Asparaginyl-tRNA synthetase from the Escherichia coli temperature-sensitive strain HO202 A proline replacement in motif 2 is responsible for a large increase in Km for asparagine and ATP

AbstractThe Escherichia coli K12 mutant gene, asnS40, coding for asparaginyl-tRNA synthetase (AsnRS) in the temperature-sensitive strain HO202, was isolated from genomic DNA using the Polymerase Chain Reaction. DNA sequencing revealed that the mutant enzyme differs from the wild-type AsnRS by two amino acids, but only the P231L replacement leads to a change in aminoacylation activity. In the ATP-PPi exchange reaction at 37°C the purified P231L enzyme has a more than 50-fold increased Km value for asparagine compared to the wild-type enzyme, while the Km value for ATP is increased 8-fold. In the aminoacylation reaction the mutant enzyme shows also significantly increased Km values for asparagine and ATP. Interestingly Pro-231 is part of the conserved motif 2 in class II aminoacyl-tRNA synthetases (Eriani, G., Delarue, M., Poch, O., Gangloff, J. and Moras, D. (1990) Nature 347, 203–206), indicating that this motif might be involved in all class II enzymes in amino acid activation

Etude de mécanismes moléculaires de l’évolution

Les travaux initiaux du laboratoire étaient orientés vers la description des mécanismes de l’adaptation de protéines isolées des Archaea halophiles. En analysant un grand nombre de données biochimiques, structurales au regard du concept de l’évolution, j’ai pu établir l’existence d’une nouvelle famille enzymatique : les LDH-like Malate Déshydrogénase dont je suis devenu un référent :(http://www.ncbi.nlm.nih.gov/Structure/cdd/cddsrv.cgi?uid=cd01339).Toutes ces données ont été croisées à une étude phylogénétique qui m’a permis de décrire l’histoire évolutive de la super famille des malates (MalDH) et des lactates déshydrogénases (LDH). Cette famille est désormais considérée comme un vivier extrêmement riche pour trouver de nombreuses enzymes présentant des caractéristiques spécifiques d’adaptation à diverses contraintes physico-chimiques. Le dossier permet de voir que la combinaison de diverses méthodologies appliquées à l’étude de différentes enzymes (MalDH et LDH) permet de décortiquer en grands détails les mécanismes de l’adaptation. Les résultats obtenus font que cette famille enzymatique est une de celles qui est actuellement la mieux comprise en terme de relation repliement-structure-fonction-dynamique et évolution.Dans une deuxième partie, j’exposerai brièvement, comment ma réflexion a permis d’aller vers la caractérisation d’une nouvelle famille de déshydrogénase qui présente un nouveau motif de repliement, différent des déshydrogénases connues jusqu’à présent. Je montrerai aussi qu’il est vraisemblablement possible d’aller sonder les propriétés structurales d’une protéine ayant échappé au contrôle du repliemen

Correlations between stacked structures and weak itinerant magnetic properties of La2−x_{2-x} Yx_x Ni7_7 compounds

Hexagonal La$_2$Ni$_7$ and rhombohedral Y$_2$Ni$_7$ are weak itinerant antiferromagnet (wAFM) and ferromagnet (wFM), respectively. The crystal structure and magnetic properties of $A_2B_7$ intermetallic compounds ($A$ = La, Y, $B$ = Ni) have been investigated combining X-ray powder diffraction and magnetic measurements. The La$_{2-x}$Y$_x$Ni$_7$ intermetallic compounds with $0 \leq x \leq 1$ crystallize in the Ce$_{2}$Ni$_7$-type hexagonal structure with Y preferentially located in the [$AB_2$] units. The compounds with larger Y content ($1.2 \leq x < 2$) crystallize in both hexagonal and rhombohedral (Gd$_2$Co$_7$-type) structures with a progressive substitution of Y for La in the $A$ sites belonging to the [$AB_5$] units. Y$_2$Ni$_7$ crystallizes in the rhombohedral structure only. The average cell volume decreases linearly versus Y content, whereas the c/a ratio presents a minimum at $x = 1$ due to geometric constrains. The magnetic properties are strongly dependent on the structure type and the Y content. La$_{2}$Ni$_7$ displays a complex metamagnetic behavior with split AFM peaks. Compounds with x = 0.25 and 0.5 display a wAFM ground state and two metamagnetic transitions, the first one towards an intermediate wAFM state and the second one towards a FM state.T$_N$ and the second critical field increase with the Y content, indicating a stabilization of the AFM state. LaYNi$_7$, which is as the boundary between the two structure types, presents a very wFM state at low field and an AFM state as the applied field increases. All the compounds with $x > 1$ and containing a rhombohedral phase are wFM with $T_C$ = 53(2) K. In addition to the experimental studies, first principles calculations using spin polarization have been performed to interpret the evolution of both structural phase stability and magnetic ordering for $0 \leq x < 2$.Comment: 26 pages (7 for supplementary material), 4 tables, 9 main figures and 8 figures in supplementary materia

