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Using platinum plate coated with PVC membrane as indicator electrode, amitriptyline hydrochloride was titrated with sodium tetraphenylborate by zero-current oscillo-potentiometry titration and zero-current oscillo-bipotentiometric titration. Both methods are precise, audio-visual, simple and convenient and can be used in the determination of other medicines.
The kinetics of light-driven electron flow and the nature of redox centers at apparent photosynthetic membrane growth initiation sites in Rhodopseudomans sphaeroides were compared to those of intracytoplasmic photosynthetic membranes. In sucrose gradients, these membrane growth sites sediment more slowly than intracytoplasmic membrane-derived chromatophores and form an upper pigmented band. Cytochromes c1, c2, b561, and b566 were demonstrated in the upper fraction by redox potentiometry; c-type cytochromes were also detected electrophoretically. Signals characteristic of light-induced reaction center bacteriochlorophyll triplet and photooxidized reaction center bacteriochlorophyll dimer states were observed by EPR spectroscopy but the Rieske iron-sulfur signal of the ubiquinol-cytochrome c2 oxidoreductase was present at a 3-fold reduced level on a reaction center basis in comparison to chromatophores. Flash-induced absorbance measurements of the upper pigmented fraction demonstrated reaction center primary and secondary semiquinone anion acceptor signals, but cytochrome b561 photoreduction and cytochrome c1/c2 reactions occurred at slow rates. This fraction was enriched approximately 2- and 4-fold in total b- and c-type cytochromes, respectively, per reaction center over chromatophores, but photoreducible b-type cytochrome was lower. Measurements of respiratory activity indicated a 1.6-fold higher level of succinate-cytochrome c oxidoreductase/reaction center than in chromatophores, but the apparent turnover rates in both preparations were low. Overall, the results suggest that complete cycles of rapid, light-driven electron flow do not occur merely by introduction of newly synthesized reaction centers into respiratory membrane, but that subsequent synthesis and assembly of appropriate components of the ubiquinol-cytochrome c2 oxidoreductase is required.
The oxidation-reduction potentials of Escherichia coli cytochromes have been studied by a recently described technique for automated electrodic potentiometry (Hendler, R.W., Songco, D., and Clem, T.R. (1977) Anal. Chem. 49, 1908-1913; Hendler, R.W. (1977) Anal. Chem. 49, 1914-1918), where entire spectra are recorded at a series of solution potentials. New techniques for resolution of the spectra versus voltage data have been applied. The results indicate that a 1-electron transport chain conducts electrons from substrate to cytochrome d, which is the cytochrome oxidase. Cytochrome d contains several components which appear to increase electron transfer first to a 2-electron stage and then to a 4-electron stage for the final reduction of a molecule of oxygen to 2 molecules of water.
The kinetics of a model reaction between the antitumor drug cis-diamminedichloroplatinum(II)(cis-DDP) and the signal nucleotide diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) has been investigated by spectrophotometry. The formation of the reactive platinum aquated species was first analyzed by potentiometry using a chloride-specific electrode. Both equilibrium and rate constants were measured. The rate constants for the release of the first and second chloride were found 1.1 +/- 0.5 (S.D.) X 10(-4) and 4.2 +/- 0.2 X 10(-5) sec-1, respectively, at 37 degrees. It was shown that anions such as acetate, phosphate, and pyrophosphate were able, in some conditions, to exchange with chloride to form acetato, phosphato, or pyrophosphato complexes. The reaction of cis-DDP with Ap4A or other targets involves at least four steps, which have been analyzed separately. The values of rate constants deduced from the analysis of the overall reaction are in agreement with those determined independently from the separated steps. The second-order rate constants for the reaction of acetato, phosphato, and pyrophosphato complexes with Ap4A (0.2 +/- 0.02, 0.20 +/- 0.02, and 0.16 +/- 0.03 M-1 sec-1, respectively) are close to that of monoaqua-monochloro (0.16 +/- 0.1 M-1 sec-1) and lower than that of the diaqua species (0.94 +/- 0.06 M-1 sec-1). At a high concentration of Ap4A, the reaction kinetics is slowed down. The formation of a complex of cis-platinum with the Ap4A phosphate groups is suggested. The intracellular concentration of phosphates, pyrophosphates, and carboxylates is large enough to displace chloride from cis-DDP. Inside cells, therefore, ligand exchange processes have to be taken into account to analyze the in vivo reactivity of cis-DDP with its potential targets.
