Sialic Acid Mutarotation Is Catalyzed by the Escherichia coli β-Propeller Protein YjhT

The acquisition of host-derived sialic acid is an important virulence factor for some bacterial pathogens, but in vivo this sugar acid is sequestered in sialoconjugates as the {alpha}-anomer. In solution, however, sialic acid is present mainly as the β-anomer, formed by a slow spontaneous mutarotation. We studied the Escherichia coli protein YjhT as a member of a family of uncharacterized proteins present in many sialic acid-utilizing pathogens. This protein is able to accelerate the equilibration of the {alpha}- and β-anomers of the sialic acid N-acetylneuraminic acid, thus describing a novel sialic acid mutarotase activity. The structure of this periplasmic protein, solved to 1.5Å resolution, reveals a dimeric 6-bladed unclosed β-propeller, the first of a bacterial Kelch domain protein. Mutagenesis of conserved residues in YjhT demonstrated an important role for Glu-209 and Arg-215 in mutarotase activity. We also present data suggesting that the ability to utilize {alpha}-N-acetylneuraminic acid released from complex sialoconjugates in vivo provides a physiological advantage to bacteria containing YjhT

Commodity Price Volatility and World Market Integration since 1700

Poor countries are more volatile than rich countries, and we know this volatility impedes their growth. We also know that commodity price volatility is a key source of those shocks. This paper explores commodity and manufactures price over the past three centuries to answer three questions: Has commodity price volatility increased over time? The answer is no: there is little evidence of trend since 1700. Have commodities always shown greater price volatility than manufactures? The answer is yes. Higher commodity price volatility is not the modern product of asymmetric industrial organizations - oligopolistic manufacturing versus competitive commodity markets - that only appeared with the industrial revolution. It was a fact of life deep into the 18th century. Does world market integration breed more or less commodity price volatility? The answer is less. Three centuries of history shows unambiguously that economic isolation caused by war or autarkic policy has been associated with much greater commodity price volatility, while world market integration associated with peace and pro-global policy has been associated with less commodity price volatility. Given specialization and comparative advantage, globalization has been good for growth in poor countries at least by diminishing price volatility. But comparative advantage has never been constant. Globalization increased poor country specialization in commodities when the world went open after the early 19th century; but it did not do so after the 1970s as the Third World shifted to labor-intensive manufactures. Whether price volatility or specialization dominates terms of trade and thus aggregate volatility in poor countries is thus conditional on the century.

Stable dietary isotopes and mtDNA from Woodland period southern Ontario people: results from a tooth sampling protocol

AbstractBioarchaeological research must balance scholarly commitment to the generation of new knowledge, descendants' interests in their collective past, and the now common practice of rapid re-interment of excavated human remains. This paper documents the first results of a negotiated protocol built on the retention of one tooth per archaeologically derived skeleton, teeth that can then be used for destructive testing associated with ancient DNA and stable isotope investigations. Seven archaeological sites dating from the 13th to 16th centuries provided 53 teeth, 10 of which were subdivided between DNA and isotope labs. All tooth roots yielded haplogroup results, and five provided more detailed sequence results. Stable isotopes of carbon and nitrogen document heavy reliance on maize among all individuals, as well as reliance on a diverse range of fish. This work establishes baseline mtDNA information for Northern Iroquoians, and confirms the value of using dental tissues for dietary reconstruction. Particularly when human remains are fragmentary or co-mingled, this approach holds promise for ongoing incorporation of bioarchaeology into reconstructions of past peoples' lives

A connectivity portfolio effect stabilizes marine reserve performance

Well-managed and enforced no-take marine reserves generate important larval subsidies to neighboring habitats and thereby con-tribute to the long-term sustainability of fisheries. However, larval dispersal patterns are variable, which leads to temporal fluctua-tions in the contribution of a single reserve to the replenishment of local populations. Identifying management strategies that mit-igate the uncertainty in larval supply will help ensure the stability of recruitment dynamics and minimize the volatility in fishery catches. Here, we use genetic parentage analysis to show extreme variability in both the dispersal patterns and recruitment contribu-tion of four individual marine reserves across six discrete recruit-ment cohorts for coral grouper (Plectropomus maculatus) on the Great Barrier Reef. Together, however, the asynchronous contri-butions from multiple reserves create temporal stability in recruit-ment via a connectivity portfolio effect. This dampening effect reduces the variability in larval supply from individual reserves by a factor of 1.8, which effectively halves the uncertainty in the recruitment contribution of individual reserves. Thus, not only does the network of four marine reserves generate valuable larval subsidies to neighboring habitats, the aggregate effect of individual reserves mitigates temporal fluctuations in dispersal patterns and the replenishment of local populations. Our results indicate that small networks of marine reserves yield previously unrecog-nized stabilizing benefits that ensure a consistent larval supply to replenish exploited fish stocks

