Dynamic Modelling of Nickel Complexation in Xylem Sap of Quercus ilex: A Voltammetric Study

Holm oak (Quercus ilex) is the dominant tree growing on serpentine soils of northeast Portugal, characterized by elevated soil concentrations of Ni and Mg, combined with low Ca concentrations. Apparently Q. ilex does not suffer from excessive concentrations of Ni in the soil. In this work we report a complexation study of nickel by the relevant ligands present in xylem sap: histidine, aspartic acid, oxalic and citric acids, at 0.10 M ionic strength and pH 5.5. Single and mixed complexes were characterized. To validate the proposed complexation model, diluted solutions of Q. ilex xylem sap were titrated with nickel. All studies were done using square‐wave voltammetry (SWV) at a hanging mercury drop electrode. Due to the dynamic nature of SWV, it is possible to obtain the conditional stability constants of the complexes formed but also to have knowledge on the kinetics of the interconversion of the species present.     

Kinetics and Mechanism of Ni(II) Chelation in Model and Real Solutions of Xylem Sap of Quercus ilex

The kinetics of formation and dissociation of Ni(II) complexes with oxalic and citric acids was studied by cyclic voltammetry in model solutions of xylem sap of Q. ilex (the dominant tree growing on serpentine soils of Northeast Portugal) using representative concentrations, pH and ionic strength. The role of magnesium on complex formation was analyzed from solutions where Mg is present at concentration levels found in the xylem sap of Q. ilex growing on both nonserpentine and serpentine soils. Kinetics studies were also done in diluted solutions of real xylem sap samples, spiked with increasing amounts of magnesium. The values obtained for the apparent rate constants were those anticipated by the proposed model. To test the validity of the methodology and mechanisms, formation rate constants, k_f (M^?1 s^?1) of Ni(II) complexes with citrate and oxalate were evaluated that compare with the values from Eigen mechanism.     

Micellar electrokinetic biofluid analysis of biogenic amines using on-line sample concentration and UV laser-induced native fluorescence detection

A simple and sensitive sweeping micellar electrokinetic chromatography method coupled with UV laser-induced native fluorescence detection has been developed for quantitative analysis of biogenic amines in biofluids. The background electrolyte comprised 30 mmol L⁻¹ phosphoric acid and 20 mmol L⁻¹ sodium dodecyl sulfate. The concentration limits of detection of analytes using sweeping-micellar electrokinetic chromatography (sweeping-MEKC) were in the range 7–100 nmol L⁻¹, which were 250–3600-fold improvement for dopamine, DOPA and epinephrine compared with conventional capillary zone electrophoresis. An improvement of approximately 20-fold was observed for all analytes compared with typical micellar electrokinetic chromatography conditions. Baseline separation was achieved for the all analytes within 12 min and migration-time and peak-area repeatability were better than RSD 0.35% and 5.68%, respectively. The developed method was applied to measure the biogenic amines in biofluids extracted from wheat phloem sap, human plasma and human urine.     

离子色谱法测定大豆木质部汁液中的Cl-、SO42-、NO3-、PO43-、柠檬酸和苹果酸

建立了离子色谱法测定大豆木质部汁液中Cl~-、SO_4~(2-)、NO_3~-、PO_4~(3-)、柠檬酸和苹果酸的方法。Cl~-、SO_4~(2-)、NO_3~-、PO_4~(3-)、柠檬酸和苹果酸的检出限分别为0.01、0.04、0.05、0.05、0.30和0.10 mg/L,相对标准偏差分别为8.34％、4.68％、9.54％、6.86％、5.52％和7.50％,线性范围分别为0.5～50.0、1.0～100.0、0.5～50.0、1.0～100.0、5.0～100.0和1.0～100.0 mg/L,回收率分别为103％～106.7％、92％～98.7％、93％～95.5％、91.7％～92％、93.2％～106％和94％～108.3％。方法简便、快速,测定结果准确,无干扰。     

Determination of inorganic and organic anions in xylem saps of two contrasting oilseed rape (Brassica juncea L.) varieties: Roles of anions in long-distance transport of cadmium

By optimizing chromatographic conditions of an ion chromatographic system, we identified and measured the major inorganic and organic anions (chloride, nitrate, malate, sulfate, phosphate and citrate) in the xylem saps of two contrasting tolerant oilseed rape (Brassica juncea L.) varieties (the high Cd-accumulating genotype Xikou Huazi and the low Cd-accumulating genotype Liangting Huazi). Cadmium concentrations in xylem saps were determined by graphite furnace atomic absorption spectrometry. By analyzing the relationship between anion and cadmium concentrations, we considered that the relatively low phosphate concentrations in Xikou Huazi xylem saps might relate to the relatively high xylem transport of Cd for this genotype, and malate in oilseed rape xylem saps seemed to participate in the long-distance Cd translocation process. Our work might not only be very useful for understanding the mechanisms of Cd hyperaccumulation for Xikou Huazi, but also very beneficial for future application of Xikou Huazi in phytoremediation.     

