N-terminal acetylation of ectopic recombinant proteins in Escherichia coli

AbstractN-terminal acetylation is a protein modification common in eukaryotes, but rare in prokaryotes. Here, we characterized five mammalian stathmin-like subdomains expressed in Escherichia coli by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nanoESI Q-TOF tandem mass spectrometry. We revealed that RB3SLD and RB3′SLD are Nα-acetylated, whereas SCG10SLD and SCLIPSLD, although identical up to residue 6, are not, as well as stathmin. To assess the influence of the N-terminal sequences on Nα-acetylation, we exchanged residues 7 and 8 between acetylated RB3SLD and unacetylated SCG10SLD, and showed that it reversed the acetylation pattern. Our results demonstrate that ectopic recombinant proteins can be extensively Nα-acetylated in E. coli, and that the rules governing Nα-acetylation are complex and involve the N-terminal region, as in eukaryotes

Robust och smidig attitydreglering för nanosatelliten Eye-Sat

Eye-Sat is a student-designed 3U-CubeSat, to be launched to a sun-synchronous orbit from where it will map the zodiacal light, a faint glare caused by the reflection of Sun on interplanetary dust. Such mission requires an accurate 3-axis attitude control, for which Eye-Sat is equipped with reactions wheels, magnetorquers, magnetometers and a star tracker. The star tracker can only be used for inertial pointing, which confines its use to shooting phases. A solution based on the remaining 3 equipment is proposed for the other mission phases, providing 3-axis pointing with high agility, for ground station tracking, at the cost of a slightly degraded accuracy. The magnetometers and magnetorquers work in closed-loop, while manoeuvres are performed in open-loop by the reaction wheels, which also ensure gyroscopic stabilisation of the spacecraft. Since this design relies on only one sensor, efforts have been put into making it robust to the imperfections of the magnetometers. Robustness to potential changes in the mission or the design has also been taken into consideration. Performance assessments carried out on a preliminary tuning have demonstrated the capacity of this magnetic-based mode to recover 3-axis pointing when exiting the survival mode, to provide a 3-axis pointing accuracy better than 8 deg  in the worst case, and to sustain slews up to 0.87 deg/s in download.Eye-Sat är en 3U-CubeSat utformad och byggd av studenter. Den ska placeras i en solsynkron omloppsbana där den kommer att kartlägga zodiakljuset, en svag bländning producerad när solens ljus reflekterar på interplanetärt damm. Detta rymduppdrag kräver en precis reglering kring tre axlar och därför är Eye-Sat utrustad med fyra reaktionshjul, magnetspolar för kraftmomentgenerering, magnetometrar och en stjärnsensor. Stjärnsensorn kan endast användas för inertial attitydreglering, vilket begränsar användningen till fotograferingsfaser. En strategi baserad på de återstående regleringsdonen och sensorerna föreslås för de andra rymduppdragsfaserna, vilken ger treaxlig pekning för markstationsspårning, men med något sämre noggrannhet. Magnetometrarna och magnetspolarna arbetar i sluten reglering, medan manövreringen genomförs i öppen reglering med reaktionshjulen, vilka också säkerställer gyroskopisk stabilisering av rymdfarkosten. Eftersom denna utformning är beroende av endast en sensor är det kritiskt att göra den robust mot mätfel hos magnetometern. Robusthet mot potentiella framtida förändringar i utformningen har också beaktats. Prestandabedömningar som gjorts vid en preliminär inställning har demonstrerat att den magnetiska regleringen kan återställa treaxlig pekning när man lämnar den säkra regleringmoden. En treaxlig pekningsnoggrannhet bättre än 8 grader i värsta fall och vinkelhastigheter upp till 0.87 grader/s i nedladdningsfaser

