Two acridones and two coumarins from the roots of Paramignya trimera

Two acridones, paratrimerins C (1) and D (2), and two coumarins, paratrimerins E (3) and F (4), were isolated from the CHCl₃ and EtOAc extracts of Paramignya trimera (Rutaceae), together with twelve known compounds (5–16). Their structures were elucidated on the basis of spectroscopic data. All isolated compounds possessed significant α-glucosidase inhibitory activity in a concentration-dependent manner, and showed more potent inhibitory activity, with IC₅₀ values ranging from 14.6 to 112.2 μM, than the positive control acarbose (IC₅₀, 214.5 μM). The biosynthesis of the isolated coumarins and acridones was proposed.     

Formation of abnormal dual‐peak profiles in large tilt angle boron implantation

Large tilt angle (LTA) implantation has been employed in Si manufacturing processes in many applications, such as lightly doped drain and halo implant. The depth profile of boron ions usually consists of only single peak at incident angle of 0° with respect to the perpendicular of the silicon surface. However, an abnormal dual‐peak profile was observed at LTA (>40°) with incident energy of 160 keV. By using a Monte Carlo method to simulate the ion implant process, it was found that the projected range of boron ions agrees completely with the formation of the first peak position that is shallower in depth, while the cause for the second peak that corresponds with a depth much deeper in the Si substrate was unknown. During the simulation, it was also found that when the tilt angle was increased, the sputtering yields and Si displacements increased significantly, and this phenomenon indicates that during LTA implantation, Si damage may not be negligible anymore. The Si damage effect that was as due to either low Si density or transient Si displacement in the simulation could have led to partial incident boron ions penetrating much deeper into the Si substrate and thus, caused the emergence of the second peak. Copyright © 2016 John Wiley & Sons, Ltd.     

Flexural behavior of strain-softening solids

The flexural behavior of a beam is investigated in an attempt to establish a correlation between the tensile and bending properties of strain-softening solids. Given the complete uniaxial stress—strain relations, including the post-peak tension-softening portion, it is possible to predict the flexural behavior in moment—curvature and load—deflection relations. The results indicate that strain-softening gives rise to enhanced bending strength in agreement with experimental data. Conversely, given the bending responses together with the softening characteristics the complete tensile behavior can be determined. Since bending experiments are easier to perform than uniaxial tensile tests, this well-defined correlation provides a feasible means to obtain the entire tensile behavior of strain-softening solids such as concrete, rocks and ceramics.     

Light-enhanced catalysis by pyridoxal phosphate-dependent aspartate aminotransferase

The mechanisms of pyridoxal 5'-phosphate (PLP)-dependent enzymes require substrates to form covalent "external aldimine" intermediates, which absorb light strongly between 410 and 430 nm. Aspartate aminotransferase (AAT) is a prototypical PLP-dependent enzyme that catalyzes the reversible interconversion of aspartate and α-ketoglutarate with oxalacetate and glutamate. From kinetic isotope effects studies, it is known that deprotonation of the aspartate external aldimine C(α)-H bond to give a carbanionic quinonoid intermediate is partially rate limiting in the thermal AAT reaction. We show that excitation of the 430-nm external aldimine absorption band increases the steady-state catalytic activity of AAT, which is attributed to the photoenhancement of C(α)-H deprotonation on the basis of studies with Schiff bases in solution. Blue light (250 mW) illumination gives an observed 2.3-fold rate enhancement for WT AAT activity, a 530-fold enhancement for the inactive K258A mutant, and a 58600-fold enhancement for the PLP-Asp Schiff base in water. These different levels of enhancement correlate with the intrinsic reactivities of the C(α)-H bond in the different environments, with the less reactive Schiff bases exhibiting greater enhancement. Time-resolved spectroscopy, ranging from femtoseconds to minutes, was used to investigate the nature of the photoactivation of C(α)-H bond cleavage in PLP-amino acid Schiff bases both in water and bound to AAT. Unlike the thermal pathway, the photoactivation pathway involves a triplet state with a C(α)-H pK(a) that is estimated to be between 11 and 19 units lower than the ground state for the PLP-Val Schiff base in water.     

Isolation of chemical constituents from Enicosanthum cupulare (King) Airy-Shaw

Six chemical constituents were isolated from Enicosanthum cupulare (King) Airy-Shaw. The structures of the isolated compounds were determined using 1D, 2D-NMR and were found to be identical to those previously reported for these compounds. Three aporphine alkaloids, O-methylmoschatoline, liriodenine and oxostephanine were isolated from this plant for the first time. In addition, we examined the effects of these compounds on melanogenesis in murine B16 melanoma cells; O-methylmoschatoline increased melanin content in these cells.     

