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1.
Cosper MM Jameson GN Davydov R Eidsness MK Hoffman BM Huynh BH Johnson MK 《Journal of the American Chemical Society》2002,124(47):14006-14007
The combination of resonance Raman, electron paramagnetic resonance and M?ssbauer spectroscopies has been used to investigate the effect of S-adenosyl-l-methionine (SAM) on the spectroscopic properties of the [4Fe-4S]2+ cluster in biotin synthase. The results indicate that SAM interacts directly at a unique iron site of the [4Fe-4S]2+ cluster in BioB and support the hypothesis of a common inner-sphere mechanism for the reductive cleavage of SAM in the radical SAM family of Fe-S enzymes. 相似文献
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D. Miholová P. Mader J. Száková A. Slámová Z. Svato 《Fresenius' Journal of Analytical Chemistry》1993,345(2-4):256-260
Summary The Trace Element Laboratory of the University of Agriculture in Prague (CSFR) participated successfully in interlaboratory experiments on the determination of the contents of trace elements in seven Czechoslovakian reference materials. Czechoslovakian certified reference material CRM 12-02-01 (Bovine liver) was used for the development of a new analytical method using the Dry Mineralizer Apion as well as in analytical quality assessment of data in the determination of Cd, Pb, and Hg contents in routinely analyzed animal tissues. 相似文献
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Novel meander with Co3+ und Au3+: Na4[AuCoO5] = Na8 1∞ [(O2/2 (CoO)O2AuO2/2)2] By “reaction with the wall” we obtained for the first time transparent brown single crystals of Na4[AuCoO5] while heating intimate mixtures of Co3O4, Na2O2, and K2O2 (Co: Na: K = 1.00:4.91:2.20; 650°C/44d) in a sealed gold-tube: monoclinic, P21/m, with a = 555.69(4) pm, b = 1042.11 (8) pm, c = 555.69(4) pm, β = 117.387(5)°, Z = 2. Characteristic features of Na4[AuCoO5] are meandric chains [(O2/2 (CoO)O2AuO2/2)2]. The structure has been determined by four-circle diffractometer data (Siemens AED 2; Mo? Kα , graphite, 881 I0(hkl), R = 0.0366, Rw = 0.0316), parameters as given in the text. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, these via Mean Fictive Ionic Radii, and Charge-distribution, CHARDI, are calculated and discussed. 相似文献
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Cs4[IrO4], a New Iridate with Planar Anion [IrO4]4? For the first time we obtained black single crystals of Cs4[IrO4] by heating intimate mixtures of CsO0.52 and IrO2 (molar ratio Cs : Ir = 4.30 : 1.00; “Ag-bomb”, 740°C/86 d). Cs4[IrO4] crystallizes monocline, C 2/m, with a = 1031.66(8) pm, b = 671.61(4) pm, c = 660.44(6) pm, b? = 108.118(7)° and Z = 2 in the K4[IrO4]-type. The structure has been determined by four-circle-diffractometer data (PW 1100 from Phillips, Ag? Kα , graphite) with 841 I0(hkl) with I ≥ 3s?(F) (from 947 I0(hkl) out of 3529 measured reflexes). The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. 相似文献
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The electronic structure of cis,trans-(L-N(2)S(2))MoO(X) (where L-N(2)S(2) = N,N'-dimethyl-N,N'-bis(2-mercaptophenyl)ethylenediamine and X = Cl, SCH(2)C(6)H(5), SC(6)H(4)-OCH(3), or SC(6)H(4)CF(3)) has been probed by electronic absorption, magnetic circular dichroism, and resonance Raman spectroscopies to determine the nature of oxomolybdenum-thiolate bonding in complexes possessing three equatorial sulfur ligands. One of the phenyl mercaptide sulfur donors of the tetradentate L-N(2)S(2) chelating ligand, denoted S(180), coordinates to molybdenum in the equatorial plane such that the OMo-S(180)-C(phenyl) dihedral angle is approximately 180 degrees, resulting in a highly covalent pi-bonding interaction between an S(180) p orbital and the molybdenum d(xy) orbital. This highly covalent bonding scheme is the origin of an intense low-energy S --> Mo d(xy) bonding-to-antibonding LMCT transition (E(max) approximately 16000 cm(-)(1), epsilon approximately 4000 M(-)(1) cm(-)(1)). Spectroscopically calibrated bonding calculations performed at the DFT level of theory reveal that S(180) contributes approximately 22% to the HOMO, which is predominantly a pi antibonding molecular orbital between Mo d(xy) and the S(180) p orbital oriented in the same plane. The second sulfur donor of the L-N(2)S(2) ligand is essentially nonbonding with Mo d(xy) due to an OMo-S-C(phenyl) dihedral angle of approximately 90 degrees. Because the formal Mo d(xy) orbital is the electroactive or redox orbital, these Mo d(xy)-S 3p interactions are important with respect to defining key covalency contributions to the reduction potential in monooxomolybdenum thiolates, including the one- and two-electron reduced forms of sulfite oxidase. Interestingly, the highly covalent Mo-S(180) pi bonding interaction observed in these complexes is analogous to the well-known Cu-S(Cys) pi bond in type 1 blue copper proteins, which display electronic absorption and resonance Raman spectra that are remarkably similar to these monooxomolybdenum thiolate complexes. Finally, the presence of a covalent Mo-S pi interaction oriented orthogonal to the MOO bond is discussed with respect to electron-transfer regeneration in sulfite oxidase and Mo=S(sulfido) bonding in xanthine oxidase. 相似文献
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EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
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