Evaluation of robustness to surface conditions of the target factor analysis method for determining the dielectric function from reflection electron energy loss spectra: Application to GaAs

Target factor analysis (TFA) of a series of angle‐resolved reflection electron energy loss spectra (REELS) was recently demonstrated to be a useful method to determine bulk energy loss functions (ELFs), which by the TFA are separated from the surface‐loss structures of REELS. The dielectric function is then readily derived by Kramers–Kronig analysis of the ELF. The advantage of the method compared with other methods, which are also based on the analysis of REELS, is that the condition of the outermost surface region is unimportant because the excitations that occur there are removed by the TFA and ideally a pure bulk component is determined. Our method is thus particularly useful for determining the ELF from compound materials that are hard to clean without modifying the outermost atomic layers. In this paper, the robustness of the method was studied by applying it to three GaAs samples with different surface compositions caused by different surface cleaning methods. The results showed that when electrons of energy 3000–4500 eV were used, the resulting bulk ELFs were essentially identical except for small differences for the sample that had the largest thickness of the modified surface layer. It is concluded that this is a useful method, provided that the thickness of the modified layer is kept to a minimum by using shallow angle sputtering and by using REELS electrons at a sufficiently high energy that a major part of the electron trajectories are at a depth larger than the thickness of the modified surface layer. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly efficient DNA compaction mediated by an in vivo antitumor-active tetrazolato-bridged dinuclear platinum(II) complex

We investigated the effects of antitumor-active tetrazolato-bridged dinuclear platinum(II) complexes [{cis-Pt(NH(3))(2)}(2)(μ-OH)(μ-tetrazolato-N(1),N(2))](2+) (1) and [{cis-Pt(NH(3))(2)}(2)(μ-OH)(μ-tetrazolato-N(2),N(3))](2+) (2) on the higher-order structure of a large DNA molecule (T4 phage DNA, 166 kbp) in aqueous solution through single-molecule observation by fluorescence microscopy. Complexes 1 and 2 cause irreversible compaction of DNA through an intermediate state in which coil and compact parts coexist in a single DNA molecule. The potency of compaction is in the order 2 > 1 ? cisplatin. Transmission electron microscopic observation showed that both complexes collapsed DNA into an irregularly packed structure. Circular dichroism measurements revealed that the dinuclear platinum(II) complexes change the secondary structure of DNA from the B to C form. These characteristics of platinum(II) complexes are markedly different from those of the usual condensing agents such as spermidine(3+) and [Co(III)(NH(3))(6)](3+). The ability to cause DNA compaction by the platinum(II) complexes is discussed in relation to their potent antitumor activity.     

Hydrogen-bond-directed 2-D sheet assemblies of sulfamide derivatives: formation of giant vesicles with patchwork-like surface pattern

Sulfamide derivatives showed high ability to form hydrogen-bond-directed two-dimensional (2-D) sheet assemblies of nanometer thickness. Further, fine-tuning of the side chain structures and preparation conditions allowed for the formation of micrometer-sized giant vesicles of 4b in water by the simple injection method. IR and XRD studies indicated that 4b having tetradecyl and oxyethylene-terminated alkyl side chains formed hydrogen-bond-directed 2-D nanosheet pairs. SEM, AFM, and TEM observation of the dried vesicles revealed that the vesicle membrane was composed of several lamellar-stacked layers of 2-D nanosheets and showed a characteristic patchwork-like pattern on the surface.     

In vitro gene delivery mediated by lactosylated dendrimer (generation 3, G3)/��-cyclodextrin conjugates into hepatocytes

The purpose of this study is to evaluate in vitro gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 3, G3) conjugates with ??-cyclodextrin (??-CDE (G3)) bearing lactose (Lac-??-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier. Lac-??-CDE (G3, DSL 1.2) was found to have much higher gene transfer activity than ??-CDE (G3), Lac-??-CDE (G2, DSL 2.6) and Lac-??-CDEs (G3, DSL 2.6, 4.1 and 6.1) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R). Lac-??-CDE (G3, DSL 1.2) provided negligible cytotoxicity up to a charge ratio of 100 (carrier/pDNA) in HepG2 cells. These results suggest the potential use of Lac-??-CDE (G3, DSL 1.2) as a non-viral vector for gene delivery toward hepatocytes.     

