Ampholytes compositions

Sample preparation for CIEF includes selection of the appropriate ampholyte composition, adjustment of sample salt levels, and dilution or concentration of the sample to the proper protein levels required for detection. 

As previously mentioned, resolution in CIEF strongly depends on the ampholyte composition. The estimated maximum resolving power of IEF is 0.02 pH units when carrier ampholytes are used to create the pH gradient.99 The Law of Monotony" formulated by Svensson in 1967 states that a natural pH gradient increases continually and monotonically from the anode to the cathode that the steady state does not allow for reversal of pH at any position along the gradient and that two ampholytes (in stationary electrolysis) cannot be completely separated from each other unless the system contains a third ampholyte of intermediate pH (or pi). The latter explains why better resolution is obtained when mixing ampholytes from different vendors and production batches as the number of ampholytes species increases, the chance that one or more ampholytes have intermediate pi relative to those of the sample components also increases. 

Amphoteric Detergents. These surfactants, also known as ampholytics, have both cationic and anionic charged groups ki thek composition. The cationic groups are usually amino or quaternary forms while the anionic sites consist of carboxylates, sulfates, or sulfonates. Amphoterics have compatibihty with anionics, nonionics, and cationics. The pH of the surfactant solution determines the charge exhibited by the amphoteric under alkaline conditions it behaves anionically while ki an acidic condition it has a cationic behavior. Most amphoterics are derivatives of imidazoline or betaine. Sodium lauroamphoacetate [68647-44-9] has been recommended for use ki non-eye stinging shampoos (12). Combkiations of amphoterics with cationics have provided the basis for conditioning shampoos (13). 

Compositions of three types of carrier ampholytes. Short segments of some representative carrier ampholytes are shown. The different types of molecules arise from different manufacturing processes. Most carrier ampholytes are mixtures of oligomers (about 300- 1000 Da in size) containing multiple aliphatic amino and carboxylate groups (A and B), although some types contain sulfonic and phosphoric acid residues (C). See Ref. I. 

Figure 5 Schematic representation of the segmented injection protocol for EOF-driven single-step capillary isoelectric focusing. The following solutions are injected into the capillary (1) 20 mM NaOH containing 0.01 5% methylcellulose, (2) ampholyte solution, (3) sample, (4) ampholyte solution. The catholyte at the negative pole is 20 mM NaOH, and the analyte is 10 mM H3P04. The length of the ampholyte-sample-ampholyte "sandwich-zone" is ca. 20-30% of the whole capillary length. The composition of the ampholyte solutions and the relative lengths of the zones can be varied easily in this protocol.

Experiments with ampholytes from different sources covering the same or similar pH ranges may not provide identical results, indicating differences in the distribution of the components and/or chemical composition [37,39]. A combination of narrow- and broad-range ampholytes provides high efficiency in separation of components with close pi values [37],... 

Heparin, then, consists of a series of highly sulfated compounds, identical in carbohydrate composition but separated by complexing with LKB ampholyte (with progressive adjustment of pH), into a large number of separate chains. These chains are flexible molecules, probably in a Gaussian coil, and are characterized by a shell of negative charges... 

Since rehydratable gels are polymerized in the presence of a defined buffer, any effects of composition, pH range, batch variation or storage-induced changes of the carrier ampholytes are eliminated. The problems Involved in achieving reproducible polymerization of... 

Fig. 2. Composition of Svensson-type (1961) carrier ampholytes, as synthesized by Vesterberg (1969). On the upper left side a representative chemical formula is shown (aliphatic oligo amino oligo carboxylic acids). On the lower left side, portions of hypothetical titration curves of Ampholines are depicted. Right different pH cuts for wide and narrow range carrier ampholytes. (Courtesy of LKB Produkter AB, Bromma. Reproduced with permission of the publisher.)...

Alternatively, hydrogels can be classified based on their composition, their preparation method, their ionic charge (neutral, anionic, cationic, ampholytic hydrogels), or their structure (amorphous, semicrystalline hydrogels). 

The trough is filled with about 45 ml solution of carrier ampholyte of the desired composition and concentration. The trough is inclined slightly from side to side. This distributes the solution evenly over the bottom of the trough. Each fold of the trough now contains liquid to a level below the tops of the ridges. 

Figure 4. Composition of carrier ampholytes for isoelectric focusing...

Amphoteric Detergents These surfactants, also known as ampholytics, have both cationic and anionic charged groups in their composition. The cationic groups are usually amino or quaternary forms, while the anionic sites consist of carboxylates, sulfates, or... 

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