Gatekeeping patterns in the publication of analytical chemistry research

An analysis has been made of the nationalities of the members of advisory and editorial boards of analytical chemistry journals. Correlations were sought between their number and citation rates and between their number and the number of analytical papers published by scientists from the country in question. A comparison is given for the gatekeepers of organic and inorganic chemistry journals.     

Crown-containing butadienyl dyes 8. Structures and complexation of chromogenic dithia-15(18)-crown-5(6) ethers

The structures of new butadienyl dyes of the benzothiazole series containing the dithia-15-crown-5 (2a) or dithia-18-crown-6 (2b) fragments were established by X-ray diffraction. Complexation of dyes 2a,b with Hg²⁺, Pb²⁺, Cd²⁺, Ag⁺, Zn²⁺, and alkaline-earth cations in aqueous-acetonitrile solutions was studied by spectrophotometry. At a high percentage of water in solutions (P _w ≈ 50%), these dyes have a very low ability to bind Pb²⁺ cations (logK < 2) and virtually do not bind Cd²⁺, Zn²⁺, and alkaline-earth cations. At the same time, these dyes form stable 1: 1 complexes with Hg²⁺ and Ag⁺ cations at all P _w. The stability constants of complexes with the Ag⁺ cation increase with increasing P _w because the free energy of hydration of this cation is much lower than the free energy of solvation in acetonitrile. In the P _w range from 0 to 75%, the stability constants of the complexes of dyes 2a,b with the Hg²⁺ cation are larger than those of the corresponding complexes with the Ag⁺ cation by more than four orders of magnitude. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 90–96, January, 2006.     

THE REACTIVITY OF CITRONELLOL and α-THUJENE WITH SINGLET OXYGEN. RATE CONSTANTS OF CHEMICAL REACTION and PHYSICAL QUENCHING*

The quantum yields of Rose Bengal sensitized photooxidation of citronellol and α-thujene have been determined as a function of added acceptor and compared with those of furfuryl alcohol as a standard. The results permitted the calculation of the corresponding rate constants of chemical reaction (k_T) and physical quenching (K_q) of singlet oxygen. The sum (k_T+ k_q) has been verified independently by a Stern-Volmer analysis of the singlet oxygen luminescence quenching. α-Thujene reacts faster with singlet oxygen than citronellol, physical quenching being negligible in both cases.     

Hydrodynamics of a bounded vertical film with nonlinear surface properties

The drainage of a thin liquid film with an insoluble monolayer down a vertical wall is studied. Lubrication theory is used to develop a model where the film is pinned at the top with a given thickness and the film drains into a bath at the bottom. A nonlinear equation of state is used for the surface tension and the surface viscosity is a nonlinear function of the surfactant concentration; these are appropriate for some aqueous systems. The three partial differential equations are solved via discretization in space and then the resulting differential algebraic system is solved. Results are described for a wide range of parameters, and the conditions under which the free surface is immobilized are discussed.     

Plasticized open-cell polyurethane foam as a universal matrix for organic reagents in trace element preconcentration: Part I. Collection of silver traces on dithizone foam

The preparation of plasticized foam containing dithizone or zinc dithizonate is described. The foam was used successfully for the rapid and quantitative collection of trace amounts of silver in batch and column experiments. The preconcentration of small amounts of silver from dilute aqueous solutions was found to be possible. The effects of different plasticizers, pH of the aqueous phase, and dithizone concentration in the foam, on the collection rate of silver were critically investigated.     

Characterization of a putative sensory [FeFe]-hydrogenase provides new insight into the role of the active site architecture

[FeFe]-hydrogenases are known for their high rates of hydrogen turnover, and are intensively studied in the context of biotechnological applications. Evolution has generated a plethora of different subclasses with widely different characteristics. The M2e subclass is phylogenetically distinct from previously characterized members of this enzyme family and its biological role is unknown. It features significant differences in domain- and active site architecture, and is most closely related to the putative sensory [FeFe]-hydrogenases. Here we report the first comprehensive biochemical and spectroscopical characterization of an M2e enzyme, derived from Thermoanaerobacter mathranii. As compared to other [FeFe]-hydrogenases characterized to-date, this enzyme displays an increased H₂ affinity, higher activation enthalpies for H⁺/H₂ interconversion, and unusual reactivity towards known hydrogenase inhibitors. These properties are related to differences in active site architecture between the M2e [FeFe]-hydrogenase and “prototypical” [FeFe]-hydrogenases. Thus, this study provides new insight into the role of this subclass in hydrogen metabolism and the influence of the active site pocket on the chemistry of the H-cluster.

Characterization of a group D putative sensory [FeFe]-hydrogenase reveals how the active site can be tuned to decrease CO inhibition and increase stability of a reduced H-cluster while retaining the ability to catalyze H⁺/H₂ interconversion.