PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Biuret”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1984

Direct analysis for urinary protein with biuret reagent, with use of urine ultrafiltrate blanking: comparison with a manual biuret method involving trichloroacetic acid precipitation.

We describe a method for measuring urinary protein with a centrifugal analyzer. Biuret reagent is used, and blanking with an ultrafiltrate of urine eliminates interferences from the nonprotein, biuret-positive chromogens in urine. We compare results by this new method with those by a manual method in which trichloroacetic acid precipitation and biuret reagent are used. The new method shows good precision and excellent correlation (r = 0.997) with the manual method. The ease and convenience of this assay should make this a useful method for the routine clinical laboratory.

Anti-Bacterial Agents↗
PubMed1991

[The determination of protein content of milk, cheese, and meat with the use of the biuret reaction].

A review is given of the different composition of biuret test solutions and experiments with the estimation of protein content of milk, cheese and meat by means of the biuret method are reported. The pure protein and the casein content of skimmed milk and the protein content of whole milk could be determined with biuret test solutions containing potassium hydroxide and a detergent. The use of the biuret method is advantageous in the case of cheese and meat, which are dissolved in potash lye or alkaline detergent solutions. Disturbances of the biuret method caused by lactose, fat or turbidity were eliminated after addition of hydrogen peroxide, by means of extraction or of additional measurements with a copper-free, zinc-containing biuret reagent. Deviations of the color intensity of biuret complexes were compensated by inclusion of standards in the measurement series.

Animals↗
PubMedDate not supplied

The measurement of total serum proteins by the Biuret method.

The biuret reaction for proteins provides a simple and precise method for measuring serum proteins; Beer's law is obeyed to at least 10 g per dl. Several stable biuret reagents are available. Hemoglobin is the only important cause of interference which cannot be minimized by use of a sample blank. The mechanism of the biuret reaction is described and attention is drawn to the heterogeneity of the serum proteins and to the use of a certified albumin standard.

Biuret Reaction↗
PubMed1978

[Refractometric measurement of total serum protein, comparison of refractometry and biuret test (author's transl)].

Study on the Refractometric Determination of Total Protein in Serum, Comparison of the Refractometric and Biuret Method. Total protein concentration in serum was determined by the aid of the Abbé-refractometer and the biuret method. Both methods showed a good precision and accuracy. The investigation was carried out in 241 sera with normal bilirubin (up to 1 mg/100 ml), cholesterol (up to 200 mg/100 ml) and urea (up to 23,0 mg/100 ml) concentration, in 43 sera with increased (10,6-26,6 mg/100 ml) bilirubin concentration, in 129 sera with increased (200-520 mg/100 ml) cholesterol concentration and in 43 sera with increased (23,0-155,3 mg/100 ml) urea concentration. The comparison of the refractometric values with the values obtained by the biuret method in the 241 sera with normal bilirubin, cholesterol and urea concentration (correlation coefficient = 0,971) showed a close correlation and in the 43 sera with increased bilirubin concentration (correlation coefficient = 0,958) an acceptable correlation. However no close correlations were observed in the 129 sera with increased cholesterol concentration and in the 43 sera with increased urea concentration. The correlation lines diverged proportional with the increase of cholesterol and urea concentration from the expected correlation lines.

Bilirubin↗
PubMed1993

Determination of proteins by a reverse biuret method combined with the copper-bathocuproine chelate reaction.

A method of protein determination has been developed which combines the biuret reaction and the copper(I)-bathocuproine chelate reaction. Protein in the specimen forms a Cu(2+)-protein chelate complex (biuret reaction) during the first step. Excess Cu2+ is reduced to Cu+ by ascrobic acid, allowing the Cu+ to form a Cu(+)-bathocuproine chelate complex during the second step. The amount of Cu(+)-bathocuproine chelate complex formed is inversely proportional to the protein concentration. The sensitivity (epsilon = 1.4 x 10(6) 1.mol-1.cm-1 against human albumin) of this method was higher than that of the original Lowry (9.8 x 10(5)), pyrogallol red (1.0 x 10(6)) and commercially available Coomassie Brilliant Blue G.250 methods (6.7 x 10(5)). The color intensities of human gamma-globulin, human globulin (fractions IV-1 and IV-4), bovine albumin, egg albumin and horse gamma-globulin against human albumin (100%) ranged from 92 to 101%. The results obtained with the present method (y) correlated well with those determined by the biuret method (r = 0.998, y = 0.98 chi - 0.002, x = 1.31, y = 1.29 g/l) in 30 diluted sera. These results confirm that this assay is similar in sensitivity to the original Lowry method, is rapid and has similar reactivity to each of the various proteins in biological fluids.

