The outer membrane of Gram-negative bacteria is highly impermeable to hydrophilic molecules of larger than 600 Da, protecting these bacteria from toxins present in the environment. In order to transport nutrients across this impermeable membrane, Gram-negative bacteria utilize a diverse family of outer-membrane proteins called TonB-dependent transporters. The majority of the members of this family transport iron-containing substrates. However, it is becoming increasingly clear that TonB-dependent transporters target chemically diverse substrates. In this work, the structure and phylogenetic distribution of the TonB-dependent transporter YncD are investigated. It is shown that while YncD is present in some enteropathogens, including Escherichia coli and Salmonella spp., it is also widespread in Gammaproteobacteria and Betaproteobacteria of environmental origin. The structure of YncD was determined, showing that despite a distant evolutionary relationship, it shares structural features with the ferric citrate transporter FecA, including a compact positively charged substrate-binding site. Despite these shared features, it is shown that YncD does not contribute to the growth of E. coli in pure culture under iron-limiting conditions or with ferric citrate as an iron source. Previous studies of transcriptional regulation in E. coli show that YncD is not induced under iron-limiting conditions and is unresponsive to the ferric uptake regulator (Fur). These observations, combined with the data presented here, suggest that YncD is not responsible for the transport of an iron-containing substrate.

“My recurring theme is the transformation of the ordinary…,” explains National Air and Space Museum photographer Carolyn Russo in reference to her new book, Art […]

The post Book: Airport Towers as Abstract Art appeared first on Smithsonian Insider.

Yung-An Huang, Chih-Hsuan Hsu, Ho-Chieh Chiu, Pei-Yu Hsi, Chris T. Ho, Wei-Lun Lo, and Eric Hwang

Microtubule (MT) is the most abundant cytoskeleton in neurons and controls multiple facets of their development. While the MT-organizing center (MTOC) in mitotic cells is typically located at the centrosome, MTOC in neurons switches to non-centrosomal sites. A handful of cellular components have been shown to promote non-centrosomal MT (ncMT) formation in neurons, yet the regulation mechanism remains unknown. Here we demonstrate that the small GTPase Ran is a key regulator of ncMTs in neurons. Using an optogenetic tool that enables light-induced local production of RanGTP, we demonstrate that RanGTP promotes ncMT plus-end growth along the neurite. Additionally, we discovered that actin waves drive the anterograde transport of RanGTP. Pharmacological disruption of actin waves abolishes the enrichment of RanGTP and reduces growing ncMT plus-ends at the neurite tip. These observations identify a novel regulation mechanism of ncMTs and pinpoint an indirect connection between the actin and MT cytoskeletons in neurons.

David Guerit, Pauline Marie, Anne Morel, Justine Maurin, Christel Verollet, Brigitte Raynaud-Messina, Serge Urbach, and Anne Blangy

Among hematopoietic cells, osteoclasts (Oc) and immature dendritic cells (Dc) are closely related myeloid cells with distinct functions; Oc participate skeleton maintenance while Dc sample the environment for foreign antigens. Such specificities rely on profound modifications of gene and protein expression during Oc and Dc differentiation. We provide global proteomic and transcriptomic analyses of primary mouse Oc and Dc, based on original SILAC and RNAseq data. We established specific signatures for Oc and Dc including genes and proteins of unknown functions. In particular, we showed that Oc and Dc have the same α and β tubulin isotypes repertoire but that Oc express much more β tubulin isotype Tubb6. In both mouse and human Oc, we demonstrate that elevated expression of Tubb6 in Oc is necessary for correct podosomes organization and thus for the structure of the sealing zone, which sustains the bone resorption apparatus. Hence, lowering Tubb6 expression hindered Oc resorption activity. Overall, we highlight here potential new regulators of Oc and Dc biology and illustrate the functional importance of the tubulin isotype repertoire in the biology of differentiated cells.

