Biuret method

The same is true for specimens of serum from the newborn. Those who attempt to apply the biuret method to newborn sera, end up with values in the normal infant, resembling those for... 

Kingsley, G. R. Direct biuret method for determination of seriim proteins as applied to photoelectric and visual colorimetry. J. Lab. Clin. Med. (1942), 27,... 

Some drugs act as Indicators (e.g. phenolphthaleln, vegetable laxatives) and affect tests carried out at a particular pH. The presence of sulfobromophthaleln dye (BSP) In serum will Interfere with serum protein determined by the biuret method. 

Absorbance at 280 nm (A280 UV method) Absorbance at 205 nm (far-UV method) Biuret method... 

The method is more sensitive than the biuret method and has an analytical range from 10 ju,g to 1.0 mg of protein. Using the method outlined below this is equivalent to sample concentrations of between 20 mg l-1 and 2.0 g l-1. The relationship between absorbance and protein concentration deviates from a straight line and a calibration curve is necessary. The method is also subject to interference from simple ions, such as potassium and magnesium, as well as by various organic compounds, such as Tris buffer and EDTA (ethylenediamine-tetraacetic acid). Phenolic compounds present in the sample will also react and this may be of particular significance in the analysis of plant extracts. 

Protein Determination. Protein was determined by the biuret method (10) and expressed as % of dry weight. The standard was bovine serum albumin (BDH). 

There are numerous substances that are administered intravenously and have a direct effect on biochemical analysis. Obviously, glucose or electrolyte concentrations will be spuriously elevated if the specimen is taken from the same vein into which these substances are being administered. The presence of sulfobromophthalein dye (BSP) in serum or plasma will interfere with protein determined by the biuret method. The... 

Less sensitive but very simple and precise is measurement of the light absorption around 280 nm. This is discussed in the main text in Section D,6. For a typical protein an absorbance of 1.0 at 280 nm corresponds to a protein concentration of 1 mg / ml.h The very old biuret method is also useful for samples containing 1-10 mg / ml of protein. The violet color that arises upon addition of copper sulfate to an alkaline solution of a peptide or protein is recorded at 540-560 nm.h The color is especially intense for longer polypeptides. The name of the method arises from the fact that biuret gives a similar color1 (see also Eq. 6-85). 

Students will isolate intact mitochondria from beef heart and fractionate them to prepare submitochondrial particles. Each fraction will be characterized by protein estimation by the biuret method and measurement of malate dehydrogenase and monoamine oxidase activity. 

This unit describes four of the most commonly used total protein assay methods. Three of the four are copper-based assays to quantitate total protein the Lowry method (see Basic Protocol 1 and Alternate Protocols 1 and 2), the bicinchoninic acid assay (BCA see Basic Protocol 2 and Alternate Protocols 3 and 4), and the biuret method (see Basic Protocol 3 and Alternate Protocol 5). The fourth is the Coomassie dye binding or Bradford assay (see Basic Protocol 4 and Alternate Protocols 6 and 7), which is included as a simple and sensitive assay, although it sometimes gives a variable response depending on how well or how poorly the protein binds the dye in acidic pH. A protein assay method should be chosen based on the sensitivity and accuracy of method as well as the condition of the sample to be analyzed. 

Fine, J. 1935. Biuret method of estimating albumin and globulin in serum and urine. Biochem. J. 29 799. 

Table 1 Six methods for the determination of total protein concentration in human urine were compared the Lowry method, biuret method, methods using the dyes Commassie Brilliant Blue (G250), Ponceau-S, pyrogallol red and the turbidity method by Exton...

Mycelium was washed twice with 0.9% (w / v) NaCl followed by three extraction steps. In each extraction step the mycelium was boiled for 10 min with 1M NaOH and the supernatant was collected after centrifugation (16). The amount of protein in the pooled supernatant was measured based on the biuret method (17). 

The Biuret method depends on the reaction of compounds containing several peptide bonds with Cu2+ under alkaline conditions to form a violet-coloured species. 

Berg et al. (B5a) correlated the results of gastric biopsies with chemical and electrophoretic analysis of gastric juice. They determined total proteins by the biuret method and total hexoses colorimetrically by the orcinol technique, and performed horizontal paper electrophoresis followed by amido black and PAS staining. Their work corroborated previous findings (G19) that carbohydrate materials staining with PAS were localized in the center of the electrophoretic partition of gastric juice with some extension to adjacent areas. They also observed that... 

Several s pec tropho tome trie methods are available for the determination of protein in solution. The biuret method is based on the reaction of Cu with peptides in alkaline solution to yield a purple complex that has an absorption... 

The protein concentrations were determined either by the biuret method, using serum albumin as standard (Gornall et al., 1949), or with the Folin reaction (Lowry et al., 1951). 

A detailed procedure of a biuret method is available in a previous edition of this textbook. 

Calibration of Total Protein Methods Bovine or human albumin is commonly used to calibrate biuret methods. Albumin has been prepared consistently in high purity, it contains only amino acids, its nitrogen content is a constant fraction of its molecular mass, and the number... 

The determination of total serum protein is an important clinical measurement used in diagnosing liver malfunctions. Although the Kjeldahl method is capable of high precision and accuracy, it is too slow and cumbersome to be used routinely in determining total serum protein. The Kjeldahl procedure, however, has historically been the reference method against which other methods are compared. Methods commonly used include the Biuret method and the Lowry... 

---