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High-sensitivity dye binding assay for albumin in urine.

We developed a dye-binding method for albumin in urine based on bis (3',3"-diiodo4'4"-dihydroxy-5'5"-dinitrophenyl)-3,4,5,6-tetrabr omosulfonphthalein (DIDNTB), a dye that has a higher chemical sensitivity and specificity for albumin when compared to two other commonly used dyes. We prepared urine dipsticks with DIDNTB and certain other compounds to prevent "nonspecific" binding to the dipstick matrix. The detection limit for albumin with DIDNTB as the dye is about 10 mg/L. The extent of dye binding to proteins and other compounds was studied using ultracentrifugation and a selectively permeable membrane that permitted the passage of free but not bound dye; we believe this method is superior to photometric titration. The affinity of the dyes for albumin was found to be pH dependent with stronger binding at pH 1.8 than at pH 7.0. At pH 1.8, DIDNTB had a ca.10-fold greater binding coefficient to albumin when compared to the widely used dyes, tetrabromophenol blue (CI 4430-25-5) or bromophenol blue (CI 115-39-9). We developed a system that minimized nonspecific binding by the dye through the use of polymethyl vinyl ethers and bis-(heptapropylene glycol) carbonate. DIDNTB showed a greater chemical specificity for albumin when compared to most other proteins. The new albumin dipsticks are resistant to many potential interferences at substantial concentrations, making the dipsticks suitable to screen for albuminuria.

Bromphenol Blue↗

Kinetics studies on the renal transport of probenecid in vitro.

1. The kinetic parameters of renal transport of probenecid have been assessed by studying the uptake of the drug in rabbit kidney tubules incubated in an electrolyte medium under various conditions. 2. The added compounds inhibited the uptake of probenecid both by kidney cortical slices and separated renal tubule preparations in the following order: p-aminohippurate less than phenol red less than bromophenol blue less than bromocresol green. A reversible competitive inhibitory effect of these organic anions on the renal accumulation of the drug was observed. 3. The Km for renal uptake of probenecid in separated tubules (0.04 mM) and the KI values calculated in this system for p-aminohippurate (0.5 mM), phenol red (0.09 mM), bromophenol blue (0.02 mM) and bromocresol green (0.015 mM) were found to be in good agreement with the corresponding KI value of probenecid and Km values of these compounds previously observed in various kidney tissue preparations. 4. On the basis of above mentioned findings, it is concluded that probenecid, p-aminohippurate and various phenolsulphonphthalein dyes are transported by the common renal organic anion transport system.

Animals↗

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↗

Extractive spectrophotometric methods for determination of diltiazem HCl in pharmaceutical formulations using bromothymol blue, bromophenol blue and bromocresol green.

Three simple and sensitive extractive spectrophotometric methods have been described for the assay of diltiazem hydrochloride either in pure form or in pharmaceutical formulations. The developed methods involve formation of coloured chloroform extractable ion-pair complexes of the drug with bromothymol blue (BTB), bromophenol blue (BPB) and bromocresol green (BCG) in acidic medium. The extracted complexes showed absorbance maxima at 415 nm for all three methods. Beer's law is obeyed in the concentration ranges 2.5-20.0, 2.5-10.0 and 2.5-12.5 microg ml(-1) with BTB, BPB and BCG, respectively. The methods have been applied to the determination of drug in commercial tablets and capsules. Results of analysis were validated statistically and through recovery studies.

Bromcresol Green↗

Bromophenol blue protein assay: improvement in buffer tolerance and adaptation for the measurement of proteolytic activity.

A modification of the bromophenol blue dye binding procedure of protein estimation is described. Substitution of glycine/phosphoric acid, pH 2.6, for dilute acetic acid in the colour reagent extended the applicability of the procedure to protein solutions containing buffers of various pH values. This was, however, accompanied by approximately 25% loss in the sensitivity of the procedure. The modified reagent exhibited very marked tolerance to detergents and could be successfully adapted for the measurement of proteolytic activity in acidic, neutral or alkaline pH ranges.

Bromphenol Blue↗

Optical detection in microscopic domains. 2. Inner filter effects for monitoring nonfluorescent molecules with fluorescence.