Björn Eismann, Teresa G. Krieger, Jürgen Beneke, Ruben Bulkescher, Lukas Adam, Holger Erfle, Carl Herrmann, Roland Eils, and Christian Conrad

3D cell cultures enable the in vitro study of dynamic biological processes such as the cell cycle, but their use in high-throughput screens remains impractical with conventional fluorescent microscopy. Here, we present a screening workflow for the automated evaluation of mitotic phenotypes in 3D cell cultures by light-sheet microscopy. After sample preparation by a liquid handling robot, cell spheroids are imaged for 24 hours in toto with a dual-view inverted selective plane illumination microscope (diSPIM) with a much improved signal-to-noise ratio, higher imaging speed, isotropic resolution and reduced light exposure compared to a spinning disc confocal microscope. A dedicated high-content image processing pipeline implements convolutional neural network based phenotype classification. We illustrate the potential of our approach by siRNA knock-down and epigenetic modification of 28 mitotic target genes for assessing their phenotypic role in mitosis. By rendering light-sheet microscopy operational for high-throughput screening applications, this workflow enables target gene characterization or drug candidate evaluation in tissue-like 3D cell culture models.

Aparna Sherlekar, Gayatri Mundhe, Prachi Richa, Bipasha Dey, Swati Sharma, and Richa Rikhy

Branched actin networks driven by Arp2/3 collaborate with actomyosin filaments in processes such as cell migration. The syncytial Drosophila blastoderm embryo also shows expansion of apical caps by Arp2/3 driven actin polymerization in interphase and buckling at contact edges by MyosinII to form furrows in metaphase. Here we study the role of Syndapin (Synd), an F-BAR domain containing protein in apical cap remodelling prior to furrow extension. synd depletion showed larger apical caps. STED super-resolution and TIRF microscopy showed long apical actin protrusions in caps in interphase and short protrusions in metaphase in control embryos. synd depletion led to sustained long protrusions even in metaphase. Loss of Arp2/3 function in synd mutants partly reverted defects in apical cap expansion and protrusion remodelling. MyosinII levels were decreased in synd mutants and MyosinII mutant embryos have been previously reported to have expanded caps. We propose that Syndapin function limits branching activity during cap expansion and affects MyosinII distribution in order to shift actin remodeling from apical cap expansion to favor lateral furrow extension.

Juan Martin D'Ambrosio, Veronique Albanese, Nicolas-Frederic Lipp, Lucile Fleuriot, Delphine Debayle, Guillaume Drin, and Alenka Copic

Osh6 and Osh7 are lipid transfer proteins (LTPs) that move phosphatidylserine (PS) from the endoplasmic reticulum (ER) to the plasma membrane (PM). High PS level at the PM is key for many cellular functions. Intriguingly, Osh6/7 localize to ER-PM contact sites, although they lack membrane-targeting motifs, in contrast to multidomain LTPs that both bridge membranes and convey lipids. We show that Osh6 localization to contact sites depends on its interaction with the cytosolic tail of the ER-PM tether Ist2, a homologue of TMEM16 proteins. We identify a motif in the Ist2 tail, conserved in yeasts, as the Osh6-binding region, and we map an Ist2-binding surface on Osh6. Mutations in the Ist2 tail phenocopy osh6 osh7 deletion: they decrease cellular PS levels, and block PS transport to the PM. Our study unveils an unexpected partnership between a TMEM16-like protein and a soluble LTP, which together mediate lipid transport at contact sites.

Westley Heydeck, Brian A. Bayless, Alexander J. Stemm-Wolf, Eileen T. O'Toole, Amy S. Fabritius, Courtney Ozzello, Marina Nguyen, and Mark Winey

Basal bodies (BBs) are microtubule-based organelles that template and stabilize cilia at the cell surface. Centrins ubiquitously associate with BBs and function in BB assembly, maturation, and stability. Human POC5 (hPOC5) is a highly conserved centrin-binding protein that binds centrins through Sfi1p-like repeats and is required for building full-length, mature centrioles. Here, we use the BB-rich cytoskeleton of Tetrahymena thermophila to characterize Poc5 BB functions. Tetrahymena Poc5 (TtPoc5) uniquely incorporates into assembling BBs and is then removed from mature BBs prior to ciliogenesis. Complete genomic knockout of TtPOC5 leads to a significantly increased production of BBs yet a markedly reduced ciliary density, both of which are rescued by reintroduction of TtPoc5. A second Tetrahymena POC5-like gene, SFR1, is similarly implicated in modulating BB production. When TtPOC5 and SFR1 are co-deleted, cell viability is compromised, and levels of BB overproduction are exacerbated. Overproduced BBs display defective transition zone formation and a diminished capacity for ciliogenesis. This study uncovers a requirement for Poc5 in building mature BBs, providing a possible functional link between hPOC5 mutations and impaired cilia.

