Determination of Nucleic Acids Based on Shifting the Association Equilibrium between a Heptamethine Cyanine Dye and Poly-Lysine

A near-infrared (near-IR) fluorescence recovery method for the determination of nucleic acids is presented. This method employs a two-reagent system composed of anionic heptamethines cyanine (HMC) and polycationic poly-lysine. The fluorescence of HMC, with maximum excitation and emission wavelengths at 778 and 804nm, respectively, was quenched by poly-lysine in proper concentration, but recovered by adding nucleic acids. Under optimal conditions, the recovered fluorescence was proportional to the concentration of nucleic acids. The calibration graphs are linear over the range of 5–300ngmL^–1 for herring sperm DNA (FS DNA), 2–100ngmL^–1 for calf thymus DNA (CT DNA) and 5–500ngmL^–1 for snake ovum RNA (SO RNA). The corresponding detection limits are 1.49ngmL^–1 for FS DNA, 0.7ngmL^–1 for CT DNA and 1.61ngmL^–1 for SO RNA, respectively. Four synthetic and three real nucleic acid samples were determined with satisfactory results.     

Isobaric thermal expansion and isothermal compressibility of ethylbenzene + n-hexane,and + n-octane at 25 and 45°C

Isobaric thermal expansion _p, and isothermal compressibility _p have been determined for binary mixtures of ethylbenzene + n-hexane, and + n-octane in the complete range of composition at 25 and 45°C. The corresponding excess quantities obtained at each measured mole fraction are negative for both systems and show minima at or around equimolecular composition. Absolute values of those excess functions decrease with the chain length of the n-alkane and increase with temperature. Combining these experimental results with data for the heat capacity at constant pressure the isentropic compressibility and the heat capacity at constant volume were calculated at 25°C. The corresponding excess quantities are negative, showing maxima around mole fraction 0.5 and their absolute values decrease for _S ^E and increase for C _V with increasing chain length.     

Small-scale method for the determination of selected organochlorine pesticides in soil

A small-scale method was developed for the simultaneous determination of -HCH, heptachlor, aldrin, dicofol, mirex, endosulfan I, endosulfan II and endosulfan sulphate in soil. The extraction and clean-up steps were combined into one step by transferring soil samples to chromatographic columns prepacked with neutral alumina. The pesticides elution was processed with n-hexane : dichloromethane (7:3) and the concentrated eluate was analysed using gas-liquid chromatography with electron capture detection. Analyses of the in vitro fortified samples with the selected pesticides were performed at three different levels. Mean recoveries for aldrin, -HCH and heptachlor, at levels of 2, 10 and 20 ng/g, ranged from 71 to 87%; for dicofol, at levels of 8, 40 and 80 ng/g, ranged from 97 to 103%; for endosulfan I and II, at levels of 5, 25 and 50 ng/g, ranged from 88 to 96%; for mirex, at levels of 6, 30 and 60 ng/g, ranged from 86 to 110%; and for endosulfan sulphate, at levels of 15, 75 and 150 ng/g, ranged from 93 to 104%. The method can be used for rapid determination of these pesticides in soil.     

Separation of food-related biogenic amines by ion-interaction reversed-phase high performance liquid chromatography. Tyramine,histamine, 2-phenylethylamine,tryptamine and precursor aminoacids. Application to red wine

Summary Methods for the separation of food-related biogenic amines (histamine, tyramine, 2-phenylethylamine and tryptamine) have been developed based on ion-interaction reversed-phase liquid chromatography.Two different interaction reagents have been comparatively used, namely octylamine ortho-phosphate (at wave-lengths of 230, 254 and 280 nm) and octylamine salicylate (at a wavelength of 254 nm). The different elution sequence orders shown by the investigated amines for the two reagents are discussed and compared.The detection limits obtained were 20 ppb for tryptamine ( =280 nm), 500 ppb for 2-phenylethylamine (=254 nm), 400 ppb for tyramine (=230 or 280 nm) and 900 ppb for histamine (=230 nm).The method was applied to the analysis of a five years old Italian red wine, in which 2-phenylethylamine (at a concentration of 72±3 ppm) and tryptamine (at a concentration of 4.0±0.3 ppm) were found to be present.     

