Conformational states of sunflower (Helianthus annuus) Helianthinin: effect of heat and pH

The structure and solubility of helianthinin, the most abundant protein of sunflower seeds, was investigated as a function of pH and temperature. Dissociation of the 11S form (hexamer) into the 7S form (trimer) gradually increased with increasing pH from 5.8 to 9.0. High ionic strength (I = 250 mM) stabilizes the 11S form at pH > 7.0. Heating and low pH resulted in dissociation into the monomeric constituents (2-3S). Next, the 7S and 11S forms of helianthinin were isolated and shown to differ in their secondary and tertiary structure, and to have denaturation temperatures (T(d)) of 65 and 90 degrees C, respectively. Furthermore, the existence of two populations of the monomeric form of helianthinin with denaturation temperatures of 65 and 90 degrees C was described. This leads to the hypothesis that helianthinin can adopt two different conformational states: one with T(d) = 65 degrees C and a second with T(d) = 90 degrees C.     

In vivo antifungal activity of the essential oil of Bupleurum gibraltarium against Plasmopara halstedii in sunflower

The antifungal activity of the essential oil of the aerial parts of Bupleurum gibraltarium was evaluated against Plasmopara halstedii. Fungus spores were inoculated in sunflower seedlings, previously treated with several essential oil solutions, and the sporulation percentage was measured after an 11-day treatment. The oil at a concentration of 5.0 mL/L clearly inhibited the fungus sporulation. The contact between fungus sporangia and essential oil was minimized, so it seems that the oil pretreatment could activate the defense response of the sunflower seedlings against the pathogen invasion. The main compounds in the oil were sabinene (31.1%), alpha-pinene (15.6%), and 2,3,4-trimethylbenzaldehyde (10.9%), among a total of 65 components identified.     

Aroma extract dilution analysis. Precision and optimal experimental design

The odor thresholds of 12 different compounds have been determined in an AEDA experiment using a panel composed of 8 individuals. Only in one case is the distribution of thresholds among judges significantly different from the log-normal. The cause of that departure from normality seems to be a cross adaptation rather than anosmia. The standard deviations (SD) range from 2(0.7) to 2(4.1), with 2(1.8) as average. If the AEDA is carried out at a dilution rate, R, and dilution R(P) (where P = 0, 1, 2.) is the last one at which a compound was detected by a judge, the flavor dilution (FD) factor that should be provided for that judge is R(P+0.5). In the case where several judges carry out the AEDA, the FD for a given compound should be the geometric mean of the FD provided by all the judges. The SD of the distribution of FDs is related to that of the distribution of odor thresholds, but is strongly influenced by the dilution rate, R, being higher with higher R values. The relationship between both SDs can be used to determine the expected precision (measured as the geometric length of the 95% confidence interval) of the result of an AEDA experiment as a function of the dilution rate, the number of judges, and the SD of the distribution of thresholds. Different simulations have shown that in most cases, a dilution rate of 10 is the best option, and that lower dilution rates are advantageous only if the analyzed solution contains compounds with a very narrow distribution of thresholds.     

Coriander essential oil composition from two genotypes grown in different environmental conditions

The objective was to study the essential oil composition of coriander fruits in plants growing in environments differing in soil conditions and weediness level. Factorial field experiments were conducted in two locations from the Rolling Pampas, Argentina, and two coriander landraces (European and Argentinean) were tested under two levels of nitrogen fertilization and weediness. Data were evaluated with uni- and multivariate techniques. The variation in the oil composition was related to the relative proportion of the constituents and not to the presence/absence of a particular component. Weather conditions in 1997 favored linalool and camphor in both landraces. Location, fertilization, and weediness also affected the chemical profile. The European landrace showed a more stable concentration of the major components than the Argentinean landrace. These results, which show the relationships between some environmental conditions and the essential oil composition, are useful in the development of innovative strategies aimed to improve oil composition and to manage crop pests.     

INCREASED CADMIUM AVAILABILITY TO CROPS ON A SEWAGE-SLUDGE AMENDED SOIL

Analysis of spatial distribution of sewage-sludge born cadmium on the experimental plot revealed positive correlation of total cadmium and organic matter. Soil pH fluctuated randomly on the field. ‘Bioavailable’ concentrations, as determined by NH₄-acetate extraction, were closely correlated to the total cadmium levels, and only negligible effects of pH and/or organic matter fluctuations were recorded. Desorption model using modified Freundlich isotherm was applied to predict risks of cadmium solubilization at different conditions. Simulations revealed that the organic matter content within the ranges found at the experimental field cannot support a proper immobilization of cadmium at pH-range observed at the field. The phenomenon was explained by ineffective care for the soil in the past.     

A rapid method for the determination of chlorine, phosphorus, and sulfur in flours of grains and legumes using wavelength dispersive x-ray flourescence spectrometry

A rapid method for the determination of chlorine, phosphorus, and sulfur in commercial flours of wheat, barley, maize, rice, field bean, and soybean by wavelength dispersive x-ray fluorescence spectrometry has been developed. The flours are strained through a 425 microns sieve, then pelletized and measured. The total analysis time for the quantitation of chlorine, phosphorus, and sulfur is less than 20 min per sample. Calibration is carried out using a standard additions method with mixed standards. The method is accurate and precise, and appears to be adequate for routine analyses.     

