Electrophoresis, definition

In addition to polymeric support media, capillaries and flowing buffers have been used as support media for electrophoresis. Although these are not used as frequendy, there are definite advantages for certain types of samples and appHcations. 

The, chain voAiantS are characterized by the presence of two abnormal components, an abnormal Hb-F (02 /2) and an abnormal Hb-A (tt2 32) Of these two, the 02 2 component dominates and the 02 32 component Is often difficult to detect. The methods of choice are starch gel electrophoresis and anion-exchange chromatography using DEAE-Sephadex or DE-52 Cellulose. Chain analyses of these Isolated hemoglobin components will lead to a definitive Identification. 

Fig. 22. The diagrams contributing to electrophoresis and the definition of lithe box. The reason why we only retain this class of terms is that we want to allow long-range propagation by the fluid— as shown in Fig. 21—which is clearly impossible if ions a and fi overlap in the box, because this would correspond to multiple scattering processes on particles a and fi.

The possible formation of a dipole is a feature of covalent bonding but it is obvious that an ionic bond results in a definite unequal distribution of electrons within a molecule and such molecules (or ions) are extremely polar. However, the fact that they carry a definite charge enables additional separation techniques to be applied. The rate of migration in an electric field (electrophoresis) and the affinity for ions of opposite charge (ion-exchange chromatography) are extremely valuable techniques in the separation of ionic species. 

Discussions of electrophoretic data handling usually include mention of separation and resolution. Although the two terms are not synonymous, they are often treated as such. In the terminology of separation science, separation refers to the distance between two adjacent band centers. Because bands are seen as being sharply defined with clearly evident blank spaces between adjacent bands, for practical purposes, separation is often taken to be the distance between the top of the faster running of two adjacent bands and the bottom of the slower one. It is the distance between the top of the bottom band and the bottom of the top band. This definition seems preferable to the rigorous one in electrophoresis. 

Although a number of assays and technologies are available to characterize and test protein molecules, such as peptide mapping, protein sequencing, carbohydrate analysis, electrophoresis, ELISA, and mass spectroscopy, they are not as definitive as the methods used for small molecule drugs. Hence, the test for similarity is not as well defined in the case of proteins. However, as... 

As a result of the pharmacopoeial harmonization process, general chapter 2.2.47. of the Ph.Eur. and general chapter 8 of the JP (Capillary Electrophoresis) and general chapter < 1047) of the USP (Biotechnology-Derived Articles — Tests, Capillary Electrophoresis ) have been harmonized to a major extent. At present some minor differences exist between the text and a few equations in the pharmacopoeia. In these chapters, the following definition of CE is given ... 

The simple definition of chitinase activity, EC 3.2.1.14, "hydrolysis of iV-acetyl-D-glucosaminide (l-4)-P-linkages in chitin and chitodextrins", belies the complexity and diversity of this group of enzymes. When chitinolytic organisms are investigated in detail, they are found to produce a range of chitinase activities. Usually these can be separated readily by chromatography or electrophoresis. However, it is more difficult to define their precise activities, chiefly because of the uncertain nature of the available assays for chitinases, with non-linear time courses... 

Equation 6.1 is valid for a macroscopic particle moving in a continuous medium. In electrophoresis where the analyte ion moves in the media where particle size is comparable with that of the analyte size, this is definitely not the case. Also, analyte ions are not spherical and the term of the ionic radius, the value of which is difficult to estimate, becomes ambiguous. Thus, even in... 

Knowledge of the pKa value is crucial for analyzing both lipophilicity and solubility of ionizable compounds, as discussed above. Ionization equilibria also affect several toxicokinetic parameters, such as intestinal absorption, membrane permeability, protein binding, and metabolic transformations. Therefore, much research has been invested in developing both experimental and computational tools for pKa determination. Experimentally, two high-throughput methods exist spectral gradient analysis and capillary electrophoresis. However, the most definitive methods are still... 

Originally, the caseins were defined as those phosphoproteins which precipitate from raw skim milk upon acidification to pH 4.6 at 20°C, and the individual families were identified by alkaline urea gel electrophoresis (Whitney et al 1976). With the resolution of their primary structure, it became possible to classify them according to their chemical structure, rather than on the basis of an operational definition. When one does this, it is apparent that not all of the caseins contain phosphorus (Table 3.1) some are also found in the acid whey after removal of the precipitated caseins. 

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