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Sachin, Kalme,Jadhav, Vinod H.,Kim, Eun-Mi,Kim, Hye Lan,Lee, Sang Bong,Jeong, Hwan-Jeong,Lim, Seok Tae,Sohn, Myung-Hee,Kim, Dong Wook American Chemical Society 2012 Bioconjugate chemistry Vol.23 No.8
<P>We introduce the high-throughput synthesis of various <SUP>18</SUP>F-labeled peptide tracers by a straightforward <SUP>18</SUP>F-labeling protocol based on a chemo-orthogonal strain-promoted alkyne azide cycloaddition (SPAAC) using aza-dibenzocyclootyne-substituted peptides as precursors with <SUP>18</SUP>F-azide synthon to develop peptide based positron emission tomography (PET) molecular imaging probes. The SPAAC reaction and subsequent chemo-orthogonal purification reaction with azide resin proceeded quickly and selectively under physiologically friendly reaction conditions (i.e., toxic chemical reagents-free, aqueous medium, room temperature, and pH ≈7), and provided four <SUP>18</SUP>F-labeled tumor targetable bioactive peptides such as cyclic Arg-Gly-Asp (cRGD) peptide, bombesin (BBN), c-Met binding peptide (cMBP), and apoptosis targeting peptide (ApoPep) in high radiochemical yields as direct injectable solutions without any HPLC purification and/or formulation processes. <I>In vitro</I> binding assay and <I>in vivo</I> PET molecular imaging study using the <SUP>18</SUP>F-labeled cRGD peptide also demonstrated a successful application of our <SUP>18</SUP>F-labeling protocol.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bcches/2012/bcches.2012.23.issue-8/bc3002425/production/images/medium/bc-2012-002425_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bc3002425'>ACS Electronic Supporting Info</A></P>
Jang, Sohye,Sachin, Kalme,Lee, Hui-jeong,Kim, Dong Wook,Lee, Hyun Soo American Chemical Society 2012 Bioconjugate chemistry Vol.23 No.11
<P>There are currently many methods available for labeling proteins in order to study their structure and function. However, the utility of these methods is hampered by low efficiency, slow reaction rates, nonbiocompatible reaction conditions, large-sized labeling groups, and the requirement of specific side chains such as cysteine or lysine. In this study, a simple and efficient method for protein labeling was developed, in which an azide-containing amino acid was introduced into a protein and conjugated to a labeling reagent by strain-promoted azide–alkyne cycloaddition (SPAAC). This method allowed us to label proteins by simply mixing a protein and a labeling reagent in physiological conditions with a labeling yield of approximately 80% in 120 min. In addition, the specificity of SPAAC made it possible to analyze the expression level of a protein quantitatively by simple mixing and SDS-PAGE analysis with no need for antibodies or multistep incubations. Because the genetic incorporation of the azide-containing amino acid can be generally applied to any protein and the SPAAC reaction is highly specific, this method should prove useful for labeling and analyzing proteins.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bcches/2012/bcches.2012.23.issue-11/bc300364z/production/images/medium/bc-2012-00364z_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bc300364z'>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>