Anomalous behavior of radioiodine: Solvent extraction from acidic solution

Anomalous behavior of radioiodine was found in solvent extraction. Iodine was extracted into CS₂ from acidic solution over a wide range of iodine concentration. The distribution ratio was obtained by measuring the -rays from iodine-131. The ratio drastically changed at about 10^–5 mol l^–1. The change is readily explained by the kinetic behavior of radioiodine.     

Thermal denaturation of ribonuclease T1 a DSC study

The thermal denaturation of microbial Ribonuclease T1 (RNAase T1) as a function ofpH, was studied by means of DSC microcalorimetry. The midpoint denaturation temperatures, enthalpy changes and heat capacity changes of Ribonuclease T1 were compared with those obtained for pancreatic Ribonuclease A (RNAase A). It was found that the microbial T1 protein undergoes a more complex conformational transition than the simple two-state transition shown by Ribonuclease A. The hypothesis of the presence of a molten globule form is discussed. The conformational stability of RNAase T1 is lower than that of RNAase A at highpH values. Indeed, the maximum stability of RNAase T1 occurs atpH 5, whereas that of RNAase A occurs atpH 8. AtpH=3.7 an irreversible aggregation phenomenon was indicated by the existence of a reproducible exothermic peak. The conformational transition of RNAase T1 is reversible in the range ofpH 4.5–7.0, whereas it becomes irreversible atpH8.0 as for RNAase A.This work was financed by the National Research Council (C.N.R.-Rome) and by Ministry of University and Scientific and Technological Research.     

One pot synthesis of the dinucleoside phosphonate GpCH2U

Summary The preparation of the dinucleoside phosphonate GpCH₂U, starting from the isosteric phosphonate analogue of uridine (3) and the guanosine derivative5 is described.

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Eintopfsynthese des Dinucleosidphosphonats GpCH₂U

Zusammenfassung Die Herstellung des Dinucleosidphosphonats GpCH₂U aus dem isosteren Phosphonatanalogen von Uridin (3) und dem Guanosinderivat5 wird beschrieben.

     

Simultaneous electrophoretic analysis of proteins of very high and low molecular weights using low-percentage acrylamide gel and a gradient SDS-PAGE gel

To be able to separate and analyze giant proteins and small proteins in the same electrophoretic gel, we have used a continuous SDS-PAGE gel formed by the combination of a low-percentage acrylamide gel and a gradient SDS-PAGE gel that we have named LAG gel. To get a good resolution for proteins of more than 200 kDa, we used an acrylamide/bisacrylamide ratio of 80:1 in the low-percentage acrylamide gel. To successfully resolve proteins in the 5-200 kDa range, we used a conventional 6-15% SDS-PAGE gradient gel with the standard acrylamide/bisacrylamide ratio of 40:1. We show that the LAG system can be successfully used in general applications of SDS-PAGE electrophoresis such as proteomics and immunobloting techniques. Thus, using this continuous LAG gel, it is possible to simultaneously analyze giant proteins, such as HERC1 and dynein, big proteins like clathrin heavy chain and small proteins like ARF. The LAG system has a good resolution, low cost, and high reproducibility. Moreover, to simultaneously analyze all proteins saves time. All these characteristics, together with the use of a standard apparatus found in any biochemistry laboratory, make the LAG system an easy tool to use.     

Anomalous magnetic behavior in the transition metal ions doped Cu2O flower-like nanostructures

Cuprous oxide (Cu₂O) flower-like nanostructures doped with various metal ions i.e. Fe, Co, Ni and Mn have been synthesized by an organic phase solution method. The powder X-ray diffraction study clearly reveals them as single phase simple cubic cuprite lattice. Study of their magnetic properties have shown that these doped samples are ferromagnetic in nature; however, no such property was observed for the undoped Cu₂O sample. The magnitude of the ferromagnetic behavior was found to be dependent on the dopant metal ions amount, which increased consistently with its increase. As total magnetic moment contribution of the doped metal ions calculated was insignificant, it is believed to have originated from the induced magnetic moments at cation deficiency sites in the material, created possibly due to the disturbance of the crystal lattice by the dopant ions. The existence of the defects has been supported by photoluminescence spectra of the doped samples.     

