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At least 19 recordsLinked to original sources
PubMed1981

Continuous-flow serum albumin determination by reaction with picrate ions, with use of a flow-through picrate ion electrode.

An automated potentiometric method for serum albumin determination by use of the picrate/albumin reaction is described. A continuous-flow system and a specially designed flow-through picrate ion electrode were used in making the measurements. Various factors affecting the reaction, such as pH, picrate ion concentration, and reaction time, were studied. Peak height in millivolts and albumin concentration were linearly related in the range 10-70 g/L. Both within-run and day-to-day, the CV for the method was about 2%. Analytical recovery of albumin added to serum samples ranged from 97.0 to 110.3%, averaging 102.2%. Results compare favorably with those by the established bromcresol green method. The proposed method is suitable for routine use and for screening tests.

Electrodes↗
PubMed1988

Structures of acetylcholine picrate and methoxycarbonylcholine picrate hemihydrate.

Acetylcholine picrate, C7H16NO2+.C6H2N3-O7-, Mr = 374.3, orthorhombic, Pbca, at 105 K: a = 18.799 (4), b = 7.726 (2), c = 22.878 (4) A, V = 3323 (2) A3, Z = 8, Dm(295 K, flotation) = 1.44, D chi(105 K) = 1.496 Mg m-3, mu(Mo K alpha) = 0.120 mm-1, F(000) = 1568, m.p. (hot-stage microscope) 381-382 K, R = 0.048 for 1049 observed [I greater than or equal to 3.0 sigma(I)] reflections. Methoxycarbonylcholine picrate hemihydrate, C7H16NO3+.C6H2N3O7-.1/2H2O, Mr = 399.3, monoclinic, P2/n, at 105 K: a = 11.337 (16), b = 7.279 (2), c = 21.424 (13) A, beta = 103.01 (7) degrees, V = 1723 (4) A3, Z = 4, Dm(295 K, flotation) = 1.49, D chi(105 K) = 1.539 Mg m-3, mu(Mo K alpha) = 0.126 mm-1, F(000) = 836, m.p. (hot-stage microscope) 391-391.5 K, R = 0.033 for 6359 observed [I greater than or equal to 3.0 sigma(I)] reflections. The acetylcholine ion as well as the methoxycarbonylcholine ion have as first neighbours a great number of oxygen atoms. Contacts to the quaternary ammonium group do not seem to be more important than contacts to the acetyl or methoxy-carbonyl moieties. No direct contacts between aromatic rings and quaternary ammonium groups are found.

Acetylcholine↗
PubMed1981

The mechanism of uncoupling by picrate in Escherichia coli K-12 membrane systems.

The mechanism of action of the uncoupler picrate on intact cells and everted membrane vesicles of Escherichia coli K-12 was investigated. Like in mitochondria [Hanstein, W. G. and Hatefi, Y. (1974) Proc. Natl Acad. Sci. USA, 71, 288-292], it was observed that picrate uncoupled energy-linked functions only in everted, but not in intact membrane systems. In the vesicles picrate also decreased the magnitude of the transmembrane proton-motive force at concentrations similar to those at which it caused uncoupling. Experiments with 14C-labelled picrate showed that this compound bound both to deenergized intact cells and everted vesicles. However, upon energization of the membrane, picrate was extruded from the intact cell and taken up to a larger extent by the vesicles. These energy-dependent changes in picrate uptake correlated with the magnitude of the transmembrane electrical potential, delta psi. It is therefore proposed that picrate is a permeant uncoupler, that delta psi is the driving force for picrate movement across biological membranes, and that the uncoupling activity of picrate in everted membrane systems is due to its protonophoric action.

Adenosine Triphosphate↗
PubMed1990

Effect of glucose upon alkaline picrate: a Jaffé interference.

