2',5,7-Trihydroxy-4',5'-(2,2-dimethylchromeno)-8-(3-hydroxy-3-methylbutyl) flavanone purified from Cudrania tricuspidata induces apoptotic cell death of human leukemia U937 cells

Cellular DNA topoisomerase I is an important target in cancer chemotherapy. A chloroform extract of the root barks of Cudrania tricuspidata showed an inhibitory effect on mammalian DNA topoisomerase I. The topoisomerase I inhibitory compound was purified and identified as 2',5,7-trihydroxy-4',5'-(2,2-dimethylchromeno)-8-(3-hydroxy-3-methylbutyl) flavanone. The compound, temporarily designated as PKH-3, was shown to inhibit the activity of topoisomerase I with IC50 about 1.0 mM. Concentration of 10 microM PKH-3 caused 50% growth inhibition of human cancer cell U937. PKH-3-induced cell death was characterized with the cleavage of poly(ADP-ribose) polymerase (PARP) and pro-caspase 3. Furthermore, PKH-3 induced the fragmentation of DNA into multiples of 180 b.p. (an apoptotic DNA ladder), indicating that the inhibitor triggered apoptosis. This induction of apoptosis by PKH-3 was also confirmed using flow cytometry analysis. Taken together, these results suggest that PKH-3 may function by inhibiting oncogenic disease, at least in part, through the inhibition of topoisomerase I activity.     

Anti-Osteoporotic Effects of n-trans-Hibiscusamide and Its Derivative Alleviate Ovariectomy-Induced Bone Loss in Mice by Regulating RANKL-Induced Signaling

Osteoporosis is characterized by the deterioration of bone structures and decreased bone mass, leading to an increased risk of fracture. Estrogen deficiency in postmenopausal women and aging are major factors of osteoporosis and are some of the reasons for reduced quality of life. In this study, we investigated the effects of n-trans-hibiscusamide (NHA) and its derivative 4-O-(E)-feruloyl-N-(E)-hibiscusamide (HAD) on receptor activator of nuclear factor kappa-Β (NF-κB) ligand (RANKL)-induced osteoclast differentiation and an ovariectomized osteoporosis mouse model. NHA and HAD significantly inhibited the differentiation of osteoclasts from bone marrow-derived macrophages (BMMs) and the expression of osteoclast differentiation-related genes. At the molecular level, NHA and HAD significantly downregulated the phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules. However, Akt and NF-κB phosphorylation was inhibited only after NHA or HAD treatment. In the ovariectomy (OVX)-induced osteoporosis model, both NHA and HAD effectively improved trabecular bone structure. C-terminal telopeptide (CTX), a bone resorption marker, and RANKL, an osteoclast stimulation factor, were significantly reduced by NHA and HAD. The tartrate-resistant acid phosphatase (TRAP)-stained area, which indicates the osteoclast area, was also decreased by these compounds. These results show the potential of NHA and HAD as therapeutic agents for osteoporosis.     

16S rRNA gene-based metagenomic analysis reveals differences in bacteria-derived extracellular vesicles in the urine of pregnant and non-pregnant women

Recent evidence has indicated that bacteria-derived extracellular vesicles (EVs) are important for host–microbe communication. The aims of the present study were to evaluate whether bacteria-derived EVs are excreted via the urinary tract and to compare the composition of bacteria-derived EVs in the urine of pregnant and non-pregnant women. Seventy-three non-pregnant and seventy-four pregnant women were enrolled from Dankook University and Ewha Womans University hospitals. DNA was extracted from urine EVs after EV isolation using the differential centrifugation method. 16S ribosomal RNA (16S rRNA) gene sequencing was performed using high-throughput 454 pyrosequencing after amplification of the V1–V3 region of the 16S rDNA. The composition of 13 taxa differed significantly between the pregnant and non-pregnant women. At the genus level, Bacillus spp. EVs were more significantly enriched in the urine of the pregnant women than in that of the non-pregnant women (45.61% vs 0.12%, respectively). However, Pseudomonas spp. EVs were more dominant in non-pregnant women than in pregnant women (13.2% vs 4.09%, respectively). Regarding the compositional difference between pregnant women with normal and preterm delivery, EVs derived from Ureaplasma spp. and the family Veillonellaceae (including Megasphaera spp.) were more abundant in the urine of preterm-delivered women than in that of women with normal deliveries. Taken together, these data showed that Bacillus spp. EVs predominate in the urine of pregnant women, whereas Pseudomonas spp. EVs predominate in the urine of non-pregnant women; this suggests that Bacillus spp. EVs might have an important role in the maintenance of pregnancy.     

