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991.
The use of bromide ion as a redox mediator promotes electrochemical reactions in the non-conductive cyclohexane phase. Anodically oxidized species of bromide ion in the conductive methanol phase can bring oxidizing power across phases to induce oxidative disulfide bond formation of a hydrophobically-tagged tripeptide, which is located predominantly in the cyclohexane phase. In addition to commonly used tetraalkylammonium salts, inorganic sodium salt can also be effective alternatives for the bromide source. 相似文献
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Takehiro Watanabe Keisuke Nakanishi Tomoyuki Ozawa Hideya Kawasaki Koichi Ute Ryuichi Arakawa 《Rapid communications in mass spectrometry : RCM》2010,24(13):1835-1841
We have designed a semi‐online liquid chromatography/matrix‐assisted laser desorption/ionization mass spectrometry (LC/MALDI‐MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI‐MS analysis. Our novel semi‐online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,‐hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost‐effective analysis. Using the semi‐online LC/MALDI‐MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size‐exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed‐phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI‐MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size‐exclusion separation; the reversed‐phase separation by interaction with the ODS functions may have less influence on column separation. The semi‐online monolithic capillary LC/MALDI‐MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Tadashi Hayama Yohei Sakaguchi Hideyuki Yoshida Miki Itoyama Kenichiro Todoroki Masatoshi Yamaguchi Hitoshi Nohta 《Rapid communications in mass spectrometry : RCM》2010,24(19):2868-2874
We have developed a novel method for selective and sensitive analysis of sialic acids (N‐acetylneuraminic, N‐glycolylneuraminic, and 2‐keto‐3‐deoxy‐D ‐glycero‐D ‐galactonononic acid) utilizing liquid chromatography/tandem mass spectrometry (LC/MS/MS) combined with a fluorous derivatization technique. In this method, the carboxylic groups in the sialic acids are derivatized via amidation with heptadecafluoroundecylamine, a commercially available perfluoroalkylamine reagent. This reaction proceeds rapidly and readily at room temperature in the presence of a condensation reagent. Subsequently, the derivatives are retained specifically on an LC column with a perfluoroalkyl stationary phase by means of a fluorophilic or 'fluorous' interaction, and detected by positive electrospray ionization MS/MS. The detection limits of the examined sialic acids are in the range of 60–750 amol on column. We show that the proposed method can be used to analyze trace amounts of sialic acids in biological samples. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Yamamoto T Fukushima T Yamamoto Y Kosaka A Jin W Ishii N Aida T 《Journal of the American Chemical Society》2006,128(44):14337-14340
Newly designed norbornene-appended hexabenzocoronene 1 self-assembles, upon diffusion of an Et(2)O vapor into its CH(2)Cl(2) solution, to form either graphitic nanocoils or nanotubes, depending on the self-assembling conditions. The coiled assembly, selectively formed at 15 degrees C, is a kinetic intermediate for the tubular assembly and transforms into nanotubes on standing at 25 degrees C. However, post-ring-opening metathesis polymerization of the norbornene pendants of 1 enhances the thermal stability of the coiled assembly as well as the tubular one and disables a thermodynamic coil-to-tube transition. The polymerized nanocoils show an electroconductivity of 1 x 10(-)(4) S cm(-)(1) upon doping with I(2), while the nonpolymerized nanocoils are disrupted upon being doped. 相似文献
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Maeda H Hasegawa M Hashimoto T Kakimoto T Nishio S Nakanishi T 《Journal of the American Chemical Society》2006,128(31):10024-10025
Phenylethynyl-bridged dipyrrin "dimers" have performed ZnII complexation to give coordination polymers, which provided the fluorescent colloidal spherical objects in solution as well as on the substrate according to the spacer units. Using a mixture of THF and water, unique morphologies, such as bell-shaped and "golf ball"-like architectures, were observed. 相似文献