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51.
Radiation-induced polymerization of monomers, for example N-methacryl-oxysuccinimide (MASu) and diethylene glycol dimethacrylate (2G), in ethyl propionate, was performed from +25°C to –78°C. The copoly (MASu/2G) microspheres were obtained in MASu monomer compositions of 30 wt % or below. The average particle diameter of copoly(MASu/2G, 20/80 wt %) microspheres obtained at irradiation temperatures of 25°, 0°, and –43 °C were 0.81±0.29, 0.63±0.26, and 0.90±0.43 m, respectively. No microspheres were formed when irradiated at –78 °C. The reactivity of the succinimide groups on the surface of copoly(MASu/2G, 20/80 wt%) microspheres was checked by reacting with ethylene diamine. The maximal amount of reacting succinimide groups was 9.4±0.5 nol/g, which corresponds to about 1 % of the total number of succinimide groups in the microsphere. 相似文献
52.
The molecular structure of COBr2 has been determined as follows by an analysis of electron diffraction intensity: rg(CO) = 1.178 ± 0.009 Å, rg(C-Br) = 1.923 ± 0.005 Å and θ°α(Br-C-Br) = 112.3 ± 0.4°. The uncertainties represent estimated limits of error. The observed systematic trends in the bond lengths and bond angles in carbonyl and thiocarbonyl halides are discussed. 相似文献
53.
T Abe K Horiuchi H Kikuchi T Aritsuka Y Takata E Fukushi Y Fukushi J Kawabata K Ueno S Onodera N Shiomi 《Chemistry Central journal》2012,6(1):89
ABSTRACT: BACKGROUND: Sugar beet molasses is a viscous by-product of the processing of sugar beets into sugar. The molasses is known to contain sucrose and raffinose, a typical trisaccharide, with a well-established structure. Although sugar beet molasses contains various other oligosaccharides as well, the structures of those oligosaccharides have not been examined in detail. The purpose of this study was isolation and structural confirmation of these other oligosaccharides found in sugar beet molasses. RESULTS: Four oligosaccharides were newly isolated from sugar beet molasses using high-performance liquid chromatography (HPLC) and carbon-Celite column chromatography. Structural confirmation of the saccharides was provided by methylation analysis, matrix-assisted laser desorption/ionaization time of flight mass spectrometry (MALDI-TOF-MS), and nuclear magnetic resonance (NMR) measurements. CONCLUSION: The following oligosaccharides were identified in sugar beet molasses: beta-D-galactopyranosyl-(1- > 6)-beta-D-fructofuranosyl-(2 <-> 1)-alpha-D-glucopyranoside (named beta-planteose), alpha-D-galactopyranosyl-(1- > 1)-beta-D-fructofuranosyl-(2 <-> 1)-alpha-D-glucopyranoside (named1-planteose), alpha-D-glucopyranosyl-(1- > 6)-alpha-D-glucopyranosyl-(1 <-> 2)-beta-D-fructofuranoside (theanderose), and beta-D-glucopyranosyl-(1- > 3)-alpha-D-glucopyranosyl-(1 <-> 2)-beta-D-fructofuranoside (laminaribiofructose). 1-planteose and laminaribiofructose were isolated from natural sources for the first time. 相似文献
54.
Abstract Ribozymes that distinguish a single base change in RNA were synthesized and used to specifically cleave c-Ha-ras messenger RNA. Using phosphorothioate containing oligonucleotide substrates, we have shown that Mg2+ binds to the pro-R oxygen of the phosphate and that the RNA cleavage reaction occurs via an in-line mechanism. Oligoribonucleotides containing a modified nucleoside are described. 相似文献
55.
56.