In this research, we test whether optical detection techniques show different characteristics in microscopic solution volumes (nano-, pico-, and femtoliter range) compared to the usual macroscopic samples. In part 1 (Lu, H.; et al. Anal Chem. 2000, 72, 1569-1576.) absorption spectra of high quality were obtained, quantitatively obeying both Beer-Lambert's law and the law of superposition, despite the micrometer optical path lengths and the curvatures of the droplets studied. Addition and subtraction of absorbing molecules with diffusional microburets (DMBs), as well as more complex operations (simultaneous addition of one and subtraction of another molecule, and a consuming scheme), have been monitored with good spectral and temporal resolution. Despite the unexpectedly good performance of absorption microspectrometry, fluorescence-based detection schemes are considered more sensitive for microscopic studies (e.g., cell physiology). In this paper, we test whether fluorescence-based schemes can be used to indirectly measure nonfluorescent chemicals in microscopic domains. Absorption by such molecules will cause a corresponding decrease in overall fluorescence intensity of the added standard fluorescent dye. This phenomenon, the inner filter effect (IFE), was tested using Lucifer Yellow CH (LY) as the fluorescent standard dye. Its effective irradiation was absorbed by Orange G (primary IFE) or its emission by Bromophenol Blue (secondary IFE). By utilizing these phenomena, (1) we measured the concentration of absorbing molecules in microscopic samples by adding a standard amount of LY by a DMB, and (2) we monitored DMB delivery of nonfluorescent reagents into droplets preloaded with LY. The results prove that IFEs are sensitive indirect means of detection of absorbing molecules in microscopic domains. The techniques presented are expected to find applications in cellular studies where absorption spectrometry is usually not considered.

Algorithms↗

A comparative study on biosorption characteristics of certain fungi for bromophenol blue dye.

Laboratory investigations of the potential use of dried biomasses of Rhizopus stolonifer, Fusarium sp., Geotrichum sp., and Aspergillus fumigatus as biosorbents for the removal of bromophenol blue (BPB) dye from aqueous solutions were conducted. Kinetics studies indicated that the BPB dye uptake processes can be well described by the pseudo-second-order model. The fungal biomasses exhibited the highest dye biosorption at pH 2.0. The Langmuir adsorption model appears to fit the dye biosorption better than the Freundlich model, with maximum dye uptake capacities ranging from 526 to 1,111 mg/g, depending on the biomass used.

Adsorption↗

Microdetermination of proteins by resonance light scattering spectroscopy with bromophenol blue.

Reaction of bromophenol blue with proteins results in an enhanced resonance light scattering at 334 nm. Based on this, a new quantitative determination method for proteins in the aqueous solution is established. This assay is characterized by high sensitivity (0.34-18.7 microg/ml), short reaction time (>2 min), and simplicity (a one-step assay). Due to protein-to-protein variability, this method gave results higher than that of the bromocresol green assay in detection of human serum albumin.

Amino Acids↗

Studies of complex formation between the bromophenol blue and some important aminoquinoline antimalarials.

A simple and rapid colorimetric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug base with bromophenol blue to give a stable ion-pair complex. The spectra of the complex shows a maxima at 415-420 nm with high apparent molar absorptivities. Beer's law was obeyed in the concentration range 1-8, 2-10 and 2-12 micrograms.ml-1 for amodiaquine hydrochloride, primaquine phosphate and chloroquine phosphate respectively. The proposed method was applied to the determination of these drugs in certain formulations and the results were favourably comparable to the official methods.

Aminoquinolines↗

Substituting Coomassie Brilliant Blue for bromophenol blue in two-dimensional electrophoresis buffers improves the resolution of focusing patterns.

In a new area of postgenomics challenges, the optimization of protein identification has become a central goal in microbiochemistry. In this work, we demonstrate that the substitution of Coomassie Brilliant Blue for bromophenol blue in two-dimensional electrophoresis (2-DE) buffers improves the focusing of whole proteins from Pseudomonas aeruginosa. This improvement of focusing concerns more particularly basic proteins. This enhancement may be attributed to a better transfer from the first to the second dimension, which probably highlights an increase in the solubility of proteins in the IPG strips. Hence, the use of an efficient tracking dye in the 2-DE buffers may enlarge protein recovery on proteome maps.

