Game of Aliphatics: A Density Functional Theory Study of Base-Catalyzed Substrate-Controlled Dimerizations of Aliphatic Alkynones.

The present work focuses on a comprehensive density functional theory (DFT) study of newly discovered base-catalyzed substrate-controlled dimerizations of aliphatic alkynones. In order to understand the origin of selectivity of the cascade assemblies of 6-methylene-5-oxaspiro[2.4]heptanones and 2-alkenylfurans, structural and electronic properties of neutral and deprotonated alkynone molecules, thermodynamic and kinetic characteristics of the deprotonation of alkynones having diverse C-H active substituents at the carbonyl function under the action of a base, and thermodynamic and kinetic characteristics of possible mechanisms of the discussed cascade reactions were theoretically assessed.

Water Quality, Toxicity and Diversity of Planktonic and Benthic Cyanobacteria in Pristine Ancient Lake Khubsugul (Hövsgöl), Mongolia.

For the first time, microcystin-producing cyanobacteria have been detected in Khubsugul, which is ancient, pristine and one of the world's largest lakes. The microcystin synthetase genes belonged to the genera , and possibly spp. No microcystins were found in the water of the lake.

Theoretical Density Functional Theory Study of Electrocatalytic Activity of MN-Doped (M = Cu, Ag, and Zn) Single-Walled Carbon Nanotubes in Oxygen Reduction Reactions.

The mechanism of oxygen reduction reaction (ORR) on transition metal-doped nitrogen codoped single-walled nanotubes, CHMN (MN-CNT where M = Zn, Cu, or Ag; N = pyridinic nitrogen), has been studied with the density functional theory method at the ωB97XD/DGDZVP level of theory. The charge density analysis revealed two active sites of the catalyst toward ORR: the MN site and the C=C bond of the N-C=C-N metal-chelating fragment (C site). The structure of O-containing adsorbates (O , HOO*, O*, HO*, etc.

Trifluoromethanesulfonamide vs. Non-Fluorinated Sulfonamides in Oxidative Sulfamidation of the C=C Bond: An In Silico Study.

A theoretical analysis of the reaction of oxidative sulfamidation of several alkenes was performed in order to explain the various experimental observations and different reactivity of triflamide and non-fluorinated sulfonamides. Transformations occurring in the system alkene-sulfonamide in the presence of oxidative system (BuOCl + NaI) were analyzed at the MP2/DGDZVP//B3LYP/DGDZVP level of theory using the IEF-PCM method for taking into account the solvent acetonitrile (MeCN) effect. As the model substrates, styrene, trimethyl(vinyl)silane, dimethyl(divinyl)silane and diphenyl(divinyl)silane were chosen and mesylamide, triflamide, tosylamide and -nosylamide were taken as the reagents.

Single Si-Doped Graphene as a Catalyst in Oxygen Reduction Reactions: An In Silico Study.

Single Si-doped graphene CHSi with one carbon atom replaced by a three-coordinate silicon atom is studied by density functional theory (DFT) calculations as a catalyst for the oxygen reduction reactions (ORRs) in both acidic and alkaline media. The active sites for oxygen adsorption were determined from the distribution of the charge density difference analysis. At the equilibrium electrode potential, the most stable intermediate was found to have the structure HO*O*-CHSi with both oxygen atoms bound to the support, one of them being incorporated in between Si and C atoms, corresponding to the transfer of one hydrogen atom [H + e].

First detection of benthic cyanobacteria in Lake Baikal producing paralytic shellfish toxins.

Cyanobacteria were screened from the surface of diseased sponges, stone and bedrock in Lake Baikal for the presence of saxitoxin using enzyme-linked immunosorbent assay. In sequel, eight paralytic shellfish toxin (PST) variants were identified using a MALDI mass spectrometry. Microscopic examination found that Tolypothrix distorta dominated in the biofouling samples.

Ionofore antibiotic polynactin produced by Streptomyces sp. 156A isolated from Lake Baikal.

The potential antibacterial activity of secondary metabolites produced by Streptomyces sp. 156A isolated from Lake Baikal was investigated. The selective liquid-liquid extraction method was applied to obtain a mixture of nactins (polynactin) produced by the strain.