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PubMed2001

Electrophoretically mediated microanalysis with small molecules: the Jaffé method for creatinine carried out in a capillary tube.

An eletrophoretically mediated microanalysis (EMMA) approach, used to perform online chemistry between two small molecules, has been characterized and optimized. The "plug-plug" type EMMA method involved electrophoretic mixing and subsequent reaction of nanoliter plugs of creatinine-containing samples and alkaline picrate (Jaffe reaction) within the confines of the capillary column, which acts as a microreactor. Analyses were performed by pressure injecting a plug of picrate followed by a plug of the creatinine-containing sample. A potential was then applied to electrophoretically mix the two reactants, and an incubation time of up to 6 min allowed the reaction to proceed prior to the application of a 27 kV separation potential with absorbance detection at 485 nm. The use of a 50 microm inner diameter(ID) extended light path capillary (150 microm pathlength) was found to be adequate for determining elevated levels of creatinine in human blood sera, but could not be used to quantify normal levels. Quantification of both normal and elevated levels of creatinine in sera was possible with a 75 microm ID high-sensitivity cell (1200 microm pathlength). Calibration plots using the latter for creatinine in human blood sera spanned the expected clinical range and were linear between 40 microM and 1.2 mM (r2 = 0.996) with an estimated limit of detection of 17 microM (signal-to-noise ratio S/N = 3). A quantitative comparison of results obtained with the reported EMMA method and accepted clinical methodology correlated very well (slope = 1.001).

Artifacts↗

PubMed2005

Synthesis and infrared and luminescence spectra of rare earth complexes with a new hexapodal ligand.

Solid complexes of rare earth nitrates and picrates with a new hexapodal ligand, 1,2,3,4,5,6-hexa{[(2'-benzylamino-formyl)phenoxyl]methyl}-benzene (L) have been prepared. These complexes were characterized by elemental analysis, IR and molar conductivity. At the same time, the luminescence properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of europium and terbium ions. The influence of the counter anion on the luminescent intensity was also discussed.

Benzamides↗

PubMed2006

Synthesis and infrared and fluorescent properties of rare earth complexes with a new aryl amide podand.

Solid complexes of rare earth nitrates and picrates with a new aryl amide podand, 1,4-bis{[(2'-benzylamino-formyl)phenoxyl]methyl}-naphthaline (L) were synthesized. The complexes were characterized by elemental analysis, IR and molar conductivity measurements. At the same time, the fluorescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated. Under the excitation, these complexes exhibited characteristic emissions of europium and terbium ions. The counter anion factor influencing the fluorescent intensity was also discussed.

Benzyl Compounds↗

PubMed1986

A general method for the assay of binders. Application to the potentiometric determination of albumin in human serum, plasma and whole blood.

From the generalized theory of binding (stepwise equilibrium model, Scatchard model) it can be derived that in a solution containing the binder and a specific ligand, the bound ligand concentration is linearly related to the total binder concentration only if the free ligand concentration is constant. We designed a general method which is based on that principle and we have shown its validity for the albumin assay in serum, plasma and whole blood. We have tested the ligands bromcresol purple and picrate and used ligand-ion selective electrodes to monitor free ligand concentration in a homogeneous solution. The method has excellent linearity. We chose picrate (PIC) as ligand, because of better specificity. Comparison with the bromcresol purple (BCP) and bromcresol green (BCG) spectrophotometric procedures for 93 samples gave the regression equations: y(PIC) = 0.98x(BCP) + 0.76 (g/L, r = 0.979) and y(PIC) = 0.95x(BCG) - 1.3 (r = 0.947), respectively. Within-day and day-to-day precision was up to 1.5% and 2.3%, respectively. Results for albumin in plasma, when transformed to expected whole blood values, were in close agreement with those obtained by direct analysis of whole blood (in the presence of erythrocytes).

Bromcresol Green↗

PubMed1976

Transport of pyruvate nad lactate into human erythrocytes. Evidence for the involvement of the chloride carrier and a chloride-independent carrier.

