Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

Asymmetric amplification during self‐replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine‐5‐carbaldehyde is a unique example of this phenomenon. Crystallization of zinc alkoxides of this 5‐pyrimidyl alkanol and single‐crystal X‐ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.     

Identification and Purification of the CPD Photolyase in Vibrio parahaemolyticus RIMD2210633

Photoreactivation is an error‐free mechanism of DNA repair, utilized by prokaryotes and most eukaryotes and is catalyzed by specific enzymes called DNA photolyases. Photoreactivation has been reported in Vibrio parahaemolyticus WP28; however, information on photolyases in V. parahaemolyticus (V.p) strains has not been reported. This study examined the photoreactivation in V.p RIMD2210633. The photolyase responsible for repairing cyclobutane pyrimidine dimer (CPD) in DNA was identified, and the corresponding gene was determined as VPA1471. The protein was overexpressed in Escherichia coli and was purified for functional assessment in vitro. The mRNA level and protein expression level of this gene increased after ultraviolet A (UVA) illumination following ultraviolet C (UVC) irradiation. In vitro experiments confirmed that the protein encoded by VPA1471 could reduce the quantity of CPD in DNA. We designated the corresponding gene and protein of VPA1471 phr and Phr, respectively, although the function of two other photolyase/cryptochrome family members, VPA0203 and VPA0204, remains unclear. UV (ultraviolet) irradiation experiments suggest that these two genes possess some photorepairing ability. Therefore, we hypothesize that VPA0203 and VPA0204 encode (6‐4) photolyase in V. parahaemolyticus RIMD2210633.     

The first total synthesis and structural determination of antibiotics K1115 B1s (alnumycins)

K1115 B₁, isolated from the broth of Streptomyces species, was found to be a mixture of stereoisomers. Authors synthesized all stereoisomers of K1115 B₁ by convergent synthesis coupling a rhamnose derivative, an isobenzofuranone, and a chiral tetraol. Comparison of ¹H NMR spectra and optical rotations made it clear that the absolute structures of K1115 B_1α (the major isomer) and K1115 B_1β (the minor isomer) were (1R, 17S)- and (1R, 17R)-configurations, respectively. The optical rotations of the stereoisomers revealed that alnumycin, reported as the identical structure with K1115 B₁, might be another mixture of stereoisomers.     

Alkene isomerization/enamide-ene and diene metathesis for the construction of indoles, quinolines, benzofurans and chromenes with a chiral cyclopropane substituent

A synthetic method for bicyclic heterocycles, such as indole, benzofuran and chromene derivatives bearing a chiral cyclopropane at the 2-position, was established using isomerization of a terminal olefin and enamide-ene or diene metathesis. This route can also be applied to chiral 2-cyclopropylquinoline synthesis (both cis and trans).     

Surface-modified lead–zirconium-titanate system for solution-processed ferroelectric-gate thin-film transistors

We propose the use of a La₂O₃ (LO) film as the capping layer for improvement of a semiconductor/insulator interface in a solution-processed indium–tin–oxide (ITO) ferroelectric-gate thin-film transistor (FGT) device. It is demonstrated that the LO layer acts as a good barrier film not only for preventing the interdiffusion between the ITO semiconductor and lead–zirconium-titanate (PZT) insulator layers, but also for stabilizing the PZT surface structure. The fabricated FGT device exhibited high I _on/I _off, large M _w, high μ _FE and improved retention time of about 10⁹, 3.5 V, 7.94 cm²?V^?1?s^?1 and 1 day, respectively, which are comparable to or better than those obtained with FGTs fabricated by means of conventional vacuum processes. We also point out that the key origin of the interface improvement is likely due to the incorporation of La into the PZT system, forming a La surface-modified PZT system which is more stable than the pure PZT in terms of Pb volatility and formation of oxygen vacancies.     

Laser ablation synthesis of monodispersed magnetic alloy nanoparticles

Monodispersed CoPt alloy nanoparticles were synthesized by a pulsed laser ablation (PLA) technique coupled with a low-pressure operating differential mobility analyzer (LP-DMA). The CoPt alloy nanoparticles were generated by laser ablating a solid Co–Pt target. In CoPt alloy nanoparticles synthesized from a target with a Co composition of 75 at%, the nanoparticle surfaces were covered by an oxide layer and exhibited a core-shell structure. In contrast, no shell was observed in particles generated from a target with a Co:Pt ratio of 50:50 at%. According to an EDX analysis, the compositions of the individual nanoparticles were almost the same as that of the target material. Finally, the magnetic hysteresis loops of the CoPt alloy nanoparticles exhibited ferromagnetism.     

Impairment in S-phase entry of splenocytes of Parp-1 knockout mice

One immediate cellular response to DNA damage is the polyADP-ribosylation reaction by poly(ADP-ribose) polymerase-1 (Parp-1). The importance of Parp-1 has been established in many cellular processes, such as the maintenance of genomic stability, DNA repair and cell-death induction. Here, we established Parp-1^−/− mice of C57BL/6J congenic strain and characterized the role of Parp-1 in cell-cycle progression. In this study, we also improved a method to observe G0/G1 to S-phase transition of splenocytes and bone marrow cells prepared from mice. The cells were cultured and stimulated with mitogens (50 μM ionomycin/1 μM phorbol 12, 13-dibutyrate). We found that addition of a commercially available growth supportive reagent, BM Condimed ^RH1, greatly enhanced the transition of G0/G1 to the S-phase, which was determined by bromodeoxyuridine (BrdU) incorporation to DNA. Using this method, G0/G1 to the S-phase entry was measured using splenocytes derived from Parp-1^−/−, Parp-1^+/− and wild-type (Parp-1^+/+) mice. DNA synthesis in Parp-1^+/+ and Parp-1^+/− splenocytes started from day 1 after addition of mitogens, whereas that in Parp-1^−/− cells started from day 2. The peak of the S-phase was at day 2 in all genotypes and notably DNA synthesis in Parp-1^−/− cells was approximately halved compared to Parp-1^+/+ cells on day 2, 3 and 4. These results suggested that Parp-1 is involved in positive regulation of S-phase entry in quiescent mouse splenocytes.