Allosteric Control of Substrate Specificity of the Escherichia coli ADP-Glucose Pyrophosphorylase

The substrate specificity of enzymes is crucial to control the fate of metabolites to different pathways. However, there is growing evidence that many enzymes can catalyze alternative reactions. This promiscuous behavior has important implications in protein evolution and the acquisition of new functions. The question is how the undesirable outcomes of in vivo promiscuity can be prevented. ADP-glucose pyrophosphorylase from Escherichia coli is an example of an enzyme that needs to select the correct substrate from a broad spectrum of alternatives. This selection will guide the flow of carbohydrate metabolism toward the synthesis of reserve polysaccharides. Here, we show that the allosteric activator fructose-1,6-bisphosphate plays a role in such selection by increasing the catalytic efficiency of the enzyme toward the use of ATP rather than other nucleotides. In the presence of fructose-1,6-bisphosphate, the kcat/S0.5 for ATP was near ~600-fold higher that other nucleotides, whereas in the absence of activator was only ~3-fold higher. We propose that the allosteric regulation of certain enzymes is an evolutionary mechanism of adaptation for the selection of specific substrates.Fil: Ebrecht, Ana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentina. University of Chicago; Estados UnidosFil: Solamen, Ligin. University of Chicago; Estados UnidosFil: Hill, Benjamin L.. University of Chicago; Estados UnidosFil: Iglesias, Alberto Alvaro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Olsen, Kenneth W.. University of Chicago; Estados UnidosFil: Ballicora, Miguel A.. University of Chicago; Estados Unido

EL SECRETO DE LOS ÁRBOLES: El intercambio de información, nutrientes y agua entre las plantas a través del suelo: la red fúngica bajo tierra.

En los bosques andino-patagónicos de Argentina es común encontrar micorrizas en especies vegetales nativas. Pero ¿qué implicancias tiene la presencia de esta asociación para el ecosistema forestal patagónico? Este artículo propone recapitular los saberes en torno a las simbiosis entre microorganismos y plantas de la Patagonia, y difundir su conocimiento. ARK: ark:/s26185385/grazwvak

CHANGING NURSING CARE TIME AS AN EFFECT OF CHANGED CHARACTERISTICS OF THE DIALYSIS POPULATION

Background The population of dialysis patients is ageing. Dialysis nurses are confronted with geriatric patients with multiple comorbidities. Nurses are confronted with an increasing burden of care. Objectives The present study focused on the question of whether, over time, the increasing age and comorbidities of the haemodialysis population increased nursing care time. Furthermore, we studied potential changes in the predictors of the required nursing time. Design Observational study. Participants A total of 980 dialysis patients from 12 dialysis centres were included. Measurements Nurses filled out the classification tool for each patient and completed a form for reporting patient characteristics for groups of relevant haemodialysis patients at baseline and after 1 and four years. Changes in patient and dialysis characteristics were analysed, as well as the estimated nursing care time needed. Results An increase in the nursing time needed for dialysis was largely due to decreased mobility, closing of the vascular access and a greater need for psychosocial attention and was most strongly present in incident dialysis patients. The time needed for dialysis decreased as patient participation increased and vascular access changed from catheters to fistulae. Over the four-year period, the average overall needed nursing care time per haemodialysis session did not change. Conclusions Our study shows that the average nursing time needed per patient did not change in the four-year observation period. However, more time is required for incident patients; thus, if a centre has high patient turnover, more nursing care time is needed.</p

Daily life stress and the cortisol awakening response : testing the anticipation hypothesis

Acknowledgments We thank Paul Stewart for his contribution to data collection and Dr Matthew Jones for programming the handheld computers. Author Contributions Conceived and designed the experiments: WS DJP. Performed the experiments: DJP. Analyzed the data: WS. Wrote the paper: WS DJP.Peer reviewedPublisher PD

Спосіб захисту графіту від окислення

Спосіб захисту графіту від окислення шляхом насичення виробів, промивки в проточній воді, сушіння та термообробки в захисному середовищі ендогазу при температурі 1050-1150°С, який відрізняється тим, що насичення графітових виробів проводять в золі із гідролізованого з каталізатором НNО₃ етилсилікату, розбавленого водою в співвідношенні від 10:1 до 1:2, протягом 5-6 годин при температурі 4-10°С, сушіння проводять при температурі 40-65°C, а термообробку здійснюють за режимом: підйом температури від 20 до 900°С зі швидкістю 25-30град/хв, від 900°C до максимальної температури термообробки 10-15 град/хв, витримують при максимальній температурі 1050-1150°С 20-25хв, охолодження проводять до 350°С зі швидкістю 40-50град/хв

Cortisol in hair measured in young adults - a biomarker of major life stressors?