The kinetics and activation energy of entry of pyruvate and lactate into the erythrocyte were studied at concentrations below 4 and 15mM respectively. The Km and Vmax. values for both substrates are reported, and it is shown that pyruvate inhibits competitively with respect to lactate and vice versa. In both cases the Km for the carboxylate as a substrate was the same as its Ki as an inhibitor. Alpha-Cyano-4-hydroxycinnamate and its analogues inhibited the uptake of both lactate and pyruvate competitively. Inhibition was also produced by treatment of cells with fluorodinitrobenzene but not with the thiol reagents or Pronase. At high concentrations of pyruvate or lactate (20mM), uptake of the carboxylate was accompanied by an efflux of Cl-ions. This efflux of Cl- was inhibited by alpha-cyano-4-hydroxycinnamate and picrate and could be totally abolished by very low (less than 10 muM) concentrations of the inhibitor of Cl- transport, 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid. This inhibitor titrated out the chlordie efflux induced by pyruvate, bicarbonate, formate and fluoride, in each case total inhibition becoming apparent when approximately 1.2x10(6) molecules of inhibitor were present per erythrocyte, that is, about one inhibitor molecule per molecule of the Cl- carrier. Evan when Cl- efflux was totally blocked pyruvate and lactate uptake occurred. Kinetic evidence is presented which suggests that the Cl- carrier can transport pyruvate and lactate with a high Km and high Vmax., but that an additional carrier with a low Km and a low Vmax. also exists. This carrier catalyses the exchange of small carboxylate anions with intracellular lactate, is competitively inhibited by alpha-cyano-4-hydroxycinnamate and non-competitively inhibited by picrate. The Cl- carrier shows a reverse pattern of inhibition. It is concluded that net efflux of lactic acid from the cell must occur on the Cl- carrier and involve exchange with HCO3 - followed by loss of CO2. The low Km carrier might be used in pyruvate/lactate or acetoacetate/beta-hydroxybutyrate exchanges involved in transferring reducing power across the cell membrane. The possibility that the Cl- carrier exists in cells other than the erythrocyte is discussed. It is concluded that its presence in other cell membranes together with a low intracellular Cl- concentration would explain why the pH in the cytoplasm is lower than that of the blood, and why permeable carboxylate anions do not accumulate within the cell when added from outside.

Biological Transport, Active↗

PubMed1999

Glomerular filtration rate estimation from plasma creatinine after inhibition of tubular secretion: relevance of the creatinine assay.

BACKGROUND: Estimation of glomerular filtration rate (GFR) from plasma creatinine concentration after inhibition of tubular creatinine secretion with cimetidine provides a good assessment in patients with various nephropathies and with non-insulin-dependent diabetes mellitus (NIDDM). The aim of this study was to compare cimetidine-aided GFR estimations using various creatinine assays. METHODS: In 30 outpatients with NIDDM GFR was measured as the urinary clearance of continuously infused [125I]iothalamate. Plasma creatinine concentration was analysed after oral cimetidine with an alkaline picrate (AP) method, with an enzymatic (PAP) assay and with HPLC. GFR estimations were calculated with the Cockcroft Gault formula (CG). RESULTS: AP creatinine concentrations were significantly higher than PAP or HPLC values. GFR estimations by AP (CG(AP) 66 +/- 19 ml/min/1.73 m2, mean SD) were significantly lower than GFR (89 +/- 30), whereas CG(PAP) (85 +/- 30) and CG(HPLC) (84 +/- 34 ml/min/1.73 m2) were not. Bland and Altman analysis showed a difference between CG(AP) and GFR of -22.4 +/- 17.7 ml/min/1.73 m2; this difference becomes larger when the GFR increases. The difference between CG and GFR was only -3.8 +/- 14.8 ml/min/1.73 m2 for PAP and -4.4 +/- 17.5 ml/min/1.73 m2 for HPLC, without any systematic difference. CONCLUSION: A good assessment of the GFR from plasma creatinine after cimetidine administration is possible when creatinine is measured with an enzymatic assay or with the less convenient HPLC method. The more widespread and cheaper alkaline picrate assay is not suitable for GFR-estimation.

Adult↗

PubMed1984

Use of [3H]triphenylmethylphosphonium cation for estimating membrane potential in neuroblastoma cells.

The lipophilic permeant cation [3H]triphenylmethylphosphonium (TPMP) was used to estimate membrane potential in neuroblastoma N1E 115 cells under carefully controlled conditions. The cation distributes into the cells only in the presence of a lipophilic anion, and tetraphenylboron and picrate have been used for this purpose. The potassium salt of tetraphenylboron is poorly soluble, so that studies in high [K+] media are difficult with this anion whereas picrate, at the concentrations required, hyperpolarises the cells. The effect of muscarinic receptor activation was investigated by treating cells with carbachol but no effect was seen either on [3H] TPMP distribution or electrophysiological parameters. The use of [3H]TPMP for qualitative and quantitative evaluation of membrane potential in these cells is discussed.

Animals↗

PubMed1976

[Effect of valinomycin on the structure of water-lecithin liposomes].

