Resonance Raman studies of the peroxotitanate(IV) complexes K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O

The resonance Raman spectra of K₂(Ti(O₂)(SO₄)₂)·5H₂O and K₂(Ti(O₂)(C₂O₄)₂)·3H₂O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O₂), with C_2ν symmetry. The ν(OO), ν_s(TiO) and ν_as(TiO) are observed around 890, 610 and 535 cm⁻¹, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O₂²⁻ → Ti(IV) charge-transfer transition. The calculated force constant values for the O₂²⁻ and TiO bonds are 320 and 275 N m⁻¹, respectively.     

Influence of HOCl…O3 and HOCl…HOCl interactions on the stability of O3(HOCl)2 complexes: a theoretical study

We have analysed the role of HOCl…O₃ and HOCl…HOCl interactions on the stability of four estimated O₃(HOCl)₂ complexes by means of ab initio molecular orbital calculations. It is predicted that the O₃(HOCl) + HOCl reaction is more energetically favourable than (HOCl)₂ + O₃ one. In all complexes, HOCl…HOCl interaction is stronger than HOCl…O₃ one. The results show that the HOCl…O₃ interaction strengthens the HOCl…HOCl one. On the other hand, O…H interaction in HOCl…O₃ moiety is strengthened when it interacts with HOCl. Quantum theory of atoms in molecules predicts that the weak interactions in O₃(HOCl)₂ complexes have electrostatic characteristic. In all complexes, the charge transfer from O₃ to (HOCl)₂ is expected from natural bond orbital analysis.     

Photosynthesis and Leaf Structure in Domesticated Cassava (Euphorbiaceae) and a Close Wild Relative: Have Leaf Photosynthetic Parameters Evolved Under Domestication?

Broad patterns across wild plant species show that leaf composition and morphology vary predictably among habitats, richer habitats favoring resource‐acquisition strategies and poorer habitats favoring resource‐conservation strategies. Domestication is often accompanied by a shift to richer habitats, and might thus be expected to lead to a shift in leaf composition and morphology and hence in photosynthetic parameters. We compared leaf photosynthetic parameters in domesticated cassava (Manihot esculenta) and a close wild relative, using greenhouse‐grown plants. In domesticated cassava, CO₂ exchange rate expressed per unit mass and specific leaf area (SLA, m²/kg dry mass) were greater than in the wild relative, whereas leaf dry matter content (LDMC, dry mass/fresh mass) was lower in the domesticate. These results suggest that SLA and net photosynthetic rates may both have increased in the evolution of cassava under domestication, enabling more rapid growth in relatively resource‐rich and protected agricultural habitats. Previous comparisons of photosynthetic rates in domesticated plants and wild relatives have usually considered only leaf area‐based measures. Here, we discuss the interest of using mass‐based rates to study the evolution of ecological strategies under domestication.     

The structure and properties of tetrakis(tironato)cerate(IV), Na12[Ce(C6H2O2(SO3)2)4]·9H2O·6C3H7NO

The title complex, prepared in 1 M NaOH, was crystallized from hot N,N-dimethylformamide/ ethanol solutions to give Na₁₂[Ce(C₆H₂O₂(SO₃)₂)₄]· 9H₂O·6DMF. The purple—brown crystals were examined by X-ray diffraction while inside quartz capillaries filled with DMF, (λ_max 425 nm, ϵ 3664; λ_sh 520 nm, ϵ 2240) and belong to space group Pbca, Z=8 with a=21.846(4), b=17.348(2), c=43.103- (6) Å, V=16.335(7) ų, D_c=1.693 gcm^t−3, D_o=1.725 g cm^t−3. Diffractometer data were collected using Mo Kα radiation to 2θ=43^o. For 7331 independent data with F_o²>3σ(F_o²) full matrix least squares refinement converged to unweighted and weighted R factors of 0.072 and 0.110, respectively, with a mixture of anisotropic and isotropic thermal parameters. The disordered DMF atom parameters were not refined. The structure consists of discrete monomeric Ce(C₆H₂S₂O₈)₄¹²⁻ units with 12 Na⁺ counter cations and 10 H₂O molecules (two with half occupancy), and 6 DMF molecules of solvation filling up spaces between cations and anions. Cerium(IV) is in a general position with a coordination polyhedron close to the trigonal-faced dodecahedron, D_2d, with the angles between the two BAAB trapezoids of 2.3^o and 3.7^o. The average CeO(A) distance, 2.363(9) Å is longer than the average CeO(B) distance, 2.326(15)Å, with the reverse being true for one of the four tironato ligands. The average ring OCeO angle is 67.9(1)^o. The cerium (IV) complex is found by cyclic voltammetry to undergo a quasi-reversible one-electron reduction (in strongly basic solution with excess tiron) with Ef=−497 mV vs. SCE, hence the ratio of the formation constants for tetrakis(tironato)cerate(IV) to that for tetrakis(tironato)cerate(III), K_IV/K_III, is 10³³. Characterization of other tiron salts is reported.     

