Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biuret”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
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↗
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↗
PubMedDate not supplied

Comparison of three methods for plasma fibrinogen.

Three plasma fibrinogen methods are presented based on (1) clottable protein assay by Biuret reagent, (2) measurement of clot absorbance and (3) thrombin time. These methods show good correlation and adequate precision on normal subjects as well as heparinized plasmas. The effects of interference owing to hemolysis, lipemia, bilirubin, heparin and fibrinogen degradation products are discussed briefly.

Bilirubin↗
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↗
PubMed1979

[Usage of the gel filtration method for the determination of urinary proteins (author's transl)].

The urinary proteins determination was carried out after purification by gel filtration over Sephadex rosin. The proteins eluaded react with Biuret-reagent to establish the coloured copper-proteins complex. If proteins concentrations is inferior, the proteins can be determinated by the copper-proteins complex isolation with second gel filtration and titrating Cu++ with reactives: dietildithiocarbamate or the PAR (4-(2pyridyl-azo)resorcinol monosodium salt).

Biuret↗
PubMed1989

Application of a silver-binding assay to the determination of protein in cerebrospinal fluid.

We evaluated a silver-binding assay for use in measuring total protein in cerebrospinal fluid. The advantage of this procedure over other methods is that, because of its sensitivity, it requires only a 0.5-microL sample. The procedure, which takes approximately 40 min to complete, involves dilution of 0.5-microL samples to 1 mL with distilled water containing sodium dodecyl sulfate, followed by addition of glutaraldehyde and an ammoniacal silver solution. After color development for 30 min, the reaction is terminated with sodium thiosulfate and the absorbance is measured at 420 nm. This assay displayed within-run and day-to-day precision (CV) of 3.1% to 13% over the range of 210 to 1370 mg/L. It showed substantially less protein-to-protein variation than the Coomassie Blue dye-binding procedure when tested with albumin, globulin, and transferrin. It also yielded an accurate estimation of hemoglobin. Moreover, preliminary studies suggested that it was capable of quantifying immunoglobulin light chains and glycoproteins. In a study of 54 human cerebrospinal fluid samples, results of the silver-binding assay corresponded more closely with those obtained with a rate biuret assay (intraclass correlation coefficient = 0.91) than did either the dye-binding or classical Lowry methods.

Albumins↗
PubMed1985

Three turbidimetric methods for determining total protein compared.

We used human serum protein fractions to evaluate the sensitivity and bias of three turbidimetric methods for determining concentrations of proteins. Each fraction (Cohn Fractions II, III, IV, and V) was assigned a protein concentration value that was determined by the biuret method, which we calibrated with purified monomer of human serum albumin. All three turbidimetric methods (those involving sulfosalicylic acid/sodium sulfate, trichloroacetic acid, and alkaline benzethonium chloride) gave acceptable results for Fraction V with crystallized human serum albumin as the reference material, but there was bias by each of the three methods for the three globulin fractions. The method involving alkaline benzethonium chloride with measurement at 450 nm had the best sensitivity within the range of linearity and the most consistent bias among the three globulin fractions. These results define the dilemma for valid calibration of these methods for total serum protein in cerebrospinal fluid and urine.

Biuret↗
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↗
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↗
PubMed2005

[Effect of tamoxifen on plasma proteins in diabetes mellitus type 1].

PURPOSE: Considering that important scientific advances have been obtained through studies based on experimental Diabetes mellitus, and that tamoxifen action in humans remains unknown, the aim of the present work is to follow the modifications promoted by diabetes and tamoxifen in the electrophoretic profile of plasmatic proteins. METHODS: It was used 27 Wistar female rats (180-250 body weight), randomicaly divided into five groups: C1 (n = 3, received vehicle), C2 (n = 3, no treatment), T (n =5, treated with tamoxifen, 0.3mg/Kg/day), D (n = 8, experimental diabetes by estreptozotocin, 45mg/Kg and DT (n = 8, diabetic treated with tamoxifen). The electrophoresis was accomplished in cellulose acetate. pH 8.6-8.8, TECNOW chamber, and the strains were stained by Ponceau S. The total proteins were determined by the Biuret method (Labtest). Proteinograms were obtained in densitometer BioSystems BTS-235. RESULTS: Albumin decreased progressively in the groups T, D and DT; a1 fraction increased in groups T and DT; a2 fraction increased in groups T and D, including a synergic effect in group DT; a fraction increased in groups T and D; a fraction increased in groups T, D and DT. CONCLUSIONS: The results indicate an acute phase resposta, with synergic effect of tamoxifen and diabetes, suggesting a probable hepatic lesion.

