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Tipton, JeremiahD.,Tran, John C.,Catherman, Adam D.,Ahlf, Dorothy R.,Durbin, Kenneth R.,Lee, Ji Eun,Kellie, John F.,Kelleher, Neil L.,Hendrickson, ChristopherL.,Marshall, Alan G. American ChemicalSociety 2012 ANALYTICAL CHEMISTRY - Vol.84 No.5
<P>Current high-throughput top-down proteomic platformsprovide routineidentification of proteins less than 25 kDa with 4-D separations.This short communication reports the application of technologicaldevelopments over the past few years that improve protein identificationand characterization for masses greater than 25 kDa. Advances in separationscience have allowed increased numbers of proteins to be identified,especially by nanoliquid chromatography (nLC) prior to mass spectrometry(MS) analysis. Further, a goal of high-throughput top-down proteomicsis to extend the mass range for routine nLC MS analysis up to 80 kDabecause gene sequence analysis predicts that ∼70% of the humanproteome is transcribed to be less than 80 kDa. Normally, large proteinsgreater than 50 kDa are identified and characterized by top-down proteomicsthrough fraction collection and direct infusion at relatively lowthroughput. Further, other MS-based techniques provide top-down proteincharacterization, however at low resolution for intact mass measurement.Here, we present analysis of standard (up to 78 kDa) and whole celllysate proteins by Fourier transform ion cyclotron resonance massspectrometry (nLC electrospray ionization (ESI) FTICR MS). The separationplatform reduced the complexity of the protein matrix so that, at14.5 T, proteins from whole cell lysate up to 72 kDa are baselinemass resolved on a nano-LC chromatographic time scale. Further, theresults document routine identification of proteins at improved throughputbased on accurate mass measurement (less than 10 ppm mass error) ofprecursor and fragment ions for proteins up to 50 kDa.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2012/ancham.2012.84.issue-5/ac202651v/production/images/medium/ac-2011-02651v_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac202651v'>ACS Electronic Supporting Info</A></P>
Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma
Mahaney, W.C.,Kalm, V.,Krinsley, D.H.,Tricart, P.,Schwartz, S.,Dohm, J.,Kim, K.J.,Kapran, B.,Milner, M.W.,Beukens, R.,Boccia, S.,Hancock, R.G.V.,Hart, K.M.,Kelleher, B. Elsevier 2010 Geomorphology Vol.116 No.1
<P><B>Abstract</B></P><P>A carbon-rich black layer encrusted on a sandy pebbly bed of outwash in the northern Venezuelan Andes, previously considered the result of an alpine grass fire, is now recognized as a ‘black mat’ candidate correlative with Clovis Age sites in North America, falling within the range of ‘black mat’ dated sites (~12.9ka cal BP). As such, the bed at site MUM7B, which dates to <11.8ka <SUP>14</SUP>C years BP (raw dates) and appears to be contemporaneous with the Younger Dryas (YD) cooling event, marks a possibly much more extensive occurrence than previously identified. No fossils (megafauna) or tool assemblages were observed at this newly identified candidate site (3800a.m.s.l.), as in the case of the North American sites. Here, evidence is presented for an extraterrestrial impact event at ~12.9ka. The impact-related Andean bed, located ~20cm above 13.7–13.3ka cal BP alluvial and glaciolacustrine deposits, falls within the sediment characteristics and age range of ‘black mat’ dated sites (~12.9ka cal BP) in North America. Site sediment characteristics include: carbon, glassy spherules, magnetic microspherules, carbon mat ‘welded’ onto coarse granular material, occasional presence of platinum group metals (Rh and Ru), planar deformation features (pdfs) in fine silt-size fragmental grains of quartz, as well as orthoclase, and monazite (with an abundance of Rare Earth Elements—REEs). If the candidate site is ‘black mat’, correlative with the ‘black mat’ sites of North America, such an extensive occurrence may support the hypothesized airburst/impact over the Laurentide Glacier, which led to a reversal of Allerød warming and the onset of YD cooling and readvance of glaciers. While this finding does not confirm such, it merits further investigation, which includes the reconnaissance for additional sites in South America. Furthermore, if confirmed, such an extensive occurrence may corroborate an impact origin.</P>