It has been established that water--lecithin liposomes in the heptane phase are formed in the course of equilibration of lecithin solution in heptane with water phase containing Na, K-picrate. The salts penetrate both the water nucleus of liposomes and their lecithin shell. The addition of valinomycin to this system does not change the water content in liposomes, but considerably increases the salt absorbed by the lipid shell of liposomes. A characteristic S-shape curve showing the relation between picrate extraction and the valinomycin concentration might be explained as an indication of a cooperative change of the structure of lecithin shell. This phase transition is induced by one valinomycin molecule per 10(3)--10(4) lecithin molecules.

Liposomes↗

PubMed1992

High-performance liquid-chromatographic measurement of plasma creatinine in newborns.

This HPLC method for measuring plasma creatinine is based on cation-exchange chromatography and is particularly suitable for use with specimens from babies. A short chromatographic run is performed after simple protein precipitation with zinc sulfate and addition of an internal standard, N-methylnicotinamide. The standard curve for the method is linear up to 200 mumol/L, and analytical recovery of added creatinine is between 101% and 103%. Between-batch precision (CV) is less than 3% for mean creatinine values of 103 and 164 mumol/L. The method is free of interference from other metabolic components and drugs commonly used in neonates in routine clinical practice. Using specimens from neonates, I compared this method with a routinely used automated alkaline picrate method (from Randox Labs., performed on a Cobas MIRA analyzer). Linear-regression analysis yielded a correlation coefficient of 0.90, a slope of 1.00, and an intercept of +0.8 mumol/L. This HPLC method for creatinine should be of use in those circumstances where the alkaline picrate method is known to produce dubious results; however, the latter method is probably more suitable for routine use.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

An evaluation of the advantages and effectiveness of picric acid monitoring during solid phase peptide synthesis.

The effectiveness of picric acid for the monitoring of coupling completion during solid phase peptide synthesis was evaluated. Each coupling step was monitored during the synthesis of 124 peptides by the method of simultaneous multiple peptide synthesis. Of the peptides tested (1622 picrate determinations), approximately 10% underwent a single low yield step, another 10% had 2 or 3 consecutive low yield steps and about 20% contained "humps" 4 to 8 steps long. In virtually all instances, the low yield steps occurred only at or after coupling step 7. High picrate values obtained after incorporation of methionine appear to be caused by a sulfonium salt in the side chain of methionine. Differences in average reactivities of amino acids correlated with structural elements of their side chains. Picric acid, which is currently seldom used for monitoring of coupling completion during solid phase peptide synthesis, was found to be straightforward and nondestructive. While picric acid monitoring is not as sensitive as the more commonly used ninhydrin method, it yields information which is not detectable with the use of ninhydrin and is clearly superior for certain applications and investigations.

Amino Acid Sequence↗

PubMed1987

Kinetic study of the Jaffé reaction for quantifying creatinine in serum: 1. Alkalinity controlled with NaOH.

We studied the kinetic behavior of the reaction of alkaline picrate and creatinine and evaluated a nonlinear curve-fitting method for quantifying creatinine in serum. Using a 3 X 3 factorial experimental design, we evaluated interactive effects among temperature and concentrations of creatinine, picrate, and NaOH. We found no evidence of interference by glucose or unconjugated bilirubin; the effects of the acetoacetate reaction, which is fast, are easily compensated by the curve-fitting method. The reaction with human serum albumin is very complex, but its effects are compensated by the curve-fitting method and by preparing standards containing 50 g of albumin per liter. Calibration plots are linear under a wide variety of conditions for both aqueous standards and standard additions of creatinine to pooled serum. Reproducibility studies with standards containing creatinine at 2, 10, and 20 mg/L yielded relative standard deviations (RSD) of 8.2, 2.5, and 1.3%, corresponding to absolute variations of 0.16, 0.25, and 0.26 mg/L. The average SD for 17 sera containing creatinine at 15-50 mg/L was 0.7 mg/L. The averages of ratios (as percent) of determined vs expected concentrations in 17 sera with added creatinine (7.27 mg/L) were 97.8% for aqueous standards, 99.9% for standards with added albumin.

Acetoacetates↗

PubMed1996

[Validation and study of the transferability of the selected technique by SFBC for the determination of creatinine in plasma].

