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21.
Hayashi T Dejima H Matsuo T Sato H Murata D Hisaeda Y 《Journal of the American Chemical Society》2002,124(38):11226-11227
Myoglobin will be a good scaffold for engineering a function into proteins. To modulate the physiological function of myoglobin, almost all approaches have been demonstrated by site-directed mutagenesis, however, there are few studies which show a significant improvement in the function. In contrast, we focused on the replacement of heme in the protein with an artificial prosthetic group. Recently, we prepared a novel myoglobin reconstituted with an iron porphycene as a structural isomer of mesoheme. The bluish colored reconstituted myoglobin is relatively stable and the deoxymyoglobin reversibly binds ligands. Interestingly, the O2 affinity of the reconstituted myoglobin, 1.1 x 109 M-1, is a significant 1,400-fold higher than that of the native myoglobin. Furthermore, the unfavorable autoxidation kinetics show 7-fold decrease in rate for the reconstituted myoglobin relative to the native myoglobin, indicating the stable oxy-form against autoxidation. The net results come from the slow dissociation of the O2 ligand in the reconstituted myoglobin, koff = 0.11 s-1, because of the formation of strong hydrogen bond between His64 and negatively charged dioxygen. The present study indicates that the replacement of native heme with an artificially created prosthetic group will give us a unique function into a hemoprotein. 相似文献
22.
Yoshio Tanaka Morishige Atsukawa Yukio Shimura Akira Okada Hideki Sakuraba Tokuji Sakata 《Journal of polymer science. Part A, Polymer chemistry》1975,13(5):1017-1028
A soluble and self-crosslinkable linear copolymer with pendant epoxy and pyridyl groups was obtained from glycidyl methacrylate (M1) and 2-vinylpyridine (M2) or 2-vinyl-5-ethylpyridine (M2) by the action of azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C: r1 = 0.510, r2 = 0.620 with 2-vinylpyridine and r1 = 0.57, r2 = 0.62 with 2-vinyl-5-ethylpyridine. These were consistent with the calculated values with the reported Q and e values for these monomers. The intrinsic viscosities of the copolymers with 2-vinylpyridine and with 2-vinyl-5-ethylpyridine were found to be 0.17–0.19 and 0.26–0.38, respectively, in tetrahydrofuran at 30°C; they were independent of the copolymer composition. The copolymers were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents. 相似文献
23.
Yoshio Mimura 《Journal of Number Theory》1981,13(3):415-419
Let L be a lattice in a quadratic space over a non-dyadic local field. We shall answer the question: What are the lattices whose unit groups coincide with that of L? If the residue class field has more than three elements the question is easy. In this case such a lattice must be L or L# with a fractional ideal and the dual lattice L# by Satz 2 of A. Kallmann, M. Kneser, and U. Stuhler (J. Reine Angew. Math.258 (1978), 51–54) or Theorem 5.2 of C. R. Riehm (Amer. J. Math.89 (1967), 549–577). But it is not easy in the case of the residue class field of three elements. 相似文献
24.
Regio- and stereoselective arylation of 2-alkenylpyridines with aryl bromides is catalyzed by specific Ru(II)-phosphine complexes affording beta-arylated (Z)-2-alkenylpyridines, in which the aryl moiety is introduced cis to the pyridyl group. This geometrical selectivity is in sharp contrast to the Mizoroki-Heck reaction. [reaction: see text] 相似文献
25.
Yoshio Okamoto Kazuhiko Urakawa Heimei Yuki 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1385-1395
Asymmetric selective (or stereoelective) polymerization of various racemic methacrylates with cyclohexylmagnesium bromide (c-HexMgBr)-(-)sparteine (1/1.2) catalyst was studied in toluene at ?78°C. The methacrylates of α-ethylbenzyl (EBMA), α-isopropylbenzyl (i-PBMA), α-tert-butylbenzyl (t-BBMA), sec-butyl (s-BuMA), 1-methylallyl (1-MAMA), 2,3-epoxypropyl (2,3-EPMA), 2-phenylpropyl (2-PPMA), and menthyl (MentMA) alcohols were used as racemic monomers. In the polymerization of EBMA and i-PBMA (S) enantiomers were consumed preferentially and the optical purity of initially polymerized i-PBMA was as high as 97%. Optically pure (R) monomers were recovered at about 60% conversion for i-PBMA and 80% for EBMA. In t-BBMA, however, the (R) monomer was consumed preferentially over the (S) isomer. In the polymerization of s-BuMA and 1-MAMA (S) monomers were consumed in excess and the optical purity of the polymers formed in the early stage was about 30%. In 2,3-EPMA and 2-PPMA, which have asymmetric centers at the β position from the ester oxygen, (R) antipodes were more reactive. MentMA did not polymerize at ?78°C. Enantiomer selectivity ratios rS and rR were determined in the polymerization of EBMA, i-PBMA, and 1-MAMA. All polymers except poly(t-BBMA) were highly isotactic, but the tacticity of poly(t-BBMA) could not be estimated. Circular dichroism spectra of optically active polymers of α-substituted benzyl esters were measured. 相似文献
26.