The partial molar heat capacity, expansion, isentropic, and isothermal compressions of thymidine in aqueous solution at T = 298.15 K

Solution densities have been determined for aqueous solutions of thymidine at T = (288.15, 298.15, 303.15, and 313.15) K. The partial molar volumes at infinite dilution, , obtained from the density data were used to derive the partial molar isobaric expansion at infinite dilution for thymidine at T = 298.15 K, . The partial molar heat capacity at infinite dilution for thymidine, , at T = 298.15 K has also been determined. Sound speeds have been measured for aqueous solutions of thymidine at T = 298.15 K. The partial molar isentropic compression at infinite dilution, , and the partial molar isothermal compression at infinite dilution, , have been derived from the sound speed data. The , , , and results for thymidine are critically compared with those available from the literature.     

Heterogeneous factors in the photochemical polymerization of methyl methacrylate

A study has been made of the photopolymerization kinetics of methyl methacrylate in bulk. There is an induction period if >310 nm, but this is reduced by previous evacuation of the vessels at 300 C and by exposure to shortwave UV. Wavelengths out to 410 nm will produce polymerization. The quantum yield for chain initiation is 0.001 at 303–313 nm and 0.0003 at 253.7 nm. Initiation occurs at the vessel wall for >310 nm, evidently as a result of a long-wave shift in the absorption band of the monomer.     

Degradation and calcification in vitro of new bioresorbable terpolymers of lactides with an improved degradation pattern

Experimental implants produced from poly(l-lactide/?-caprolactone/glycolide) 80/10/10% (polymer 1), poly(l-lactide/dl-lactide/glycolide) 80/10/10% (polymer 2) and poly(l-lactide/dl-lactide/glycolide) 80/5/15% (polymer 3) were subjected to in vitro degradation in a buffer solution at 37 °C and pH = 7.4 and calcification in vitro was performed at 37 °C in a simulated body fluid for 4, 8, 12, 16, 24, 28, 32 and 36 weeks. In vitro degradation was performed in static and pseudodynamic modes. Samples from poly(l-lactide) were used as a control. The changes in the materials during the course of degradation were assessed from the measurements of molecular weight, mechanical properties and crystallinity. The changes in the appearance of the materials upon degradation and calcification were observed using a scanning electron microscope with an EDAX attachment. The decrease of molecular weight at 4 weeks was 66% for polymer 1, 56% for polymer 2 and 20% for polymer 3. Samples retained 55% of their bending strength at 4 weeks (polymer 1), 50% at 12 weeks (polymer 2) and 99% at 12 weeks (polymer 3). The bending modulus of polymer 3 remained practically unchanged during the first 12 weeks of degradation. Subsequently it increased by 44% at week 16 and remained unchanged up to 24 weeks and next decreased to 33% of the initial value at the end of the experiment at week 32. The bending modulus of polymer 2 decreased 35% at week 8 and subsequently increased to 44% of the initial value at week 16 and remained at this level until week 20. Next the modulus decreased to 84% of the initial value at week 24. The bending modulus of polymer 1 progressively decreased over the first 12 weeks of degradation to 40% of the initial value. The maximum crystallinity attained by the samples at the end of the experiments was 60% for polymer 1 and 38% for polymers 2 and 3. In the static mode the pH remained constant up to week 8 for polymer 1, week 20 for polymer 2 and week 28 for polymer 3. It decreased to 3.8 at weeks 12, 20 and 36 for polymers 1, 2 and 3, respectively. All the samples underwent calcification from week 16 of the experiments with the Ca/P ratio ranging from 0.92 to 1.20.     

