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291.
Harumi Kaga Atsushi Narumi Toshifumi Satoh Takeshi Matsuda Mohd. Sharfuddin Toyoji Kakuchi 《Macromolecular Symposia》2002,181(1):95-100
Coupling reactions of TEMPO-terminated polystyrene (PS-TEMPO) with divinylbenzene were performed in the presence of vinyl saccharides 1 , successfully producing star-shaped polystyrenes with glycoconjugated core 2 . Amphiphilic star-shaped polystyrenes with cores containing saccharide as hydrophilic segments 3 were obtained by the deacetylation of 2 , which exhibited an encapsulation ability toward methyl orange (MO) in chloroform. A positive Cotton effect was observed in the CD spectrum for the MO/ 3 in the adsorption area of MO, indicating that MO existed in a chiral segment, i.e., the glycoconjugated core. 相似文献
292.
Tadahiro Kato Toshifumi Hirukawa Takaaki Suzuki Masaharu Tanaka Masahiro Hoshikawa Makoto Yagi Motoyuki Tanaka Shin‐suke Takagi Naoko Saito 《Helvetica chimica acta》2001,84(1):47-68
Based on the putative biogenesis of trinervitane‐ and kempane‐type diterpenes (Scheme 1), a biogenetic‐type transformation was simulated by cyclization of 7,16‐secotrinervita‐7,11,15‐triene‐2α,3α,17‐triol ( 23 ) and of its 17‐chloro derivative 30 . The requisite substrates were prepared from geranylgeranoic acid chloride 6 (Schemes 2, 4, and 5). Treatment of 30 with AgClO4 at −20° provided the trinervitantrienediols 32 and 33 in 68 and 5% yields, while kempadienediol 35 was obtained in 50% yield by the same reagent at +20° (Scheme 7). The structures of the cyclization products were elaborated from detailed inspection of NMR spectra including H,H COSY, C,H COSY, and NOESY (Tables 1 and 2). The conformation of 30 and its plausible cyclization intermediate was discussed with the help of physical evidence, including X‐ray crystallographic analysis. 相似文献
293.
294.
Fang S Takao T Satomi Y Mo W Shimonishi Y 《Journal of the American Society for Mass Spectrometry》2000,11(4):345-351
C-terminal rearrangement ions [b(n-1) + H2O] (where n refers to the total number of residues of peptides) are frequently observed for peptides which contain basic amino acid(s), especially arginine, at or near their N termini in low- and high-energy collision-induced dissociation or post-source decay (PSD) spectra. Here we report a novel rearrangement, associated with PSD for serine- or threonine-containing peptides that are susceptible to C-terminal rearrangement. Based on PSD analyses of serine- or threonine-containing bradykinin and its analogs, which have been ethyl-esterified or 18O labeled at their C termini, the [b(k) + H2O] (where k denotes the position adjacent to the left of the Ser/Thr residue) ion is generally thought to be formed by the transfer of the hydroxyl moiety of a serine or threonine residue to the carbonyl group of the residue to its left accompanied by the loss of the remaining C-terminal portion of the peptide. When the Ser/Thr is at or near the C terminus, the present [b(k) + H2O] ion could be formed via two pathways, i.e., the Ser/Thr-related rearrangement and the conventional C-terminal rearrangement, which has been clearly verified by 18O labeling at the C terminus. In addition, the ions which are formally designated as [y(m)b(l) + H2O], where y(m)b(l) denotes a b-type internal ion, are also briefly described. 相似文献
295.
Fernández-de-Cossio J Gonzalez LJ Satomi Y Betancourt L Ramos Y Huerta V Besada V Padron G Minamino N Takao T 《Rapid communications in mass spectrometry : RCM》2004,18(20):2465-2472
Mass spectrometry is now firmly established as a powerful technique for the identification and characterization of proteins when used in conjunction with sequence databases. Various approaches involving stable-isotope labeling have been developed for quantitative comparisons between paired samples in proteomic expression analysis by mass spectrometry. However, interpretation of such mass spectra is far from being fully automated, mainly due to the difficulty of analyzing complex patterns resulting from the overlap of multiple peaks arising from the assortment of natural isotopes. In order to facilitate the interpretation of a complex mass spectrum of such a mixture, such as an MS spectrum of a stable-isotope-enriched ion species, we report on the development of a software application, 'Matching' (web accessible), that enables the automatic matching of theoretical isotope envelopes to multiple ion peaks in a raw spectrum. It is particularly useful for resolving the relative abundances of narrow-split paired peaks caused by enrichment with a stable isotope, such as 18O, 13C, 2H, or 15N. 相似文献
296.
