Changes in specific area and energy of root surface of cereal plants in Al-solution cultures. Water vapor adsorption studies

Surface areas and energetic properties of the shooting stage roots of rye (Secale L.), triticale (Triticale), barley (Hordeum L.) and four wheat (Triticum L.) varieties were estimated from experimental water vapor adsorption data. Roots stressed during 10 days at pH 4 with aluminium concentrations ranging from 0 to 40 mg dm^–3 were studied. Roots grown continuously at pH 7 were taken as controls. The surface properties of the roots grown at pH 4 without Al addition were apparently the same as those of the control roots. With the increase of the concentration of the aluminium treatment the surface area of the roots increased for all of the plants, beginning at 5 mg Al dm^–3 for barley, at 10 mg Al dm^–3for wheat and triticale, and at 40 mg Al dm^–3 for rye. The average water vapor adsorption energy of the root surface decreased in general with the increase of Al stress concentration for all plants but triticale, for which this increased. The sensitive cereal varieties seem to have greater amount of high energy adsorption centers (more polar surface) than the resistant ones (lower surface polarity), however more data is needed to justify this hypothesis. For Al-sensitive roots, fraction of high energy adsorption sites decreased and fraction of low energy sites increased under the Al stress. Smaller changes in adsorption energy sites were noted for roots of Al-resistant plants.     

Study of the stability of aluminium trimeric clusters in aqueous solutions

Ab initio molecular dynamics (AIMD) based on density functional theory has been used to study small aluminium–oxygen complexes in water. Such Al–O clusters have been seen in several recent mass spectrometry studies. In this study, we have focused on trimeric Al–O clusters. The initial very compact trimeric Al–O structures opened up and formed linear Al–O chains. The typical Al–O coordination number in these chain structures was 5. We have performed long (up to 200 ps) AIMD simulations and these chain structures are stable on the nanosecond time scale. We have also studied the reactivity of the Al–O dimer and solvated Al. We found a formation path for the trimeric cluster, which has a action barrier (0.04 eV) and a reaction free energy of ? 0.55 eV. This suggests that the association of a dimer and a monomer Al–O species is fast and thermodynamically a very favourable process.     

The beneficial effect of aluminium and the role of citrate in Al accumulation in Melastoma malabathricum

* Here we investigated the beneficial effect of aluminium (Al) on the development of the Al accumulating plant Melastoma malabathricum. * Seedlings of M. malabathricum were cultivated in a nutrient solution containing 0.5 mM Al and compared with barley (Hordeum vulgare). In addition, roots of M. malabathricum were divided into one part growing in a nutrient solution, and the other part growing in a calcium solution. Al (0.5 mM) was applied to either solution. * Al-induced improvements of the root activity contributed to a growth enhancement in M. malabathricum. Al exposure without nutrients did not increase root growth and Al accumulation in the leaves. The beneficial effect, however, was induced by the combination of Al and nutrients. * We suggest that without nutrients roots are not able to synthesize an adequate amount of citrate that is required for transporting Al to the leaves. High Al levels in the plant tissues and/or an interaction of Al with particular nutrient elements in the apoplast of root cells appear to be essential to exert the beneficial effect of Al.     

Evidence for the denaturation of recombinant hepatitis B surface antigen on aluminium hydroxide gel

Despite the complexity of the subject of protein–alum interactions, a valuable information can be obtained by analyzing the adsorbed and desorbed protein by common physico–chemical methods. In the present work, to approach the adsorption of hepatitis B surface antigen (HBsAg) on alum, the experimental data were supported by complementary analyses of the adsorbed protein by immunoelectron microscopy and the desorbed protein by denaturing size-exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. First, the depletion of HBsAg was investigated. The aspects assessed were the conditions, recovery and chromatographic performance of the desorbed protein. The results obtained strongly suggested the loss of particulate structure of HBsAg after adsorption on alum. This conclusion was further reinforced by direct immunoelectron microscopic visualization of HBsAg in the adsorbed state.     

