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31.
From the standpoint of protein dynamics and metalloprotein design, it is interesting to create an artificial protein which induces structural change and regulates its function by metal-ion binding. We engineered a novel protein, "Antennafinger (Ant-F)", whose structure and function can be controlled with Zn(II), by introducing the consensus sequence of a Cys(2)His(2)-type zinc finger protein into a non-metalloprotein scaffold, an Antennapedia homeodomain mutant (Ant-wt), selected using a motif-searching system. The circular dichroism studies demonstrate that Ant-F has secondary structures similar to Ant-wt and also changes its conformation due to Zn(II)-binding. The optical absorption spectra of the Co(II) complexes of Ant-F and its derivative proteins suggest that the geometry of the metal center of holo-Ant-F is tetrahedral and that the mutated Cys(2)His(2) residues are involved in the complex formation. In addition, the gel mobility shift assay reveals that the DNA binding activity of Ant-F can be regulated through Zn(II)-induced structural alteration. These results provide valuable information about the dynamic properties of proteins and a novel concept for metalloprotein design. 相似文献
32.
An air-segmented continuous-flow method has been developed for the determination of molybdenum at ultra trace levels using
the catalytic effect of molybdate during the oxidation of L-ascorbic acid by hydrogen peroxide. Incorporation of an on-line
ion exchange column improved the tolerance limit for various ions. The detection limits with and without the column were 64 pmol L−1 and 17 pmol L−1, and the reproducibilities at 10 nmol L−1 were 2.1% and 0.2%, respectively. The proposed method was applied to the determination of molybdenum in seawater and lake
water as well as in rock and sediment samples. This method has the highest sensitivity among the available literature to our
knowledge, and is also convenient for routine analysis of molybdenum in various natural samples.
Author for correspondence. E-mail: masahito.sugiyama@ sojin0206.mbox.media.kyoto-u.ac.jp
Received October 23, 2002; accepted January 28, 2003
Published online May 19, 2003 相似文献
33.
Matsuo T Dejima H Hirota S Murata D Sato H Ikegami T Hori H Hisaeda Y Hayashi T 《Journal of the American Chemical Society》2004,126(49):16007-16017
Sperm whale myoglobin, an oxygen storage hemoprotein, was successfully reconstituted with the iron porphycene having two propionates, 2,7-diethyl-3,6,12,17-tetramethyl-13,16-bis(carboxyethyl)porphycenatoiron. The physicochemical properties and ligand bindings of the reconstituted myoglobin were investigated. The ferric reconstituted myoglobin shows the remarkable stability against acid denaturation and only a low-spin characteristic in its EPR spectrum. The Fe(III)/Fe(II) redox potential (-190 mV vs NHE) determined by the spectroelectrochemical measurements was much lower than that of the wild-type. These results can be attributed to the strong coordination of His93 to the porphycene iron, which is induced by the nature of the porphycene ring symmetry. The O2 affinity of the ferrous reconstituted myoglobin is 2600-fold higher than that of the wild-type, mainly due to the decrease in the O2 dissociation rate, whereas the CO affinity is not so significantly enhanced. As a result, the O2 affinity of the reconstituted myoglobin exceeds its CO affinity (M' = K(CO)/K(O2) < 1). The ligand binding studies on H64A mutants support the fact that the slow O2 dissociation of the reconstituted myoglobin is primarily caused by the stabilization of the Fe-O2 sigma-bonding. The IR spectra for the carbon monoxide (CO) complex of the reconstituted myoglobin suggest several structural and/or electrostatic conformations of the Fe-C-O bond, but this is not directly correlated with the CO dissociation rate. The high O2 affinity and the unique characteristics of the myoglobin with the iron porphycene indicate that reconstitution with a synthesized heme is a useful method not only to understand the physiological function of myoglobin but also to create a tailor-made function on the protein. 相似文献
34.
35.
Masahito Segi Hiroaki Yamamoto Takeyoshi Hori Tadashi Nakajima 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):599-602
Selenoaldehydes and selenoketones, generated by thermal retro-Diels-Alder reaction of their cycloadducts with cyclopentadiene, reacted with oxygen-functionalized conjugated dienes such as 1-acetoxy-1,3-butadiene, Danishefsky's diene, and 1,4-diacetoxy-1,3-butadiene to give the corresponding cycloadducts in good yields regioselectively. 相似文献
36.
Abstract With a 1:1 and a 2:1 host-guest stoichiometry, α-cyclodextrin (α-CD) forms inclusion complexes with 2-chloronaphthalene. From simulations concerning observed chemical-shift differences (Δδobs) of proton signals of 2-chloronaphthalene, intrinsic Δδ values are estimated for all the guest protons in the 1:1 and 2:1 inclusion complexes. The intrinsic Δδ values indicate that α-CD first binds to a part of a naphthalene ring bearing a C1 atom to form the 1:1 inclusion complex. In the 1:1 and 2:1 inclusion complexes, the symmetry axes of α-CD are tilted approximately 30° relative to a naphthalene longitudinal axis. In the 2:1 inclusion complex, the association through hydrogen bonding most likely occurs between two α-CD molecules whose symmetry axes are laterally shifted. 相似文献
37.
We present tamper resistance in optical excitation transfer via optical near-field interactions based on the energy dissipation process occurring locally in nanometric devices such as quantum dots. A theoretical comparison with electrical systems is also shown, focusing on the required environmental conditions. Numerical simulations based on virtual photon models demonstrate high tamper resistance. 相似文献
38.
Stable conformations of 12-crown-O3N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O3N and its Li+ complex, our procedure was to make use of two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O3N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li+ changes depending on the distance between the cation and the crown ring. 相似文献
39.
Uto Y Hirata A Fujita T Takubo S Nagasawa H Hori H 《The Journal of organic chemistry》2002,67(7):2355-2357
We have demonstrated that prenylation of p-halophenols was dependent on the solvent effect and succeeded in o,o'-diprenylation of p-halophenols in water. Following the Mizoroki-Heck coupling of the diprenyl-p-iodophenol 3c with methyl acrylate and then hydrolysis, we first synthesized artepillin C [3-(4-hydroxy-3,5-di(3-methyl-2-butenyl)phenyl)-2(E)-propenoic acid] (1), which is a biologically active constituent of propolis. These reactions may be applicable to the synthesis of various useful natural products such as 2,4,6-trisubstituted phenol derivatives. 相似文献
40.
Widmann E Eades J Ishikawa T Sakaguchi J Tasaki T Yamaguchi H Hayano RS Hori M Torii HA Juhász B Horváth D Yamazaki T 《Physical review letters》2002,89(24):243402
Using a newly developed laser-microwave-laser resonance method, we observed a pair of microwave transitions between hyperfine levels of the (n,L)=(37,35) state of antiprotonic helium. This experiment confirms the quadruplet hyperfine structure arising from the interaction of the antiproton orbital angular momentum, the electron spin and the antiproton spin as predicted by Bakalov and Korobov. The measured frequencies of nu(+)(HF)=12.895 96+/-0.000 34 GHz and nu(-)(HF)=12.924 67+/-0.000 29 GHz agree with recent theoretical calculations on a level of 6x10(-5). 相似文献