Online transient isotachophoresis concentration by the pseudo-terminating electrolyte buffer for the separation of DNA-aptamer and its thrombin complex in poly(methyl methacrylate) microchip

Online automatic transient isotachophoresis concentration of DNA-aptamer and its thrombin complex by using one kind of pseudo-terminating electrolyte buffer in a cross-channel poly(methyl methacrylate) microchip is reported. Sample injection, transient concentration and separation were done continuously and controlled by a sequential voltage switching program, time-consuming steps and complicated chip design were not required. Peak resolution between DNA-aptamer and its thrombin complex was influenced by this novel pseudo-terminating electrolyte buffer, which was prepared by the addition of chemical component with slow mobility into the same buffer as leading electrolyte buffer. 1100-fold signal enhancement of thrombin complex was achieved by this transient isotachophoresis on a standard cross-form microchip. The concentration effect or standing time of transient isotachophoresis was proved to be influenced by the concentration of leading electrolyte ion and the concentration of pseudo-terminating electrolyte buffer ion (glycine). The transient concentration was followed by on-chip nondenaturing gel electrophoresis in methylcellulose solution for the size-based separation. The detection limit, taken as the lowest thrombin concentration at threefold S/N, was determined to be 0.5 amol in mass by this method.     

Multirotations of (Anilinium)([18]Crown‐6) Supramolecular Cation Structure in Magnetic Salt of [Ni(dmit)2]−

A solid‐state dynamic supramolecular structure consisting of (anilinium)([18]crown‐6) was arranged as the cation in a salt of [Ni(dmit)₂]^? (dmit=2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate). With the ammonium moiety of anilinium located within the cavity of [18]crown‐6, a hydrogen‐bonded supramolecular structure is formed, with an orthogonal arrangement between the π plane of anilinium and the mean O6 plane of [18]crown‐6. In this supramolecular cation, both anilinium and [18]crown‐6 act as dynamic units with different rotational modes in the solid state. The uniform stacks of cations form an antiparallel arrangement, thus producing a layer structure. Sufficient space for the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 was observed in the cation layer. Thermally activated 180° flip‐flop motions, with a frequency of 6 MHz at room temperature and an activation energy of 31 kJ mol^?1, were confirmed by temperature‐dependent ²H NMR spectra of ([D₅]anilinium)‐([18]crown‐6)[Ni(dmit)₂]. A double‐minimum potential for the molecular rotation of anilinium, with a barrier of approximately 40 kJ mol^?1, was indicated by ab initio calculations. The wide‐line ¹H NMR spectra indicated a thermally activated rotation of [18]crown‐6 at temperatures above 250 K. Therefore, multiple molecular motions of the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 occur simultaneously in the solid state. The temperature‐dependent dielectric constants revealed that the molecular motion of [18]crown‐6, other than the flip‐flop motion, dominates the dielectric response in the measured temperature and frequency range.     

Rational synthesis of multicyclic bis[2]catenanes

Bis-loop tetraurea calix[4]arene 6 has been prepared by acylation of the wide-rim calix[4]arene tetraamine 1 with the activated bis(urethane) 8 under dilution conditions. Similarly the bis(Boc-protected) tetraamine 2 is converted into the mono-loop derivative 3 which after deprotection and acylation gives the bisalkenyl derivative 5. In apolar solvents this tetraurea calix[4]arene 5 forms regioselectively a single hydrogen-bonded homodimer, from which the bis[2]catenane 10a is formed in 49% by a metathesis reaction followed by hydrogenation. Bis-loop derivative 6 forms no homodimers for steric reasons, but a stoichiometric mixture with the open-chain tetraalkenyl derivative 7a contains exclusively the heterodimer. Metathesis and subsequent hydrogenation now yields 65 % of the pure bis[2]catenane 10a which could not be isolated from the complex reaction mixture obtained from the homodimer 7a.7a. The chirality of 10a (D(2) symmetry) has been verified by optical resolution using HPLC on a chiral stationary phase.     

Mixed boundary element solution for three-dimensional convection-diffusion problem with a velocity profile

A mixed boundary element formulation is presented for convection-diffusion problems with a velocity profile. In this formulation the convection-diffusion equation is considered as a nonlinear diffusion equation with inhomogeneous terms in which the convective term is involved additionally, because the spatial distribution of the drift velocity cannot be straightforwardly expressed in boundary integral form. Accordingly, a corresponding boundary integral equation may be described usually in the form of a so-called hybrid-type boundary integral equation.

In the present paper, mixed boundary elements are employed in a discrete model of the original convection-diffusion system. In the mixed element, potentials are approximated linearly, and their normal derivatives to boundaries are assumed constant. A simple iterative scheme is adopted in order to solve hybrid-type mixed boundary element equations. Simple three-dimensional models are dealt with in numerical experiments. The proposed approach gives more accurate and stable solutions compared with constant boundary elements which have been reported.     

