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PubMed1982

The quantitation and fractionation of proteins in cerebrospinal fluid.

The quantitation of CSF proteins has important clinical applications. Often the total protein level is quite useful but does not provide sufficient information to differentiate the disease state of the patient. The IgG/albumin index is a parameter frequently used as an indication of IgG production within the central nervous system. Hence, the levels of the albumin and globulin fractions must often be determined. Many methods exist for quantitations of total protein in CSF and the levels of the major protein fractions and for separating the various proteins present into their major protein fractions. For total protein quantitation, the turbidimetric method is common, but the Coomassie brilliant blue method may be the method of the future. For separation and quantitation of protein fractions, electrophoresis or some immunologic method is frequently used. The more sophisticated isoelectric focusing and two-dimensional techniques are limited to use mostly by research laboratories. With further sophistication of techniques for separating proteins and interpretation of the results thereby obtained, the methods which are now limited to research may be adapted by routine laboratories in the future.

Biuret Reaction↗
PubMed1983

Six methods for determining urinary protein compared.

Inter-laboratory surveys have shown that "routine methods" of urinary protein determination are often unsatisfactory. Therefore, we compared six frequently used methods for determination of protein in urine with respect to linearity, within-batch and between-batch precision, comparative bias, and practicability. We assayed dilutions of human and bovine albumin and serum, and fresh and lyophilized human urine. We find that the AACC Selected Method has poor practicability and poor precision under routine conditions, but good linearity. The sulfosalicylic acid/biuret technique is also impracticable, requires a large sample, and is not linear at low concentrations of urine protein. The Coomassie Brilliant Blue technique has a narrow range of linearity and poor precision. The sulfosalicylic acid/sodium sulfate turbidimetric method is not precise and cannot be standardized with bovine materials. The Ponceau-S technique has good performance characteristics and practicability, and we recommend it for routine laboratory use.

Australia↗
PubMed1981

A candidate reference method for determination of total protein in serum. II. Test for transferability.

The transferability of the candidate Reference Method for total serum protein was tested in eight laboratories in the United States and Europe. National Bureau of Standards SRM 927 (bovine serum albumin) was used in each analytical run as the calibration standard. The mean absorptivity value obtained for this material was 0.2983 L g-1 cm-1. Four serum pools prepared at the Centers for Disease Control were analyzed on each of 15 days. Within-run variation of the protein values (expressed as CV) in the eight laboratories ranged from 0.1 to 2.5% and day-to-day (total) variation in six of the laboratories ranged from 0.4 to 1%.

Biuret Reaction↗
PubMedDate not supplied

[The use of different albumin preparations as calibrators in determining the total protein in blood serum by the biuret method].

The authors have investigated the possibility of using various albumin preparations as calibrators in measurements of human blood serum total protein by the biuret method. Analysis of Precinorm U and Precipath U reference sera has demonstrated that use of various albumin preparations as calibrators may result in significant deviations (as much as 27%) of the resultant values from the due ones.

Biuret Reaction↗
PubMed1976

[Quantitative protein estimation following standardized concentration of diluted physiological fluids (author's transl)].

After the tenfold concentration of 1:100 diluted standard solutions in the Minicon B-15 concentrator, the quantitative determination of total protein and of ten single proteins showed a decreased yield. These losses are not standardizable. The reason is analyzed and discussed. Therefore, the quantitative estimation of single proteins by means of immunochemical methods as well as the densitometry of electrophoreses of dilute protein solutions following concentration should be interpreted with caution, because changes in the absolute and relative concentration of proteins are to be expected. These methods are not suitable for exact measurements. An unstandardizable correction coefficient ought to be considered.

Biuret Reaction↗
PubMedDate not supplied

Folic acid age correlation established on folates determinations in cell homogenates.

From the available data, there has resulted that folic acid quantity in homogenate, coming from various organs, collected from young animals is much larger than for the other age categories. These results may be correlated with intense cell proliferation and development processes that take place in the young tissues as compared to rather low values established from grown-ups and old ranges. When comparing the folates quantity found in homogenate resulting from various organs we may ascertain that, if the folates are related to grams of tissue under the test, they are more in spleen than in kidneys, liver and brains respectively. If the folates are reported to tissue protein milligrams it may be ascertained that a larger quantity of folates is found in the brains than in the other studied organs that may be due to big dilution of the proteins in the brains.

Aging↗
PubMed1977

Simple procedure for measuring total protein in urine.

We describe a procedure for measuring total protein in urine. The method is simple, sensitive, and free of interference from drugs that are known to affect other commonly used methods. The CV for a 1.1 g/liter urine control in daily, routine use is 4.6%. The procedure involves adsorbing the protein onto cellulose powder, binding of Ponceau S dye by the protein, washing away excess dye, and eluting the bound dye into dilute NaOH for colorimetry. Comparison of results by this method with those by the biuret and turbidimetric procedures showed good agreement in those cases where the specimens were suitable for assay by the comparison methods.

Biuret Reaction↗
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↗
PubMed1998

[Materials for carrying out external quality control in the determination of total protein].

Quaternary bis-ammonium compound No. 82 (QAC-82) is a highly effective antibacterial biochemical stabilizer of total protein. In concentrations of 3.4-13.6 mmol/liter, it preserves the content of protein in the blood serum for 40 days at 18-20 degrees C. For preparing reference material, 5 ml human or animal serum is added to 95 ml 5.25 mM aqueous solution of QAC-82, mixed, stored at room temperature, and used for assessing the quality of total protein measurements by the biuret method.

Biuret Reaction↗
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↗
PubMed1987

Determination of total protein in human seminal plasma.

Methodological problems are encountered in determinating human seminal protein content since results are influenced especially by techniques which are used, and by modifications due to liquefaction process. In order to test these two points, three methods (Folin, Biuret and Meulemans's reactions) were applied to the same seminal samples and results were compared. The differences seem principally due to the high level of glycoproteins. To determine the modifications of total protein content with time after semen collection, each sample was separated in aliquot fractions and proteolysis was blocked at different times for each fraction. There is an increase of the protein concentration during the first fifteen minutes that follows semen collection. The cause of this phenomenon is discussed.

Electrophoresis↗
PubMed1985

The variable reagent blank: protein determination as a model.

Three total protein assays were analyzed to determine the extent of deviation encountered when a constant measured reagent blank is compared to a continuously decreasing true reagent blank. This blank effect owes its regressive nature to the consumption of the active reagent ingredient by the protein reactive species, variably and sometimes, with certain reactants, nonlinearly in the presence of increasing protein concentrations. However, the blank effect of interest here is apparent only when the reagent and the reagent-protein complex present overlapping spectra and therefore absorb at the wavelength of measurement. Thus it was found that while the biuret and the Coomassie brilliant blue assays produced pronounced differences in the variable true reagent blanks, the Folin-Ciocalteau reaction did not develop a deviation from the true blank since the reagent blank does not absorb to any extent at the assay wavelength. In this manner, the latter procedure could serve as a marker against which the former two blank reactions can be shown to display relatively excessive deviations.

Biuret Reaction↗
PubMed1994

[Comparison of protein assays for ejiao].

Ejiao exhibits identical spectral characteristics with those of reference gelatin in Murphy's UV spectrophotometry and color-yielding reactions performed according to Gornall's biuret and Lowry's Folin phenol procedures respectively. Results of protein assays of Ejiao measured by above-mentioned photometric methods were in good approximation to each other using gelatin as standard and comparable with that of Kjeldahl nitrogen determination.

Materia Medica↗