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PubMed1977

Assessment of five quantitative methods for determination of total proteins in urine.

1. We assessed five quantitative methods for the determination of urinary total proteins, three of them with precipitation followed by spectrophotomollowed by spectrophotometry (Tsuchyga/Benedict, Tsuchyga/Biuret and TCA/Biuret); one with gel-filtration (Sephadex G50/Biuret) and a Turbidimetric procedure (SSA). 2. Day-to-day precision was between 3.58 %CV (Tsuchyga/Benedict) and 11.46 %CV (Sephadex/Biuret). The Tsuchyga/Benedict method showed the closest values to controls quantitated by the Kjeldahl method and the lowest detection limit )17.3 mg of total proteins per liter). Recovery studies showed that a level of 100-200 mg/l the Tsuchyga/Benedict recovered over the 96% of the protein added. 3. Comparison studies of 66 24-hour urine samples showed that the best correlation was obtained between the Tsuchyga/Benedict and the Tsuchyga/Biuret methods (r = 0.996). 4. We conclude that the Tsuchyga/Benedict is a sensitive, precise and accurate procedure for the routine quantitation of urinary total proteins.

Biuret Reaction↗
PubMed1997

Serum protein determination by high-performance gel-permeation chromatography.

A general high-performance gel-permeation chromatography (HPGPC) method was developed to determine protein in human serum with improved sensitivity and speed. The optimum UV wavelength for protein detection was found to be 210 nm, by comparing the protein values obtained by varying the UV wavelength of the HPLC detection system with the protein values obtained from spectrophotometric protein assays, i.e., the bicinchoninic acid (BCA) method and the biuret method. The analysis time was less than 1 min. Since this HPGPC serum protein assay method is simple and rapid, it is expected to be particularly well adapted for use in clinical laboratories.

Adolescent↗
PubMed2002

Fabrication of microchannel structures in fluorinated ethylene propylene.

A new technique for fabrication of channel structures with diameters down to 13 microm in fluorinated ethylene propylene (also known as poly(tetrafluoroethylene-co-hexafluoropropylene), FEP) is described. The technique is based on the unique property of a dual-layer fluoropolymer tubing consisting of an outer layer of poly(tetrafluoroethylene) (PTFE) and an inner layer of FEP. When heated (>350 degrees C), the outer PTFE layer shrinks while the inner FEP layer melts, resulting in filling of all empty space inside the tubing with FEP. The channel structures are formed using tungsten wires as templates that are pulled out after completion of the shrinking and melting process. While several analytical devices have been reproducibly prepared and shown to function, this report describes a single example. A microreactor coupled to an electrochemical flow cell detects the biuret complex of the natively electroinactive peptide des-Tyr-Leu-enkephalin.

Biuret Reaction↗
PubMed1999

Infusion of plasma expanders may lead to unexpected results in urinary protein assays.

Overt proteinuria was detected in the urine of a potential kidney donor, ultimately leading to the refusal of the kidneys for transplantation purposes. Histological examination of the kidneys did not reveal any abnormalities. Searching for substances that could have interfered with the urinary total protein assay, the role of infused, modified gelatin plasma expanders was investigated. We therefore measured the concentration of protein before and after the addition of various artificial plasma expanders to urine. Only when Biuret reagent or Pyrogallol Red dye were used did we find elevated concentrations of protein. Other methods, including the turbidimetric assays, did not detect additional amounts of protein in the spiked urine. We conclude that the infusion of modified gelatin solutions may cause apparent proteinuria. This effect is not observed with starch-based plasma expanders. Clinical chemists and clinicians should be aware of this phenomenon and possibly repeat the analysis with a different technique.

Albumins↗
PubMed1992

Determination of total protein in highly purified factor IX concentrates.

Protein determination by the methods of Kjeldahl, Biuret, Bradford and UV absorbance at 280 nm have been studied in regard to accuracy, precision and simplicity. A reference preparation of a highly purified factor IX concentrate, Nanotiv, reconstituted to 1/5 of ordinary volume was used in the study in order to make a comparison between the different procedures. The Kjeldahl method resulted in a protein concentration of 3.7 mg/ml, whereas the Biuret, Bradford (BSA) and UV absorbance at 280 nm resulted in protein concentrations of 3.6, 2.5 and 2.8 mg/ml, respectively. The corresponding values for specific activity were 136, 140, 200 and 179 IU/mg, respectively. These results demonstrate a great variation in the response obtained by different methods for determination of total protein.

Biuret Reaction↗
PubMed1991

External quality assessment of total urinary protein estimation in the United Kingdom.