Yuka Yamazaki Akihiro Yokoyama Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2012,50(17):3648-3655
Well‐defined (AB)3 type star block copolymer consisting of aromatic polyether arms as the A segment and polystyrene (PSt) arms as the B segment was prepared using atom transfer radical polymerization (ATRP), chain‐growth condensation polymerization (CGCP), and click reaction. ATRP of styrene was carried out in the presence of 2,4,6‐tris(bromomethyl)mesitylene as a trifunctional initiator, and then the terminal bromines of the polymer were transformed to azide groups with NaN3. The azide groups were converted to 4‐fluorobenzophenone moieties as CGCP initiator units by click reaction. However, when CGCP was attempted, a small amount of unreacted initiator units remained. Therefore, the azide‐terminated PSt was then used for click reaction with alkyne‐terminated aromatic polyether, obtained by CGCP with an initiator bearing an acetylene unit. Excess alkyne‐terminated aromatic polyether was removed from the crude product by means of preparative high performance liquid chromatography (HPLC) to yield the (AB)3 type star block copolymer (Mn = 9910, Mw/Mn = 1.10). This star block copolymer, which contains aromatic polyether segments with low solubility in the shell unit, exhibited lower solubility than A2B or AB2 type miktoarm star copolymers. In addition, the obtained star block copolymer self‐assembled to form spherical aggregates in solution and plate‐like structures in film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
57.
Motoko S. Asano Sho Hashimoto Takuya Shinozuka Yasutaka Fushimi 《Molecular physics》2019,117(19):2664-2672
ABSTRACTInteraction between a zinc porphyrin (ZnPor) as the end-group and poly(9,9-di-n-octylfluorene-2,7-vinylene) (PFV) as the main chain in a porphyrin end-modified fluorescent conjugated polymer, ZnPFV, was studied by time-resolved electron paramagnetic resonance (EPR) and fluorescence spectroscopy. While fluorescence from the PFV part of ZnPFV showed a spectral profile almost identical to that of a PFV oligomer without end-modification, the emission spectrum of the ZnPor part exhibited a much broader profile compared to that of the reference zinc porphyrin monomer. Based on the analysis of lifetimes and quantum yields, it was found that radiative rate constant of the ZnPor part was enhanced by nearly three times. The observed unusual enhancement in the radiative rate constant was rationalised in terms of a partial π-conjugation between the end group and the main chain, as a result of co-planarisation in fluid solution. On the other hand, the time-resolved EPR spectrum of ZnPFV at 100?K basically showed a similar spectral pattern to that of the reference zinc porphyrin, but with significant differences in zero-field spitting parameters and initial population ratios. The π-system of the excited triplet state is deduced to deviate from D4h symmetry in the end zinc porphyrin groups. The obtained results show that interaction of the porphyrin end group with the main chain of the polymer significantly influences the excited singlet state properties of the porphyrin, while its triplet state properties were affected to a lesser extent. 相似文献
58.
Yasuhiro Igarashi Daisuke Asano Kazuo Furihata Naoya Oku Satoshi Miyanaga Hiroaki Sakurai Ikuo Saiki 《Tetrahedron letters》2012,53(6):654-656
During the course of screening natural products for the inhibitors of tumor cell invasion, pterocidin, a linear polyketide with a δ-lactone terminus, was rediscovered from a Streptomyces strain of a marine sediment-origin. A series of J-based configuration analyses and NOESY analysis, coupled with chemical derivatization and chiral anisotropy analysis, established the absolute stereochemistry of five asymmetric centers in this compound. 相似文献
59.
Novel aryl-β-C-glucosidation method using glucal boronate was developed. This protocol can offer several advantages including use of non-toxic, easily handling glucal boronate as a crystalline solid and storable at room temperature for several months. Tri-O-methylnorbergenin (8,10-di-O-methylbergenin), an anti-HIV active bergenin derivative, was concisely synthesized by application of the aryl-β-C-glucosidation method. 相似文献
60.
Kazuyuki Kubo Hiroshi Nakazawa Hiroyasu Inagaki Tomoyuki Miyake Tsutomu Mizuta Katsuhiko Miyoshi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8-9):2159-2160
Treatment of [Cp*(CO) 2 M{P(NHPh)(OMe) 2 }]PF 6 (M = Fe and Ru) with NaNH 2 gives metallaiminophosphoranes, Cp*(CO) 2 M{P(NPh)(OMe) 2 }. The x-ray structures and reactivity of the complexes are reported. 相似文献