The influence of out-of-plane disorder on the formation of pseudogap and Fermi arc in Bi2Sr2−xRxCuOy (R=La and Eu)

We found that the length of the Fermi arc decreases with increasing out-of-plane disorder by performing angle resolved photoemission spectroscopy (ARPES) measurements in the superconducting state of optimally doped R=La and Eu samples of Bi₂Sr_2−xR_xCuO_y. Since out-of-plane disorder stabilizes the antinodal pseudogap as was shown in our previous study of the normal state, the present results indicate that this antinodal pseudogap persists into the superconducting state and decreases the Fermi arc length. We think that the shrinkage of the Fermi arc reduces the superfluid density, which explains the large suppression of the superconducting transition temperature when out-of-plane disorder is increased.     

Element‐specific microtomographic imaging of Drosophila brain stained with high‐Z probes

An application of X‐ray microtomography to the Drosophila adult brain stained with colloidal gold and a platinum compound is described. The transparency of biological tissue to hard X‐rays enables tomographic visualization of the three‐dimensional structure of tissue entrails. Each high‐Z element was visualized as a three‐dimensional structure from the difference absorption coefficient image at the corresponding L_III absorption edge. The cortex of the optic lobe was selectively visualized by the specific adsorption of colloidal gold. The entire structure revealed by the platinum impregnation allowed the anatomical assignment of the gold‐stained structures. Selective staining and specific visualization of biological tissues at micrometer resolution should elucidate the three‐dimensional cellular organization essential for the understanding and application of biological microstructures.     

Search for the invisible decay of neutrons with KamLAND

The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the -shell energy level of (12)C nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n--> 3v or nn--> 2v. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n--> inv) > 5.8 x 10(29) years and tau (nn--> inv) > 1.4 x 10(30) years at 90% C.L. These results represent an improvement of factors of approximately 3 and >10(4) and over previous experiments.     

Chemical synthesis and isolation of UDP-2-deoxy glucose and galactose

2-Deoxy sugars are attractive compounds in synthetic chemistry with regard to reactivity and stereoselectivity. Moreover, their ability to inhibit enzymes and metabolism is significant in biology. In this study, uridine-5′-diphosphate (UDP)-2-deoxy glucose (11) and galactose (12) were synthesized chemically. These sugar donors for glycosyltransferases were obtained α-selectively via phosphorylation using thioglycosides, coupling reaction with uridine-5′-monophosphate (UMP)-morpholidate, and moderate deacetylation. Isolation was carried out by sequential silica-gel chromatography using two kinds of developing solvents in a refrigerator. The structures were elucidated from the NMR results. Investigation of stability showed that the synthesized UDP-2-deoxy sugars were hydrolyzed much faster in buffer (pH 4) than the natural UDP sugars.     

Real-time observation of the photoinduced structural change of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) by femtosecond fluorescence spectroscopy: a realistic potential curve of the Jahn-Teller distortion

In copper(I) complex [Cu(dmphen)(2)]+ (dmphen = 2,9-dimethyl-1,10-phenanthroline), a "flattening" structural change is induced with 1MLCT excitation, which is a prototype of the structural change accompanied with Cu(I)/Cu(II) conversion in copper complexes. Femtosecond and picosecond emission dynamics of this complex were investigated in solution at room temperature with optically allowed S(2) <-- S(0) photoexcitation. Time-resolved emission was measured in the whole visible region, and the lifetimes, intrinsic emission spectra, and radiative lifetimes of the transients were obtained by quantitative analysis. It was concluded that the initially populated S(2) state is relaxed with a time constant of 45 fs to generate the S1 state retaining the perpendicular structure, and the D(2d) --> D(2) structural change (the change of the dihedral angle between the two ligand planes) occurs in the S(1) state with a time constant of 660 fs. The intersystem crossing from the S(1) state to the T(1) state takes place after this structural distortion with a time constant of 7.4 ps. Importantly, the temporal spectral evolution relevant to the structural change clearly exhibited an isoemissive point around 675 nm. This manifests that there exists a shallow potential minimum at the perpendicular geometry on the S1 surface, and the S1 state stays undistorted for a finite period as long as 660 fs before the structural distortion. This situation is not expected for the structural change induced by the ordinary (pseudo-)Jahn-Teller effect, because the distortion should be induced by the spontaneous structural instability at the perpendicular structure. This result sheds new light on the present understanding on the structural change occurring in the metal complexes.     

Porous glass beads as stationary phase in supercritical fluid chromatography

Summary Porous glass beads were evaluated as the stationary phase in supercritical fluid chromatography using methanol or diethyl ether as the mobile phase. Separation of oligomers of styrene and methylphenylsiloxane were demonstrated by using a microcolumn packed with prous glass beads.     

