Redistribution extractives

Test preparation for both methods is similar. It comprises an extraction by a water-acetone mixture with its further degreasing protein isolation and redistribution of aflatoxin B into chloroform, concentrating by means of evaporation of the dissolvent on the rotary evaporator (t = 40°C). 

Impurities present in the organic phase may sometimes be removed by backwashing. The organic extract when shaken with one or more small portions of a fresh aqueous phase containing the optimum reagent concentration and of correct pH will result in the redistribution of the impurities in favour of the aqueous phase, since their distribution ratios are low most of the desired element will remain in the organic layer. 

Another possibility for plants to influence the P cycle is the hydraulic redistribution of water. This is the redistribution of water from wet to dry soil areas via the roots, which has been suggested to have an impact on the availability of P due to better mobility of inorganic P in wet soil (Lambers et al. 2006). McCulley et al. (2004) found that the concentration of extractable P was greater at depth than in the top meter of the soil in several arid and semi-arid systems in the southwestern USA and that nutrients were uplifted from this depth. They proposed that hydraulic redistribution of water from the soil surface to depths up to 10 m by roots was the mechanism by which P and other nutrients were mobilized and could be taken up by plants. 

The fourth type of mediator-based cation optical sensing is using potential sensitive dye and a cation selective ionophore doped in polymer membrane. Strong fluorophores, e.g. Rhodamine-B C-18 ester exhibits differences in fluorescence intensity because of the concentration redistribution in membranes. PVC membranes doped with a potassium ionophore, can selectively extract potassium into the membrane, and therefore produce a potential at the membrane/solu-tion interface. This potential will cause the fluorescent dye to redistribute within the membrane and therefore changes its fluorescence intensity. Here, the ionophore and the fluorescence have no interaction, therefore it can be applied to develop other cation sensors with a selective neutral ionophore. 

Melan, M. A. and Slnder, G. (1992) Redistribution and differential extraction of solnble proteins in permeabilized cnltnred cells implications for immunofluorescence microscopy. J. Cell Sci. 101, 731-743. 

Permeabilization of cells with 0.1-0.2% detergent after paraformaldehyde fixation can leave an uneven cytoplasmic distribution of the labeled proteins, and some of the larger proteins are redistributed to the nuclei. Extraction with 1 % de tergent prior to fixation removes most, but not always all of the exogenous proteins from the cell remnants. 

Even if the metal cation exchanged zeolite is not dehydrated, the introduction of the ligand or its precursors frequently requires thermal treatment, which can redistribute the cations within the zeolite. Not all metal ions will become com-plexed and their presence can complicate the characterization of the materials as well as the interpretations of catalytic reactions. In principle, the uncomplexed metal ions should be removed by back-extraction. Unfortunately, however, this is a requirement more frequently honored in the breach, rather than the observance. 

While the circumstances of operation of such a device might seem to permit direct application of the results obtained on small columns to large ones, there are apparently some difficulties. In columns as large as 24 in. in diameter, for example, considerable channeling may be observed, and this may lead to as much as a 50% decrease in extraction efficiency (W2). For such columns, special redistribution plates have been developed which overcome this tendency (W2). 

The combination of low-resolution and spectral unzipping into noninteracting polyads enables systematic, model-free surveys of deperturbed Franck-Condon factors, deperturbed zero-order energy levels, and trends in intramolecular vibrational redistribution (IVR) rates and pathways [3]. The H[ res,/i polyad model permits extraction of the most important resonance strengths directly from fits to a few polyads [6-8]. Once these anharmonic... 

To dearly distinguish between these two modes of solvent penetration of the gel, we immersed poly(acrylamide-co-sodium methacrylate) gels swollen with water and equilibrated with either pH 4.0 HQ or pH 9.2 NaOH solution into limited volumes of solutions of 10 wt % deuterium oxide (DzO) in water at the same pHs. By measuring the decline in density of the solution with time using a densitometer, we extracted the diffusion coefficient of D20 into the gel using a least squares curve fit of the exact solution for this diffusion problem to the data [121,149]. The curve fit in each case was excellent, and the diffusion coefficients obtained were 2.3 x 10 5cm2/s into the ionized pH 9.2 gel and 2.4 x 10 5 cm2/s into the nonionized pH 4.0 gel. These compare favorably with the self diffusion coefficient of D20, which is 2.6 x 10 5 cm2/s, since the presence of the polymer can be expected to reduce the diffusion coefficient about 10% in these cases [150], In short, these experiments show that individual solvent molecules can rapidly redistribute between the solution and the gel by a Fickian diffusion process with diffusion coefficients slightly less than in the free solution. 

In common with other sequential extraction procedures, the BCR scheme suffers from a degree of non-specificity (Whalley and Grant, 1994 Coetzee et d., 1995) and redistribution of analytes during extraction (Raksasataya et d., 1996). Some success in limiting lead redistribution by addition of cryptand 2.2.2 or nitriloacetic acid to the acetic acid in Step 1 has been reported, but the effectiveness of the complexing agent was found to be strongly dependent on the bulk composition of the model soil system studied (Raksasataya et d., 1997). 

Raksasataya, M., Langdon, AG. and Kim, N.D. (1996) Assessment of the extent of lead redistribution during sequential extraction by two different methods. Anal. Chim. Acta, 332,1-14. 

Two experimental problems have been recognised in the application of sequential extractions for PTMs fractionation in soil and sediments. One is the PTMs readsorption and redistribution among phases during extraction, meaning that PTMs... 

For completion of the discussion it is useful to remind the reader that the delivery of 02 to working muscles, and the extraction of 02 by working muscles, must be closely integrated with the metabolic adjustments described above. That indeed is the case, and it is of course well known that aerobic training induces an adaptive increase in the maximum cardiac output and thus in the total amount and total rate of 02 delivered to muscle. Although in theory the delivery of 02 to muscles could also be increased by preferential perfusion (i.e., redistribution of cardiac output), this mechanism does not appear to be utilized. So the question arises Does the increase in cardiac output during aerobic exercise proceed in step with the overall increase in maximum 02 uptake rates The answer turns out to be negative. 

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