Analysis of Variance↗
PubMed2000

Too hot to handle: an unusual exposure of HDI in specialty painters.

BACKGROUND: Hexamethylene Diisocyanate (HDI) is a color stable aliphatic isocyanate that is used in specialty paints as a hardener. Due to the lower vapor pressure of its commercial biuret form, it is considered a relatively "safe" isocyanate from an exposure standpoint. This case series reports on an unusual toxic exposure to HDI. Between November 1993 and May 1994, seven specialty painters and one boiler maker who were working at three different power plants were examined at the Institute of Occupational and Environmental Health at West Virginia University. At their respective work sites, HDI was applied to the hot surfaces of boilers that were not shut down, and allowed sufficient time to cool. Consequently, these workers were exposed to volatile HDI and its thermal decomposition products. METHODS: All of these workers underwent a complete physical examination, spirometry, and methacholine challenge testing. RESULTS: All 8 workers complained of dyspnea, while 4 of the 8 also complained of rash. On examination 3 workers were methacholine challenge positive and 2 had persistent rash. At follow-up 4 years later, 5 workers still had to use inhalation medication and one had progressive asthma and dermatitis. All 8 workers, by the time of the follow-up, had gone through economic and occupational changes. CONCLUSIONS: This case series reports on an unusual exposure to HDI. It is unusual in that: 1) There were two simultaneous sentinel cases with two different Material Safety Data Sheets (MSDS) for the same product, 2) Exposure was to volatile HDI and its decomposition products and 3) Hazardous conditions of exposure occurred at three different sites.

Adult↗
PubMedDate not supplied

Cytotoxicity of EDTA used in biological samples: effect on some human breast-milk studies.

Ethylene diamine tetraacetic acid (EDTA) is a chelator for metal ions that has found widespread application in modern medicine and pharmacy. However, few studies have examined the cytotoxic side-effects of EDTA when added to biological samples upon various laboratory analyses. The present study was aimed at assessing the artefactual side-effects of EDTA on some biochemical assays performed on human milk samples. The secondary effects of addition of EDTA (at a final concentration of 20 mmol l(-1)) to inhibit complement system activation in human breast-milk samples were examined, using different laboratory techniques and methods, compared to milk samples with equivalent volumes of phosphate-buffered saline added. Assays considered included Biuret's test for total protein measurement, CH50 assays of whole complement activity, pH measurements and total cell counts. The toxic effects of EDTA included breast-milk cell loss, disruption of milk fat globule membrane and subsequent release of membrane-bound protein, free fatty acids and reduction in pH. It also caused false-positive results of haemolytic assays.

Animals↗
PubMed1975

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.

Anti-Inflammatory Agents↗
PubMed1991

Validation of a non-invasive technique to assess immediate or delayed onset of airway hypersensitivity in guinea-pigs.