Intermolecular [2+2+1] Carbonylative Cycloaddition of Aldehydes with Alkynes,and Subsequent Oxidation to γ‐Hydroxybutenolides by a Supported Ruthenium Catalyst

Intermolecular [2+2+1] carbonylative cycloaddition of aldehydes with alkynes and subsequent oxidation to γ‐hydroxybutenolides is achieved using a supported ruthenium catalyst. A ceria‐supported ruthenium catalyst promotes the reaction efficiently, even with an ambient pressure of CO or without external CO, thus giving the corresponding γ‐hydroxybutenolide derivatives in good to high yields. Moreover this catalyst can be reused with no loss of activity.     

Simple procedure for preparation of α-fluoro esters by fluorination of ester enol silyl ethers with perchloryl fluoride

Fluorination of ester enol silyl ethers in THF at room temperature using diluted perchloryl fluoride (FClO₃) in the presence of ca. 0.5 M eq. of t-BuNH₂ as an additive produced the corresponding α-fluoro esters in over 80% yields.     

A Pretreatment‐Free,Polymer‐Based Platform Prepared by Molecular Imprinting and Post‐Imprinting Modifications for Sensing Intact Exosomes

Exosomes are small (30–100 nm) membrane vesicles that serve as regulatory agents for intercellular communication in cancers. Currently, exosomes are detected by immuno‐based assays with appropriate pretreatments like ultracentrifugation and are time consuming (>12 h). We present a novel pretreatment‐free fluorescence‐based sensing platform for intact exosomes, wherein exchangeable antibodies and fluorescent reporter molecules were aligned inside exosome‐binding cavities. Such antibody‐containing fluorescent reporter‐grafted nanocavities were prepared on a substrate by well‐designed molecular imprinting and post‐imprinting modifications to introduce antibodies and fluorescent reporter molecules only inside the binding nanocavities, enabling sufficiently high sensitivity to detect intact exosomes without pretreatment. The effectiveness of the system was demonstrated by using it to discriminate between normal exosomes and those originating from prostate cancer and analyze exosomes in tear drops.     

Strong Positive Allosterism which Appears in Molecular Recognition with Cerium(IV) Double Decker Porphyrins: Correlation between the Number of Binding Sites and Hill Coefficients

Abstract

Cerium(IV) double decker porphyrins bearing one-to-four pairs of 4-pyridyl groups (3a, 3a′, 3bp, 3bd, 3c, and 3d) were synthesized from tetraarylporphyrins bearing mono-, bis-, tris-, and tetrakis(4-pyridyl) groups. In 3b bearing two pairs of 4-pyridyl groups, there exist two isomers in which the 4-pyridyl groups are either proximal or distal (3bp and 3bd, respectively). In a mixed solvent of dichloromethane: ethyl acetate (30:1 v/v), 3a′ bearing one pair of 4-pyridyl groups and three pairs of phenyl groups did not interact with any dicarboxylic acids whereas 3d bearing four pairs of 4-pyridyl groups interacted only with dicarboxylic acid guests with a dimethylene spacer [e.g., BOC-L-aspartic acid (L-4) and (1R,2R)-cyclohexane-1,2-dicarboxylic acid ((1R,2R)-5)]. Interestingly, the complexation process monitored by CD spectroscopy showed a positive homotropic allosterism which satisfied the Hill equation giving constants K = 2.63 × 1011M-4 and n = 3.9 for L-4 and K = 2.75 × 109 M-4 and n = 4.0 for (1R,2R)-5. The continuous variation plots (Job plots) also supported the formation of the 1:4 3d/dicarboxylic acid guest complexes. The results consistently indicate that four pairs of 4-pyridyl groups in 3d allosterically bind these guests. In 3d, the two porphyrin rings can still rotate, but once the rotation is suppressed by the first guest binding, the subsequent binding of the second, third and fourth guests can occur cooperatively. This is the origin of the present positive homotoropic allosterism. A similar positive homotropic allosterism was also observed for 3bp and 3bd with n = 1.5 and 1.7, respectively and 3c with n = 3.0. The X-ray crystallographic study of the 3d·[(1R,2R)-5]4 complex showed that the two porphyrin planes are warped outward to relax the electrostatic repulsion and chirally twisted. The two carboxylic acid groups form intermolecular hydrogen bonds (but not intramolecular bridge-type hydrogen bonds) with the pyridyl groups because of the close packing effect of rigid host 3d and rigid guest (1R,2R)-5. In conclusion, this is a rare example of positive homotropic allosterism in an artificial system which is frequently seen in nature where the biological events must be efficiently regulated in response to signals.