A Negative Hydraulic Message from Oxygen-Deficient Roots of Tomato Plants? (Influence of Soil Flooding on Leaf Water Potential,Leaf Expansion,and Synchrony between Stomatal Conductance and Root Hydraulic Conductivity)

Four to 10 h of soil flooding delayed and suppressed the normal daily increase in root hydraulic conductance (Lp) in tomato (Lycopersicon esculentum Mill. cv Ailsa Craig) plants. The resulting short-term loss of synchrony between Lp and stomatal conductance decreased leaf water potential ([psi]L) relative to well-drained plants within 2 h. A decrease in [psi]L persisted for 8 h and was mirrored by decreased leaf thickness measured using linear displacement transducers. After 10 h of flooding, further closing of stomata and re-convergence of Lp in flooded and well-drained roots returned [psi]L to control values. In the second photoperiod, Lp in flooded plants exceeded that in well-drained plants in association with much increased Lp and decreased stomatal conductance. Pneumatic balancing pressure applied to roots of intact flooded plants to prevent temporary loss of [psi]L in the 1st d did not modify the patterns of stomatal closure or leaf expansion. Thus, the magnitude of the early negative hydraulic message was neither sufficient nor necessary to promote stomatal closure and inhibit leaf growth in flooded tomato plants. Chemical messages are presumed to be responsible for these early responses to soil flooding.     

[Zn(phen)(O,N,O)(H2O)] and [Zn(phen)(O,N)(H2O)] with O,N,O?is?2,6-dipicolinate and N,O?is?l-threoninate: synthesis, characterization, and biomedical properties

Two ternary Zn(II) complexes, with 1,10-phenanthroline (phen) as the main ligand and a carboxylate-containing ligand [dipicolinate (dipico) or L-threoninate (L-Thr)] as the subsidiary ligand, were prepared and characterized by elemental analysis, Fourier transform IR, UV, and fluorescence spectroscopy, X-ray diffraction, molar conductivity, and electrospray ionization mass spectrometry. X-ray structure analysis shows that both [Zn(phen)(dipico)(H(2)O)]·H(2)O (1) and [Zn(phen)(L-Thr)(H(2)O)Cl]·2H(2)O (2) have octahedral geometry about the Zn(II) atom. Both complexes can inhibit topoisomerase I, and have better anticancer activity than cisplatin against nasopharyngeal cancer cell lines, HK1 and HONE-1, with concentrations causing 50?% inhibition of cell proliferation (IC(50)) in the low micromolar range. Complex 2 has the highest therapeutic index for HK1. Both Zn(II) complexes can induce cell death by apoptosis. Changing the subsidiary ligand in the Zn(II) complexes affects the UV-fluorescence spectral properties of the coordinated phen ligand, the binding affinity for some DNA sequences, nucleobase sequence-selective binding, the phase at which cell cycle progression was arrested for treated cancer cells, and their therapeutic index.     

How relevant are S=O and P=O Double Bonds for the Description of the Acid Molecules H2SO3, H2SO4, and H3PO4, respectively?

The acid molecules H₂SO₃, H₂SO₄, and H₃PO₄ are usually drawn using "Lewis structures" which exhibit the octet extension by 3d-orbitals on sulfur and phosphorus, respectively. Thus, S=O and P=O double bonds are assumed to be formed. The natural d-orbital occupancies on S and P, however, were calculated to be as low as 0.1 e, and therefore, an octet extension can hardly be expected. After the natural bond orbitals (NBO) search procedure was forced to attempt to form different Lewis structures of bonds and lone pairs, we defined the optimal Lewis structure, if a dominant structure exists at all, by the maximum electronic charge in Lewis orbitals. Indeed, sulfur obeys the octet rule in the optimal zwitterionic Lewis structures and does not form S=O double bonds. No dominant resonance structure could be found for H₃PO₄ where polarized PO ?-bond and zwitterionic PO bond structures exhibit similar weights.     