The influence of Al3+ ion on porcine pepsin activity in vitro

The in vitro effect of Al³⁺ ions in the concentration range 1.7·10^{? 6} M–8.7·10^{? 3} M on pepsin activity at pH 2, via kinetic parameters and its electrophoretic mobility was evaluated. Kinetic study demonstrated the existence of an activation effect of Al³⁺ at pH 2 on pepsin molecule. Kinetic analysis with respect to concentrations of haemoglobin showed that Al³⁺ ions increase the maximal velocity (V_max) and k_cat values rather than apparent affinity for substrate (K_S) implying the non-competitive nature of activation which indicated that aluminium was a non-essential activator of partial non-competitive type. The values of the equilibrium constants K_S and K_mA for dissociation of corresponding complexes were evaluated as 0.904 ± 0.083 mM and 8.56 ± 0.51 μM, respectively. Dissociation constant K_A, of activator from enzyme-activator complex calculated via kinetic and direct measurement of Al³⁺ binding data, as well as activation constant A₅₀, the activator concentration that gives a rate equal to half at a saturating concentration of activator, were found to be 8.82 ± 0.90 μM, 8.39 ± 0.76 μM, and 8.05 ± 0.48 μM respectively. Native PAGE electrophoresis shows the decrease in electrophoretic mobility of pepsin and confirms modification of the electric charge and conformational changes of pepsin caused by bound Al³⁺ on the pepsin molecule. Al³⁺ induced conformational changes of pepsin were verified by UV-VIS and IR spectra. Moreover, the absence of conformational changes in the haemoglobin molecule in the presence of Al³⁺ ions confirms that the obtained activation is a consequence of conformational changes caused only in the pepsin molecule.     

Phosphate adsorption on bottom sediments of the Rio de la Plata

A study of the phosphate adsorption onto the bottom sediments of the Rio de la Plata has been made with the aim to understand the dynamics of this compound in the fluvio-marine system. Previous to the chemical analysis of the phosphate content, an extraction of the different adsorbed phosphate fractions have been made. In addition to phosphate, calcium, iron and aluminium in the sediment samples were determined. The phosphate is associated to the fine fractions of the sediments and good correlations with Al and Fe content in the bottom sediments were found. There is a relative decrease of the adsorbed phosphate on the bottom sediment in the areas where the influence of the marine water is more conspicuous; it is explained by the pH increase of the estuary waters due to the mixture with the marine waters. A hypothesis about the role of the ionic strength and the pH on the phosphate adsorption process is suggested.     

The imaging and quantification of aluminium in the human brain using dynamic secondary ion mass spectrometry (SIMS).

Dynamic secondary ion mass spectrometry (SIMS) has been utilised to study the post-mortem distribution of aluminium in air-dried frozen sections from unfixed, unstained human brain in order to minimise contamination of the tissue and avoid redistribution and extraction of endogenous tissue aluminium. Substrates, sputter-coated with silver, were found to be free of focal aluminum surface contamination and thus minimised substrate induced artefacts in the tissue aluminium ion image. SIMS imaging of aluminium secondary ions at a mass resolution that eliminated the major molecular interferences, combined with a photomontage technique provided a unique strategy for studying aluminium distribution in tissue unrivalled by other spatially resolved microanalytical techniques such as laser microprobe mass spectrometry or X-ray microanalysis. Using this strategy, high densities of focal aluminium accumulations have been demonstrated in the cerebral cortex of the majority of chronic renal dialysis patients studied. In contrast, such aluminium accumulations were absent in control patients. SIMS imaging of aluminium appeared to provide much better discrimination between the dialysis patient group and the control group than one of the most widely used techniques for measuring aluminium in bulk samples, graphite furnace atomic absorption spectrometry. Preliminary studies have shown the feasibility of quantifying focal aluminium SIMS images obtained from brain tissue using aluminium-loaded brain homogenates as reference standards.     

