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A homology model of penicillin acylase from Alcaligenes faecalis and in silico evaluation of its selectivity 总被引:1,自引:0,他引:1
Braiuca P Ebert C Fischer L Gardossi L Linda P 《Chembiochem : a European journal of chemical biology》2003,4(7):615-622
A three-dimensional model of the relatively unknown penicillin acylase from Alcaligenes faecalis (PA-AF) was built up by means of homology modeling based on three different crystal structures of penicillin acylase from various sources. An in silico selectivity study was performed to compare this homology model to the structure of the Escherichia coli enzyme (PA-EC) in order to find any selectivity differences between the two enzymes. The program GRID was applied in combination with the principal component analysis technique to identify the regions of the active sites where the PAs potentially engage different interactions with ligands. These differences were further analyzed and confirmed by molecular docking simulations. The PA-AF homology model provided the structural basis for the explanation of the different enantioselectivities of the enzymes previously demonstrated experimentally and reported in the literature. Different substrate selectivities were also predicted for PA-AF compared to PA-EC. Since no crystallographic data are available for PA-AF to date, the three-dimensional homology model represents a useful and efficient tool for fully exploiting this attractive and efficient biocatalyst, particularly in enantioselective acylations of amines. 相似文献
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Misselwitz B Schmitt-Willich H Ebert W Frenzel T Weinmann HJ 《Magma (New York, N.Y.)》2001,12(2-3):128-134
Rationale and objectives: Gadomer-17 is a new magnetic resonance (MR) contrast medium presently in clinical development. It
is a dendritic gadolinium (Gd) chelate carrying 24 Gd ions. This study investigated the pharmacokinetic behavior of this contrast
medium. Methods: The pharmacokinetics of Gadomer-17 were investigated in different species (rat, rabbit, dog, monkey) for
up to 7 days after intravenous (i.v.) injection of 25–100 μmol/kg body weight. In addition, elimination and biodistribution
were evaluated after single i.v. injection of Gadomer-17 in rats. Results: After i.v. injection Gadomer-17 distributes almost
exclusively within the intravascular space without significant diffusion into the interstitial space. The volume of distribution
(Vc) in the initial or α-phase ranged from 0.04 1/kg (rats, rabbits) to 0.06 1 kg (monkeys) and 0.07 1/kg (dogs), which reflects
mainly the plasma volume. The blood/plasma concentration profile was found to be biphasic. The volume of distribution at a
steady state is clearly smaller than that of other contrast media, which distribute to the extracellular space. After single
i.v. injection in rats, the dendritic contrast medium was rapidly and completely eliminated from the body, mainly via glomerular
filtration. No long-term accumulation or retention of the nonmetabolized agent was detectable in organs or tissues. Conclusions:
Gadomer-17 is a promising new MR contrast medium that has an intravascular distribution and a rapid renal elimination. 相似文献
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To mark IEEE Software's 25th anniversary, Software Technology column editor Christof Ebert presents a review and road map of major software technologies, starting with the magazine's inauguration, 1984. Learning from the many hypes and often long introduction cycles, he provides some timeless principles of technology evaluation and introduction. 相似文献
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The authors report on some implementation research that uses judgment capturing (JC) as a tool to reveal where conflicting views and policy ambiguities exist in the organization. This tool describes how differentiation can arise and foster inconsistent views which may be either healthy or dysfunctional. Having revealed these inconsistencies and voids in overall direction for a design project. JC then provides information for a group integrative exercise that leads toward better understanding of engineering design's role for a more unified product development effort 相似文献
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L. M. Gassa J. R. Vilche M. Ebert K. Jüttner W. J. Lorenz 《Journal of Applied Electrochemistry》1990,20(4):677-685
Electrochemical d.c. and a.c. measurements have been carried out on porous Raney nickel in H2-saturated 0.1 M, 1 M, and 6 M NaOH solutions atT=303 K and 333 K using rotating-disc and static-plaar electrodes. For comparison, measurements were also performed on graphite-cloth and graphite-felt electrodes. From polarization curves and current transients obtained in the potential range of the hydrogen evolution and hydrogen oxidation reactions the dependence of the electrocatalytic activity of Raney nickel on the prepolarization conditions was studied. Impedance spectra in the frequency range 1 mHzf 10 kHz were used to determine the characteristic pore parameters and to identify the kinetic behaviour of the porous electrodes by application of transfer function analysis using non-linear fit routines. 相似文献
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Investigating the Role of Conformational Effects on Laccase Stability and Hyperactivation under Stress Conditions
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Dr. Valerio Ferrario Dr. Alexey Chernykh Federica Fiorindo Dr. Marina Kolomytseva Dr. Loris Sinigoi Dr. Nina Myasoedova Dr. Diana Fattor Prof. Dr. Cynthia Ebert Prof. Dr. Ludmila Golovleva Prof. Dr. Lucia Gardossi 《Chembiochem : a European journal of chemical biology》2015,16(16):2365-2372
Fungal laccase from Steccherinum ochraceum 1833 displays remarkable stability under different harsh conditions: organic/buffer mixtures, thermal treatment, and microwave radiation. The behavior is particularly significant in the light of the sharp inactivation observed for two different fungal laccases. Laccase from S. ochraceum 1833 also displays hyperactivation under mild thermal treatment (60 °C). Molecular dynamics simulations at 80 °C explained how this laccase retains the geometry of the electron transfer pathway, thereby assuring electron transfer through the copper ions and thus maintaining its catalytic activity at high temperature. Spectroscopic studies revealed that the thermal activation corresponds to specific conformational changes in the protein. The results indicate that this laccase is potentially applicable under denaturing conditions that might be beneficial for the biotransformation of recalcitrant substrates. 相似文献