Novel bipolar bathophenanthroline containing hosts for highly efficient phosphorescent OLEDs

The electronic structures of eight bathophenanthroline derivatives were elucidated by DFT calculations, and four representatives of which CZBP, m-CZBP, m-TPAP, and BPABP were synthesized and employed as the hosts to afford highly efficient phosphorescent OLEDs. The calculated molecular orbital energies agree well with the experimental results, which further demonstrates that the localization of HOMO and LUMO at the respective hole- and electron-transporting moieties is desirable in bipolar molecular designs.     

A note on -bases of a regular affine domain extension

Let be a tower of commutative rings where is a regular affine domain over an algebraically closed field of prime characteristic and is a regular domain. Suppose has a -basis over and . For a subset of whose elements satisfy a certain condition on linear independence, let be a set of maximal ideals of such that is a -basis of over . We shall characterize this set in a geometrical aspect.

     

Effects of dispersion stabilizer and reaction solvent on forming monodisperse polystyrene microspheres by dispersion polymerization

We used poly(aspartic acid) (PAsp) synthesized by ion exchange with sodium polyaspartate (PAspNa) as a dispersion stabilizer. PAsp improved the dispersion stability and the solubility in the medium for dispersion polymerization. The effects of the stabilizer hydrophobicity on particle formation, conversion, particle diameter, and its distribution of polystyrene microspheres were investigated by using both biodegradable polymers as a dispersion stabilizer. According to these results, we concluded that the polymerization rate of the styrene with PAsp was higher than that of styrene with PAspNa. That is why, smaller and more monodisperse microspheres were prepared with PAsp, compared to those with PAspNa.     

Dynamic transitions in molecularly thin liquid films under frictional sliding

The friction properties of the molecularly thin films of an asymmetric ether, 1,3-dimethylbutyl hexadecyl ether (DBHE), confined between mica surfaces were investigated using the surface forces apparatus. Kinetic friction was measured as a function of normal load and sliding velocity, and the static friction (stiction) was measured as a function of normal load and surface stopping time. Kinetic friction measurements exhibited unstable sliding dynamics: the friction force exhibited cyclic bumps and valleys in the sliding velocity range from about 10(-2) to 1 microm/s, but above and below the velocity range, smooth sliding was observed. Stop-start experiments showed a stiction spike when surface stopping time exceeded a characteristic nucleation time, indicative of the static friction state at very low sliding velocity. These results imply that the friction of the confined DBHE film has at least three responsible friction states--static friction and two different kinetic friction states--depending on the sliding velocity. The unstable sliding (bumps and valleys of the friction force) reflects the dynamic transition between two different kinetic states. The different friction states and their transitions are discussed on the basis of the recent experiments and theories of "inverted" stick-slip friction.     

Highly productive droplet formation by anisotropic elongation of a thread flow in a microchannel

We developed a microfluidic device to form monodisperse droplets with high productivity by anisotropic elongation of a thread flow, defined as a threadlike flow of a dispersed liquid phase in a flow of an immiscible, continuous liquid phase. The thread flow was anisotropically elongated in the depth direction in a straight microchannel with a step, where the microchannel depth changed. Consequently, the elongated thread flow was given capillary instability (Rayleigh-Plateau instability) and was continuously transformed into monodisperse droplets at the downstream area of the step in the microchannel. We examined the effects of the flow rates of the dispersed phase and the continuous phase on the droplet formation behavior, including the droplet diameter and droplet formation frequency. The droplet diameter increased as the fraction of the dispersed-phase flow rate relative to the total flow rate increased and was independent of the total flow rate. The droplet formation frequency proportionally increased with the total flow rate at a constant dispersed-phase flow rate fraction. These results are explained in terms of a mechanism similar to that of droplet formation from a cylindrical liquid thread flow by Rayleigh-Plateau instability. The microfluidic device described was capable of forming monodisperse droplets with a 160-microm average diameter and 3-microm standard deviation at a droplet formation frequency of 350 droplets per second from a single thread flow. The highest total flow rate achieved was 6 mL/h using the present device composed of a straight microchannel with a step. We also demonstrated parallel droplet formation by anisotropic elongation of multiple thread flows; the process was applied to form W/O and O/W droplets. The highly productive droplet formation process presented in this study is expected to be useful for future industrial applications.     

Electrokinetic analyte transport assay for alpha-fetoprotein immunoassay integrates mixing, reaction and separation on-chip

A rapid and highly sensitive CE immunoassay method integrating mixing, reaction, separation, and detection on-chip is described for the measurement of alpha-fetoprotein (AFP), a liver cancer marker in blood. Antibody-binding reagents, consisting of 245-bp DNA coupled anti-AFP WA1 antibody (DNA-WA1) and HiLyte dye-labeled anti-AFP WA2 antibody (HiLyte-WA2), and AFP-containing sample were filled into adjacent zones of a chip channel defined by the laminar flow lines of the microfluidic device using pressure-driven flow. The channel geometry was thus used to quantitatively aliquot the reagents and sample into the chip. DNA-WA1 was electrokinetically concentrated in the channel and sequentially transported through the AFP-sample zone and HiLyte-WA2 zone by ITP in such a manner that the AFP sandwich immune complex formation took place in the sample and HiLyte-WA2 zones. The sandwich AFP immune complex was then detected by LIF after CGE in a separation channel that was arranged downstream of the reaction channel. AFP was detected within 136 s with a detection sensitivity of 5 pM. The on-chip immunoassay described here, applying ITP concentration, in-channel reaction, and CGE separation, has the potential of providing a rapid and sensitive method for both clinical and research applications.     

