Biocatalytic strategy toward asymmetric β-hydroxy nitriles and γ-amino alcohols

A library of 20 bakers’ yeast reductases, that are overexpressed in Escherichia coli, were screened against a variety of β-keto nitriles. Enzymes from the aldose reductase and the short chain dehydrogenase family displayed activity toward these substrates. All of the seven substrates were reduced with high enantioselectivities and in some cases both antipodes could be synthesized in high ees. These whole-cell reactions afforded gram quantities of asymmetric compounds that could ultimately lead to scaleable and simple synthesis to new drug analogs of serotonin reuptake inhibitors and β-adrenergic blocking agents.     

Interdigitated comb-like electrodes for continuous separation of malignant cells from blood using dielectrophoresis

In this paper, a method for continuous flow separation of circulating malignant cells from blood in a microfluidic device using dielectrophoresis is discussed. Separation of MDA231 breast cancer cells after mixing with normal blood cells was achieved with a level of accuracy that enabled precise counting of the malignant cells, separation and eventually, sub-culturing. MDA231 cells were separated from the blood to a daughter channel using two pairs of interdigitated activated comb-like electrode structures. All experiments are performed with conductivity adjusted medium samples. The electrode pairs were positioned divergent and convergent with respect to the flow. The AC signals used in the separation are 20 V peak-to-peak with frequencies of 10-50 kHz. The separation is based on balance of magnitude of the dielectrophoretic force and hydrodynamic force. The difference in response between circulating malignant cells and normal cells at a certain band of alternating current frequencies was used for rapid separation of cancer cells from blood. The significance of these experimental results is discussed in this paper, with detailed reporting on the suspension medium, preparation of cells, flow condition and the fabrication process of the microfluidic chip. The present technique could potentially be applied to identify incident cancer at a stage and size that is not yet detectable by standard diagnostic techniques (imaging and biochemical testing). Alternatively, it may also be used to detect cancer recurrences.     

Potentiometric Cd-selective electrode with a detection limit in the low ppt range

A recently introduced model describing the response curves of polymer membrane ion-selective electrodes (ISEs) is used here to optimize a Cd²⁺-ISE with a view to achieve very low detection limits. In a first step, the selectivity behavior is determined for two membranes based on the ionophore, N,N,N′,N′-tetradodecyl-3,6-dioxaoctanedithioamide (ETH 5435), but having different concentrations of the ionophore and ion-exchanger. Based on these data, the optimal response curves are calculated with a model that takes into account the ion fluxes induced by interfering ions. The experimental results with different ionic backgrounds correspond very well with the predicted effects. The best lower detection limit of 10⁻¹⁰ M or 11 ppt Cd²⁺ is achieved at pH 7 with an ionic background of 10⁻⁴ M NaNO₃.     

Mega three-photon absorption cross-section enhancement in pseudoisocyanine J-aggregates

Herein we report an extraordinary three-photon absorption cross-section (sigma'3) enhancement in J-aggregates supramolecular systems. The much higher value of sigma'3 in PIC J-aggregate (2.5 x 10(-71) cm6 s2 ph(-2)) compared to typical values obtained in organic molecules (10(-80) cm6 s2 ph(-2)) is attributed to the strong molecular transition dipole moment coupling in the supramolecular assembly. Three-photon absorption of PIC J-aggregates and monomer aqueous solutions were measured using the well known open aperture Z-scan technique pumping with a 25 ps pulse laser-OPG system at 1720 nm. This novel result opens new expectations for applications of supramolecular systems in bioimaging and medicine.     

Characterization of Heavy Metal Air Pollution in Romania Using Moss Biomonitoring,Neutron Activation Analysis,and Atomic Absorption Spectrometry

ABSTRACT

Heavy metal air pollution in Romania was investigated by using passive moss biomonitoring. This study is a component of an international UNECE ICP Vegetation Program – moss survey. A total of 330 samples of Hypnum cupressiforme, Hylocomium splendens, Pleurozium schreberi, and other mosses were collected in Romania in the summer and autumn of 2010. The concentrations of aluminum, cadmium, chromium, copper, iron, lead, nickel, vanadium, and zinc were determined by graphite furnace/flame atomic absorption spectrometry and instrumental neutron activation analysis. The results were statistically processed to obtain spatial distribution maps of factor scores based on elemental concentrations in the moss, together with the spatial distribution maps of heavy metals in moss. The median concentrations of cadmium, 1.20?mg/kg dry weight, and lead, 30.8?mg/kg dry weight, were high compared with other European countries. The results revealed that the atmospheric deposition of these metals is a problem in north and northwest Romania.     

Hoeffding’s inequality for supermartingales

We give an extension of Hoeffding’s inequality to the case of supermartingales with differences bounded from above. Our inequality strengthens or extends the inequalities of Freedman, Bernstein, Prohorov, Bennett and Nagaev.