High-resolution iterative frequency identification for NMR as a general strategy for multidimensional data collection

We describe a novel approach to the rapid collection and processing of multidimensional NMR data: "high-resolution iterative frequency identification for NMR" (HIFI-NMR). As with other reduced dimensionality approaches, HIFI-NMR collects n-dimensional data as a set of two-dimensional (2D) planes. The HIFI-NMR algorithm incorporates several innovative features. (1) Following the initial collection of two orthogonal 2D planes, tilted planes are selected adaptively, one-by-one. (2) Spectral space is analyzed in a rigorous statistical manner. (3) An online algorithm maintains a model that provides a probabilistic representation of the three-dimensional (3D) peak positions, derives the optimal angle for the next plane to be collected, and stops data collection when the addition of another plane would not improve the data model. (4) A robust statistical algorithm extracts information from the plane projections and is used to drive data collection. (5) Peak lists with associated probabilities are generated directly, without total reconstruction of the 3D spectrum; these are ready for use in subsequent assignment or structure determination steps. As a proof of principle, we have tested the approach with 3D triple-resonance experiments of the kind used to assign protein backbone and side-chain resonances. Peaks extracted automatically by HIFI-NMR, for both small and larger proteins, included approximately 98% of real peaks obtained from control experiments in which data were collected by conventional 3D methods. HIFI-NMR required about one-tenth the time for data collection and avoided subsequent data processing and peak-picking. The approach can be implemented on commercial NMR spectrometers and is extensible to higher-dimensional NMR.     

Exploring and modeling the ion mobility spectrometry of perindopril: Example of protonation-dissociation reactions in large molecules

The current research is constructed for considering the chemical ionization and dissociation of perindopril in the positive mode of corona discharge ion mobility spectrometry. Four product ion peaks are observed in the ion mobility spectrum of perindopril erbumine at the cell temperature of 473 K. These peaks are assigned through the obtained intensity variation analysis in the ion mobility spectra over the elapsed time accompanied by the calculations backed by the validated density functional theory (DFT). In this regard, the most stable ionic species associated with each peak and the corresponding reliable generation pathways are found by the well-confirmed meta hybrid density functional method, M06-2X. The peaks are assigned to the protonated perindopril and its dissociation products, including counter ion and the related fragment ions. However, the structures of the neutral perindopril in the gas phase are thoroughly assessed to find a more stable one. The predicted chemical ionization products by the theory are in excellent agreement with our presented experiment here. Theoretical evaluations demonstrated that the production of a fragment by dissociation process occurs when perindopril gets a proton from the ionization region. Also, without protons, there is no dissociation process. Therefore, our mechanism investigated here is the proton transfer one. All possible sites of perindopril are considered theoretically for protonation along with their possible reactions. In addition to the computed PES, the assigned ions for obtained spectra are confirmed by the computed equilibrium constants and rate constants. Our theoretical results show that the peak of the main fragment is for M-CH₃CH₂OH produced by a reaction pathway involving no barrier. This study opens new perspectives in interpreting large molecules spectra for future studies.     

Covalent bonding of magnetic Fe3O4 nanoparticles to aminopropyl‐functionalized magnesium phyllosilicate clay: Synthesis and cytotoxic potential investigation

Stable water dispersion of Fe₃O₄ magnetic nanoparticles (NPs) were successfully synthesized by using 3‐glycidoxypropyltrimethoxysilane (GPTMS) and Mg‐phyllo (organo) silicate known as aminoclay (AC) containing pendant amino groups with the approximate composition (R₈Si₈Mg₆O₁₆(OH)₄, R = CH₂CH₂CH₂NH₂). The Fe₃O₄‐GPTMS magnetic NPs with an epoxy functional group are suitable for forming a covalent bond with the amine group of aminoclay in an epoxy ring opening reaction. Appropriate Fe₃O₄‐GPTMS‐aminoclay (FG‐AC) magnetic composite are promising carriers for the targeting and delivery of platinum‐based anticancer drugs. Analysis of the cytotoxicity of the nanostructures on a K562 leukemia cell line using a colorimetery assay shows that both the FG‐AC and cis‐platin/FG‐AC magnetic composite were biocompatible. The nanostructures characterizations were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy and energy dispersive analysis of X‐ray techniques. Magnetic measurement revealed that the saturated magnetization of the FG‐AC nanocomposite reached 7.6 emu/g and showed the characteristics of magnetism.     

Optimization of effective processing parameters of hybrid anti-corrosion Si/Zr sol–gel coatings doped with cerium salt for aluminum alloy 6061

Journal of Sol-Gel Science and Technology - In this study, the Taguchi method was used to design of experiment to obtain optimum conditions for hybrid Si–Zr sol–gel coating doped with...     

Lentivirus-mediated transgene delivery to the hippocampus reveals sub-field specific differences in expression

Background  

In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus.     

Mixed mode I/II brittle fracture in V-notched Brazilian disk specimens under negative mode I conditions

The well-known round-tip V-notched Brazilian disk specimen is utilized for conducting mixed mode I/II fracture tests on PMMA under negative mode I conditions for different notch angles and various notch radii with the aim to measure experimentally the fracture load and the fracture initiation angle. It is shown by the finite element analysis that although the notch is under negative mode I loading, one side of the notch border still experiences tensile tangential stresses suggesting that fracture would take place from the same side of notch border. Experimental observations also indicated that fracture occurs from the tensile side of the notch border confirming the finite element results. The experimental results are then theoretically estimated by means of two stress-based brittle fracture criteria, namely the round-tip V-notch maximum tangential stress and the mean-stress criteria. It is shown that both criteria provide very good predictions to the experimental results obtained under negative mode I conditions.     

Effect of photoanode active area on photovoltaic parameters of dye sensitized solar cells through its effect on series resistance investigated by electrochemical impedance spectroscopy

In the present work, the dependence of photovoltaic parameters of laboratory-scale dye sensitized solar cells (DSSCs) on photoanode active area (A) and also the effect of using current collector on this dependency were investigated. Current collectors were applied, in the form of silver strips, on the edges of electrodes. Electrochemical impedance spectroscopy (EIS) and current-voltage (I-V) curve measurement were employed as characterizing methods. The role of current collector was to decrease the resistance against current collection from the surface of electrodes and thus to decrease series resistance of DSSCs. It was observed that all photovoltaic parameters, i.e., short circuit current density (J _sc), open circuit voltage (V _oc), fill factor (FF), and power conversion efficiency (η), decrease with increasing A. Applying current collector had no influence on photovoltaic parameters of smallest DSSC, but it improved the performance of larger DSSCs. Also, applying current collector caused the photovoltaic parameters of DSSCs to be less dependent on A. It was shown that A dependence of photovoltaic parameters was due to the effect of A on area-specific series resistance (r _s) of DSSC. Also, the effect of current collector on A dependency of photovoltaic parameters was due to its effect on A dependency of r _s.