Negatively charged micelles directed synthesis of snow-ball flower like superparamagnetic Ni nanoparticles and investigation of their properties

Snow-ball flower like Ni nanoparticles have been synthesized using negatively charged micelles. Negatively charged micelles incorporate the Ni⁺² onto its head group by electrostatic attraction and again a surfactant layer is arranged on positively charged Ni and thus in a repetitive way layer-by-layer a snow-ball flower like structure is formed. After reduction of Ni⁺² to Ni atom by sodium borohydride and hydrated hydrazine the Ni clusters (3 nm) are formed and confined in micelles in snow-ball flower like pattern. The sizes of these nanoflowers are of 30 nm order. The particles are superparamagnetic in nature with blocking temperature about 117 K.     

Role of the gouy phase in the coherent phase control of the photoionization and photodissociation of vinyl chloride

We demonstrate theoretically and experimentally that the Gouy phase of a focused laser beam may be used to control the photoinduced reactions of a polyatomic molecule. Quantum mechanical interference between one- and three-photon excitation of vinyl chloride produces a small phase lag between the dissociation and ionization channels on the axis of the molecular beam. Away from the axis, the Gouy phase introduces a much larger phase lag that agrees quantitatively with theory without any adjustable parameters.     

Electron spin relaxation of copper(II) complexes in glassy solution between 10 and 120 K

The temperature dependence, between 10 and 120 K, of electron spin-lattice relaxation at X-band was analyzed for a series of eight pyrrolate-imine complexes and for ten other copper(II) complexes with varying ligands and geometry including copper-containing prion octarepeat domain and S100 type proteins. The geometry of the CuN4 coordination sphere for pyrrolate-imine complexes with R=H, methyl, n-butyl, diphenylmethyl, benzyl, 2-adamantyl, 1-adamantyl, and tert-butyl has been shown to range from planar to pseudo-tetrahedral. The fit to the recovery curves was better for a distribution of values of T1 than for a single time constant. Distributions of relaxation times may be characteristic of Cu(II) in glassy solution. Long-pulse saturation recovery and inversion recovery measurements were performed. The temperature dependence of spin-lattice relaxation rates was analyzed in terms of contributions from the direct process, the Raman process, and local modes. It was necessary to include more than one process to fit the experimental data. There was a small contribution from the direct process at low temperature. The Raman process was the dominant contribution to relaxation between about 20 and 60 K. Debye temperatures were between 80 and 120 K. For samples with similar Debye temperatures the coefficient of the Raman process tended to increase as gz increased, as expected if modulation of spin-orbit coupling is a major factor in relaxation rates. Above about 60 K local modes with energies in the range of 260-360 K (180-250 cm-1) dominated the relaxation. For molecules with similar geometry, relaxation rates were faster for more flexible molecules than for more rigid ones. Relaxation rates for the copper protein samples were similar to rates for small molecules with comparable coordination spheres. At each temperature studied the range of relaxation rates was less than an order of magnitude. The spread was smaller between 20 and 60 K where the Raman process dominates, than at higher temperatures where local modes dominate the relaxation. Spin echo dephasing time constants, Tm, were calculated from two-pulse spin echo decays. Near 10 K Tm was dominated by proton spins in the surroundings. As temperature was increased motion and spin-lattice relaxation made increasing contributions to Tm. Near 100 K spin-lattice relaxation dominated Tm.     

Regioselective N‐Alkylation of Ethyl 4‐Benzyloxy‐1,2,3‐triazolecarboxylate: A Useful Tool for the Synthesis of Carboxylic Acid Bioisosteres

Acidic 4‐hydroxy‐1,2,3‐triazole is a proven bioisostere of acidic functions that has recently been used to replace the acidic moieties of biologically active leads. Straightforward chemical strategies for the synthesis of the three possible N‐alkylated 4‐hydroxy‐1,2,3‐triazole regioisomers have been designed and reported herein, by identifying the optimal conditions under which the alkylation of ethyl 4‐benzyloxy‐1,2,3‐triazolecarboxylate (compound 19 ) can be regiodirected to the triazole N(b) position and thus produce the only isomer that cannot be obtained via the cycloaddition reaction. Furthermore, an innovative platform for parallel synthesis, called Arachno and which has been patented by the authors' group, has been used to speed up the process, and an NMR study has been carried out to better understand the reactivity of compound 19 towards the N(b) position. A library of benzyloxy protected 4‐hydroxy‐1,2,3‐triazoles has been prepared using the two strategies: regiodirection for the N(b) and N(c) isomers and cycloaddition for the N(a) isomers; the processes are described herein. The three N‐alkylated regioisomer series have been characterized spectroscopically (NMR and MS). The subsequent catalytic hydrogenation of the 4‐benzyloxy protective group on the N‐alkylated‐4‐benzyloxy‐5‐ethoxycarbonyl‐1,2,3‐triazoles provided the corresponding substituted 4‐hydroxy‐1,2,3‐triazoles.     