The reactivity of glucose in aqueous alkaline picrate was investigated by spectrophotometry and polarography at 25 degrees C in 0.51 mol/l sodium hydroxide. Thin-layer chromatography and infrared spectroscopy studies have conclusively identified the presence of picramic acid in 5:1 and 10:1 glucose picrate test solutions incubated at 25 degrees C. The polarographic data of an alkaline picrate blank with a concentration of 0.284 mmol/l, show three well-defined nitro group reduction waves with approximate half-wave potentials of -0.62 V, -0.78 V, and -0.93 V and a fourth broad wave appearing near -1.31 V versus a saturated calomel electrode. The addition of glucose to alkaline picrate resulted in a decreased diffusion current for reduction waves 1-3, with little change in reduction wave 4. The reactivity of test solutions containing glucose:picrate in 1:1, 2:1, 5:1 and 10:1 molar ratios was investigated at varied time intervals between 10 and 180 minutes. The absorption spectra of a 10:1 glucose:picrate solution shifted from 356 nm to 375 nm and a broad tailing shoulder absorbance formed in the 450-600 nm region. An orange coloured minor product, separated by thin-layer chromatography, was observed to fluoresce. The maximum excitation and emission wavelengths were 318 nm and 545 nm, respectively. A major, red-coloured product was isolated and identified as picramic acid by infrared spectroscopy. For 10:1 glucose:picrate test solutions incubated at 25 degrees C, picramic acid formed within 10 minutes. Within the first minute, the colour was observed to change from yellow to orange and then to red.

Chemical Phenomena↗
PubMed1984

Use-dependent block of GABA-activated chloride channels in crayfish muscle fibers by picrate.

In crayfish muscle fibers studied with intracellular microelectrodes the protein-binding agent, picrate (2,4,6-trinitrophenolate; 10(-5)-2 X 10(-4) M) was found to have a specific and dose-dependent inhibitory effect on the chloride conductance activated by bath-applied gamma-aminobutyric acid (GABA). A kinetic analysis showed that picrate did not interfere with GABA binding to its receptor. The blocking action of picrate was not increased by lowering the extracellular Cl- concentration which indicates that picrate is not likely to bind to the ionic selectivity site of the postsynaptic Cl- channel. In fibers first exposed to picrate (1-2 X 10(-4) M) and then, in the continuous presence of this drug, to GABA (5 X 10(-4) M), the latter induced a transient increase in the chloride conductance with an apparent rate constant of decay of about 40 sec. It is tentatively suggested that the site of action of picrate is a positively charged amino acid residue that is exposed through the action of GABA and critically involved in the chemical gating of the postsynaptic chloride channel.

Animals↗
PubMed1984

Reaction of picrate with creatinine and cepha antibiotics.

The concentration of creatinine in serum, which is used to estimate glomerular filtration rate, is measured by reaction with alkaline picrate, but this reaction is not specific for creatinine. Although several other cephalosporin antibiotics have been reported not to react with picrate, we reacted picrate with creatinine, cefoxitin, penicillin, and eight different cephalosporins, and found that all compounds reacted with picrate and showed superimposable spectrophotograms with absorption maxima at 485 nm. From these results we conclude that the color-absorbing moiety of the product is the picrate molecule. Further, the structure common to creatinine and the cephalosporins, cefoxitin, or penicillin is the carbonyl group attached to a nitrogen and a carbon atom. We postulate that the carbonyl group with the adjacent carbon and nitrogen atoms is probably the chemical moiety that reacts with picrate to absorb energy at 485 nm.

Cephalosporins↗
PubMed1988

Reactivity of acetoacetate with alkaline picrate: an interference of the Jaffé reaction.

Spectrophotometric, kinetic, and polarographic studies of the interaction of acetoacetate with alkaline picrate have been undertaken in the presence of aqueous NaOH concentrations ranging between 0.50 mol/L and 2.50 mol/L. Spectrophotometric data has substantiated formation of the following acetoacetate-picrate complexes: 1:1 red, 490 nm; 2:1 orange, 390 nm; and 3:1 colorless, 265 nm. Depending upon the time of measurement, the composition of alkaline picrate, and the acetoacetate level in the test samples, acetoacetate may be either a positive or negative interference in kinetic Jaffé methods for the determination of creatinine. Polarograms of alkaline picrate in 0.50 mol/L NaOH showed three well-defined nitro group reduction waves and a more diffuse fourth reduction wave with approximate half-wave potentials of -0.62 V, -0.79 V, -0.94 V, and -1.32 V, respectively. Increasing the concentration of hydroxide and/or acetoacetate resulted in the disappearance of reduction waves 1 to 3 with only reduction wave 4 remaining. Based upon the polarographic results, a trinitro anion structure has been assigned for the 2:1 acetoacetate-picrate complex.

