甲烷生物催化氧化制甲醇——几种化学物质对Methylosinus trichosporium 3011甲醇累积的影响

本文报导了在 Methylosinus trichosporium 3011细胞反应液中加入一些化学物质对甲醇累积的影响。结果表明,Na~+抑制甲烷单加氧酶的活性。当 M.trichosporium 3011细胞反应液中含高浓度磷酸根时,只有很少量甲醇累积下来。EDTA 和 Na_2EDTA 甲醇累积的促进作用小于甲酸钠或甲酸的作用。但由于 EDTA 不仅可以抑制甲醇脱氢酶的活性,而且可以螯合 Na~+,而甲酸则可使 NADH 辅酶再生。因此,反应液中含有2mM EDTA 和20mM 甲酸时甲醇累积量最高。     

Analysis of serotonin release from single neuron soma using capillary electrophoresis and laser-induced fluorescence with a pulsed deep-UV NeCu laser

The use of capillary electrophoresis (CE) with laser-induced fluorescence excited by ultraviolet (UV) lasers in the range 200–300 nm has been restricted by the available wavelengths and expense of UV lasers. The integration of a NeCu deep UV laser operating at 248.6 nm with a single channel CE system with post-column sheath flow detection allows detection limits for serotonin and tryptophan of 3.9×10^-8 M and 4.5×10^-8 M respectively. Single cell analysis of serotonergic metacerebral cells from the sea slug Aplysia californica yields a value of 800±85 fmol of serotonin in each cell soma. For the first time, serotonin is directly detected in electrically stimulated release from single metacerebral cell soma, with approximately 4% of the serotonin contained in the soma released from a semi-intact preparation with a 2 min electrical stimulation.     

High Lithium Capacity MxV2O5Ay·nH2O for Rechargeable Batteries

The aqueous synthesis and electrochemical properties of nanocrystalline M_xV₂O₅A_y·nH₂O are described. It is easily and quickly prepared by precipitation from acidified vanadate solutions. M_xV₂O₅A_y·nH₂O has been characterized by X-ray powder diffraction, electron microscopy, TGA, chemical analyses, and electrochemical studies. The atomic structure is related to that of xerogel-derived V₂O₅·nH₂O. In M_xV₂O₅A_y·nH₂O, M is a cation from the starting vanadate salt and A is an anion from the mineral acid. This material exhibits high, reversible Li capacity and may be considered for use in a cathode in primary and secondary batteries. The lithium capacity of an electrode composed of M_xV₂O₅A_y·nH₂O/EPDM/carbon (88/4/8) is ∼380(mA h)/g (C/80 rate) and the energy density is ∼1000(W h)/kg (120-μm-thick cathode, 4-1.5 V, versus Li metal anode). Critical parameters identified in the synthesis of M_xV₂O₅A_y·nH₂O, with respect to achieving high Li-ion insertion capacity, are acid/vanadium ratio, starting vanadate salt, and temperature. Inclusion of carbon black in the synthesis yields a composite that maintains the high Li capacity, lowers the electrochemical-cell polarization, and preserves the lithium capacity at higher discharge rates. Li-ion coin cells, using pre-lithiated graphite anodes, exhibit electrochemical performance comparable to that of Li-metal coin cells.     

Novel fragmentation reaction of correolide

[reaction: see text] Pentacyclic triterpenoid natural product correolide (1) was converted to ketone 2 via ozonolysis. An unusual fragmentation reaction of ketone 2 with LiCl was discovered. This reaction is general among several similar substrates examined and appears to be specific for the correolide-type E-ring structure (ketone). A mechanism involving a retroaldol reaction, a nucleophilic opening of the epoxide, and a subsequent acetoxy elimination reaction was proposed.     

Redox Processes Involving Quinones on Poly-3,4-ethylenedioxythiophene-Modified Glassy Carbon Surface

Russian Journal of General Chemistry - Redox transformations involving quinone/hydroquinone redox pair on a glassy carbon electrode (pristine and modified with poly-3,4-ethylenedioxythiophene film)...     