Murashima T Tsukiyama S Fujii S Hayata K Sakai H Miyazawa T Yamada T 《Organic & biomolecular chemistry》2005,3(22):4060-4064
The novel ferrocene-based ditopic receptor 1 was synthesized. This receptor bears two oligoethylene glycol arms with pendant 2,2'-bipyridine unit at the identical cyclopentadienyl rings, Cu(I) cation binds to 1 to form the 1 : 1 complex (1.Cu(I)) with the cavity consisting of polyether, and the resulting complex acts as a receptor for amino acid ester salts to give the ditopic complex (1.Cu(I).AAOMe-HCl). The 1H NMR spectrum of 1.Cu(I).LeuOMe-HCl exhibits strong broadening at the bipyridine region, and the ESR spectrum of the same sample gives the signals assigned as Cu(II) species. With these data, the binding of 1.Cu(I) towards AAOMe.HCl leads to the conformational change, and the Cu(I) complex is simultaneously oxidized to the Cu(II) complex. 相似文献
297.
Site-specific carbohydrate profiling of human transferrin by nano-flow liquid chromatography/electrospray ionization mass spectrometry 总被引:1,自引:0,他引:1
Satomi Y Shimonishi Y Hase T Takao T 《Rapid communications in mass spectrometry : RCM》2004,18(24):2983-2988
Glycopeptides derived from a lysylendopeptidase digest of commercially available human transferrin were analyzed by nano-flow liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), which permitted the carbohydrate profiles at Asn432 and Asn630 to be determined. Both are located in a well-known motif for N-glycosylation, Asn-Xaa-Ser/Thr. The contents of the carbohydrates at each site were significantly different from each other, and consisted of a variety of minor types of oligosaccharides in addition to the major one, a biantennary complex-type oligosaccharide. Nano-flow ESI tandem mass spectrometry (MS/MS) of the glycopeptides (Cys421-Lys433 and Ile619-Lys646) containing these two sites yielded predominantly ions originating from the non-reducing termini (oxonium ions) and reducing terminus, resulting from cleavage of the glycosidic bonds of the carbohydrate moieties; this permitted the structural read-out of a small minority of the carbohydrate moieties. In particular, the observation of oxonium ions at m/z 512.2 and 803.2 is useful for probing outer non-reducing terminal fucosylation, which represented carbohydrate structures consisting of Hex, dHex, and HexNAc, and NeuNAc, Hex, dHex, and HexNAc, respectively, from which the Lewis X structure (Galbeta1-4(Fucalpha1-3)GlcNAc) was readily deduced. Moreover, fucosylation at the reducing-terminal GlcNAc (Fucalpha1-6GlcNAc) specifically occurred at Asn630, as demonstrated by treatment of the glycopeptides with alpha1-3/4-L-fucosidase. 相似文献
298.
Toshifumi Miyazawa Kiwamu Imagawa Hiroe Minowa Toyoko Miyamoto Takashi Yamada 《Tetrahedron》2005,61(43):10254-10261
In the Aspergillus oryzae protease-catalyzed ester hydrolysis, substitution of N-unprotected amino acid esters for the corresponding N-protected amino acid esters resulted in a large enhancement of the hydrolysis rate, while the enantioselectivity was deteriorated strikingly when the substrates employed were the conventional methyl esters. This difficulty was overcome by employing esters bearing a longer alkyl chain such as the isobutyl ester. Utilizing this ester, amino acids carrying an aromatic side chain were resolved with excellent enantioselectivities (E=50 to >200). With amino acids bearing an aliphatic side chain also, good results in terms of the hydrolysis rate and enantioselectivity were obtained by employing such an ester as the isobutyl ester. Moreover, the enantioselectivity proved to be enhanced further by conducting the reaction at low temperature. This procedure was applicable to the case where the enantioselectivity was not high enough even by the use of the isobutyl ester. 相似文献
299.
A cyclobarbital-imprinted polymer was prepared using a fluorescent functional monomer, 2,6-bis(acrylamido)pyridine, and the polymer showed not only selective binding of cyclobarbital but also enhancement of fluorescence intensity, suggesting that the polymer could be utilized as a selective fluorescence probe. 相似文献
300.
An enzyme concerned with the epoxidation of styrenes was isolated from cultured cells of Nicotiana tabacum. The enzyme had peroxidase activity as well as epoxidation activity, and its amino acid sequence showed 89% homology in their 9 amino acid overlap with horseradish peroxidase. In the enzymatic reaction, hydrogen peroxide and p-cresol were necessary and molecular oxygen was the source of the oxygen atom of the epoxide. The enzymatic reaction using a spin trap reagent and monitoring of the reaction with ESR indicated that the epoxidation reaction of styrenes proceeded by a radical mechanism with peroxidase. 相似文献