Adaptive contrast enhancement of two-dimensional electrophoretic protein gel images facilitates visualization, orientation and alignment

2-DE is a powerful technique to discriminate post-translationally modified protein isoforms. However, all steps of 2-DE preparation and gel-staining may introduce unwanted artefacts, including inconsistent variation of background intensity over the entire 2-DE gel image. Background intensity variations limit the accuracy of gel orientation, overlay alignment and spot detection methods. We present a compact and efficient denoising algorithm that adaptively enhances the image contrast and then, through thresholding and median filtering, removes the gray-scale range covering the background. Applicability of the algorithm is demonstrated on immunoblots, isotope-labeled gels, and protein-stained gels. Validation is performed in contexts of (i) automatic gel orientation based on Hough transformation, (ii) overlay alignment based on cross correlation and (iii) spot detection. In gel stains with low background variability, e.g. Sypro Ruby, denoising will lower the spot detection sensitivity. In gel regions with high background levels denoising enhances spot detection. We propose that the denoising algorithm prepares images with high background for further automatic analysis, without requiring manual input on a gel-to-gel basis.     

Anomalous electrophoretic mobility of microgel particles in buffer solutions

The electrophoretic mobility (μ) of tunable surface charge poly(N-isopropylacrylamide) microgel particles (PNIPAM) was measured vs pH, using different anionic buffers. Two minima, just at the buffers’ pK values, were found for the μ-pH curve. The preferential penetration of the small counterions into the soft-charged shell explains the electrokinetic charge reduction. For pH values higher than the pK, the charge screening leads to electrostatic repulsions among coions. It pushes them towards the particles; thus, balancing the global ionic distribution.     

Anomalous electrophoretic behavior of a chitinase isoform from grape berries and wine in glycol chitin-containing sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels

An anomalous electrophoretic behavior of a chitinase isoform present in both grape (Vitis vinifera L.) berries and wine was observed in glycol chitin-containing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels. A progressive shift of the relative molecular mass M(r) of the enzyme (from approximately 30,500 up to approximately 57,700) with increasing glycol chitin concentration in the gels up to 0.1% was revealed when samples were electrophoresed under nonreducing conditions, whereas the presence of glycol chitin had no effects when samples were reduced before SDS-PAGE separation. The M(r) of other grape and wine chitinase isoforms as well as that of the chitinase from pomegranate (Punica granatum L.) fruit was unaffected by the presence of the substrate in the gel under both reducing and nonreducing conditions. Since the enzymes were inactive during the electrophoretic separation, it is likely that the retarding effect of glycol chitin observed specifically for the unreduced chitinase band from grape and wine was due to an interaction between the substrate and a chitin-binding domain different from the catalytic site, such as that typical of class I and class IV chitinases.     

Cyclen based lanthanide ion ribonuclease mimics: the effect of pyridine cofactors upon phosphodiester HPNP hydrolysis

The cyclen based pyridine complexes 1Ln-3Ln (Ln = La(III) and Eu(III)) were synthesised as metallo-ribonuclease mimics and their ability to hydrolytically cleave the phosphodiester of HPNP at 37 °C was investigated using UV-vis spectroscopy, whereas the binding of the substrate was evaluated using ³¹P NMR and Eu(III)-luminescent measurements. In contrast 2La gave rise to fast pH dependent hydrolysis of HPNP, with maximum efficiency at ca. pH 8.2, and with a half-lifetime of ∼1 h, the 1Ln and 3Ln complexes were found to be inactive, emphasizing the importance of the nature of the pyridine isomer as a cofactor in the hydrolytic process.     

A very short uranium-uranium bond: the predicted metastable U(2)2+

Quantum chemical calculations, based on multiconfigurational wave functions and including relativistic effects, show that the U(2)2+ system has a large number of low-lying electronic states with S of 0 to 2 and Lambda ranging from zero to ten. These states share a very small bond length of about 2.30 A, compared to 2.43 A in neutral U2. The Coulomb explosion to 2 U+ lowers the energy by only 1.6 eV and is separated by a broad barrier.     

