Optical properties of Au–Ag core–shell nanorods on glass and ITO substrates

Gold-silver core–shell nanorods were deposited on glass and ITO plates. SEM observations indicated that some of these nanorods were standing on the ITO plate. The extinction spectra of the plates were measured by varying the angles of incidence of p-polarized monitor light. Deconvolution of these spectra gave six bands in the visible region. The dependence of the peak intensities on the incident angles indicated that the bands at 390 and 420 nm originated from surface plasmon bands in the transverse direction of the nanorods.     

Blockade of inflammatory responses by a small-molecule inhibitor of the Rac activator DOCK2

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Highlights? CPYPP binds to DOCK2 DHR-2 domain and inhibits its catalytic activity ? CPYPP inhibits DOCK2-mediated Rac activation in cells ? The structural features of CPYPP required for its inhibitory effect were revealed ? CPYPP inhibits lymphocyte migration and activation in vitro and in vivo     

Two Paths Joining Given Vertices in 2k-Edge-Connected Graphs

Let k≥2 be an integer and G = (V(G), E(G)) be a k-edge-connected graph. For X⊆V(G), e(X) denotes the number of edges between X and V(G) − X. Let {s_i, t_i}⊆X_i⊆V(G) (i=1,2) and X₁∩X₂=∅. We here prove that if k is even and e(X_i)≤2k−1 (i=1,2), then there exist paths P₁ and P₂ such that P_i joins s_i and t_i, V(P_i)⊆X_i (i=1,2) and G − E(P₁∪P₂) is (k−2)-edge-connected (for odd k, if e(X₁)≤2k−2 and e(X₂)≤2k−1, then the same result holds [10]), and we give a generalization of this result and some other results about paths not containing given edges.     

一个新型碗状双核配合物的合成及结构表征

采用挥发法，在无水条件下合成了一个新型具有碗状结构的双核稀土金属配合物：[Y₂(L)(HL)(NO₃)₆(HCOO)]·3CH₃OH[L=1，3，5-三(1-咪唑基-亚甲基)-2，4，6-三甲基苯] (1)。并通过元素分析、FT-IR、电喷雾质谱及X-射线单晶衍射对其进行了表征。结构分析表明该化合物属于正交晶系，空间群为Pnnm，晶胞参数为a=1.952 42(15) nm，b=1.875 28(19) nm，c=1.682 25(15) nm，晶胞体积V=6.159 3(10) nm³，Z=4。在化合物1中，两个独立的Y(Ⅲ)均为九配位，并通过甲酸根桥联，而两个配体采用不同的构象作为二齿配体参与与Y(Ⅲ)的配位，一个为cis，cis，cis-构象，另一个为cis，trans，trans-构象。     

Noncanonical RNA Nucleosides as Molecular Fossils of an Early Earth—Generation by Prebiotic Methylations and Carbamoylations

The RNA‐world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth.     

Every 4k-edge-connected graph is Weakly 3k-linked

We prove:

1. Fork ≥ 2 andα = 0, 1, every (4k + 2α)-edge-connected graph is weakly (3k + 2α)-linked.
2. IfG is ak-edge-connected graph (k ≥ 2),s, t are vertices andf is an edge, then there exists a pathP betweens andt such thatf ? E(P) andG ? E(P) ? f is (k ? 2)-edge-connected, whereE(P) denotes the edge set ofP.

     

Synthesis and structural characterization of centrosymmetric multinuclear nickel(II) complexes with neutral tetradentate N6-ligand

A neutral tetradentate ligand L1 [L1?=?3,6-bis(pyrazol-1-yl)-pyridazine] reacts with Ni(ClO₄)₂·6H₂O and undergoes counterion exchange with PF ^?₆ to give di- and tetranuclear complexes [Ni₂(L1)₂(CH₃CN)₄](PF₆)₄·4H₂O (1) and [Ni₄(L1)₄(µ-OH)₄](ClO₄)₄·2H₂O (2), respectively. The presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base controls the nuclearity of the complex formation. Both complexes were structurally characterized by physicochemical and spectroscopic techniques. Their crystal structures revealed that both complexes are centrosymmetric and adopt slightly distorted octahedral geometry. Complex 1 crystallizes in monoclinic space group C2/c as the Ni(II) center is octahedrally bound to L1 in a trans-isomer arrangement. Complex 2 crystallizes in tetragonal space group I4₁/amd with four L1 and four hydroxy bridging ligands linked to Ni(II) center in cis-isomer arrangement. Cyclic voltammograms of complexes 1 and 2 were measured under Ar and CO₂. Under CO₂, the quasireversible peaks of both complexes become irreversible and a current enhancement occurs under reduction.

     

Separation of Semiconducting Single‐Walled Carbon Nanotubes by Using a Long‐Alkyl‐Chain Benzenediazonium Compound

We designed and synthesized 4‐dodecyloxybenzenediazonium tetrafluoroborate ( 1 ), which preferentially reacts with metallic single‐walled carbon nanotubes (SWNTs) by kinetic control. We first determined the suitable experimental conditions for the preferential reaction of 1 with individually dissolved SWNTs by monitoring the decrease in absorbance for the metallic SWNT in the range of 400–650 nm in the absorption spectrum of the SWNTs. The reacted SWNTs were thoroughly rinsed with THF to obtain THF‐insoluble SWNTs. The Raman spectrum of the THF‐insoluble SWNTs showed a strong peak near 180 cm^?1, which corresponds to a semiconducting breathing band. The metallic breathing bands (≈220 cm^?1) and Breit–Wingner–Fano (BWF) modes (1520 cm^?1) corresponding to the metallic SWNTs were much weaker than those of the pristine SWNTs. We also confirmed that metallic peaks in the range of 400–650 nm in the absorption spectrum of THF‐insoluble SWNTs that were individually dissolved in an aqueous micelle of sodium cholate were almost nondetectable. All the results indicate that the THF‐insoluble SWNTs are semiconducting.     

Daphnicyclidins J and K, unique polycyclic alkaloids from Daphniphyllum humile

Two Daphniphyllum alkaloids with unprecedented polycyclic skeletons, daphnicyclidins J (1) and K (2), have been isolated from the stems of Daphniphyllum humile, and the structures and relative stereochemistry were elucidated on the basis of spectroscopic data. The absolute stereochemistry of 1 was established by chemical correlation with a known-related alkaloid, daphnicyclidin D (3), through a modified Polonovski reaction.