Accumulation of <Superscript>137</Superscript>Cs and <Superscript>40</Superscript>K in aboveground organs of tropical woody fruit plants

Distribution of ⁴⁰K and ¹³⁷Cs in tissues of the Citrus aurantifolia was measured by gamma spectrometry. A simple theoretical model is also proposed to describe the temporal evolution of ⁴⁰K activity concentration in such tropical woody fruit species. This model exhibits close agreement with the ⁴⁰K experimental results, in the leaf growing and fruit ripening processes of lemon trees.     

Quantification of measurement uncertainty in the sequential determination of <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po by liquid scintillation counting and alpha-particle spectrometry

Methodologies for the quantification of measurement uncertainties associated with the determination of ²¹⁰Pb- and ²¹⁰Po-specific activities by liquid scintillation counting (LSC) and alpha-particle spectrometry are presented, and are demonstrated using the soil reference material IAEA-326. Major contributors to the combined uncertainty associated with the measurement result of ²¹⁰Pb were the uncertainties of net count rates in the ²¹⁰Pb energy region of the sample spectrum and in the ²¹⁰Bi energy region of the blank spectrum. The predominant sources of uncertainty in the measurement of ²¹⁰Po were the uncertainties of net count rates in the regions of interest of ²⁰⁹Po and ²¹⁰Po. The relative standard uncertainty of ²¹⁰Po exponentially increases with the time interval between the sampling date and the separation date of Po, and this effect is strongly dependent on the ²¹⁰Po/²¹⁰Pb activity ratio. When the specific activity of ²¹⁰Pb is much higher than that of ²¹⁰Po in the sample, the relative standard uncertainty of the ²¹⁰Po determination increases significantly within a short time interval between the sampling date (or reference date) and the separation date of Po in samples.     

Effects of La<Superscript>3+</Superscript> on inward K<Superscript>+</Superscript> channels at plasma membrane in guard cells

The effects of La³⁺ on inward K⁺ channels at plasma membrane in vicia guard cells are investigated using the whole-cell patch-clamp recording mode. It is shown that La³⁺ on both sides of plasma membrane blocks inward K⁺ currents in a concentration-dependent manner, indicating that La³⁺ binding sites may exist on both sides of plasma membrane in guard cells in vicia. The dose response is fitted by the Michaelis-Menten relation characterized by an inhibitor constant K _i of 2.56±0.25 μmol · L⁻¹ (outside membrane) and (1.18±0.11)×10⁻¹⁵ mol · L⁻¹ (inside membrane). Intracellular La³⁺ has much stronger inhibitory effect on inward K⁺ currents than extracellular La³⁺ does, suggesting there may exist stronger binding sites inside membrane than outside membrane. Since ion channel activities of guard cells directly affect plant stomatal movement and water status, our results imply that rare earth elements might have potential practical values in regulating plant water status and strengthening plant drought endurance.     

NMR Spectra of Cyclic Nitrones. 7. The Influence of Substituents and a Hydrogen Bond on <Superscript>14</Superscript>N and <Superscript>17</Superscript>O Chemical Shifts in Derivatives of 3-Imidoazoline 3-Oxide

Derivatives of 3-imidazoline 3-oxide have been studied by ¹⁴N and ¹⁷O NMR methods. Regularities of the influence of substituents and of a hydrogen bond on chemical shifts have been made apparent. The range of changes of the chemical shifts of the nitrogen and oxygen nuclei of the nitrone group has been determined. Both in the ¹⁷O and in the ¹⁴N NMR spectra the signals of the amino derivatives are the highest field signals for the nitrone group, and the lowest field signals are the signals of the cyano derivatives in the series of derivatives investigated. Depending on the substituent (from amino to cyano group) the ¹⁷O chemical shifts varied over a range ∼155 ppm, but the interval of change of the ¹⁴N chemical shifts for the same substituents was ∼110 ppm. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1336–1341. September, 2005.     

Ionic mobility in ammonium-rubidium heptafluorozirconate (NH<Subscript>4</Subscript>)<Subscript>2.4</Subscript>Rb<Subscript>0.6</Subscript>ZrF<Subscript>7</Subscript> by (<Superscript>1</Superscript>H, <Superscript>19</Superscript>F) NMR data

NMR (¹⁹F, ¹H) methods are used to study ionic mobility in heptafluorozirconate (NH₄)_2.4Rb_0.6ZrF₇ in a range of temperatures from 150 K to 430 K. Types of ionic movements are determined, and their activation energy is evaluated. As a result of a phase transition a modification forms in which diffusion in the ammonium sublattice and isotropic reorientations of ZrF ₇ ^3? complex anions are observed. According to preliminary data, due to diffusion of ammonium ions the compound has relatively high ionic conductivity (σ ≈ 8.3 × 10^?5 S/cm at 423 K).     

