293 research outputs found

    Spectroscopy of broad absorption line quasars at 3≲z≲53\lesssim z \lesssim 5 -- I: evidence for quasar winds shaping broad/narrow emission line regions

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    We present an observational study of 22 broad absorption line quasars (BAL QSOs) at 3≲z≲53\lesssim z \lesssim5 based on optical/near-IR spectroscopy, aiming to investigate quasar winds and their effects. The near-IR spectroscopy covers the \hb\ and/or \mgii\ broad emission lines (BELs) for these quasars, allowing us to estimate their central black hole (BH) masses in a robust way. We found that our BAL QSOs on average do not have a higher Eddington ratio than that from non-BAL QSOs matched in redshift and/or luminosity. In a subset consisting of seven strong BAL QSOs possessing sub-relativistic BAL outflows, we see the prevalence of large \civ-BEL blueshift (∼\sim3100 km s−1^{-1}) and weak \oiii\ emission (particularly the narrow \oiiiλ\lambda5007 component), indicative of nuclear outflows affecting the narrow emission-line (NEL) regions. In another subset consisting of thirteen BAL QSOs having simultaneous observations of \mgii\ and \hb, we found a strong correlation between 3000~\AA\ and 5000~\AA\ monochromatic luminosity, consistent with that from non-BAL QSOs matched in redshift and luminosity; however, there is no correlation between \mgii\ and \hb\ in FWHM, likely due to nuclear outflows influencing the BEL regions. Our spectroscopic investigations offer strong evidence that the presence of nuclear outflows plays an important role in shaping the BEL/NEL regions of these quasars and possibly, regulating the growth of central supermassive black holes (SMBHs). We propose that BEL blueshift and BAL could be different manifestations of the same outflow system viewed at different sightlines and/or phases.Comment: 13 pages, 10 figures. Accepted for publication in Ap

    Cloning and function analysis of a Saussurea involucrata LEA4 gene

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    Late embryogenesis abundant proteins (LEA) help adapt to adverse low-temperature environments. The Saussurea involucrate SiLEA4, which encodes a membrane protein, was significantly up-regulated in response to low temperature stress. Escherichia coli expressing SiLEA4 showed enhanced low-temperature tolerance, as evident from the significantly higher survival numbers and growth rates at low temperatures. Moreover, tomato strains expressing SiLEA4 had significantly greater freezing resistance, due to a significant increase in the antioxidase activities and proline content. Furthermore, they had higher yields due to higher water utilization and photosynthetic efficiency under the same water and fertilizer conditions. Thus, expressing SiLEA4 has multiple advantages: (1) mitigating chilling injury, (2) increasing yields, and (3) water-saving, which also indicates the great potential of the SiLEA4 for breeding applications

    Induction of APOBEC3 family proteins, a defensive maneuver underlying interferon-induced anti–HIV-1 activity

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    Apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G), a cytidine deaminase, is a recently recognized innate intracellular protein with lethal activity against human immunodeficiency virus (HIV). Packaged into progeny virions, APOBEC3G enzymatic activity leads to HIV DNA degradation. As a counterattack, HIV virion infectivity factor (Vif) targets APOBEC3G for proteasomal proteolysis to exclude it from budding virions. Based on the ability of APOBEC3G to antagonize HIV infection, considerable interest hinges on elucidating its mechanism(s) of regulation. In this study, we provide the first evidence that an innate, endogenous host defense factor has the potential to promote APOBEC3G and rebuke the virus-mediated attempt to control its cellular host. We identify interferon (IFN)-α as a potent inducer of APOBEC3G to override HIV Vif neutralization of APOBEC3 proteins that pose a threat to efficient macrophage HIV replication. Our data provide a new dimension by which IFN-α mediates its antiviral activity and suggest a means to render the host nonpermissive for viral replication

    Secretory Leukocyte Protease Inhibitor Binds to Annexin II, a Cofactor for Macrophage HIV-1 Infection

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    The distribution of secretory leukocyte protease inhibitor (SLPI) at entry portals indicates its involvement in defending the host from pathogens, consistent with the ability of SLPI to inhibit human immunodeficiency virus (HIV)-1 infection by an unknown mechanism. We now demonstrate that SLPI binds to the membrane of human macrophages through the phospholipid-binding protein, annexin II. Based on the recent identification of human cell membrane phosphatidylserine (PS) in the outer coat of HIV-1, we define a novel role for annexin II, a PS-binding moiety, as a cellular cofactor supporting macrophage HIV-1 infection. Moreover, this HIV-1 PS interaction with annexin II can be disrupted by SLPI or other annexin II–specific inhibitors. The PS–annexin II connection may represent a new target to prevent HIV-1 infection
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