The steady state

In the course of current research the procedure of obtaining of the piecewise linear vibration systems time and frequency responses have been developed. The method is partly analytical and partly numerical and is based on combining of linear solutions of different sections in a cycle of motion. In a row with the method of obtaining of the exact steady state time and frequency response, also it is provided sensitivity analysis of the vibration isolator.

86p runthenight07 01-03-2023 10 3   Download

The aim of the study is to design, analysis and optimization of piston for a single cylinder four stroke over head valve (OHV) spark ignition engine. This paper used reverse engineering techniques, in order to obtain of an existing physical model.

11p lucastanguyen 01-06-2020 21 1   Download

The design of b-glycosidases with planed substrate specificity for biotechnological application has received little attention. This is mostly a consequence of the lack of data on the molecular basis of the b-glycosidase specificity, namely data on the energy of the noncovalent interactions in the enzymetransition state complex. In an attempt to fill this gap, sitedirected mutagenesis and enzyme steady-state kinetic experiments with different substrates were conducted, using as model a digestive b-glycosidase (glycoside hydrolase family 1) from Spodoptera frugiperda (Lepidoptera) (Sfbgly50).

10p system191 01-06-2013 41 4   Download

Pyruvate decarboxylase (EC 4.1.1.1) was isolated and purified from the yeast Kluyveromyces lactis. The properties of this enzyme relating to the native oligomeric state, the subunit size, the nucleotide sequence of the coding gene(s), the catalytic activity, and protein fluorescence as well as circular dichroism are very similar to those of the well characterized pyruvate decarboxylase species from yeast.

8p system191 01-06-2013 41 3   Download

Modelling of the fluxes in central metabolism can be performed by combining labelling experiments with metabolite balancing. Using this approach, multiple samples from a cultivation of Saccharomyces cerevisiae in metabolic and isotopic steady state were analysed, and the metabolic fluxes in central metabolism were estimated. In the various samples, the estimates of the central metabolic pathways, the tricarboxylic acid cycle, the oxidative pentose phosphate pathway and the anaplerotic pathway, showed an unprecedented reproducibility....

6p system191 01-06-2013 41 2   Download

Cloning and over-expression of human glucose 6-phosphate dehydrogenase (Glc6P dehydrogenase) has for the first time allowed a detailed kinetic study of a preparation that is genetically homogeneous and in which all the protein molecules are of identical age. The steady-state kinetics of the recombinant enzyme, studied by fluorimetric initial-rate measurements, gave converging linear Lineweaver–Burk plots as expected for a ternary-complex mechanism.

8p research12 01-06-2013 59 4   Download

CTP synthase catalyzes the reaction glutamine + UTP +ATPfiglutamate + CTP + ADP + Pi.The rate of the reaction is greatly enhanced by the allosteric activator GTP.We have studied the glutaminase half-reactionofCTP synthase from Lactococcus lactisand its response to the allosteric activator GTP and nucleotides that bind to the active site. In contrast to what has been found for the Escherichia colienzyme, GTP activation of the L. lactis enzyme did not result in similarkcat values for the glutami-nase activity and glutamine hydrolysis coupled to CTP synthesis. ...

8p research12 29-04-2013 44 2   Download

Traditional analyses of the control and regulation of steady-state concentrations and fluxes assume the activities of the enzymes to be constant. In living cells, a hierar-chical control structure connects metabolic pathways to signal-transduction and gene-expression. Consequently, enzyme activities are not generally constant. This would seem to compromise analyses of control and regulation at the metabolic level.

10p research12 23-04-2013 49 2   Download

cAMP receptor protein (CRP), allosterically activated by cAMP, regulates the expression of several genes inEscheri-chia coli. As binding of cAMP leads to undefined conform-ational changes in CRP, we performed a steady-state and time-resolved fluorescence study to showhow the binding of the ligand influences the structure and dynamics of the protein. We used CRP mutants containing a single trypto-phan residue at position 85 or 13, and fluorescently labeled with 1,5-I-AEDANS attached toCys178.

11p tumor12 20-04-2013 31 3   Download

Human alcohol dehydrogenase 3/glutathione-dependent formaldehyde dehydrogenase was shown to rapidly and irreversibly catalyse the reductive breakdown of S-nitroso-glutathione. The steady-state kinetics of S-nitrosogluta-thione reduction was studied for the wild-type and two mutated forms of human alcohol dehydrogenase 3, muta-tions that have previously been shown to affect the oxidative efficiency for the substrate S-hydroxymethylglutathione.