Prediction of chlortetracycline adsorption on the Fe3O4 nanoparticle using molecular dynamics simulation

Abstract

Molecular dynamics (MD) simulation was applied to investigate the adsorption mechanism of chlortetracycline (CTC) antibiotic molecule as the aqueous pollutant on the Fe₃O₄ nanoparticle (NP). Two different NP sizes with a diameter of about 1.4?nm and 3.5?nm were selected. Initially, the stability of both NPs in water was investigated by calculating radial distribution function curves of NP atoms. Simulation results confirmed the stable crystallographic structures of both NPs. However, small NP induce greater structural stabilization. Then, CTC molecules were adsorbed on NPs surface in various pollutant concentrations. Electrostatic and hydrogen bond were the major types of interactions between CTC molecules and the adsorbent surface. CTC molecules formed a complex with NP surface from their amine side chains; while they were parallel to each other in their aromatic rings and π-π bond between two CTC molecules was formed. Diffusion rate of CTC molecules could predict the adsorption mechanism. At lower concentration of CTC, CTC molecules tend to adsorb on the NP surface. At these concentrations, the diffusion rate of CTC was high. By increasing the CTC concentration, the pollutant agglomeration was enhanced which decreased the diffusion rate. At this time, the surface of NP was saturated. In addition, the results of isotherm curves showed that CTC adsorption on small NPs could be defined with both Langmuir and Freundlich isotherm models, while Freundlich isotherm model was more appropriate for larger NPs. In conclusion, observations confirmed that MD simulation could successfully predict the behavior of CTC adsorption on the Fe₃O₄ NP surface.

Communicated by Ramaswamy H. Sarma     

Effects of nitrogen fertilizers on the aluminium contents of mature tea leaf and extractable aluminium in the soil

Increasing rates of nitrogenous fertilizer decreased the aluminium contents in mature leaf of tea but increased the extractable soil aluminium in the 0–30 cm soil depth. Use of NPKS 25:5:5:5 or NPK 20:10:10 did not affect the order of responses. Different rates of potash had no effect on leaf aluminium levels. The concentrations of aluminium in the mature leaf were well above the minimum required for tea nutrition. The increase in extractable soil aluminium due to higher nitrogen rates in part explains the generally low potassium and calcium contents in the leaf and soil.     

The role of suspended matter in the distribution of dissolved inorganic phosphate,iron and aluminium in the Ems estuary

In winter 1992/1993, a persistent local maximum in fluorescence, dissolved iron, dissolved aluminium and dissolved inorganic phosphate was found, upstream of the turbidity maximum in the freshwater zone of the Ems estuary (The Netherlands — Federal Republic Germany; western Europe). Upstream of this local maximum values ranged from 6 to 9 rel. units fluorescence, 0.9 to 2.4 μmol dm⁻³ iron, 0.5 to 0.7 μmol dm⁻³ aluminium and 0.6 to 2.3 μmol dm⁻³ dissolved inorganic phosphate. Within the maximum peak values of 24 rel. units fluorescence, 5.8 μmol dm⁻³ iron, 1.4 μmol dm⁻³ aluminium and 8.3 μmol dm⁻³ dissolved inorganic phosphate were observed. Downstream, fluorescence (indicator of dissolved organic carbon) showed conservative mixing with sea water, whereas dissolved iron, aluminium and dissolved inorganic phosphate did not. Dissolved aluminium and iron were quickly removed from solution to reach values of ∼100 nmol dm⁻³ aluminium and ∼0.3 μmol·dm⁻³ Fe at salinities of approximately 7 PSU. Further seaward iron concentrations gradually decreased to levels below 0.04 μmol dm⁻³. Dissolved aluminium first decreased to ∼20 nmol dm⁻³ at 29 PSU and increased again to concentrations of 30–44 nmol dm⁻³ at higher salinities. Dissolved inorganic phosphate, however, first decreased to upstream concentrations before reaching a secondary peak in the mid-estuarine reaches. At salinities >25 PSU dissolved inorganic phosphate mixed conservatively with sea water. It is hypothesized that adsorption-desorption equilibria are responsible for the local maximum values of fluorescence (DOC), iron, aluminium and dissolved inorganic phosphate. The similarity between the observed curves suggests a common underlying process, possibly related to the adjustment of new equilibria between suspended matter of marine and riverine origin.     

