Single-Scan Diffusion-Ordered NMR Spectroscopy of SABRE-Hyperpolarized Mixtures

The analysis of complex mixtures of dissolved molecules is a major challenge, especially for systems that gradually evolve, e. g., in the course of a chemical reaction or in the case of chemical instability. 1D NMR is a fast and non-invasive method suitable for detailed molecular analysis, though of low sensitivity. Moreover, the spectral resolution of proton, the most commonly used and most sensitive stable isotope in NMR, is also quite limited. Spatially encoded (SPEN) experiments aim at creating in one acquisition a 2D data set by simultaneously performing different 1D sub-experiments on different slices of the NMR tube, at the price of an extra loss of sensitivity. Choosing translational diffusion coefficients as the additional dimension (the so-called DOSY approach) helps to recover proton spectra of each molecule in a mixture. The sensitivity limitation of SPEN NMR can, on the other hand, be addressed with hyperpolarization methods. Within hyperpolarization methods, signal amplification by reversible exchange (SABRE), based on parahydrogen, is the cheapest and the easiest one to set up, and allows multi-shot experiments. Here we show that the spectra of a mixture's components at millimolar concentration are resolved in few seconds by combining the SABRE, SPEN and DOSY concepts.     

Docetaxel Loaded in Copaiba Oil-Nanostructured Lipid Carriers as a Promising DDS for Breast Cancer Treatment

Breast cancer is the neoplasia of highest incidence in women worldwide. Docetaxel (DTX), a taxoid used to treat breast cancer, is a BCS-class-IV compound (low oral bioavailability, solubility and intestinal permeability). Nanotechnological strategies can improve chemotherapy effectiveness by promoting sustained release and reducing systemic toxicity. Nanostructured lipid carriers (NLC) encapsulate hydrophobic drugs in their blend-of-lipids matrix, and imperfections prevent drug expulsion during storage. This work describes the preparation, by design of experiments (2³ factorial design) of a novel NLC formulation containing copaiba oil (CO) as a functional excipient. The optimized formulation (NLC_DTX) showed approximately 100% DTX encapsulation efficiency and was characterized by different techniques (DLS, NTA, TEM/FE-SEM, DSC and XRD) and was stable for 12 months of storage, at 25 °C. Incorporation into the NLC prolonged drug release for 54 h, compared to commercial DTX (10 h). In vitro cytotoxicity tests revealed the antiproliferative effect of CO and NLC_DTX, by reducing the cell viability of breast cancer (4T1/MCF-7) and healthy (NIH-3T3) cells more than commercial DTX. NLC_DTX thus emerges as a promising drug delivery system of remarkable anticancer effect, (strengthened by CO) and sustained release that, in clinics, may decrease systemic toxicity at lower DTX doses.     

Halogenation of a twisted non-polar π-system as a tool to modulate phosphorescence at room temperature

Halogenation of a twisted three-fold symmetric hydrocarbon with F, Cl or Br leads to strong modulation of triplet–triplet annihilation and dual phosphorescence, one thermally activated and the other very persistent and visible by eye, with different relative contributions depending on the halide. The room temperature phosphorescence is highly unusual given the absence of lone-pair-contributing heteroatoms. The interplay between the spin–orbit coupling matrix elements and the spatial configuration of the triplet state induces efficient intersystem crossing and thus room temperature phosphorescence even without relying on heteroatomic electron lone pairs. A ninefold increase of the ISC rate after introduction of three bromine atoms is accompanied by a much higher 34-fold increase of phosphorescence rate.

Twisted π-systems investigation showed a very unusual HAE, influencing independently the ISC and the dual phosphorescence emission, one being very persistent at room temperature and visible by eye in powder.     

Simultane Dezimilligrammbestimmung von Kohlenstoff, Wasserstoff und Stickstoff in organischen Substanzen

Zusammenfassung Die früher beschriebene Methode für die simultane Dezimilligrammbestimmung von Kohlenstoff, Wasserstoff und Stickstoff ist weiter entwickelt worden. Stickstoff wird unter vermindertem Druck gemessen und Kohlendioxid und Wasser werden ausgefroren und nicht mehr mit Lauge absorbiert. Die Standardabweichungen von 17 direkt nacheinander ausgeführten Analysen von Substanzen mit weit verschiedener Zusammensetzung (enthaltend unter anderem Fluor, Chlor, Brom, Jod, Schwefel, Phosphor und Kalium) betrugen für Kohlenstoff 0,21%, Wasserstoff 0,23% und Stickstoff 0,10% (nur sechs der analysierten Substanzen enthielten Stickstoff). Die Zuverlässigkeit der Methode ist sehr gut. In der Regel brauchen nur Einzelanalysen ausgeführt zu werden.

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Summary The earlier described method for the simultaneous decimilligram determination of carbon, hydrogen and nitrogen has been further developed. Nitrogen is measured at reduced pressure and carbon dioxide and water are frozen out and no longer absorbed in potassium hydroxide. The standard deviations of a series of 17 analyses of samples with widely different compositions (containing among other elements fluorine, chlorine, bromine, iodine, sulfur, phosphorus and potassium) were: 0.21% for carbon, 0.23% for hydrogen and 0.10% for nitrogen (only six of the analyzed substances contained nitrogen). The reliability of the method is very good. As a rule it is not necessary to carry out duplicate analyses.

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Frühere Mitteilung W. Kirsten⁴.

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Die Arbeit wured durch Unterstützung durch die schwedischen staatlichen medizinischen und naturwissenschaftlichen Forschungsräte ermöglicht.     

Palladium-catalyzed cross-coupling of diaryliodonium salts with organotin compounds

M. V. Lomonosov Moscow State University, 119899 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2683–2685, November, 1992.     

Electronic interactions in a branched chromophore investigated by nonlinear optical and time-resolved spectroscopy

The third order nonlinear optical properties of a trimer branched chromophore system and its linear molecule analog are investigated. Two-photon absorption and degenerate four wave mixing measurements were carried out on both systems. An enhancement in the nonlinear optical effect is observed for the branched trimer molecule in comparison to the linear chromophore system. Ultrafast time-resolved measurements were carried out to probe the excited state dynamics in the branched structures. The time-resolved measurements suggest that the two important processes affecting the nonlinear optical properties in the trimer system, charge transfer stabilization and initial electronic delocalization, occur on two different time scales.     

Light scattering study of a twist grain boundary liquid crystal

Dynamic light scattering is used to probe the fluctuation modes of a liquid crystal exhibiting twist grain boundary (TGB) structure. At the chiral nematic to proposed "chiral line liquid" phase transition, anomalous temperature dependence in the fluctuation spectrum and an instability in the helicoidal director structure signify developing TGB order. At lower temperatures, the behavior of the smectic layer-director fluctuations ("soft" mode) indicates that the previously identified commensurate TGB(A) phase may in fact be a TGB(C) phase with an unusually small tilt angle.     

ChemInform Abstract: A New Cu,Al Fluoride Disilicate CuAl2F2(Si2O7) and Its Relations to Topaz.

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