Acetoacetates↗
PubMed1988

Picrate and niflumate block anion modulation of radioligand binding to the gamma-aminobutyric acid/benzodiazepine receptor complex.

The organic anions picrate (2,4,6-trinitrophenol) and niflumate (2-[[3-(trifluoromethyl)phenyl]-amino]-3-pyridinecarboxylate) were examined for their effects on radioligand binding to the gamma-aminobutyric acid (GABA)/benzodiazepine receptor complex. Neither organic anion produced the enhancement of [35S] t-butylbicyclophosphorothionate (TBPS) binding characteristic of anions (such as Cl- and Br-) known to permeate GABA-gated chloride channels. However, both picrate and niflumate potently (IC50 values between 66 and 531 and 30 and 155 microM, respectively) inhibited the effect of 100-200 mM concentrations of anions (I-, Br-, Cl-, SCN-, and F-) to increase the binding of [35S]TBPS to GABA-gated chloride channels. This inhibition resulted from a decrease in both the maximum number of binding sites and the apparent affinity (increased Kd) of [35S]TBPS. Niflumate was consistently more potent than picrate, but both organic anions exhibited the same sequence of relative potencies against smaller anions (I- greater than Br- greater than Cl- greater than SCN- greater than F-). This sequence was similar to that described for the relative permeabilities of these anions through GABA-gated chloride channels. Niflumate and picrate were potent inhibitors of Cl-, but not GABA-modulated radioligand binding to benzodiazepine receptors. These findings suggest that picrate and niflumate bind with high affinity at or near an anion binding site that may regulate the movement of anions through GABA-gated chloride channels and radioligand binding at this "supramolecular complex."

Animals↗
PubMed1986

Advantages of picrate fixation for staining polypeptides in polyacrylamide gels.

When acetic acid-urea polyacrylamide gels with or without Triton X-100 were immersed in 0.1 M Na picrate, pH 7, to which 1/4 vol Coomassie blue staining solution (0.2% in 45% methanol, 10% acetic acid, 45% water) was added, proteins stained rapidly (within a few minutes in gels without Triton and within an hour in gels with Triton) with little or no background staining. Thus protein bands could be observed in a single step with no destaining. The picrate-Coomassie blue method fixed and stained a small peptide (bradykinin, nine amino acids) that was not observed in gels stained with fast green, silver, or Coomassie blue following fixation in 50% trichloroacetic acid. The picrate-Coomassie blue method gave high-contrast bands suitable for densitometry. Gels containing sodium dodecyl sulfate were also stained by the picrate-Coomassie blue method if they were first washed briefly (1 h) in 45% methanol, 10% acetic acid, 45% water, presumably to remove the detergent. These gels also stained rapidly with almost no background.

Acrylic Resins↗
PubMed1978

Modification of the alkaline picrate assay for creatinine to prevent spuriously elevated values by keto acids.

Acetoacetate and pyruvate, sometimes present in patients' serum in abnormal amounts, interfere, like other keto acids, with the determination by some usual procedures of creatinine. Acetoacetate can be responsible for overestimation of "creatinine" in the order of 400 mumol/l in sera of ketotic diabetics, fasting subjects and other patients with ketosis. The pseudocreatinine reaction of acetoacetate increases with increasing concentration of NaOH and picrate. Pyruvate causes falsely elevated values, especially at high picrate concentrations. The effect of acetoacetate at 25 degrees C has ceased 90 sec after the start of the reaction. We propose a continuous flow method with relatively low concentrations of NaOH and picrate, and a kinetic method at 25 degrees C with a measuring time of between 90 and 270 sec after mixing sample and reagents. In this way the interference by acetoacetate and pyruvate is eliminated or reduced. We found excellent correlation between the proposed method for a centrifugal analyzer and a manual reference method, based on the adsorption of creatinine to fuller's earth.

Creatinine↗
PubMed1978

Specific method for serum creatinine determination based on ion exchange chromatography and an automated alkaline picrate reaction -- a proposed reference method.

