Copper‐mediated intra‐ligand oxygen transfer in gas‐phase complexes with 3‐nitrotyrosine

• Published in: Journal of Mass Spectrometry
• Main Authors: Vaisar, Tomáš, Heinecke, Jay W., Seymour, Jennifer L., Tureček, František
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1002/jms.829; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjms.829; https://onlinelibrary.wiley.com/doi/full/10.1002/jms.829

Abstract Gas‐phase ternary complexes with Cu(II) and 2,2′‐bipyridine (bpy) of tyrosine, 3‐aminotyrosine, 3‐nitrotyrosine and 3‐nitrotyrosine methyl ether are formed readily upon electrospraying aqueous methanol solutions containing the components. In contrast to Cu(bpy) complexes of tyrosine, 3‐aminotyrosine and other aromatic amino acids, the complexes of 3‐nitrotyrosine and its methyl ether undergo unusual collisionally activated dissociations (CADs) that involve Cu‐mediated transfer of an oxygen atom from the nitro group. With 3‐nitrotyrosine this results in an expulsion of carbonic acid, H 2 CO 3 , whereas with 3‐nitrotyrosine methyl ether an OH migration forms Cu(OH)bpy + as the predominant product. To the best of our knowledge, this is the first case of an intra‐ligand redox reaction in a gas‐phase organometallic complex. The reaction mechanism of this unusual dissociation was elucidated by a combination of isotope labeling, accurate mass measurements, energy‐resolved CAD mass spectra and density functional theory calculations of ion structures and relative energies. Copyright © 2005 John Wiley & Sons, Ltd.