The relatively recent distribution of apparati which allow cation measurement by electrometry presents the biologist with a certain number of difficulties inherent to this methodology. A review of the principles of electrochemistry, limited to the facts necessary to master use of these apparati and avoiding the dissipated effort inevitably incurred by consulting treatises, is of an evident practicality. The points concerning, in particular, application in clinical biology have been treated in detail, whether they involved the definition of direct and indirect potentiometries, or the concepts of activity and of concentration, or the explanation of the actual problems posed by the plasma/plasmatic water difference and by electrometry/flame photometry comparison measurement. A survey of the different types of standard electrodes in biology completes this works.
An improved device for potentiometry using magnetic circular dichroism spectroscopy has been developed and used to characterize the potentiometric behavior of solubilized beef heart cytochrome oxidase. In the absence of inhibitors, the electron affinity of cytochromes alpha and alpha 3 are indistinguishable and adequately described by the allosteric model of Nicholls and Peterson (Nicholls, P., and Peterson, L. C. (1972) Biochim. Biophys. Acta 357, 462-467). All of the cytochrome alpha can be accounted for as low spin heme throughout the titration. Cytochrome c present at 1:1, 2:1, and 4:1 stoichiometry with cytochrome alpha did not significantly affect the potentiometric behavior of alpha or chondroitinase alpha 3; at the 1:1 ratio the midpoint potential of cytochrome c was lowered by about 30 mV. In the presence of formate, azide and cyanide cytochrome alpha assumed approximately n = 1 behavior. However, the response of alpha 3 differed with each reagent and was particularly complex in the presence of azide. Fluoride produced very small changes in the potentiometric behavior suggesting that it may not be a ligand to cytochrome alpha 3. Possible deficiencies in the allosteric model are examined.
A procedure for continuous recording of the glycogen synthetase 1 activity, based on the potentiometry, is described. The stoichiometric ratio of H+/UDP, estimated at pH 7.8 and 30 degrees, was equal to 0.89 +/- 0.01. The specific activity of the enzyme did not depend on the buffer capacity in the incubation mixture containing 0.8-10 mM Tris-HCl, pH 7.8. The course of reaction had a linear type at the enzyme concentration of 4-20 mcg/ml in presence of 10 mM MgCl2. The rate of glycogen synthetase reaction was decreased in the course of experiment if the activator was absent. MgCl2 was more suitable activator than Na2SO4, universally accepted for this form of the enzyme.
Sodium was determined by flame photometry and by direct potentiometry in 56 serum or plasma samples from 24 patients with multiple myeloma or macroglobulinemia. We observed differences between the two techniques as large as 17 mmol/L (12%). The flame-photometric values decreased relative to the direct-potentiometric values as protein increased or water content decreased. Moreover, the two sodium measurements could not be interconverted simply on the basis of correcting for protein or water content. There was significantly lower residual variance (p less than 0.005) when the direct-potentiometric sodium values were compared with the osmolality (corrected for the influence of glucose and urea nitrogen) than when the flame-photometric values for sodium were so compared. We conclude that direct potentiometric measurements of sodium in patients with multiple myeloma gives clinically relevant results but flame photometry does not. Clearly, the method by which sodium is measured in patients with multiple myeloma must be considered if results are to be interpreted correctly.
We evaluated an accessory that enables the Du Pont aca discrete analyzer to measure Na+ and K+ by direct potentiometry (aca/ISE). Na+ and K+ gave linear responses in both the blood and urine modes, with no carryover. No interfering species were identified in the blood mode. Intra-assay and interassay precision for Na+ and K+ were more than adequate and analytical recoveries comparable to those with flame photometry were found for plasma. The Na+ and K+ values for plasma were comparable with those obtained by use of another direct potentiometric analyzer (the Orion SS-30), but slightly higher than flame-photometric values. Samples from patients with hyperlipemia and multiple myeloma gave clinically relevant values with the aca/ISE, but the flame photometric values were artefactually low. Whole blood could not be accurately analyzed. The aca/ISE is a precise, easy-to-use instrument, which gives values for plasma similar to those obtained with direct potentiometric analyzers. For analysis of urine, certain precautions are necessary.