Influence of root-induced pH on the solubility of soil aluminium in the rhizosphere

Increase in solubility of soil aluminium (Al) as a result of root-induced decrease of soil pH was studied. Soil samples of known distances from the roots of NH₄-N fertilized Ryegrass were analyzed for pH and aluminium extractable with 0.01 M CaCl₂. Results showed that though no Al was found in bulk soil (pH 6.8), its concentration in the vicinity of roots increased to 0.023 mM with a concomitant decrease of soil pH from 6.8 to 4.4.     

Comparison of techniques for determining the effect of aluminium on the growth of,and the inheritance of aluminium tolerance in wheat

The effect of Al on the growth of plants derived from the F3 generation of a cross between Al tolerant (Waalt) and Al sensitive (Warigal) wheat cultivars, grown in low ionic strength nutrient solutions, were assessed by a number of methods viz; root length and haematoxylin stain after 3 days exposure to Al and plant top and root yields, and root length and visual assessment for Al damage after 4 weeks growth.Of these methods haematoxylin stain (3 days) and visual assessment at 4 weeks identified the same plants as being sensitive or tolerant to Al and clearly segregated the 2 populations. Consequently these 2 methods were used as standard techniques to determine the ability of the other methods to distinguish between tolerant and sensitive plants.The ratio of plant top: root yields clearly segregated the 2 populations. The 2 populations could not be clearly distinguished based on plant top or root yields, or on root length either after 3 days or 4 weeks exposure to Al.Within the population of tolerant plants, root length was significantly correlated with root weight (r²=0.86) and top weight (r²=0.71). None of these relationships were significant for the population of sensitive plants.These techniques were applied in a number of separate experiments on the F2 and F3 populations from a Waalt × Warigal cross. The results indicate that Al tolerance in wheat is inherited by a single gene and that this gene has incomplete dominance.     

铝对荞麦根系的影响

以荞麦为试材,用五种剂量的铝进行土培,发现低浓度(0.435+0.6gAl3+/kg土)的铝能增加荞麦的总根长、根尖数和根系活力,减小根平均直径,降低根质膜透性,对荞麦生长有一定的促进作用;高浓度的铝(0.435+1.2gAl3+/kg土)会使荞麦的根变短、变粗、侧根减少,根系活力下降,根质膜透性升高,明显不利于荞麦的生长发育。     

Effect of Fe/Al Hydroxides on Transport and Retention of Escherichia coli in Saturated Sand Media

The transport of bacteria has been investigated extensively using iron (Fe) (hydr)oxide-coated quartz. However, few studies have investigated the effects of aluminum (Al) (hydr)oxide on the transport of bacteria. In this study, column experiments were conducted to investigate the effects of Fe/Al hydroxides on the transport of Escherichia coli (E. coli) in saturated quartz sand at different pH levels, ionic strengths (IS), and ionic compositions. Fe/Al hydroxide coatings increased the positive charge of quartz, reduced the negative charge, shifted zeta potential in a positive direction, and thus enhanced the retention of E. coli on quartz. The retention of E. coli decreased with increasing pH and increased with increasing IS. These findings were consistent with the theoretical prediction of the Derjaguin, Landau, Verwey and Overbeek (DLVO) interaction energy. Calcium ions improved the retention of E. coli in the column. Since Al-hydroxide-coated quartz had a more positive charge, the retention of E. coli was higher in Al-hydroxide-coated quartz than in Fe-hydroxide-coated quartz. When compared with quartz alone, Fe/Al hydroxide coatings significantly reduced the transport of E. coli, and the inhibitory effect of Al hydroxide was greater than that of Fe hydroxide.     

