Mass Spectrometry
Online ISSN : 2186-5116
Print ISSN : 2187-137X
Original Article
OH-Radical Oxidation of Lung Surfactant Protein B on Aqueous Surfaces
Shinichi EnamiAgustín J. Colussi
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2018 Volume 7 Issue 2 Pages 1-7


Air pollutants generate reactive oxygen species on lung surfaces. Here we report how hydroxyl radicals (·OH) injected on the surface of water react with SP-B1–25, a 25-residue polypeptide surrogate of human lung surfactant protein B. Our experiments consist of intersecting microjets of aqueous SP-B1–25 solutions with O3/O2/H2O/N2(g) gas streams that are photolyzed into ·OH(g) in situ by 266 nm laser nanosecond pulses. Surface-sensitive mass spectrometry enables us to monitor the prompt (<10 μs) and simultaneous formation of primary On-containing products/intermediates (n≤5) triggered by the reaction of ·OH with interfacial SP-B1–25. We found that O-atoms from both O3 and ·OH are incorporated into the reactive cysteine Cys8 and Cys11 and tryptophan Trp9 components of the hydrophobic N-terminus of SP-B1–25 that lies at the topmost layers of the air–liquid interface. Remarkably, these processes are initiated by ·OH additions rather than by H-atom abstractions from S–H, C–H, or N–H groups. By increasing the hydrophilicity of the N-terminus region of SP-B1–25, these transformations will impair its role as a surfactant.

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© 2018 Shinichi Enami and Agustín J. Colussi. This is an open access article distributed under the terms of Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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