Ferrocenylpyrazole—A versatile building block for hydrogen-bonded organometallic supramolecular assemblies

The crystal architectures of 5-ferrocenylpyrazole (1) and its metal complexes were investigated. Compound 1 can form non-solvated and chloroform-solvated crystals. In both cases, 1 forms a zigzag one-dimensional architecture via NH?N hydrogen bonds. The hydrogen bond exhibits a twofold disorder, which was shown to be static by solid-state ¹³C NMR. In the solvated crystal, the chloroform is released at 415 K, associated with melting of the crystal. The reaction of 1 with metal salts provided metal-centered ferrocenyl clusters [Zn(NO₃)₂(1)₄] (4), [Co(NO₃)₂(1)₄] (5), [CoCl₂(1)₄] (6), [Zn(NCS)₂(1)₂] (7), cis-[Pt(NH₃)₂(1)₂](PF₆)₂ (8), and trans-[Pt(NH₃)₂(1)₄](PF₆)₂ (9). In all of these complexes, 1 acts as a monodentate ligand. In 4, 5, and 7, the multinuclear units are joined via hydrogen bonds to form supramolecular chains. Two polymorphs were found for the crystals of 4. Both are composed of the same hydrogen-bonded chains, but their arrangements are different. 5-Ferrocenyl-1-tritylpyrazole (2) and 4-ferrocenyl-1-methylpyrazole (3) were also crystallographically characterized.     

A remark on the regularity of weak solutions to the Navier–Stokes equations in terms of the pressure in Lorentz spaces

For the incompressible Navier–Stokes equations in R³${\mathbb{R}}^3$, a regularity criterion for weak solutions is proved under the assumption that the pressure belongs to the scaling invariant Lorentz space with small norm, while corresponding results for the velocity field were proved by Sohr. The main theorem continues and extends a previous result given by the author.     

Preparation and chiral recognition ability of crosslinked beads of polysaccharide derivatives

The spherical beads consisting of cellulose 3,5-dimethylphenylcarbamate with partial hydroxyl groups were prepared to be used as chiral packing materials (CPMs) for HPLC. The beads were obtained without using macroporous silica gel, which is usually used as the support of the CPMs based on the polysaccharide derivatives. After the crosslinking in the bead with diisocyanates, such as 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate (DBDI), tolylene-2,4-diisocyanate (TDI), and m-xylylene diisocyanate (XDI), the obtained beads were packed into an HPLC column. As the content of the hydroxyl groups of the cellulose derivatives decreased, the obtained CPM exhibited a higher chiral recognition ability. The beads possessed a higher loading capacity than the CPM prepared by coating the cellulose derivative on silica gel. The crosslinked beads could be used with the eluent containing chloroform. The amylose derivative beads were also prepared as a CPM for chiral HPLC.     

The effect of the particle size on the kinetics of CO electrooxidation on high surface area Pt catalysts

Using high-resolution transmission electron microscopy (TEM), infrared reflection-absorption spectroscopy (IRAS), and electrochemical (EC) measurements, platinum nanoparticles ranging in size from 1 to 30 nm are characterized and their catalytic activity for CO electrooxidation is evaluated. TEM analysis reveals that Pt crystallites are not perfect cubooctahedrons, and that large particles have "rougher" surfaces than small particles, which have some fairly smooth (111) facets. The importance of "defect" sites for the catalytic properties of nanoparticles is probed in IRAS experiments by monitoring how the vibrational frequencies of atop CO (nu(CO)) as well as the concomitant development of dissolved CO(2) are affected by the number of defects on the Pt nanoparticles. It is found that defects play a significant role in CO "clustering"on nanoparticles, causing CO to decrease/increase in local coverage, which yields to anomalous redshift/blueshift nu(CO) frequency deviations from the normal Stark-tuning behavior. The observed deviations are accompanied by CO(2) production, which increases by increasing the number of defects on the nanoparticles, that is, 1 < or = 2 < 5 < 30 nm. We suggest that the catalytic activity for CO adlayer oxidation is predominantly influenced by the ability of the surface to dissociate water and to form OH(ad) on defect sites rather than by CO energetics. These results are complemented by chronoamperometric and rotating disk electrode (RDE) data. In contrast to CO stripping experiments, we found that in the backsweep of CO bulk oxidation, the activity increases with decreasing particle size, that is, with increasing oxophilicity of the particles.     

Oxidative coupling of benzenes with alpha,beta-unsaturated aldehydes by the Pd(OAc)2/molybdovanadophosphoric acid/O2 system

[reaction: see text] The oxidative coupling reaction of benzene with an alpha,beta-unsaturated aldehyde was examined by the combined catalytic system of Pd(OAc)2 with molybdovanadophosphoric acid (HPMoV) under atmospheric dioxygen. Thus, the reaction of benzene with acrolein under dioxygen (1 atm) by the use of catalytic amounts of Pd(OAc)2 and H4PMo11VO40 x 26H2O in the presence of dibenzoylmethane as a ligand in propionic acid at 90 degrees C for 1.5 h afforded cinnamaldehyde in 59% yield and beta-phenylcinnamaldehyde in 5% yield. This catalytic system was extended to the direct oxidative coupling through the C-H bond activation of various arenes with acrolein and methacrolein.