Surface modified microarray chip and laser induced fluorescence microscopy to detect DNA cleavage

This work describes a quantitative method to detect DNA damage in the presence of Pb and Cd ions using a surface modified microarray chip and a laser induced fluorescence microscopy (LIFM). The detection was carried out by the immobilization of a single-stranded DNA oligomer, tagged with a Cy5 fluorophore on a polydimethylsiloxane (PDMS) microarray chip followed by LIFM. Sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (Sulfo-SMCC) was attached as a cross-linker via the formation of covalent amide bonds. Then, the single-stranded DNA oligomer containing Cy5 as a fluorophore and thiol functional groups at both terminals, was bonded to the linker by reaction with sulfhydryl group. As the DNA oligomers were reacted with metal ions of Pb and Cd, the un-cleaved DNA oligomers were quantitatively identified by monitoring Cy5 fluorescence. Cadmium showed a quenching constant of 0.84 in the Stern–Volmer plot, whereas lead gave 0.22, indicating that cadmium ions suppress fluorescence more than lead ions. When optimized, fluorescence reductions of 23% (± 2.1) for Pb and 25% (± 1.4) for Cd were observed in air and decreased to almost < 5.0% in a radical scavenger of 5 mM. The cleaved DNA was also confirmed by MALDI-TOF-MS. In result, this experimental method using a microarray chip with surface modification provided quantitative determination of DNA oligomer damage with reproducible results, significantly reduced sample volumes and analysis times.     

Quantification of tryptic peptides in quadrupole ion trap using high-mass signals derived from isotope-coded N-acetyl dipeptide tags

Isotope-labeled N-acetyl dipeptides (Ac-Xxx-Ala) are coupled to the primary amines of tryptic peptides and then analyzed by tandem mass spectrometry. Amide bond cleavage between Xxx and Ala provides both low- and high-mass isotope-coded signals for quantification of peptides. Especially, facile cleavage at the modified lysine side chain yields very strong high-mass quantitation signals in a noise-free region. Tagging tryptic peptides with isobaric N-acetyl dipeptides is a viable strategy for accurate quantification of proteins, which can be used with most quadrupole ion trap mass spectrometers carrying the 1/3 mass cut-off problem.     

A magnetic resonance (MR) microscopy system using a microfluidically cryo-cooled planar coil

We present the development of a microfluidically cryo-cooled planar coil for magnetic resonance (MR) microscopy. Cryogenically cooling radiofrequency (RF) coils for magnetic resonance imaging (MRI) can improve the signal to noise ratio (SNR) of the experiment. Conventional cryostats typically use a vacuum gap to keep samples to be imaged, especially biological samples, at or near room temperature during cryo-cooling. This limits how close a cryo-cooled coil can be placed to the sample. At the same time, a small coil-to-sample distance significantly improves the MR imaging capability due to the limited imaging depth of planar MR microcoils. These two conflicting requirements pose challenges to the use of cryo-cooling in MR microcoils. The use of a microfluidic based cryostat for localized cryo-cooling of MR microcoils is a step towards eliminating these constraints. The system presented here consists of planar receive-only coils with integrated cryo-cooling microfluidic channels underneath, and an imaging surface on top of the planar coils separated by a thin nitrogen gas gap. Polymer microfluidic channel structures fabricated through soft lithography processes were used to flow liquid nitrogen under the coils in order to cryo-cool the planar coils to liquid nitrogen temperature (-196 °C). Two unique features of the cryo-cooling system minimize the distance between the coil and the sample: (1) the small dimension of the polymer microfluidic channel enables localized cooling of the planar coils, while minimizing thermal effects on the nearby imaging surface. (2) The imaging surface is separated from the cryo-cooled planar coil by a thin gap through which nitrogen gas flows to thermally insulate the imaging surface, keeping it above 0 °C and preventing potential damage to biological samples. The localized cooling effect was validated by simulations, bench testing, and MR imaging experiments. Using this cryo-cooled planar coil system inside a 4.7 Tesla MR system resulted in an average image SNR enhancement of 1.47 ± 0.11 times relative to similar room-temperature coils.     