The effects of surface adsorption on the thermal stability of proteins

The effect of surface adsorption on the structure and stability of proteins is a matter of increasing interest in biotechnology. Therefore, we have examined the effect of adsorption to silica on the thermal stability of 7 proteins employing differential scanning calorimetry (DSC) and front surface fluorescence (FSF) spectroscopy. In general, it was found that surface adsorption decreased the thermal stability of the bound protein. Using lysozyme for further studies, DSC, FSF, and FTIR spectroscopies, as well as enzymatic activity measurements, were used to explore the effect of decreasing surface apolarity on stability. It was observed that increasing surface apolarity produced decreasing stability and increasing structural alteration of the adsorbed protein.     

pH值和Fe、Cd处理对水稻根际及根表Fe、Cd吸附行为的影响

通过营养液-蛭石联合培养试验,设置系列pH值(4.5—7.5)和Fe、Cd处理,研究不同pH值及Fe、Cd浓度对水稻和蛭石表面Fe、Cd吸附的影响。结果表明,不同pH值处理下的根际氧化还原电位和酸度不同,0.9 mg/L Cd处理下的根际氧化势低于0.5 mg/L Cd,50 mg/L Fe处理下的根际酸度高于30 mg/L Fe处理。根表吸附Fe、Cd组分和数量都受根际Eh、pH值制约,根表Fe、Cd吸附量在处理pH值6.0时最低,并分别在处理pH值7.5和处理pH值4.5达到最高。但根系表面对Fe、Cd的吸附机制与蛭石表面不同,蛭石吸附Fe主要为晶态Fe,占到总沉积Fe的73%—87%;水稻根表沉积Fe以非晶态Fe为主,占总沉积Fe的91%—95%;与处理pH值和根际Eh间有显著的相关性(蛭石晶态Fe:ppH=0.011、pEh=0.042;水稻根表非晶态Fe:ppH=0.050、pEh=0.004)。蛭石表面交换态Fe及交换态Cd与处理pH值和Eh间存在显著的相关性(pH值:pFe<0.001、pCd=0.009;Eh:pFe=0.016、pCd=0.002),而根表交换态Fe及交换态Cd仅与处理pH值间有显著的相关性(pFe=0.007,pCd=0.048)。不同Fe、Cd浓度处理对根际Eh、pH值的升降和根表Fe、Cd吸附均有影响。与对照相比,增Cd处理可以降低根际Eh和升高pH值,减少溶液Cd浓度并增加根表Cd吸附量;增Fe处理则可以升高根际Eh和降低pH值,增加溶液Fe、Cd浓度并减少根表Fe、Cd吸附量。这是水稻应对Fe、Cd浓度胁迫的生理反应之一。     

Interfacial effect of extremely low frequency electromagnetic fields (EM-ELF) on the vaporization step of carbon dioxide from aqueous solutions of body simulated fluid (SBF)

Spontaneous processes in an aqueous solution of body simulated fluid (SBF) were monitored in closed vessel for a period of 1 month at 310 K, at atm pressure, and initial pH of 7.2, both with and without exposure to a square pulsed extremely low frequency electromagnetic fields (EM-ELF) of 250 microT, repeated at 75 Hz. The most important findings are that the SBF surface tension (gamma), evaluated under the EM-ELF field, is lower than the corresponding value measured without EM-ELF at any time. Furthermore, the pH of the exposed SBF is always more basic than that of the unexposed solution. As a consequence, when the EM-ELF is applied, calcium phosphate salts do not precipitate from the SBF solution for a period as long as 30 days. Behind all these experimental evidences there is only one mechanism: the vaporisation from the SBF-air interface of the CO(2)(aq) dissolved into the aqueous electrolyte solution. Thermodynamic analysis of these results establish that, at any given time, the difference, Delta, between the measured surface tensions with and without EM-ELF applied, gives the work of the electromagnetic forces to change the extent at which the CO(2)(aq) adsorbs at the liquid-air interface. It has been demonstrated that the work supply per second and per unit of area by the electromagnetic forces, 3.73 x 10(-10) mJ/s cm(2), is very near to the experimental slope in the plot Delta vs. t 1.7 x 10(-10) mJ/s cm(2). This leads to the conclusion that the EM-ELF fields have an interfacial effect on the concentration value of the CO(2) (aq) at the SBF-air interface. Because of that, the EM-ELF field is enhancing the CO(2) vaporisation rate; thus any other steps, which are a consequence of this mechanism, are changing. These results allow explanation of previous experiments concerning the precipitation of calcium carbonate from flowing hydrogen carbonate aqueous solution in the temperature range 353-373 K at a pressure of 0.1 MPa under the effect of static magnetic fields.     

