Deuterium N.M.R. studies of polypeptides I. Sidechain orientation in poly(γ-benzyl L-glutamate) and the mechanism of the cholesteric sense inversion

The mechanism of thermally- and solvent-induced cholesteric sense inversions in lyotropic polypeptide liquid crystals has been discussed based on deuterium N.M.R. observations for poly(γ-benzyl L-glutamate) with perdeuteriated sidechain benzyl ester groups. Comparison of the deuterium quadrupolar splitting pattern with the macroscopic helical twisting power indicates that the sense inversion does not necessarily require sidechain conformational transitions (or changes in the helix surface chirality). The new data support a less specific mechanism for sense determination in polypeptide liquid crystals: anisotropic intermolecular interactions between helices are influenced by the solvent dielectric medium.     

Asymmetric synthesis of metallocenes through enantioselective addition of organolithium reagents to 6-(dimethylamino)fulvene

Enantioselective addition of aryllithiums 2a-d (Ar = Ph (a), 2-MeC(6)H(4) (b), 2-MeOC(6)H(4) (c), 1-naphthyl (d)) to 6-(dimethylamino)fulvene (1) in the presence of (-)-sparteine in toluene at -78 degrees C generated chiral cyclopentadienyllithiums (4) substituted with an N,N-dimethylamino(aryl)methyl group, where the enantioselectivities are 51, 91, 90, and 83% for 4a, 4b, 4c, and 4d, respectively. Treatment of the chiral cyclopentadienides 4 with FeCl(2) or Fe(acac)(2) gave ferrocenes, which contain an N,N-dimethylamino(aryl)methyl side chain on both of the cyclopentadienyl rings. The enantiomeric purity of the chiral ferrocenes 7 thus obtained is 99% ee or higher for those containing a 2-MeC(6)H(4) (7b) or a 2-MeOC(6)H(4) (7c) group.     

Oxidative degradation of 8-nitroquinoline with hydrogen peroxide in acetic acid a possible mechanism through 3,4-epoxide of quinoline ring

The treatment of 8-nitroquinoline with hydrogen peroxide and acetic acid at 60°C afforded 7-nitroindole, 7-nitro-2-oxindole, 2-amino-3-nitrobenzoic acid, 2-amino-3-nitrobenzaldehyde, 3,4-dihydro-3, 4-trans-dihydroxy-8-nitrocarbostyril, 3,4-trans-dihydro-3-hydroxy-4-acetoxy-8-nitrocarbostyril, and 1-(2-amino-3-nitrophenyl)-2-hydroxy-ethanone. The reaction mechanism acceptable in elucidating the formation of these products involves, at the initial step of reaction, an epoxidation of the 3,4-double bond of the 1,2-dihydro adduce of quinoline ring.     

Thermoluminescence from extended-chain crystals of polyethylene

Thermoluminescence (TL) has been observed in γ-irradiated extended-chain crystals of polyethylene above room temperature. The TL curve, which exhibits four peaks at 50, 90, 120, and 140°C, is different from that given by folded-chain crystals, in both shape and intensity. In particular, a shape, strong glow peak is observed at 140°C, corresponding to the melting temperature of the extended chain crystals. These results are discussed in relation to independent measurements by differential scanning calorimetry and electron spin resonance.     

Invariance of Picard Dimensions Under Basic Perturbations

The Picard dimension \(\dim \mu\) of a signed Radon measure μ on the punctured closed unit ball 0?x|?≦?1 in the d-dimensional euclidean space with d?≧?2 is the cardinal number of the set of extremal rays of the cone of positive continuous distributional solutions u of the Schrödinger equation (???Δ?+?μ)u?=?0 on the punctured open unit ball 0?x|?x|?=?1. If the Green function of the above equation on 0?x|?Δ?+?μ)u?=?δ _y , the Dirac measure supported by the point y, exists for every y in 0?x|?μ is referred to as being hyperbolic on 0?x|?γ is a radial Radon measure which is both positive and absolutely continuous with respect to the d-dimensional Lebesgue measure dx whose Radon–Nikodym density dγ(x)/dx is bounded by a positive constant multiple of |x|^???2. The purpose of this paper is to show that the Picard dimensions of hyperbolic radial Radon measures μ are invariant under basic perturbations \(\gamma: \dim(\mu+\gamma)=\dim\mu\). Three applications of this invariance are also given.     

