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To mitigate greenhouse gas CO2 emissions and recycle its carbon source, one possible approach would be to separate CO2 from the flue gases of power plants and to convert it to a liquid fuel, e.g., methanol. Hydrogenation of CO2 to methanol is investigated in a dielectric-barrier discharge (DBD) with and without the presence of a catalyst. Comparison of experiments shows that this nonequilibrium discharge can effectively lower the temperature range of optimum catalyst performance. The simultaneous presence of the discharge shifts the temperature region of maximum catalyst activity from 220 to 100 °C, a much more desirable temperature range. The presence of the catalyst, on the other hand, increases the methanol yield and selectivity by more than a factor of 10 in the discharge. Experiment and numerical simulation show that methane formation is the major competitive reaction for methanol formation in the discharge. In the case of low electric power and high pressure, methanol formation can surpass methanation in the process.

The use of dielectric-barrier discharges (DBDs) is a mature technology originally developed for industrial ozone production. In this article, it is demonstrated that DBDs are also an effective tool to convert the greenhouse gases CH4 and CO2 to synthesis gas (syngas, H2/CO) at low temperature and ambient pressure. The synthesis gas produced in this system can have an arbitrary H2/CO ratio, mainly depending on the mixing ratio of CH4/CO2 in the feed gas. Specific electric energy, gas pressure, and temperature hardly influence syngas composition. The amount of syngas produced strongly depends on the electric energy input. CO2-rich mixtures prevent carbon and wax formation. At fixed specific input energies, the maximum amount of syngas with low H2/CO molar ratio is produced from a mixture of CH4:CO2 = 20:80. In a mixture of CH4:CO2 = 80:20, as high as 52 mol of H2 and 14 mol of CO have been obtained from 100 mol of feed gas at a specific input energy of 87 kW h/(N m3). CH4 conversion reaches 64%, and CO2 conversion is 54%. High temperatures lead to wax formation and carbon deposition in CH4-rich feeding mixtures. Low gas pressures favor syngas production.

Conantokin-G isolated from the marine snail Conus geographus is a 17-amino acid ␥-carboxyglutamate (Gla)-containing peptide that inhibits the N-methyl-Daspartate receptor. We describe the cloning and sequence of conantokin-G cDNA and the possible role of the propeptide sequence. The cDNA encodes a 100-amino acid peptide. The N-terminal 80 amino acids constitute the prepro-sequence, and the mature peptide is derived from the remaining C-terminal residues after proteolysis, C-terminal amidation, and a unique posttranslational modification, ␥-carboxylation of glutamate residues to Gla. Mature conantokin-G peptide containing Glu residues (E.Con-G) in place of Gla is a poor substrate for the vitamin K-dependent ␥-glutamyl carboxylase (apparent K m ‫؍‬ 3.4 mM). Using peptides corresponding to different segments of the propeptide we investigated a potential role for the propeptide sequences in ␥-carboxylation. Propeptide segment ؊20 to ؊1 covalently linked to E.Con-G or the synthetic pentapeptide FLEEL increased their apparent affinities 2 orders of magnitude. These substrates are not efficiently carboxylated by the bovine microsomal ␥-glutamyl carboxylase, suggesting differences in specificities between the Conus and the mammalian enzyme. However, the role of propeptide in enhancing the efficiency of carboxylation is maintained.

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