\u3cem\u3eIn Vitro\u3c/em\u3e Determination of Potency of Small Molecule Inhibitors of Arp2/3 Complex

Actin is a key protein building block of actin microfilaments, which are constructed and deconstructed in response to cellular signaling pathways to regulate cellular processes such as motility, division, and endocytosis. Arp2/3 Complex is a 7-subunit protein complex that is in involved in cellular construction of branched actin networks, functioning by attaching to the side of a pre-existing actin filament and nucleating a daughter branch. Overexpression of Arp2/3 complex has been linked to the ability of certain metastatic cancers to proliferate. This work describes the synthesis and in vitro biochemical testing of several molecules predicted by computational docking to be inhibitors of Arp2/3 Complex, and therefore of potential interest in clinical applications. A bulk actin polymerization assay is used as the key method to determine the potency of inhibitor candidates. Structure-activity relationships derived from these results are also discussed

Concept definition study for recovery of tumbling satellites. Volume 1: Executive summary, study results

The first assessment is made of the design requirements and conceptual definition of a front end kit to be transported on the currently defined Orbital Maneuvering Vehicle (OMV) and the Space Transportation System Shuttle Orbiter, to conduct remote, teleoperated recovery of disabled and noncontrollable, tumbling satellites. Previous studies did not quantify the dynamic characteristics of a tumbling satellite, nor did they appear to address the full spectrum of Tumbling Satellite Recovery systems requirements. Both of these aspects are investigated with useful results

Concept definition study for recovery of tumbling satellites. Volume 2: Supporting research and technology report

A number of areas of research and laboratory experiments were identified which could lead to development of a cost efficient remote, disable satellite recovery system. Estimates were planned of disabled satellite motion. A concept is defined as a Tumbling Satellite Recovery kit which includes a modular system, composed of a number of subsystem mechanisms that can be readily integrated into varying combinations. This would enable the user to quickly configure a tailored remote, disabled satellite recovery kit to meet a broad spectrum of potential scenarios. The capability was determined of U.S. Earth based satellite tracking facilities to adequately determine the orientation and motion rates of disabled satellites

Changes in Land Distribution of Polar Bears in Western Hudson Bay

We examined the capture locations of polar bears (Ursus maritimus) on land in western Hudson Bay over 19 years (1986–2004) to assess temporal trends in the distribution of the population. We found that the distribution of bears of most age and sex groups shifted northward and eastward over the study. The causes of these shifts may be related to an altered population structure, changing environmental conditions, or a combination of both factors. Segregation by age, sex, and reproductive status persisted over time as found in earlier studies, but more females with young were within 5 km of the coast after 2001 than before. The distribution changes were correlated with the timing of sea-ice breakup, which now occurs, on average, about three weeks earlier than it did 30 years ago. While environmental conditions may have influenced polar bear distribution, the reduction in the number of large adult males along the coast may also have affected distribution patterns, allowing adult females to remain closer to the coast in more recent times.Nous avons examiné les lieux de capture d’ours polaires (Ursus maritimus) sur la terre ferme dans l’ouest de la baie d’Hudson pendant 19 ans (de 1986 à 2004) afin d’évaluer les tendances temporelles caractérisant la répartition de la population. Nous avons remarqué que la répartition des ours de la plupart des groupes d’âge et de sexe se déplaçait vers le nord et vers l’est au cours de l’étude. Cela pourrait être attribuable à une structure de population modifiée, à l’évolution des conditions environnementales ou à un ensemble des deux facteurs. La ségrégation en fonction de l’âge, du sexe et de l’état reproducteur a persisté avec le temps, tel que dénoté dans le cadre d’études antérieures, mais plus de femelles avec des jeunes se trouvaient en-dedans de cinq kilomètres de la côte après 2001 qu’avant. Les changements en matière de répartition ont été corrélés au moment de la débâcle de la glace de mer qui maintenant se produit, en moyenne, environ trois semaines plus tôt qu’il y a 30 ans. Bien que les conditions environnementales puissent avoir exercé une influence sur la répartition des ours polaires, la réduction du nombre de gros mâles adultes le long de la côte pourrait également avoir modifié les tendances caractérisant la répartition, permettant ainsi aux femelles adultes de rester plus près de la côte ces dernières années

