Iron–Copper Cooperative Catalysis in the Reactions of Alkyl Grignard Reagents: Exchange Reaction with Alkenes and Carbometalation of Alkynes

Iron–copper cooperative catalysis is shown to be effective for an alkene–Grignard exchange reaction and alkylmagnesiation of alkynes. The Grignard exchange between terminal alkenes (RCHCH₂) and cyclopentylmagnesium bromide was catalyzed by FeCl₃ (2.5 mol %) and CuBr (5 mol %) in combination with PBu₃ (10 mol %) to give RCH₂CH₂MgBr in high yields. 1-Alkyl Grignard reagents add to alkynes in the presence of a catalyst system consisting of Fe­(acac)₃, CuBr, PBu₃, and <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine to give β-alkylvinyl Grignard reagents. The exchange reaction and carbometalation take place on iron, whereas copper assists with the exchange of organic groups between organoiron and organomagnesium species through transmetalation with these species. Sequential reactions consisting of the alkene–Grignard exchange and the alkylmagnesiation of alkynes were successfully conducted by adding an alkyne to a mixture of the first reaction. Isomerization of Grignard reagents from 2-alkyl to 1-alkyl catalyzed by Fe–Cu also is applicable as the first 1-alkyl Grignard formation step

Lesson Study through Collaborative Action Research with a Team of Undergraduate Student Teachers and Graduate Students (1).

本研究では, アクションリサーチという手法によって, 実践と研究を統合して授業研究を行うことにより, 教育実習生の教科指導力と, 院生の授業観察力の向上をめざした。その結果, ある程度の成果を挙げることができた。院生は当初, 授業規律のような, 教科外の問題に視点を当てていたが, しだいに教科の内容に関する問題に着眼するようになっていき, 問題に対する対処法に関しても, 的確なアドバイスができるようになった。実習観察後に行った院生へのインタビューから次の仮説が浮かび上がってきた。 教科の専門性は, 専門教育で培われるものを土台として, そのうえに教科教育学的な方法論が位置することによって, ようやく獲得されるものではないだろうか。模擬授業や教育実習を積み重ねることだけでは獲得されないものであるといえよう

A specific single-stranded DNA induces a distinct conformational change in the nucleoid-associated protein HU

AbstractIn prokaryotic cells, genomic DNA forms an aggregated structure with various nucleoid-associated proteins (NAPs). The functions of genomic DNA are cooperatively modulated by NAPs, of which HU is considered to be one of the most important. HU binds double-stranded DNA (dsDNA) and serves as a structural modulator in the genome architecture. It plays important roles in diverse DNA functions, including replication, segregation, transcription and repair. Interestingly, it has been reported that HU also binds single-stranded DNA (ssDNA) regardless of sequence. However, structural analysis of HU with ssDNA has been lacking, and the functional relevance of this binding remains elusive.In this study, we found that ssDNA induced a significant change in the secondary structure of Thermus thermophilus HU (TtHU), as observed by analysis of circular dichroism spectra. Notably, this change in secondary structure was sequence specific, because the complementary ssDNA or dsDNA did not induce the change. Structural analysis using nuclear magnetic resonance confirmed that TtHU and this ssDNA formed a unique structure, which was different from the previously reported structure of HU in complex with dsDNA. Our data suggest that TtHU undergoes a distinct structural change when it associates with ssDNA of a specific sequence and subsequently exerts a yet-to-be-defined function