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PubMed2006

The sensitivity of approved Ninhydrin and Biuret tests in the assessment of protein contamination on surgical steel as an aid to prevent iatrogenic prion transmission.

Regulations recommend the routine application of biochemical tests, such as the Ninhydrin or Biuret tests, to confirm the efficacy of hospital sterile service department (SSD) washer-disinfector cycles in removing proteinaceous material, particularly with respect to prions. The effectiveness of these methods relies on both the effective sampling of the instruments and the sensitivity of the tests employed. Two commercially available contamination assessment tests were evaluated for their sensitivity to ME7 brain homogenate on surgical-grade stainless steel surfaces. Controls were visualized by the application of episcopic differential interference contrast/Epi-fluorecence microscopy (EDIC/EF) combined with the sensitive fluorescent reagent, SYPRO Ruby, which has been shown previously to rapidly visualize and assess low levels of contamination on medical devices. The Ninhydrin test displayed a minimum level of detection observed by 75% of volunteers (MLD(75)) of 9.25 microg [95% confidence interval (95% CI) 8.6-10.0 microg]. The Biuret test provided better sensitivity, with a MLD(75) of 6.7 microg (95% CI 5.4-8.2 microg). However, much lower concentrations of proteinaceous soiling (pg) were visualized using the EDIC/EF microscopy method. From these findings, it is clear that these approved colorimetric tests of cleaning are relatively insensitive. This investigation demonstrates how large amounts (up to 6.5 microg) of proteinaceous brain contamination could remain undetected and the instruments deemed clean using such methods. The application of more sensitive cleanliness evaluation methods should be applied to reduce the risk of iatrogenic transmission of prion disease in 'high-risk' instruments such as neurosurgical devices.

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↗
PubMed2005

Interference of dextran in biuret-type assays of serum proteins.

Dextran interference in biuret-type assays of total serum proteins was investigated in a Belgian National External Quality Assurance Survey with 256 participants. In vitro supplementation of therapeutic (10% Gentran 70) dextran concentrations showed a broadly varying (from 0 to 20%) negative interference. The analytical interference was found to depend on both the sodium hydroxide and tartrate concentrations in the reagent formulation. The dry chemistry biuret method was not affected by the dextran interference. In a number of cases, the effects observed may be of clinical importance. Both clinicians and laboratory staff should be aware of the persistence of this analytical problem.

Biuret Reaction↗
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↗
PubMed1995

Quantitation of protein content by biuret method during production of Yellow Fever Vaccine.

Protein content of 60 batches of Yellow Fever Vaccine was measured by Biuret method and was compared to the values obtained by Kjeldahl method. Statistical analysis did not show any difference between the two methods. The Biuret method is specific, easy to carry out and takes little time for protein estimation during production of Yellow Fever Vaccine.

Chemistry Techniques, Analytical↗
PubMed1995

Quantitation of the protein content of diphtheria and tetanus toxoids by the Biuret method during production of combined vaccines.

The protein content of 15 batches of diphtheria toxoid and 12 batches of tetanus toxoid was measured by Biuret method and was compared to the values obtained by the Kjeldahl method. Statistical analysis did not show any difference between the two methods. The Biuret method, is specific, easy to carry out and takes less time for protein estimation of purified toxoids during production of combined vaccines.

Chemistry Techniques, Analytical↗
PubMed1999

Detection of peptides by precolumn derivatization with biuret reagent and preconcentration on capillary liquid chromatography columns with electrochemical detection.

The separation and detection of biuret complexes of neuropeptides by capillary liquid chromatography with electrochemical detection was explored. Capillaries of 25-micron inner diameter packed with base-resistant, polymer-based reversed-phase particles were used for separation, and C-fiber electrodes were used for detection. Detection at the C-fiber electrode was found to have some differences in relative sensitivity for peptides compared to glassy carbon electrodes used previously. On-column preconcentration of preformed complexes allowed up to 1-microL samples to be injected with minimal band broadening resulting in a 100-fold improvement in concentration detection limit with no effect on mass detection limit. Concentration detection limits ranged from 5 to 59 pM, depending upon the peptide, corresponding to 5-59 amol injected. The low concentration detection limit was possible because of minimal baseline disturbances, minimal formation of unwanted products, and high efficiency of complex formation associated with biuret derivatization. The method was applied to determination of vasopressin and bradykinin in dialysates collected with 5-min sampling frequency from the rat supraoptic nucleus.