Activity of potassium ions was examined in 3 liquid media of 54 rabbit cadavers by potentiometry with the use of a potassium-selective valinomycin electrode. The reported and obtained data were used for the development of the diagnostic regression equations and the curves to define the time of death from the activity of a complex of 3 ions (potassium, sodium and hydrogen) in the blood serum, CSF and vitreous body fluid. The method is offered for appropriate trials in human cadavers.
Interactions in the bio-inorganic systems of the copper ions and azalide (azithromycin) were analyzed by spectroscopic methods (atom-absorption spectroscopy, IR and UV spectrometry in the visible spectrum) and electrochemical methods (potentiometry). The system samples within molar ratios of the metal ion and ligand of 10:1 to 1:10 and wide pH ranges were tested. Formation of a compound consisting of the metal ion and ligand at a ratio of 1:1 was detected. The experimental data showed that the product of the compound solubility equaled 9.8.10(-14) (pH 7.0, 0.1 KNO3).
In this paper a flow injection manifold for the sequential determination of ionic and total calcium in a small (75 microL) sample of saliva is presented. This setup incorporates two detectors, a tubular potentiometric detector and an atomic absorption spectrophotometer, for determining the ionic and total calcium, respectively. Furthermore, the saliva samples can be injected directly into the manifold without any pre-treatment or loss of carbon dioxide. The results of the analyses of 20 saliva samples were in good agreement with those obtained by the two reference procedures, the direct potentiometry for ionic calcium and atomic absorption spectroscopy for total calcium. The paired Student's t-test showed that there were no statistical differences in the results obtained. The relative standard deviations of ten consecutive measurements of the same salive sample were approximately 3% for ionic calcium and 4% for total calcium. Effects of differences in coexisting ions, ionic strength, and pH between standard solutions and samples were negligible.
Reduction capacity of the blood and its fractions was studied by potentiometry in 68 patients with the nephrotic syndrome. The type of renal injury was identified by kidney biopsy in all the patients. Control group consisted of 30 donors. Changes of blood reduction capacity were detected in all the patients with the nephrotic syndrome in comparison with the controls. A correlation could be traced between blood reduction capacity and functional compensation of the nephrotic syndrome. Disordered redox equilibrium was not associated in patients with the nephrotic syndrome with increased levels of lipid peroxidation products. The method used to assess reduction capacity is highly informative, rapid, and simple.
The authors have studied the possibility of using ion-selective electrodes Kritus (Czecho-Slovakia) for analysis of whole blood and serum without preliminary labor-consuming sample preparation. Chloride ions were found to be detectable in the blood serum by potentiometric titration with Ag nitrate solution making use of a pAg-CE-pF-CE pair in ethanol, acetone, or acetic acid medium. Active concentrations of whole blood and serum bromide- and iodide ions may be measured by direct potentiometry with pBr-CE-pF-CE and pI-CE-pF-CE pairs, respectively, against the background of 1 M potassium (or sodium) nitrate solution providing the constancy of solution ionic strength.
N-D-Gluconylglycine, a pseudopeptide derivative glucono-delta-lactone and glycine, was prepared and the equilibrium constants of its protonation and copper(II) coordination and the structures of the copper complexes formed were studied in aqueous solution by potentiometry, spectrophotometry, CD, EPR and 13C-NMR relaxation. The parent complexes formed in acidic medium have low stabilities, characteristic of carboxylate coordination. In the pH range 5-9, the amide group and the 2-OH group of the ligand undergo deprotonation. In parallel with these processes, one ligand is replaced from the copper(II) coordination sphere. For the species MLH-2' we propose (30, 1N) coordination in the equatorial plane around the copper(II). EPR measurements indicate that dimeric species are also formed. At pH > 9, further base-consuming processes start as an indication of the deprotonation of other alcoholic hydroxy groups of the sugar moiety or the formation of mixed hydroxy complexes.
Streptomyces producing ionophore antibiotics were searched for in various natural substrata, such as soil, sea water, and coastline sea mud, in many geographical regions. A total of 393 Streptomyces strains were isolated, 308 of which proved to be capable of producing antibiotics; 135 of these contained water-insoluble antibiotically active substances in the mycelium. Studies by radioindication, spectrophotometry, and potentiometry demonstrated that these partially purified hydrophobic antibiotics possessed ionophore properties. Selectivity to monovalent potassium and ammonium cations seems to be a characteristic feature of hydrophobic antibiotics derived from Streptomyces differing them from other bacteria.