<p>Abstract</p> <p>Background</p> <p>Stress as a cause of illness has been firmly established. In public health and stress research a retrospective biomarker of extended stress would be an indispensible aid. The objective of this pilot study was to investigate whether concentrations of cortisol in hair correlate with perceived stress, experiences of serious life events, and perceived health in young adults.</p> <p>Methods</p> <p>Hair samples were cut from the posterior vertex area of (n = 99) university students who also answered a questionnaire covering experiences of serious life events, perceived Stress Scale and perceived health during the last three months. Cortisol was measured using a competitive radioimmunoassay in methanol extracts of hair samples frozen in liquid nitrogen and mechanically pulverised.</p> <p>Results</p> <p>Mean cortisol levels were significantly related to serious life events (p = 0.045), weakly negatively correlated to perceived stress (p = 0.025, r = -0.061) but nor affected by sex, coloured/permed hair, intake of pharmaceuticals or self-reported health. In a multiple regression model, only the indicator of serious life events had an independent (p = 0.041) explanation of increased levels of cortisol in hair. Out of four outliers with extremely high cortisol levels two could be contacted, both reported serious psychological problems.</p> <p>Conclusions</p> <p>These findings suggest that measurement of cortisol in hair could serve as a retrospective biomarker of increased cortisol production reflecting exposure to major life stressors and possibly extended psychological illness with important implications for research, clinical practice and public health. Experience of serious life events seems to be more important in raising cortisol levels in hair than perceived stress.</p

Impact of glucocorticoid receptor density on ligand-independent dimerization, cooperative ligand-binding and basal priming of transactivation: a cell culture model

Glucocorticoid receptor (GR) levels vary between tissues and individuals and are altered by physiological and pharmacological effectors. However, the effects and implications of differences in GR concentration have not been fully elucidated. Using three statistically different GR concentrations in transiently transfected COS-1 cells, we demonstrate, using co-immunoprecipitation (CoIP) and fluorescent resonance energy transfer (FRET), that high levels of wild type GR (wtGR), but not of dimerization deficient GR (GRdim), display ligand-independent dimerization. Whole-cell saturation ligand-binding experiments furthermore establish that positive cooperative ligand-binding, with a concomitant increased ligand-binding affinity, is facilitated by ligand-independent dimerization at high concentrations of wtGR, but not GRdim. The down-stream consequences of ligand-independent dimerization at high concentrations of wtGR, but not GRdim, are shown to include basal priming of the system as witnessed by ligand-independent transactivation of both a GRE-containing promoter-reporter and the endogenous glucocorticoid (GC)-responsive gene, GILZ, as well as ligand-independent loading of GR onto the GILZ promoter. Pursuant to the basal priming of the system, addition of ligand results in a significantly greater modulation of transactivation potency than would be expected solely from the increase in ligand-binding affinity. Thus ligand-independent dimerization of the GR at high concentrations primes the system, through ligand-independent DNA loading and transactivation, which together with positive cooperative ligand-binding increases the potency of GR agonists and shifts the bio-character of partial GR agonists. Clearly GR-levels are a major factor in determining the sensitivity to GCs and a critical factor regulating transcriptional programs

Model Model-based Testing based on xUML.

Die Unified Modelling Language (UML) wird zunehmend für die grafische Beschreibung bzw. Modellierung von Systemen verwendet. Für die Ausführung von UML-Modellen und den Test von Systemen ist eine formale Variante der UML, die executable UML (xUML) erschaffen worden. Am Beispiel von Generis, einem universellen Stellwerkmodells, dass im Euro-Interlocking Projekt erstellt wurde, wird die System-Modellierung mit xUML und der xUML basierte Testprozess beschrieben