Biuret reagent: Difference between revisions
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#REDIRECT [[Biuret test#Biuret reagent]] |
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The '''Biuret reagent''' is made of [[potassium hydroxide]] (KOH) and [[copper (II) sulfate]] (CuSO<sub>4</sub>), together with [[potassium sodium tartrate]] (KNaC4H4O6·4H2O). The blue reagent turns violet in the presence of [[proteins]], and changes to pink when combined with short-chain [[polypeptides]]. The potassium hydroxide does not participate in the reaction at all, but is merely there to provide an [[alkaline]] medium so that the reaction can take place. |
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The reagent is commonly used in a biuret [[protein]] [[assay]], a [[colorimetric]] assay used to determine protein [[concentration]]--such as [[UV/VIS spectroscopy|UV-VIS]] at wavelength 560nm (to detect the Cu<sup>2+</sup> ion). |
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==The Biuret Test== |
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:''Main Article: [[Biuret test]]'' |
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The principle underlying the test can be demonstrated with the chemical compound [[biuret]] which, just as proteins, is able to [[Complex (chemistry)|complex]] [[copper]] (II) [[ion]]s. The biuret assay does not in fact use [[biuret]], but is so named as it detects the [[peptide bond]] between the urea molecules or between amino acids. |
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Not all biuret tests actually require the Biuret reagent. Rather, the term "biuret test" is a generic term for the testing of proteins by using copper (II) sulfate solution in an alkaline environment. Thus, the process of testing for proteins in a solution by first adding a small amount of [[sodium hydroxide]], and then adding copper (II) sulfate drop by drop, is also known as a biuret test. |
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==References== |
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*[http://faculty.mansfield.edu/bganong/biochemistry/reagents.htm Chemical Reagents] |
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{{Template:Protein methods}} |
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[[Category:Protein methods]] |
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[[Category:Analytical chemistry]] |
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[[Category:Chemical tests]] |
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[[de:Biuretreaktion]] |
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Latest revision as of 22:03, 21 February 2011
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