Thiosugars: reactivity, methodology and applications

Carbohydrates, alongside proteins and nucleic acids, constitute a crucial and versatile family of biomolecules present in all life forms. They manifest as monosaccharides, oligosaccharides, and polysaccharides, covalently bonded to proteins and fats. Carbohydrates are integral to plant and arthropod cell walls and traditionally viewed as the primary source and storage of energy, but also play a vital role in many fundamental biological processes. To study the structure and biological activity of specific carbohydrates, it is essential to synthesize them in a pure and well-defined form, as current natural extraction techniques are often limiting.The work of this thesis is focused on a specific type of glycomimetics: thiosugars, i.e. sugar analogues which have their endocylic oxygen replaced by a sulfur atom. These analogues are of interest because of their unique stability and stereoelectronic effects, which closely mimick their natural O-counterparts. The glycosidic linkage of thioglycosides (i.e. 4-S-furanosides and 5-S-pyranosides) shows improved resistance towards chemical and enzymatic hydrolysis.Bio-organic Synthesi

La désirabilité sociale a-t-elle un effet sur la motivation au changement des personnes en cours de sentence?

Rapport de stage présenté à la Faculté des Arts et des Sciences en vue de l'obtention du grade de Maîtrise (M.Sc.) en criminologieTrès peu de chercheurs ont porté attention aux liens possibles entre la motivation au changement et la désirabilité sociale. Cependant, dans un système de contrôle comme la probation, où la personne détenue peut avoir le sentiment que son sort dépend de l’intervenant qui la suit, la motivation au changement pourrait être influencée par le désir de bien paraître aux yeux de cet intervenant. Afin d’examiner la présence ou non d’indices de désirabilité sociale dans un contexte de probation, un stage à la Direction des services professionnels correctionnels de Joliette a été réalisé. Au cours de ce stage, des entretiens auprès de quatre participants ont été effectués et deux questionnaires, l’University of Rhode Island Change Assessment Scale et l’échelle de désirabilité sociale de Strahan et Gerbasi (1972) leur ont été administrées. Ces participants purgeaient une sentence dans la communauté. L’analyse du matériel recueilli a permis de noter la présence de liens entre la désirabilité sociale et la motivation au changement chez deux des quatre participants à l’étude. À cet égard, l’évaluation de ces deux aspects pourrait contribuer à aider les agents de probation à identifier les dimensions à travailler pour soutenir la motivation au changement de leurs clients et pour mieux identifier les personnes les plus susceptibles de profiter de l’aide offerte.Few studies have examined the relationship between motivation for change and social desirability. In certain social control situations such as probation, individuals’ motivation for change might be influenced by a wish to please the probation officer. Hence motivation for change might be influenced by social desirability. An internship completed at the Direction des services professionnels correctionnels of Joliette allowed the author to examine the presence, or absence, of social desirability in the context of probation. During the course of the internship interviews were completed with four participants in the programme who were also administered two questionnaires, the University of Rhode Island Change Assessment Scale, and Strahan and Gerbasi’s (1972) social desirability scale. Analysis showed a relationship between social desirability and motivation for change in two participants of the four participants of the study. Evaluation of these aspects might help probation officers identify the dimensions to work on in order to support motivation for change in clients and to better identify those who might benefit the most of the help offered

Op weg naar een schuldenvrij leven. Gezond financieel gedrag noodzakelijk om financiele problemen te voorkomen

De schuldenproblematiek in Nederland is nog steeds groeiende. De impact op de schuldenaar, maar ook op de samenleving, is groot. Financiële problemen zijn voor een groot deel een gedragsvraagstuk. In deze dissertatie staat het gedrag van de groep consumenten met een financiële achterstand centraal. Uit de analyses blijkt dat het niet één specifieke gedraging is die leidt tot financiële problemen, maar een combinatie van verschillende gedragingen die het risico op financiële problemen vergroten. Zo spelen niet bijhouden van de administratie, post en niet vooruit plannen een rol. Analyses naar de oorzaken van deze gedragingen laten bovendien zien dat er verschillende factoren en processen zijn die samenhang vertonen met het financiële gedrag. Onder meer de rol van self-efficacy, self-control en sociale steun, is onderzocht en blijken een samenhang te hebben. Financiële problemen kennen een eigen dynamiek. Eenmaal geconfronteerd met financiële problemen, verandert het gedrag van de consument. Deze verandering wordt deels veroorzaakt, doordat hij zich moet aanpassen en bijvoorbeeld meer gaat bezuinigen. Maar de verandering van gedrag is ook het gevolg van processen zoals schaarste en een veranderende houding ten opzichte van schulden.Coherent privaatrech

Digging for data: the rise and fall of a Miocene mammal biodiversity hotspot in the Vallès-Penedès (Catalonia, Spain)

