Activation of the chicken Ig-β locus by the collaboration of scattered regulatory regions through changes in chromatin structure

A total of 10 B-lymphocyte-specific DNase I hypersensitive sites located in the chicken Ig-β locus were divided into four regions and combinations of deletions of these regions were carried out. A decrease in transcription of the Ig-β gene to <3% was demonstrated in cells with deletions in all four regions. The Ig-β chromatin was resistant to DNase I digestion in these cells. Thus, the collaboration is shown to convert the Ig-β chromatin from the condensed state to a relaxed state. H3 and H4 acetylation decreased to <8% but H3K4 hypermethylation was observed at the Ig-β promoter and exon 3. The collaboration of four regions had virtually no effect on CG hypomethylation in the region upstream the transcriptional start site. Accordingly, neither the DNase I general sensitive state in the Ig-β chromatin nor hyperacetylation of H3 and H4 histones in the promoter proximal region causes H3K4 di-methylation or CG hypomethylation in the promoter. From these analyses, a chromatin situation was found in which both an active state, such as enhanced H3K4 methylation, or CG hypomethylation, and an inactive state, such as DNase I resistance in the Ig-β chromatin or hypoacetylation of H3 and H4 histones in the Ig-β locus, coexist

Electrocatalytic activity and volatile product selectivity for nitrate reduction at tin-modified Pt(100), Pd(100) and Pd–Pt(100) single crystal electrodes in acidic media

We prepared Sn-modified Pt(100), Pd(100) and Pd–Pt(100) single crystal electrodes and investigated the nitrate reduction reaction (NO3RR) activity and the product selectivity for them using online electrochemical mass spectroscopy (OLEMS), also known as differential electrochemical mass spectroscopy (DEMS). OLEMS measurements allowed us to quantify volatile products of N2, N2O and NO and confirm the production of N2 at Sn/Pd(100) but not at Sn/Pt(100). Pd-doping to Pt(100) with a 3 atomic % increased the product selectivity for the NO3RR to N2. These results indicate that the presence of Pd in the (100) surface is the key to produce N2, which seems to be related to the hydrogen adsorption energy to the metal surface. The suppression of hydrogenation of intermediate species at the electrode surface could lead to the production of N2. This work will guide us to understand N2 production mechanism for the NO3RR and develop highly selective electrocatalysts for denitrification

Organocatalytic asymmetric domino Michael–Henry reaction for the synthesis of substituted bicyclo[3.2.1]octan-2-ones

This paper was submitted for publication in the journal "Chemical Communications" and the definitive version can be found at: http://dx.doi.org/10.1039/c3cc39165eThe first organocatalytic asymmetric reaction between 1,4-cyclohexanedione and nitroalkenes have been studied, affording bicyclo[3.2.1]octane derivatives containing four continuous stereogenic centres. The products were obtained through a domino Michael-Henry process as a single diastereoisomer with excellent enantioselectivities

Synthesis of a Heterometallic Trinuclear Cluster of Ruthenium and Platinum with a Linear Alignment

A heterobimetallic trinuclear complex of Ru and Pt in a linear alignment, {Cp*Ru­(H)₂}₂(Pt)­(μ-P^tBu₂)₂(μ-H)₂ (<b>2</b>; Cp* = η⁵-C₅Me₅), was synthesized via P–C bond scission upon the photolysis of Cp*Ru­(μ-H)₄RuCp* (<b>1</b>) in the presence of Pt­(P^tBu₃)₂. Complex <b>2</b> was alternatively synthesized by the reaction of <b>1</b> with Pt­(P^tBu₂H)₃, together with the formation of a triangular Ru₂Pt complex, (Cp*Ru)₂{Pt­(P^tBu₂H)}­(μ-P^tBu₂)­(μ-H)₃(H)₂ (<b>4</b>). X-ray diffraction experiments showed that the structure of <b>2</b> could be regarded as a dimer of [Cp*RuH₃(P^tBu₂)]⁻ fragments linked by a Pt²⁺ ion. In contrast to the relevant monometallic trihydrido complex of ruthenium, Cp*RuH₃(P^tR₃), terminal hydrides of <b>2</b> were readily substituted by CO and ethylene, leading to the formation of {Cp*Ru­(L)}₂(Pt)­(μ-P^tBu₂)₂(μ-H)₂ (<b>5</b>; L = CO, <b>6</b>; L = C₂H₄). Such high reactivity could be attributed to the facile formation of a coordinatively unsaturated intermediate owing to stabilization by bulky μ-P^tBu₂ moieties as well as electronic influence of the central Pt atom. In fact, terminal hydrides of <b>2</b> were readily removed upon evacuation, leading to the formation of tetra- and dihydrido complexes (Cp*Ru)­{Cp*Ru­(H)₂}­Pt­(μ-P^tBu₂)₂(μ-H)₂ (<b>3</b>) and (Cp*Ru)₂­Pt­(μ-P^tBu₂)₂(μ-H)₂ (<b>8</b>), consecutively. Upon hydrogenation, <b>3</b> and <b>8</b> were smoothly transformed into <b>2</b>. In contrast with the reactions of <b>2</b> with 2<i>e</i> donors, substitution at the Pt atom occurred in reactions with Ph₂SiH₂ and Et₂SiH₂, resulting in μ-silylene and μ-silyl complexes {Cp*Ru­(H)}­{Cp*Ru­(P^tBu₂H)}­Pt­(μ-P^tBu₂)­(μ-SiPh₂)­(μ-H)₂ (<b>9</b>) and {Cp*Ru­(H)₂}­{Cp*Ru­(P^tBu₂H)}­Pt­(μ-P^tBu₂)­(μ-η²-SiEt₂)­(μ-H)₂ (<b>10</b>), respectively. In these reactions, the μ-phosphido ligand bridging the Ru and Pt atoms was transformed into a terminal phosphine ligand at the peripheral Ru atom, alongside the formation of μ-silylene and μ-silyl ligands via reductive P–H bond formation

Stereoselective Approach to the Racemic Oxatetracyclic Core of Platensimycin

A highly stereoselective synthesis of the racemic oxatetracyclic core of platensimycin has been accomplished from a known bicyclic epoxy lactone by an 11-step sequence that involves a Diels–Alder cyclcoaddition to construct its <i>cis</i>-decalenone structural motif with complete regio- and stereoselectivity and a ring-closing metathesis to establish its whole carbon framework