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PubMed1978

An interlaboratory comparison of serum total protein analyses.

An analysis of the 1976 CAP Comprehensive Chemistry Survey of total serum proteins is presented. More than 2,000 laboratories contributed data in this survey. Estimation of total serum protein concentration by the biuret reaction remains the most widely used technic, followed by refractometry. Precision and accuracy data for a number of analytic systems and methods are presented. Precisions for the entire group are nearly comparable. A negative bias for total protein concentration was shown by the SMAC.

Blood Chemical Analysis↗
PubMed1993

[Antithrombotic and antiplatelet effects of rosmarinic acid, a water-soluble component isolated from radix Salviae miltiorrhizae (danshen)].

Wistar rats of both sex were used. Ros A was intravenously injected 5-10 min before blood collection or the ligation of vena cava. 1. Stasis-induced venous thrombosis: A tight ligature was applied to inferior vena cava below the left renal vein in anesthetized rats. The abdominal walls were closed and then reopened two hours later. The vena cava was clamped 2 cm below the ligature. This segment was cut to remove the thrombus. The dry weight of the thrombus was determined. 2. Platelet aggregation: Using Born's method the platelet aggregation induced by collagen or ADP was studied. 3. Blood coagulation times: Blood recalcium time (RT), kaolin partial thromboplastin time (KPTT) and prothrombin time (PT) were estimated. 4. Plasma fibrinolytic activity was observed by the determination of euglobulinolytic time (ELT). Plasma fibrinogen content was estimated based on the biuret reaction. The venous thrombosis was inhibited by 41.9% and 54.8% (P < 0.05) when Ros A was injected at the dosages of 50 and 100 mg/kg. The blood platelet aggregation elicited by collagen was suppressed by 30.4% (P < 0.05) and 46.4% (P < 0.01) after the injection of Ros A at doses of 100 and 150 mg/kg respectively. The ELT was shortened after the injection of Ros A (100 and 150 mg/kg) as compared with the control value (P < 0.05), while the plasma fibrinogen content remained unchanged. The results that Ros A showed mild antithrombotic effect. The mechanism of this effect might be related to its inhibition of platelet aggregation and promotion of fibrinolytic activity.

Animals↗
PubMed1977

Combined gel filtration, biuret/copper method compared with an immunochemical method for urinary protein measurement.

We compared an immunochemical method specific for plasma proteins with a chemical method, in which interfering substances are separated by gel filtration and "total" urinary protein is determined by the biuret reaction followed by reaction of protein-bound copper with diethyldithiocarbamate after a second gel filtration to remove nonprotein-bound copper. More than 250 24-h urine samples were analyzed by each method. There was linear agreement and a correlation of 0.96 between the two methods, but urinary protein values determined by the immunochemical method, especially for patients with multiple myeloma, were lower than by the chemical method.

Chromatography, Gel↗
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

Three automated quantitative assays for serum proteins.

Three quantitative assays for detection of proteins are reported. One is an adaptation to the Auto-Analyzer of the widely used method of Lowry et al. In another procedure, the product of the reaction of proteins with a modified biuret reacts with the phosphomolybdic--phosphotungstic reagent of Folin and Ciocalteu. The third method, performed on hydrolyzed sample, is based on the measurement of proline (Pro) and the conversion of the Pro content into protein. The universal presence of proline in serum proteins suggested this assay. The values for total serum proteins as assayed by the three procedures are similar. The second and the third assay for proteins, described in this paper, can also be performed manually. Studies on interfering substances and their elimination as well as on the sensitivity of the assays are reported.

Animals↗
PubMed1985

Molar absorptivity and the blank correction factor.

In photometry, where both the product formed and one or several reactants absorb light at the same wavelength, the absorbance of the "blank" of the sample at the end of the reaction may be less than that measured at the beginning of the reaction, because of consumption of reactant(s). The blank correction factor for the determined result with one light-absorbing reagent is epsilon P / (epsilon P - epsilon R), where epsilon R and epsilon P are the molar absorptivities of the reagent and the product, respectively. We derived a factor for the case when more than one reagent absorbs light at the same wavelength as the measured product. This factor is independent of the concentration of reagent(s) and can correct the determined result or absorbance for the consumption of light-absorbing reagent(s) during the reaction.

Biuret Reaction↗
PubMed1996

Electrochemical detection in bioanalysis.

This review article presents an overview of current research on the use of amperometric electrochemical detectors in bioanalytical chemistry. Topics covered include microdialysis and ultrafiltration membranes for in-vivo sampling; microbore liquid chromatography; capillary electrophoresis; enzyme, photochemical, and chemical post-column reactions; electrochemiluminescence; and thin-film electrode materials. Selected references are cited.

Animals↗
PubMed1983

Colorimetric determination of agarose-immobilized proteins by formation of copper-protein complexes.

