Eccentric cleavage products of beta carotene: biologically active?

The most important role of beta-carotene has long been thought to be the metabolic cleavage at the central double bond to produce two molecules of vitamin A (retinol). There is growing interest in the "eccentric cleavage" of dietary carotenoids at different double bond sites of beta-carotene to produce apocarotenals and their possible oxidation to apocarotenoic acids. However, there are no careful, quantitative analyses of the levels of these compounds in human foods and tissues, and little is known of the enzymology of their formation. This project is part of a larger effort to characterize the full family of putative metabolites of beta-carotenes and lycopene, their occurrence, and their biological significance. We are synthesizing and characterizing all of the possible aldehyde and acid metabolites of beta-carotene for use as analytical standards and for direct assay of their biological activity. Multi-step syntheses were employed to synthesize many of the molecules. Nuclear magnetic resonance spectroscopy, UV-visible spectroscopy, high performance liquid chromatography, and mass spectrometry are being used for characterization. The laboratory of Dr. Earl Harrison (Dept. of Nutrition) is currently studying the interaction of the eccentric cleavage products with the nuclear retinoic acid receptors (RARs), which are responsible for cell differentiation and aspects of the immune response. The interaction of these molecules with other nuclear receptors will be analyzed in the future. The samples will also be used as standards to quantitate the concentrations of eccentric cleavage products in biological samples. The synthesis of the molecules prepared to date will be described as well as aspects of the limited biological activity data gathered to date.No embarg

Detector tilt considerations in high-energy Bragg coherent diffraction imaging: a simulation study

This paper addresses three-dimensional signal distortion and image reconstruction issues in x-ray Bragg coherent diffraction imaging (BCDI) in the event of a general non-orthogonal orientation of the area detector with respect to the diffracted beam. Growing interest in novel BCDI adaptations at fourth-generation synchrotron light sources has necessitated improvisations in the experimental configuration and the subsequent data analysis. One such possibly unavoidable improvisation that is envisioned in this paper is a photon-counting area detector whose face is tilted away from the perpendicular to the Bragg-diffracted beam during acquisition of the coherent diffraction signal. We describe a likely circumstance in which one would require such a detector configuration, along with experimental precedent at third generation synchrotrons. Using physically accurate diffraction simulations from synthetic scatterers in the presence of such tilted detectors, we analyze the general nature of the observed signal distortion qualitatively and quantitatively, and provide a prescription to correct for it during image reconstruction. Our simulations and reconstructions are based on an adaptation of the known theory of BCDI sampling geometry as well as recently developed projection-based methods of wavefield propagation. Such configurational modifications and their numerical remedies are potentially valuable in realizing unconventional coherent diffraction measurement geometries and eventually paving the way for the integration of BCDI into new materials characterization experiments at next-generation light sources.Comment: 13 pages, 5 figure

Examination of Acid-Fast Bacilli in Sputum Using Modified Light Microscope with Homemade Light Emitting Diode Additional Attachment

Typical clinical symptoms and chest X-ray is a marker of Tuberculosis (TB) sufferers. However, the diagnosis of TB in adults should be supported by microscopic examination. Currently, Bacilli microscopic examination of acid-fast bacilli (AFB) in sputum by Ziehl-Neelsen (ZN) coloring is the most widely used. However, for reasons of convenience, especially for laboratories with a considerable amount of smear samples, and due to higher sensitivity compared with ZN staining, the World Health Organization (WHO) has recommended the use of auramine-O-staining (fluorochrome  staining), which is visualized by light emitting diode (LED) fluorescence microscopy. The aim of this study was to evaluate the performance of modified light microscope with homemade LED additional attachment for examination of AFB in sputum using auramine-O-staining method. We compared the sensitivity and specificity of 2 kinds of AFB in sputum methods: ZN and fluorochrome, using culture on Lowenstein-Jensen media as the gold standard. The results showed auramine-O-staining gives more proportion of positive findings (81%) compared to the ZN method (70%). These results demonstrated that the sensitivity of auramine-O-staining was higher than ZN, however it gives more potential false positive results than ZN. The sensitivity of auramine-O-staining in detecting AFB in sputum was 100% while the specificity was 88%

Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in-situ Bragg coherent diffraction imaging

Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. 3D images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O2 and H2. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles