Electron emission from naphthacene crystal due to the impact of argon and krypton metastable atoms

Energy distributions of electrons emitted from polycrystalline naphthacene due to the impact of metastable argon or krypton atoms were measured. The energy distribution peaks, except for large peaks appearing near zero eV, correspond to the kinetic energies estimated from photoelectron spectra on the assumption that the excitation energies of the metastable atoms are transferred to the electrons in the valence bands. The results are interpreted as the occurrence of Penning ionization (Auger de-excitation) on the naphthacene surface.     

Effect of acid-base properties on copper catalysts for hydrogenation of carbon dioxide

Acidic or basic components as co-catalysts were added to the Cu-based catalysts for hydrogenation of CO₂. Effects of acid-base properties on the catalytic activity and methanol selectivity are discussed.     

Self-assembled monolayer electrode of a diiron complex with a phenoxo-based dinucleating ligand: observation of molecular oxygen adsorptionldesorption in aqueous media

The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)amino-methyl-4-aminophenol (1), and its Fe2(II) complex, [Fe2(II)(1)(PhCOO)2](CF3SO3) (2), were prepared and 2 deposited on the Au surface (2/Au) is much more stable than in solution and exhibits redox behavior in aqueous media as well as reversible adsorption/desorption of oxygen at room temperature.     

The UPS: a promising target for breast cancer treatment

Abstract

During the past decade, progress in endocrine therapy and the use of trastuzumab has significantly contributed to the decline in breast cancer mortality for hormone receptor-positive and ERBB2 (HER2)-positive cases, respectively. As a result of these advances, a breast cancer cluster with poor prognosis that is negative for the estrogen receptor (ESR1), the progesterone receptor (PRGR) and ERBB2 (triple negative) has come to the forefront of medical therapeutic attention. DNA microarray analyses have revealed that this cluster is phenotypically most like the basal-like breast cancer that is caused by deficiencies in the BRCA1 pathways. To gain further improvements in breast cancer survival, new types of drugs might be required, and small molecules targeting the ubiquitin proteasome system have moved into the spotlight. The success of bortezomib in the treatment of multiple myeloma has sent encouraging signals that proteasome inhibitors could be used to treat other types of cancers. In addition, ubiquitin E3s involved in ESR1, ERBB2 or BRCA1 pathways could be ideal targets for therapeutic intervention. This review summarizes the ubiquitin proteasome pathways related to these proteins and discusses the possibility of new drugs for the treatment of breast cancers.

Publication history

Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).

     

Temperature-dependent fluorescence lifetime of a fluorescent polymeric thermometer, poly(N-isopropylacrylamide), labeled by polarity and hydrogen bonding sensitive 4-sulfamoyl-7-aminobenzofurazan

Fluorescent molecular thermometers showing temperature-dependent fluorescence lifetimes enable thermal mapping of small spaces such as a microchannel and a living cell. We report the temperature-dependent fluorescence lifetimes of poly(NIPAM-co-DBD-AA), which is a random copolymer of N-isopropylacrylamide (NIPAM) and an environment-sensitive fluorescent monomer (DBD-AA) containing a 4-sulfamoyl-7-aminobenzofurazan structure. The average fluorescence lifetime of poly(NIPAM-co-DBD-AA) in aqueous solution increased from 4.22 to 14.1 ns with increasing temperature from 30 to 35 degrees C. This drastic change in fluorescence lifetime (27% increase per 1 degrees C) is the sharpest ever reported. Concentration independency, one of the advantages of fluorescence lifetime measurements, was seen in average fluorescence lifetime (13.7 +/- 0.18 ns) of poly(NIPAM-co-DBD-AA) at 33 degrees C over a wide concentration range (0.005-1 w/v%). With increasing temperature, polyNIPAM units in poly(NIPAM-co-DBD-AA) change their structure from an extended form to a globular form, providing apolar and aprotic environments to the fluorescent DBD-AA units. Consequently, the environment-sensitive DBD-AA units translate the local environmental changes into the extension of the fluorescence lifetime. This role of the DBD-AA units was revealed by a study of solvent effects on fluorescence lifetime of a model environment-sensitive fluorophore.     

