Quantitative determination of paclitaxel and its metabolites, 6α‐hydroxypaclitaxel and p‐3′‐hydroxypaclitaxel,in human plasma using column‐switching liquid chromatography/tandem mass spectrometry

A column‐switching liquid chromatography/electrospray ionization tandem mass spectrometry to determine paclitaxel and its metabolites, 6α‐hydroxypaclitaxel and p‐3′‐hydroxypaclitaxel, in human plasma was developed. The analytical system had a Shim‐Pack MAYI‐ODS (10 × 4.6 mm i.d.) trapping column with deproteinization ability that concentrates analytes and removes water‐soluble components. This method covered a linearity range of 5–5000 ng/mL of concentrations in plasma for paclitaxel, a range of 0.87–870 ng/mL for 6α‐hydroxypaclitaxel and a range of 0.87–435 ng/mL for p‐3′‐hydroxypaclitaxel. The intra‐day precision and inter‐day precision of analysis were less than 11.1%, and the accuracy was within ±14.4% at concentrations of 5, 50, 500 and 5000 ng/mL for paclitaxel, 0.87, 8.7, 87 and 870 ng/mL for 6α‐hydroxypaclitaxel, and 0.87, 8.7, 87 and 435 ng/mL for p‐3′‐hydroxypaclitaxel. The total run time was 30 min. Our method was successfully applied to clinical pharmacokinetic investigation. Copyright © 2012 John Wiley & Sons, Ltd.     

X-ray diffraction analysis of the layer structure in a ferroelectric liquid crystal with a chiral nematic–chiral smectic C phase transition

A half-V-shaped switching ferroelectric liquid crystal (FLC) is a promising candidate for fast response displays. In the half-V FLC display, a liquid crystal with a chiral nematic–chiral smectic C phase transition is used, and the smectic layer is formed by cooling from N* to SmC* with an applied d.c. field. We studied the layer structure by means of X-ray measurements for two axes (ω and χ). By using a point-focused X-ray tube and optimizing the slit width, we succeeded in the two-axis measurement with a commercial X-ray system. The ω–χ profile of the half-V FLC showed two broad peaks in an arc-shaped high-intensity area. Our interpretation of this result is that the major part of the layer consists of a tilted-bookshelf structure and that the minor part consists of a near-bookshelf structure. Since optical microscopy observations on the half-V FLC cells showed a stripe-shaped texture, we consider that the coexistence of the tilted-bookshelf and the near-bookshelf structures forms the stripe-shaped patterns. The radius of the arc-shaped high-intensity area was nearly equal to the molecular tilt angle. This result can explain why the half-V FLC showed a desirable black appearance in spite of the stripe-shaped texture.     

New limit on time-reversal violation in beta decay

We report the results of an improved determination of the triple correlation DP·(p(e)×p(v)) that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the standard model. Our result is D=[-0.96±1.89(stat)±1.01(sys)]×10(-4). The corresponding phase between gA and gV is ?AV=180.013°±0.028° (68% confidence level). This result represents the most sensitive measurement of D in nuclear β decay.     

Fluorescence probe for lysophospholipase C/NPP6 activity and a potent NPP6 inhibitor

Nucleotide pyrophosphatases/phosphodiesterases (NPPs) are ubiquitous membrane-associated or secreted ectoenzymes that have a role in regulating extracellular nucleotide and phospholipid metabolism. Among the members of the NPP family, NPP1 and -3 act on nucleotides such as ATP, while NPP2, -6, and -7 act on phospholipids such as lysophosphatidylcholine and sphingomyelin. NPP6, a recently characterized NPP family member, is a choline-specific glycerophosphodiester phosphodiesterase, but its functions remain to be analyzed, partly due to the lack of highly sensitive activity assay systems and practical inhibitors. Here we report synthesis of novel NPP6 fluorescence probes, TG-mPC and its analogues TG-mPC(3)C, TG-mPC(5)C, TG-mPENE, TG-mPEA, TG-mPhos, TG-mPA, TG-mPMe, and TG-mPPr. Among the seven NPPs, only NPP6 hydrolyzed TG-mPC, TG-mPC(3)C, and TG-mPENE. TG-mPC was hydrolyzed in the cell lysate from NPP6-transfected cells, but not control cells, showing that it is suitable for use in cell-based NPP6 assays. We also examined the usefulness of TG-mPC as a fluorescence imaging probe. We further applied TG-mPC to carry out high-throughput NPP6 inhibitor screening and found several NPP6-selective inhibitors in a library of about 80,000 compounds. Through structure-activity relationship (SAR) analysis, we identified a potent and selective NPP6 inhibitor with an IC(50) value of 0.21 μM. Our NPP6-selective fluorescence probe, TG-mPC, and the inhibitor are expected to be useful to elucidate the biological function of NPP6.     