The generalized Darwin–Hamilton equations [Wuttke (2014). Acta Cryst. A70, 429–440] describe multiple Bragg reflection from a thick, ideally imperfect crystal. These equations are simplified by making full use of energy conservation, and it is demonstrated that the conventional two-ray Darwin–Hamilton equations are obtained as a first-order approximation. Then an efficient numeric solution method is presented, based on a transfer matrix for discretized directional distribution functions and on spectral collocation in the depth coordinate. Example solutions illustrate the orientational spread of multiply reflected rays and the distortion of rocking curves, especially if the detector only covers a finite solid angle.

The post Conservators challenged by contemporary artworks at the Hirshhorn Museum appeared first on Smithsonian Insider.

If a supernova vaporized Earth’s ozone layer, what would happen to life in the ocean? Smithsonian biologist Pat Neale shows how UV rays could harm […]

The post If a supernova vaporized our ozone layer, what would happen to life on Earth? appeared first on Smithsonian Insider.

“The Outwin 2016: American Portraiture Today” exhibition is on view at the Smithsonian’s National Portrait Gallery from March 12, 2016 – January 8, 2017. The Outwin […]

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Known around the world for personal and culturally inspired choreography, Dana Tai Soon Burgess has been named the Smithsonian’s first choreographer-in-residence at the National Portrait […]

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Smithsonian staff gathered on Thursday, June 1 outside the National Museum of African American History and Culture to show their support and listen to Director […]

The post Smithsonian staff rally to support African American History Museum after noose incident appeared first on Smithsonian Insider.

On February 12, 2018, the Smithsonian’s National Portrait Gallery unveiled its commissioned portraits of former President Barack Obama and Mrs. Michelle Obama by artists Kehinde […]

The post Installation of the Obama portraits appeared first on Smithsonian Insider.

Curator Taína Caragol gives you a tour of a portrait of the late sculptor Luis Jiménez by Gaspar Enríquez at our National Portrait Gallery

The post Portraiture and the Mexican American Experience appeared first on Smithsonian Insider.

Police say TSA agent Gerardo Hernandez was shot and killed last Friday at the base of the escalators of LAX Terminal 3, and not at the checkpoint gates.  Paul Ciancia is accused of killing Hernandez and wounding several others.  Ciancia remains hospitalized in critical condition.

Steve Julian: Business analyst Mark Lacter, how did the airlines respond to shooting and its aftermath?

Mark Lacter: Generally pretty well, Steve, considering that the airport was effectively closed for several hours on Friday, and most of Terminal 3 was out of commission until Saturday afternoon.  You know, there's always this precarious balance in operating airlines and airports, even in the best of circumstances.  Just so many flights coming in and going out, and so many thousands people using the facility at any given time - and it really doesn't take much to upset the balance.  So, when you have something horrific take place and you see all those travelers stranded outside the terminals, the ripple effects are enormous - not just at LAX but all over the country.

Julian: More than a thousand flights were either canceled or delayed on Friday.

Lacter: And, there was a further complication because the airlines flying out of Terminal 3 are not the legacy carriers like United, American, and Delta that have all kinds of resources, but smaller operations with less flexibility.  It's not like there's an empty aircraft just sitting in a hangar waiting to take passengers wherever they want to go.  Actually, the airlines have gotten better at arranging re-bookings when there's a snowstorm or some other emergency that gives them advance warning.  But obviously, there was no advance warning last Friday, so the carriers needed to improvise in handling passengers whose flights were cancelled.

