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891.
Nakazawa T Yamaguchi M Nishida K Kuyama H Obama T Ando E Okamura TA Ueyama N Tanaka K Norioka S 《Rapid communications in mass spectrometry : RCM》2004,18(7):799-807
We have developed a novel method for enhancing the response of a peptide in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) by activating the C-terminal carboxyl group through an oxazolone with which is coupled an amine containing a functional group to help ionize the peptide. The reactions consist of dehydration with acetic anhydride to give an oxazolone, followed by aminolysis with an appropriate amino acid derivative such as arginine methyl ester. The MALDI signal of Ac-Tyr-Gly-Gly-Phe-Leu-Arg-OMe, thus converted from leucine-enkephalin, was detected while completely excluding the responses of arginine-deficient peptides coexisting in the reaction mixture. Some less intense peaks corresponding to a few sequential degradation products, also terminated with the arginine derivative, were also observed. The side-chain groups potentially that are reactive were conveniently protected by acetylation simultaneous with the C-terminal activation, and those that remained unprotected were reduced to virtually negligible proportions when the reaction was conducted in a peptide solution of concentration less than 1 mM. The greatly increased responses of such arginine-terminated peptides could possibly be exploited to discern the C-terminal tryptic peptide of a protein that is otherwise almost insensitive to MALDI-MS in general. The simplicity of the post-source decay spectrum of enkephalin derivatized by arginine methyl ester characteristically accentuated z- and b-type ions, and this should facilitate sequencing of such derivatized peptides. Remaining problems with practical applications of this approach are discussed. 相似文献
892.
Nishino N Jose B Okamura S Ebisusaki S Kato T Sumida Y Yoshida M 《Organic letters》2003,5(26):5079-5082
New inhibitors of histone deacetylase (HDAC) containing a sulfhydryl group were designed on the basis of the corresponding hydroxamic acid (CHAP31) and FK228. Their disulfide dimers and hybrids exhibited potent HDAC inhibitory activity in vivo with potential as anticancer prodrugs. [structure: see text] 相似文献
893.
The specific heat of typical relaxors, Pb(Mg(1/3)Nb(2/3))O3 (PMN) and Pb(Mg(1/3)Ta(2/3))O3 (PMT), was measured by adiabatic and relaxation methods between 2 and 420 K. A broad anomaly was found in the specific heat curve over the wide temperature range between 150 and 500 K for PMN, and between 50 and 400 K for PMT, which provides evidence for the formation of ferroelectric nanoregions (FNR) in the paraelectric matrix. The entropy of the anomaly was estimated as 3.3 J K(-1) mol(-1) and 2.9 J K(-1) mol(-1) for PMN and PMT, respectively, which implies an order-disorder-type mechanism for the formation of FNR. 相似文献
894.
The reactions of various alkenynols with phenylsulfenyl chloride result in the formation of either vinylallene sulfoxides or vnylacetylene sulfoxides, depending on the substitution pattern of the starting material. 相似文献
895.
The steady-state photoelectron currents JL arising from a cathode irradiated by a deuterium lamp in liquid Ar, Ne, He, H2 and N2 near their boiling points were measured for external field strengths of up to 105 V/cm. The current attenuation in the liquids compared to that available from the same light intensity into vacuum Jv, J (JL/Jv), is in reverse order to the dielectric strength of the liquids. This may suggest that the facility of electron injection from the cathode plays an important role in determining the dielectric strength. 相似文献
896.
897.
I. Ogawa T. Idehara A. Sakai K. Yoshida T. Tsuchida K. Kawahata A. Ejiri H. Iguchi K. Tanaka K. Matsuoka R. Akiyama M. Osakabe S. Okamura T. Minami C. Takahashi W. Kasparek 《International Journal of Infrared and Millimeter Waves》1998,19(5):727-736
Intense submillimeter wavelength radiation (f=354 GHz, P=110 W) from Gyrotron FU II is converted into a well-collimated, linearly-polarized beam by a quasi-optical transmission line consisting of a quasi-optical antenna and several mirrors. The observed focusing of the beam agrees with calculations based on the Huygens equation. We have used this intense beam to study low frequency density fluctuations by plasma scattering in Compact Helical System (CHS) plasmas at the National Institute for Fusion Science. 相似文献
898.
Kanae Hayashi Michinori Tachibana Seizo Okamura 《Journal of polymer science. Part A, Polymer chemistry》1980,18(9):2785-2791
Effects of electron beam irradiation on liquid polybutadiene in n-hexane solution were studied at ?10°C. With irradiation, crosslinking of the polymer and loss of double bond by cyclization took place at the same time. These reactions were retarded by the addition of DPPH or triethylamine which indicated that both radical and cationic mechanisms contributed to this system. 相似文献
899.
Takeshi Mori Yasuhisa Fukuda Hirokazu Okamura Keiji Minagawa Seizo Masuda Masami Tanaka 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2651-2658
New thermosensitive polymers were synthesized by copolymerization between N‐vinylacetamide (NVA) and methyl acrylate whose homopolymers are soluble and insoluble in water, respectively. The lower critical solution temperature (LCST) of the obtained copolymers ranged between 59 and 83 °C, and the LCST increased with an increasing NVA content in the copolymers. The effectiveness of various salts addition on lowering the LCST of the copolymer solutions followed Hoffmeister series. NaCl and Na2SO4 addition linearly lowered the LCST with an increasing salts concentration, and slopes of the lines were almost constant regardless of the copolymer composition. The effectiveness of alcohols with various alkyl chain lengths on lowering the LCST did not follow the viscosity B coefficient values of the alcohols, which was probably the result of preferential adsorption of the alcohols to the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2651–2658, 2004 相似文献
900.