Synthesis of cyclic dendronized polymers via divergent "graft-from" and convergent click "graft-to" routes: preparation of modular toroidal macromolecules

Cyclic dendronized polymers represent a new class of polymers which exhibit a donut-like "toroidal" shape. Two previous unreported methods for preparing this architecture, the divergent "graft-from" and the convergent click "graft-to" approaches, are explored and the resulting products fully characterized. This route is particularly attractive because it enables production of exact linear and cyclic dendronized analogues, enabling direct comparison of their physical properties. In this preliminary work, the divergent "graft from" approach appears to lead to materials with broad PDI at high DP, whereas the "graft to" approach yields more well-defined dendronized cyclic polymers at larger DP. On the basis of reports to date, a combination of click cyclization followed by click "grafting to" provides the most versatile route for the synthesis of cyclic dendronized polymers.     

Lactase in Immobilized Cells of Watermelon

A cell suspension culture of Citrullus vulgaris Schrad cv. Samara was permeabilized by Tween 80 and immobilized by glutaraldehyde. The highest lactase activity was achieved at pH 4.3, the temperature optimum for cell suspension was at 50°C, while for the immobilized cells the optimum was at 58°C. The hydrolysis of substrate was linear for 3 h, reaching 60-67% conversion rate. The cells were characterized by high enzyme activity. The stability of the enzyme showed convenient physico-mechanical properties (physical protection from shear forces and easy separation of product from biocatalysts) in long-term storage.     

Lars Onsager (1903–1976), Chemist-Physicist, on the Silver Anniversary of His Death

The Norwegian-born theoretical chemist-physicist Lars Onsager (1903–1976) received the 1968 Nobel Prize for Chemistry for the discovery of the reciprocal relations bearing his name, which are fundamental for the thermodynamics of irreversible processes. A recipient of numerous awards and honorary degrees, which he did not receive until relatively late in life, he taught at the Johns Hopkins and Brown universities, but spent most of his academic career at Yale University (1933–1972). He spent his post-retirement years (1972–1976) as Distinguished University Professor at the University of Miamis Center for Theoretical Studies, where he continued his work with several postdoctoral research fellows.     

Inclusion of Enantiomeric Carvones in β-Cyclodextrin: a Variable Temperature 1H NMR Study in Aqueous Solution

In aqueous solution, the apparent association constant at room temperature for the 1 : 1 inclusion of S-(+)-carvone in - cyclodextrin is double of that for R-(-)-carvone, whereas, at 45 °C, both enantiomers have association constants two orders of magnitude smaller, with the S-(+) inclusion being then slightly weaker than the R-(-) encapsulation. Calculations carried out at the molecular mechanics, AM1 and STO-3G levels confirm the preferential inclusion of the S-enantiomer and provide important clues for understanding chiral discrimination by -cyclodextrin.     

Simple screening method for the fast determination of clenbuterol in animal feeds

Summary A simple method for the determination of clenbuterol is described. It is extracted from the sample at pH 3 and then at pH 11, followed by partitioning the analyte into water at pH 3 and reextraction into ethyl acetate at pH 9. Clenbuterol is oxidized with KMnO₄ to clenbuteron for GC-determination. Recoveries for 0.01– 1.0 mg/kg were between 70% and 110% (standard deviation ±14%, n = 18).

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Eine einfache Screening-Methode zur schnellen Bestimmung von Clenbuterol in tierischen Futtermitteln

     

First heats of solution δH0 of salts in nonaqueous and mixed solvents

A theoretical method is considered for determining H₀ for dissolution of salts in nonaqueous and mixed solvents at various temperatures using published and experimental data for H_m, Values of H₀ were calculated for the dissolution of salts in a number of nonaqueous and mixed solvents at various temperatures. The results obtained were compared with the published data.With an isothermal microcalorimeter, H_m values were determined for the dissolution of potassium nitrate at 25 C in water-glycerol mixtures of various compositions. The results are explained in relation to the structural characteristics of the solvent.     

m-Aminophenylarsonic Acid as a Reagent for the Extraction Preconcentration of Phenol

The azocoupling reaction of phenol with the diazonium salt of m-aminophenylarsonic acid was used for the determination of phenol in water at a level of maximum permissible concentrations. The resulting compound is stable in a wide pH range, which made it possible to develop a procedure for the determination of phenol with the preconcentration of the azo compound by extraction to isobutanol at pH 2 and subsequent back extraction to the aqueous phase at pH 10. The high concentration coefficient of phenol (65) provides for determination of phenol down to 0.9 g/L.     

