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751.
The prochiral tertiary amine N-ethyl-N-methylaniline (EMA) is known to be metabolically N-oxygenated in vitro with microsomal preparations. This biotransformation is thought to be mediated predominantly by the flavin-containing monooxygenase (FMO) enzyme system. Microsomal N-oxygenation of EMA is known to be stereoselective and varies between species. In order to further characterise this metabolic transformation, we have examined the in vitro metabolism of EMA using purified porcine hepatic FMO. Following incubation of EMA with purified FMO, EMA N-oxide, the only metabolite detected, was found to be produced stereoselectively [ratio (?)-(S):(+)-(R), ca. 4:1]. The enantiomeric ratio of the N-oxide product did not change markedly with respect to time, enzyme or substrate concentration. Determination of the kinetics of formation of the N-oxide indicated a single affinity for the prochiral substrate with differential rates of formation of the enantiomers. The extent of EMA N-oxide formation was shown to be affected by activators and inhibitors of FMO and pH, but its stereoselectively was unaltered. © 1994 Wiley-Liss, Inc. 相似文献
752.
Ian Whalley Asser Tantawi Malgorzata Steinder Mike Spreitzer Giovanni Pacifici Rajarshi Das David M. Chess 《Cluster computing》2006,9(4):401-416
This paper presents an autonomic system in which two managers with different responsibilities collaborate to achieve an overall
objective within a cluster of server computers. The first, a node group manager, uses modeling and optimization algorithms
to allocate server processes and individual requests among a set of server machines grouped into node groups, and also estimates
its ability to fulfill its service-level objectives as a function of the number of server machines available in each node
group. The second, a provisioning manager, consumes these estimates from one or more node group managers, and uses them to
allocate machines to node groups over a longer timescale. We describe the operation of both managers and the information that
flows between them, and present the results of some experiments demonstrating the effectiveness of our technique. Furthermore,
we relate our architecture to a general autonomic computing architecture based on self-managing resources and patterns of
inter-resource collaboration, and to emerging standards in the area of distributed manageability. We also discuss some of
the issues involved in incorporating our implementation into existing products in the short term, and describe a number of
further directions for this research. 相似文献
753.
Color carboxymethylation of cysteine residues with a new chromophoric reagent dimethylaminoazobenzene iodoacetamide, was applied to the micro-sequence analysis of hirudin, a thrombin specific inhibitor. Six cysteine residues of the reduced hirudin were detected as colored phenylthiohydantoin derivative and 3 tryptic peptides of hirudin (all containing cysteines) were isolated as colored peptide. The complete hirudin sequence, including 6 uncertain positions left in the previous report [Petersen T.E. (1976) in: Protides of the Biological Fluids; 23rd Colloquium, pp. 145, Pergamon Press, London] was established. 相似文献
754.
Replica exchange molecular dynamics (MD) simulations of Met-enkephalin in explicit solvent reveal helical and nonhelical structures. Four predominant structures of Met-enkephalin are sampled with comparable probabilities (two helical and two nonhelical). The energy barriers between these configurations are low, suggesting that Met-enkephalin switches easily between configurations. This is consistent with the requirement that Met-enkephalin be sufficiently flexible to bind to several different receptors. Replica exchange simulations of 32 ns are shown to sample approximately five times more configurational space than constant temperature MD simulations of the same duration. The energy landscape for the replica exchange simulation is presented. A detailed study of replica trajectories demonstrates that the significant increases in temperature provided by the replica exchange technique enable transitions from nonhelical to helical structures that would otherwise be prevented by kinetic trapping. Met-enkephalin (Type Entrez Proteins; Value A61445; Service Entrez Proteins). 相似文献
755.
