Regression algorithm for calculating second-dimension retention indices in comprehensive two-dimensional gas chromatography.

Gas chromatography-mass spectrometry (GC-MS) is one of the most accurate, well developed, and reliable analytical tools for the analysis of volatile and semivolatile compounds. The GC-MS data have been extensively improved by enhancing the separation capacity via comprehensive two-dimensional gas chromatography (GC × GC). The reliability of the identification of the analytes in GC × GC-MS can be notably improved by applying the second-dimension retention index (2I) as additional analytical parameter along with the commonly used first dimension retention index (1I) and mass spectrum. A novel approach for calculating second-dimension retention indices (2I) for semivolatile organic compounds is proposed. It is noteworthy that the standards used in calculations are the same compounds recommended as internal standards by US EPA 8270 Method for analysis of semivolatile organic compounds. The new algorithm takes into account the analyte retention time and its retention temperature at the secondary column, (2tR) and (2TR), respectively. The experimental data collected with different primary oven temperature ramp rates and carrier gas flow rates have shown that the calculated by the proposed approach 2I values remain the same for each evaluated compound, drifting in a very narrow range. The proposed approach was tested using 100 organic compounds from various chemical classes including alkanes, phenols, nitrobenzenes, chlorinated hydrocarbons, anilines, polycyclic aromatic hydrocarbons (PAHs), phthalates, etc. The important advantage of the proposed 2I values for compounds of the same chemical origin (reference standards and analytes) involves applicability of well-known Lee's indices for non-polar phases. Therefore, the proposed approach can be used in targeted and non-targeted analysis of a wide range of organic compounds. The reduced version of the second dimension retention indices provides a valuable mapping of the homologues series of organic compounds, making their detection and identification easy and reliable.

Detection of semi-volatile compounds in cloud waters by GC×GC-TOF-MS. Evidence of phenols and phthalates as priority pollutants.

Although organic species are transported and efficiently transformed in clouds, more than 60% of this organic matter remains unspeciated. Using GCxGC-HRMS technique we were able to detect and identify over 100 semi-volatile compounds in 3 cloud samples collected at the PUY station (puy de Dôme mountain, France) while they were present at low concentrations in a very small sample volume (<25 mL of cloud water). The vast majority (∼90%) of the detected compounds was oxygenated, while the absence of halogenated organic compounds should be specially mentioned. This could reflect both the oxidation processes in the atmosphere (gas and water phase) but also the need of the compounds to be soluble enough to be transferred and dissolved in the cloud droplets. Furans, esters, ketones, amides and pyridines represent the major classes of compounds demonstrating a large variety of potential pollutants. Beside these compounds, priority pollutants from the US EPA list were identified and quantified. We found phenols (phenol, benzyl alcohol, p-cresole, 4-ethylphenol, 3,4-dimethylphenol, 4-nitrophenol) and dialkylphthalates (dimethylphthalate, diethylphthalate, di-n-butylphthalate, bis-(2-ethylhexyl)-phthalate, butylbenzylphthalate, di-n-octyl phthalate). In general, the concentrations of phthalates (from 0.09 to 52 µg L-1) were much higher than those of phenols (from 0.03 to 0.74 µg L-1). To our knowledge phthalates in clouds are described here for the first time. We investigated the variability of phenols and phthalates concentrations with cloud air mass origins (marine vs continental) and seasons (winter vs summer). Although both factors seem to have an influence, it is difficult to deduce general trends; further work should be conducted on large series of cloud samples collected in different geographic areas and at different seasons.

Semi volatile organic compounds in the snow of Russian Arctic islands: Archipelago Novaya Zemlya.

Environmental contamination of the Arctic has widely been used as a worldwide pollution marker. Various classes of organic pollutants such as pesticides, personal care products, PAHs, flame retardants, biomass burning markers, and many others emerging contaminants have been regularly detected in Arctic samples. Although numerous papers have been published reporting data from the Canadian, Danish, and Norwegian Arctic regions, the environmental situation in Russian Arctic remains mostly underreported. Snow analysis is known to be used for monitoring air pollution in the regions with cold climate in both short-term and long-term studies. This paper presents the results of a nontargeted study on the semivolatile organic compounds detected and identified in snow samples collected at the Russian Artic Archipelago Novaya Zemlya in June 2016. Gas chromatography coupled to a high-resolution time-of-flight mass spectrometer enabled the simultaneous detection and quantification of a variety of pollutants including those from the US Environmental Protection Agency (EPA) priority pollutants list, emerging contaminants (plasticizers, flame retardants-only detection), as well as the identification of novel Arctic organic pollutants, (e.g., fatty acid amides and polyoxyalkanes). The possible sources of these novel pollutants are also discussed. GC-HRMS enabled the detection and identification of emerging contaminants and novel organic pollutants in the Arctic, e.g., fatty amides and polyoxyalkanes.