A simple, reliable, and sensitive colorimetric procedure for the determination of proteins bound to agarose is described. The procedure utilizes the capacity of diethyldithiocarbamate to react with cupric ions resulting in a complex of dark yellow color. The extent of reduction in the color, due to chelation of Cu2+ by the immobilized proteins, indicates the amount of protein. The optimum conditions for the determination of immobilized proteins are investigated. The formation of Cu2+-protein complex proceeds stepwise until enough excess of Cu2+ is present to form the final complex. The reliability of the procedure requires that all the protein species, samples and standards, are in the final Cu2+-protein complex form. A comparative study on the determination of different proteins bound to agarose using this method as well as other methods, such as protein balance, modified Lowry reaction, and direct ultraviolet spectrophotometry, is described. The method is substantially more reliable, accurate, and simple than previously described methods.

Biuret Reaction↗
PubMed2002

Separation and detection of angiotensin peptides by Cu(II) complexation and capillary electrophoresis with UV and electrochemical detection.

The use of capillary electrophoresis (CE) with on-capillary Cu(II) complexation for the determination of angiotensin and its metabolites is described. The resulting copper-peptide complexes can be detected using either UV or electrochemical (EC) detection. Optimal reaction and separation conditions for the angiotensin peptides were first determined using CE with UV detection. With UV detection, the limit of detection (signal-to noise ratio S/N = 3) for native angiotensin II was 18 microM, while the limit of detection (LOD) obtained for the copper-angiotensin II complex is 2 microM. CE with EC detection was then evaluated, yielding significantly lower LODs--2 microM for native angiotensin II and 200 nM for the copper-angiotensin II complex. The addition of copper to the run buffer improved the separation and sensitivity for both CE-UV and CE-EC detection. The method was demonstrated by monitoring the conversion of angiotensin I to angiotensin II in plasma via angiotensin-converting enzyme (ACE) and subsequent inhibition of ACE by captopril.

Angiotensin I↗
PubMed2001

Application of an improved biuret method to the determination of total protein in urine and cerebrospinal fluid without concentration step by use of Hitachi 7170 auto-analyzer.

A biuret automated colorimetric assay for total protein in urine and cerebrospinal fluids was established. The procedures were as follows. Acidify all urine sample before analysis. Add precipitant Na(2)WO(4) to urine samples. After 10 min, centrifuge, decant the supernatant fluid, drain the inverted tubes on absorbent tissue, dissolve the precipitation with 0.1 mol/L NaOH, and finally adapt the reconstituted urine to the Hitachi 7170 analyzer. A cell-free cerebrospinal fluid sample produced by centrifugation can be inserted in an auto-analyzer for protein measurement directly. The program: mix 35 microl sample (CSF or reconstituted urine) and standard with 0.2 mol/L NaOH; incurable at 37 degrees C for 5 min, and real A1. Add concentrated biuret reagent, and 10 min later measure absorbance A2 at 546 nm vs. reagent blank. Secondary wavelength was 700 nm. The test results were calculated against a one-point standard. This biuret colorimetric method was relatively simple, fast, and accurate for the determination of protein in urine and cerebrospinal fluid, with a wide linearity extending from 0.125 g/L up to 6 g/L, had a good correlation with Benzethonium chloride turbidimetry technique, and was a practical routine method.

Albumins↗
PubMed1995

A comparison of methods for determining total body protein.

The aim of the study was to find the optimal method (with respect to convenience and accuracy) for determining total protein in whole-body homogenates of rats. Three different protein extraction methods and five different protein concentration methods were assessed. The results were compared against a reference value measured by complete amino acid analysis after acid hydrolysis. The data demonstrated that extraction with 5% (w/v) sodium dodecylsulfate (SDS) in 0.5 N NaOH was far superior to that with water alone or to 6 N guanidine-HCl. A comparison of the Biuret, Bradford, and bicinchoninic acid methods on the SDS-NaOH-extracted samples showed that the Biuret method was optimal, giving a value that was 90% of the reference value with a small variation (2.4% of the mean). The Kjeldahl method gave the correct protein concentration only when a nitrogen factor of 5.51 +/- 0.03 (N = 5) was applied. The results suggest that extraction with SDS-NaOH followed by the Biuret procedure is a good method for measuring protein concentrations in whole body rat homogenates.

Amino Acids↗
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↗
PubMed1978

Automated continuous flow determination of urine albumin by competition with dye-detergent binding.

A continuous flow automated method for urine albumin was developed based on the ability of albumin to displace bromophenol blue from a bromophenol blue detergent complex. The method is almost specific for albumin, giving a slight response with an alpha-globulin fraction from serum. Results agreed closely with rocket electrophoresis albumin estimates on urine samples, but significantly less closely with "total urine protein" estimates by an acid protein precipitation, followed by biuret colour reaction, procedure. This method is being used to replace the indefinite "total protein" test for most routine purposes.

Albuminuria↗
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↗