Asymmetric synthesis of 1-deoxyazasugars from chiral aziridines

A general and facile synthesis of enantiopure 1-deoxyazasugars was achieved from stereoselective dihydroxylation of a common synthetic intermediate, piperidine ring fused oxazolidin-2-one, originating from a commercially available starting substrate, chiral aziridine-2-carboxylate, in high yields.     

The monotonic property and stability of solutions of fractional differential equations

In this paper we improve on the monotone property of Lemma 1.7.3 in Lakshmikantham et al. (2009) [5] for the case g(t,u)=λu with a nonnegative real number λ. We also investigate the Mittag-Leffler stability of solutions of fractional differential equations by using the fractional comparison principle.     

Decoration of glassy carbon surfaces with dendrimer-encapsulated nanoparticles with a view to constructing bifunctional nanostructures

We demonstrate a method for constructing bifunctional nanostructures, which conjugate biochemical and electrocatalytic activities, on glassy carbon surfaces by decorating the carbon surfaces with both biologically active glucose oxidases and size-monodisperse Pt nanoparticles (less than 2 nm in diameter) utilizing only a single dendrimer layer.     

Influence of TiO2 nanotube morphology and TiCl4 treatment on the charge transfer in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were fabricated using TiO₂ nanoparticles (NPs), TiO₂ nanotube arrays (NTAs), and surface-modified NTAs with a TiCl₄ treatment. The photovoltaic efficiencies of the DSSCs using TiO₂ NP, NTA, and TiCl₄-treated NTA electrodes are 4.25, 4.74, and 7.47 %, respectively. The highest performance was observed with a TiCl₄-treated TiO₂ NTA photoanode, although in the case of the latter two electrodes, the amounts of N719 dye adsorbed were similar and 68 % of that of the NP electrode. Electrochemical impedance measurements show that the overall resistance, including the charge–transfer resistance, was smaller with NTA morphologies than with NP morphologies. We suggest that a different electron transfer mechanism along the one-dimensional nanostructure of the TiO₂ NTAs contributes to the smaller charge–transfer resistance, resulting in a higher short circuit current (J _sc), even at lower dye adsorption. Furthermore, the TiCl₄-treated NTAs showed even smaller charge–transfer resistance, resulting in the highest J _sc value, because the downward shift in the conduction band edge improves the electron injection efficiency from the excited dye into the TiCl₄-treated TiO₂ electrodes.     

Small sample properties of generalized logit model estimators with bootstrap

The generalized logit model of nominal type with random regressors is studied for bootstrapping. We assess the accuracy of some estimators for our generalized logit model, using a Monte Carlo simulation. That is, we study the finite sample properties containing the consistency and asymptotic normality of the maximum likelihood estimators. Also, we compare Newton Raphson algorithm with BHHH algorithm.     

Lewis-type catalytic activity of direct incorporated Zr- and Sn-SBA-16 catalysts

Metal incorporation into nanoporous materials could give Lewis acid sites through the framework substitution of silica matrix, which are supposed to be in tetrahedral substitution of silica. In this work, Zr- and Sn-incorporated SBA-16 were directly synthesized by the microwave synthesis method. These microwave synthesized Zr- and Sn-incorporated mesoporous silica materials were applied in activation of ketones by Lewis acid sites to catalyze Meerwein-Ponndorf-Verly reduction of cyclohexanone and Baeyer-Villiger oxidation of adamantanone, respectively. Optimum incorporated Zr- and Sn-species gave almost 100% selectivity with high activity onto corresponding alcohol and lactone, respectively.     

Off-peak saturation effects of beam-plasma instability

For beam-plasma instability in the absence of a magnetic field, hybrid simulations produce almost identical results to those of particle simulations (both agree with linear and nonlinear analyses), but with much reduced computing cost and noise level. With the verification by simulations, it is shown that the saturation level is very strongly influenced by the discrete wave number spectrum, sometimes giving different, by an order of magnitude, results by choosing slightly different off-peak (in growth rate curve) parameters, which must be considered in most simulations (whether hybrid or particle or whether magnetized or unmagnetized)