Interaction of bovine serum albumin (BSA) with ionic surfactants evaluated by electron paramagnetic resonance (EPR) spectroscopy

EPR spectra of 5- and 16-doxyl stearic acid nitroxide probes (5-DSA and 16-DSA, respectively) bound to bovine serum albumin (BSA) revealed that in the presence of ionic surfactants, at least, two label populations coexist in equilibrium. The rotational correlation times (tau) indicated that component I displays a more restricted mobility state, associated to the spin labels bound to the protein; the less immobilized component 2 is due to label localization in the surfactant aggregates. For both probes, the increase of surfactant concentration leads to higher motional levels of component 1 followed by a simultaneous decrease of this fraction of nitroxides and its conversion into component 2. For 10 mM cethyltrimethylammonium chloride (CTAC), the nitroxides are 100% bound to the protein, whereas at 10mM N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and sodium dodecyl sulfate (SDS) the fractions of bound nitroxides are reduced to 18% and 86%, respectively. No significant polarity changes were observed in the whole surfactant concentration range for component 1. Moreover, at higher surfactant concentration, component 2 exhibited a similar polarity as in the pure surfactant micelles. For 16-DSA the surfactant effect is different: at 10mM of HPS and CTAC the fractions of bound nitroxides are 76% and 49%, respectively, while at 10 mM SDS they are present exclusively in a micellar environment, consistent with 100% of component 2. Overall, both SDS and HPS are able to effectively displace the nitroxide probes from the protein binding sites. while CTAC seems to affect the nitroxide binding to a significantly smaller extent. (C) 2008 Elsevier B.V. All rights reserved.

Effects of a quantum measurement on the electric conductivity : Application to graphene

We generalize the standard linear-response (Kubo) theory to obtain the conductivity of a system that is subject to a quantum measurement of the current. Our approach can be used to specifically elucidate how back-action inherent to quantum measurements affects electronic transport. To illustrate the utility of our general formalism, we calculate the frequency-dependent conductivity of graphene and discuss the effect of measurement-induced decoherence on its value in the dc limit. We are able to resolve an ambiguity related to the parametric dependence of the minimal conductivity.

Síntese e caracterização de catalisadores de LaNiO3 não suportados e suportados em Al2O3 e ZrO2 para a reforma a vapor do metano

Ionic oxides with ABO3 structure, where A represents a rare earth element or an alkaline metal and B is a transition metal from group VIII of the periodic table are potential catalysts for oxidation and good candidates for steam reforming reaction. Different methods have been considered for the synthesis of the oxide materials with perovskite structure to produce a high homogeneous material with low amount of impurities and low calcination temperatures. In the current work, oxides with the LaNiO3 formula had been synthesized using the method of the polymeric precursors. The thermal treatment of the materials took place at 300 ºC for 2h. The material supported in alumina and/or zirconia was calcined at 800 ºC temperature for 4h. The samples had been characterized by the following techniques: thermogravimetry; infrared spectroscopy; X-ray diffraction; specific surface area; distribution of particle size; scanning electron microscopy and thermo-programmed reduction. The steam reforming reaction was carried out in a pilot plant using reducing atmosphere in the reactor with a mixture of 10% H2-Argon, a mass about 5g of catalyst, flowing at 50 mL.min-1. The temperature range used was 50 - 1000 oC with a heating rate of 10 oC.min-1. A thermal conductivity detector was used to analyze the gas after the water trapping, in order to permit to quantify the consumption of hydrogen for the lanthanum nickelates (LaNiO3). The results showed that lanthanum nickelate were more efficient when supported in alumina than when supported in zirconia. It was observed that the methane conversion was approximately 100% and the selectivity to hydrogen was about 70%. In all cases were verified low selectivity to CO and CO2

On the interaction of bovine serum albumin with ionic surfactants: Temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Transporte de juvenis de curimbatá Prochilodus lineatus em diferentes densidades

Transportation of curimbata Prochilodus lineatus juveniles in different densities. Tins study evaluated the effects of curimbata Prochilodus lineatus transportation in three densities (100, 150 and 250 g L-1) on survival, metabolic, ionic and hematological (red series) variables Curimbata juveniles were transported in plastic bag during six hours, and sampled before packing, immediately after die arrival, 24 and 96 hours after transportation During recovery, higher mortality was seen in fish transported in die highest density Water variables, such as conductivity and total ammonia, presented increased values as density increased (p < 005). whereas the opposite occurred with dissolved oxygen Glucose level observed in the arrival was high, significantly reducing after 96 hours Among ionic variables, chloride decreased in higher fish densities and according to sampling times Red series hematological variables, such as hematocrit, red blood cell and hemoglobin, Increased in arrival, but diminished 96 hours after transportation There were no significant differences in the interaction between density and time of sampling for mentioned variables 250 g L-1 density induced the highest mortality rate and the worst variables values measured 96 hours of recovery after the stressing event was enough to return to initial values for hematological variables, but was not sufficient to return to initial values for metabolic and ionic variables.