Removal of Copper and Cadmium Ions from Diluted Aqueous Solutions by Low Cost and Waste Material Adsorbents

The sorption of copper and cadmium ions using activated carbon,kaolin, bentonite, diatomite and waste materials such as compost,cellulose pulp waste and anaerobic sludge as sorbents is reported. Equilibrium isotherms were obtained for the adsorption of these metals in single and binary solutions. Bentonite presented the highest adsorption capacities for both copper and cadmium. A competitive uptake was observed when both metals are present; copper being preferentially adsorbed by all materials with theexception of anaerobic sludge. Equilibrium data were fitted toLangmuir and Freundlich models, with satisfactory results for most of the adsorbent-metal systems studied.Of all the adsorbents studied, bentonite and compost presentedthe highest removal efficiencies, reaching 99% for copper whencadmium is also present, for initial solution concentrations ofup to 100 mg L^-1. Anaerobic sludge has a greater preferencefor cadmium, even in the presence of copper, with removal efficiencies of 98% for similar concentrations to those mentioned above.     

Speciation of Selected Minor and Major Elements in Oil Ash I. Operationally Defined Chemical Associations and Aqueous Speciation

This study is focused on the speciation of selected elements in oil ash. Our efforts were directed primarily to obtain information on the various forms of vanadium, chromium and nickel. One sample was characterized via its total composition and via its capacity for releasing various elements. The latter was estimated by hot water and nitric acid extractios. A rapid cold water extraction technique has been developed and utilized for sample preparation prior to aqueous speciation by high pressure ion chromatography (HPIC). Results of the HPIC measurements, in agreement with electron spin resonance (ESR) investigations performed on the solid sample, indicate that 38% of the vanadium is present as VOSO₄, 58% of the chromium is Cr₂(SO₄)₃ and 30% of the nickel is NiSO₄. The pH and the redox potential values of the cold water extract support the existence of these forms. Results of a generic study with successive fractionation extractions show the probable existence of oxides, associations with organic matter and aluminosilicate minerals.     

Mineralization of carbon atoms of 14C-2,4-D side chain and degradation ability of bacteria in soil

The time-course of ¹⁴CO₂ formation in chernozem soil samples enriched with 1- or 2-¹⁴C-2, 4-dichlorophenoxyacetic acid (50 μg g g^?1 air-dry soil) was determined during incubation at 28°C. Except for the initial phase of decomposition, when the conversion of carboxyl carbon to ¹⁴CO₂ predominated over that of carbon in position 2, the rates of mineralization of the two carbon atoms of the side chain of the herbicide molecule exhibited no significant difference. The exponential phase of ¹⁴CO₂ evolution lasted from the 3rd to the 21st day of incubation; a semilogarithmic plot of its time dependence was strictly linear. The mineralization activity doubling time in this phase was 89.1 ± 3.6 h with 1-¹⁴CO-2, 4-D and 85.4 ± 5. l h with 2-¹⁴CO-2,4-D. An exponential decrease in mineralization activity was observed after 21 days, probably due to substrate exhaustion. The total proportion of radioactive carbon introduced into the soil in the form of 1- or 2-¹⁴CO-2,4-D and converted into ¹⁴CO₂ during 31 days of incubation was about 33%. Plate counts of bacteria increased during 35 days of incubation from 2.14 × 10⁸ to 2.8 × 10⁸ g^?1. The proportion of bacteria capable of producing ¹⁴CO₂ from the labelled herbicide increased in this period from 4.1 to 86.1%. This increase is probably directly responsible for the immediate onset of mineralization of the herbicide in soil treated previously with it or in soil inoculated with a suspension prepared from a sample previously incubated with the herbicide.     

Arsenic,lead, and uranium concentrations on sediments deposited in reservoirs in the Rio Grande Basin,USA–Mexico border

Purpose

The El Granero reservoir is the last reservoir of the Rio Conchos before it joins the Rio Grande at the Mexico–USA border. This reservoir, together with the San Marcos reservoir, is located in the arid region of Chihuahua, Mexico. High, naturally occurring radioactivity levels, as well as high arsenic (As) concentrations, have been found in both reservoirs. The main goal of this research was to establish the spatial and temporal distribution of trace and radioactive elements in surface sediments and cores collected from these reservoirs.

Materials and methods

Sediment cores were dated using ²¹⁰Pb and ¹³⁷Cs measurements and applying the constant rate of supply (CRS) model. Major, trace, and radioactive elements were determined in surface samples and three sediment cores. Radioactive elements were determined by both alpha and gamma spectrometry. Major and trace elements were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using the EPA 3051a method. Enrichment factors (EF), contamination factors (CF), and pollution load indexes (PLI) were calculated in order to identify the human impact in both reservoirs, whereas the chemical index weathering (CIW) was used to assess differences in the degree of weathering.

Results and discussion

High uranium (U) enrichment (EFs?=?24.9–54.7) was observed in core layers at the San Marcos reservoir, while in surface sediments, this enrichment was lower. The high variability of lead (Pb) and As in sediment cores from the Granero reservoir was attributed to human influence. Arsenic and Pb enrichment differences between entry and exit sediment cores were explained by the filtering capabilities of the elongated shape, the topography, and the presence of plants on the reservoir’s bed. The highest PLI was found at the entrance core of the Granero reservoir.

Conclusions

The natural element concentration levels of As, Pb, and U were established at the Granero reservoir. High EFs for As and Pb suggest an anthropogenic origin of these pollutants at specific time intervals. High U concentrations in the San Marcos area are explained as naturally occurring. The concentrations of As in most of the studied sediments could pose a risk to human health by As ingestion, since they are above the probable effect level (PEL).