On‐line separation of bacterial cells by carbon‐electrode dielectrophoresis

Dielectrophoresis (DEP) represents a powerful approach to manipulate and study living cells. Hitherto, several approaches have used 2‐D DEP chips. With the aim to increase sample volume, in this study we used a 3‐D carbon‐electrode DEP chip to trap and release bacterial cells. A continuous flow was used to plug an Escherichia coli cell suspension first, to retain cells by positive DEP, and thereafter to recover them by washing with peptone water washing solution. This approach allows one not only to analyze DEP behavior of living cells within the chip, but also to further recover fractions containing DEP‐trapped cells. Bacterial concentration and flow rate appeared as critical parameters influencing the separation capacity of the chip. Evidence is presented demonstrating that the setup developed in this study can be used to separate different types of bacterial cells.     

Molybdenum Phosphosulfide: An Active,Acid‐Stable,Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.     

Properties of Goethite Grown under the Presence of Cr3+, Cu2+ and Mn2+ Ions

Hyperfine Interactions - This study is focused on properties of goethite related to the inhibition of the corrosion process in low alloy, weathering steels. These steels are characterized by the...     

Asymptotic structure, -estimates of sequences, and compactness of multilinear mappings

We relate the moduli of asymptotic uniform smoothness and convexity of a Banach space with the existence of upper and lower ℓ_p-estimates of sequences in the space. To this end, we introduce two properties which are related to the (m_p)-property defined by Kalton and Werner. In this way we obtain a connection between the moduli of asymptotic uniform smoothness and convexity, and compactness or weak-sequential continuity of multilinear mappings. Finally, we give some applications to the existence of analytic and asymptotically flat norms on a Banach space.     

On the spectrum ofC b 1 (E)

This research was supported in part by D.G.I.C.Y.T. (Project PB-87-1031), Spain and by U.S.-Spain. Joint Committee (Project CCB-8609/025)     

Multiplicative functionals on algebras of differentiable functions

Research supported in part by D.G.I.C.Y.T Project PB-87-1031, Spain.     

Pattern of distribution and cycling of SLOB,Slowpoke channel binding protein,in <Emphasis Type="Italic">Drosophila</Emphasis>

Background  

SLOB binds to and modulates the activity of the Drosophila Slowpoke (dSlo) calcium activated potassium channel. Recent microarray analyses demonstrated circadian cycling of slob mRNA.     

Synthesis of N-methylpyrrole and N-methylimidazole amino acids suitable for solid-phase synthesis

New and higher yielding synthetic routes to N-protected N-methylpyrrole and N-methylimidazole amino acids are introduced to circumvent difficulties associated with established schemes. Key steps in each synthesis include copper-mediated cross-coupling reaction to directly install a carbamate-protected 4-amine in the N-methylpyrrole derivative and effective nitration followed by a one-pot reduction/Boc protection of the amine in the synthesis of the N-Me-imidazole amino acid.     

Polyethyleneimine‐Coated Gold Nanoparticles: Straightforward Preparation of Efficient DNA Delivery Nanocarriers

A novel one‐pot method for the synthesis of polyethyleneimine (PEI)‐coated gold nanoparticles (AuPEI‐NPs) that combines the reductant–stabilizer properties of PEI with microwave irradiation starting from hydrogen tetrachloroaurate acid (HAuCl₄) and branched PEI 25 kDa (b25kPEI) was explored. The method was straightforward, green, and low costing, for which the Au/PEI ratio (1:1 to 1:128 w/w) was a key parameter to modulate their capabilities as DNA delivery nanocarriers. Transfection assays in CHO‐k1 cells demonstrated that AuPEI‐NPs with 1:16 and 1:32 w/w ratios behaved as effective DNA gene vectors with improved transfection efficiencies (twofold) and significantly lower toxicity than unmodified b25kPEI and Lipofectamine 2000. The transfection mediated by these AuPEI‐NP–DNA polyplexes preferentially used the caveolae‐mediated route for intracellular internalization, as shown by studies performed by using specific internalization inhibitors as well as colocalization with markers of clathrin‐ and caveolae‐dependent pathways. The AuPEI‐NP polyplexes preferentially used the more efficient caveolae internalization pathway to promote transfection, a fact that supports their higher transfection efficiency relative to that of Lipofectamine 2000. In addition, intracellular trafficking of the AuPEI‐NPs was studied by transmission electron microscopy.     

Synthesis of Magnetite in Presence of Cu2+ or Cr3+

The effects of Cu or Cr ions on the formation of magnetite, which were prepared by two different methods, were studied by ⁵⁷Fe Mössbauer spectrometry. The first synthesis procedure consisted in an alkaline hydrolysis of ferrous chloride solution in accordance with literature reports. The second method, which was a variation of a reported synthetic route, consisted of a reaction of a 2:1 Fe(II)/Fe(III) solution under alkaline conditions in the presence of an oxidant agent. The samples were also prepared in the presence of chromium or copper chloride solutions. Our results showed that the magnetites obtained via the first procedure exhibits a higher degree of stoichiometry and a better crystalline quality than those prepared by the second route. It seems that the presence of chromium helped the formation of goethite, whereas the presence of copper interfered with it in agreement with other works. We observed that the magnetites obtained in the presence of copper were of poorer crystallinity than the ones obtained with chromium. Finally, the influence of Cu or Cr upon the magnetic and crystalline properties of the two series of magnetites is also presented and discussed.