Biuret Reaction Research Articles

Corrosion Products Formed on Copper exposed to humid SO2‐containing atmospheres

AbstractX‐ray diffraction analyses have been performed on samples of electrolytic copper (min. 99,9% Cu) exposed to humid atmoshperes at SO2‐supplies of 10 and 100μg SO2 per cm2 surface area per hour (10 and 100 ppm SO2. respectively). During the SO2 ‐exposures copper (II) sulphate (CuSO4 · 5 H2O) were the only crystalline phases formed in detectable amounts. Interruption of the SO2‐ supply resulted in the formation of copper (I) oxide and antlerite (CuSO4) · 2Cu (OH)2. During prolonged exposure brochanite (CuSO4 · 3Cu(OH)2) and langite (CuSO4· 3Cu(OH)2) and langite (CuSO4 · Cu(OH)2 · 2H2O) were also formed i. E. the Cu:S ratio of the basic copper sulphates increased with time. The formation of antlerite was preceeded by formation of an unidentified intermediate compound, probably a basic copper sulphate with a Cu:S ratio of less than three, and a simultaneous transformation of the copper (II) sulphate and copper (I, II) sulphite formed during the SO2‐exposure.

The Radiation Chemistry of Aqueous Solutions of Ammonium and Sodium Cyanides in the Megarad Dose Range

to large doses of 60Co -y rays. Radiation-chemical yields were determined for the decomposition of cyanide molecules, as were the total amount of nitrogen in nonvolatile nitrogen-containing radiolytic products, the free ammonia, and the yields of several amino acids released on acid hydrolysis of irradiated samples. Positive biuret reaction was found and its intensity used for an estimation of amide bond yields. Up to 18% of the nitrogen from nonvolatile radiolytic products appears in the amide bond, and up to 14% appears in natural amino acids. The origin of peptidic material is attributed to the polymerization initiated by cyano radicals produced in reactions of cyanides with OH, H, and eaq- species from radiolyzed water.

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.

Determination of Serum Proteins in the Presence of Dextran by means of the Biuret Reaction

264 biuret reagents for total protein determination in serum containing dextran were investigated. The usefulness of the method is dependent on proper ratio of the components of the reagent: concentrations of NaOH and copper sulphate, and the ratio of sodium-potassium tartrate to copper sulphate.

A study on the cuticle of Stegoalpheon kempi Chopra (Isopoda: Crustacea) in relation to its parasitic mode of life

Histological, histochemical, and possible functional properties of the cuticle in the bopyrid isopod parasite Stegoalpheon kempi Chopra are described. In the male, the epi- and the procuticle show similar histochemical characters. The protein constituent of the cuticle suggests a similarity to collagen and its significance is discussed in relation to the parasitic mode of life. In the female, the epicuticle is fuchsin-positive in Mallory's Triple and Masson's Trichrome stains, positive to tests for aromatic amino acids, but negative to tests for phenol, phenol oxidase, and quinone. In addition, the epicuticle shows auto-fluorescence and investigations on the fluorescent compounds present in the epicuticle protein show the presence of di- and tri-tyrosine. The function of these two unusual amino acids as possible cross links is discussed. The cuticle covering the pleopods lacks epicuticle, but it has a simple protein positive to the biuret test, and also a protein containing sulphydryl groups, perhaps as an adaptation for providing respiratory exchanges of gases through cuticle.

Improved method for determining serum protein concentrations in the far ultraviolet.

We examined the feasibility of measuring absorbance in the far ultraviolet for serum protein determination with a medium-priced, double-beam spectrophotometer. The method has been simplified by using an automatic dilutor to dilute the serum, and a flow-through cell and recorder in conjunction with the spectrophotometer. Because it is only necessary to dilute the serum and determine its absorbance, the procedure is quite rapid. As compared to the biuret reaction, interferences from hemolysis have been about halved. Interferences owing to light scattering by turbid sera have also been appreciably decreased by use of an anionic detegent (sodium dodecyl sulfate) as a serum diluent. Comparisons of the present method to the biuret and Kjeldahl methods indicate that it is relatively accurate, and is practical for routine use.

The Radiation Chemistry of Aqueous Solutions of Hydrogen Cyanide in the Megarad Dose Range

at their natural pH and at pH 2.4. The solutions were exposed to high doses of 6Co gamma rays (up to 16 Mrad) causing large decompositions (up to 90%). The decomposition yield, G(-HCN), and the radiation-chemical yields of formation of NH3, HCHO, H2, CO2, and of seven amino acids were determined. Also, the total yields of nitrogen in nitrogen-containing nonvolatile compounds, G(N), were measured. The irradiated solutions exhibited positive biuret reaction and the absorbancies depend on both the dose and the initial pH. Histidine, aspartic acid, threonine, serine, glutamic acid, alanine, and glycine were found in irradiated samples. Glycine was found to be the most abundant among the radiolytically produced amino acids; strong acid hydrolysis increases its yield by one or two orders of magnitude in samples irradiated initially at pH 2.4 as well as at their natural pH. The release of amino acids on hydrolysis and the positive biuret reaction suggest the presence of peptidic material in irradiated samples both at acid and neutral pH's. To account for these findings the formation of polymers (or their segments) having a peptidic structure was taken into consideration. The polymerization reactions were assumed to be initiated by the free radicals which were produced by HCN reactions with H, OH, and ej,- species. It has been concluded that the radiolysis of dilute aqueous