Ascorbic Acid↗
PubMed1980

[Determination of proteins with the Coomassie brilliant blue G 250 method. IV. Use with cerebrospinal fluid proteins and comparative analysis with the biuret and Lowry methods].

The method of Bradford with Coomassie Brillant Blue G 250 for protein assay has been applyed to CSF in comparison with biuret and Lowry's methods. The results of Coomassie method closely agree with Lowry, and are similar to those of biuret. It is suggested to replace the previously used methods for CSF protein assay by the Bradford's method, because it keeps the sensitivity of Lowry and the simplicity of biuret. It adds too the advantage of requiring less time.

Cerebrospinal Fluid Proteins↗
PubMed1980

Automated multiple flow-injection analysis in clinical chemistry: determination of total protein with Biuret reagent.

We have examined the feasibility of the automated multiple flow-injection technique for application to clinical chemistry by adapting to this system the biuret method for the determination of total protein. Samples were discretely and rapidly introduced into a continuously flowing, nonsegmented reagent stream by means of an automatic sampler and high-pressure injection valve. Pumps operating at 1380-2070 kPa (200-300 psi) were utilized to introduce the biuret reagent and saline diluent into the system separately at flow rates of 72 and 47 microL/s, respectively. Use of 20-microL sample and a 3.0-s reaction-delay coil was adequately sensitive for analysis for total protein by this method. Samples were analyzed at a rate of 150/h with no detectable between-sample carryover. Within-run precision studies yielded relative standard deviations of 2.5% and less. Total protein values obtained by this method correlated well with those obtained by centrifugal analyzer and bubble-segmented continuous-flow biuret methods.

Autoanalysis↗
PubMed1984

Postcolumn detection of serum proteins with the biuret and Lowry reactions.

The Lowry and biuret reactions have been adapted for the selective detection of chromatographically resolved proteins, specifically proteins separated by high-performance liquid chromatography. The protein reagents are continuously added to the column effluent and produce the characteristic chromophores with both proteins and peptides. The reaction chemistries are compatible with ion-exchange, steric exclusion, and reverse-phase chromatography. Detection limits for proteins resolved by ion-exchange are about 5 to 10 micrograms with the Lowry reaction. Peptides containing tyrosine can be detected at the 100-ng level when chromatographed on reverse-phase columns. The biuret reaction is about 8 times less sensitive for proteins and not very effective for peptides. Reaction detection can be combined with direct absorbance detection in the uv to distinguish proteinaceous peaks from other peaks containing uv-absorbing compounds.

Biuret Reaction↗
PubMed1991

Electrochemical detection of oligopeptides through the precolumn formation of biuret complexes.

The relatively slow kinetics of formation of the electroactive Cu(II)-peptide complexes from larger (greater than 6 amino acids) peptides requires relatively high temperature and long reaction times for a postcolumn reactor. The precolumn incubation of bradykinin, Tyr8-bradykinin and insulin A chain with biuret reagent for 20 min at 60 degrees C leads to the formation of biuret complexes which can be subjected to chromatography in acidic or basic eluents. These complexes are detected electrochemically with a sensitivity similar to the Cu(II)-(ala)3 complex (1 nC/pmol at 1.0 ml/min). The influence of the column-packing material on the electrochemical detector response of the Cu-peptide complexes has also been studied.

Biuret↗
PubMed1991

[Determination of urinary protein using the biuret method].

Interlaboratory inspection of the quality of laboratory investigations in the Saratov region, carried out in 1987-1988, has revealed a 9 to 50 percent share of unsatisfactory results of measurements of urinary protein by the Roberts-Stolnikov method. This fault was not mended despite the measures taken and the errors detected in the activities of clinical diagnostic laboratories. Analysis of the relevant literature has led the authors to a conclusion that the biuret method, the most specific and sensitive of all the universal methods, should be given preference to. The final stage of the investigation is carried out with the use of a KFK-2M photoelectrocolorimeter. A standard curve based on albumin calibration solution was plotted to estimate the results. At present 15 clinical diagnostic laboratories of this region are using the biuret method. Their results have improved, as evidenced by interlaboratory quality control: the share of satisfactory results of urinary protein measurements makes up 83 to 100 percent.