白桦液及白桦液复方清除自由基防止沙土鼠脑缺血再灌注氧化损伤的研究

本文用化学发光体系检测白桦液及其复方的清除活性氧自由基的功能。用羟胺法测实验动物化及脑组织的SOD活性,硫代巴比妥酸法测定MDA含量,细胞化学发光法测PMN细胞的免疫功能,化学发光法测脑组织的自发发光,直接法检测GSH-PX活性,氰高铁Hb法测Hb浓度,放免法测血浆TXB2的含量。结果表明,白桦液及其复方在离体体系中有清除O2-、OH-、H2O2的作用,在沙土鼠胞缺点再灌注模型中,可提高血和脑组织的SOD、GSH-PX活性,增强PMN细胞的免疫功能,降低血浆和脑组织LPO,TXB2及Hb浓度。本研究首次发现白桦液及其复方有抗氧化功能。     

A new approach for the limit to tree height using a liquid nanolayer model

Liquids in contact with solids are submitted to intermolecular forces inferring density gradients at the walls. The van der Waals forces make liquid heterogeneous, the stress tensor is not any more spherical as in homogeneous bulks and it is possible to obtain stable thin liquid films wetting vertical walls up to altitudes that incompressible fluid models are not forecasting. Application to micro tubes of xylem enables to understand why the ascent of sap is possible for very high trees like sequoias or giant eucalyptus.      

Molybdenum Speciation in Raw Phloem Sap of Castor Bean

Abstract

Separation and quantification of molybdenum (Mo) in raw phloem sap from castor bean (Ricinus communis L.) was performed by size exclusion chromatography (SEC) and further purification was performed using quantitative preparative native continuous polyacrylamide gel electrophoresis (QPNC-PAGE). For elemental detection, an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) was applied. Two different SEC columns were utilized: column A, Sephadex G-50 SF (700 mm × 24 mm), and column B, Sephadex G-25 M (28 mm × 9 mm). The protein content of the fractions was determined by the Bradford method. Using column A, two peaks of Mo were detected consisting of a main peak (Mo_A2) in the low molecular weight area (< 1.35 kDa), and a minor peak (Mo_A1, ≥ 30 kDa) at the void volume of the column. Both Mo species were detected at the ultraviolet (UV) active absorption area of raw phloem sap. Two peaks of Mo were also detected using column B, the first peak (Mo_B1) being at the same elution volume as the protein of raw phloem sap, and the second one (Mo_B2) was eluted in the area of 1.5 to 2.4 mL of elution volume. Raw phloem sap digested by proteinase K-enzyme indicates a significant reduction of Mo_B1 peak, which suggests that the peak may contain Mo bound to protein or polypeptides. The raw phloem sap and SEC fraction containing highest Mo concentration (Mo_A2) were furthermore separated by QPNC-PAGE. The result reveals that the Mo-containing fraction from the raw phloem sap was eluted at the same retention volume as the purified sample. This implies that the Mo species were also successfully separated and purified using QPNC-PAGE.     

Application of capillary electrophoretic methods for the analysis of plant phloem and xylem saps composition: A review

Plant vascular tissue is essential for the exchange of water, nutrients, metabolic products, and signals among distant organs in cormophytes. The compositions of phloem and xylem saps are highly dependent on many internal and external factors, and thus their analysis provides a valuable insight into plant physiology, growth, and development as well as nutrition status or presence of biotic or abiotic stresses. Capillary electrophoresis characterized by highly efficient separations and minuscule sample requirements represents a suitable analytical technique for this purpose because the sap constitutes a complex mixture with generally minimal availability. This review aims at providing a comprehensive overview of published capillary electrophoretic methods for the analysis of primary components present in the phloem and xylem saps of higher plants.     

Nano-emulsification of oriental lacquer sap by ultrasonic wave propagation: Improvement of thin-film characteristics as a natural resin

Lacquer sap has received much attention as a traditional natural resin because it is a renewable and eco-friendly biopolymer resource unlike artificial coating materials. However, strict drying conditions and long drying times of lacquer sap should be modified to expand its applications. This study presents the first attempt to investigate the effect of different amplitudes of ultrasonic waves on the lacquer sap composed of water-in-oil (W/O) emulsion droplets and the mechanical properties of the resultant film by solvent evaporation. Acoustically induced cavitation via batch ultrasonication facilitates the generation of submicron-sized W/O emulsion. The drying time of sonicated lacquer sap was noticeably shortened as the amplitude of acoustic power increased. Interestingly, the transparency of the film cast from lacquer sap consisting of the smallest emulsion droplets increased significantly, weakening the degree of colour change from caramel-like yellow to dark brown as polymerisation progressed. These are attributed to the effective and frequent contact of laccase enzyme with urushiol at the increased interfacial area of nano-emulsified W/O droplets pulverised by ultrasonic waves. The quinone radical-generation in the interface layer and its transfer to the urushiol oil phase through water-insoluble glycoprotein emulsifier are greatly promoted, resulting in highly cross-linked, dense three-dimensional polymer networks, which also increased the lacquer film hardness after drying. As the emulsion droplet size decreased, the mutual interaction between the catechol moiety of urushiol and the substrates increased, resulting in improved adhesion. The nano-emulsification of the lacquer sap by ultrasonic waves can be used in a simple, effective, and eco-friendly way to shorten the drying time and improve the film characteristics of natural resins. This approach could pave the way for its wide range of applications in industrial fields, taking into account green and sustainable chemistry.