Julian: What did they do?

Lacter: One step was waiving the fees normally charged to re-book flights (and that's gotten to be a pretty penny).  Another was waiving the difference in the price of the original ticket and the re-booked ticket.  But, the policies varied according to the airline, and we heard about travelers not receiving hotel or food vouchers, or having to buy a brand new ticket on another airline if they wanted to avoid the wait - and that can be expensive.  Which raises another issue: planes tend to be completely full these days because airlines have been cutting back on the number of flights.  And that can be a problem if you're taking a route that doesn't have too many flights in the first place.  So, it gets really complicated.

Julian: Why do you think we haven't we heard more horror stories from passengers?

Lacter: Well, look at the cities that the airlines in Terminal 3 fly to - New York, San Francisco, Seattle, Dallas.  They're all served by several other carriers.  L.A. to New York, in particular, is one of the busiest routes in the world, which means that it's also one of the most competitive.  So, even if your flight was cancelled, there's a good chance you'd be able to find space by Saturday (which is normally a slower day for air travel).  This is a big reason, in general, why people like LAX.

Julian: Why don't other local airports handle more of the load?

Lacter: You might remember a few years ago local officials were promoting something called "regionalization" - the idea was that as LAX maxed out on the number of passengers it was allowed to handle each year, then other airports would make up the difference - places like Ontario, Bob Hope in Burbank, and John Wayne in Orange County.

Julian: Right, and they talked about easing traffic congestion by spreading around the flights.

Lacter: Well, regionalization never happened because, first of all, passenger levels at L.A. International didn't come close to maxing out.  But, more importantly, because the airlines decided that using LAX was more efficient for everything from handling baggage to arranging international connections.  So, through the first nine months of the year, passenger traffic at LAX is up 4.2 percent from a year earlier, while at Ontario traffic was down 9.3 percent.  And, we've seen that John Wayne, Bob Hope, and Long Beach are all struggling.  Of course, the challenge at a busy place like LAX is making it as safe as possible, and that will no doubt become a priority in the weeks ahead.

Mark Lacter writes for Los Angeles Magazine and pens the business blog at LA Observed.com.

This content is from Southern California Public Radio. View the original story at SCPR.org.

The Windows Defender Browser Protection tech support scam is a fake web site alert that states that Windows Defender Browser Extension detected someone to hack your bank account.

This article was published first at Remove the Windows Defender Browser Protection Tech Support Scam

Latinus 9333 is the Latin translation of the so-called Tacuinum sanitatis, a medieval handbook on wellness written in Arabic by the 11th-century physician ibn Butlan. It deals with factors influencing human health: from the air, the environment and food, to physical exercise and sexual activity.

The post Medieval book is important resource for how plants were once collected, treated and used appeared first on Smithsonian Insider.

New results from a massive study at the Smithsonian Tropical Research Institute show that interactions among community members play an important role in determining which organisms thrive.

The post Tropical tree study shows interactions with neighbors plays an important role in tree survival appeared first on Smithsonian Insider.

The post Smithsonian paleobotanist Scott Wing discusses ancient global warming & what it portends for the future appeared first on Smithsonian Insider.

This year’s El Niño event is one of the strongest on record and is still ramping up. Large parts of the tropics are turning into […]

The post Major El Nino Perfect opportunity for Global Change Research appeared first on Smithsonian Insider.

How much is a wetland worth? It’s a question that has plagued policymakers, scientists and other leaders looking to protect their communities and slow down […]

The post New report enables creation of carbon credits for restored wetlands appeared first on Smithsonian Insider.

The report of the Executive Committee for 2017 is presented.

If you try to open a text file with UTF-16 or UTF-32 encoding, the Import Tool displays a warning message stating that the encoding is not supported.  If you continue to load the file anyways, it is opened with UTF-8 encoding, and the file may not be displayed or imported as expected.This bug exists in the following release(s):
R2020a

This bug has a workaround

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Customers online want convenience, ease, and access. Fortunately, your business offers it all. Unfortunately, thats what fraudsters want too.