Hierarchical Self‐Assembled Photo‐Responsive Tubisomes from a Cyclic Peptide‐Bridged Amphiphilic Block Copolymer

Typically, the morphologies of the self‐assembled nanostructures from block copolymers are limited to spherical micelles, wormlike micelles and vesicles. Now, a new generation of materials with unique shape and structures, cylindrical soft matter particles (tubisomes), are obtained from the hierarchical self‐assembly of cyclic peptide‐bridged amphiphilic diblock copolymers. The capacity of obtained photo‐responsive tubisomes as potential drug carriers is evaluated. The supramolecular tubisomes pave an alternative way for fabricating polymeric tubular structures, and will expand the toolbox for the rational design of functional hierarchical nanostructures.     

Observation of superradiant amplification of ultrashort laser pulses in a plasma

We demonstrate the amplification of a femtosecond signal pulse in an underdense plasma by a novel mechanism called superradiant amplification. The pulse is amplified by a counterpropagating few picosecond long pump pulse. In the superradiant regime, the ponderomotive forces exceed the electrostatic forces and arrange the plasma electrons to reflect the pump light into the signal pulse. We found a significant amplification in energy and intensity. The time structure of the amplified signal pulse carries intrinsic features of the superradiant regime. Sub-10-fs pulses of petawatt power appear feasible.     

Efficient coupling of hybrid optical waveguide with a sharp bend structure for high integration

A hybrid optical waveguide with a \(90^{\circ }\) sharp bend comprising a dielectric straight waveguide, a tapered dielectric strip waveguide, and a microscale metal gap waveguide is proposed, modeled, fabricated, and characterized with the aim of improving the efficiency of light coupling between the dielectric and plasmonic waveguides. The simulation result using the full-vector finite-difference time domain shows a total transmissivity of about 63 % at a wavelength of 1,550 nm. A set of hybrid optical waveguide with a \(90^{\circ }\) bend is fabricated via the two-step photolithography and a metal lift-off process. From the measured result for the characteristics of the fabricated hybrid optical waveguide, the transmission loss was estimated to be about 17 dB, which is in stark contrast with the simulation value. Nevertheless, such a novel coupling scheme may be of potential use in high-density photonic integration applications.     

Contact angle hysteresis: study by dynamic cycling contact angle measurements and variable angle spectroscopic ellipsometry on polyimide

The phenomenon of contact angle hysteresis was studied on smooth films of polyimide, a polymer type used in the microelectronic industry, by dynamic cycling contact angle measurements based on axisymmetric drop shape analysis-profile in combination with variable angle spectroscopic ellipsometry (VASE). It was found that both advancing and receding contact angles became smaller with increasing the number of cycles and are, therefore, not a property of the dry solid alone. The changes of the wetting behavior during these dynamic cycling contact angle measurements are attributed mainly to swelling and/or liquid retention. To reveal the water-induced changes of the polymer film, the polyimide surface was studied before and after the contact with a water droplet by VASE. Both the experimental ellipsometric spectrum for Delta and that for Psi as well as the corresponding simulations show characteristic shifts due to the contact with water. The so-called effective medium approximation was applied to recover information about the thickness and effective optical constants of the polymer layer from the ellipsometrically measured values of Delta and Psi. On the basis of these results, the swelling and retention behavior of the polyimide films in contact with water droplets were discussed.     

Resolving the different silicon clusters in Li12Si7 by 29Si and (6,7)Li solid-state NMR spectroscopy

Structural signatures: The analysis of Si-Si and Si-Li connectivities by solid-state NMR spectroscopy allows the different types of silicon clusters to be discriminated in the model lithium silicide compound Li(12)Si(7) (see picture, Si clusters red and blue, Li ions gray). The results provide new NMR spectroscopic strategies with which to differentiate and study the structures formed in silicon-based electrode materials.     

Raman spectroscopy of ZnS nanostructures

We report Raman scattering results of wurtzite ZnS nanowires, nanocombs, and nanobelts. The Raman spectrum obtained from ZnS nanowires exhibits first‐order phonon modes at 272, 284, and 350 cm⁻¹, corresponding to A₁/E₁ transverse optical, E₂ transverse optical, and A₁/E₁ longitudinal optical phonons, respectively. Several multiphonon modes are also observed. The longitudinal optical phonon mode varies in wavenumber for nanocombs and nanobelts, indicating that the residual strain varies during the morphological change from ZnS nanowires to nanocombs and ultimately to nanobelts. Interestingly, a surface optical (SO) phonon mode varies in wavenumber depending on the shape and surface roughness of the ZnS nanostructures. The surface modulation wavelengths of the ZnS nanowires, nanocombs, and nanobelts are estimated using the SO phonon dispersion relations and the observed SO phonon wavenumbers. Copyright © 2012 John Wiley & Sons, Ltd.