Quantitation of protein in cerebrospinal fluid, urine and other low-protein fluids requires more sensitive techniques than either the Biuret or refractometer method. Take 1 ml of test solutions in dry test tubes and in another tube take 1 ml distilled water as control. It detects all proteins and is accurate for the range of 1-10 g/dL. For example, the trimer of 1,6-hexamethylene diisocyanate is also known as HDI-biuret. Biuret Method This is the colorimetric method used on the automated chemistry analyzer. For more on estimation of total protein with refractometry, refer to the hemogram basics section of the website. The test and reagent do not actually contain biuret; they are so named because both biuret and proteins have the same response to the test. It is less favored than urea, due to its higher cost and lower digestibility but the latter characteristic also slows down its digestion and so decreases the risk of ammonia toxicity. also can affect refractive index, as can colloids such as hetastarch and gelatin (Yam et al 2018). 249.68), 5 gm Potassium iodide (166.0), all dissolved in orderin 400 ml 0.2 M NaOH (f.w. This lab activity is designed to teach students the principles behind a common protein estimation assay known as the Biuret Protein Assay. A variety of organic derivatives are known. 40.0) before bringing to final volume. Precipitation methods include trichloroacetic acid and sulfosalicylic acid, whereas dye-binding uses dyes such as Coomassie blue and pyrogallol red-molybdate. The parent compound can be prepared by heating urea above the melting point at which temperature ammonia is expelled:[3]. The procedure on the Hitachi 911 at Cornell University for measurement of protein in low-protein fluids is a turbidometric method based on precipitation of protein by benzethonium chloride. Albumin is a single protein that accounts for about half of the total protein concentration in plasma. The contribution of fibrinogen to total protein content in plasma compared to serum. This difference is attributed to: However, it should be noted that there are some reports where the total protein by biuret is higher (0.5-0.7 g/dL on average) than that by refractometry in ruminants, for unclear reasons (Katsoulos et al 2017). It measures the refractive index of a sample relative to the refractive index of water. It crystallizes from water as the hydrate. The stability of total protein in human serum and plasma samples are as follows: 3 days at 2-8 °C or 6 months at (-15) to (-25) °C. The conversion formula is shown below: Serum and plasma. [4], Biuret is also used as a non-protein nitrogen source in ruminant feed,[5] where it is converted into protein by gut microorganisms. There are also different refractometers available, which may not give equivalent results, depending on whether they use a correction formula or not. This is the colorimetric method used on the automated chemistry analyzer. Albumin generally accounts for about half of the total protein concentration in plasma. Note that urinary dipsticks can be used to estimate protein in cerebrospinal fluid samples, however they are not as accurate as turbidometric techniques. A Review", "Ueber ein neues Zersetzungsproduct des Harnstoffs", "Neues Zersetzungsproduct des Harnstoffs", "Ueber eine neue, aus dem Harnstoff entstehende Verbindung", https://en.wikipedia.org/w/index.php?title=Biuret&oldid=979652696, Articles with unsourced statements from June 2012, Articles with unsourced statements from May 2012, Articles with unsourced statements from January 2016, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License, This page was last edited on 21 September 2020, at 23:56.