Automated cellular sample preparation using a Centrifuge-on-a-Chip

The standard centrifuge is a laboratory instrument widely used by biologists and medical technicians for preparing cell samples. Efforts to automate the operations of concentration, cell separation, and solution exchange that a centrifuge performs in a simpler and smaller platform have had limited success. Here, we present a microfluidic chip that replicates the functions of a centrifuge without moving parts or external forces. The device operates using a purely fluid dynamic phenomenon in which cells selectively enter and are maintained in microscale vortices. Continuous and sequential operation allows enrichment of cancer cells from spiked blood samples at the mL min(-1) scale, followed by fluorescent labeling of intra- and extra-cellular antigens on the cells without the need for manual pipetting and washing steps. A versatile centrifuge-analogue may open opportunities in automated, low-cost and high-throughput sample preparation as an alternative to the standard benchtop centrifuge in standardized clinical diagnostics or resource poor settings.     

Strong polyelectrolyte quantum dot surface for stable bioconjugation and layer-by-layer assembly applications

A series of quantum dot (QD) ligands are reported that can make strong polyelectrolyte QD surfaces with sulfonates or quaternary ammoniums, which can endow QDs with excellent colloidal stability independent of the pH and ionic strength, minimal hydrodynamic size, and can be exploited to achieve stable and flexible bioconjugations and layer-by-layer assembly.     

Physicochemical and sensory properties of irradiated dry-cured ham

To determine the effect of different irradiation doses on ready-to-eat (RTE) dry-cured shoulder hams, physicochemical and sensory attributes were analyzed during 8 weeks of refrigerated storage. The results show that irradiation reduced the redness value and increased the 2-thiobarbituric acid-reactive substance (TBARS) value as well as the irradiation aroma during storage. However, ham samples irradiated with 2.5 and 5.0 kGy did not show significant changes in lightness values compared to the control sample during 8 weeks of storage. TBARS values were lower in the sample irradiated with 2.5 kGy than in the other irradiated samples. The total plate counts of the 5.0 kGy-irradiated samples were not measured after 0 weeks. Sensory panels found that the 2.5- and 5.0 kGy-irradiated samples had better overall acceptability scores than the other irradiated samples. It was concluded that treatments with lower levels of irradiation (≤5.0 kGy) can enhance the microbial safety and sensory acceptance of dry-cured shoulder hams.     

Superior dispersion of highly reduced graphene oxide in N,N-dimethylformamide

Here, we report the effect of temperature on the extent of hydrazine reduction of graphene oxide in N,N-dimethylformamide (DMF)/water (80/20 v/v) and the dispersibility of the resultant graphene in DMF. The highly reduced graphene oxide (HRG) had a high C/O ratio and good dispersibility in DMF. The good dispersibility of HRGs is due to the solvation effect of DMF on graphene sheets during the hydrazine reduction, which diminishes the formation of irreversible graphene sheet aggregates. The dispersibility of the HRGs was varied from 1.66 to 0.38 mg/mL when the reduction temperature increased from 25 °C to 80 °C. The dispersibility of the HRGs was inversely proportional to the electrical conductivity of the HRGs, which varied from 17,400 to 25,500 S/m. The relationships between the C/O ratio, electrical conductivity, and dispersibility of the HRGs were determined and these properties were found to be easily controlled by manipulating the reduction temperature.     

Dual Pd and CuFe2O4 nanoparticles encapsulated in a core/shell silica microsphere for selective hydrogenation of arylacetylenes

A dual catalyst containing Pd and CuFe(2)O(4) nanoparticles in a silica shell exhibits >98% conversion of arylacetylenes to related styrenes with selectivity greater than 98%, which are better than those obtained using a commercial Lindlar catalyst. The excellent synergy was likely a result of the proximal interaction between Pd and CuFe(2)O(4) nanoparticles.     

Explorations of catalytic domains in non-ribosomal peptide synthetase enzymology

Covering up to the end of 2011Many pharmaceuticals on the market today belong to a large class of natural products called nonribosomal peptides (NRPs). Originating from bacteria and fungi, these peptide-based natural products consist not only of the 20 canonical l-amino acids, but also non-proteinogenic amino acids, heterocyclic rings, sugars, and fatty acids, generating tremendous chemical diversity. As a result, these secondary metabolites exhibit a broad array of bioactivity, ranging from antimicrobial to anticancer. The biosynthesis of these complex compounds is carried out by large multimodular megaenzymes called nonribosomal peptide synthetases (NRPSs). Each module is responsible for incorporation of a monomeric unit into the natural product peptide and is composed of individual domains that perform different catalytic reactions. Biochemical and bioinformatic investigations of these enzymes have uncovered the key principles of NRP synthesis, expanding the pharmaceutical potential of their enzymatic processes. Progress has been made in the manipulation of this biosynthetic machinery to develop new chemoenzymatic approaches for synthesizing novel pharmaceutical agents with increased potency. This review focuses on the recent discoveries and breakthroughs in the structural elucidation, molecular mechanism, and chemical biology underlying the discrete domains within NRPSs.     

Co-sheathed SiOx nanowires

We fabricated Co-coated SiO_x nanowires and investigated the effects of thermal annealing on their properties. The sputtering process resulted in the formation of a relatively smooth Co shell layer, whereas subsequent thermal annealing generated the Co₃O₄ phase. The photoluminescence (PL) spectrum was not changed by the Co-coating, whereas the thermal annealing induced new peaks in the yellow and ultraviolet regions. Possible emission mechanisms were discussed. Based on the magnetization measurements of the SiO_x-core/Co-shell nanowires, we obtained small and negligible hysteresis loops for the as-fabricated and thermal annealed samples, respectively.     

Charge fractionalization in nonchiral Luttinger systems

One-dimensional metals, such as quantum wires or carbon nanotubes, can carry charge in arbitrary units, smaller or larger than a single electron charge. However, according to Luttinger theory, which describes the low-energy excitations of such systems, when a single electron is injected by tunneling into the middle of such a wire, it will tend to break up into separate charge pulses, moving in opposite directions, which carry definite fractions f and (1-f) of the electron charge, determined by a parameter g that measures the strength of charge interactions in the wire. (The injected electron will also produce a spin excitation, which will travel at a different velocity than the charge excitations.) Observing charge fractionalization physics in an experiment is a challenge in those (nonchiral) low-dimensional systems which are adiabatically coupled to Fermi liquid leads. We theoretically discuss a first important step towards the observation of charge fractionalization in quantum wires based on momentum-resolved tunneling and multi-terminal geometries, and explain the recent experimental results of Steinberg et al. [H. Steinberg, G. Barak, A. Yacoby, L.N. Pfeiffer, K.W. West, B.I. Halperin, K. Le Hur, Nature Physics 4 (2008) 116].     

Effect of grain boundary on resistive magnetodielectric property of polycrystalline <Emphasis Type="Italic">γ</Emphasis>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

We have investigated the role of the grain boundary on the resistive magnetodielectric property of polycrystalline γ-Fe₂O₃ through impedance spectroscopy measurements. Depending on the sample preparation temperature, the dielectric constant of γ-Fe₂O₃ is significantly different especially at low frequencies (<10⁴ Hz) and high temperatures (>200 K). The value of the magnetodielectric effect at a specific frequency and the resonance frequency for the maximized magnetodielectric effect are different, although polycrystalline γ-Fe₂O₃ samples show a quite similar magnetoresistance. Through the experimentally obtained resistance ratio between the grain and the grain boundary, we can reproduce the magnetodielectric curves based on the Maxwell–Wagner model and the measured magnetoresistance.