Enumeration of non-labile oxygen atoms in dissolved organic matter by use of 16O/18O exchange and Fourier transform ion-cyclotron resonance mass spectrometry

We report a simple approach for enumeration of non-labile oxygen atoms in individual molecules of dissolved organic matter (DOM), using acid-catalyzed ¹⁶O/¹⁸O exchange and ultrahigh-resolution Fourier-transform ion-cyclotron-resonance mass spectrometry (FTICR-MS). We found that by dissolving DOM in H₂ ¹⁸O at 95 °C for 20 days it is possible to replace all oxygen atoms of DOM molecules (excluding oxygen from ether groups) with ¹⁸O. The number of exchanges in each molecule can be determined using high-resolution FTICR. Using the proposed method we identified the number of non-labile oxygen atoms in 231 molecules composing DOM. Also, using a previously developed hydrogen–deuterium (H/D)-exchange approach we identified the number of labile hydrogen atoms in 450 individual molecular formulas. In addition, we observed that several backbone hydrogen atoms can be exchanged for deuterium under acidic conditions. The method can be used for structural and chemical characterization of individual DOM molecules, comparing different DOM samples, and investigation of biological pathways of DOM in the environment.     

Directed synthesis and immunoactive properties of (2-hydroxyethyl)ammonium salts of 1-R-indol-3-ylsulfanyl(sulfonyl)alkanecarboxylic acids

A general method for the synthesis of 1-alkyl(allyl)(benzyl)-substituted (indol-3-yl)-sulfanylalkanecarboxylic acids and hexane-1,6-diyl(1,4-phenylenemethylene)bisindol-3-ylsulfanylalkanecarboxylic acids from the corresponding N-substituted indoles and bisindoles, thiourea, iodine, and halogencarboxylic acids was developed. The oxidation of substituted (indol-3-yl)sulfanylalkanecarboxylic acids for the first time afforded their analogs containing the sulfonyl group. New (2-hydroxyethyl)ammonium salts of 1-R-indol-3-ylsulfanyl(sulfonyl)-alkanecarboxylic acids, which are structural analogs of highly active immunomodulators of indacetamin and VILIM, were synthesized. Among the studied (2-hydroxyethyl)ammonium salts of 1-R-indol-3-ylsulfanylacetic and -sulfonylalkanecarboxylic acids, the compounds exhibiting high dose-dependent antiproliferative activity by the ability to affect the spontaneous and mitogen-stimulated splenocyte proliferation of mice in vitro were found.     

Application of NMR Spectroscopy and Imaging in Heterogeneous Biocatalysis

Heterogeneously catalyzed enzymatic glucose isomerization was considered as a model process to extend the application of nuclear magnetic resonance (NMR) and magnetic resonance imaging techniques to the studies of biocatalytic processes and heterogeneous biocatalysts. It has been demonstrated that the T ₂ times of glucose are different for its aqueous solution in the pores of an unmodified porous support and in a heterogeneous biocatalyst, comprising bacterial cells immobilized on the same support. This observation has been used to map the spatial distribution of the active component within a packed bed of biocatalyst in a model reactor. ¹³C NMR spectroscopy was applied to follow the progress of glucose isomerization catalyzed by the heterogeneous biocatalyst in a batch reactor. The utilization of proton spin decoupling and nuclear Overhauser effect was shown to be necessary to obtain high signal-to-noise ratio in the natural abundance ¹³C NMR spectra of a glucose–fructose syrup present in the packed bed of biocatalyst. The spectra thus obtained were suitable for the quantification of the glucose-to-fructose ratio achieved in the biocatalytic reaction.     

On finite critical lattices

Critical lattices are considered, i.e., lattices without nontrivial endomorphisms and not containing nontrivial proper sublattices without nontrivial endomorphisms. It is proved that there exist n-element critical sublattices for any n ≥ 21.     

Synthesis of Nanostructured Carbon on Ni Deposited on Mesoporous Aluminum,and Titanium Oxides. Investigation of Biocatalytic Properties of Lipase Adsorbed on Carbon–Mineral Supports

This work is a continuation of the studies devoted to the synthesis of nanostructured carbon (NSC) as a result of the pyrolysis of a mixture of H₂ + C₃–C₄ alkanes on supported Ni catalysts. Mesoporous alumina (γ-Al₂O₃) and titania (TiO₂), on which Ni(II) compounds are deposited by impregnation or homogeneous precipitation, are studied as carriers. Using the methods of thermogravimetric analysis and scanning electron microscopy, it is shown that the activity of Ni catalysts (carbon yield) and the morphology of synthesized NSC are largely determined by the chemical nature of the support. It is found that the synthesis of NSC in the form of carbon nanofibers with a pronounced filamentary structure proceeds only on a Ni catalyst supported on titanium dioxide. The mesoporous carbon–mineral supports obtained after catalytic pyrolysis were studied in the adsorptive immobilization of the enzyme such as Thermomyces lanuginosus lipase. The adsorption properties of the supports, as well as the enzymatic activity and stability of the prepared biocatalysts in the esterification of saturated fatty acids (capric, C10: 0) with aliphatic alcohols (isopentanol, C₅) in the non-aqueous media of organic solvents (hexane and diethyl ether) at ambient temperature, are studied. Biocatalysts prepared by lipase adsorption on NSC/TiO₂ show the maximum esterification activity of 100 EA/g, which is 20–45 times higher than the activity of lipase adsorbed on NSC/Al₂O₃.     

Quantitative and qualitative precision improvements by effective mobility-scale data transformation in capillary electrophoresis analysis

By transforming the time-based x-axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility-scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (mu eff-scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity-based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the mu eff-scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time-scale integration.     

Enzymatic esterification of saturated fatty acids with aliphatic alcohols as an alternative method of a low-temperature synthesis of esters

Russian Chemical Bulletin - low-temperature synthesis of saturated fatty acid esters with aliphatic alcohols by enzymatic esterification in the presence of heterogeneous biоcatalysts was...     

Combined utilization of ion mobility and ultra‐high‐resolution mass spectrometry to identify multiply charged constituents in natural organic matter

Natural organic matter as complex biogeochemical non‐repetitive material was investigated with ion mobility mass spectrometry (IMS) and ultra‐high‐resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS) approaches in order to unravel the existence of multiply charged state constituents. Hereby we describe and assign the potential molecular formulae of these doubly charged species, derived from FTICR‐MS, and the existence of these species was confirmed via IMS. The parallel application of these powerful techniques enabled the boundaries of the understanding of natural organic matter to be pushed further. Copyright © 2009 John Wiley & Sons, Ltd.