Robust och smidig attitydreglering för nanosatelliten Eye-Sat

Eye-Sat is a student-designed 3U-CubeSat, to be launched to a sun-synchronous orbit from where it will map the zodiacal light, a faint glare caused by the reflection of Sun on interplanetary dust. Such mission requires an accurate 3-axis attitude control, for which Eye-Sat is equipped with reactions wheels, magnetorquers, magnetometers and a star tracker. The star tracker can only be used for inertial pointing, which confines its use to shooting phases. A solution based on the remaining 3 equipment is proposed for the other mission phases, providing 3-axis pointing with high agility, for ground station tracking, at the cost of a slightly degraded accuracy. The magnetometers and magnetorquers work in closed-loop, while manoeuvres are performed in open-loop by the reaction wheels, which also ensure gyroscopic stabilisation of the spacecraft. Since this design relies on only one sensor, efforts have been put into making it robust to the imperfections of the magnetometers. Robustness to potential changes in the mission or the design has also been taken into consideration. Performance assessments carried out on a preliminary tuning have demonstrated the capacity of this magnetic-based mode to recover 3-axis pointing when exiting the survival mode, to provide a 3-axis pointing accuracy better than 8 deg  in the worst case, and to sustain slews up to 0.87 deg/s in download.Eye-Sat är en 3U-CubeSat utformad och byggd av studenter. Den ska placeras i en solsynkron omloppsbana där den kommer att kartlägga zodiakljuset, en svag bländning producerad när solens ljus reflekterar på interplanetärt damm. Detta rymduppdrag kräver en precis reglering kring tre axlar och därför är Eye-Sat utrustad med fyra reaktionshjul, magnetspolar för kraftmomentgenerering, magnetometrar och en stjärnsensor. Stjärnsensorn kan endast användas för inertial attitydreglering, vilket begränsar användningen till fotograferingsfaser. En strategi baserad på de återstående regleringsdonen och sensorerna föreslås för de andra rymduppdragsfaserna, vilken ger treaxlig pekning för markstationsspårning, men med något sämre noggrannhet. Magnetometrarna och magnetspolarna arbetar i sluten reglering, medan manövreringen genomförs i öppen reglering med reaktionshjulen, vilka också säkerställer gyroskopisk stabilisering av rymdfarkosten. Eftersom denna utformning är beroende av endast en sensor är det kritiskt att göra den robust mot mätfel hos magnetometern. Robusthet mot potentiella framtida förändringar i utformningen har också beaktats. Prestandabedömningar som gjorts vid en preliminär inställning har demonstrerat att den magnetiska regleringen kan återställa treaxlig pekning när man lämnar den säkra regleringmoden. En treaxlig pekningsnoggrannhet bättre än 8 grader i värsta fall och vinkelhastigheter upp till 0.87 grader/s i nedladdningsfaser

Parenté et diversité fonctionnelles des protéines de la famille de la stathmine

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Robust och smidig attitydreglering för nanosatelliten Eye-Sat

Eye-Sat is a student-designed 3U-CubeSat, to be launched to a sun-synchronous orbit from where it will map the zodiacal light, a faint glare caused by the reflection of Sun on interplanetary dust. Such mission requires an accurate 3-axis attitude control, for which Eye-Sat is equipped with reactions wheels, magnetorquers, magnetometers and a star tracker. The star tracker can only be used for inertial pointing, which confines its use to shooting phases. A solution based on the remaining 3 equipment is proposed for the other mission phases, providing 3-axis pointing with high agility, for ground station tracking, at the cost of a slightly degraded accuracy. The magnetometers and magnetorquers work in closed-loop, while manoeuvres are performed in open-loop by the reaction wheels, which also ensure gyroscopic stabilisation of the spacecraft. Since this design relies on only one sensor, efforts have been put into making it robust to the imperfections of the magnetometers. Robustness to potential changes in the mission or the design has also been taken into consideration. Performance assessments carried out on a preliminary tuning have demonstrated the capacity of this magnetic-based mode to recover 3-axis pointing when exiting the survival mode, to provide a 3-axis pointing accuracy better than 8 deg  in the worst case, and to sustain slews up to 0.87 deg/s in download.Eye-Sat är en 3U-CubeSat utformad och byggd av studenter. Den ska placeras i en solsynkron omloppsbana där den kommer att kartlägga zodiakljuset, en svag bländning producerad när solens ljus reflekterar på interplanetärt damm. Detta rymduppdrag kräver en precis reglering kring tre axlar och därför är Eye-Sat utrustad med fyra reaktionshjul, magnetspolar för kraftmomentgenerering, magnetometrar och en stjärnsensor. Stjärnsensorn kan endast användas för inertial attitydreglering, vilket begränsar användningen till fotograferingsfaser. En strategi baserad på de återstående regleringsdonen och sensorerna föreslås för de andra rymduppdragsfaserna, vilken ger treaxlig pekning för markstationsspårning, men med något sämre noggrannhet. Magnetometrarna och magnetspolarna arbetar i sluten reglering, medan manövreringen genomförs i öppen reglering med reaktionshjulen, vilka också säkerställer gyroskopisk stabilisering av rymdfarkosten. Eftersom denna utformning är beroende av endast en sensor är det kritiskt att göra den robust mot mätfel hos magnetometern. Robusthet mot potentiella framtida förändringar i utformningen har också beaktats. Prestandabedömningar som gjorts vid en preliminär inställning har demonstrerat att den magnetiska regleringen kan återställa treaxlig pekning när man lämnar den säkra regleringmoden. En treaxlig pekningsnoggrannhet bättre än 8 grader i värsta fall och vinkelhastigheter upp till 0.87 grader/s i nedladdningsfaser

Combined influence of pressurization and bendingof pre-hydrided unirradiated rod sectionsafter simulated transportation conditions