A Palladium‐Nanoparticle and Silicon‐Nanowire‐Array Hybrid: A Platform for Catalytic Heterogeneous Reactions

We report the development of a silicon nanowire array‐stabilized palladium nanoparticle catalyst, SiNA‐Pd. Its use in the palladium‐catalyzed Mizoroki‐Heck reaction, the hydrogenation of an alkene, the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β‐unsaturated ketone, and the C‐H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred‐mol ppb of palladium, reaching a TON of 2 000 000.     

Stereoselective Isomerization of Unsymmetrical Diallyl Ethers to Allyl (E)-Vinyl Ethers by a Cationic Iridium Catalyst

The stereoselective isomerization of unsymmetrical diallyl ethers to allyl (E)-vinyl ethers was carried out in the presence of a cationic iridium(I) catalyst. The catalyst prepared in situ by treating [Ir(cod)(PPh₂Me)₂]PF₆ with hydrogen was found to be an excellent catalyst to selectively isomerize the less substituted allyl group to an (E)-vinyl ether.     

Structural transition of pentacene monolayer on Ga bilayer: From brick-wall structure to herringbone pattern of molecular dimers

Utilizing the substrate of Ga bilayer grown on Si(1 1 1)-√3 × √3-Ga, we have investigated the structural transition of pentacene monolayer induced by moderate annealing. Short-range ordering has been observed in the monolayer pentacene deposited at room temperature. Annealing the sample at ∼350 K produced ordered pentacene monolayer with the “brick-wall” adsorption pattern. The STM images with sub-molecular resolution revealed that the orbital symmetry of the HOMO is reduced from D_2h to C_2v, due to the substrate-molecule interaction, while the deeper HOMO-1 orbital remains intact. Further annealing at ∼400 K led to the formation of molecular dimers as well as the structural transition from “brick-wall” packing to “herringbone” pattern.     

Dynamical stability of the BRS supersymmetry and the Gribov problem

The stability of the Becchi-Rouet-Stora supersymmetry is studied on the basis of a simple non-gauge model invariant under BRS supersymmetry. The Nambu-Goldstone theorem is stated and the spontaneous breakdown of the BRS supersymmetry is illustrated by the above non-gauge model. This indicates that the dynamical stability of BRS supersymmetry in non-abelian gauge theories should also be carefully examined, if one takes the Faddeev-Popov lagrangian as a basis of the formal canonical treatment. We show that a better understanding of the Gribov problem is required to establish the stability of the BRS supersymmetry in non-abelian gauge theories to non-perturbative accuracy.     

Design and synthesis of highly sensitive fluorogenic substrates for glutathione S-transferase and application for activity imaging in living cells

Here we report the development of fluorogenic substrates for glutathione S-transferase (GST), a multigene-family enzyme mainly involved in detoxification of endogenous and exogenous compounds, including drug metabolism. GST is often overexpressed in a variety of malignancies and is involved in the development of resistance to various anticancer drugs. Despite the medical significance of this enzyme, no practical fluorogenic substrates for fluorescence imaging of GST activity or for high-throughput screening of GST inhibitors are yet available. So, we set out to develop new fluorogenic substrates for GST. In preliminary studies, we found that 3,4-dinitrobenzanilide (NNBA) is a specific substrate for GST and established the mechanisms of its glutathionylation and denitration. Using these results as a basis for off/on control of fluorescence, we designed and synthesized new fluorogenic substrates, DNAFs, and a cell membrane-permeable variant, DNAT-Me. These fluorogenic substrates provide a dramatic fluorescence increase upon GST-catalyzed glutathionylation and have excellent kinetic parameters for the present purpose. We were able to detect nuclear localization of GSH/GST activity in HuCCT1 cell lines with the use of DNAT-Me. These results indicate that the newly developed fluorogenic substrates should be useful not only for high-throughput GST-inhibitor screening but also for studies on the mechanisms of drug resistance in cancer cells.