8p tumor12 20-04-2013 32 2   Download

Heterologous expression of the putative open reading frame MJ0303 ofMethanococcus jannaschiiprovided a recombin-ant protein catalysing the formation of the riboflavin precursor, 6,7-dimethyl-8-ribityllumazine, by condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and 3,4-dihydroxy-2-butanone 4-phosphate. Steady state kinetic analysis at 37
C and pH 7.0 indicated a catalytic rate of 11 nmolÆmg )1 Æmin )1 ;Kmvalues for 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and 3,4-dihydroxybutanone 4-phosphate were 12.5 and 52lM, respectively....

8p tumor12 20-04-2013 37 3   Download

Human novel reductase 1 (NR1) is an NADPH dependent diflavin oxidoreductase related to cytochrome P450reduc-tase (CPR). The FAD/NADPH- and FMN-binding domains of NR1 have been expressed and purified and their redox properties studied by stopped-flow and steady-state kinetic methods, and by potentiometry.

12p tumor12 20-04-2013 41 2   Download

The influence of temperature on cytochromec oxidase (CCO) catalytic activity was studied in the temperature range 240–308 K. Temperatures below 273 K required the inclusion of the osmolyte ethylene glycol. For steady-state activity between 278 and 308 K the activation energy was 12 kcalÆmol )1 ; the molecular activity or turnover number was 12 s )1 at 280K in the absence of ethylene glycol. CCO activity was studied between 240and 277 K in the presence of ethylene glycol.

8p tumor12 20-04-2013 33 4   Download

We introduce the basic concepts and develop a theory for nonequilibrium steady-state biochemical systems applicable to analyzing large-scale complex isothermal reaction networks. In terms of the stoichiometric matrix, we dem-onstrate both Kirchhoff’s flux lawR‘J‘ ¼0 over a bio-chemical species, and potential law R‘l‘ ¼0overa reaction loop. They reflect mass and energy conservation, respectively.

7p tumor12 20-04-2013 45 3   Download

The peroxidase–oxidase reaction is known to involve react-ive oxygen species as intermediates. These intermediates inactivatemany types of biomolecules, including peroxidase itself. Previously,wehave shown that oscillatorydynamics in the peroxidase–oxidase reaction seem to protect the enzyme frominactivation. It was suggested that this is due to a lower average concentration of reactive oxygen species in the oscillatory state compared to the steady state. Here, we studied the peroxidase–oxidase reaction with either 4-hydroxybenzoic acid or melatonin as cofactors. ...

9p fptmusic 16-04-2013 45 4   Download

Amathematicalmodel hasbeendevelopedtostudy theeffect of external tryptophan on the trp operon. The model accounts for the effect of feedback repression by tryptophan through the Hill equation. We demonstrate that the trp operonmaintains an intracellular steady-state concentration in a fivefold range irrespective of extracellular conditions. Dynamic behavior of thetrp operon corresponding to varying levels of extracellular tryptophan illustrates the adaptive nature of regulation.

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Thrombomodulin (TM) slows down the interaction rate between thrombin and plasminogen activator inhibitor 1 (PAI-1). We now show that the 12-fold reduced inhibition rate in the presence ofTM does not result from an altered distribution between PAI-1 cleavage and irreversible com-plex formation. Surface plasmon resonance (SPR) revealed an over 200-fold reduced affinity of TM for thrombin-VR1 tPA as compared to thrombin, demonstrating the importance ofthe VR1 loop in the interaction ofthrombin withbothTMandPAI-1....

10p fptmusic 16-04-2013 42 3   Download

The structural features of the hyperthermophilic endo-b-1,3-glucanase from Pyrococcus furiosuswere studied using circular dichroism, steady-state and time-resolved fluorescence spectroscopy and anisotropy. Upon heat and chemical treatment the folded and denatured states of the protein were characterized by distinguishable spectral profiles that identified a number of conformational states.

13p fptmusic 12-04-2013 39 2   Download

Cyclins are the essential regulatory subunits of cyclin-dependent protein kinases. They accumulate and disappear periodically at specific phases of the cell cycle. Here we investigated whether variations in cyclin mRNA levels in exponentially growing cells can be attributed to changes in mRNA stability. Mouse EL4 lymphoma cells and 3T3 fibroblasts were synchron-ized by elutriation or cell sorting.

13p fptmusic 12-04-2013 57 3   Download

Purified recombinant proteins fromSynechocystisPCC6803 were used to show that the magnesium chelatase ChlH subunit stimulates magnesium protoporphyrin methyltransferase (ChlM) activity. Steady-state kinetics demonstrate that ChlH does not significantly alter theKmfor the tetrapyr-role substrate. However, quenched-flow analysis reveals that ChlH dramat-ically accelerates the formation and breakdown of an intermediate in the catalytic cycle of ChlM.

8p fptmusic 12-04-2013 45 2   Download