Constituents of Holothuroidea, 17. Isolation and structure of biologically active monosialo-gangliosides from the sea cucumber Cucumaria echinata

Three new monosialo-gangliosides, CEG-3 (3), CEG-4 (4), and CEG-5 (5), were obtained, together with two known gangliosides, SJG-1 (1) and CG-1 (2), from the lipid fraction of the chloroform/methanol extract of the sea cucumber Cucumaria echinata. The structures of the new gangliosides were determined on the basis of chemical and spectroscopic evidence to be 1-O-[4-O-acetyl-alpha-L-fucopyranosyl-(1-->11)-(N-glycolyl-alpha-D-neuraminosyl)-(2-->6)-beta-D-glucopyranosyl]-ceramide (3) and 1-O-[alpha-L-fucopyranosyl-(1-->11)-(N-glycolyl-alpha-D-neuraminosyl)-(2-->6)-beta-D-glucopyranosyl]-ceramide (4, 5). The ceramide moieties of each compound were composed of heterogeneous sphingosine or phytosphingosine bases, and 2-hydroxy or nonhydroxylated fatty acid units. These gangliosides showed neuritogenic activity toward the rat pheochromocytoma cell line PC-12 in the presence of nerve growth factor.     

Synthesis of proton‐conducting block copolymer membranes composed of a fluorinated segment and a sulfonic acid segment

Diblock copolymer membranes having a fluorinated segment and a sulfonic acid segment were prepared by living radical polymerization, solution casting, and crosslinking, followed by heat treatment. Diblock copolymers of 2,3,4,5,6‐pentafluorostyrene (PFS)/4‐(1‐methylsilacyclobutyl)styrene (SBS) and neopentyl styrenesulfonate (SSPen) (poly(PFS‐co‐SBS)‐b‐polySSPen)s were synthesized by nitoroxy‐mediated living radical polymerization. Self‐standing crosslinked membranes were obtained by casting a THF solution of the block copolymer with Pt catalyst. Heat treatment of the membrane at 230 °C induced decomposition of the neopentyl sulfonate esters to provide block copolymer membranes having a fluorinated segment and a free sulfonic acid segment. It was confirmed that the block copolymer with a high sulfonic acid content exhibited high ion exchange capacity and high proton conductivity as well as high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4479–4485, 2008     

Efficient generation of vibrational stimulated Raman emission in the ultraviolet region using a femtosecond pump beam

The third harmonic emission (261 nm, 30 μJ) of a femtosecond Ti:sapphire laser is focused into molecular hydrogen to generate vibrational stimulated Raman emission. High-order emission lines are efficiently generated by using a high-beam-quality nearly-transform-limited laser and high-pressure hydrogen (40 atm) as a Raman medium.     

Phosphorothioate Modification of mRNA Accelerates the Rate of Translation Initiation to Provide More Efficient Protein Synthesis

Messenger RNAs (mRNAs) with phosphorothioate modification (PS‐mRNA) to the phosphate site of A, G, C, and U with all 16 possible combinations were prepared, and the translation reaction was evaluated using an E. coli cell‐free translation system. Protein synthesis from PS‐mRNA increased in 12 of 15 patterns when compared with that of unmodified mRNA. The protein yield increased 22‐fold when the phosphorothioate modification at A/C sites was introduced into the region from the 5′‐end to the initiation codon. Single‐turnover analysis of PS‐mRNA translation showed that phosphorothioate modification increases the number of translating ribosomes, thus suggesting that the rate of translation initiation (rate of ribosome complex formation) is positively affected by the modification. The method provides a new strategy for improving translation by using non‐natural mRNA.     

The first stereospecific arylation of (Z)‐germyl(stannyl)ethenes with an aryl halide or heteroaryl halide under palladium‐catalysis

A combination catalyst of Pd(dba)₂‐PPh₃‐CuI‐LiCl or Pd(dba)₂‐P(2‐furyl)₃‐CuI‐LiCl effectively catalyzed the cross‐coupling of (Z)‐germyl(stannyl)ethenes with aryl halides, providing novel triethyl(2,2‐diarylethenyl)germanes in good to high yields. The reaction proceeds with retention of configuration. Cross‐coupling results in the formation of phenylene or phenyleneethynylene derivatives with terminal stereochemically defined vinylgermane unit(s). Copyright © 2008 John Wiley & Sons, Ltd.     

