Biuret Separation

When the residue is heated with water, qyanuric acid remains behind, and biuret separates out on cooling the solution. Xhis may be putifi by dissolving in hot water and reprecipitating with dilate ammonia.- Binret forms long white needle-shaped crystals, 100 parts requiting for their solution... 

For the assay of ephedrine in the total alkaloids a colorimetric method based on the biuret reaction was used by Feng and Read and is described in detail by Feng. Krishna and Chose separated ephedrine and iji-ephedrine by treating the dry mixed hydrochlorides with dry chloroform in which the ephedrine salt is virtually insoluble and the -ephedrine salt soluble. ... 

The latter group (M13, M14) separated two types of KIK factor from cancerous gastric juice. The first was a mucopolysaccharide and the second a mucoprotein. Others thought it to be a mucopolypeptide. A similar factor from cancerous ascitic fluid (19) contained 50-60% hexoses, 1.5% tyrosine, and 10% protein by biuret reaction. It formed a single peak at pH range 1.5-10.0 on paper electrophoresis, and at pH 8.6 moved with the mobility of serum y-globulin. 

Use Fertilizer, animal feed, plastics, chemical intermediate, stabilizer in explosives, medicine (diuretic), adhesives, separation of hydrocarbons (as urea adducts), pharmaceuticals, cosmetics, dentifrices, sulfamic acid production, flameproofing agents, viscosity modifier for starch or casein-based paper coatings, preparation of biuret. 

In the above methods, the separated albumin (or whole serum if total protein is to be determined) is reacted with excess copper in approximately 1 N alkali. A macromethod is also available which utilizes the capacity of albumin to react with copper(II) in a mole ratio of 1 1 (K32). This is an amperometric titration of blood serum (1 ml) in 0.1 M ammoniacal am-moniiun nitrate pH 9.2 with CuS04 (4.8 X 10 M). Under these conditions human y-globulin did not react, so that the fair agreement by this method with results obtained by a biuret method after sulfite fractionation (K32) is probably the result of a balance of errors. In view of the interest in the small fraction of albumin-boimd copper in hepatolenticular degeneration, and the paucity of information on the unique binding reaction presumably with N-terminal aspartyl residues, further investigation would be valuable. 

Albumin and globulins can be analyzed by the same procedure as for total proteins after fractionation by salting out with either sodium sulfate or sodium sulfite. More detailed information may be required about the protein fractions (a, j8, 7 globulins), in which case starch gel electrophoresis can be used to separate the proteins. Micro-Kjeldahl analysis of proteins is used when highly accurate data are required the biuret method is accurate to about 4%. 

Precipitation of neutralized gastric juice with tungstic acid and biuret reaction Precipitation of neutralized gastric juice with tungstic acid and biuret reaction separation of protein fractions... 

Weber et al. [111,147,149-156] have extensively studied the biuret reaction as a means of detecting peptides separated by HPLC. They identified a number of operating parameters that influence sensitivity, including post-column temperature, reaction time, buffer composition, Cu(II) concentration, peptide... 

Applications CE. In addition to its prevalent use in detection following HPLC separation, the biuret detection strategy has also been used for electrochemical detection of peptides following CE separation. A Cu(lI)-coated capillary has been used to eliminate the need for pre-colunm or on-column derivatization using a Cu(II)-containing buffer [161], Detection limits on the order of 0.7 jM were obtained for nonelectroactive peptides (di-, tri-, tetra-, and pen-taglycines). Other peptides including Pro-Leu-Gly-amide were also successfully detected with a 2 oM detection limit. 

Lunte and coworkers [162] recently showed the utility of on-column com-plexation using a Cu(II)-containing buffer for monitoring Leu-enkephalin metabolism in plasma. Using CE separation, biuret complexation, and electrochemical detection, a complete separation of Leu-enkephalin and its five metabolites was achieved. Applicability of this technique to plasma samples allowed two major... 

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