Functionalization of one or two methyl groups in the [Cp*<Subscript>2</Subscript>RuBr]<Superscript>+</Superscript>Br<Superscript>−</Superscript> complex in the reaction with bromine

The reaction of [Cp*₂RuBr]⁺Br⁻ with bromine in CH₂Cl₂ (CD₂Cl₂) in an inert atmosphere at room temperature produces the complexes [Cp*Ru(Br)C₅Me₄CH₂Br]⁺Br₃ ⁻ (syn conformer), [Cp*Ru(Br)C₅Me₃(CH₂Br)₂]⁺ (syn and anti conformers), and [Ru(Br)(C₅Me₄CH₂Br)₂]⁺ (syn conformer). All complexes were characterized by ¹H and ¹³C NMR spectroscopy; the former complex, by elemental analysis. These complexes were also prepared by the reaction of [Cp*RuC₅Me₄CH₂]⁺BF₄ ⁻ with bromine in CH₂Cl₂. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2712–2718, December, 2005.     

Quantum-Chemical Investigation of Keto-enol-enethiol Tautomerism in 3-oxo-3-R<Superscript>1</Superscript>-N-R<Superscript>2</Superscript>-propanethioamides

The keto-enol-enethiol tautomerism in 3-oxo-3-R¹-N-R²-propanethioamides under vacuum and in acetone was studied in terms of density functional theory. It was established that the equilibrium depends on the structure of the 3-oxo-3-R¹-N-R²-propanethioamides and on the nature of the solvent, but the most stable form is as a rule the keto form stabilized by an intramolecular hydrogen bond. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 272–277, September–October, 2005.     

Structure of Galactomannans from <Emphasis Type="Italic">Gleditsia delavayi</Emphasis> and <Emphasis Type="Italic">G. aquatica</Emphasis> by <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR Spectroscopy

The structure of galactomannans isolated from seeds of G. delavayi and G. aquatica was studied by ¹H and ¹³C NMR spectroscopy. It was found that the galactomannans consisted mainly of β-1-4-bound mannopyranoses, a part of which was substituted on the C-6 hydroxyl by terminal units of α-galactopyranose.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 12–13, January–February, 2005.     

<Superscript>2</Superscript>H-NMR investigation after a polymerisation-induced phase separation process*

Polymer-dispersed liquid crystals (PDLC) are composite materials consisting of micron-sized droplets of liquid crystal dispersed in a polymer matrix. The easiest method to obtain a PDLC film is the polymerisation-induced phase separation process (PIPS). The liquid crystal is mixed with a monomer of low molecular weight and polymerisation is induced by heat or UV light. The increasing molecular weight of the polymer causes the phase separation of liquid crystal from the polymer matrix as micron-sized droplets. In this work, we have studied the structural changes induced in the polymer matrix of a PDLC after the PIPS process by deuterium nuclear magnetic resonance. Two different selectively deuterated monomers have been synthesized and investigated: isobutyl methacrylate (IBMA-d₂) and methyl methacrylate (MMA-d₃). The main results were the disappearance of the characteristic two-site hop in poly-IBMA, due to liquid crystal molecules, and the lack of unreacted MMA molecules in the liquid crystal droplets. In this last case, we found that it is possible to confine temporarily the unreacted MMA molecules within liquid crystal droplets.Abbreviations MMA Methyl methacrylate - IBMA Isobutyl methacrylate - PDLC Polymer-dispersed liquid crystal - PIPS Polymerisation-induced phase separation - ²H-NMR Deuterium nuclear magnetic resonance*Dedicated to Professor V. Bertini for his 70^th birthday     

Electrochemical properties of <Emphasis Type="Italic">n</Emphasis>-sulfonatothiacalyx[4]arene complexes with Fe<Superscript>3+</Superscript> and [Co(dipy)<Subscript>3</Subscript>]<Superscript>3+</Superscript> ions

The electrochemical properties of n-sulfonatothiacalyx[4]arene (H₄XNa₄) complexes with [Co(dipy)₃]³⁺ and Fe³⁺ ions were studied by means of cyclic voltammetry in aqueous solution at pH 2.5. The observed single-electron reduction of [Co(dipy)₃]³⁺ bound extraspherically to the upper rim and Fe³⁺ ion bound intraspherically to the lower rim of n-sulfonatothiacalyx[4]arene in binary [Co(dipy)₃]³⁺ · H₃X^5?, H₃X^5? · Fe³⁺, and ternary [Co(dipy)₃]³⁺ · H₃X^5? · Fe³⁺ heterometal complexes was more difficult than in the free state. The reversible single-electron transfer to the metal ion results in lower binding energy ([Co(dipy)₃]³⁺, ΔΔG ₀ = 3.9 kJ/mol) or in full fast dissociation of the complex (Fe³⁺). The ternary complex in the solution forms the aggregates, in which inner encapsulated Fe(III) and Co(III) ions are not reduced on the electrode. Their quantitative reduction takes place by the relay mechanism of intra- and intermolecular electron transfer through electrochemically generated [Co(dipy)₃]²⁺ outer ions.     