Busy-period and blocking behavior of finite queues with state-dependent Markov renewal arrivals

The busy-period length distributions and blocking probabilities are considered for finiteG/G/1/K queues with state-dependent Markov renewal arrivals. The Laplace-Stieltjes transforms of the distributions and blocking probabilities are given for the non-preemptive and last-come-first-served preemptive resume (or repeat) service disciplines. For Erlangian (or deterministic) service times in particular, it is proved that the busy-period length (the number of blocked customers) for the non-preemptive discipline is smaller (larger) than for the preemptive resume discipline.     

Fundamental burning velocities of meso-scale propagating spherical flames with H2, CH4 and C3H8 mixtures

This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale outwardly propagating spherical laminar flames in the range of flame radius r_f approximately from 1 to 5 mm for hydrogen, methane and propane mixtures, in order to make clear a method for improving combustion of micro–meso scale flames. Macro-scale laminar flames with r_f > 7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity (S_L0 = 25 cm/s) for unstretched flames and different equivalence ratios ?. The radius r_f and the burning velocity S_Ll of meso-scale flames are estimated by using sequential schlieren images recorded under appropriate ignition conditions. It is found that S_Ll of hydrogen and methane premixed meso-scale flames at the same r_f or the Karlovitz number Ka shows a tendency to increase with decreasing ?, whereas S_Ll of propane flames increases with ?. However, S_Ll tends to decrease with the Lewis number Le and the Markstein number Ma, irrespective of the type of fuel and ?. It also becomes clear that the optimum flame size and Ka to improve the burning velocity exist for some mixtures depending on Le and fuel types.     

Analysis and design of concave lens with metallic slit array for terahertz wave band

This paper presents a three-dimensional concave lens constructed from a metallic slit array. The effective refractive index is estimated to be $0<n<1$ . The actual lens requires spacers in the slits. A lens using a low loss dielectric material for the terahertz frequency band is designed. The fast wave effect is enhanced in order to mitigate the slow wave effect of the dielectric material. Full wave analysis results are obtained by ANSYS HFSS and the focusing effect of the three-dimensional concave lens is confirmed in the terahertz frequency band.     

Optimization of spectral-domain optical coherence tomography with a supercontinuum source for in vivo motion detection of low reflective outer hair cells in guinea pig cochleae

Optical Review - Sound evokes sub-nanoscale vibration within the sensory epithelium. The epithelium contains not only immotile cells but also contractile outer hair cells (OHCs) that actively...     

Syntheses, crystal structures, and water adsorption behaviors of jungle-gym-type porous coordination polymers containing nitro moieties

NO₂ containing dicarboxylate bridging ligands, nitroterephthalate (bdc-NO₂) and 2,5-dinitroterephthalate (bdc-(NO₂)₂), afford porous coordination polymers, {[Zn₂(bdc-NO₂)₂(dabco)]·solvents}_n (2⊃solvents) and {[Zn₂(bdc-(NO₂)₂)₂(dabco)]·solvents}_n (3⊃solvents). Both compounds form jungle-gym-type regularities, where a 2D square grid composed of dinuclear Zn₂ units and dicarboxylate ligands is bridged by dabco molecules to extend the 2D layers into a 3D structure. In 2⊃solvents and 3⊃solvents, a rectangle pore surrounded by eight Zn₂ corners contains two and four NO₂ moieties, respectively. Thermal gravimetry (TG) and X-ray powder diffraction (XRPD) measurements reveal that both compounds maintain the frameworks regularities without guest molecules and with solvents such as MeOH, EtOH, i-PrOH, and Me₂CO. Adsorption measurements reveal that dried 2 and 3 adsorb H₂O molecules to be {[Zn₂(bdc-NO₂)₂(dabco)]·4H₂O}_n (2⊃4H₂O) and {[Zn₂(bdc-(NO₂)₂)₂(dabco)]·6H₂O}_n (3⊃6H₂O), showing the pore hydrophilicity enhancement caused by NO₂ group introduction.