A selected method for the determination of creatinine in plasma, using the reaction with alkaline picrate without prior pretreatment has been proposed by the Commission 'Validation de techniques' in the SFBC (Société Française de biologie clinique). The transferability step was conducted in seven laboratories, equipped with different automatic analyzers, using analytical procedures derived from the recommended method. Its goal was to test whether the original analytical performances could be maintained and consistent results obtained. The validation step was designed to evaluate the linearity limits of the analytical range, the detection limit, to assess accuracy as compared to a high performance liquid chromatography and to investigate the effect of the main interferents. Linearity limits are 15 and 2000 mumol/L. The detection limit is 3 to 8 mumol/L according to the analytical systems. The selected method can fulfil the set imprecision goals: intralaboratory CV minus than 2% (within-run), minus than 4% (run-to-run), interlaboratory CV minus than 5% (for 100 mumol/L creatinine). Inaccuracy evaluated for the chosen control sera is 1 to 15% as compared to the chromatographic method, according to the sera and to the analytical systems. The results obtained with the selected method are more consistent with the HPLC than are those obtained with an alkaline picrate method without SDS or with an enzymatic method. No interference could be demonstrated for acetoacetate (up to 8 mmol/L), hemoglobin (up to 210 mumol/L), unconjugated bilirubin (up to 250 mumol/L), glucose (up to 30 mmol/L), IgG (up to 45 g/L), albumin (up to 60 g/L). The effect of cephalosporins depends on the molecule. The reagents are stable for at least 6 months when stored in closed vials at +20 degrees C. The alkaline reagent is stable 30 days at +4 degrees C. Reference limits (0.025 and 0.975 fractiles) have been established for healthy adults. They are respectively 73 to 126 mumol/L for men and 59 to 100 mumol/L for females.

Adult↗

PubMed2004

Using diffusion NMR to characterize guanosine self-association: insights into structure and mechanism.

This paper presents results from a series of pulsed field gradient (PFG) NMR studies on lipophilic guanosine nucleosides that undergo cation-templated assembly in organic solvents. The use of PFG-NMR to measure diffusion coefficients for the different aggregates allowed us to observe the influences of cation, solvent and anion on the self-assembly process. Three case studies are presented. In the first study, diffusion NMR confirmed formation of a hexadecameric G-quadruplex [G 1](16)4 K(+)4 pic(-) in CD(3)CN. Furthermore, hexadecamer formation from 5'-TBDMS-2',3'-isopropylidene G 1 and K(+) picrate was shown to be a cooperative process in CD(3)CN. In the second study, diffusion NMR studies on 5'-(3,5-bis(methoxy)benzoyl)-2',3'-isopropylidene G 4 showed that hierarchical self-association of G(8)-octamers is controlled by the K(+) cation. Evidence for formation of both discrete G(8)-octamers and G(16)-hexadecamers in CD(2)Cl(2) was obtained. The position of this octamer-hexadecamer equilibrium was shown to depend on the K(+) concentration. In the third case, diffusion NMR was used to determine the size of a guanosine self-assembly where NMR signal integration was ambiguous. Thus, both diffusion NMR and ESI-MS show that 5'-O-acetyl-2',3'-O-isopropylidene G 7 and Na(+) picrate form a doubly charged octamer [G 7](8)2 Na(+)2 pic(-) 9 in CD(2)Cl(2). The anion's role in stabilizing this particular complex is discussed. In all three cases the information gained from the diffusion NMR technique enabled us to better understand the self-assembly processes, especially regarding the roles of cation, anion and solvent.

Circular Dichroism↗

PubMed2004

Metal ion-binding ability of tetrapeptides containing alpha-aminoisobutyric acid.

alpha-Aminoisobutyric acid (Aib), one of the Calpha,alpha-disubstituted glycines, is a sterically hindered amino acid that acts as a conformational constraint in peptides. However, studies for the application of the ability of Aib to control conformation are quite few. The paper focuses on the molecular recognition ability of acyclic oligopeptides containing Aib. Liquid-liquid extraction of nine kinds of metal ions from aqueous layers to nonpolar organic layers with acyclic tetrapeptides, X-Trp-Xaa2-Gly-Xaa4-NH-Ar (X = H or C6H5CH2OCO (Z), Xaa2 = Aib or Gly, Xaa4 = Leu or Ala, Ar = phenyl or 3,5-dimethylphenyl) was examined using picrate as the anion of ion pairs. The extraction behaviour of the metal ions with the tetrapeptides was investigated in the pH range from 3 to 9. In the case of basic pH regions, Cu(II) and Ag(I) were effectively extracted with Trp-Aib-Gly-Leu-NH-Ar. Pd(II) was specifically extracted with Trp-Aib-Gly-Leu-NH-Ar in acidic pH regions. The extraction percent (%E) of the peptide host, which has a 3,5-dimethylphenyl group, was even larger than that of the host, which has a phenyl group. Moreover, Pd(II) was extracted with a peptide host which has Leu and a 3,5-dimethylphenyl group in the absence of picrate as the anion of ion pairs. The free alpha-amino group, the turn conformation and the hydrophobicity of peptide molecules were important factors for the extraction of the metals.

