Spin-polarized Dirac-cone-like surface state with d character at W(110)

The surface of W(110) exhibits a Dirac-cone-like state with d character within a spin-orbit-induced symmetry gap. As a function of the wave vector parallel to the surface, it shows a nearly massless energy dispersion and a pronounced spin polarization, which is antisymmetric with respect to the Brillouin zone center. In addition, the observed constant energy contours are strongly anisotropic for all energies. This discovery opens new pathways to the study of surface spin-density waves arising from a strong Fermi surface nesting as well as d-electron-based topological properties.     

The isolation and structure elucidation of new cassane diterpene-acids from Caesalpinia crista L. (Fabaceae), and review on the nomenclature of some Caesalpinia species

New cassane diterpene-acids, neocaesalpins H and I, were isolated from the leaves of Caesalpinia crista (Fabaceae), and their structures were deduced on the basis of the spectroscopic and chemical basis. These compounds were characterized as having an alpha,beta-butenolide hemiacetal ring that is rare in nature. The lacking of 5-hydroxy group also distinguished neocaesalpins H and I from cassane diterpenes (caesalpins) occurring in other Caesalpinia species from the phytochemical viewpoint. The nomenclature of three Caesalpinia species was also reviewed, and it was found that some species belonging to the genus Caesalpinia are improperly named and should be changed to valid names.     

Determination of sulfates of androsterone and epiandrosterone in human serum using isotope diluted liquid chromatography-electrospray ionization-mass spectrometry

A promising liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) for analysis of the sulfates of 5alpha-androgen, androsterone and epiandrosterone (A-S and EpiA-S) in human serum was developed. The method was used to assess one of the markers of 5alpha-reductase activity of males including patients with prostate cancer (PC). After deproteinization with acetonitrile, the androgen sulfates and the internal standard, [7,7,16,16-2H4]dehydroepiandrosterone-S, were extracted from human serum using a solid-phase extraction cartridge and washed with hexane. The extract was reconstituted and applied to the LC/ESI-MS system operated in the selected ion monitoring mode. The method was validated over the range 0.02-5 microg/mL (A-S) and 0.005-1.5 microg/mL (EpiA-S) using 10 microL of human serum. The method was a concise procedure without chemical or enzymatic hydrolysis of the conjugates, purification by high-performance liquid chromatography and/or derivatization, and proved to be satisfactory in its reproducibility and accuracy. The levels of these androgen sulfates tended to decrease during aging, and the A-S levels in the sera obtained from both healthy males and patients with PC were correlated with their EpiA-S levels.     

Structural Fluctuation of Disilanyl Double‐Pillared Bisheteroarenes

Silacyclophanes possessing two disilanyl pillars were synthesized from tricyclic heteroarenes in one‐pot synthetic procedures. The step‐like anti structures of three congeners bearing two heteroarene units were revealed in single crystals by X‐ray crystallographic analysis. Depending on the structures of aromatic units, torsion angles at the disilanyl pillars altered to maintain the overall step‐like molecular structures. The structure, however, fluctuated between anti and syn conformers in a solution phase despite the presence of eight methyl groups on the ring periphery. The analysis of the coalescence temperature with NMR spectroscopy showed the fundamental energetics of the dynamics. The subtle structural differences affected the dynamic behavior of the silacyclophanes.     

Non-Sonogashira-type palladium-catalyzed coupling reactions of terminal alkynes assisted by silver(I) oxide or tetrabutylammonium fluoride

Palladium-catalyzed reaction of aryl and alkenyl halides with terminal alkynes in the presence of silver(I) oxide as an activator furnishes various arylated or alkenylated alkynes in good to excellent yields. The similar coupling reaction is also found to proceed using tetrabutylammonium fluoride (TBAF) or tetrabutylammonium hydroxide (TBAOH) as an activator.     

Novel stereoselective entry to 2'-beta-carbon-substituted 2'-deoxy-4'-thionucleosides from 4-thiofuranoid glycals

2'-Beta-methyl- and 2'-beta-hydroxymethyl-2'-deoxy-4'-thionucleosides have been synthesized through PhSeCl-mediated electrophilic glycosidation using 4-thiofuranoid glycals having carbon substituents at the C2-position as a glycosyl donor. Preparation of these glycals were carried out by means of the C2 lithiation of 1-chloro-4-thiofuranoid glycal with LTMP followed by the Birch reduction of the chlorine atom. [reaction: see text]     

Derivatization of neutral steroids to enhance their detection characteristics in liquid chromatography–mass spectrometry

This review article underlines the detection-oriented derivatization of neutral steroids in liquid chromatography-mass spectrometry (LC-MS). Steroids have strong biological activity at very low concentrations in target tissues and, therefore, the analysis of steroids in body fluids or tissues is necessary to elucidate the nature of the many endocrine disease processes and thus be useful for diagnosis and treatment. LC-MS has recently been used for steroid analysis because of its specificity and versatility, but the ionization efficiencies of most steroids are relatively low for the different ionization methods. Derivatization enhances the ionization efficiencies of steroids, leading to high sensitivity and specific detection. For electrospray ionization MS the introduction of permanently charged moieties or easily ionizable moieties effectively increases the sensitivity of detection of steroids. The introduction of moieties with proton affinity or electron affinity enhances the analyte signals in positive and negative atmospheric pressure chemical ionization MS, respectively.     

Development of a novel analytical method for determination of chondroitin sulfate using an in-capillary enzyme reaction

A novel analytical method for determination of total amount of chondroitin sulfate (CS) based on its conversion to desulfated chondro-disaccharide via an enzyme-catalyzed reaction, was developed. Using the in-capillary enzyme reaction, the method was also applied to the successful construction of an on-line analytical system. Within this system, electrophoretic migration was used to mix zones containing the enzyme mixture (chondroitinase ABC, chondro-4-sulfatase, chondro-6-sulfatase and 2-o-sulfatase) and the substrate (CS). The reaction was then allowed to proceed in the presence of a weak electric field and, finally, the product (desulfated chondro-disaccharide) of enzyme reaction migrated to the detector under the influence of an applied electric field. A polyvinyl alcohol-coated capillary was used to reduce protein adsorption. Desulfated chondro-disaccharide was successfully migrated toward the anode in 10 mM Tris-acetate buffer (pH 7.0) under reversed polarity and detected at 232 nm. The established method was validated and demonstrated to be applicable in the determination of total amount of CS in a commercial ophthalmic solution. No interference from the formulation excipients was observed. Good linearity was obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 100.0 to 100.5%, and from 0.2 to 0.6% of the relative standard deviation, respectively. Good agreement was obtained between the established method and traditional photometric method based on carbazole reaction. In this study, application of the method to disaccharide compositional analysis was also performed.     

Mesostructured organosilica with a 9-mesityl-10-methylacridinium bridging unit: photoinduced charge separation in the organosilica framework

Polycondensation of 9-mesityl-10-methylacridinium-bridged organosilane in the presence of a nonionic surfactant yielded a mesostructured organosilica solid with a functional framework that exhibited long-lived photoinduced charge separation.