LC Method for the Determination of Multiple Components in a Compound Cold Formulation

An isocratic liquid chromatographic method for determination of acetaminophen (AMP), caffeine (CAF), chlorphenamine maleate (CPM) and guaiacol glyceryl ether (GGE) in a compound cold formulation is described. Separation and quantitation were achieved on a Diamonsil C18 column using a binary mixture of methanol and 1.5% aqueous acetic acid (55: 45, v/v, pH 3.6) as mobile phase delivered at 0.4 mL min^–1. Single wavelength detection was at 220 nm for all four drugs and the run time was < 10 min. The linearity, accuracy and precision of the method were found to be acceptable over the concentration ranges: 16.0–127.8 g mL^–1 for AMP, 6.0–48.2 g mL^–1 for CAF, 5.0–40.0 g mL^–1 for CPM and 10.1–80.6 g mL^–1 for GGE.     

Formation of monodisperse poly(1-methacryloxybenzotriazole) particles by radiation-induced dispersion polymerization

Radiation-induced dispersion polymerization of 1-methacryloxybenzotriazole (MABt) in ethyl propionate starts as homogeneous mixture and the resulting polymer precipitates as spherical particles. Formation, size, and shape of polymer particles are strongly dependent on the initial monomer concentration. Three regions can be distinguished: formation of deformed particles at concentrations of 15 w/v-% MABt; formation of spherical particles at concentrations from 18 to 35 w/v-% MABt; no precipitation of polymer at concentrations of 40 w/v-% MABt. The spherical particles at 20 w/v-% MABt had a diameter of 0.54 ± 0.31 m for 3 kGy irradiation and 2.93±0.68 m for 30 kGy. The number distribution of the microspheres shows that the spherical particles with small sizes formed at low irradiation dose (low conversion) disappears with increasing irradiation dose because of multi-coating by newly produced polymer.     

The interaction of sodium caseinate with monoglyceride and diglyceride at the oil-water interface in corn oil-in-water emulsions and its effect on emulsion stability

The slow rate of drop coalescence at 5 C in concentrated corn oil-in-water emulsions stabilised with sodium caseinate, glyceryl monostearate and glyceryl distearate was deduced from changes in the drop size distribution. Both pH and the monoglyceride/diglyceride ratio influenced coalescence. At any pH minimum coalescence was observed at a 5/2 monoglyceride/diglyceride ratio. This was attributed to association of caseinate with a previously formed complex of monoglyceride and diglyceride, so supporting an interpretation previously proposed on the basis of rheological data for the emulsions and for films of caseinate-glycerides at the oil-water interface.     

Comparison of microwave and lower-frequency discharges for plasma polymerization

A plasma sustained by surface waves (SW) has been used to study the deposition rate R of hydrocarbon and fluorocarbon plasma polymer films as a function of excitation frequency f=/2 in the range 12–400 MHz. The SW technique allows one to vary only f while keeping constant all other parameters known to influence R, for example, power density in the plasma P. A plot of R/P at a total pressure of 200 m Torr (27 Pa) displays two plateaus, that at f<30 MHz being about five times lower than that at f100 MHz. This is attributed to the fact that electron energy distribution functions differ fundamentally at radio- (f50 MHz) and microwave (f100 MHz) frequencies, for the gas pressure range considered.     

