Pb(II) sorption onto gamma-Al2O3 surfaces at the oxide-water interface: a novel approach using planar oxides

A novel technique for examining metal-ion interactions at the solid-water interface is introduced. Planar oxides, flat, thin coatings of uniform thickness created on a metal support, have been constructed as useful analogs for investigating metal-solid interactions under a variety of conditions. XPS and ToF/SIMS results from sorption studies at pH 6.0 show that the sorption behavior of Pb on each phase is similar with Pb binding preferentially to the bulk gamma-Al(2)O(3). This may be due to the presence of defect sites on the bulk oxides, the preferential exposure of a specific crystallographic plane in the planar oxides, or it may be an artifact of instrumental analysis. A second study examining Pb sorption to planar gamma-Al(2)O(3) under a series of increasingly complex conditions shows that our methods are able to successfully characterize sorption complexes formed in the presence of environmentally derived complexants. Results suggest that Pb is more strongly complexed by aqueous phase organic matter than sediment-bound organic material, indicating a possible control on Pb sorption in natural environments. Overall, the use of planar oxides combined with a powerful suite of spectroscopic tools provides a promising approach to better understanding metal ion sorption to natural sediment surfaces in aquatic environments.     

Operator-valued Chandrasekhar H-functions

Operator valued analogs of the Chandrasekhar H-function, that occur in the study of neutron transport in a slab with continuous energy dependence and anisotropic scattering, satisfy a system of nonlinear integral equations. An appropriate Banach space setting is found for the study of this system. We show that the system may be solved by iteration. We extend the domain of analyticity of H_r and H_t by means of bifurcation theory.     

Site-specific assembly of DNA and appended cargo on arrayed carbon nanotubes

We describe a strategy that permits discrete regions of arrayed carbon nanotubes (CNTs) to be functionalized simultaneously and specifically with DNA oligonucleotides. The different chemical properties of two regions on single CNTs and orthogonal chemical coupling strategies have been exploited to derivatize CNTs within highly ordered arrays with multiple DNA sequences. Through duplex hybridization, we then targeted different DNA sequences with appended metal nanoparticles to distinct sites on the CNT architecture with precise spatial control. The materials generated from these studies represent the first CNTs with bipartite functionalization. The approach described provides a high level of precision in parallel and directed assembly of DNA sequences and appended cargo and is useful for the preparation of novel hybrid bionanomaterials.     

Solvent effects on the resonance Raman and hyper-Raman spectra and first hyperpolarizability of N,N-dipropyl-p-nitroaniline

Linear absorption spectra, resonance Raman spectra and excitation profiles, and two-photon-resonant hyper-Rayleigh and hyper-Raman scattering hyperpolarizability profiles are reported for the push-pull chromophore N,N-dipropyl-p-nitroaniline in seven solvents spanning a wide range of polarities. The absorption spectral maximum red shifts by about 2700 cm(-1), and the symmetric -NO2 stretch shifts to lower frequencies by about 11 cm(-1) from hexane to acetonitrile, indicative of significant solvent effects on both the ground and excited electronic states. The intensity patterns in the resonance Raman and hyper-Raman spectra are similar and show only a small solvent dependence except in acetonitrile, where both the Raman and hyper-Raman intensities are considerably reduced. Quantitative modeling of all four spectroscopic observables in all seven solvents reveals that the origin of this effect is an increased solvent-induced homogeneous broadening in acetonitrile. The linear absorption oscillator strength is nearly solvent-independent, and the peak resonant hyperpolarizability, beta(-2omega;omega,omega), varies by only about 15% across the wide range of solvents examined. These results suggest that the resonant two-photon absorption cross sections in this chromophore should exhibit only a weak solvent dependence.     

Modulation of the NOTCH1 Pathway by LUNATIC FRINGE Is Dominant over That of MANIC or RADICAL FRINGE

Fringes are glycosyltransferases that transfer a GlcNAc to O-fucose residues on Epidermal Growth Factor-like (EGF) repeats. Three Fringes exist in mammals: LUNATIC FRINGE (LFNG), MANIC FRINGE (MFNG), and RADICAL FRINGE (RFNG). Fringe modification of O-fucose on EGF repeats in the NOTCH1 (N1) extracellular domain modulates the activation of N1 signaling. Not all O-fucose residues of N1 are modified by all Fringes; some are modified by one or two Fringes and others not modified at all. The distinct effects on N1 activity depend on which Fringe is expressed in a cell. However, little data is available on the effect that more than one Fringe has on the modification of O-fucose residues and the resulting downstream consequence on Notch activation. Using mass spectral glycoproteomic site mapping and cell-based N1 signaling assays, we compared the effect of co-expression of N1 with one or more Fringes on modification of O-fucose and activation of N1 in three cell lines. Individual expression of each Fringe with N1 in the three cell lines revealed differences in modulation of the Notch pathway dependent on the presence of endogenous Fringes. Despite these cell-based differences, co-expression of several Fringes with N1 demonstrated a dominant effect of LFNG over MFNG or RFNG. MFNG and RFNG appeared to be co-dominant but strongly dependent on the ligands used to activate N1 and on the endogenous expression of Fringes. These results show a hierarchy of Fringe activity and indicate that the effect of MFNG and/or RFNG could be small in the presence of LFNG.     

Ein elektrotitrimetrisches Verfahren zur Bestimmung von Vanadin

Ohne Zusammenfassung     

High-Performance Nucleic Acid Sensors for Liquid Biopsy Applications

Circulating tumour nucleic acids (ctNAs) are released from tumours cells and can be detected in blood samples, providing a way to track tumors without requiring a tissue sample. This “liquid biopsy” approach has the potential to replace invasive, painful, and costly tissue biopsies in cancer diagnosis and management. However, a very sensitive and specific approach is required to detect relatively low amounts of mutant sequences linked to cancer because they are masked by the high levels of wild-type sequences. This review discusses high-performance nucleic acid biosensors for ctNA analysis in patient samples. We compare sequencing- and amplification-based methods to next-generation sensors for ctDNA and ctRNA (including microRNA) profiling, such as electrochemical methods, surface plasmon resonance, Raman spectroscopy, and microfluidics and dielectrophoresis-based assays. We present an overview of the analytical sensitivity and accuracy of these methods as well as the biological and technical challenges they present.