Antioxidative Activity of (-)-Epigallocatechin-3-(3″-O-methyl)gallate Isolated from Fresh Tea Leaf and Preliminary Results on Its Biological Activity

Antioxidative activity of (-)-epigallocatechin-3-(3″-O-methyl)gallate (catechin e) was examined. Catechin e showed a strong antioxidative activity. A preliminary test using rat cancer cells suggests that catechin e also has a strong cytotoxic activity. Among tested catechins, only catechin e has strong activity for both.     

Comparative behavior of Pd and Ag deposition phenomenon on clean α-Al2O3 (001) surface—A first principle study

The nature of bonding at the interface between deposited silver/palladium and clean Al-terminated (001) surface of α-Al₂O₃ has been investigated using a periodic ab initio method. Substantial inter-planar relaxations within the alumina were found at both the interfaces and the bulk. The periodic calculation with both Ag and Pd deposition shows that 10% of loading on alumina results maximum stability. Surface energy and work function calculations were performed to propose the stability for the metals on the studied surfaces. The deposited Ag forms a three-dimensional (3-D) cluster on top of the alumina surface. The Pd cluster formed on the alumina surface is two-dimensional (2-D) and is distorted to accommodate the Ag cluster in its domain. A further low index calculation can explain the reason for a higher stability of the membrane generated over alumina support with silver and palladium. The results are discussed in view of the existing experimental data and models of metal-oxide interface and a reason for the difference of activity of the metal interaction with alumina surface is postulated.     

Fe2O3 Nanoparticle Seed Catalysts Enhance Cyclability on Deep (Dis)charge in Aprotic Li?O2 Batteries

Although the high energy density of Li? O₂ chemistry is promising for vehicle electrification, the poor stability and parasitic reactions associated with carbon‐based cathodes and the insulating nature of discharge products limit their rechargeability and energy density. In this study, a cathode material consisting of α‐Fe₂O₃ nanoseeds and carbon nanotubes (CNT) is presented, which achieves excellent cycling stability on deep (dis)charge with high capacity. The initial capacity of Fe₂O₃/CNT electrode reaches 805 mA h g^?1 (0.7 mA h cm^?2) at 0.2 mA cm^?2, while maintaining a capacity of 1098 mA h g^?1 (0.95 mA h cm^?2) after 50 cycles. The operando structural, spectroscopic, and morphological analysis on the evolution of Li₂O₂ indicates preferential Li₂O₂ growth on the Fe₂O₃. The similar d‐spacing of the (100) Li₂O₂ and (104) Fe₂O₃ planes suggest that the latter epitaxially induces Li₂O₂ nucleation. This results in larger Li₂O₂ primary crystallites and smaller secondary particles compared to that deposited on CNT, which enhances the reversibility of the Li₂O₂ formation and leads to more stable interfaces within the electrode. The mechanistic insights into dual‐functional materials that act both as stable host substrates and promote redox reactions in Li? O₂ batteries represent new opportunities for optimizing the discharge product morphology, leading to high cycling stability and coulombic efficiency.     

Biological Control ofBemisia argentifolii(Homoptera: Aleyrodidae) on Poinsettia with Inundative Releases ofEncarsia formosa(Hymenoptera: Aphelinidae): Are Higher Release Rates Necessarily Better?

The effectiveness of inundative releases of the parasitoidEncarsia formosafor control ofBemisia argentifoliion poinsettia was determined in replicated experimental greenhouses. We evaluated two release rates ofE. formosa:a low release rate (1 wasp/plant/week, released in two greenhouses, in spring 1995) and a high release rate (3 wasps/plant/week, released in two greenhouses, in fall 1993), each over a 14-week growing season. Each release trial had one or two control greenhouses in whichB. argentifoliideveloped on poinsettia in the absence ofE. formosa.Life-tables were constructed forB. argentifoliiin the presence and absence ofE. formosaby using a photographic technique to follow cohorts of whiteflies on poinsettia leaves. Weekly population counts of the whitefly were also made. In the absence ofE. formosa,egg to adult survivorship ofB. argentifoliion poinsettia was 75–81%. At the low release rate, egg to survivorship ofB. argentifoliiwas 5% and parasitism was 13%. At the high release rate, egg to adult survivorship forB. argentifoliiwas 8% and parasitism was 23%. The net reproductive rates (R₀) forB. argentifoliipopulations in the absence ofE. formosaranged from 18.01–26.12, indicating a rapidly increasing population. Net reproductive rates for whitefly populations subject to wasp releases were 1.54 for the low release rate greenhouses and 2.11 for the high release rate greenhouses, indicating substantially reducedB. argentifoliipopulation growth. The low release rate provided better control ofB. argentifoliithan the high release rate. This difference was attributed to higher levels of mortality of whiteflies at the low release rate in the first 5–6 weeks of the growing period. We suggest that mutual interference may also have affected observed levels of mortality and parasitism.     

Optical analysis of RE3+ (RE = Nd or Er):B2O3–P2O5–CaF2–ZnO–(Li2O/Na2O/K2O) glasses

Calcium boro fluoro zinc phosphate glasses modified using alkali oxide and doped with Nd³⁺ and Er³⁺ ions with the chemical composition of 69.5 (B₂O₃) + 10 (P₂O₅) + 10 (CaF₂) + 5 (ZnO) + 5 (Na₂O/Li₂O/K₂O) + 0.5 (Er₂O₃/Nd₂O₃) were prepared using a conventional melt quenching technique. The results of X-ray diffraction patterns indicated the amorphous nature of all the prepared glasses. The visible–near-infrared red (NIR) absorption spectra of these glasses were analyzed systematically. The NIR emission spectra of Er³⁺ and Nd³⁺:calcium boro fluoro zinc phosphate glasses showed prominent emission bands at 1536 nm (⁴I_13/2→⁴I_15/2) and 1069 nm (⁴F_3/2→⁴I_11/2) respectively with λ_exci = 514.5 nm (Ar⁺ laser) as the excitation source.     

A novel vanadium(V) homocitrate complex: synthesis,structure, and biological relevance of [K2(H2O)5][(VO2)2(R,S-homocitrate)2]·H2O

Initial investigations into the possible roles of homocitric acid in the biosynthesis and function of the active site cofactor of nitrogenase resulted in the isolation and characterization of the dinuclear vanadium(V) species [K₂(H₂O)₅][(VO₂)₂(R,S-C₇H₈O₇)₂]·H₂O ( 1). Complex 1 represents the first synthetic structurally characterized transition metal homocitrate complex and may represent an early mobilized precursor in the biosynthesis of VFeco. Compound 1 was characterized by a variety of physical methods, including X-ray crystallography. Crystal data: space group P?* (#2), with a?=?10.292 (3)?Å, b?=?16.663 (3)?Å, c?=?8.343 (1)?Å, α?=?95.93 (1)°, β?=?105.74 (2)°, γ?=?90.86 (2)°, V?=?1386 (1)?ų, and Z?=?2. The homocitrate ligand is coordinated to the vanadium(V) atoms in a bidentate fashion via the deprotonated bridging hydroxyl group and a carboxylate donor. This unique coordination mode accurately mimics the coordination of homocitrate to the cofactor of nitrogenase.     

A case of systemic lupus erythematosus (SLE) and Sj?gren's syndrome associated with anti-T3 autoantibodies

A case of systemic lupus erythematosus (SLE) associated with Sj?gren's syndrome had extremely low serum triiodothyronine (T3) with normal levels of serum thyroxine (T4) measured by single antibody radioimmunoassays (RIAs) and thyroid stimulating hormone (TSH) during steroid treatment. Measurement of serum T3 and T4 with double antibody RIAs showed unusually high T3 and normal T4 concentrations. Examination of her serum revealed the presence of IgG class anti-T3 autoantibodies whose Scatchard plot was analyzed in two components; one with a higher associate constant (8.6 X 10(8)M-1) and a lower binding capacity (5.6 X 10(-7) mol/ml serum); the other a lower associate constant (3.5 X 10(7)M-1) and a higher binding capacity (2.1 X 10(-6) mol/ml serum). Antithyroglobulin (Tg) autoantibody has been positive throughout the seven year observation period. A significant positive correlation between titers of anti-Tg autoantibodies indicated that the antigen of anti-T3 antibodies in the patient could be T3 containing antigenic site(s) on the Tg molecule.