Development of a two-step chromatography procedure that allows the purification of a high-purity anti-histone H1 monoclonal immunoglobulin M antibody with immunosuppressant activity

In organ transplantation, the development of a novel immunosuppressant free of the need for permanent administration and any serious side effects has eagerly been awaited. We have previously reported that an anti-histone H1 polyclonal antibody has immunosuppressant activity. Here we prepared an anti-histone H1 monoclonal antibody as an analytical tool to elucidate its mechanism of immunosuppression. The isotype of this monoclonal antibody was immunoglobulin M. A monoclonal antibody prepared for administration to organ transplantation model animals should not contain any allogenic proteins and should have high purity. Therefore, we conducted a two-step chromatography procedure, consisting of strong anion-exchange chromatography and gel filtration chromatography, to purify an anti-histone H1 monoclonal immunoglobulin M antibody from the serum-free culture supernatant of hybridomas. Consequently, we successfully purified the monoclonal antibody at 96%, a purification rate at which its administration to organ transplantation model animals is possible.     

Thermally responsive supramolecular nanomeshes for on/off switching of the rotary motion of F1-ATPase at the single-molecule level

The artificial regulation of protein functions is essential for the realization of protein-based soft devices, because of their unique functions conducted within a nano-sized molecular space. We report that self-assembled nanomeshes comprising heat-responsive supramolecular hydrogel fibers can control the rotary motion of an enzyme-based biomotor (F(1)-ATPase) in an on/off manner at the single-molecule level. Direct observation of the interaction of the supramolecular fibers with a microbead unit tethered to the F(1)-ATPase and the clear threshold in the size of the bead required to stop ATPase rotation indicates that the bead was physically blocked so as to stop the rotary motion of ATPase. The temperature-induced formation and collapse of the supramolecular nanomesh can produce or destroy, respectively, the physical obstacle for ATPase so as to control the ATPase motion in an off/on manner. Furthermore, this switching of the F(1)-ATPase motion could be spatially restricted by using a microheating device. The integration of biomolecules and hard materials, interfaced with intelligent soft materials such as supramolecular hydrogels, is promising for the development of novel semi-synthetic nano-biodevices.     

Crystal design of monometallic single-molecule magnets consisting of cobalt-aminoxyl heterospins

Five N-aryl-N-pyridylaminoxyls, which have no substituent (PhNOpy), one substituent (MeOPhNOpy and tert-BuPhNOpy) at the 4-position, and three substituents (TPPNOpy and TBPNOpy) at the 2, 4, and 6-positions of the phenyl ring, were prepared as new ligands for cobalt-aminoxyl heterospin systems. The 1:4 complexes, [Co(NCS)2(PhNOpy)4] (1), [Co(NCS)2(MeOPhNOpy)4] (2), [Co(NCS)2(tertBuPhNOpy)4] (3), [Co(NCS)2(TPPNOpy)4] (4), [Co(NCS)2(TBPNOpy)4] (5a), and [Co(NCO)2(TBPNOpy)4] (5b), were obtained as single crystals. The molecular geometry revealed by X-ray crystallography for all complexes except 4 is a compressed octahedron. In the crystal structure of 1, 2, and 3, the organic spin centers have various short contacts within 4 A with the neighboring molecules to form 3D and 2D spin networks. On the other hand, complexes 5a and 5b have no significant short intermolecular contacts, indicating that they are magnetically isolated. 1 and 2 behaved as a 3D antiferromagnet with a Neel temperature, T(N), of 22 K and as a weak 3D antiferromagnet with a T(N) of 2.9 K and a spin-flop field at 1.9 K, Hsp(1.9), of 0.7 kOe, respectively. 3 was a canted 2D antiferromagnet (a weak ferromagnet) with T(N) = 4.8 K and showed a hysteresis loop with a coercive force, Hc, of 1.3 kOe at 1.9 K. On the other hand, the trisubstituted complexes 4, 5a, and 5b functioned as single-molecule magnets (SMMs). 5b had an effective activation barrier, U(eff), value of 28 K in a microcrystalline state and 48 K in a frozen solution.     

Generation and suppression of 3-/4-functionalized benzynes using zinc ate base (TMP-Zn-ate): new approaches to multisubstituted benzenes

We present full details of our new methods for preparing functionalized benzynes with lithium di-alkyl(2,2,6,6-tetramethylpiperidino)zincate (R2Zn(TMP)Li) through deprotonative zincation as a key reaction. In this system, by choosing appropriate ligands for the zincate, either regioselective zincation of functionalized haloaromatics or the generation of substituted benzynes can be controlled in good yields with excellent chemoselectivity, using the same substrate. Zincation with (t)Bu2Zn(TMP)Li followed by electrophilic trapping or zincation with Me2Zn(TMP)Li followed by nucleophilic or diene trapping is shown to be a powerful tool for the chemoselective preparation of 1,2,3-/1,2,4-trisubstituted benzene derivatives. These methods offer far greater generality than previous methods for the synthesis of multifunctionalized benzenes. Computational/theoretical studies of the reaction mechanism of this unique benzyne formation indicated that preferential coordination of the dialkylzinc moiety of zincate to halogen is the reason for the reduced activation energy of the elimination, that is, for the formation of the benzyne. The role of the ligands on Zn in accelerating/decelerating the elimination is also discussed.