Yoshio Imai Takeyoshi Takahashi Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2841-2845
Two aminophthalide monomers, 6-amino-3-benzylidenephthalide (I) and 3-(p-aminobenzylidene)phthalide (II), underwent self-polycondensation in o-phenylphenol at 250°C to yield polyphthalimidines with inherent viscosities up to 0.5 dL/g. These polymers were readily soluble in a variety of solvents such as dimethylformamide, dimethyl sulfoxide, m-cresol, pyridine, and methylene chloride. The temperatures at which a 10% weight loss occurred by thermogravimetry in nitrogen were 460°C for the polymer derived from I and 490°C for the polymer from II. The glass transition temperature of the polymer from I was 332°C, determined by thermomechanical analysis. 相似文献
27.
Yoshio Masuda 《Thermochimica Acta》1980,39(3):235-241
The thermal dehydration reactions of two kinds of copper(II) formate dihydrate, which differ in origin and preparation history, have been investigated by means of TG, DTA and DSC. The kinetics of isothermal dehydration were studied by weight loss, and the difference in kinetic behavior between these two samples was related to the difference in origin and preparation history. On the whole, the dehydration mechanisms of these two samples were found to be phase boundary controlled contracting interface reactions. 相似文献
28.
Yoshio Masuda 《Thermochimica Acta》1983,60(2):203-210
The thermal dehydration of some rare earth metal formate dihydrates were studied by means of thermogravimetry, differential thermal analysis and differential scanning calorimetry.The dehydration took place successively as a one step reaction for all of the formate dihydrates examined. The reaction order of dehydration was found to be for all of the salts examined, which indicated that the rate of dehydration was controlled by a chemical process at a phase boundary.The values of the activation energy, frequency factor and the enthalpy change of dehydration for all of the dihydrates were 108–142 kJ mole?1, 1016–1017 min?1 and 109–147 kJ mole?1, respectively.Both the temperature at which the dehydration occurred and the enthalpy change increased as the reciprocal of the radius of the metallic ion increased. 相似文献
29.
Mituko Ozima Jun-Ichi Susaki Syun-Iti Akimoto Yoshio Shimizu 《Journal of solid state chemistry》1982,44(3):307-317
Phase relations in the system BaOGeO2 were investigated in the pressure range 20–70 kbar in the temperature range 750–1200°C. Several new phases were identified in this system: an atmospheric phase of BaGe2O5 (monoclinic BaGe2O5 I), two high-pressure phases of BaGe2O5 (monoclinic BaGe2O5 II and tetragonal BaGe2O5 III), and a high-pressure phase of Ba2Ge5O12. The phase boundary curve between BaGe2O5 II and BaGe2O5 III was preliminarily determined as P(kbar) = 7.7 + 0.047T (°C). The high-pressure phases of BaGeO3, which were previously reported by Y. Shimizu, Y. Syono, and S. Akimoto (High Temp.-High Pressures2, 113 (1970)) in the pressure range 15–95 kbar, were interpreted to be not single-phase materials but complicated mixtures of more than two phases in the system BaOGeO2. X-Ray powder diffraction data for the new compounds synthesized in this study are given. 相似文献
30.
Jun-Ichi Asakura Masakuni Yoshihara Yoshio Matsubara Toshihisa Maeshima 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1473-1478
Radical copolymerization of styrene (St, M1) with acrylonitrile (AN, M2) has been carried out using azobisisobutylonitrile as an initiator in benzene, dimethylsulfoxide, acetonitrile, and ethanol at 60 and 80°C. Good linear correlationships were obtained by plotting the values of log r1, log r2, Q2, and e2 against those of vC[dbnd]N and vC[dbnd]C determined in the solvents: the increase in the interaction between AN and the solvent was found to decrease the values of log r1 and e2 but to increase those of log r2 and Q2. The results are discussed in terms of the solvation both in the ground state and in the transition state. 相似文献