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681.
Moali C Anne C Lamotte-Brasseur J Groslambert S Devreese B Van Beeumen J Galleni M Frère JM 《Chemistry & biology》2003,10(4):319-329
The role of the mobile loop comprising residues 60-66 in metallo-beta-lactamases has been studied by site-directed mutagenesis, determination of kinetic parameters for six substrates and two inhibitors, pre-steady-state characterization of the interaction with chromogenic nitrocefin, and molecular modeling. The W64A mutation was performed in IMP-1 and BcII (after replacement of the BcII 60-66 peptide by that of IMP-1) and always resulted in increased K(i) and K(m) and decreased k(cat)/K(m) values, an effect reinforced by complete deletion of the loop. k(cat) values were, by contrast, much more diversely affected, indicating that the loop does not systematically favor the best relative positioning of substrate and enzyme catalytic groups. The hydrophobic nature of the ligand is also crucial to strong interactions with the loop, since imipenem was almost insensitive to loop modifications. 相似文献
682.
683.
A plot of the DISPersion mode of a pure, ideal Lorentzian line versus the Absorption one (DISPA plot) gives a perfect circle. Non-Lorentzian profiles distort this reference circle in an unambiguous way. A modification of the DISPA method for the lineshape analysis of Mössbauer spectra of amorphous Fe83B17 and Fe40Ni40B20 pointed out convolutions of Gaussian and Lorentzian lines to be somewhat superior. Based on the previous results a construction of a hyperfine field distribution is proposed. 相似文献
684.
685.
Milan Mikula Jozef Blecha Michal Čeppan Ján Panák 《Czechoslovak Journal of Physics》1995,45(12):1125-1133
Photoactive TiO2 layers were formed by anodic oxidation of Ti in O2 RF plasma under various conditions and Ti surface pretreatment. The photocurrent spectrum in 1M NaOH was used to calculate the quantum efficiency of the photocurrent production and the band-gap energy for indirect transitions. Photoelectrochemical properties of TiO2 layers were studied on the decomposition of p-cresol water solution. The method of Ti surface pretreatment (mechanical polishing or chemical etching) has a decisive influence on the photoelectrochemical properties and the structure of the polycrystalline oxide, rutile, anatase or amorphous phase content.This study was supported by the Grant Agency for Sciences of Slovakia. 相似文献
686.
687.
Jozef Mikloško 《BIT Numerical Mathematics》1977,17(4):430-436
Let the calculation of thenth term of a general recurrence relation requireO(q(n)) arithmetical operations. The derivation is given of a new algorithm that performsm repetitions of this calculation with different initial conditions requiring onlyO(q(n)) +O(m) operations. The application of this algorithm to accelerate the calculation of continued fractions and the solution of three- and five-diagonal systems of linear equations, is also described. 相似文献
688.
The Freundlich isotherm used in place of the Langmuir isotherm to describe the adsorption mode in the dual sorption theory of glassy polymer—gas systems. Time-lag expressions have been derived and compared with the available corresponding results for the Langmuir case. In the case of large and moderate values of the upstream boundary activity a0, the value of the time-lag function La)(l) calculated with the proposed model is close to that calculated by Paul for the Langmuir isotherm. In the case of small values of a0, the La(l) values predicted by Paul and the proposed model are different and the difference increases when the value of a0 decreases. The ability of the present model to represent systems exhibiting positive deviations from Henry's law is also described. 相似文献
689.
The Use of Computers in Emission Spectroscopy. Part 2. Establishment, Evaluation and Linearization of Analytical Calibration CurvesThe problems of establishing optimum linear calibration plots for atomic emission spectrometry are described, particularly when photographic recording techniques are employed. The calculation procedure, based on the least-squares method, generates additional statistical values which permit linearity to be checked. As the desired linearity is not always achieved at the first attempt, the process is repeated after exclusion of unreliable input data. 相似文献
690.
Jozef Širáň 《Discrete Mathematics》1984,48(1):129-132
A graph is crossing-critical if deleting any edge decreases its crossing number on the plane. It is proved that, for any n ? 3, there is an infinite family of 3-connected crossing-critical graphs with crossing number n. 相似文献