Wim J.B. Wannet Huub J.M. Op den Camp Hendrik W. Wisselink Chris van der Drift Leo J.L.D. Van Griensven Godfried D. Vogels 《Biochimica et Biophysica Acta (BBA)/General Subjects》1998,1425(1):177-188
Trehalose phosphorylase (EC 2.4.1.64) from Agaricus bisporus was purified for the first time from a fungus. This enzyme appears to play a key role in trehalose metabolism in A. bisporus since no trehalase or trehalose synthase activities could be detected in this fungus. Trehalose phosphorylase catalyzes the reversible reaction of degradation (phosphorolysis) and synthesis of trehalose. The native enzyme has a molecular weight of 240 kDa and consists of four identical 61-kDa subunits. The isoelectric point of the enzyme was pH 4.8. The optimum temperature for both enzyme reactions was 30°C. The optimum pH ranges for trehalose degradation and synthesis were 6.0–7.5 and 6.0–7.0, respectively. Trehalose degradation was inhibited by ATP and trehalose analogs, whereas the synthetic activity was inhibited by Pi (Ki=2.0 mM). The enzyme was highly specific towards trehalose, Pi, glucose and α-glucose-1-phosphate. The stoichiometry of the reaction between trehalose, Pi, glucose and α-glucose-1-phosphate was 1:1:1:1 (molar ratio). The Km values were 61, 4.7, 24 and 6.3 mM for trehalose, Pi, glucose and α-glucose-1-phosphate, respectively. Under physiological conditions, A. bisporus trehalose phosphorylase probably performs both synthesis and degradation of trehalose. 相似文献
756.
757.
758.
Valarie Byford Stephen Strugnell Ruth Coldwell Neil Schroeder Hugh L.J Makin Joyce C Knutson Charles W Bishop Glenville Jones 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2002,1583(2):151-166
In this study, we used molecules with either of the structural differences in the side chains of vitamin D2 and vitamin D3 to investigate which feature is responsible for the significant differences in their respective metabolism, pharmacokinetics and toxicity. We used two cell model systems—HepG2 and HPK1A-ras—to study hepatic and target cell metabolism, respectively. Studies with HepG2 revealed that the pattern of 24- and 26-hydroxylation of the side chain reported for 1α-hydroxyvitamin D2 (1α-OH-D2) but not for 1α-OH-D3 is also observed in both 1α-OH-D4 and Δ22-1α-OH-D3 metabolism. This suggests that the structural feature responsible for targeting the enzyme to the C24 or C26 site could be either the C24 methyl group or the 22–23 double bond. In HPK1A-ras cells, the pattern of metabolism observed for the 24-methylated derivative, 1α,25-(OH)2D4, was the same pattern of multiple hydroxylations at C24, C26 and C28 seen for vitamin D2 compounds without evidence of side chain cleavage observed for vitamin D3 derivatives, suggesting that the C24 methyl group plays a major role in this difference in target cell metabolism of D2 and D3 compounds. Novel vitamin D4 compounds were tested and found to be active in a variety of in vitro biological assays. We conclude that vitamin D4 analogs and their metabolites offer valuable insights into vitamin D analog design, metabolic enzymes and maybe useful clinically. 相似文献
759.
GERD GÄDE 《Physiological Entomology》1989,14(4):405-418
ABSTRACT. The corpora cardiaca of the stick insect, Sipyloidea sipylus Westwood, contain peptidic material which elevates blood lipids in migratory locusts, blood carbohydrates in American cockroaches, and activates glycogen phosphorylase in the fat body of the cockroach in a time- and dose-dependent manner. The active principle is found in appreciable amounts only in the corpora cardiaca; slight hyperlipaemia is caused by extracts made from corpora allata and abdominal ganglia, whereas brain, suboesophageal and thoracic ganglia are not active. The adipokinetic activity is already present in corpora cardiaca from second instar (first day) nymphs. The factor retains its adipokinetic activity after boiling for up to 1 h. Conspecific injections of extracts from corpora cardiaca of S.sipylus cause hypertrehalosaemia in ligated stick insects and activate glycogen phosphorylase in non-ligated S.sipylus. After incubation of corpora cardiaca in vitro in saline with high concentrations of potassium and calcium, one fraction with adipokinetic (in locusts) and hypertrehalosaemic (in stick insects) activity can be isolated from the medium by RP-HPLC. Fractionation of a methanolic extract of corpora cardiaca from S.sipylus by RP-HPLC shows that active compounds are confined to apparently three absorbance peaks. The material of the highest absorbance peak was purified to homogeneity by RP-HPLC, and its amino acid composition determined after acid hydrolysis with HCl and with methanesulfonic acid revealed the residues Asx, Thr(3), Glx, Pro, Gly, Leu, Phe and Trp. The primary structure of this hypertrehalosaemic factor is assigned as a blocked decapeptide, pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2, from its FAB spectrum and metastable scans of its FAB spectrum. The structure is confirmed by synthesis; the synthetic and natural peptide co-chromatograph, and the synthetic peptide elevates blood carbohydrates in ligated stick insects and activates fat body phosphorylase in non-ligated S.sipylus. 相似文献
760.
