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An improved homogeneous preparation of adenylate kinase (ATP : AMP phosphotransferase, ATP + AMP S 2 ADP) from baker's yeast was attained by extraction using ethyl acetate and successive column chromatography on Affi-Gel blue, Sephadex G-100, phosphocellulose and Sephacryl S-200. The overall purification is about 670-fold with a yield of 23 % and final specific activity of 1900units/mg protein. The enzyme preparation is a single band in isoelectrofocusing with a PI of 5.7. By sodium dodecyl sulfate gel electrophoresis and gel chromatography the molecular weight is 27 500.Among the nucleoside monophosphates investigated (AMP, CMP, GMP, IMP and UMP) only AMP reacts with ATP (dATP). ATP (dATP) is about one order of magnitude more active than CTP, GTP, ITP and UTP. The enzyme catalyzes only in the presence of a divalent metal cation, namely Mg2+, Ca2+, Co2+, Mn2+ and Ni2+, and the reaction rate is maximal at about 0.5 M NaCl. The binding of the substrates also takes place in the absence of metal. The dissociation constants for ATP, MgATP, CTP, GTP, UTP and AMP are 3.4, 4.2, 18.5, 17.2, 23.8 and 39.3 pM respectively. The amino acid composition of the purified enzyme is: 32 aspartic acid + asparagine, 12 threonine, 12 serine, 27 glutamic acid + glutamine, 16 proline, 21 glycine, 24 alanine, 11 valine, 9 methionine, 17 isoleucine, 25 leucine, 4 tyrosine, 7 phenylalanine, 2 half-cystine (no free sulfhydryl), 23 lysine, 6 histidine, 10 arginine and 2 tryptophan, totalling 260 residues.Adenylate kinase has served as a precedent in the kinetic and physicochemical studies of phosphoryltransferring enzymes. The structure of the enzyme molecule from porcine muscle has been determined by X-ray diffraction [l] and aspects of enzyme substrate interaction have been investigated by X-ray diffraction [2,3] and NMR studies [4-71. One handicap in the study of the mechanism of the catalyzed reaction is the identity of the two distinct and different enzymatic sites with respect to the two substrates bound. One yeast adenylate kinase [8-111. With a view to the study of yeast adenylate kinase as a protein molecule in addition to its kinetic properties, the purification and characterization of this protein was undertaken. Some disagreement with the published work has been found in the course of our investigation. MATERIALS AND METHODSSubstrates and Reazents approach to circumvent the problem of localization of the two binding sites, to better understand the catalytic mechanism and to elucidate aspects of protein evolution, is to isolate and study adenylate kinases from a variety of sources.Russell and co-workers have reported results on the purification, localization and kinetic studies of -

This paper presents a new numerical method to compute the macroscopic electromagnetic properties of the soft magnetic composite (SMC). In present method, SMC is assumed to be composed of homogeneous magnetic bricks with periodicity. The macroscopic electromagnetic properties of SMC are obtained using finite element method in which it is assumed that the homogenized energy is equal to that stored in a unit domain. We compare the macroscopic electromagnetic properties obtained by the present method with those obtained by Ollendorf's formula and magnetic circuit based on the nonmagnetic grain boundary model. It is shown that the three results are in good agreement when assuming constant permeability. It is also found that there are clear discrepancies among them due to magnetic saturations especially when the demagnetization coefficient is large.

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Ba1–xPbxTiO3 powder with a fixed composition was prepared by the reaction of BaTiO3 powders with molten PbCl2at various PbCl2/BaTiO3 molar ratios at 600° and 800°C in a nitrogen atmosphere. When 0.1 μm powder was used, the reaction was finished when x= 0.9. Two phases of BaTiO3and a solid solution of Ba1–xPbxTiO3 coexisted, but the final phase gave a solid solution of Ba1–xPbxTiO3 at 800°C. When 0.5 μm powder was used, the two phases coexisted in the products at 600°C at PbCl2/BaTiO3= 1.0. A sintered compact of Ba1–xPbxTiO3 powders solid solution was prepared by hot isostatic pressing, and its dielectric constant was measured in the temperature range 20°–550°C.