Acids chromatography

Keller and Cohen (36) also subjected to chromatography acidic extracts of cattle pancreatic microsomes and ribosomes. In microsomes they found the expected amounts of all enzymes which are known to be stable in acid, viz., chymotrypsinogen A, trypsinogen, deoxyribonuclease, and ribonuclease. The amounts of chymotrypsinogen B were abnormally low and ribonuclease B was perhaps not present. The results concerning ribosomes were made somewhat uncertain by the ability of these particles to incorporate proteins from the medium. Nevertheless, a series of characteristic enzymes could be isolated from what appears to be the very site of their biosynthesis. 

High-scale purification methods are required for several protein studies such as crystallography, mass specttometty, circular dichroism, and function. Here we describe a purification method for PAP based on anion exchange, L-(+)-tartrate affinity, and gel filtration chromatographies. Acid phosphatase activity and protein concentration were measured for each purification step, and to collect the firactions with the highest acid phosphatase activity the p-nittophenyl phosphate method was used. The purified protein obtained by the procediue described here was used for the determination of the first reported three-dimensional structure of prostatic add phosphatase. 

For use as the stationary phases in chromatography, acidic, neutral and basic forms of alumina are commercially available. 

Windahl, K. W., Trenerry, V. C., and Ward, C. M., The determination of niacin in selected foods by capillary electrophoresis and high performance liquid chromatography Acid extraction. Food Chem., 65, 263, 1998. 

SPE,TLC, HSCCC, MSPD Column chromatography Acidity based-fractionation Liquid-liquid fractionation (organic solvents)... 

In the separation of organic molecules, gas-liquid chromatography (GLQ has become more important than gas-solid (adsorption) chromatography. Acid-washed kieselguhr, powdered fire-brick and polystyrene containing polymers (Porapaks) are the most widely used carriers. Silicone or paraffin material is used for non-polar impregnation polyglycols and polyesters usually serve as polar stationary liquids. 

Several techniques were used in order to characterize the neutral radiolabelled xylolipids. According to silicic acid and anion exchange column chromatography, acid and alkali treatments and comparative thin layer chromatography in neutral, basic and acidic solvents (Table 1 and [7]) the major neutral xylolipid was found to behave as a sterol derivative, whereas one of the minor neutral xylolipids behaved as an acylated steryl derivative. The main anionic xylolipid x behaved as a dolichyl-phosphate derivative (Table 1 )[9]. 

Sephadex A trade name for an insoluble hydrophilic substance prepared by cross-linking dextran, and used in gel filtration. It can also be linked to acidic or basic groups for ion exchange or to alkanes for the chromatography of lipophilic compounds. 

The first of the two experiments given below illustrates the separation of amino-acids, now an almost classic example of the use of paper chromatography the second illustrates the separation of anthranilic acid and iV-methylanthranilic acid. Both experiments show the micro scale of the separation, and also the fact that a mixture of compounds which are chemically closely similar can be readily separated, and also can be identified by the use of controls. 

This recrystallised acid is pure in the norm y accepted sense of the word, namely it has a sharp m.p. and gives on analysis excellent values for carbon, hydrogen and nitrogen. If however it is subjected to one-dimensional paper chromatography (p. 53), the presence of traces of unchanged anthranilic acid can be detected, and repeated recrystallisation is necessary to remove these traces. 

More information has appeared concerning the nature of the side reactions, such as acetoxylation, which occur when certain methylated aromatic hydrocarbons are treated with mixtures prepared from nitric acid and acetic anhydride. Blackstock, Fischer, Richards, Vaughan and Wright have provided excellent evidence in support of a suggested ( 5.3.5) addition-elimination route towards 3,4-dimethylphenyl acetate in the reaction of o-xylene. Two intermediates were isolated, both of which gave rise to 3,4-dimethylphenyl acetate in aqueous acidic media and when subjected to vapour phase chromatography. One was positively identified, by ultraviolet, infra-red, n.m.r., and mass spectrometric studies, as the compound (l). The other was less stable and less well identified, but could be (ll). 

The nitration of the 2-anilino-4-phenylselenazole (103) is much more complicated. Even careful nitration using the nitrate-sulfuric acid method leads to the formation of a mixture of variously nitrated compounds in an almost violent reaction. By the use of column chromatography as well as thin-layer chromatography a separation could be made, and the compounds could be partly identified by an independent synthesis. Scheme 33 shows a general view of the substances prepared. Ring fission was not obser ed under mild conditions. 

Nonvolatile analytes must be chemically converted to a volatile derivative before analysis. For example, amino acids are not sufficiently volatile to analyze directly by gas chromatography. Reacting an amino acid with 1-butanol and acetyl chloride produces an esterfied amino acid. Subsequent treatment with trifluoroacetic acid gives the amino acid s volatile N-trifluoroacetyl- -butyl ester derivative. 

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