A proposed reference method for serum creatinine has been developed under the auspices of the Committee on Reference Methods and Reference Materials of the Canadian Society of Clinical Chemists. A serum ultrafiltrate at pH 2.0 is applied through a closed sample loop injection system to a short column containing cationic resin of high resolving power. Elution with sodium citrate buffer by means of minipump at constant rate passes the eluate into alkaline picrate reagents in a continuous flow system (Technicon AAIII pump, AAII colorimeter 50 mm x 1.5 mm flow cell, narrow band width filter). The colour reaction peak is monitored visually to verify specificity and the area is calculated electronically. Specificity has been demonstrated by use of Jaffé-reactive substances such as glucose, sodium acetoacetate, L-ascorbic acid, pyruvic acid, L-dopa and glycocyamidine and also by use of an alternate colour reaction, sodium 3,5-dinitrobenzoate in place of alkaline picrate in the analysis of serum pools. Routine methods in common use, i.e., manual and automated alkaline picrate procedures, demonstrated a statistically significant high bias in interlaboratory studies in which this procedure was used for reference.

Autoanalysis↗
PubMed1990

Binding studies using ion-selective electrodes. Examination of the picrate-albumin interaction as a model system.

We are studying the binding of ligands to macromolecules by using ligand ion selective electrodes as transducers. The picrate-bovine albumin interaction is examined in detail as a model system. A picrate ion selective electrode is used to monitor the free picrate concentration directly in the presence of albumin and bound ligand. The binding parameters are estimated and the effect of protein concentration, ionic strength, pH, and temperature is studied. The experimental data are interpreted with a specially designed computer program that performs nonlinear least-squares fitting of the generalized Scatchard model with an infinite number of classes of binding sites directly to the raw potentiometric data. The binding parameters (binding constant and maximum number of ligands that can be bound), the nonspecific binding as well as their standard deviations are estimated by this program. The principles described can be used for the potentiometric study of any ligand-binder interaction.

Electrodes↗
PubMed1985

Characterization of creatinine error in ketotic patients. A prospective comparison of alkaline picrate methods with an enzymatic method.

Creatinine measurement by alkaline picrate reagents is subject to positive interference by acetoacetate. Enzymatic reagents avoid this interference and have been adapted to instruments such as the Ektachem-400 (Kodak). By documenting the discrepancy between alkaline picrate and Ektachem determinations for creatinine, the authors prospectively identified ketotic patients in whom the presence of ketones was responsible for a significant creatinine error. During their three-month survey, they identified 50 such ketotic inpatients. Those admitted to the medicine service represented almost 5% of all medicine admissions over this time. Of the total specimens, the mean discrepancy was 14 +/- 8 mg/L with a range of 4-44 mg/L. The greater the ketosis, the greater the discrepancy. Two-thirds of the samples were normal on the Ektachem but greater than normal by picrate methods. In addition to diabetes or ethanol abuse, 17% of the ketotic patients had severe or terminal illness that was generally associated with malnutrition.

Acetoacetates↗
PubMed1991

Dipotassium and sodium/potassium crystalline picrate complexes with the crown ether 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]-[1,4, 7,10,13,16,19,22]octaoxacyclotetracosin (dibenzo-24-crown-8).

The crystal structures of the dipotassium and the mixed sodium/potassium picrate complexes with the crown ether dibenzo-24-crown-8 (DB24C8) were solved and found to be nearly identical. (I): NaK-pic2(DB24C8), [NaK(C6H2N3O7)2(C24H32O8)]. Mr = 966.8, triclinic, P1, a = 8.164 (2), b = 9.960 (2), c = 13.368 (3) A, alpha = 103.92 (3), beta = 108.03 (2), gamma = 93.23 (2) degrees, V = 993.0 (7) A3, Z = 1, Dm = 1.54 (T = 298 K). Dx = 1.62 (1) g cm-3, lambda = (Mo K alpha) 0.71069 A, mu = 2.37 cm-1, F(000) = 500, T = 103 K, R = 0.086 for 2904 unique reflections. (II): K2pic2(DB24C8), [K2(C6H2N3O7)2(C24H32O8)]. Mr = 982.9, triclinic, P1, a = 8.231 (4), b = 9.850 (2), c = 13.346 (4) A, alpha = 103.91 (2), beta = 106.82 (3), gamma = 93.37 (2) degrees, V = 995.7 (9) A3, Z = 1, Dm = 1.59 (T = 298 K), Dx = 1.638 (8) g cm-3, lambda (Mo K alpha) = 0.71069 A, mu = 3.30 cm-1, F(000) = 508, T = 163 K, R = 0.042 for 4835 unique reflections. Both structures feature eight-coordinated cations between alternating layers of relatively flat crown ligands and paired picrates. In the mixed-metal system the two cations are disordered between two P1-related sites; these metal sites have a coordination environment only slightly different from that in the dipotassium structure. Na+ is able to occupy an environment similar to that of K+ under the conditions of these crystals, a situation not previously observed in the chemistry of crown ethers or macrocylic multidentates.