A 140 GHz pulsed EPR/212 MHz NMR spectrometer for DNP studies

We described a versatile spectrometer designed for the study of dynamic nuclear polarization (DNP) at low temperatures and high fields. The instrument functions both as an NMR spectrometer operating at 212 MHz ([superscript 1]H frequency) with DNP capabilities, and as a pulsed-EPR operating at 140 GHz. A coiled TE[subscript 011] resonator acts as both an NMR coil and microwave resonator, and a double balanced ([superscript 1]H, [superscript 13]C) radio frequency circuit greatly stabilizes the NMR performance. A new 140 GHz microwave bridge has also been developed, which utilizes a four-phase network and ELDOR channel at 8.75 GHz, that is then multiplied and mixed to obtain 140 GHz microwave pulses with an output power of 120 mW. Nutation frequencies obtained are as follows: 6 MHz on S = 1/2 electron spins, 100 kHz on [superscript 1]H, and 50 kHz on [superscript 13]C. We demonstrate basic EPR, ELDOR, ENDOR, and DNP experiments here. Our solid effect DNP results demonstrate an enhancement of 144 and sensitivity gain of 310 using OX063 trityl at 80 K and an enhancement of 157 and maximum sensitivity gain of 234 using Gd-DOTA at 20 K, which is significantly better performance than previously reported at high fields (⩾3 T).National Institutes of Health (U.S.) (EB002804)National Institutes of Health (U.S.) (EB002026)National Institutes of Health (U.S.) (EB001965)National Institutes of Health (U.S.) (EB004866)Deutsche Forschungsgemeinschaft (Postdoctoral Fellowship

Polar bear (Ursus maritimus) Migration from Maternal Dens in Western Hudson Bay

Migration is a common life history strategy among Arctic vertebrates, yet some of its aspects remain poorly described for some species. In February-March, post-parturient polar bears (Ursus maritimus) in western Hudson Bay, Canada, migrate from maternity den sites on land to the sea ice with three- to four-month-old cubs. We investigated this migration using data from 10 adult females fitted with satellite-linked global positioning system collars tracked in 2011 – 16. Directed movement towards the coast began on average on 1 March (range: 31 January to 23 March) and took a mean of 7.8 days to reach the coast. Bears traveled 18 to 100 km from their dens to the coast (mean = 63 km) at a mean rate of 6.7 km/d. Movements were highly directed, with an approximate northeast orientation, but did not follow the shortest path to the coast. Observed migration patterns were broadly similar to those previously documented, although mean departure date from dens was about four days earlier and mean movement rate was only 40% of that from the late 1990s. Given the sensitivity of polar bears to climate change, the phenology of denning may be a meaningful parameter for long-term monitoring.Parmi les vertébrés de l’Arctique, la migration constitue une stratégie de cycle biologique courante et pourtant, pour certaines espèces, certains des aspects de la migration sont toujours mal décrits. En février et en mars, les ours polaires (Ursus maritimus) de post-parturition de l’ouest de la baie d’Hudson, au Canada, migrent depuis leurs aires terrestres de mise bas vers la glace de mer avec leurs oursons de trois à quatre mois. Nous avons étudié cette migration en nous servant des données relatives à dix femelles adultes dotées de colliers satellitaires avec système de localisation GPS, données recueillies de 2011 à 2016. En moyenne, les déplacements dirigés vers la côte commençaient le 1er mars (étendue : du 31 janvier au23 mars) et pour se rendre jusqu’à la côte, il fallait en moyenne 7,8 jours. De leur aire de mise bas jusqu’à la côte, les ours parcouraient de 18 à 100 km (moyenne = 63 km) au taux moyen de 6,7 km/j. Les déplacements étaient fortement dirigés, avec une orientation approximative du nord-est, sans toutefois emprunter le chemin le plus court menant à la côte. Les modèles de migration observés ressemblaient beaucoup aux modèles déjà documentés, quoique la date de départ moyenne des aires de mise bas s’établissait à environ quatre jours plus tôt et que le taux de déplacement moyen ne correspondait qu’à 40 % du taux de la fin des années 1990. Compte tenu de la sensibilité des ours polaires au changement climatique, la phénologie de l’aire de mise bas pourrait constituer un paramètre significatif pour la surveillance à long terme

Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization

We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here—which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole—circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100 K which shows 30 Hz linewidths.National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-002804)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-001960)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-001035)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-002026)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-003151)National Science Foundation (U.S.). Graduate Research Fellowship Progra