Matrix Metalloproteinases MMP-1 and MMP-9 and Their Inhibitor TIMP-1 as Markers of Dilated Cardiomyopathy in Patients of Different Age.

We studied the expression of MMP-2, MMP-9, and inhibitor TIMP-1 in myocardial autopsy samples from subjects of different age and in cardiomyocyte cultures in the norm and in dilated cardiomyopathy. In autopsy samples of normal myocardium and in cardiomyocyte cultures, expression of molecules involved in extracellular matrix remodeling did not change during aging. In dilation cardiomyopathy, expression of MMP-2, MMP-9, and TIMP-1 and their ratios in autopsy material and in cultures was elevated by 1.5-9 times. Remodeling of extracellular matrix plays an important role in the pathogenesis of dilated cardiomyopathy. MMP-2, MMP-9, and their inhibitor TIMP-1 and the MMP/TIMP ratios can be regarded as promising predictors of dilated cardiomyopathy and used for evaluation of the effectiveness of treatment of this conditions in patients of different ages.

Novel pollutants in the Moscow atmosphere in winter period: Gas chromatography-high resolution time-of-flight mass spectrometry study.

The most common mass spectrometry approach analyzing contamination of the environment deals with targeted analysis, i.e. detection and quantification of the selected (priority) pollutants. However non-targeted analysis is becoming more often the method of choice for environmental chemists. It involves implementation of modern analytical instrumentation allowing for comprehensive detection and identification of the wide variety of compounds of the environmental interest present in the sample, such as pharmaceuticals and their metabolites, musks, nanomaterials, perfluorinated compounds, hormones, disinfection by-products, flame retardants, personal care products, and many others emerging contaminants. The paper presents the results of detection and identification of previously unreported organic compounds in snow samples collected in Moscow in March 2016. The snow analysis allows evaluation of long-term air pollution in the winter period. Gas chromatography coupled to a high resolution time-of-flight mass spectrometer has enabled us with capability to detect and identify such novel analytes as iodinated compounds, polychlorinated anisoles and even Ni-containing organic complex, which are unexpected in environmental samples. Some considerations concerning the possible sources of origin of these compounds in the environment are discussed.

Mutation of Lys-75 affects calmodulin conformation.

Some properties of synthetic calmodulin and its five mutants with replacement of Lys-75 were analyzed by means of electrophoresis, limited proteolysis and MALDI mass-spectrometry. A double mutant of calmodulin containing insert KGK between residues 80 and 81 and replacement of Lys-75 by Pro has a highly flexible central helix which is susceptible to trypsinolysis in the presence of Ca2+. Two mutants, K75P and K75E, having a distorted central helix demonstrate high resistance to trypsinolysis in the absence of Ca2+. Arg-90 and Arg-106 being the primary site of trypsinolysis of synthetic calmodulin are partially-protected in K75P and K75E mutants. The central helix of K75A and K75V mutants is stabilized by hydrophobic interactions between residues located in positions 71, 72 and 75. In the presence of Ca2+, the central helix of K75V is resistant to trypsinolysis. Mutations K75A and K75V decrease the rate of trypsinolysis of the central helix with a simultaneous increase of the rate of trypsinolysis in the C-terminal domain of calmodulin. It is concluded that the point mutation in the central helix has a long distance effect on the structure of calmodulin.

Participation of chaperonin GroEL in the folding of D-glyceraldehyde-3-phosphate dehydrogenase. An approach based on the use of different oligomeric forms of the enzyme immobilized on sepharose.

The binding of denatured B. stearothermophilus D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to the E. coli chaperonin GroEL was investigated in two systems: (1) GroEL immobilized on Sepharose via a single subunit was titrated with urea-denatured soluble GAPDH and (2) a Sepharose-bound denatured GAPDH monomer was titrated with soluble GroEL. Similar apparent KD values for the complex GroEL x GAPDH were obtained in both cases (0.04 and 0.03 microM, respectively), the stoichiometry being 1.0 mol chaperonin per GAPDH subunit in the system with the immobilized GroEL and 0.2 mol chaperonin per Sepharose-bound GAPDH monomer. Addition of GroEL and Mg x ATP to a reactivation mixture increased the yield of reactivation of both E. coli and B. stearothermophilus GAPDHs. Incubation of the Sepharose-bound catalytically active tetrameric and dimeric GAPDH forms with the protein fraction of a wild-type E. coli cell extract resulted in the binding of GroEL to the dimer and no interaction with the tetrameric form. These data suggest that GroEL may be capable of interacting with the interdimeric contact regions of the folded GAPDH dimers.