Fabricating Dual-Atom Iron Catalysts for Efficient Oxygen Evolution Reaction: A Heteroatom Modulator Approach

Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear Fe^III₂Fe^II complex (denoted as Fe₃) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of Fe^II by other metal(II) ions (e.g., Zn^II/Co^II) via synthesizing isostructural trinuclear-complex precursors (Fe₂Zn/Fe₂Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities.     

Revisiting Indolo[3,2‐b]carbazole: Synthesis,Structures, Properties,and Applications

Indolo[3,2‐b]carbazole presents a π‐skeleton with a remarkable electronic structure and interesting potential applications. It is, however, also associated with ambiguity and controversy. Herein, new derivatives of indolo[3,2‐b]carbazole are reported and they have enabled a comprehensive study on the electronic structure of indolo[3,2‐b]carbazole and the development of a new n‐type organic semiconductor. Experimental and computational studies show that indolo[3,2‐b]carbazole has a largely localized p‐benzoquinonediimine moiety and significant antiaromaticity. When substituted with (4‐silylethynyl)phenyl groups, the indolo[3,2‐b]carbazole exhibits one‐dimensional π–π stacking and functions as an n‐type organic semiconductor in solution‐processed field effect transistors.     

Single electron transfer events and dynamical heterogeneity in the small protein azurin from Pseudomonas aeruginosa

Monitoring the fluorescence of single-dye-labeled azurin molecules, we observed the reaction of azurin with hexacyanoferrate under controlled redox potential yielding data on the timing of individual (forward and backward) electron transfer (ET) events. Change-point analysis of the time traces demonstrates significant fluctuations of ET rates and of mid-point potential E₀. These fluctuations are a signature of dynamical heterogeneity, here observed on a 14 kDa protein, the smallest to date. By correlating changes in forward and backward reaction rates we found that 6% of the observed change events could be explained by a change in midpoint potential, while for 25% a change of the donor–acceptor coupling could explain the data. The remaining 69% are driven by variations in complex association constants or structural changes that cause forward and back ET rates to vary independently. Thus, the observed spread in individual ET rates could be related in a unique way to variations in molecular parameters. The relevance for the understanding of metabolic processes is briefly discussed.

Observing electron transfer events in individual azurin molecules, we relate the spread in transfer rates in a unique way to variations in molecular parameters.     

Bifunctional primary amine-thiourea-TfOH (BPAT·TfOH) as a chiral phase-transfer catalyst: the asymmetric synthesis of dihydropyrimidines

An enantioselective Biginelli reaction has been developed by using a bifunctional primary amine-thiourea-TfOH (BPAT·TfOH) as a chiral phase-transfer catalyst and t-BuNH(2)·TFA as an additive in saturated brine at room temperature. The corresponding dihydropyrimidines were obtained in moderate-to-good yields with up to 99% ee under mild conditions. A plausible transition state has been proposed to explain the origin of the activation and the asymmetric induction.     

Synthesis,Crystal Structure,and Characterization of a Novel Metallo‐Organically‐Templated Pentaborate with Mixed Ligands

A novel metallo‐organically templated pentaborate with layered framework, [Cd(TETA)(C₂H₃O₂)][B₅O₆(OH)₄] ( 1 ) (TETA = triethylenetramine), was synthesized under mild solvothermal conditions. The structure was determined by single‐crystal X‐ray diffraction and further characterized by FT‐IR spectroscopy, elemental analysis, thermogravimetric analysis, and photoluminescence spectroscopy. The structure consists of an isolated polyborate anion [B₅O₆(OH)₄]^– and the cadmium complex cation of [Cd(TETA)(C₂H₃O₂)]⁺, which contains both organic amine and organic acid ligands. The [B₅O₆(OH)₄]^– units are connected together by hydrogen bonds, and a 2D sheet‐like framework with rectangle‐like 12‐membered boron rings are formed. The [Cd(TETA)(C₂H₃O₂)]⁺ complex cations are located in the free space between the layers and connect the adjacent borate layers through hydrogen bonds to form a three‐dimensional supramolecular network. The luminescent properties of the compound were studied for the first time in the series of metallo‐organically‐templated pentaborates, and a blue luminescence occurs with an emission maximum at 468 nm upon excitation at 397 nm.