International audienceDuring the transportation of spent fuel assemblies, filling gas and fission gas release pressurize the fuel rods contained in the transportation cask. The rods are heated by their residual power, increasing the pressurization stresses and facilitating radial hydride precipitation during subsequent cooling. Radial hydrides have a detrimental influence on cladding ductility in some loading situations.In the present study, radial hydrides formed during simulated transportation are first evaluated, then their influence on pressurized fuel rod bending resistance is studied using a four point bend test device.The samples are pre-hydrogenated SRA Zircaloy-4 cladding tubes with alumina pellets inserted within the cladding tube. The samples are then tightened with Swagelocks and pressurized. The four point bend device is first used to precipitate radial hydrides using combined internal pressurization and bending imposed to the rod samples to simulate the fuel assembly transportation. The radial hydride precipitation heat treatment consists in heating the device at 350°C to dissolve hydrogen and cooling it slowly. After this, to simulate a lateral impact of fuel assemblies, the pressurized sample is loaded at room temperature under combined internal pressurization and four point bending. This type of loading induces a combination of axial and hoop stresses varying in the azimuthal direction between the two central rollers of the four point bending device. Internal pressurization and fuel pellets presence are shown to significantly strengthen the samples. Besides a rather negligible influence of radial hydrides on sample failure was observed under this loading configuration. After this mechanical test, the sample is cut and examined to check radial hydrides distribution at different azimuthal locations. These examination allows analyzing axial to hoop stress ratio influence on radial hydride precipitation but also to better understand the strengthening influence of fuel pellets and internal pressurization

Combined influence of pressurization and bendingof pre-hydrided unirradiated rod sectionsafter simulated transportation conditions

International audienceDuring the transportation of spent fuel assemblies, filling gas and fission gas release pressurize the fuel rods contained in the transportation cask. The rods are heated by their residual power, increasing the pressurization stresses and facilitating radial hydride precipitation during subsequent cooling. Radial hydrides have a detrimental influence on cladding ductility in some loading situations.In the present study, radial hydrides formed during simulated transportation are first evaluated, then their influence on pressurized fuel rod bending resistance is studied using a four point bend test device.The samples are pre-hydrogenated SRA Zircaloy-4 cladding tubes with alumina pellets inserted within the cladding tube. The samples are then tightened with Swagelocks and pressurized. The four point bend device is first used to precipitate radial hydrides using combined internal pressurization and bending imposed to the rod samples to simulate the fuel assembly transportation. The radial hydride precipitation heat treatment consists in heating the device at 350°C to dissolve hydrogen and cooling it slowly. After this, to simulate a lateral impact of fuel assemblies, the pressurized sample is loaded at room temperature under combined internal pressurization and four point bending. This type of loading induces a combination of axial and hoop stresses varying in the azimuthal direction between the two central rollers of the four point bending device. Internal pressurization and fuel pellets presence are shown to significantly strengthen the samples. Besides a rather negligible influence of radial hydrides on sample failure was observed under this loading configuration. After this mechanical test, the sample is cut and examined to check radial hydrides distribution at different azimuthal locations. These examination allows analyzing axial to hoop stress ratio influence on radial hydride precipitation but also to better understand the strengthening influence of fuel pellets and internal pressurization

Experimental Study of the Effect of Neighboring Rods in Fuel Cladding Deformation under LOCA Conditions

International audienceThe purpose of the COCAGNE experiments, performed in the framework of the PERFROI program, is to study the deformation and burst of fuel cladding under Loss-Of-Coolant-Accident (LOCA) conditions in “multi-rod” configuration. This configuration enables to study the deformation in situations of contact/blockage between peripheral rods, the burst conditions after contact, and the influence of azimuthal temperature gradient on cladding strains. The main objective is to get precise knowledge of the three-dimensional mechanical behavior of pressurized rods surrounded by structures simulating four neighboring fuel rods, under a geometrical and thermal representative environment. Experimental data will be used to validate three-dimensional thermal mechanical models implemented in the DRACCAR software (developed by IRSN for the simulation of LOCA type accidents) that can simulate rod and multi-rods behavior during LOCA transients.The COCAGNE facility can heat a rod cladding up to 1200°C under an internal pressure of up to 10 MPa. The rod can be surrounded by 4 “guards” that emulate peripheral deformed rods. To simulate as accurately as possible the major types of coolant conditions, such as guide tube presence for instance, the position, the temperature and the geometry of each guards are adjustable. The facility includes a mobile platform that moves several sensors along the vertical axis allowing the on-line measure of temperature and radial deformation of the cladding during the test. Several tests have been carried out on pre-oxidized Zy-4 (10 µm of pre-oxide) at different heating rates (1, 5 and 10 °C/s) and at pressures from 2 to 10 MPa. The effect of the temperature gaps between the test rod and the guards or between the guards were also studied. This paper is intended to introduce the COCAGNE facility, its performances and some typical results obtained