Desulfitobacterium has been described to utilize and cleave phenyl methyl ethers under anoxic conditions; however, no ether-cleaving O-demethylases from the latter organisms have been identified and investigated so far. In this study, genes of an operon encoding O-demethylase components of Desulfitobacterium hafniense strain DCB-2 were cloned and heterologously expressed in Escherichia coli. Methyltransferases I and II were characterized. Methyltransferase I mediated the ether cleavage and the transfer of the methyl group to the superreduced corrinoid of a corrinoid protein. Desulfitobacterium methyltransferase I had 66% identity (80% similarity) to that of the vanillate-demethylating methyltransferase I (OdmB) of Acetobacterium dehalogenans. The substrate spectrum was also similar to that of the latter enzyme; however, Desulfitobacterium methyltransferase I showed a higher level of activity for guaiacol and used methyl chloride as a substrate. Methyltransferase II catalyzed the transfer of the methyl group from the methylated corrinoid protein to tetrahydrofolate. It also showed a high identity (∼70%) to methyltransferases II of A. dehalogenans. The corrinoid protein was produced in E. coli as cofactor-free apoprotein that could be reconstituted with hydroxocobalamin or methylcobalamin to function in the methyltransferase I and II assays. Six COG3894 proteins, which were assumed to function as activating enzymes mediating the reduction of the corrinoid protein after an inadvertent oxidation of the corrinoid cofactor, were studied with respect to their abilities to reduce the recombinant reconstituted corrinoid protein. Of these six proteins, only one was found to catalyze the reduction of the corrinoid protein.
Topics: Cloning, Molecular; Corrinoids; Desulfitobacterium; Escherichia coli; Methyltransferases; Operon; Oxidoreductases, O-Demethylating; Recombinant Proteins; Substrate Specificity
PubMed: 22522902
DOI: 10.1128/JB.00146-12 -
Acta Crystallographica. Section E,... Jul 2009In the structure of the title compound, [CoCl(2)(C(9)H(16)N(2)Si)(2)], the Co(II) atom is located on an inversion center in a slightly distorted tetra-hedral environment...
In the structure of the title compound, [CoCl(2)(C(9)H(16)N(2)Si)(2)], the Co(II) atom is located on an inversion center in a slightly distorted tetra-hedral environment formed by two chloride ions and the pyridine N atoms of two chelating 6-methyl-2-[(trimethyl-silyl)amino]pyridine ligands. The dihedral angle between the planes of the pyridine rings is 80.06 (5)°. Cohesion within the crystal structure is accomplished by N-H⋯Cl hydrogen bonds.
PubMed: 21583404
DOI: 10.1107/S1600536809027937