The Radiation Chemistry of Aqueous Solutions of Acetonitrile and Propionitrile in the Megarad Dose Range

A study was made of the radiolytic behavior of dilute, neutral, oxygen-free aqueous solutions of CH/sub 3/CN and C/sub 2/H/sub 5/CN. Small-molecular products were identified as RCHO, NH/sub 3/, CO/sub 2/, and H/sub 2/. The decomposition of nitrile is followed by high yields of formation of the nonvolatile nitrogen-containing compounds, G(N). The ..gamma..-irradiated solutions exhibit a positive biuret reaction. Several amino acids were identified among radiolytic products, and glycine and alanine were found to be the most abundant for CH/sub 3/CN and C/sub 2/H/sub 5/CH, respectively. Their yields increased after strong acid hydrolysis of the irradiated samples. The free radicals formed by reactions of RCN with H, OH, and e/sub aq/- were found to be important for the phenomena observed. It is suggested that the positive biuret reaction, ir spectra, and the release of amino acids on acid hydrolysis provide some evidence on the formation of peptidic materials and might be of interest for the evaluation of the role that ionizing radiation might have played in prebiotic chemical evolution in aqueous media.

THE ‘STUTTGARTER KARTENSPIEL’—SCIENTIFIC EXAMINATION OF THE PIGMENTS AND PAINT LAYERS OF MEDIEVAL PLAYING CARDS

In the paint layer of the Stuttgarter Kartenspiel the following pigments have been detected: white lead, chalk, lead-tin yellow, yellow lake, green basic copper sulphate hydrate (Cu4SO4(OH)6.xH2O), copper green (unidentified), azurite, vermilion, red lake, minium, charcoal black, and lamp black. A considerable variety of different metal applications results in the splendid appearance of the playing cards. Poliment twist-gold, unpolished silver and gold leaf on a white ground, mordant gilding, gilding with mosaic gold (SnS2), and glazing of twist-gold and mosaic gold with red lake have been observed.

An improved automated biuret method for the determination of microgram protein concentrations

The inherently simple biuret reaction is hampered by lack of sensitivity and reproducibility in the determination of low protein concentrations. A method utilizing a modified biuret formulation and colorimeter range expander permits protein determination in the 0.01–3.0 mg/ml range at a sampling rate of 60/hr without significant sample interaction. This inexpensive method is useful in investigations involving large numbers of samples with microgram protein content.

Standards for Total Serum Protein Assays— A Collaborative Study

We have studied the standardization of total serum protein assay with the biuret reaction. Standard solutions were prepared from lyophilized preparations of human serum albumin and bovine serum albumin, with corrections made for volatile material and ash contents. These solutions and a solution of crystalline albumin standard were analyzed with a new stable biuret reagent, to establish absorptivity values (values for the absorbance of a 1 g/liter final reaction mixture). The mean values obtained were 0.302, 0.292, and 0.290 for human serum albumin, bovine serum albumin, and the crystalline albumin, respectively. We believe that the established absorptivity value will improve the accuracy of serum protein determinations. We studied the linearity of the relation between color produced and protein concentration, with use of the solutions described above and a serum pool. The color adheres to Beer's law up to the highest concentration tested: 3 g/liter for HSA and BSA, and 2.8 g/liter for serum in the final reaction mixture. The new biuret reagent has been stable for one year at room temperature. We recommend the use of bovine serum albumin as a primary standard for serum protein assays. It is inexpensive, easily available, and exhibits the best linearity in the biuret reaction.

Pseudoproteinuria in tolmetin-treated patients.

In a clinical study of the new nonsteroidal anti-inflammatory drug tolmetin, the urines of 5 patients reacted positively when tested for protein by the standard sulfosalicylic acid method. Pseudoproteinuria, due to the precipitation by acid of the major metabolite of tolmetin, was suspected. The urines were subsequently tested for protein by the following alternate methods: solubility of acid precipitate test, heat coagulation test, Upjohn modification of the sulfosalicylic acid test, biuret test, Albustix, and electrophoresis. All were negative for protein. These results confirmed that the reactions with the sulfosalicylic acid test did not indicate true proteinuria but pseudoproteinuria. It is suggested that patients who receive tolmetin be tested for proteinuria by methods other than those involving acid precipitation.

