Differential precipitation

Many other methods for separating isotopes have been described. A partial list includes membrane and membrane pervaporation, thermal diffusion of liquids, mass diffusion, electrolysis and electro-migration, differential precipitation, solvent extraction, biological microbial enrichment, and more. Although not discussed in... 

ProteTns are often purified by differential precipitation with neutral salts. Ammonium sulfate is the most common salt used for this purpose, although occasionally NaCl is used. The concentration of ammonium sulfate used to salt out proteins is almost always expressed in terms of percent saturation."... 

Wheat germ agglutinin (WGA), a lectin, has been used to measure BAP by affinity chromatography, affinity electrophoresis, or differential precipitation of isoforms. 

Mitoma and keeper (605) resolved the system into two components, separated from rat liver homogenate supernatant by differential precipitation with ammonium sulfate. Their combined system of enzyme I, enzyme II, DPN (or reduced DPN), and an aldehyde or alcohol, specifically hy-droxylated L-phenylalanine but not other aromatic compounds. Enzyme I is labile and only a tenfold purification could be achieved. Enzyme II is relatively stable. Many, but not all, aldehydes and alcohols tested could participate in the reaction. 

Other water miscible solvents (ethanol, methanol, and acetone), and other salts can also be used to differentially precipitate out proteins. Caprylic acid can precipitate proteins as effectively as... 

The solid residues from the filter and from various other plant sources contain some cadmium as well as iron, nickel, and cobalt. Since they may not be discarded as waste, they are processed further by a sequence of selective dissolution steps, electrolysis, and differential precipitation to recover metallic cadmium and separate solutions of cadmium sulfate, nickel sulfate, and cobalt sulfate that are sold to metal refiners for recycling. Depending on their compositions, the rinse and neutralizing liquors may be discarded as waste or reprocessed to recover their metal values and to reduce the plant emissions to acceptable levels. 

When mixtures of alkoxides are hydrolyzed, the different hydrolysis and polycondensation rates of each individual alkoxide can cause complications. These complications may lead to local inhomogeneities. If one species is hydrolyzed faster than the other, which is almost always the case, then differential precipitation occurs during hydrolysis, leaving the other species substantially unreacted. Examples of these are found in the following sections of this chapter. 

Consequence metal separation by their redox properties (Table 2.64) by way of differentiated precipitation. 

Barrett and Northcote (1965) extracted apple fruit pectin under mild conditions and separated the neutral arabinogalactan fraction from the pectinic acid by differential precipitation. The purity of the fractions was monitored by zone electrophoresis. It was found that the purified pectinic acid contained galactose, arabinose, rhamnose, xylose, fucose, 2- C methyl xylose... 

Efficient extraction of high quality RNA from a variety of plant tissues is an important first step in many procedures, such as analysis of gene expression, cDNA library construction, and in vitro translation. This procedure, which is essentially as described in Draper et al. (1), involves grinding and phenol extraction of plant material followed by differential precipitation of RNA with sodium acetate. The protocol has been successful with leaf material and cultured cells from a large number of species, however, slight adjustments may be necessary to optimize extraction from other tissues. 

Many laboratories have succeeded in fractionating histones by selective extraction and differential precipitation. The selective extraction procedure is based on the difference in the amino acid composition of the various types of histones. For example, a histone-rich lysine can be obtained by extraction from whole thymus with 5% perchloric acid followed by precipitation with 10% trichloroacetic acid. If the histones found in the perchloric acid extract are passed through a carboxymethyl-cellulose column and eluted from the column with borate buffer at pH 9, then different components called 1, 2, and 3 can be recovered. 

In human plasma and in many horse plasmas tested, no differential precipitation of euglobulin and pseudoglobulin could be detected (37). 

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