Isoelectric separation, distribution

Figure 3. pH diagram with distribution of enzymic activities from isoelectric separation. The fraction volume was 2.3 ml. (2)... 

Electrophoresis plays a key role as an analytical or preparative technique in the characterization of natural organic matter because it gives information about the behavior of these molecular mixtures in controlled solution conditions, depending on both the size and the charge distribution frequency of the analytes in the complex mixture. Historically, the first electrophoretic separations were conducted with environmental colloids and over the years all the techniques based on zone, gel electrophoresis, or isoelectric focusing were used in their different setups to analyze natural organic matter and environmental particles to a minor extent. The goal of... 

Examination of the groupings of Table 7.2 verifies most of the more or less traditional associations between separation methods chromatography with countercurrent distribution and distillation, electrophoresis with rate-zonal sedimentation, isoelectric focusing with isopycnic sedimentation, re-... 

Isoelectric focusing (IEF) is unique among separation processes as it results in a stationary steady state distribution of fractions along the column axis. The final distribution of fractions is independent of their initial distribution. As such, IEF has no analogue in other electrophoretic or chromatographic methods and well deserves its current popularity (2). 

If the five proteins in question 2 were separated in an isoelectric-focusing experiment, what would be their distribution between the positive (+) and negative (-) ends of the gel Indicate the high and low pH ends. 

FNR is distributed between the stroma and the thylakoid membrane of higher plants. Estimates of the proportion bound to the spinach thylakoid membrane vary from 40 to 80% (3,4). FNR is probably attached to the membrane by a specific binding protein of 17 kDa (5). Both stromal and bound forms often show considerable heterogeneity when analysed by SDS and non-denaturing polyacrylamide gel electrophoresis. Indeed, up to 8 forms of spinach FNR have been separated by isoelectric focussing(6). The significance, if any, of these variants is not yet clear. 

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