In situ conductance measurements for alignments of silica particles under alternating electric fields

The alignments of silica particles formed in sinusoidal electrical fields of 1 kHz were assessed using an optical microscope with measuring the electric conductance of a silica dispersion between two Pt electrodes in a vitreous silica glass cell. We confirmed that the electric conductance of the silica dispersion between the two electrodes in the cell reflected the surface conductance of the silica particles settling at the bottom of the cell. More interestingly, we observed that the electric conductance of the silica dispersion in the cell increased when pearl chains of the silica particle were formed along the direction of the electric field. However, no clear change in the electric conductance of the dispersion was observed at higher electric field strengths where a transition from pearl chains to zigzag band patterns and circulating movements of the silica particles in the zigzag bands formed.     

Formation of 4H-1,2-benzoxazines by intramolecular cyclization of nitroalkanes. Scope of aromatic oxygen-functionalization reaction involving a nitro oxygen atom and mechanistic insights

In this paper, we deal with the scope and mechanism of the strong Br?nsted acid-catalyzed intramolecular cyclization reaction of methyl 3-aryl-2-nitropropionates to give 4H-1,2-benzoxazines. This reaction can be regarded as an oxygen functionalization of the aromatic ring wherein the oxygen atom is derived from the nitro group in the molecule, and it is favored by the presence of electron-withdrawing groups on the benzene ring. The reaction rate is strongly influenced by the acidity of the reaction medium, and the methyl ester group on the alpha-carbon atom with respect to the nitro group facilitates deprotonation at the alpha-position to give aci-nitro species in situ. Some correlation was found between the electron-withdrawing ability of the substituents on benzene, represented in terms of Hammett's sigma p value of the substituents, and the rate of disappearance of the starting substrate leading to the product in trifluoromethanesulfonic acid (TFSA)/trifluoroacetic acid (TFA) medium. This would be because the acidity of the alpha-proton with respect to the nitro group is influenced by the substituents on the benzene ring. Experimentally, we excluded the 6pi electrocyclization mechanism involving deprotonation of the benzyl proton of the protonated aci-nitro species. Alternative cyclization mechanisms involving equilibrating monocationic aci-nitro species bearing O-protonated ester carbonyl group and O-protonated aci-nitro species were calculated to be highly energetically unfavorable. Diprotonated or protosolvative species can reduce the activation energy significantly, and this is consistent with the observed acidity-dependent nature of the cyclization.     

Superacid-catalyzed intramolecular cyclization reaction of arylcyanopropionate: geminal substitution effect on superelectrophilicity

We present superacid-catalyzed intramolecular cyclization reactions of arylcyanopropionates to give cyclized five- and six-membered beta-enamino esters in moderate to high yields. Known intramolecular ring-closing reactions of protonated nitrile to aromatic carbon atom are limited to the 6-membered case. Interestingly, a significant synergistic increase of reactivity of the cyano functionality was observed, and the cyano nitrogen atom was converted into an amino group, when an ester group was present in a geminal arrangement. Deuterium exchange experiments excluded the involvement of deprotonation of the alpha-proton in the cyclization process. The acidity dependence of the cyclization reactions and (13)C NMR studies of a model compound, methyl cyanoacetate, in various acidic media were consistent with the involvement of the O, N-diprotonated dication of methyl cyanoacetate, a distonic dication, in strong acid, and this is considered to be the de facto electrophile in the present cyclization reaction of arylcyanopropionates.     

Nonplanar structures of thioamides derived from 7-azabicyclo[2.2.1]heptane. Electronically tunable planarity of thioamides

X-ray crystallographic analysis showed that N-thiobenzoyl-7-azabicyclo[2.2.1]heptane displays marked nonplanarity of the thioamide (1a, alpha = 167.1 degrees and |tau| = 11.2 degrees) as compared with the corresponding monocyclic pyrrolidine thioamide (2a, alpha = 174.7 degrees and |tau| = 3.9 degrees). In a series of para-substituted or unsubstituted thioaroyl-7-azabicyclo[2.2.1]heptanes (1a-1h), the planarity of the thioamide depended significantly on the electronic nature of the substituent; for example, in the p-nitro-substituted compound, planarity was substantially restored (1h, alpha = 175.2 degrees and |tau| = 0.1 degrees). In solution, increasing electron-withdrawing character of the aromatic substituent was associated with a larger rotational barrier of the bicyclic thioamides, as determined by means of variable-temperature (1)H NMR spectroscopy and line shape analysis. The reduced rotational barrier, that is, reduced enthalpy of activation (DeltaH(double dagger)) for thioamide rotation, of 1a as compared with that of 2a in nitrobenzene-d5 is consistent with the postulate that 1a assumes a nonplanar thioamide structure in solution. These results indicate that the planarity of thioamides based on 7-azabicyclo[2.2.1]heptane is controlled by electronic factors in the solid phase and in solution.