Baker Abdalhaq Ana Cortés Tomàs Margalef Germán Bianchini Emilio Luque 《Cluster computing》2006,9(3):329-343
One of the challenges still open to wildland fire simulators is the capacity of working under real-time constrains with the
aim of providing fire spread predictions that could be useful in fire mitigation interventions. We propose going one step
beyond the classical wildland fire prediction by linking evolutionary optimization strategies to the traditional scheme with
the aim of emulating an “ideal” fire propagation model as much as possible. In order to accelerate the fire prediction, this
enhanced prediction scheme has been developed in a fashion on a Linux cluster using MPI. Furthermore, a sensitivity analysis
has been carried out to determine the input parameters that we can fix to their typical values in order to reduce the search-space
involved in the optimization process and, therefore, accelerates the whole prediction strategy.
Baker Abdalhaq received the BSc. Computer Science from Princess Sumaya University College, Royal JordanianSocieaty, Amman Jordania in 1993.
In 2001 and 2004, he got the MSc and PhD in Computer Science from Universitat Autónoma de Barcelona (UAB), respectively. His
main research interest is focused on parallel fire simulation and, in particular, how to take advantage of the computational
power provided for massively distributed systems to enhance wildland fire prediction.
Ana Cortés received both her first degree and her PhD in Computer Science from the Universitat Autonoma de Barcelona (UAB), Spain, in
1990 and 2000, respectively. She is currently assistant professor of Computer Science at the UAB, where she is a member of
the Computer Architecture and Operating Systems Group at the Computer Science Department. Her current research interests concern
software support for parallel and distributed computing including algorithms and software tools for the load-balancing of
parallel programs. She has also been working on enhancing wildland fire prediction by exploiting parallel/distributed systems.
Tomàs Margalef got a BS degree in physics in 1988 from Universitat Autónoma de Barcelona (UAB). In 1990 he obtained the MSc in Computer
Science and in 1993 the PhD in Computer Science from UAB. Since 1988 he has been working in several aspects related to parallel
and distributed computing. Currently, his research interests focuses on development of high performance applications, automatic
performance analysis and dynamic performance tuning. Since 1997 he has been working on exploiting parallel/distributed processing
to accelerate and improve the prediction of forest fire propagation. He is an ACM member.
Germán Bianchini received the BSc. Computer Science from Universidad Nacional Del Comahue, Argentina, in 2002. In 2004 and 2006, he got the
MSc and PhD in Computer Science from Universitat Autónoma de Barcelona (UAB), respectively. His main research interest is
focused on parallel fire simulation and, in particular, how to take advantage of the computational power provided for massively
distributed systems to enhance wildland fire prediction.
Emilio Luque received the Licenciate in physics and PhD degrees from the University Complutense of Madrid (UCM) in 1968 and 1973 respectively.
Between 1973 and 1976 he was an associate professor at the UCM. Since 1976 he is a professor of “Computer Architecture and
Technology” at the University Autonoma of Barcelona (UAB), where he is leading the Computer Architecture and Operating System
(CAOS) Group at the Computer Science Department. Professor Luque has been the Computer Science Department chairman for more
than 10 years. He has been invited lecturer/researcher in Universities of USA, Argentina, Brazil, Poland, Ireland, Cuba, Italy,
Germany and PR of China. He has published more than 35 papers in technical journals and more than 100 papers at international
conferences and his current/major research areas are: computer architecture, interconnection networks, task scheduling in
parallel systems, parallel and distributed simulation environments, environment and programming tools for automatic performance
tuning in parallel systems, cluster and Grid computing, parallel computing for environmental applications (forest fire simulation,
forest monitoring) and distributed video on demand (VoD) systems. 相似文献