Dialysate extraction fraction

Concentric Microdialysis Probe When a microdialysis probe with perfusion fluid flowing at a flow rate of is placed in a bath of analyte of concentration Cr, the microdialysis recovery, also known as dialysate extraction fraction, is described by a balance of the diffusion of the analyte across the microdialysis membrane into the perfusion fluid with the convective flux due to the perfusion flow ... 

A lyophilized preparation of alginate lyase from a dialysed extract of sonicated cells of a Pseudomonas sp. has been separated into three fractions by gel filtration. ... 

Batistic et al. have used similar extraction and purification procedures to obtain from soil active acid and alkaline phosphomonoesterases (and other hydrolases, cellulase, B-glucosidase, invertase and proteinase), Salmine substituted for protamine as a precipitant of humic material from dialysed extracts. In this case complete flocculation of humic compounds was accompanied by extensive (about 60%) losses of enzymic activities from solution. The activities of the precipitated material were low and could not be restored. Enzymes remaining in dialysed supernatants were of enhanced (about ten fold) specific activities, and were further fractionated by... 

Removal of starch impurities About lOOmg of the extracted pectic fractions were dissolved in 30ml of NaOH 0.05M and stirred for 20h at 0°C. The solutions were neutralised by the addition of 0.18ml glacial acetic acid and the pH was adjusted to 4.6. After the addition of I ml of an amyloglucosidase solution (60U/ml) without any detectable side activities, the samples were incubated at 60°C for 3h. Finally, the samples were cooled to room temperature, dialysed (cut-off 12000D) against deionised water (4 C) for 72h and freeze-dried. 

The dipeptidyl carboxypeptidase was prepared from rat lungs. A microsomal fraction was prepared and extracted with detergent (sodium deoxycho-late) and clarified by centrifugation. The supernatant solution was dialyzed against sodium phosphate, and the dialysate was stored frozen. 

The flow rates of the microdialysis experiment are such that samples of 1-10 J,L are typically obtained. At typical perfusion rates, the perfusate is not at equilibrium with the extracellular fluid. As such, the concentration of sample in the dialysate is some fraction of that in the surrounding tissue. This is termed the extraction efficiency and is a function of the delivery or recovery of the probe. Not only are the sample volumes small but also the concentration in the dialysate may be low, typically ranging from 1 pM to 1 lM. Because the recovery is typically less than 100%, the limit of detection of the method should be lower than the lowest concentration expected in the dialysate. This presents a tremendous challenge for the analyst. 

Equation (21.1-14) can be used to estimeie the degree of separation of two solutes by a given dialyzer. For any solute, the fractional extraction into the dialysate, E, of solute from the feed stream is given by... 

By combining Eqs. (21.1-14) and (21.1-1B), fractionel extraction can be obtained as a function of ovVQf for different ratios of feed io dialysate flow rate. These relationships are shown in Fig. 21.1-6. The separation factor in a dialytic process can be considered to be the ratio of the fractional masses of two solutes removed from their commou Teed stream, under a given asi of operating conditions. By applying Eq. (21.1-16) to each solute, we can see diet a is equal to the ratio of the fractional extractions of the two solutes. Thus. Fig, 21.1-6 can be used to estimate the relative separation of two solutes from a keowlcdge of their overall mess transfer coefficients, membrane area, and feed and dialysate Aow rates. 

Extracts from biota samples can be treated with sulphuric acid, can be cleaned up by gel permeation chromatography 27,i38-i40 polyethylene film dialyses " for elimination of the lipid content. Lipids can also be eliminated by alkaline alcohol digestion of the sample.After lipid elimination the extract can be further fractionated by column chromatography on Florisil, alumina/silica, " or silica gel impreg-... 

The LCmodel method has been adapted to analyse data from localised in vivo spectra obtained from the rat brain. The relative distribution of isotopomers in Glu, Gin, and Asp was in excellent agreement with that determined in extracts. Microdialysis and mass-spectrometry have been used to measure the enrichment of extracellular Glu from C-glucose in the rat brain. The fractional 13C enrichment of basal dialysate Glu C5, collected during 0.75 - 1.25 h of [2,5- C]glucose infusion, was 0.263 0.01, which is close to the value obtained in parallel NMR measurements. Localised water-suppressed H-[ C]-NMR has been used to follow the incorporation of [l,6- C]glucose in the rat brain. 

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