Biuret Reaction↗
PubMedDate not supplied

Determination of chicken and turkey plasma and serum protein concentrations by refractometry and the biuret method.

Plasma and serum protein concentrations were determined in chickens and turkeys by refractometry (with human and veterinary refractometers) and by the biuret method. Chicken and turkey serum protein values were significantly lower than respective plasma protein values according to both methods. Refractometer readings for both plasma and serum correlated closely with the results of the biuret test (r2 = 0.72 to 0.97). These findings indicate that plasma and serum protein values may be determined accurately in chickens and turkeys with a handheld refractometer.

Analysis of Variance↗
PubMed1984

Prevention of interference by dextran with biuret-type assay of serum proteins.

In assay of serum proteins by use of the biuret reaction, dextran can cause turbidity by formation of an insoluble complex of dextran with copper and tartrate (or EDTA) in strongly alkaline solution. Whether or not the turbidity occurs depends on the tartrate concentration: turbidity is maximal at about 10 g/L, absent at 20 g/L or more, and only slight and delayed at 4 g/L. Two biuret reagents, containing respectively 5.6 and 22.5 g of tartrate per liter, obviate the interference, but the former is suitable only when a short (5 min) incubation is used. Both reagents show linear calibration curves and yield virtually identical results.

Biuret Reaction↗
PubMed1983

An improved modification of the biuret method for the determination of protein in turbid materials with high lipid and hemoglobin content.

The quantitative determination of protein by means of the biuret method frequently yields erroneous values, especially when applied to turbid, lipid- and hemoglobin-containing materials. These errors can only partially be abolished either by the addition of detergents or by destroying the Cu-protein complex by KCN addition. It was found that most disturbances were almost completely eliminated after prior precipitation of protein by the addition of Triton X-100 to the solubilizing biuret reagent and absorbance measurements being performed at a wavelength of 572 nm before and after the addition of KCN. Values of protein determinations according to the proposed assay and protein concentrations calculated from Kjeldahl nitrogen determinations have been shown to agree fairly satisfactory. The proposed assay represents a relatively simple and versatile approach for the evaluation of protein concentrations in a variety of materials containing lipids, hemoglobin and of some other turbidities as well.

Adipose Tissue↗
PubMed1983

Assay of cerebrospinal fluid protein: a rate biuret method evaluated.

We evaluated a rate colorimetric method (Beckman) for measuring total protein in cerebrospinal fluid. The automated instrument we used was Beckman's ASTRA TM. A 100-microL sample of spinal fluid is introduced into the biuret reagent in the reaction cell and the increase in absorbance at 545 nm is monitored for 20.5 s. Solid-state circuits determine the rate of alkaline biuret-protein chelate formation, which is directly proportional to the total protein concentration in the sample. The linear range of measurement is 120 to 7500 mg/L. Day-to-day precision (CV) over the range of 150 to 1200 mg/L ranged from 15.2 to 2.3%. The method was unaffected by radical alteration of the albumin/globulin ratio, but there is a positive interference in the presence of hemoglobin, a suppression in the presence of bilirubin, and no effect by xanthochromia. The method is precise, accurate, rapid, and convenient. The method was compared with the trichloroacetic acid method as performed on the Du Pont aca III, giving a correlation coefficient (r2) of 0.9693. The method is precise, accurate, rapid, and convenient.

Albumins↗
PubMed1977

The estimation of fibrinogen levels in animal plasmas by a simple refractometric method. A comparison with a biuret method.

A comparison was made between a biuret (reference) method and a simple refractometric (test) method for measuring fibrinogen levels in 84 animal plasmas. Although the correlation between the two methods was high (4=0.90 P less than 0-001) there was considerable random variation in the refractometric results in relation to the biuret results. This was thought to be due in part to the fact that refractometric results could only be expressed in multiples of 2.4 g/litre. In spite of this limitation, the refractometric method, on the grounds of speen and simplicity, is considered to have worthwhile application for fibrinogen determinations in practice laboratory.

Animals↗