Aluminium-induced changes in the surface and micropore properties of wheat roots: a study using the water vapor adsorption-desorption technique

The geometric and energetic characteristics of root surfaces of two wheat (Triticum L.) varieties, Al tolerant (Inia 66/16) and Al sensitive (Henika), were estimated from experimental water vapor adsorption–desorption data. Roots stressed for around 1 week at pH 4 without and with a toxic aluminium level (0.741 mol m^–3) were studied at the tillering and shooting stages. Roots grown continuously at pH 7 were taken as control. The surface properties of the pH 4 stressed roots were apparently the same as those of the control roots whatever the root age. For the roots of both varieties, the surface area and total micropore volume increased markedly after aluminium treatment. The average micropore radius increased significantly for the sensitive wheat, whereas it increased only slightly for the resistant one. Under Al treatment the number of large pores increased while small pores were fewer for both plants, indicating a possible alteration of the build-up of root tissue. The root surface pores were fractal. The fractal dimension of the sensitive wheat roots decreased under Al treatment, whereas for the resistant wheat this remained apparently unchanged. The adsorption energy distribution functions had different shapes for the sensitive and the resistant wheat varieties: the sensitive variety had greater number of high energy adsorption centers, which implies that the root tolerance on Al stress may be connected with lower polarity of the surface.     

Antibody adsorption on the surface of water studied by neutron reflection

Surface and interfacial adsorption of antibody molecules could cause structural unfolding and desorbed molecules could trigger solution aggregation, resulting in the compromise of physical stability. Although antibody adsorption is important and its relevance to many mechanistic processes has been proposed, few techniques can offer direct structural information about antibody adsorption under different conditions. The main aim of this study was to demonstrate the power of neutron reflection to unravel the amount and structural conformation of the adsorbed antibody layers at the air/water interface with and without surfactant, using a monoclonal antibody ‘COE-3′ as the model. By selecting isotopic contrasts from different ratios of H₂O and D₂O, the adsorbed amount, thickness and extent of the immersion of the antibody layer could be determined unambiguously. Upon mixing with the commonly-used non-ionic surfactant Polysorbate 80 (Tween 80), the surfactant in the mixed layer could be distinguished from antibody by using both hydrogenated and deuterated surfactants. Neutron reflection measurements from the co-adsorbed layers in null reflecting water revealed that, although the surfactant started to remove antibody from the surface at 1/100 critical micelle concentration (CMC) of the surfactant, complete removal was not achieved until above 1/10 CMC. The neutron study also revealed that antibody molecules retained their globular structure when either adsorbed by themselves or co-adsorbed with the surfactant under the conditions studied.     

石油焦基高比表面积活性炭对废水中CODCr的吸附能力

探讨了高比表面积活性炭(HSAAC)吸附水中COD_Cr时,活性炭用量、pH值和吸附时间等因素对COD_Cr吸附量和去除率的影响。实验结果表明,HSAAC用量越大,去除COD_Cr效果越好。当HSAAC用量为2.0g·L^-1,pH=3时,去除率达到78%以上;在酸性条件下HSAAC对COD_Cr的去除效果较好;HSAAC对废水中COD_Cr的吸附发生在前30min;COD_Cr浓度低于60mg·L^-1时,处理后COD_Cr的残余质量浓度低于地表水环境质量Ⅰ类标准(15mg·L^-1)。用碱再生HSAAC,一次再生率达94.22%,二次再生率达到了86.90%。说明高比表面积活性炭在适宜条件下对COD_Cr具有较好的吸附性能和良好的再生效果。