Effect of ginseng saponins on the survival of cerebral cortex neurons in cell cultures

The effects of nerve growth factor (NGF) and saponins isolated from Panax ginseng C.A. Mayer on the survival of chick and rat embryonic cerebral cortex neurons were examined. Ginsenoside Rg1 (GRg1) exerted a survival-promoting effect on both chick and rat cerebral cortex neurons in cell cultures. Ginsenoside Rb1 (GRb1) also had an effect in the rat and displayed some influence in the chick. NGF alone exerted no effect on both neurons, although it did potentiate the GRb1 effect on chick embryonic cerebral cortex neurons, but did not alter the GRb1 effect on rat embryonic cerebral cortex neurons. NGF did not alter the survival-promoting effect of GRg1 on either chick or rat embryonic cerebral cortex neurons. The other saponins alone or with NGF exerted no effect on the survival of cerebral cortex neurons in either the chick or rat.     

Alkane Oxidation with Molecular Oxygen Using a New Efficient Catalytic System: N-Hydroxyphthalimide (NHPI) Combined with Co(acac)(n)() (n = 2 or 3)

A novel class of catalysts for alkane oxidation with molecular oxygen was examined. N-Hydroxyphthalimide (NHPI) combined with Co(acac)(n)() (n = 2 or 3) was found to be an efficient catalytic system for the aerobic oxidation of cycloalkanes and alkylbenzenes under mild conditions. Cycloalkanes were successfully oxidized with molecular oxygen in the presence of a catalytic amount of NHPI and Co(acac)(2) in acetic acid at 100 degrees C to give the corresponding cycloalkanones and dicarboxylic acids. Alkylbenzenes were also oxidized with dioxygen using this catalytic system. For example, toluene was converted into benzoic acid in excellent yield under these conditions. Ethyl- and butylbenzenes were selectively oxidized at their alpha-positions to form the corresponding ketones, acetophenone, and 1-phenyl-1-butanone, respectively, in good yields. A key intermediate in this oxidation is believed to be the phthalimide N-oxyl radical generated from NHPI and molecular oxygen using a Co(II) species. The isotope effect (k(H)/k(D)) in the oxidation of ethylbenzene and ethylbenzene-d(10) with dioxygen using NHPI/Co(acac)(2) was 3.8.     

Synthesis of poly(2-cyclohexenone-4-yl methacrylate) and acidolysis of pendant protecting groups in the polymer

4-Acetoxy-2-cyclohexenone (ACH) and 2-cyclohexenone-4-yl methacrylate (CHM) were obtained from the condensation reaction of 4-bromo-2-cyclohexenone (BCH) with acetic acid and methacrylic acid using 1,8-diazabicyclo-[5,4,0]-7-undecene (DBU), respectively. Poly(2-cyclohexenone-4-yl methacrylate) ( P-1 ) containing acid-sensitive 2-cyclohexenone-4-yl group was prepared from the radical polymerization of CHM and the esterification of poly(methacrylic acid) with BCH using DBU. Furthermore, P-1 and CHM copolymers ( P-2 and P-3 ) were easily synthesized from the radical polymerization of methacrylic acid and comonomers in dimethylsulfoxide using 1 mol % of 2,2′-azobis (isobutyronitrile) followed by esterification of the resulting polymers with BCH using DBU by one-pot method. The deprotection reaction of ACH and P-1 was carried out in dichloromethane using an acid catalyst. The reaction proceeded smoothly in solution to give phenol and the corresponding carboxylic acid. Therefore, the 2-cyclohexenone-4-yl group is a useful protecting group for carboxylic acids, because the protection and deprotection reactions are very easy. In the case of polymer films, however, the acid was trapped by carbonyl group on the 2-cyclohexenone-4-yl group, and did not cause the deprotection reaction. © 1993 John Wiley & Sons, Inc.     