Unexpected behavior of the reaction between acyl thioformanilides and acetonitrile derivatives—a useful entry to new penta-substituted dipyrrole disulfides

A convenient and unexpected synthesis of penta-substituted dipyrrole disulfides starting from readily available acyl thioformanilides and acetonitrile derivatives has been developed. The overall process leads to the creation of two C-C bonds, two C-N bonds, and one S-S bond with the concomitant formation of two pyrrole rings and disulfide from the fact that only two reagents need to be mixed together, and it complements the existing pyrrole disulfides chemistry.     

Simultaneous detection of molecular weight and activity of adenylate kinases after electrophoretic separation

Adenylate kinases (AKs) are ubiquitous monomeric phosphotransferases catalyzing the reversible reaction, AMP + MgATP = ADP + MgADP, which plays a pivotal role in the energetic metabolism. In vertebrates, six AK isoforms are known. In this work, we report the detection of many AK isoforms directly on gel or NC after separation by denaturing electrophoresis and electroblotting, by an optimized protocol for the enzyme detection. The method allows to clarify the apparent MW of most of those AK isozymes that follow the cited reaction, especially onto NC where bands are sharper due to the absence of protein diffusion. In contrast, GTP:AMP phosphotransferases are not detectable. AK activity from many sources can be detected in both its reaction courses; ATP production appears as dark-blue bands, while ADP formation appears as nonfluorescent bands over a fluorescent background, under long-wavelength UV light. We show that nondenaturing gel electrophoresis is not the first choice for AK activity detection. Our method is different from the preceding reports on AK activity detection in bacteria after native polyacrylamide gel separations, in the absence of SDS or methanol. The procedure is also quantitative, allowing to determine the amount of enzyme present in samples.     

Anomalous behavior of saturated aqueous tungstate solutions

Potentiometric measurements on a freshly prepared saturated silver tungstate solution at 25°C indicate the existence of at least four different ionic tungstate species in this solution leading to the formation of a four-component precipitate. Solubility measurements have been carried out on saturated aqueous silver tungstate solutions at 25°C at different ionic strengths and at various pH. An attempt is made to explain the appearance of the solubility curves. Conductivity measurements on saturated sodium tungstate solutions indicate a phase transition of solid sodium tungstate at 36.5±1.0°C. The assumption of a phase transition is supported by DTA and TGA measurements.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Phosphine-free cationic rhodium(I) complex-catalyzed disulfide exchange reaction: convenient synthesis of unsymmetrical disulfides

A phosphine-free cationic rhodium(I) complex, [Rh(cod)₂]BF₄, is an effective catalyst for disulfide exchange reaction of symmetrical disulfides to unsymmetrical disulfides under inert atmosphere. This reaction could be carried out using unpurified commercial grade solvents under air without decrease of yields and reaction rates.     

Synergistic behavior of sodiumdodecylsulfate and 1,2-diheptanoyl-sn- glycero-3-phosphocholine in an aqueous medium: interfacial and bulk behavior

The synergistic behavior of sodiumdodecylsulfate (SDS) and 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) binary mixtures has been studied with interfacial and pyrene fluorescence(I ₁/ I ₃) intensity measurements. From the interfacial data, the interfacial parameters; the maximum surface excess (Γ_max), or the minimum area per molecule (A _min), and the surface pressure at the critical micellar concentration (π_cmc) have been evaluated. The cmc value has been used for evaluating the free energies of micellization (ΔG ^o _m). The mixed micelle formation was evaluated with the help of the Clint equation. The SDS plus DHPC mixed micelles showed negative departure from ideality indicating synergistic interactions between the unlike components. The quantitative analysis of mixed micelle, mixed monolayer and the composition of the mixed micelle was carried out with the help of regular solution approximation. The interaction parameters, β and β^σ, in the mixed micelle as well as in the mixed monolayer, respectively showed negative values indicating synergistic behavior of SDS and DHPC molecules.     

