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- Andõn, F. T., et al.
(author)
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Biodegradation of Single-Walled Carbon Nanotubes by Eosinophil Peroxidase
- 2013
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In: Small. - : Wiley-VCH Verlagsgesellschaft. - 1613-6810 .- 1613-6829. ; 9:16, s. 2721-2729
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Journal article (peer-reviewed)abstract
- Eosinophil peroxidase (EPO) is one of the major oxidant-producing enzymes during inflammatory states in the human lung. The degradation of single-walled carbon nanotubes (SWCNTs) upon incubation with human EPO and H2O 2 is reported. Biodegradation of SWCNTs is higher in the presence of NaBr, but neither EPO alone nor H2O2 alone caused the degradation of nanotubes. Molecular modeling reveals two binding sites for SWCNTs on EPO, one located at the proximal side (same side as the catalytic site) and the other on the distal side of EPO. The oxidized groups on SWCNTs in both cases are stabilized by electrostatic interactions with positively charged residues. Biodegradation of SWCNTs can also be executed in an ex vivo culture system using primary murine eosinophils stimulated to undergo degranulation. Biodegradation is proven by a range of methods including transmission electron microscopy, UV-visible-NIR spectroscopy, Raman spectroscopy, and confocal Raman imaging. Thus, human EPO (in vitro) and ex vivo activated eosinophils mediate biodegradation of SWCNTs: an observation that is relevant to pulmonary responses to these materials. Human eosinophil peroxidase (EPO) is able to degrade SWCNTs in vitro in the presence of H2O2. EPO is one of the major oxidant-generating enzymes present in human lungs during inflammatory states. The biodegradation of SWCNTs is evidenced also in an ex vivo culture system using primary murine eosinophils stimulated to undergo degranulation. These results are relevant to potential respiratory exposure to carbon nanotubes.
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| 2. |
- Wu, S. -W, et al.
(author)
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The discovery of a very massive star in W49
- 2014
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. L13-
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Journal article (peer-reviewed)abstract
- Context. Very massive stars (M > 100 M-circle dot) are very rare objects, but have a strong influence on their environment. The formation of this kind of objects is of prime importance in star formation, but observationally still poorly constrained. Aims. We report on the identification of a very massive star in the central cluster of the star forming region W49. Methods. We investigate near infrared K-band spectroscopic observations of W49 from VLT/ISAAC together with JHK images obtained with NTT/SOFI and LBT/LUCI. We derive the spectral type of W49nrl, the brightest star in the dense core of the central cluster of W49. Results. On the basis of its K-band spectrum, W49nrl is classified as an O2-3.5If* star with a K-band absolute magnitude of -6.27 +/- 0.10 mag. The effective temperature and bolometric correction are estimated from stars of similar spectral type. After comparison to the Geneva evolutionary models, we find an initial mass between 100 M-circle dot and 180 M-circle dot. Varying the extinction law results in a larger initial mass range of 90-250 M-circle dot
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