OBJECTIVE: To compare results for sodium and potassium determination on llama urine, using flame emission spectrophotometry (flame photometry), atomic absorption spectrophotometry (AAS), indirect ion-selective electrode potentiometry (ISE), and direct ISE. DESIGN: Llama urine samples encompassing a wide range of electrolyte concentrations were analyzed for sodium and potassium concentrations, using 4 analytical methods, and results were compared statistically to assess correlation, bias, and potential interferents. SAMPLE POPULATION: 10 healthy male llamas. PROCEDURE: Urine specimens were obtained from llamas fitted with urine collection apparatus at defined intervals over a 24-hour period. Urine samples were centrifuged, and supernatants were frozen at -70 C until analysis. Analytical procedures were done, using standard laboratory protocols. Means, correlation coefficients, and bias were calculated, and differences were evaluated by ANOVA, with significance set at P < 0.05. RESULTS: There was strong correlation and good agreement among sodium values obtained by flame photometry, AAS, and indirect ISE. Sodium values obtained by use of direct ISE correlated poorly with other methods; urine is not an acceptable specimen for this method. Only AAS and indirect ISE had good correlation (r > 0.9) for potassium values. Data did not suggest presence of a potassium chelator in llama urine; urine potassium values measured by indirect ISE were significantly higher (by 150 to 200 mmol/L) than those measured by other methods. CLINICAL RELEVANCE: Urine electrolyte analysis in llamas resulted in less agreement between methods than is generally found for serum. Data collection for patient monitoring or research analysis should be restricted to a single method to avoid differences in results attributable to analytical variance.
We report the first solid state X-ray crystal structure for a Eu(II) chelate, [C(NH2)3]3[Eu(II)(DTPA)(H2O)].8H2O, in comparison with those for the corresponding Sr analogue, [C(NH2)3]3[Sr(DTPA)(H2O).8H2O and for [Sr(ODDA)].8H2O (DTPA5 = diethylenetriamine-N,N,N',N",N"-pentaacetate, ODDA2- =1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetate ). The two DTPA complexes are isostructural due to the similar ionic size and charge of Sr(2+) and Eu(2+). The redox stability of [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- complexes has been investigated by cyclovoltammetry and UV/Vis spectrophotometry (ODDM4- =1,4,10,13-tetraoxa-7,16-diaza-cyclooctadecane-7,16-++ +dimalonate). The macrocyclic complexes are much more stable against oxidation than [Eu(II)(DTPA)(H2O)]3- (the redox potentials are E1/2 =-0.82 V, -0.92 V, and -1.35 V versus Ag/AgCl electrode for [Eu(III/II)(ODDA)(H2O)],[Eu(III/II)(ODDM)], and [Eu(III/II)(DTPA)(H2O)], respectively, compared with -0.63 V for Eu(III/II) aqua). The thermodynamic stability constants of [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2- were also determined by pH potentiometry. They are slightly higher for the EuII complexes than those for the corresponding Sr analogues (logK(ML)=9.85, 13.07, 8.66, and 11.34 for [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2-, respectively, 0.1M (CH3)4NCl). The increased thermodynamic and redox stability of the Eu(II) complex formed with ODDA as compared with the traditional ligand DTPA can be of importance when biomedical application is concerned. A variable-temperature 17O-NMR and 1H-nuclear magnetic relaxation dispersion (NMRD) study has been performed on [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- in aqueous solution. [Eu(II)(ODDM)]2- has no inner-sphere water molecule which allowed us to use it as an outer-sphere model for [Eu(II)(ODDA)(H2O)]. The water exchange rate (k298(ex)= 0.43 x 10(9)s(-1)) is one third of that obtained for [Eu(II)(DTPA)(H2O)]3-. The variable pressure 17O-NMR study yielded a negative activation volume, deltaV (not=) = -3.9cm3mol(-1); this indicates associatively activated water exchange. This water exchange rate is in the optimal range to attain maximum proton relaxivities, which are, however, strongly limited by the fast rotation of the small molecular weight complex.