Standardization of 177Lu by means of 4π(LS)β-γ coincidence and anti-coincidence counting

Journal of Radioanalytical and Nuclear Chemistry - The activity concentration of a 177Lu solution was measured by the Laboratory of Radioactivity Standards in the Radioisotope Centre POLATOM. The...     

Stereochemistry of 1-hydroxyphosphonate-phosphate rearrangement. Retention of configuration at the phosphorus atom

1-Hydroxyphosphonate 1 in the presence of triethylamine in acetonitrile solution undergoes irreversible rearrangement to phosphate 2 and reversible retro-phospho-aldol (retro-Abramov) reaction. The X-ray structures for 1 and 2 revealed that the phosphonate-phosphate rearrangement occurs with retention of configuration at the phosphorus atom.     

Invariance in a class of Bajraktarevi? means

Let I⊂R be a non-trivial interval, s:I→(0,∞) be a function, and let φ,ψ be real continuous strictly monotonic functions defined on I. We consider the equation

     

Application of BDD thin film electrode for electrochemical decomposition of heterogeneous aromatic compounds

The aim of the presented study is to investigate the applicability of electrochemical oxidation of aromatic compounds containing heteroatoms, e.g. waste from production of pesticides or pharmaceutics, at a borondoped diamond (BDD) electrode. The BDD electrodes were synthesized by microwave plasma enhanced chemical vapour deposition (MW PE CVD). Investigation of the electrode surface by optical microscopy and scanning electron microscopy (SEM) confirmed that the synthesized layer was continuous and formed a densely packed grain structure with an average roughness of less than 0:5 ??m. The influence of important electrochemical parameters: current density, kind of reactor, pH or mixing operation, on the efficiency of the oxidation was investigated. The fouling of electrode??s surface caused by the deposition of organic material was observed during CV and galvanostatic experiments. At low current density the oxidation rate constant k was low, but the current efficiency was relatively high. The BDD can be used successfully to remove heterogeneous aromatic compounds existing either as molecules or cations. During 4 h of electrolysis 95% of aromatic compounds were electrochemically decomposed to mineral forms. It was observed that the influence of the initial pH on mineralization was marginal.     

Search of nature of planar chirality for pendent benzodiazacoronands in the solid state: NMR, X-ray, and DFT studies

In this work, we report the structural studies on the solid state of two benzodiazacoronads that form chiral and achiral crystals. Crystals have to be considered as a two-component system consisting of an organic unit and a water molecule in 1:1 ratio. Both components play an important role in the crystal structure. The strong (O-H...O, N-H...O) and weak (C-H...O) intermolecular hydrogen bonds are responsible for phase organization and, in consequence, formation of chiral or achiral crystals. The alignment of the water molecule with respect to the macrocycle is different for samples 1 and 2. Removal of water from the crystal lattice of 1 is reversible. Formation of chiral cocrystals from two different achiral molecules by self-assembly is well-known. However, in this paper, we show that the water molecule can be an important achiral cofactor responsible for chiral crystallization.     

Time-dependent stokes shifts of fluorescent dyes in the hydrophobic backbone region of a phospholipid bilayer: combination of fluorescence spectroscopy and ab initio calculations

We explored the time-dependent Stokes shifts of fluorescent dyes containing an anthroyloxy chromophore (2-AS, 9-AS, and 16-AP) in bilayers composed of palmitoyl-oleoyl-phosphatidylcholine. The obtained data revealed a nontrivial solvation response of these dyes, which are located in the backbone region of the bilayer with a gradually increasing depth. For comparison, steady-state emission spectra in the neat solvents of various polarities and viscosities were also recorded. The results indicate that on the short picosecond time scale the AS dyes undergo complex photophysics including formation of states with a charge-transfer character. This observation is supported by ab initio calculations of the excited states of 9-methylanthroate. The slower nanosecond part of the relaxation process can be attributed to the solvation response of the dyes. A slowdown in solvent relaxation is observed upon moving toward the center of the bilayer. A mechanism similar to preferential solvation present in the mixture of a polar and nonpolar solvent is considered to explain the obtained data.     

Chemical Changes in the Broccoli Volatilome Depending on the Tissue Treatment

The storage of plant samples as well as sample preparation for extraction have a significant impact on the profile of metabolites, however, these factors are often overlooked during experiments on vegetables or fruit. It was hypothesized that parameters such as sample storage (freezing) and sample pre-treatment methods, including the comminution technique or applied enzyme inhibition methods, could significantly influence the extracted volatile metabolome. Significant changes were observed in the volatile profile of broccoli florets frozen in liquid nitrogen at −20 °C. Those differences were mostly related to the concentration of nitriles and aldehydes. Confocal microscopy indicated some tissue deterioration in the case of slow freezing (−20 °C), whereas the structure of tissue, frozen in liquid nitrogen, was practically intact. Myrosinase activity assay proved that the enzyme remains active after freezing. No pH deviation was noted after sample storage - this parameter did not influence the activity of enzymes. Tissue fragmentation and enzyme-inhibition techniques applied prior to the extraction influenced both the qualitative and quantitative composition of the volatile metabolome of broccoli.     

Application of organolithium and related reagents in synthesis. Part 25: Novel specific synthesis of the 4-arylisochroman-3-acetic acids via conversion of benzoic acids

The transformation of the benzanilides 1 into 4-arylisochroman-3-acetic acids 8 applying the following sequence of reactions is described. At first, the 3-arylphthalides 3 were obtained via metallation [n-BuLi] of benzanilides 1 and subsequent treatment of the generated bis-lithiated anilides 2 with aromatic aldehydes. Next, the 3-arylphthalides 3 were reduced [LiBH₄] to phthalanes 5 and then, via reductive metallation [Li/C₁₀H₈] and reaction of the generated bis-lithiated species 6 with dimethylformamide, 3-hydroxy-4-arylisochromans 7 were produced. In the final step the isochromans 7 were treated with 1-methoxy-1-trimethylsilyloxyethene in the presence of titanium tetrachloride and furnished 4-arylisochromans-3-acetic acid methyl esters 8 as trans stereoisomers (Ψ-e/e).