Medicinal Flowers. XXXII. Structures of oleanane-type triterpene saponins, perennisosides VIII, IX, X, XI, and XII, from the flowers of Bellis perennis

Five new triterpene saponins perennisosides VIII (1), IX (2), X (3), XI (4), and XII (5) were isolated from the MeOH-eluated fraction of the methanolic extract from the flowers of Bellis perennis. The MeOH-eluted fraction of the methanolic extract from the flowers of B. perennis was found to inhibit gastric emptying in olive oil-loaded mice at a dose of 200 mg/kg, per os (p.o.). The stereostructures of 1-5 were elucidated on the basis of chemical and spectroscopic evidence.     

Garlicnin A from the fraction regulating macrophage activation of Allium sativum

Garlicnin A (1), a new stable, sulfur-containing compound isolated from a fraction of the acetone extracts of Allium sativum L. garlic bulbs, showed the potential to suppress tumor cell proliferation by inhibiting the polarization of M2 alternatively activated macrophages, and its structure was characterized as 3,4-dimethyl-5-(4,5-dithia-1E,7-octadiene)-tetrahydrothiophene-2-sulfoxide-S-oxide, on the basis of the results of spectroscopic analysis results.     

Magnetic properties of barium uranate Ba2U2O7

Unique magnetic properties of a ternary uranate Ba₂U₂O₇ are reported. Magnetic susceptibility measurements reveal that this compound undergoes a magnetic transition at 19 K. Below this temperature, magnetic hysteresis was observed. The results of the low-temperature specific heat measurements below 30 K support the existence of the second-order magnetic transition at 19 K. Ba₂U₂O₇ undergoes a canted antiferromagnetic ordering at this temperature. The magnetic anomaly which sets in at 58 K may be due to the onset of one-dimensional magnetic correlations associated with the linear chains formed by U ions. The analysis of the experimental magnetic susceptibility data in the paramagnetic temperature region gives the effective magnetic moment μ_eff=0.73 μ_B, the Weiss constant θ=−10 K, and the temperature-independent paramagnetic susceptibility χ_TIP=0.14×10⁻³ emu/mole.The magnetic susceptibility results and the optical absorption spectrum were analyzed on the basis of an octahedral crystal field model. The energy levels of Ba₂U₂O₇ and the crystal field parameters were determined.     

TTF-Annulated Silicon Phthalocyanine Oligomers and Their External-Stimuli-Responsive Orientational Ordering

Orientational control of functional molecules is essential to create complex functionalities as seen in nature; however, such artificial systems have remained challenge. Herein, we have succeeded in controlling rotational isomerism of μ-oxo silicon phthalocyanine (SiPc) oligomers to achieve an external-stimuli-responsive orientational ordering using intermolecular interactions of tetrathiafulvalene (TTF). In this system, three modes of orientations, free rotation, eclipsed conformation, and staggered conformation, were interconverted in response to the oxidation states of TTF, which varied interactions from association due to formation of mixed-valence TTF dimer to dissociation due to electrostatic repulsion between TTF dications. Furthermore, a stable performance of oligomers as a cathode material in a Li-ion battery proved that the one-dimensionally stacked, rotatable structure of SiPc oligomers is useful to control the orientation of functional molecules toward molecular electronics.     

Multivalent Ligands for Inducing Receptor-Receptor Interactions

To obtain enchanced and/or unique cellular responses to peptide hormones by simultaneous activation of two different receptor systems, chimera peptide hormones in which enkephalin (EK) is connected through sarcosine oligomer (n) to the message segment of neurotensin [NT(8–13)] were synthesized. Interaction of these two receptor systems was studied by receptor-binding assay and determination of cAMP and cGMP level in cytosol of NG108-15 cells. It was found that EK-12-NT(8- 13) induced specific cell response in terms of the second messenger level. The specific cell response was explained in terms of the enhancement of receptor-receptor interaction in cytosol due to activation of nearby occurring receptors of different kinds. It was also found that EK-12- NT(8-13) has a high affinity toward neurotensin receptor but a low affinity toward enkephalin receptor. To strengthen and prolong the activity of peptide hormones by simultaneous binding with two or more receptors in the target cell, enkephalin/lipid conjugates were immobilized on the surface of polymerized liposomes. It was found that multivalent ligands with a high receptor affinity were synthesized, which was sensibly influenced by the presence of a spacer chain connecting the enkephalin unit to the lipid part. It was found that the introduction of anionic charges to the polymerized liposomes strongly affected the receptor affinity of immobilized ligands.