New approaches inμ + SR studies on critical phenomena in Ni

The critical phenomena in Ni are probed by pulsedSR method under longitudinal- and zero external magnetic fields. The sample magnetization around the critical temperature is confirmed simultaneously by bulk magnetization measurement in situ, disappearance of transverseSR signal and recovery of asymmetry under longitudinal field. At the same time, the ratio of the ⁺ hyperfine field to the bulk magnetization in the ferromagnetic phase below the critical temperature is determined from the observables obtained only in the present experiment. The zero- and low-field longitudinal relaxation rate of muon does not diverge in approaching toT _c in the paramagnetic region, but seems to reach a saturation value.This work is supported by the Grand-in-Aid of the Japanese Ministry of Education, Culture and Science.     

Site-selective RNA cleavage by DNA bearing a base pair-mimic nucleoside

We have synthesized the deoxyadenosine derivative tethering a phenyl group (X), which mimics the Watson-Crick A/T base pair. The RNA/DNA hybrid duplexes containing X in the middle of the DNA sequence showed a similar thermal stability regardless of the ribonucleotide species (A, G, C, or U) opposite to X, probably because of the phenyl group stacking inside of the duplex accompanied by the opposite ribonucleotide base flipped in an extrahelical position. The RNA strand hybridized with the DNA strand bearing X was cleaved on the 3'-side of the ribonucleotide opposite to X in the presence of MgCl2, and the RNA sequence to be cleaved was not restricted. The site-specific RNA hydrolysis suggests that the DNA strand bearing X has the advantage of the site-selective base flipping in the target sequence and the development of a "universal deoxyribozyme" to exclusively cleave a target RNA sequence.     

An efficient synthesis of N-tert-butoxycarbonyl-O-cyclohexyl-L-tyrosine

A facile and efficient synthesis of N-tert-butoxycarbonyl-O-cyclohexyl-L-tyrosine [Boc-Tyr(Chx)-OH] is described. Boc-Tyr-OH was treated with NaH in dimethylformamide and then with 3-bromocyclohexene to give N-Boc-O-(cyclohex-2-enyl)-L-tyrosine [Boc-Tyr(Che)-OH] in 70% yield. Hydrogenation of Boc-Tyr(Che)-OH over PtO2 afforded Boc-Tyr(Chx)-OH in almost quantitative yield. The highest yield was achieved when a side product in the synthesis of Boc-Tyr-OH, Boc-Tyr(Boc)-OH, was not removed, because it was also converted to Boc-Tyr(Che)-OH without any additional manipulations. The new synthetic method described here is convenient for practical use, and would facilitate the widespread use of the Chx group for the hydroxy-protection of Tyr.     

Light emission from chlorine atoms formed in the dissociative excitation of HCI in a flowing afterglow of discharged argon

Light emission from Cl(5p) atoms (near 440 nm) produced in the reaction of HCl in a discharged flow of argon was investigated with a flowing-afterglow apparatus. Ionic species, most probably argon ions in metastable states, Ar^+M, were found to be responsible for the Cl(5p) production in the dissociative excitation of HCl.     

PEGylated polyplex micelles from triblock catiomers with spatially ordered layering of condensed pDNA and buffering units for enhanced intracellular gene delivery

An A-B-C type triblock copolymer, tandemly aligning two types of polycations with different pKa values in a single polymer strand, was developed for the construction of novel polyplex micelles, satisfying a high DNA condensing ability as well as a proton buffering activity directed to elevating gene transfection. The micelle might feature the distinctive three-layered structure, where an inner polyplex layer of condensed pDNA with poly(l-lysine) (pKa approximately 9.4) as the C segment is successively wrapped with an intermediate layer of poly[(3-morpholinopropyl)aspartamide] (B segment) with a comparatively low pKa of approximately 6.2, to provide a buffering effect, and an outer PEG layer (A segment) as a biocompatible palisade.     

Mass spectral fragmentations of 6-aryl-5,6,7,8-tetrahydro-4H-1,3,2,6-dioxathiazocine 2-Oxides

The mass spectral fragmentation of 4-, 5-, and 4,8-disubstituted derivatives of 6-aryl-5,6,7,8-tetrahydro-4H-1,3,2,6-dioxathiazocine 2-oxides is reported.