Chelating Agents↗
PubMed1970

Crystal structure of serotonin picrate, a donor-acceptor complex.

The crystal structure of the red picric acid salt of serotonin was determined by x-ray diffraction methods. The structure consists of parallel hydroxyindole and picrate planes which are intimately stacked with an interplanar separation of 3.3 to 3.4 angstroms. The stacking interaction appears to be of the donor-acceptor (charge-transfer) type, involving specific contacts between picrate nitro groups and atoms of the hydroxyindole moieties. Similar interactions might mediate biological processes involving serotonin.

Electron Transport↗
PubMed1981

Kinetic potentiometric determination of creatinine in serum with a picrate ion-selective membrane electrode.

We describe a new kinetic method for potentiometric determination of creatinine in serum, based on the creatinine--picrate reaction in alkaline medium (Jaffé reaction). The reaction is monitored with a picrate-selective electrode, and the increase in electrode potential during 270 s is measured and related directly to the creatinine concentration. Small cation-exchange columns are used to separate creatinine from interfering substances. Analytical recovery of creatinine added to serum was 100.7%. Results for a series of samples compared well with results obtained with a spectrophotometric method (r = 0.994).

Creatinine↗
PubMed1978

[Effect of selective application of sodium picrate to the hypogastric ganglion in the hypogastric nerve-vas deferens preparation of the guinea pig (author's transl)].

Effect of sodium picrate (picric acid-Na; PA) on the hypogastric ganglion in the hypogastric nerve-vas deferens preparation of the guinea pig was studied and the results are as follows: PA or acetylcholine (ACh) at doses (g/ml) of 10(-5) approximately 10(-4) applied to the ganglion increased the height of the response (R-NS) of the vas deferens to the hypogastric nerve stimulation. Neither drug restored R-NS blocked by hexamethonium 3 X 10(-5). Effects of PA and ACh on R-NS were potentiated by neostigmine 10(-7) and the potentiation was considerably greater for ACh than for PA. Effects of PA on R-NS were not influenced by pretreatment with atropine. Both PA and ACh recovered R-NS which was partially reduced by hemicholinium-3 (HC-3), although the recovery of R-NS by PA was rapidly abolished more than that by ACh when these drugs were repeatedly applied in the presence of HC-3 3 X 10(-5). PA markedly recovered the R-NS reduced by morphine 10(-4) and ACh slightly restored that R-NS. These results suggest that the site of action of PA on the hypogastric ganglion of the guinea pig is different from that of ACh and the effect of PA on R-NS may be due to the acceleration of ACh-release from preganglionic nerve endings.

Acetylcholine↗
PubMed1976

Reaction of alkaline sodium picrate with creatinine: I. Kinetics and mechanism of formation of the mono-creatinine picric acid complex.

Spectrophotometric, kinetic, and nuclear magnetic resonance studies indicate that alkaline sodium picrate and creatinine react to form a 1/1 aduct between picric and creatinine, with a stability constant of log K= 4.26. Kinetic studies indicate that the forward reaction is first order with respect to picric acid, hydroxide, and creatinine concentration. The reverse reaction, the dissociation of the 1/1 complex, shows a complex dependence on hydroxide concentration. The expression for the observed pseudo-first-order rate constant in the presence of excess picric acid is: Kobsd = K1K0[P][OH] +[K2[OH]x. A value of K1K0 = 5.0 (mol/liter)-2s-1 is obtained. For accurate analytical results with this reaction, hydroxide concentration must be maintained at a constant value for both samples and standards.

Chemical Phenomena↗