Three surveys of total urinary protein quantitation have been carried out in 350 UK laboratories. The seven specimens comprised buffered saline or normal human urine with added human serum albumin or human serum, or urine from individuals with nephrotic syndrome. Principal method groups were: turbidimetry (57%), dye binding (25%) and biuret (15%). For all surveys, overall between-laboratory agreement was poor (CV 22.8% to 57.1%), with ranges of results from 24-fold (0.83-20 g/L) to 366-fold (0.05-18.3 g/L); there was no improvement with time. The most popular method (sulphosalicylic acid turbidimetry) consistently performed the worst, and performance of the direct biuret procedure was also unacceptable; both methods should be discontinued. There were no significant differences in performance between the other major method groups, and none can be specifically recommended. Within the individual calibrant groups, least variation was observed with human serum. A common calibrant for all participants yielded significantly better between-laboratory agreement for all methods except sulphosalicylic acid turbidimetry.

Biuret Reaction↗
PubMed1985

Spinal fluid protein revisited: a reappraisal of the biuret procedure.

In this study our previously described selected method, a biuret procedure with deproteinization, for the determination of spinal fluid protein is thoroughly discussed against the background of the results found with a number of Lowry modifications. The use of various separation techniques, i.e. deproteinization, ultrafiltration and chromatography (HPLC), for protein analysis led to the question as to whether low molecular weight proteins in cerebrospinal fluid play an important role or not with respect to the choice of a selected method for the determination of total protein.

Biuret Reaction↗
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↗
PubMed1990

Effects of low and high relative molecular protein mass on four methods for total protein determination in urine.

Four commonly used methods for the determination of total protein in urine were compared. These were two biuret methods using different precipitants, a Ponceau S method and a Coomassie Brilliant Blue method. The protein content of the urines was also evaluated by sodium dodecylsulphate polyacrylamide gel electrophoresis. The biuret method with ethanolic phosphotungstic acid as precipitant correlated best with the Coomassie Brilliant Blue method (r = 0.944; p less than 0.001) but less well with the Ponceau S (r = 0.895; p less than 0.001) or biuret-trichloroacetic acid (r = 0.874; p less than 0.001) methods. For urines with normal electrophoretic protein patterns, the imprecise biuret-trichloroacetic acid method (cv = 18.5%) gave the greatest number of false high results (23 in 36 urines) as assessed by electrophoresis. False low results were common in low relative molecular mass (Mr) proteinuria, especially with the biuret-tricholoroacetic acid and Ponceau S methods. High Mr proteinuria rarely caused false low results. Discrepancies between methods appear to have resulted from incomplete precipitation of low Mr protein by trichloroacetic acid.

Azo Compounds↗
PubMed1975

Studies of fibrinogen measurement in the CAP survey program.

A review of the College of American Pathologists' Surveys experience in fibrinogen testing from 1967 to 1974 is reported. Trends in fibrinogen methodology and the emergence of a consensus choice of the modified thrombin time method are documented. The reasons for these changes from former methods are discussed.

Biuret Reaction↗
PubMed1975

Comparative testing of methods of protein concentration determination.

The authors have carried out various tests for determining protein concentrations. They have compared the methods, and have found, as well as proved, that the spectrophotometric method I of protein determination can be employed with sufficient accuracy for the purpose of serial tests.

Ammonium Sulfate↗
PubMed1999

[Purification and characterization of a novel antifungal peptide APS-1 produced by Bacillus cereus].

In previous study, we isolated an antagonist Bacillus cereus strain: S-1 from cotton plant. In field experiments, this bacterium was shown strong inhibition to several plant diseases. In this paper, we reported the purification of the antifungal substance produced by the bacterium and its properties. After the steps of acid precipitation, methanol and ethy lether extraction, Sephadex G100 and DEAE52 column chromatography, the antifungal material was purified. The purified material had absorption peak at 275 nm, and was exhibited negative in biuret color reaction. However after hydrolyzed with HCl, this substance shown positive in the same reaction. Amino acid analysis to the hydrolysate of APS-1 showed that APS-1 was composed of Glu, Asp, Tyr, Ser, Thr, Pro, Leu, Ile, Val and an unknown amino acid. Combining with its pratial resistance to proteinases, it was suggested that this antifungal material was a cyclic peptide. This peptide, named APS-1, with strong inhibition on the germination of spores of the phytopathogens tested, was shown high stability against ultraviolet radiation and heat. APS-1 may have potential role in plant diseases biological control.

Amino Acids↗
PubMed1992

Quantitative estimation of urinary protein excretion by refractometry.

Quantitative estimation of proteinuria done by the refractometric method was compared with that done by the sulphosalycilic acid method and biuret method in 102 urine samples. The analysis of results by students' t test showed no statistically significant difference between the three methods. It is concluded that quantitative estimation of urinary protein excretion by refractometric method is a simple cheap and reliable method and can be performed easily in the outpatient clinic. The instrument is quite handy and can be carried in the pocket.

Benzenesulfonates↗