Bacterial Proteins↗

Simple spectrophotometric determination of cinnarizine in its dosage forms.

A direct, extraction-free spectrophotometric method has been developed for the determination of cinnarizine in pharmaceutical preparations. The method is based on ion-pair formation between the drug and three acidic (sulphonphthalein) dyes; namely bromocresol green (BCG), bromocresol purple (BCP) and bromophenol blue (BPB) which induces an instantaneous bathochromic shift of the maximum in the drug spectrum. Conformity to Beer's law enabled the assay of dosage forms of the drug. Compared with a reference method, the results obtained were of equal accuracy and precision. A more detailed investigation of the cinnarizine-BCG ion pair complex was made with respect to its composition, association constant and free energy change. In addition, this method was also found to be specific for the analysis of cinnarizine in the presence of some of the co-formulated drugs, such as pyridoxine hydrochloride and digoxin.

Bromcresol Green↗

Spectrophotometric determination of certain antidepressants in pharmaceutical preparations.

Simple and reproducible spectrophotometric methods have been developed for determination of sertraline, fluoxetine, and venlafaxine in pharmaceutical preparations. The methods are based on the reactions between the studied drug substances and ion-pair agents (bromothymol blue, bromocresol green, or bromophenol blue) to produce yellow-colored ion-pair complexes in acidic buffers. After extracting in chloroform, the ion-pair complexes are spectrophotometrically determined at the optimum wavelength. Optimizations of the reaction conditions were carried out. Beer's law was obeyed within the concentration range from 1 to 15 microg/mL. The molar absorptivity, Sandell sensitivity, and detection and quantification limits were also determined. The developed methods were applied successfully for the determination of these drugs in some available commercial preparations. The results were compared statistically with those obtained from reported high-performance liquid chromatography methods.

Antidepressive Agents↗

Theoretical analysis concerning the characteristics of a dye-binding method for determining serum protein based on protein error of pH indicator: effect of buffer concentration of the color reagent on the color development.

In the dye-binding method based on protein error of a pH indicator, the color development has been reported to be markedly affected by the buffer concentration of the color reagent. In this study, the author analyzed this phenomenon by a theoretical calculation based on the chemical equilibrium of protein error. The calculation was performed on the assumption that both the dissociated dye anion and the anion contained in the buffer solution react with protein, forming a dye-protein complex and an anion-protein complex, respectively. The calculated results were compared with those obtained by the experiments using bromophenol blue, bromocresol green and bromocresol purple that are employed widely for determining the human serum albumin concentration clinically. The calculated results of this method are summarized as follows: (1) the color development decreases with the increase in the concentration of the anion contained in the buffer solution; (2) the calibration curve is more linear in the higher concentration of the anion than in the lower one. These calculated results agreed well with the experimental ones. From these results, it was concluded that the change in the color development by the buffer concentration of the color reagent is due to the change in the concentration of the buffer anion.

Blood Proteins↗

Application of the bromophenol blue (BPB) staining method to rat fetal cartilage previously stained with alizarin red S.

The application of a convenient bromophenol blue (BPB) cartilage staining method on rat fetal skeleton, previously stained with alizarin red S, was investigated. This staining method made it possible to observe uncertain cartilage anomalies and unossified caudal vertebrae, which were poorly detected by single staining with alizarin red S. Namely, the anomaly of chondral rib bifurcation was detected and the number of unossified caudal vertebrae in rat fetuses was demonstrated as being identical with adult rat caudal vertebrae. The BPB staining has the notice to make the pH 4 adjusted specimens and has the advantage of fading with water or ethanol at pH 8 without discoloration of alizarin red S on the bones.

Animals↗

Improvement of the micromethod for the limulus lysate test.