1,4-Addition of silicon dienoates to α,β-unsaturated aldehydes catalyzed by in situ-generated silicon Lewis acid

In situ-generated silyl methide species (R(3)Si-CTf(2)R') effectively catalyzed the reaction of β-substituted α,β-unsaturated aldehydes with silicon dienoates such as 3-bromo-2-TESO-furan to give the corresponding γ-adducts with excellent 1,4-selectivity and good anti selectivity.     

Degradation of hydroxymaleimide in 2-propanol by irradiation of energetic heavy ions (II)—N2-saturated system

Hydroxymaleimide was irradiated in N₂-saturated 2-propanol solutions by high-energy heavy ions over a wide range of LET values. The differential G-values of the degradation of hydroxymaleimide by irradiation with the heavier ions were lower than those of the lighter ions for the same LET value. An opposite result obtained in the air-saturated system. The degradation efficiency was 1.5 times higher, when the dose rate was 1/10 times lower. When irradiated at an LET value lower than 8 eV/nm, the G-values converged to a value less than that obtained by γ-irradiation.     

Precise and global identification of phospholipid molecular species by an Orbitrap mass spectrometer and automated search engine Lipid Search

In the present research, we have established a new lipidomics approach for the comprehensive and precise identification of molecular species in a crude lipid mixture using a LTQ Orbitrap mass spectrometer (MS) and reverse-phase liquid chromatography (RPLC) combination with our newly developed lipid search engine “Lipid Search”. LTQ Orbitrap provides high mass accuracy MS spectra by Fourier-transform (FT) mass spectrometer mode and can perform rapid MSⁿ by ion trap (IT) mass spectrometer mode. In this study, the negative ion mode was selected to detect fragment ions from phospholipids, such as fatty acid anions, by MS2 or MS3. We selected the specific detection approach by neutral loss survey-dependent MS3, for the identification of molecular species of phosphatidylcholine, sphingomyelin and phosphatidylserine. Identification of molecular species was performed by using both the high mass accuracy of the mass spectrometric data obtained from FT mode and structural data obtained from fragments in IT mode. Some alkylacyl and alkenylacyl species have the same m/z value as molecular-related ions and fragment ions, thus, direct acid hydrolysis analysis was performed to identify alkylacyl and alkenylacyl species, and then the RPLC–LTQ Orbitrap method was applied. As a result, 290 species from mouse liver and 248 species from mouse brain were identified within six different classes of phospholipid, only those in manually detected and confirmed. Most of all manually detected mass peaks were also automatically detected by “Lipid Search”. Adding to differences in molecular species in different classes of phospholipids, many characteristic differences in molecular species were detected in mouse liver and brain. More variable number of saturated and monounsaturated fatty acid-containing molecular species were detected in mouse brain than liver.     

Equivalent contributing depth investigated by a lateral wave with axial transmission in viscoelastic cortical bone

Cortical bone is a viscoelastic heterogeneous medium which may be assessed with axial transmission. This work aims at evaluating the average depth investigated by the lateral wave for radial variations of material properties in relatively thick cortical bone. The equivalent contributing depth (ECD) is derived from the finite element simulation results for spatial variations of a viscoelastic coefficient (η(11)) and of porosity. A value of ECD equal to around 1.6 mm is obtained for a spatial variation of η(11). The method fails to predict accurate values of the ECD for a spatial variation of porosity, because all parameters vary simultaneously.     

Role of Ti 3d carriers in mediating the ferromagnetism of Co∶TiO2 anatase thin films

We study the surface and bulk electronic structure of the room-temperature ferromagnet Co∶TiO(2) anatase films using soft- and hard-x-ray photoemission spectroscopy with probe sensitivities of ～1 and ～10 nm, respectively. We obtain direct evidence of metallic Ti(3+) states in the bulk, which get suppressed to give a surface semiconductor, thus indicating the difference in electronic structure between surface and bulk. X-ray absorption and resonant photoemission spectroscopy reveal Ti(3+) electrons at the Fermi level (E(F)) and high-spin Co(2+) electrons occurring away from E(F). The results show the importance of the charge neutrality condition: Co(2+)+V(O)(2-)+2Ti(4+)?Co(2+)+2Ti(3+) (V(O) is oxygen vacancy), which gives rise to the elusive Ti 3d carriers mediating ferromagnetism via the Co 3d-O 2p-Ti 3d exchange interaction pathway of the occupied orbitals.