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a urea derivative; its presence is detected after addition of sodium hydroxide and copper sulfate solutions by a pinkish-violet color (protein test) or a pink and finally a bluish color (urea test).
biuret reaction the reaction in biuret tests.
biuret test either of the tests done with biuret.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
the formation of biuret that gives a violet color as a result of the reaction of a polypeptide of more than three aminoacyl residues with CuSO4 in strongly alkaline solution; dipeptides and amino acids (except histidine, serine, and threonine) do not so react; used for the detection and quantification of polypeptides, or proteins, in biologic fluids.
Farlex Partner Medical Dictionary © Farlex 2012
bi·u·ret re·ac·tion, biuret test (bī'yŭr-et' rē-ak'shŭn, bī'yŭr-et' test)
The formation of biuret, which gives a violet color because of the reaction of a polypeptide of more than three amino acids with CuSO4 in strongly alkaline solution; used for the detection and quantitation of polypeptides or protein in biologic fluids.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
Biuret reactiona chemical change used as a quantitative method for protein determination. The reaction takes place when dilute copper sulphate solution is added to a protein solution which is then made alkaline by the addition of sodium hydroxide. A copper hydroxide precipatate forms and a purple/violet colour is produced, the strength of which indicates the quantity of protein present. The reaction only works if at least two PEPTIDE BONDS are present in the protein. Thus single AMINO ACIDS and DIPEPTIDES with only one peptide bond will not give a positive Biuret reaction.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005