Frauch's micro-slide method was improved to facilitate the endpoint-determination of the Limulus test. Two precise observations, by inverted phase contrast microscopy and with a staining procedure, were newly performed as additions to the slide test. The staining procedure was proposed as an improved method for the Limulus test since it is simple and convenient. In the staining method, bromophenol blue (BPB) solution was used as the staining solution. A negative (-), a strong positive (++) and a weak positive reaction (+) were characterized by a "ring" formation, a "cloud-like" spread of gel and a "spot" in the "cloud" respectively. Since the distinction between (-) and (+) reactions was obvious in the proposed method, determination of the endpoint was easier than in the ordinary tube and Frauch's method. The sensitivity of the present method was equal to or higher than that of other methods. Inverted phase contrast microscopy was utilized to confirm the findings obtained by the staining method. The volume of the lysate used in this method was as little as 1/10 of that used in the tube method.

Blood Platelets↗

Effect of nonuniform bile flow rate on the rate of biliary excretion of bromophenol blue in the beagle.

Following the intravenous administration of bromophenol blue to beagle dogs, graphs of the biliary excretion rate versus time displayed drastic fluctuations which render them of little value for standard pharmacokinetic modeling purposes. It was shown that these fluctuations in excretion rate are highly correlated with corresponding fluctuations in the bile flow rate. An expression was derived which accounts for the primary effect of nonuniform bile flow rate on the biliary excretion rate. This treatment would enable the use of such biliary excretion rate data for pharmacokinetic modeling. Secondary effects of nonuniform bile flow on the biliary excretion rate are also discussed. It is suggested that the modeling of other flow rate-dependent elimination processes could benefit from such a treatment.

Animals↗

Characterization of Rose Bengal binding to sinusoidal and bile canalicular plasma membrane from rat liver.

The binding of Rose bengal, a model organic anion, to sinusoidal and bile canalicular membrane fractions isolated from rat liver was compared. The fluorescence change of Rose bengal after being bound to liver plasma membranes was utilized for measuring the binding. The dissociation constants (Kd = 0.1-0.12 microM) and the binding capacities (n = 11-15 nmol/mg protein) for Rose bengal are comparable between the two membrane fractions, although the n value for sinusoidal membrane is somewhat larger than that for bile canalicular membrane. The Rose bengal binding to both membrane fractions was inhibited by various organic anions at relatively low concentrations, i.e., the half-inhibition concentrations (IC50) for Indocyanine green, sulfobromophthalein, Bromophenol blue and 1-anilino-8-naphthalene sulfonate were 0.1, 100, 1.5-2.5 and 100 microM, respectively, while taurocholate did not inhibit the Rose bengal binding to either membrane fraction at these low concentration ranges. The type of inhibition of sulfobromophthalein and Indocyanine green for Rose bengal binding is different between the two membrane domains. That is, in sinusoidal and bile canalicular membrane fractions, these organic anions exhibit mixed-type and competitive-type inhibition, respectively. It was suggested that the fluorescence method using Rose bengal may provide a simple method for detecting the specific organic anion binding protein(s) in the liver plasma membrane.

Anilino Naphthalenesulfonates↗

A simple spectrophotometric method for the determination of beta-blockers in dosage forms.

A simple, extraction-free spectrophotometric method is proposed for the analysis of some beta-blockers, namely atenolol, timolol and nadolol. The method is based on the interaction of the drugs in chloroform with 0.1% chloroformic solutions of acidic sulphophthalein dyes to form stable, yellow-coloured, ion-pair complexes peaking at 415 nm. The dyes used were bromophenol blue (BPB), bromothymol blue (BTB) and bromocresol purple (BCP). Under the optimum conditions, the three drugs could be assayed in the concentration range 1-10 microg ml(-1) with correlation coefficient (n = 5) more than 0.999 in all cases. The stoichiometry of the reaction was found to be 1:1 in all cases and the conditional stability constant (K(F)) of the complexes have been calculated. The free energy changes (DeltaG) were determined for all complexes formed. The interference likely to be introduced from co-formulated drugs was studied and their tolerance limits were determined. The proposed method was then applied to dosage-forms the percentage recoveries ranges from 99.12-100.95, and the results obtained were compared favorably with those given with the official methods.

Adrenergic beta-Antagonists↗