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41.
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
42.
We are reporting on a new method of constructing dearomatized compounds from α-substituted aryltriazenes. Deprotonation occurs at C atom α to N3. Nucleophilic attack of generated anion at the ortho-position of aryl group forms a new carbon-carbon bond. A stereoselective reaction was observed when the substituents on the C α to N3 are tied together in either a pyrrolidine or a piperidine. The product of this reaction possessed an interesting dearomatized tetrahydrobenzotriazine framework. 相似文献
43.
Matsuo Nonoyama 《Transition Metal Chemistry》1982,7(5):281-284
Summary Reactions of palladium(II) chloride with 2-substituted pyridines (HL), 2-(p-R-C6H4-Y)-C5H4N (R = H, CH3, Cl; Y= NH, NCH3, O, S, CH2) form 12 complexestrans-[PdCl2(HL)2], HL being coordinated through a pyridine-N atom. When the ratio PdCl2/HL = 1/1, the pyridine derivatives with Y = NH are cyclopalladated to form another type of complexes [PdClL]2. In [PdClL]2 the deprotonated ligand L is chelated through pyridine-N and phenylortho-C atoms forming an unusual six-membered palladacycle. Like other cyclopalladated complexes containing a five-membered palladacycle, [PdClL]2 reacts with pyridine (py) to form adducts [PdClL(py)]. [Pd(acac)L] and [Pd(dtc)L] were also prepared and characterized (acac=acetylacetonate and dtc =N,Ndimethyldithiocarbamate ion). 相似文献
44.
Yamamoto Y Terui N Tachiiri N Minakawa K Matsuo H Kameda T Hasegawa J Sambongi Y Uchiyama S Kobayashi Y Igarashi Y 《Journal of the American Chemical Society》2002,124(39):11574-11575
Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability. 相似文献
45.
Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids. 相似文献
46.
47.
The preparation and characterization of a series of niobium(V) complexes that incorporate the linear-linked aryloxide trimers 2,6-bis(4,6-dimethylsalicyl)-4-tert-butylphenol [H3(Me-L)] and 2,6-bis(4-methyl-6-tert-butylsalicyl)-4-tert-butylphenol [H3(tBu-L)] are described. The chloride complex [Nb(Me-L)Cl2]2 (1) was prepared in high yield by reaction of NbCl5 with H3(Me-L) in toluene. In contrast, the analogous reaction with H3(tBu-L) gave a mixture of [Nb(tBu-L)Cl2]2 (2) and [Nb(de-tBu-L)Cl2]2 (3a). During the formation of 3a, one of tert-butyl groups at the ortho position in the tBu-L ligand was lost. When the NbCl5/H3(tBu-L) reaction was carried out in acetonitrile, Nb[H(tBu-L)]Cl3(NCMe) (4) was obtained. Heating a solution of 4 in toluene generated 2 and 3a. The isolated complex 4 underwent ligand redistribution in acetonitrile to produce Nb[H(tBu-L)]2Cl(NCMe) (5). Treatment of NbCl5 with Li3(tBu-L) in toluene afforded 2. The chloride ligands in 1 and 2 smoothly reacted with 4 equiv of MeMgI and LiStBu, resulting in [Nb(R-L)Me2]2 [R = Me (6), tBu (7)] and Nb(Me-L)(StBu)2 (8), respectively. A number of the above complexes have been characterized by X-ray crystallography. In the structures of 1, 2, and 6, the R-L ligand is bound to the metal center with a U-coordination mode, while an alternative S-conformation is adopted for 3a and 8. Complexes 4 and 5 contain a bidentate H(tBu-L) diphenoxide-monophenol ligand. 相似文献
48.
Carbon-Fluorine Bondings of Fluorinated Fullerene and Graphite 总被引:1,自引:0,他引:1
Carbon-fluorine bondings of fluorinated fullerenes and fluorine-graphite intercalation compound CxF were investigated in detail on the basis of XPS data and the potential model using the charge distribution calculated by semiempirical method. It has been confirmed by the present study that two peaks in the C1s spectra observed for fluorinated fullerenes are assigned to carbon atoms bonded to fluorine atoms and those unbound to fluorine atoms, and the small difference in charges and Madelung potentials of fluorine atoms in different circumstances well explains the single peak in F1s spectra of fluorinated fullerenes. In the calculated structures of 1,3-C60F2 and 1,2-C60Fx (x = 2?6) used as the models of CxF, three kinds of carbon-fluorine bondings were observed corresponding to nearly ionic, semicovalent and covalent C? F bondings. The calculated result supports that the bi-intercalation structure of stage 1 CxF consists of nearly ionic and semi-covalent fluorines. 相似文献
49.
Fukuyama Y Minami H Matsuo A Kitamura K Akizuki M Kubo M Kodama M 《Chemical & pharmaceutical bulletin》2002,50(3):368-371
New five seven-membered vibsane-type diterpenes named 5-epi-vibsanin C, 5-epi-vibsanin H, 5-epi-vibsanin K, 18-O-methyl-5-epi-vibsanin K and 5-epi-vibsanin E have been isolated from the leaves of Viburnum awabuki (Caplifoliaceae). Their structures have been elucidated by analyses of spectroscopic data and comparison of their spectral data with those of the previously known seven-membered vibsane-type diterpenes. The occurrence of these seven-membered vibsane-type diterpenes with a cis relationship on the C-5 and C-10 positions in nature have been predicted by conformational analysis of vibsanin B, an eleven-membered vibsane-type diterpene. Vibsanin C, 5-epi-vibsanin C and 5-epi-vibsanin H exhibited moderate cytotoxic activities on KB cells. 相似文献
50.
A family of tantalum compounds supported by the triaryloxide [R-L]3− ligands are reported [H3(R-L) = 2,6-bis(4-methyl-6-R-salicyl)-4-tert-butylphenol, where R = Me or tBu]. The reaction of H3[Me-L] with TaCl5 in toluene gave [(Me-L)TaCl2]2 (1). The [tBu-L] analogue [(tBu-L)TaCl2]2 (2) was synthesized via treatment of TaCl5 with Li3[tBu-L]. A THF solution of LiBHEt3 was added to 1 in toluene to provide [(Me-L)TaCl(THF)]2 (3), while treatment of 2 with 2 equiv of LiBHEt3 or potassium in toluene followed by recrystallization from DME resulted in formation of [M(DME)3][{(tBu-L)TaCl}2(μ-Cl)] [M = Li (4a), K (4b)]. When the amount of MBHEt3 (M = Li, Na, K) was increased to 5 equiv, the analogous reactions in toluene afforded [{(bit-tBu-L)Ta}2(μ-H)3M] [M = Li(THF)2 (5a), Na(DME)2 (5b), K(DME)2 (5c)]. During the course of the reaction, the methylene CH activation of the ligand took place. Dissolution of 5a in DME produced [{(bit-tBu-L)Ta}2(μ-H)3Li(DME)2] (6), indicating that the coordinated THF molecules are labile. When the 2/LiBHEt3 reaction was carried out in THF, the ring opening of THF occurred to yield [(tBu-L)Ta(OBun)2]2 (7) along with a trace amount of [Li(THF)4][{(tBu-L)TaCl}2(μ-OBun)] (8). Treatment of 2 with potassium hydride in DME yielded [{(tBu-L)TaCl2K(DME)2}2(μ-OCH2CH2O)] (9), in which the ethane-1,2-diolate ligand arose from partial C-O bond rupture of DME. The X-ray crystal structures of 2, 3, 4, 5a, 6, 7, and 9 are described. 相似文献