Co3O4-SiO2 nanocomposite: a very active catalyst for CO oxidation with unusual catalytic behavior

A high surface area Co(3)O(4)-SiO(2) nanocomposite catalyst has been prepared by use of activated carbon as template. The Co(3)O(4)-SiO(2) composite, the surface of which is rich in silica and Co(II) species compared with normal Co(3)O(4), exhibited very high activity for CO oxidation even at a temperature as low as -76 °C. A rather unusual temperature-dependent activity curve, with the lowest conversion at about 80 °C, was observed with a normal feed gas (H(2)O content ~3 ppm). The U-shape of the activity curve indicates a negative apparent activation energy over a certain temperature range, which has rarely been observed for the heterogeneously catalyzed oxidation of CO. Careful investigation of the catalytic behavior of Co(3)O(4)-SiO(2) catalyst led to the conclusion that adsorption of H(2)O molecules on the surface of the catalyst caused the unusual behavior. This conclusion was supported by in situ diffuse reflectance Fourier transform infrared (DRIFT) spectroscopic experiments under both normal and dry conditions.     

Immunobinding‐induced alteration in the electrophoretic mobility of proteins: An approach to studying the preconcentration of an acidic protein under cationic isotachophoresis

The objective of this study is to explore an approach for analyzing negatively charged proteins using paper‐based cationic ITP. The rationale of electrophoretic focusing the target protein with negative charges under unfavorable cationic ITP condition is to modify the electrophoretic mobility of the target protein through antigen‐antibody immunobinding. Cationic ITP was performed on a paper‐based analytical device that was fabricated using fiberglass paper. The paper matrix was modified with (3‐aminopropyl)trimethoxysilane to minimize sample attraction to the surface for cationic ITP. Negatively charged BSA was used as the model target protein for the cationic ITP experiments. No electrophoretic mobility was observed for BSA‐only samples during cationic ITP experimental condition. However, the presence of a primary antibody to BSA significantly improved the electrokinetic behavior of the target protein. Adding a secondary antibody conjugated with amine‐rich quantum dots to the sample further facilitated the concentrating effect of ITP, reduced experiment time, and elevated the stacking ratio. Under our optimized experimental conditions, the cationic ITP‐based paper device electrophoretically stacked 94% of loaded BSA in less than 7 min. Our results demonstrate that the technique has a broad potential for rapid and cost‐effective isotachphoretic analysis of multiplex protein biomarkers in serum samples at the point of care.     

In-line liquid-phase microextraction for selective enrichment and direct electrophoretic analysis of acidic drugs

This work describes an efficient in-line extraction-preconcentration unit coupled to the electrophoretic capillary based on a liquid-phase microextraction (LPME) process, which can be directly assembled to the cartridge of the commercial CE equipment. The unit permits analyte extraction, preconcentration and electrophoretic separation to be automatically performed in the commercial CE equipment without the need for additional hardware or software. This new approach was usefully used for the separation and determination of nonsteroidal anti-inflammatory drugs in human urine permitting at least to analyze 30 consecutive real samples. The LODs were lower than 2 microg/L and the reproducibility, expressed as RSD, was 3.1% for the same unit and only 4.8% between different units.     

Effect of multiple ionic species on the electrophoretic behavior of a charge-regulated particle

It is often assumed in the conventional electrophoresis analysis that the liquid phase contains only one kind of each cation and anion. That analysis is extended to the case where the liquid phase contains multiple ionic species in this study so that the conditions considered are closer to reality. Using a dispersion of SiO(2) particles, which is of a charge-regulated nature, as an example, where the dispersion pH is adjusted by HCl and NaOH, numerical simulation is conducted to examine the electrophoretic behaviors of the particle under various conditions. We show that the presence of multiple ionic species is capable of yielding profound and interesting electrophoretic behaviors, which are justified by the experimental data in the literature. In addition, we show that two types of double-layer polarization (DLP) are present that have not been reported previously in the electrophoresis analyses. Type I DLP, which reduces the mobility of a particle, occurs inside the double layer, and type II DLP, which raises that mobility, occurs immediately outside the double layer.