The Vallesian, 11.1-9 Ma, was a special time in the Vallès-Penedes basin near Barcelona, where a biodiversity hotspot existed. Europe had a subtropical climate, with rhinos, forest giraffes, lions, hyenas, flying squirrels and primates.Around 9.7 million years ago there was an abrupt collapse in diversity; the so-called 'Vallesian Crisis'. This was seen as the transition point to a climate with more seasonality and open landscapes.Using a fossil dataset from Miocene Eurasia, the influence of dataset quality on the severity of this crisis, which animals were most affected and their distribution patterns was studied.The crisis’ victims have three things in common: they are mainly forest dwellers, they date back to the Middle Miocene (16-11.1 Ma), and they are rare during the early Vallesian. The high Vallesian biodiversity was caused by the arrival of new immigrants in addition to older transient groups, possibly due to the unique coastal conditions.Major differences existed between the coastal region and the interior of the Iberian Peninsula. Some species appeared in the Vallès-Penedès, but never reached the inland. The 'Vallesian Crisis', while seen understandably as a time of abrupt and severe extinction, was thus largely a local turnover event.Naturali

Tunneling, cognitive load and time orientation and their relations with dietary behavior of people experiencing financial scarcity – an AI-assisted scoping review elaborating on scarcity theory

Background: The concept of a financial scarcity mindset has raised much attention as an explanation for poor decision-making and dysfunctional behavior. It has been suggested that financial scarcity could also impair dietary behavior, through a decline in self-control. Underlying cognitive mechanisms of tunneling (directing attention to financial issues and neglecting other demands), cognitive load (a tax on mental bandwidth interfering with executive functioning) and time orientation (a shift towards a present time horizon, versus a future time horizon) may explain the association between financial scarcity and self-control related dietary behavior. The current scoping review gathers recent evidence on how these mechanisms affect dietary behavior of people experiencing financial scarcity. It builds on a theoretical framework based on insights from behavioral economics and health psychology. Methods: A literature search was executed in six online databases, which resulted in 9.975 papers. Search terms were tunneling, cognitive load and time orientation, financial scarcity, and dietary behavior. Screening was performed with ASReview, an AI-ranking tool. In total, 14 papers were included in the scoping review. We used PRISMA-ScR guidelines for reporting. Results: Limited evidence indicates that a scarcity mindset could increase tunneling, through attentional narrowing on costs of food, which then directly impacts dietary behavior. A scarcity mindset involves experiencing financial stress, which can be understood as cognitive load. Cognitive load decreases attentional capacity, which could impair self-control in dietary choices. Financial scarcity is related to a present time orientation, which affects dietary choices by shifting priorities and decreasing motivation for healthy dietary behavior. Conclusions: A scarcity mindset affects dietary behavior in different ways. Tunneling and a shift in time orientation are indicative of an attentional redirection, which can be seen as more adaptive to the situation. These may be processes indirectly affecting self-control capacity. Cognitive load could decrease self-control capacity needed for healthy dietary behavior because it consumes mental bandwidth. How a changing time orientation when experiencing financial scarcity relates to motivation for self-control in dietary behavior is a promising theme for further inquiry.</p

Tunneling, cognitive load and time orientation and their relations with dietary behavior of people experiencing financial scarcity – an AI-assisted scoping review elaborating on scarcity theory

Background: The concept of a financial scarcity mindset has raised much attention as an explanation for poor decision-making and dysfunctional behavior. It has been suggested that financial scarcity could also impair dietary behavior, through a decline in self-control. Underlying cognitive mechanisms of tunneling (directing attention to financial issues and neglecting other demands), cognitive load (a tax on mental bandwidth interfering with executive functioning) and time orientation (a shift towards a present time horizon, versus a future time horizon) may explain the association between financial scarcity and self-control related dietary behavior. The current scoping review gathers recent evidence on how these mechanisms affect dietary behavior of people experiencing financial scarcity. It builds on a theoretical framework based on insights from behavioral economics and health psychology. Methods: A literature search was executed in six online databases, which resulted in 9.975 papers. Search terms were tunneling, cognitive load and time orientation, financial scarcity, and dietary behavior. Screening was performed with ASReview, an AI-ranking tool. In total, 14 papers were included in the scoping review. We used PRISMA-ScR guidelines for reporting. Results: Limited evidence indicates that a scarcity mindset could increase tunneling, through attentional narrowing on costs of food, which then directly impacts dietary behavior. A scarcity mindset involves experiencing financial stress, which can be understood as cognitive load. Cognitive load decreases attentional capacity, which could impair self-control in dietary choices. Financial scarcity is related to a present time orientation, which affects dietary choices by shifting priorities and decreasing motivation for healthy dietary behavior. Conclusions: A scarcity mindset affects dietary behavior in different ways. Tunneling and a shift in time orientation are indicative of an attentional redirection, which can be seen as more adaptive to the situation. These may be processes indirectly affecting self-control capacity. Cognitive load could decrease self-control capacity needed for healthy dietary behavior because it consumes mental bandwidth. How a changing time orientation when experiencing financial scarcity relates to motivation for self-control in dietary behavior is a promising theme for further inquiry.</p

Haemangioma of Infancy: Two Case Reports with an Overdose of Propranolol

An 8-week-old infant was treated with oral propranolol for a haemangioma of infancy. The standard dose (according to protocol) is 2 mg/kg/day but, because of a mistake by the pharmacist, the child was treated with 8 mg/kg/day without any side effects (pulse, blood pressure and glucose stayed normal)