Optical to near-infrared transmission spectrum of the warm sub-Saturn HAT-P-12b

We present the transmission spectrum of HAT-P-12b through a joint analysis of data obtained from the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) and Wide Field Camera 3 (WFC3) and Spitzer, covering the wavelength range 0.3-5.0 $\mu$m. We detect a muted water vapor absorption feature at 1.4 $\mu$m attenuated by clouds, as well as a Rayleigh scattering slope in the optical indicative of small particles. We interpret the transmission spectrum using both the state-of-the-art atmospheric retrieval code SCARLET and the aerosol microphysics model CARMA. These models indicate that the atmosphere of HAT-P-12b is consistent with a broad range of metallicities between several tens to a few hundred times solar, a roughly solar C/O ratio, and moderately efficient vertical mixing. Cloud models that include condensate clouds do not readily generate the sub-micron particles necessary to reproduce the observed Rayleigh scattering slope, while models that incorporate photochemical hazes composed of soot or tholins are able to match the full transmission spectrum. From a complementary analysis of secondary eclipses by Spitzer, we obtain measured depths of $0.042\%\pm0.013\%$ and $0.045\%\pm0.018\%$ at 3.6 and 4.5 $\mu$m, respectively, which are consistent with a blackbody temperature of $890^{+60}_{-70}$ K and indicate efficient day-night heat recirculation. HAT-P-12b joins the growing number of well-characterized warm planets that underscore the importance of clouds and hazes in our understanding of exoplanet atmospheres.Comment: 25 pages, 19 figures, accepted for publication in AJ, updated with proof correction

Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries: II. omicron Draconis, a Candidate for Recent Low-Mass Companion Ingestion

To measure the stellar and orbital properties of the metal-poor RS CVn binary o Draconis (o Dra), we directly detect the companion using interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array. The H-band flux ratio between the primary and secondary stars is the highest confirmed flux ratio (370 +/- 40) observed with long-baseline optical interferometry. These detections are combined with radial velocity data of both the primary and secondary stars, including new data obtained with the Tillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at the Fred Lawrence Whipple Observatory and the 2-m Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We determine an orbit from which we find model-independent masses and ages of the components (M_A = 1.35 +\- 0.05 M_Sun, M_B = 0.99 +\- 0.02 M_Sun, system age = 3.0 -\+ 0.5 Gyr). An average of a 23-year light curve of o Dra from the Tennessee State University Automated Photometric Telescope folded over the orbital period newly reveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations. The modeled light curve for our system's stellar and orbital parameters confirm these ellipsoidal variations due to the primary star partially filling its Roche lobe potential, suggesting most of the photometric variations are not due to stellar activity (starspots). Measuring gravity darkening from the average light curve gives a best-fit of beta = 0.07 +\- 0.03, a value consistent with conventional theory for convective envelope stars. The primary star also exhibits an anomalously short rotation period, which, when taken with other system parameters, suggests the star likely engulfed a low-mass companion that had recently spun-up the star.Comment: 14 pages, 13 figures, Accepted to Ap

Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries: I. sigma Geminorum

To measure the properties of both components of the RS CVn binary sigma Geminorum (sigma Gem), we directly detect the faint companion, measure the orbit, obtain model-independent masses and evolutionary histories, detect ellipsoidal variations of the primary caused by the gravity of the companion, and measure gravity darkening. We detect the companion with interferometric observations obtained with the Michigan InfraRed Combiner (MIRC) at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array with a primary-to-secondary H-band flux ratio of 270+/-70. A radial velocity curve of the companion was obtained with spectra from the Tillinghast Reflector Echelle Spectrograph (TRES) on the 1.5-m Tillinghast Reflector at Fred Lawrence Whipple Observatory (FLWO). We additionally use new observations from the Tennessee State University Automated Spectroscopic and Photometric Telescopes (AST and APT, respectively). From our orbit, we determine model-independent masses of the components (M_1 = 1.28 +/- 0.07 M_Sun, M_2 = 0.73 +/- 0.03 M_Sun), and estimate a system age of 5 -/+ 1 Gyr. An average of the 27-year APT light curve of sigma Gem folded over the orbital period (P = 19.6027 +/- 0.0005 days) reveals a quasi-sinusoidal signature, which has previously been attributed to active longitudes 180 deg apart on the surface of sigma Gem. With the component masses, diameters, and orbit, we find that the predicted light curve for ellipsoidal variations due to the primary star partially filling its Roche lobe potential matches well with the observed average light curve, offering a compelling alternative explanation to the active longitudes hypothesis. Measuring gravity darkening from the light curve gives beta < 0.1, a value slightly lower than that expected from recent theory.Comment: Accepted to ApJ, 11 pages, 6 figures, 8 table

Spring warming in Yukon mountains is not amplified by the snow albedo feedback

Decreasing spring snow cover may amplify Arctic warming through the snow albedo feedback. To examine the impact of snowmelt on increasing temperature we used a 5,000 m elevation gradient in Yukon, Canada, extending from valley-bottom conifer forests, through middle elevation tundra, to high elevation icefields, to compare validated downscaled reanalysis air temperature patterns across elevational bands characterized by different patterns of spring snowmelt. From 2000 to 2014 we observed surface warming of 0.01 °C/a·1,000 m in May (0.14 °C/a at 1,000 m to 0.19 °C/a at 5,000 m), and uniform cooling of 0.09 °C/a in June at all elevations. May temperature trends across elevationally dependent land cover types were highly correlated with each other despite large variations in albedo and snow cover trends. Furthermore, a clear dependency of infrared skin temperature on snow cover mediated albedo decline was observed in tundra, but this was insufficient to influence average diurnal air temperature. We observed negative June temperature trends which we attribute to increasing daytime cloud cover because albedo and snow cover trends were unchanging. We conclude that 8-day and monthly averaged Spring air temperature trends are responding to a synoptic external forcing that is much stronger than the snow albedo feedback in sub-Arctic mountains