Microwave-sintered Pr<Superscript>3+</Superscript>, Sm<Superscript>3+</Superscript>, and Gd<Superscript>3+</Superscript> triple-doped ceria electrolyte material for IT-SOFC applications

The Pr³⁺, Sm³⁺, and Gd³⁺ triple-doped ceria Ce_0.76Pr_0.08Sm_0.08Gd_0.08O_2-δ material as solid electrolyte for IT-SOFC has been successfully synthesized by sol–gel auto-combustion route. The effect of microwave sintering (1300 °C for 15, 30, and 60 min, named as PSG-MS15, PSG-MS30, and PSG-MS60, respectively) on structural, electrical, and thermal properties of prepared electrolyte material has been studied. Powder X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, and Raman analysis revealed the single phase, microstructure, elemental confirmation, and structural oxygen vacancy formation of all the samples. Impedance spectroscopy analysis revealed the highest total ionic conductivity, i.e., 3.47 × 10^?2 S cm^?1 at 600 °C with minimum activation energy of 0.69 eV, in PSG-MS30 sample when compared to PSG-MS15 and PSG-MS60. The thermal expansion measurements have been carried out for PSG-MS30 specimen. The highest total ionic conductivity with minimum activation energy and moderate thermal expansion coefficient of PSG-MS30 sample makes the possibility of its use as solid electrolyte in IT-SOFC applications.     

Applications of MALDI-MS/MS-Based Proteomics in Biomedical Research

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is one of the most widely used techniques in proteomics to achieve structural identification and characterization of proteins and peptides, including their variety of proteoforms due to post-translational modifications (PTMs) or protein–protein interactions (PPIs). MALDI-MS and MALDI tandem mass spectrometry (MS/MS) have been developed as analytical techniques to study small and large molecules, offering picomole to femtomole sensitivity and enabling the direct analysis of biological samples, such as biofluids, solid tissues, tissue/cell homogenates, and cell culture lysates, with a minimized procedure of sample preparation. In the last decades, structural identification of peptides and proteins achieved by MALDI-MS/MS helped researchers and clinicians to decipher molecular function, biological process, cellular component, and related pathways of the gene products as well as their involvement in pathogenesis of diseases. In this review, we highlight the applications of MALDI ionization source and tandem approaches for MS for analyzing biomedical relevant peptides and proteins. Furthermore, one of the most relevant applications of MALDI-MS/MS is to provide “molecular pictures”, which offer in situ information about molecular weight proteins without labeling of potential targets. Histology-directed MALDI-mass spectrometry imaging (MSI) uses MALDI-ToF/ToF or other MALDI tandem mass spectrometers for accurate sequence analysis of peptide biomarkers and biological active compounds directly in tissues, to assure complementary and essential spatial data compared with those obtained by LC-ESI-MS/MS technique.     

Use of an approximate diabatic molecular representation in He+ -He charge transfer collision

A single-configuration “frozen-orbital” molecular basis set has been used as an approximation to the “standard” radial diabatic representation defined by Smith. The usefulness of this approximate representation has been demonstrated in an eight-state close-coupled treatment of the He⁺ -He resonant transfer collisions in the impact parameter approximation. Apart from the Σ-Σ potential couplings the two Σ-Π rotational couplings at short range have been considered. Generally satisfactory agreement with the experimental data of Nagy ., together with a significant improvement in the estimate of the rotational coupling effects toward the region of large EO (? 3-4 keV deg) as compared to the earlier theoretical work of McCarroll and Piacentini is obtained.     

The octarepeat domain of the prion protein binds Cu(II) with three distinct coordination modes at pH 7.4

The prion protein (PrP) binds Cu2+ in its N-terminal octarepeat domain. This unusual domain is comprised of four or more tandem repeats of the fundamental sequence PHGGGWGQ. Previous work from our laboratories demonstrates that at full copper occupancy, each HGGGW segment binds a single Cu2+. However, several recent studies suggest that low copper occupancy favors different coordination modes, possibly involving imidazoles from histidines in adjacent octapeptide segments. This is investigated here using a combination of X-band EPR, S-band EPR, and ESEEM, along with a library of modified peptides designed to favor different coordination interactions. At pH 7.4, three distinct coordination modes are identified. Each mode is fully characterized to reveal a series of copper-dependent octarepeat domain structures. Multiple His coordination is clearly identified at low copper stoichiometry. In addition, EPR detected copper-copper interactions at full occupancy suggest that the octarepeat domain partially collapses, perhaps stabilizing this specific binding mode and facilitating cooperative copper uptake. This work provides the first complete characterization of all dominant copper coordination modes at pH 7.4.     

Spectrophotometric determination of arsenic via arsine generation and in-situ colour bleaching of methylene blue (MB) in micellar medium

A new spectrophotometric method has been developed to determine arsenic in parts-per-million (ppm) level. It is based on the colour bleaching of methylene blue (MB) in anionic micellar medium. Arsine gas was formed by borohydride reduction of arsenite/arsenate. Arsine generation and colour bleaching (quantification of arsenic) could be done in one-pot. The presence of silver or gold nanoparticles makes the determination faster. Different calibration graphs at the three different ranges of arsenic concentration such as 0-8.63, 0-1.11 and 0-0.11 ppm were constructed and limit of detection (LODs) were found to be 1.3, 0.53 and 0.03 ppm, respectively. The method is simple, rapid, reproducible (relative standard deviations lies within +/-5%) and eco-friendly. It is free from phosphate and silicate interferences and applicable for real sample analysis.