Determination of protein in preparations of microsomes

Nine protein assay procedures based on the phenol, biuret, and picryl sulfonate reactions were compared as to their suitability for the determination of protein in microsomal preparations. All of the methods gave comparable results except the “macrobiuret,” which showed light-scattering interference, and the routine assays of Lowry et al. (1) and Schacterle and Pollack (14) which gave low values with calcium-precipitated microsomes. The advantages and disadvantages of the various assays relative to simplicity, interferences, and sensitivity are discussed. Three of the assay methods, the “insoluble biuret” (17) “nonaqueous biruet” (18), and a modification of the assay described by Schacterle and Pollack (14) (which is a modification of the assay of Lowry et al. (1), are particularly recommended.

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%.

Turbine mixer fundamentals and scale-up method at the Port Nickel Refinery

The Port Nickel Refinery at Braithwaite, Louisiana is being rehabilitated and expanded to achieve a capacity of 80 million pounds per year of nickel. The atmospheric leaching of granulated and ground matte with recirculated and aerated electrolyte from the copper tankhouse is one of the first steps in the Port Nickel flowsheet. An investigation was undertaken to develop the design parameters necessary for the commercial scale-up of this leach circuit. Mechanical factors to be specified include tank geometry, impeller type, and froth handling capability. Also needed for scale-up was quantitative data showing the effect of mixer power and gas input rate on the rate of oxygen transfer. During the leaching period, the rate mechanism changed from oxygen diffusion control to chemical rate control which necessitated careful correlation of the kinetic data with mixer scale-up parameters. The scaled up system calls for a co-current five stage leaching train. Use of a single turbine impeller on a vertical central shaft provides sufficient power for off-bottom solids suspension while providing the required oxygen mass transfer rate. Radial impellers are provided for the first three tanks in which oxygen transfer is rate controlling, and axial impellers for the last two tanks where hydrolysis of basic copper sulfate is the rate controlling factor.

The measurement of actin concentration in solution: A comparison of methods

Intrinsic optical density, Folin, and Biuret color development have been carefully studied as methods of determining actin concentration in solution. It appears that the Lowry (Folin) method is the most sensitive and reliable method as standardized by Kjeldahl analysis. Intrinsic optical density is also found to be a reliable method and the extinction coefficients of F and G actin at 280 and 290 nm are determined. The Biuret reaction is found to be the least reliable of the three methods for determining the concentration of actin in solution.

Evaluation and Elimination of the Interference by Starch in the Biuret Determination of Wheat Protein

In the biuret determination of wheat protein, starch, color substances and lipids extractable with an alkaline solution such as biuret reagent were found to interfere with the biuret method. Comparative evaluation of their effects revealed that starch, a major component of wheat, has the most significant effect on the biuret method. In the presence of starch, the correlation between Kjeldahl protein and the optical density of biuret was poor.It was found that several organic solvents effectively retarded solubilization of wheat starch in the biuret reaction mixture. By treatment of the wheat samples with these solvents prior to the biuret procedure, the effect of starch was completely eliminated and the optical density of biuret became closely correlated with Kjeldahl protein.

A NINETEENTH - CENTURY COLLECTION OF PIGMENTS AND PAINTING MATERIALS

AbstractFifty-six samples of an historic pigment collection were examined. A great number of the pigments are standard colours of the early nineteenth century, such as emerald green, chrome green, Prussian blue, Naples yellow, mummy, and sepia. Many pigments are extended with inert fillers, mainly barytes and gypsum. However some rare or unusual pigments were also detected. Among these are orange antimony sulphide and a green artificial basic copper sulphate of brochantite structure.

In vitro studies of testosterone and 5alpha-dihydrotestosterone binding in benign prostatic hypertrophy.

ABSTRACT The cytosol fractions of prostatic adenoma and of the rectus abdominis muscle, together with the respective plasma samples were investigated in 13 patients in order to clarify whether or not there is an androgen receptor in human benign prostatic hypertrophy. The following methods were used: High speed ultracentrifugation in a sucrose gradient and agar gel electrophoresis at low temperature, of the 100 000 g supernatants after in vitro incubation with 3H-testosterone, 3H-5α-dihydrotestosterone, and 3H-oestradiol-17β. In parallel experiments the supernatants were heated to 45°C for 1 h before the steroid incubation. Displacement experiments with a 100–500-fold excess of various cold androgens. In the supernatants as well as in the plasma samples the total protein concentration was measured by the biuret reaction. The concentration of albumin and of immunoglobulin G (IgG) in the various biological fluids was determined by quantitative immuno diffusion. After charcoal stripping the binding of testosterone and of 5α-dihydrotestosterone was estimated quantitatively and correlated to the plasma contamination. By the methods used no physico-chemical differences in the androgen binding properties of plasma and of prostate cytosol were observed. However, in any individual cytosol a higher 5α-DHT binding than could be related to the plasma contamination was obtained. The question therefore remains open, as to whether the augmented 5α-dihydrotestosterone binding relates to a cellular increase of sex hormone binding globulin (SHBG) or to androgen receptors which do not show up clearly under the experimental conditions used.

Factors Affecting Control of European Apple Canker by Difolatan and Basic Copper Sulfate

Factors Affecting Control of European Apple Canker by Difolatan and Basic Copper Sulfate