A Proof for Substitution of Endogenous Iron (II) in Lipoxygenase by Exogenous Cu2+

Soybean lipoxygenase (LOX) contains endogenous iron (II) at the active site, which is important for the enzyme activity. The activity of LOX can be accelerated by some exogenous metal ions including Cu²⁺. However, the mechanism of the activity improvement caused by exogenous metal ions remains unclear, not only for LOX but for most other metalloenzymes. Meanwhile, the possibility that exogenous metal ions can displace endogenous iron (II) is still in discussion for a lack of a direct and quantitative proof. In this paper, a quantitative proof of replacing iron (II) inside LOX by exogenous Cu²⁺ was provided, simply using UV-Vis spectrometry with two indicators p-carboxylantipyrylazo and 9-(4-carboxyphenyl)-2,3,7-trihydroxyl-6-fluorine. A 0.56 μM free iron (II) was observed in the bulk solution after incubating 9.45 μM Cu²⁺ with 16.10 μM LOX at 20°C for 5 min, which is in coincidence with the decrement of Cu²⁺ in the bulk solution (0.53 μM), implying that iron (II) was replaced by Cu²⁺.     

An Effective Device for Gas–Liquid Oxygen Removal in Enclosed Microalgae Culture

A high-performance gas–liquid transmission device (HPTD) was described in this paper. To investigate the HPTD mass transfer characteristics, the overall volumetric mass transfer coefficients, K_{\textLa,\textCO2} ^\textA K_{{\text{La}},{\text{CO}}_2 }^{\text{A}} for the absorption of gaseous CO₂ and K_{\textLa,\textO2} ^\textD K_{{\text{La}},{\text{O}}_2 }^{\text{D}} for the desorption of dissolved O₂ were determined, respectively, by titration and dissolved oxygen electrode. The mass transfer capability of carbon dioxide was compared with that of dissolved oxygen in the device, and the operating conditions were optimized to suit for the large-scale enclosed micro-algae cultivation. Based on the effectiveness evaluation of the HPTD applied in one enclosed flat plate Spirulina culture system, it was confirmed that the HPTD can satisfy the demand of the enclosed system for carbon supplement and excessive oxygen removal.     

Structure,biological and electrochemical studies of transition metal complexes from N,S,N′ donor ligand 8-(2-pyridinylmethylthio)quinoline

The semirigid tridentate 8-(2-pyridinylmethylthio)quinoline ligand (Q1) is shown to form the structurally characterized transition metal complexes [Cu(Q1)Cl₂] (1), [Co(Q1)(NO₃)₂] (2), [Cd(Q1)(NO₃)₂] (3), [Cd(Q1)I₂] (4). [Cu(Q1)₂](BF₄)₂·(H₂O)₂ (5), [Cu(Q1)₂](ClO₄)₂·(CH₃COCH₃)₂ (6), [Zn(Q1)₂](ClO₄)₂(H₂O)₂ (7), [Cd₂(Q1)₂Br₄] (8), [Ag₂(Q1)₂(ClO₄)₂] (9), and [Ag₂(Q1)₂(NO₃)₂] (10). Four types of structures have been observed: ML-type in complexes 1–4, in which the anions Cl⁻, NO₃⁻ or I⁻ also participate in the coordination; ML₂⁻ type in complexes 5–7 without direct coordination of the anions BF₄⁻ or ClO₄⁻ and with more (Cu²⁺) or less (Zn²⁺) distorted bis-fac coordinated Q1; M₂L₂-type in complex 8, in which two Br⁻ ions act as bridges between two metal ions; and M₂(μ-L)₂-type in complexes 9 and 10, in which the ligand bridges two anion binding and Ag–Ag bonded ions. Depending on electron configuration and size, different coordination patterns are observed with the bonds from the metal ions to N_pyridyl longer or shorter than those to N_quinoline. Typically Q1 acts as a facially coordinating tridentate chelate ligand except for the compounds 9 and 10 with low-coordinate silver(I). Except for 6 and 8, the complexes exhibit distinct constraining effects against both G(+) and G(-) bacteria. Complexes 1, 3, 4, 5, 7 have considerable antifungal activities and complexes 1, 5, 7, and 10 show selective effects to restrain certain botanic bacteria. Electrochemical studies show quasi-reversible reduction behavior for the copper(II) complexes 1, 5 and 6.     

Synthesis,structural characterization and growth features of some (Ph)Se–Cd cluster compounds (Ph = phenyl)

Cd(SePh)₂, CdBr₂·4H₂O/CdI₂ and PCh₃ (Ph = phenyl; PCh₃ = tricyclohexylphosphine) react to give [(SePh)₂Cd₂Br₂(PCh₃)₂] (1), [(SePh)₂Cd₂I₂(PCh₃)₂] (2) and [(SePh)₇Cd₄Br(PCh₃)]_n (3).     

Tracking protein electrodenaturation fronts in the electrochemical treatment of tumors

Electrochemical reactions in the electrochemical treatment of tumors (EChT) induce extreme pH changes and, consequently, protein electrodenaturation fronts intimately related to tumor destruction. Here we introduce a new in vitro EChT collagen–macronutrient gel (CMG) model to study protein electrodenaturation fronts as a mean of assessing EChT effectiveness. Our CMG model shows that from an initial uniform condition two electrodenaturation fronts evolve expanding towards each other until collision. Moreover, electrodenaturation front tracking reveals that the front grows under a diffusion-controlled regime. Based on this evidence it is possible, in principle, to predict the time needed for tumor destruction without compromising healthy tissue. These results are consistent with those previously obtained with in vivo and in vitro EChT modeling. In contrast to previous simpler in vitro models, our CMG model represents a better structural and chemical approximation to a real tissue thus providing a better tool for validation of new in silico EChT models aimed at a more accurate prediction of tissue destruction level.     

Fabrication and performance test of solid oxide fuel cells with screen-printed yttria-stabilized zirconia electrolyte membranes

Yttria-stabilized zirconia (YSZ) membranes were deposited onto porous NiO–YSZ anode supports by screen printing. Combined with La_0.7Sr_0.3MnO₃–YSZ composite cathode, the prepared anode-supported solid oxide fuel cells (SOFCs) were electrochemically tested. A typical SOFC with a 30-μm-thick YSZ electrolyte membrane gave the maximum power densities (MPDs) of 0.26, 0.53, 0.78, and 1.03 W/cm² at 650, 700, 800, and 850 °C, respectively, using hydrogen as fuel and stationary air as oxidant. Replacement of stationary air with pure oxygen flow exerted a significant positive effect on the MPDs of the cell. Using 100- and 200-ml/min oxygen as oxidants, the MPDs of the cell were enhanced 35.3% and 68.6%, respectively. Polarization analysis indicated that, at the MPD points, the electrode polarization resistances accounted for 80% of the cell total resistances.