A new phosphor with flower-like structure and luminescent properties of Sr<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>: Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> long afterglow materials by sol–gel method

The flower-like phosphors of Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased Sr₂MgSi₂O₇ phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists of nano-sized whiskers which are detected for the first time in Eu²⁺ and Dy³⁺ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ nanostructure. Finally, the optical properties of flower-like Sr₂MgSi₂O₇ nanostructure have been characterized by photoluminescence (PL) spectra.     

Combination of <Superscript>13</Superscript>C/<Superscript>113</Superscript>Cd NMR,potentiometry, and voltammetry in characterizing the interactions between Cd and two models of the main components of soil organic matter

This work allowed the characterization of the Cd-binding sites of two compounds taken as models for exudates, the main components of soil organic matter (SOM). The studied compounds were exopolysaccharides (EPS), specifically exudates of roots (polygalacturonic acid) and of soil bacteria (Phytagel). Potentiometric acid–base titrations were performed and fitting of the obtained results indicated the presence of two main classes of acidic sites, defined by their pK _a values, for both EPS but of a different nature when comparing the two compounds. The two studied exopolysaccharides presented different acidic/basic site ratios: 0.15 for Phytagel and 0.76 for polygalacturonic acid. Spectroscopic techniques (¹³C/¹¹³Cd NMR, FTIR) distinguished different Cd surroundings for each of the studied EPS, which is in agreement with the titration results. Furthermore, these analyses indicated the presence of –COOH and –OH groups in various proportions for each exopolysaccharide, which should be linked to their reactivity towards cadmium. Cadmium titrations (voltammetric measurements) also differentiated different binding sites for each compound and allowed the determination of the strength of the Cd-binding site of the EPS. Fitting of the results of such voltammetric measurements was performed using PROSECE (Programme d’Optimisation et de Speciation Chimique dans l’Environnement), a software coupling chemical speciation calculation and binding parameter optimization. The fitting, taking into account the Cd²⁺/H⁺ competition towards exopolysaccharides, confirmed the acid-base titrations and spectroscopic analyses by revealing two classes of binding sites: (i) one defined as a strong complexant regarding its Cd²⁺–EPS association (logK = 9–10.4) and with basic functionality regarding H⁺–EPS association (pK _a = 11.3–11.7), and (ii) one defined as a weak complexant (logK = 7.1–8.2) and with acidic functionality (pK _a = 3.7–4.0). Therefore the combination of spectroscopic analyses, voltammetry, and fitting allowed the precise characterization of the binding sites of the studied exopolysaccharides, mimicking the main SOM components. Furthermore, the binding parameters obtained by fitting can be used in biogeochemical models to better define the role of key SOM compounds like exudates of roots and of soil bacteria on trace metal transport or assimilation.     

Synthesis and biological evaluation of <Superscript>99m</Superscript>Tc-HEDTA/HYNIC-MPP4 complex for 5-HT<Subscript>1A</Subscript> receptor imaging

5-HT_1A receptor is associated with a variety of pathophysiology of neuropsychiatric disorders. Accordingly, we have synthesized a new 5-HT_1A receptor ligand (HYNIC-MPP4) and labeled it with ^99mTc using N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) as coligand. ^99mTc-HEDTA/HYNIC-MPP4 was prepared under pH 6 at room temperature. Biodistribution of 99mTc-HEDTA/HYNIC-MPP4 in normal mice showed that this complex had moderate brain uptake (0.60% ID·g⁻¹ at 2 min p.i.) and good retention. The hippocampus had the highest radioactivity uptake at 2 min p.i. (1.84% ID⋆g⁻¹). The ratio of Hipp/CB was 3.1 at 2 min p.i. and increased to 4.4 at 60 min p.i. After blocking with 8-hydroxy-2-(dipropylamino) tetralin, the uptake of hippocampus was decreased significantly from 1.84% ID·g⁻¹ to 0.53% ID·g⁻¹ at 2 min p.i., while the cerebellum had no significant decrease. This ^99mTc complex could be a potent agent for 5-HT_1A receptor imaging. Supported by the National Natural Science Foundation of China (Grant No. 20401004) and the Analysis and Test fund of Beijing Normal University     

Theoretical study on the reaction mechanism of (CH<Subscript>3</Subscript>)<Subscript>3</Subscript>CO<Superscript>.</Superscript> radical with NO

The reaction mechanism of (CH₃)₃CO^. radical with NO is theoretically investigated at the B3LYP/6-31G* level. The results show that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than that in the triple state. The balance reaction: (CH₃)₃CONO⇔(CH₃)₃CO^.+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH₃)₃CO^. radical increase. So NO may be considered as a stabilizing reagent for the (CH₃)₃CO^. radical.     

