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Published November 21, 2018 | Supplemental Material + Published
Journal Article Open

OH-Radical Oxidation of Lung Surfactant Protein B on Aqueous Surfaces


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-B_(1–25), a 25-residue polypeptide surrogate of human lung surfactant protein B. Our experiments consist of intersecting microjets of aqueous SP-B_(1–25) solutions with O_3/O_2/H_2O/N_2(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 O_n-containing products/intermediates (n ≤ 5) triggered by the reaction of ·OH with interfacial SP-B_(1–25). We found that O-atoms from both O_3 and ·OH are incorporated into the reactive cysteine Cys_8 and Cys_(11) and tryptophan Trp_9 components of the hydrophobic N-terminus of SP-B_(1–25) 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-B_(1–25), these transformations will impair its role as a surfactant.

Additional Information

© 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. Received: August 21, 2018. Accepted: October 11, 2018. Published online: November 21, 2018. S. E. is grateful to the Japan Science and Technology Agency (JST) PRESTO program and the Research Foundation for Opto-Science and Technology. S. E. is indebted to Prof. Hiroshi Masuhara for his kind advices. A. J. C. acknowledges support from the National Science Foundation USA, grant AGS-1744353. SUPPORTING INFORMATION AVAILABLE: Additional data and experimental details. This material is available free of charge via the Internet.

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Supplemental Material - 7_S0077_1.pdf


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