Fully automated two-dimensional high-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry for the determination of oligosaccharides in glycopeptides after enzymic fluorescence labeling

Two-dimensional high-performance liquid chromatography using an electrospray ionization time-of-flight mass spectrometry (2D-HPLC-ESI-TOF-MS) system was established for the on-line determination of asparagine-linked oligosaccharides in glycopeptides. The analysis of the oligosaccharides started with the enzymic transglycosylation reaction utilizing Endo-beta-N-acetylglucosaminidase (Endo-M). The oligosaccharides were transferred to a fluorescent acceptor (NDA-Asn-GlcNAc) with Endo-M to produce the fluorescent oligosaccharides. The resulting fluorescent oligosaccharides were specifically isolated from the non-fluorescent oligosaccharides with fluorescence detection after separation by the 1st dimension Amide-80 column. The fraction of fluorescent oligosaccharides was effectively trapped in the anion exchange column. The trapped oligosaccharides were then separated by the 2nd dimension ODS column and sensitively determined by ESI-TOF-MS. Disialo-Asn (a model oligosaccharide) and several oligosaccharides liberated from ovalbumin could be efficiently separated by the 2D-HPLC and identified from the ESI-TOF-MS. Based on these results, the proposed 2D-HPLC-ESI-TOF-MS system may be useful for on-line oligosaccharide analyses. Although the analytical run time is still long, a high-throughput determination will be performed by optimization of the 2D-HPLC conditions.     

Synthesis and structure activity relationship studies of benzothieno[3,2-b]furan derivatives as a novel class of IKKbeta inhibitors

As a novel class of IKKbeta inhibitors, a series of tricyclic furan derivatives was designed and synthesized based on the structure of known thiophene IKKbeta inhibitors. Among the various fused furan derivatives synthesized, a benzothieno[3,2-b]furan derivative 13a displayed potent inhibitory activity towards IKKbeta in enzymatic and cellular assays. The potent inhibitory activity originates from an intramolecular non-bonded S...O interaction which was confirmed by the X-ray structure of JNK3 with 16k. The introduction of further substituents on the core structure led to the discovery of the 6-alkoxy derivatives, which possessed a comparable IKKbeta inhibitory activity to 13a and an improved metabolic stability. Among these, appropriately lipophilic compounds 16a, h, i, and 13g (log D>2) were found to possess good oral bioavailability.     

Development of a column-switching high-performance liquid chromatography for kynurenine enantiomers and its application to a pharmacokinetic study in rat plasma

Kynurenine (KYN), a tryptophan metabolite, is a precursor of kynurenic acid, which is an antagonist of N-methyl-d-aspartate receptor. In this study, an enantiomeric separation of d,l-KYN derivatized with the benzofurazan fluorescence reagent 4-N,N-dimethylaminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (DBD-F) (DBD-d,l-KYN) was first investigated by using a high-performance liquid chromatography (HPLC) with several chiral columns. As a consequence, DBD-d,l-KYN was enantiomerically separated on a cellulose-type chiral column (CHIRALCEL OJ-RH) with a mobile phase of H₂O/CH₃CN/MeOH (40/50/10) containing 0.1% acetic acid. Under this condition, the separation factor and resolution were 1.48 and 1.28, respectively. Next, a column-switching HPLC consisting of both octadecylsilica and chiral columns was developed and used to determine both d- and l-KYN enantiomers in 10 μL of rat plasma following the intraperitoneal administration of d,l-KYN to rats (10 mg kg⁻¹). The result revealed that the concentration of l-KYN was higher than that of d-KYN, suggesting that d-KYN was eliminated faster than l-KYN.     

Resolution of oligosaccharides in glycopeptides using immobilized Endo-M and ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry

The resolution of asparagine-linked oligosaccharides in glycopeptides was carried out by combination of the transglycosylation reaction and ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry (UPLC-ESI-TOF-MS). The resolution of the oligosaccharides is based on the enzymic transglycosylation reaction with Endo-beta-N-acetylglucosaminidase (Endo-M) isolated from Mucor hiemalis. The oligosaccharides were transferred to a fluorescent acceptor (NDA-Asn-GlcNAc) with Endo-M to produce the fluorescent oligosaccharides. In the present research, the enzyme was also immobilized in the well of a microassay plate by the sol-gel technique. The transglycosylation reaction was easily managed due to the immobilization. Furthermore, multiple use was possible by the encapsulated Endo-M. The resulting fluorescent oligosaccharides were separated by UPLC and efficiently detected by ESI-TOF-MS. Several oligosaccharides in ovalbumin were successfully identified by the proposed procedure.