Animals↗
PubMed1975

Improved biuret procedure for routine determination of urinary total proteins in clinical proteinuria.

This communication describes and evaluates an improved routine methodology for quantitating clinical proteinuria. Based on investigations of Piscator and of Savory et al., a modified Tsuchiya's reagent (ethanolic HCI-phosphotungstic acid) is used to precipitate proteins at 56 degrees C, followed by biuret spectrophotometry at 540 nm. The accuracy of the proposed procedure was assessed by comparisons with results obtained by using an ultrafiltration membrane that retains solutes with an average molecular weight in excess of 10 000 for separating of urinary proteins before they are measured with the biuret reaction. Precision of the method (coefficient of variation) is typically 2-3%.

Evaluation Studies as Topic↗
PubMed1980

[Method of determination of proteins with Coomassie brilliant blue G 250. I. General characteristics and comparative analysis with the biuret method and Lowry's method].

Bradford (1977) described a new sensitive easy rapid method for protein assay, depending on colour change of the stain Coomassie Brilliant Blue G 250. In this study Bradford's method was compared with the Lowry et al. 91951) and biuret methods. Coomassie method appears to be as sensitive as Lowry, as simple as biuret. Another advantage is a very short time of performing.

Methods↗
PubMed1983

A rapid biuret assay for protein of whole fatty tissues.

A rapid biuret procedure is described which avoids the turbidity that occurs with protein analysis of intact fatty tissues. Recovery is complete and absorbancy linear with both concentration of the soluble crystalline serum albumin standard and the volume of homogenate of a variety of tissues. This method has been used successfully for the determination of protein concentrations of homogenates of whole rat heart, liver, kidney, brain, lung, and the following muscles: gastrocnemius, interior and exterior obliques, red and white vastus lateralis, and soleus.

Adipose Tissue↗
PubMed1979

[Sensitive method for continuous detection of peptides and proteins using the biuret reaction and a copper-Sephadex reactor (author's transl)].

We describe a detection method relying both on the copper displacement from a Sephadex gel by peptides and proteins, and on the subsequent colorimetric determination of the complexed copper. The system described is fully automated and it permits a continuous analysis of column effluents. The choice of cuprizone as a detecting reagent for copper, enables one to bring the detection limit down to 200 ng for albumin and 60 ng for alanylglycylglycin. The specificity of the method is the same as the biuret reaction. Some examples of the possible applications are given.

Biuret Reaction↗
PubMedDate not supplied

Exposure, lung function, and symptoms in car painters exposed to hexamethylendiisocyanate and biuret modified hexamethylendiisocyanate.

Individuals who paint cars often complain to doctors about respiratory problems. Car painters are exposed to isocyanates, especially hexamethylendiisocyanate (HDI), and biuret modified HDI (HDI-BT). The mean exposure to HDI-BT was 115 micrograms/m3 in the air (range 10-385 micrograms/m3), which exceeds the time-weighted Swedish threshold level of 90 micrograms/m3. Exposure to HDI was about 1.0 microgram/m3 with brief peaks. This study investigated the effect of HDI and HDI-BT on lung function and included two control groups: (1) car platers, exposed to the same solvents and grinding dust as car painters, but not to isocyanates, and (2) car mechanics (controls), not exposed to the mentioned agents. Car painters and car platers were compared to car mechanics on Monday before work. Acute effects of car painting were tested by comparing the lung function values on Monday morning with those on Friday afternoon. Pulmonary function was evaluated by means of spirometry and a single breath nitrogen washout. Spirometry in painters and platers did not differ from that in controls, i.e., car mechanics. Closing volume in relation to vital capacity (CV%) was increased in car painters, suggestive of a "small airways disease" on Monday before work and tended to increase during a work week. Car platers did not differ from controls.

Adult↗