Conscious Hartley guinea-pigs were sensitized with trimellitic anhydride (TMA) or trimeric hexamethylene diisocyanate biuret (Des-N) by repeated intradermal injections or by inhalation exposure. Immediate- and delayed-onset pulmonary reactions were recorded during/after challenges with the hapten or protein conjugate of the hapten, respectively. The positive control was sensitized and challenged with ovalbumin (OA) by inhalation. Homocytotropic antibodies of the IgG1 type were determined to correlate antibody titres and pulmonary responses. Immediate-onset pulmonary reactions were apparent in guinea-pigs sensitized by inhalation of TMA and OA. Animals sensitized intradermally with TMA demonstrated more vigorous immediate-onset reactions than animals sensitized by inhalation. The measurement of breathing parameters demonstrated that the ability to detect immediate-onset airway hyperreactivity was best when the breathing rate and tidal and minute volumes were measured. None of the measurements for delayed-onset reactions presented conclusive results, since sensitized as well as naive guinea-pigs demonstrated a delayed increase of breathing frequency. Antigen-specific IgG1 antibodies were several orders of magnitude higher in intradermally sensitized animals compared with animals sensitized by inhalation. Although Des-N-sensitized guinea-pigs experienced high IgG1-antibody titres, no response of pulmonary hypersensitivity could be elicited after hapten or conjugate challenge. In summary, it would appear that pulmonary hypersensitivity depends on factors other than IgG1 antibody titres. For the screening of chemicals, the dermal induction and inhalation challenge protocol was revealed to be more sensitive than the inhalation induction and inhalation challenge protocol.

Administration, Inhalation↗
PubMed1991

Continuous aqueous phase extraction of proteins: automated on-line monitoring of fumarase activity and protein concentration.

Automated assay techniques are described for on-line measurements of fumarase activity and total protein concentration, including in-line sample dilution and sample multiplexing during continuous aqueous phase extraction. Fumarase was determined by following the conversion of L-malate to fumurate at a wavelength of 250 nm, while the protein assay was based on the Biuret reaction. Actual assay times of 2 and 4 min were achieved for the fumarase and protein measurements, respectively, with an effective measurement cycle time of 2 min. Standard deviations of c. 3.2 and 2% of the measured values were calculated for the enzyme and protein values, respectively. The assay system was coupled to a computer to allow on-line data visualization and storage.

Automation↗
PubMed2004

Effect of roasting history and buffer composition on peanut protein extraction efficiency.

Peanut is a major allergenic food. Undeclared peanut (allergens) from mis-formulation or contamination during food processing pose a potential risk for sensitized individuals and must be avoided. Reliable detection and quantification methods for food allergens are necessary in order to ensure compliance with food labelling and to improve consumer protection. The extraction of proteins from allergenic foods and complex food products is an important step in any allergen detection method. In this study, the protein extraction efficiency of various buffers prepared in-house and some extraction buffers included in some commercial allergen enzyme-linked immunosorbent assay (ELISA) test kits for peanut determination in food products were tested. In addition, the effect of roasting history on the extractability of peanut protein was investigated by the biuret and the bicinchoninic acid (BCA) assays. Elevated roasting temperatures in food processing were found to have a major impact on protein extraction efficiency by reducing protein yields of oil and dry roasted peanuts by 50-75% and 75-80%, respectively, compared with the raw material. Extraction buffers operating in the higher pH range (pH 8-11) showed best yields.

Allergens↗
PubMed1980

Relationship between exposure to heavy metals and prevalence of renal dysfunction.

Total proteinuria (biuret method) and the urinary excretion of specific proteins (albumin, transferrin, orosomucoid and IgG measured by an automated immunoprecipitin reaction and beta 2-microglobulin determined by radioimmunoassay) have been assessed in four groups of workers: a control group (n = 88) and a group exposed to cadmium (n = 148), mercury vapour (n = 63) and lead (n = 25) respectively. The results demonstrate that a moderate exposure to lead (lead concentration in blood < 62 micrograms/100 ml) does not change the prevalence of renal dysfunction, whereas mercury vapour exposure increases the prevalence of subjects with excessive excretion of albumin (> 12 mg/g creatinine), orosomucoid (> 4.35 mg/g creat.) and IgG (> 3.5 mg/g creat.). Besides an increased excretion of beta 2-microglobulin (> 200 micrograms/g creat.) workers exposed to cadmium excrete a greater amount of high molecular weight proteins. An increased excretion of urinary proteins occurs when mercury and cadmium level in urine exceeds 50 and 10 micrograms/g creatinine respectively.

Cadmium Poisoning↗