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Medford, MA, United States

Lacy M.,U.S. National Radio Astronomy Observatory | Ridgway S.E.,National Optical Astronomy Observatory | Gates E.L.,UCO Lick Observatory | Nielsen D.M.,University of Wisconsin - Madison | And 7 more authors.
Astrophysical Journal, Supplement Series | Year: 2013

We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate active galactic nuclei (AGNs) selected in the mid-infrared. This survey selects both normal and obscured AGNs closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L bol ∼ 1010 L to highly luminous quasars (L bol ∼ 1014 L ), all with redshifts ranging from 0 to 4.3. Samples of candidate AGNs were selected with mid-infrared color cuts at several different 24 μm flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGNs and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type 1 AGNs with blue continua, 294 (44%) are type 2 objects with extinctions AV ≳ 5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (AV ∼ 1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L bol > 1012 L , in the quasar regime. We present composite spectra for type 2 quasars and objects with no signs of AGN activity in their spectra. We also discuss the mid-infrared - emission-line luminosity correlation and present the results of cross correlations with serendipitous X-ray and radio sources. The results show that: (1) obscured objects dominate the overall AGN population, (2) mid-infrared selected AGN candidates exist which lack AGN signatures in their optical spectra but have AGN-like X-ray or radio counterparts, and (3) X-ray and optical classifications of obscured and unobscured AGNs often differ. © 2013. The American Astronomical Society. All rights reserved.. Source

Lacy M.,U.S. National Radio Astronomy Observatory | Petric A.O.,California Institute of Technology | Martinez-Sansigre A.,University of Portsmouth | Martinez-Sansigre A.,Network Physics | And 4 more authors.
Astronomical Journal | Year: 2011

We present optical through radio observations of the host galaxies of two dust-obscured, luminous quasars selected in the mid-infrared, at z = 2.62 and z = 2.99, including a search for CO emission. Our limits on the CO luminosities are consistent with these objects having masses of molecular gas ≲ 10 10 M ⊙, several times less than those of luminous submillimeter-detected galaxies at comparable redshifts. Their near-infrared spectral energy distributions, however, imply that these galaxies have high stellar masses (1011-1012 M ⊙). The relatively small reservoirs of molecular gas and low dust masses are consistent with them being relatively mature systems at high-z. © 2011. The American Astronomical Society. All rights reserved. Source

Tuffs University | Date: 2013-04-11

A recombinant

Go Y.-M.,Allergy and Critical Care Medicine | Roede J.R.,Allergy and Critical Care Medicine | Walker D.I.,Allergy and Critical Care Medicine | Walker D.I.,Tuffs University | And 6 more authors.
Molecular and Cellular Proteomics | Year: 2013

Thioredoxin (Trx) and GSH are the major thiol antioxidants protecting cells from oxidative stress-induced cytotoxicity. Redox states of Trx and GSH have been used as indicators of oxidative stress. Accumulating studies suggest that Trx and GSH redox systems regulate cell signaling and metabolic pathways differently and independently during diverse stressful conditions. In the current study, we used a mass spectrometry-based redox proteomics approach to test responses of the cysteine (Cys) proteome to selective disruption of the Trx- And GSH-dependent systems. Auranofin (ARF) was used to inhibit Trx reductase without detectable oxidation of the GSH/GSSG couple, and buthionine sulfoximine (BSO) was used to deplete GSH without detectable oxidation of Trx1. Results for 606 Cys-containing peptides (peptidyl Cys) showed that 36% were oxidized more than 1.3-fold by ARF, whereas BSO-induced oxidation of peptidyl Cys was only 10%. Mean fold oxidation of these peptides was also higher by ARF than BSO treatment. Analysis of potential functional pathways showed that ARF oxidized peptides associated with glycolysis, cytoskeleton remodeling, translation and cell adhesion. Of 60 peptidyl Cys oxidized due to depletion of GSH, 41 were also oxidized by ARF and included proteins of translation and cell adhesion but not glycolysis or cytoskeletal remodeling. Studies to test functional correlates showed that pyruvate kinase activity and lactate levels were decreased with ARF but not BSO, confirming the effects on glycolysis-associated proteins are sensitive to oxidation by ARF. These data show that the Trx system regulates a broader range of proteins than the GSH system, support distinct function of Trx and GSH in cellular redox control, and show for the first time in mammalian cells selective targeting peptidyl Cys and biological pathways due to deficient function of the Trx system. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc. Source

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