Application of image analysis technique for the determination of thiophanate methyl by thin-layer chromatography

A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine thiophanate methyl. The detection of pesticide was based on iodine–azide reaction. Digital images of TLC plate chromatograms were analysed using TLSee software, and quantitative analysis was conducted. The linearity (0.3–3.0 µg per spot), sensitivity, accuracy and precision of the system were investigated.     

Gas-Phase Reactions of Dimethyl Disulfide with Aliphatic Carbanions - A Mass Spectrometry and Computational Study

Ion-molecule reactions of Me₂S₂ with a wide range of aliphatic carbanions differing by structure and proton affinity values have been studied in the gas phase using mass spectrometry techniques and DFT calculations. The analysis of the spectra shows a variety of product ions formed via different reaction mechanisms, depending on the structure and proton affinity of the carbanion. Product ions of thiophilic reaction (m/z 47), S_N2 (m/z 79), and E2 elimination – addition sequence of reactions (m/z 93) can be observed. Primary products of thiophilic reaction can undergo subsequent S_N2 and proton transfer reactions. Gibbs free energy profiles calculated for experimentally observed reactions using PBE0/6-311+G(2d,p) method show good agreement with experimental results.

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Absolute Borel sets and function spaces

An internal characterization of metric spaces which are absolute Borel sets of multiplicative classes is given. This characterization uses complete sequences of covers, a notion introduced by Frolík for characterizing Cech-complete spaces. We also show that the absolute Borel class of is determined by the uniform structure of the space of continuous functions ; however the case of absolute metric spaces is still open. More precisely, we prove that, for metrizable spaces and , if is a uniformly continuous surjection and is an absolute Borel set of multiplicative (resp., additive) class , , then is also an absolute Borel set of the same class. This result is new even if is a linear homeomorphism, and extends a result of Baars, de Groot, and Pelant which shows that the \v{C}ech-completeness of a metric space is determined by the linear structure of .

     

Ion flux through membrane channels--an enhanced algorithm for the Poisson-Nernst-Planck model

A novel algorithmic scheme for numerical solution of the 3D Poisson-Nernst-Planck model is proposed. The algorithmic improvements are universal and independent of the detailed physical model. They include three major steps: an adjustable gradient-based step value, an adjustable relaxation coefficient, and an optimized segmentation of the modeled space. The enhanced algorithm significantly accelerates the speed of computation and reduces the computational demands. The theoretical model was tested on a regular artificial channel and validated on a real protein channel-alpha-hemolysin, proving its efficiency.     

Application of Image Analysis Technique for the Determination of Organophosphorus Pesticides by Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine...     

Antagonistic Effects of Endogenous Nitric Oxide in a Glioblastoma Photodynamic Therapy Model

Gliomas are aggressive brain tumors that are resistant to conventional chemotherapy and radiotherapy. Much of this resistance is attributed to endogenous nitric oxide (NO). Recent studies revealed that 5‐aminolevulinic acid (ALA)‐based photodynamic therapy (PDT) has advantages over conventional treatments for glioblastoma. In this study, we used an in vitro model to assess whether NO from glioblastoma cells can interfere with ALA‐PDT. Human U87 and U251 cells expressed significant basal levels of neuronal NO synthase (nNOS) and its inducible counterpart (iNOS). After an ALA/light challenge, iNOS level increased three‐ to fourfold over 24 h, whereas nNOS remained unchanged. Elevated iNOS resulted in a large increase in intracellular NO. Extent of ALA/light‐induced apoptosis increased substantially when an iNOS inhibitor or NO scavenger was present, implying that iNOS/NO was acting cytoprotectively. Moreover, cells surviving a photochallenge exhibited a striking increase in proliferation, migration and invasion rates, iNOS/NO again playing a dominant role. Also observed was a large iNOS/NO‐dependent increase in matrix metalloproteinase‐9 activity, decrease in tissue inhibitor of metalloproteinase‐1 expression and increase in survivin and S100A4 expression, each effect being consistent with accelerated migration/invasion as a prelude to metastasis. Our findings suggest introduction of iNOS inhibitors as pharmacologic adjuvants for glioblastoma PDT.     

Linking metal–organic cages pairwise as a design approach for assembling multivariate crystalline materials

Using metal–organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal–organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu₄L₄ and Rh₄L₄ MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities.

A new strategy to design atomically precise multivariate metal–organic frameworks is presented. This is achieved by linking two preformed metal–organic cages via a precisely tuned Rh–aniline interaction.     

Drag reduction and solvation in polymer solutions

A model is described which explains drag reduction (DR) in dilute polymer solutions in terms of solvation of macromolecular chains and formation of relatively stable domains. The domains partly suppress the vortex formation, act as energy sinks, and also play a role in mechanical degradation in flow (MDF). We report ultrasonically determined solvation numbers for a series of copolymers with the same chemical structure but differing widely in their intrinsic viscosities. The solvation numbers confirm the model. Thus, we have a criterion for selection of DR agents with low MDF for: oil well operations; crude oil transport; fire fighting; high sewer throughput; irrigation; hydrotransport of solids; marine applications; and biomedical applications including the arteriosclerosis prevention.