Aminoisobutyric Acids↗

PubMed1987

Polarographic determination of extraction constants.

The extraction constant of three organic compounds containing nitrogen as a picrate ion pair in a water-chloroform system were determined by following polarographically the picrate concentration in the aqueous phase as a function of the added amount of reagent. The extraction constants were also determined spectrophotometrically (via batch extraction). The obtained results are in good agreement. The proposed method is applicable for extraction constants with values between 10(3) and 10(9).

Ions↗

PubMed1978

Selective ion binding and membrane activity of synthetic cyclopeptides.

Four cyclic peptides related to the membrane-active complexones PV, cyclo-(L-Pro-Lval-D-Pro-D-Val)3, and valinomycin were synthesized: (1) cyclo-(L-Pro-L-Ala-D-Val)3 or PVPA, (2) cyclo-(L-Ala-L-Val-D-Pro-D-Val)3 or PVAV, (3) cyclo-(L-Pro-L-Val-D-Pro-D-Val)2-L-Pro-D-Val or PV-10, (4) cyclo-(L-Pro-L-Val-D-Pro-D-Val)2 or PV-8. In a two-phase extraction assay the affinity of PV and PVPA for alkali picrates was about three orders or magnitude greater than that of valinomycin. It was about equal to valinomycin for PVAV and much lower for PV-10 and PV-8. PV, PVPA and PVAV showed a selectivity sequence similar to that of valinomycin, namely K+ approximately Rb+ greater than Cs+ greater than Na+ greater than Li+. In the series PV, PV-10, PV-, the preference for K+ over Na+ was 700, 5 and less than 1, respectively. Thus, it was possible to reverse the selectivity of PV for K+ over Na+ by reducing the ring size from 12 to 8 amino acid residues. In sheep red cell lipid bilayer membranes PVPA increased the membrane conductance significantly in the presence of either KCl or NaCl but it was less potent than PV. PV-10, PV-8 and PVAV on the other hand were ineffective in this assay. The inactivity of PVAV as a potassium carrier in membrane was in contrast to its high affinity for potassium picrate in two-phase assays. Such a behaviour may be observed of a compound that has too low an aqueous cation binding constant to use the solution-complexation mechanism of PV (Davis et al. (1976) Biochemistry 15, 768--774 and Pinkerton et al. (1969) Biochem. Biophys. Res. Commun. 35, 512--518) and too slow binding and release kinetics to use the interfacial-complexation mechanism of valinomycin.

Cations, Monovalent↗

PubMed1978

A selective method for determination of methylguanidine in biological fluids. Its application in normal subjects and uremic patients.

A selective analytical method for the determination of methylguanidine in plasma in biological fluids has been developed. Methylguanidine is extracted in a column to dichloromethane as an ion pair with hexanitrodiphenylamine (dipicrylamine). It is isolated from coextracted compounds by partition chromatography as the picrate ion-pair. The methylguanidine fraction is collected and after reextraction to a buffer solution the methylguanidine content is quantitatively determined photometrically as picrate. An absolute recovery of 95 +/- 5% was obtained in the concentration range 1.5-10 microgram/ml plasma. The concentration of methylguanidine in plasma was higher in uremic patients, (44.4 +/- 5.71 mumol/l in conservatively-treated and 42.4 +/- 7.87 mumol/l in dialysis-treated patients) than in normal subjects, (4.0 mumol/l), but still lower than reported by other investigators using non-specific methods and also lower than the concentrations found to be toxic in experimental animals. There was a significant correlation between methylguanidine and creatinine concentration but no correlation between methylguanidine and urea concentration in plasma. No obvious relation was found between plasma methylguanidine concentration and various uremic symptoms, mode of treatment or protein intake.

Creatinine↗

PubMed1993

A benzopyrylium dye as a novel effective cationic uncoupler of oxidative phosphorylation.

Benzopyrylium dye BDBP was found to be an effective uncoupler of oxidative phosphorylation. It stimulates state 4 respiration of mitochondria 2-fold at about 2 microM, reveals a maximum stimulation (8-fold) at 30 microM and inhibits the respiration at higher concentrations. BDBP is also an effective proton (hydroxyl) carrier through bilayer lipid membranes (BLM) as is seen from the electrical properties of BLM with BDBP. Picrate enhances the effects of BDBP on the mitochondrial respiration and BLM conductance. The BDBP activities are accounted for by formation of dimers and complexes with picrate.

Animals↗