Electrical conductivity of soybean seeds after storage in several environments

Membrane integrity, as measured by electrical conductivity (EC), is suggested as an indicator of seed vigor in soybean [Glycine max (L.) Merrill] seeds. This study evaluated the effect of storage time and temperature on EC of six soybean seed lots (two lots each of high, medium and low vigor). All seed lots were adjusted to 120 g kg(-1) seed moisture, sealed in aluminum foil packets and placed in storage at 10 and 20 degreesC or stored unsealed in multi-wall paper bags in warehouse (WH) conditions at Lexington, KY, USA for 486 days. Four of the six seed lots were also stored unsealed at 10 degreesC. All seed lots were sampled at 3-month intervals and evaluated for seed moisture (SMC), standard germination (SG) and vigor [accelerated aging (AA) and EC]. After 91 and 204 days in storage, samples initially stored at 20 degreesC and WH were moved to 10 degreesC and sampled at the same intervals. Seed moisture content for unsealed samples equilibrated at 107 g kg(-1) (+/-9 g kg(-1)) in both the WH and 10 degreesC environments. No change in SG occurred for seeds stored sealed (120 g kg(-1)) at 10 degreesC, except for the low vigor seed lots which declined significantly at the last sample date. The AA germination declined significantly for all, seed lots stored sealed at 10 degreesC, however the EC did not change during the same storage period. Seeds stored sealed at 20 degreesC and unsealed in the WH showed rapid declines in AA and SG and significant increases in EC. When these seeds were moved to 10 degreesC, however, the AA continued to decline while the EC remained at the same level (no significant change) for the remainder of the seed storage period. Thus whilst the AA declined in all environments, the EC only increased at higher temperatures (20 degreesC, WH) but showed little change during storage at 10 degreesC. Thus, precautions must be taken if using EC to measure soybean seed vigor following storage at 10 degreesC.

Electrical conductivity of the seed soaking solution and soybean seedling emergence

Vigor of soybean [Glycine max (L.) Merrill] seeds can be evaluated by measuring the electrical conductivity (EC) of the seed soaking solution, which has shown a satisfactory relationship with field seedling emergence, but has not had aproper definition of range yet. This work studies the relationship between EC and soybean seedling emergence both in the field and laboratory conditions, using twenty two seed lots. Seed water content, standard germination and vigor (EC, accelerated aging and cold tests) were evaluated under laboratory conditions using -0.03; -0.20; -0.40 and -0.60 MPa matric potentials, and field seedling emergence was also observed. There was direct relationship between EC and field seedling emergence (FE). Under laboratory conditions, a decreasing relationship was found between EC and FE as water content in the substrate decreased, Relationships between these two parameters were also found when -0.03; -0.20 and -0.40 MPa matric potentials were used. EC tests can be used successfully to evaluate soybean seed vigor and identify lots with higher or lower field emergence potential.

Seed-borne pathogens and electrical conductivity of soybean seeds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Eletrical conductivity and deterioration of soybean seeds exposed to different storage conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical conductivity testing of corn seeds as influenced by temperature and period of storage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical conductivity as an indicator of pea seed aging of stored at different temperatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical conductivity and soybean seedling emergence

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrical conductivity and mineral composition of the imbibition solution of bean seeds during storage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical conductivity test in the evaluation of physiological quality in seeds of Zeyheria tuberculosa

The electrical conductivity test is still an excellent tool to evaluate the effect of seeds of various forest and agricultural species and recent studies have been conducted aiming at verifying its application in forest seeds. The objective of this study was to establish a specific methodology to test the electrical conductivity of forest seeds of Zeyheria tuberculosis. Four lots of seeds were used, which were submitted to the germination test, evaluating the percentage of germination, germination speed index and dry mass of seedlings. For the electrical conductivity test, five replicates of 20 seeds installed in three volumes of deionized water (75, 100 and 125 mL) were used and eight periods for seed imbibitions (2, 4, 6, 12, 18, 24, 48 and 72 hour) at 25 degrees C were allowed. The statistical design used was completely random; the comparison of means was performed by Tukey test at 5 % probability. Lot II showed higher germination percentage and speed. The electrical conductivity test allows discrimination of the same batch by the germination test under laboratory conditions. It was possible to separate the seed lot presenting better physiological quality (lot II) from among the other lots. It was recommended the use of 75 or 125 mL of deionized water at a temperature of 25 degrees C to perform the electrical conductivity test.

Automated system of seedling image analysis (SVIS) and electrical conductivity to assess sun hemp seed vigor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)