Analysis of reduced glutathione using a reaction with 2,4′-dichloro-1-(naphthyl-4-ethoxy)-s-triazine (EDTN)

A fluorescent adduct was formed between 2,4-dichloro-l-(naphthyl-4-ethoxy)-s-triazine (EDTN) and reduced glutathione in a reaction at 37 °C and pH 9.2. This reaction was used as the basis of an assay for reduced glutathione. The fluorescence was examined at an excitation wavelength of 319 nm and an emission wavelength of 425 nm after extraction of residual unreacted EDTN with methylene dichloride and subsequent dilution of the aqueous phase with ethanol containing 0.01 percent Triton X-100. The reaction rate was low at pH 7 but was accelerated by addition of preparations containing the enzyme glutathione-S-transferase. The adduct gave a discrete peak using isocratic elution with HPLC on a Nova-pak C₁₈ 3 m reverse phase column and a solvent system of methanol: 0.1 M phosphate buffer pH 6.3 (4060). An analytical concentration range of 24 to 240 M reduced glutathione was obtained with an ultraviolet detection system but the concentration range was 7.5 to 75 M when a fluorescence detection system was used. Adducts of other mercapturic acid pathway thiol compounds were not formed at 37 °C under the conditions used and hence did not interfere in the assay. They were formed by heating EDTN and the respective thiol compound at 60 °C for 30 min and they clearly separated from the reduced glutathione compound on HPLC analysis. A strong reaction was observed with digitonin while solutions of tyrosine, at 10 mM concentration, also reacted but these reactants are unlikely to interfere with reduced glutathione analysis in biological systems. When adduct formation was used to estimate reduced glutathione concentrations in some mammalian and plant tissues the reaction using 2,4-dichloro-l-(naphthyl-4-ethoxy)-s-triazine and HPLC separation gave the same results as ano-phthaldialdehyde assay for liver and muscle but the HPLC method gave slightly lower values for other mammalian and plant tissues. The differences were attributed to other material in the tissue extracts which was fluorescing at the same wavelengths as the reduced glutathione adduct.     

Trends in instrumentation for activation analysis of short-lived nuclides

This paper reports on the last year's two major activities of our nuclear instrumentation group it the field of high rate and high resolution gamma spectrometry which were mainly devoted to the needs of activation analysis of short-lived nuclides. The first of the projects was the completion of a state-of-the-art spectrometry system for very high counting rates which has been installed at the fast inrradiation and transport facility of the TRIGA reactor and now is the main instrument for the short-lived work of our radiochemistry group. Based on a laboratory-designed gated integrator pulse processing system and equipped with an Ortec Gamma-X detector of 20% relative efficiency with cooled FET and transistor reset preamplifier, it exhibits a basic resolution of 2.3 keV at 1332 keV which at a counting rate of 1.1 million cps of⁶⁰Co degrades to 3.4 keV. An essential feature of the system is a novel quantitative pileup rejector of the pulse counting type which has been specially designed for high rejection efficiency and at the same time, for the reliable exemption of valid events, and thus is a necessary prerequisite for quantitative real-time correction of counting losses by means of the Virtual Pulse Generator method. The second project included the successful implementation of the novel Preloaded Filter Technique (applied for patent), a new method for high resolution and high throughput processing of nuclear detector signals which, in contrast to conventional techniques, does not rely on a fixed pulse processing time per event which up to now was the main reason for pulse pileup and limited throughput, but, at the latest, terminates the filtering process of an individual event at the instant of arrival of the next event which results in optimized throughput and, at the same time, in a self-adapting, counting rate dependent shaping time. To that aim, the delta-noise filter of the system must be preloaded with the best estimate of the final result of the filtering process which is simply the unfiltered signal amplitude, to make sure that at the instant of termination of the filtering process the output of the filter deviates from the final value not more than by the decaying noise amplitude. Complemented by counting rate dependent step-noise filtering, this technique made possible the creation of a spectrometry system for all purposes which at low to medium counting rates is comparable to the best of the semi-Gaussian amplifiers and at high counting rates to the gated integrator. An experimental implementation of the Preloaded Filter combined with an Ortec Gamma-X detector of 15% relative efficiency resulted in a basic resolution of 1.9 keV at 1332 keV at a counting rate of 5000 cps slowly degrading to 3.2 keV at a counting rate of 650 000 cps of⁶⁰Co.