32 research outputs found
Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.
G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology
International Knowledge Flows and Economic Performance An Introductory Survey of the Evidence
Segmented flow generator for serial crystallography at the European X-ray free electron laser
Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported
The Science Performance of JWST as Characterized in Commissioning
This paper characterizes the actual science performance of the James Webb
Space Telescope (JWST), as determined from the six month commissioning period.
We summarize the performance of the spacecraft, telescope, science instruments,
and ground system, with an emphasis on differences from pre-launch
expectations. Commissioning has made clear that JWST is fully capable of
achieving the discoveries for which it was built. Moreover, almost across the
board, the science performance of JWST is better than expected; in most cases,
JWST will go deeper faster than expected. The telescope and instrument suite
have demonstrated the sensitivity, stability, image quality, and spectral range
that are necessary to transform our understanding of the cosmos through
observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures;
https://iopscience.iop.org/article/10.1088/1538-3873/acb29
Investigating Carbonaceous Aerosol and its Absorption Properties From Fires in the Western United States (WECAN) and Southern Africa (ORACLES and CLARIFY)
Towards Cities as Communities
Cities should be communities that ensure high quality of life promoting effective services, sustaining knowledge acquisition and developing innovation, using technology to sustain urban growth and promote value creation. Cities becoming smart communities should adopt a smart approach to driving social and economic urban development employing information technology to promote innovation. Information and communication technologies (ICTs) help cities to achieve successful issues as smart communities within knowledge-based global and local economies and open societies. Sustaining smart growth relies on rethinking the city as a smart and sustainable community using technology to support collaboration between local government, businesses, education and research centres and people to change the city in a significant and positive way. Sustainable, inclusive and open cities should evolve as communities that use technology to support human capital value, to use knowledge sources encouraging public and private organizations to believe in cooperation for sustaining change through innovation
Investigating Carbonaceous Aerosol and Its Absorption Properties From Fires in the Western United States (WE‐CAN) and Southern Africa (ORACLES and CLARIFY)
Biomass burning (BB) produces large quantities of carbonaceous aerosol (black carbon and organic aerosol, BC and OA, respectively), which significantly degrade air quality and impact climate. BC absorbs radiation, warming the atmosphere, while OA typically scatters radiation, leading to cooling. However, some OA, termed brown carbon (BrC), also absorbs visible and near UV radiation; although, its properties are not well constrained. We explore three aircraft campaigns from important BB regions with different dominant fuel and fire types (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen [WE-CAN] in the western United States and ObseRvations of Aerosols above CLouds and their intEractionS and Cloud-Aerosol-Radiation Interactions and Forcing for Year downwind of southern Africa) and compare them with simulations from the global chemical transport model, GEOS-Chem using GFED4s. The model generally captures the observed vertical profiles of carbonaceous BB aerosol concentrations; however, we find that BB BC emissions are underestimated in southern Africa. Our comparisons suggest that BC and/or BrC absorption is substantially higher downwind of Africa than in the western United States and, while the Saleh et al. (2014, https://doi.org/10.1038/ngeo2220) and FIREX parameterizations based on the BC:OA ratio improve model-observation agreement in some regions, they do not sufficiently differentiate absorption characteristics at short wavelengths. We find that photochemical whitening substantially decreases the burden and direct radiative effect of BrC (annual mean of +0.29 W m−2 without whitening and +0.08 W m−2 with). Our comparisons suggest that whitening is required to explain WE-CAN observations; however, the importance of whitening for African fires cannot be confirmed. Qualitative comparisons with the OMI UV aerosol index suggest our standard BrC whitening scheme may be too fast over Africa
Serial femtosecond X-ray diffraction of enveloped virus microcrystals
Serial femtosecond crystallography (SFX) using X-ray free-electron lasers has produced high-resolution, room temperature, time-resolved protein structures. We report preliminary SFX of Sindbis virus, an enveloped icosahedral RNA virus with ∼700 Å diameter. Microcrystals delivered in viscous agarose medium diffracted to ∼40 Å resolution. Small-angle diffuse X-ray scattering overlaid Bragg peaks and analysis suggests this results from molecular transforms of individual particles. Viral proteins undergo structural changes during entry and infection, which could, in principle, be studied with SFX. This is an important step toward determining room temperature structures from virus microcrystals that may enable time-resolved studies of enveloped viruses
Microfluidic sorting of protein nanocrystals by size for X-ray free-electron laser diffraction
The advent and application of the X-ray free-electron laser (XFEL) has uncovered the
structures of
proteins that
could not previously be solved using traditional crystallography. While this new
technology is powerful, optimization of the process is still needed to improve data
quality and analysis efficiency. One area is sample heterogeneity, where variations in
crystal size (among other factors) lead to the requirement of large data sets (and thus
10–100 mg of protein) for determining accurate structure factors. To decrease
sample dispersity, we developed a high-throughput microfluidic sorter operating on the
principle of dielectrophoresis, whereby polydisperse particles can be transported into
various fluid streams for size fractionation. Using this microsorter, we isolated several
milliliters of photosystem I nanocrystal fractions ranging from 200 to 600 nm in size as
characterized by dynamic light scattering, nanoparticle tracking, and electron microscopy.
Sorted nanocrystals were delivered in a liquid jet via the
gas dynamic virtual nozzle into the path of the XFEL at the Linac Coherent Light Source.
We obtained diffraction to ∼4 Å resolution, indicating that the small crystals were
not damaged by the sorting process. We also observed the shape transforms of photosystem I
nanocrystals,
demonstrating that our device can optimize data collection for the shape transform-based
phasing method. Using simulations, we show that narrow crystal size distributions can
significantly improve merged data quality in serial crystallography. From this
proof-of-concept work, we expect that the automated size-sorting of protein crystals will become an
important step for sample production by reducing the amount of protein needed for a high
quality final structure and the development of novel phasing methods that exploit
inter-Bragg reflection intensities or use variations in beam intensity for radiation
damage-induced phasing. This method will also permit an analysis of the dependence of
crystal quality on crystal size