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At least 19 recordsLinked to original sources

PubMed1996

Synthesis of a Heteroditopic Cryptand Capable of Imposing a Distorted Coordination Geometry onto Cu(II): Crystal Structures of the Cryptand (L), [Cu(L)(CN)](picrate), and [Cu(L)(NCS)](picrate) and Spectroscopic Studies of the Cu(II) Complexes.

The synthesis of a new macrobicyclic cryptand (L) with heteroditopic receptor sites has been achieved in good yields by the [1 + 1] Schiff base condensation of tris(2-aminoethyl)amine (tren) with the tripodal trialdehyde, tris{[2-(3-(oxomethyl)phenyl)oxy]ethyl}amine at 5 degrees C temperature. The crystal structure of L (P2(1)/c, a = 10.756 (5) Å, b = 27.407(9) Å, c = 12.000(2) Å, beta = 116.22(3) degrees, Z = 4, R = 0.060, R(w) = 0.058) shows a pseudo-3-fold symmetry axis passing through the two bridgehead nitrogens. This symmetry is maintained in chloroform solution also, as indicated from its (1)H-NMR spectral data. The cryptand readily forms inclusion complexes with the Cu(II) ion at the tren end of the cavity. The tetracoordinated Cu(II) cryptate (1) thus formed with Cu(picrate)(2) exhibits a very small A(II) value (60 x 10(-)(4) cm(-)(1)) in its EPR spectrum and low-energy ligand field bands in its electronic spectrum in MeCN at room temperature. The bound Cu(II) ion readily accepts the anions CN(-), SCN(-), or N(3)(-), forming distorted trigonal bipyramidal complexes (2-4). The crystal structure of [Cu(L)(CN)](picrate) (2) (P2(1)/C, a = 13.099(1) Å, b = 11.847(8) Å, c = 25.844(7) Å, beta = 91.22(1) degrees, Z = 4, R = 0.056, R(w) = 0.054) has been determined. The equatorial coordination is provided by the three secondary amino N atoms of the tren unit in L, while the two axial positions are occupied by the bridgehead N of the tren unit and the C atom of the cyanide group. One of the equatorial Cu-N bond distances is 2.339(6) Å, which is longer than normal values. The crystal structure of [Cu(L)(NCS)](picrate) (3) (C2/c, a = 47.889(10) Å, b = 10.467(5) Å, c = 16.922(2) Å, beta = 93.90(2) degrees, Z = 8, R = 0.054, R(w) = 0.055) shows the coordination geometry around the Cu(II) ion to be very similar to that in the case of 2. The electronic spectral and EPR spectral data obtained on 2-4 are characteristic of trigonal bipyramidal Cu(II) complexes. The three meta-substituted benzene rings present in L makes the donor atom somewhat rigid in nature which enforces a distorted geometry around the Cu(II) ion.

Journal Article↗

PubMed2006

L-prolinium picrate and 2-methylpyridinium picrate.

In the structure of L-prolinium picrate, C5H10NO2+.C6H2N3O7-, the Cgamma atom of the pyrrolidine ring has conformational disorder. Both the major and minor conformers of the pyrrolidine ring adopt conformations intermediate between a half-chair and an envelope. Both the cation and anion are packed through chelated three-centred N-H...O hydrogen bonds. The prolinium cation connects two different picrate anions, leading to an infinite chain running along the b axis. In 2-methylpyridinium picrate, C6H8N+.C6H2N3O7-, the cations and anions are packed separately along the a axis and are interconnected by N-H...O hydrogen bonds. Intramolecular contacts between phenolate O atoms and adjacent nitro groups are identified in both structures. A graph-set motif of R1(2)(6) is observed in both structures.

Journal Article↗

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↗

PubMed2004

New highly selective picrate sensors based on charge-transfer complexes.

Two novel highly selective potentiometric membrane sensors responsive to picrate ion were developed. They are based on the use of N,N'-dibenzoyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DD18C6)-picrate and Kryptofix 222-picrate charge-transfer complexes as novel electroactive materials in poly(vinyl chloride) matrix membranes plasticized with o-nitrophenyloctylether or dioctylphthalate. The sensors show a Nernstian response with anionic slopes of -59.0 +/- 0.1 and -58.0 +/- 0.2 mV decade(-1) over concentration ranges of 6.0 x 10(-5) - 1.0 x 10(-2) and 7.0 x 10(-5) - 1.0 x 10(-2) mol l(-1) picrate ion and pH ranges of 5-11.5 and 5.5-11.5 for DD18C6 and Kryptofix 222 based picrate sensors, respectively. Both sensors show highly selectivity towards picrate ion over many hydrophilic and lipophilic anions, and exhibit a non-Hofmeister selectivity sequence, which is an improvement over methods reported so far. The sensors are used for the titrimetric determination of alkaloids using picrate as a titrant.

Journal Article↗

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↗

PubMed2006

Spectral investigations of amino acid picrates.

FTIR and laser Raman spectra of beta-alanine beta-alaninium picrate and dl-phenylalanine dl-phenylalaninium picrate crystals of space group P1 (C(i)) have been me in the 4000-50 cm(-1) range, at room temperature. The former crystal consists of beta-alanine beta-alaninium and the later dl-phenylalanine dl-phenylalaninium as cations. The presence of both carbonyl (CO) and carboxylate COO(-) groups in these crystals is the evidence for the existence of the zwitterion and the protonated forms. Factor group analysis has been made and the numbers of vibrational modes have been calculated. The tentative assignments of the observed bands are given. Fermi resonance has also been observed in one of the crystal beta-alanine beta-alaninium picrate. The picrate group forms the anion in both crystals and the characteristic bands nu(as)NO(2), nu(s)NO(2), and nu(phen)C-O stretching are observed in the spectra. These suggest that the picrate ion is unaffected by the presence of the cations.

Alanine↗

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↗

PubMed2005

Thermal hazard of iron picrate.

Iron picrate (FePic) was synthesized under conditions similar to those that result in the natural deterioration of chemical weapons. Its thermal hazard was investigated by comparing it with iron picrate obtained by the chemical synthesis method (FePic(Ba)). FePic has eight or more water molecules of crystallization and consists of a mixture of various hydrates. It shows low sensitivity to friction and drop hammer tests due to the large number of water molecules of crystallization. Under the experimental conditions of the thermal analysis, the hydrated iron picrates began to decompose before being dehydrated to form the anhydrous salt. Prolonged holding under natural environmental conditions does not appear to result in formation of the dangerous anhydrous salt. Based on the observed heating rate dependence, it is thought that the hydrated iron picrate should start to decompose before dehydration to the anhydrous salt occurs when subjected to a large heating rate.

Barium↗

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↗

PubMed2006

Vibrational spectral analysis of DL-valine DL-valinium and DL-methionine DL-methioninium picrates.

A comparative study of infrared and Raman spectra of DL-valine DL-valinium picrate (DL-VVP) and DL-methionine DL-methioninium picrate (DL-MMP) at the room temperature in 4000-50 cm(-1) range helps to determine the effect of hydrogen bonds in these crystals. The existence of the zwitterion and the protonated form in both the crystals has been observed. In DL-MMP, the methionine and the methioninium residues form a dimer through a strong hydrogen bond between them in the crystal. The characteristic bands due to gem-methyl group are observed in the case of DL-VVP. Factor group analysis has been made and the numbers of vibrational modes have been calculated. The tentative assignments of the observed bands are given. The picrate group forms the anion in both the crystals and it is unaffected by the presence of the cations.

Hydrogen Bonding↗

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↗