Preparation and Characterization of GdTaO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> Sol-Gel Luminescence Thin Films

High quality GdTaO₄:Eu³⁺ luminescence films have been successfully prepared through a modified sol-gel process. The films were prepared using inorganic materials as raw materials, and the thermal decomposition and UV assisted technique were introduced to improve the quality of the film and reduce the period for forming the thick film. Results of structural studies by atomic force microscopy (AFM) and X-ray diffraction (XRD) showed that the surface was smooth and the structure was monoclinic with the average grain size of about 55 nm. The emission and excitation spectra of the film were investigated. Related to the transition ⁵ D₀ →⁷ F₁ and ⁵ D₀→⁷ F₂ of Eu³⁺ ions, the main luminescence peaks were observed at 591 and 611 nm respectively, and the luminescence peak at 345 nm was detected simultaneously related to the TaO₄³⁻ emission. Transmission spectrum and decay curve of the luminescence are also presented in this paper.     

Manifestation of electron-nuclear dynamics in <Superscript>59</Superscript>Co NQR spectra of a series of cobaltocenium derivatives

A coupling equation relating the quadrupole coupling constant (e² Qq _zz ) to the asymmetry parameter (η) of the electric field gradient for a series of cobaltocenium derivatives (⁵⁹Co NQR) is derived. The estimates of the correlation times of “slow” modulations of electron motions by tunneling processes lie in the range from 10⁻¹² to 10⁻¹⁴ s. This corresponds to the interval of the characteristic times of nuclear motions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1919–1923, October, 2007.     

Local structure and photoluminescent characteristics of Eu<Superscript>3+</Superscript> in ZnO–SiO<Subscript>2</Subscript> glasses

The photoluminescence properties of xZnO–(100−x)SiO₂ (x = 0, 5, 10, 20) containing 1% Eu₂O₃ prepared by a sol–gel method were systematically investigated. The results indicated that the relative proportion of f–f transitions to charge transfer (CT) absorption decreased with the increase of ZnO concentration. The intensity of ⁵D₀–⁷F_J transitions of Eu³⁺ ions was enhanced with the increase of ZnO content due to local structure changes and decreased quantities of Eu³⁺ ions clusters. The results of fluorescence line narrow (FLN) spectra indicated that Eu³⁺ ions occupied one site in SiO₂ glass and two sites in ZnO–SiO₂ glasses. The second-order crystal field parameters were calculated. B₂₀ and B₂₂ for site 1 increased with excitation energy, while ones hardly changed for site 2.     

[1-B<Subscript>10</Subscript>H<Subscript>9</Subscript>N<Subscript>2</Subscript>]<Superscript>−</Superscript> and [1-CB<Subscript>9</Subscript>H<Subscript>10</Subscript>]<Superscript>−</Superscript> anions: an attempt of quantum chemical calculations

Comparative quantum chemical calculations of structural parameters, chemical shifts of ¹¹B NMR spectra, and atomic charges in 10-vertex boron hydride anions [1-CB₉H₁₀]⁻ and [1-B₁₀H₉N₂]⁻ were performed using the restricted Hartree-Fock method with the 6-31++G(D,P) basis set. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1853–1855, September, 2007.     

Theoretical prediction on vibrational spectra of [Ar...Ar-H]<Superscript>+</Superscript>

Centrosymmetric linear [Ar-H-Ar]⁺ and asymmetric linear [Ar---Ar-H]⁺ are two stable configurations of [Ar₂H]⁺. Based on the global potential energy surface of [Ar₂H]⁺ provided by our group recently, we calculated the vibrational spectra of [Ar---Ar-H]⁺ with total angular momentum J = 0 by time-dependent quantum mechanical method, and the influence of quantum tunneling effect on vibrational spectra was found. With the help of the observation on the eigenstate functions and the modified potential energy surface, assignments were made to the spectra. The strong coupling between the excited bending mode of [Ar-H-Ar]⁺ and the vibrational states of [Ar---Ar-H]⁺ was discussed.     

Glycosylation of Bovine Serum Albumin with D-[<Superscript>14</Superscript>C]-Glucose

Certain parameters of the Maillard reaction between bovine serum albumin (BSA) and D-[¹⁴C]-glucose were investigated.__________Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 275–277, May–June, 2005.