Damage of aromatic amino acids by the atmospheric free radical oxidant NO3˙ in the presence of NO2˙, N2O4, O3 and O2

Abstract

Analysis of the products formed in the reaction of NO(3)˙ with the N- and C-protected aromatic amino acids 1-5, which was performed under conditions that simulate exposure of biosurfaces to environmental pollutants, revealed insight how this important atmospheric free-radical oxidant can cause irreversible damage. In general, NO(3)˙ induced electron transfer at the aromatic ring is the exclusive initial pathway in a multi-step sequence, which ultimately leads to nitroaromatic compounds. In the reaction of NO(3)˙ with tryptophan 5 tricyclic products 12 and 13 are formed through an intramolecular, oxidative cyclization involving the amide moiety. In addition to this, strong indication for formation of N-nitrosamides was obtained, which likely result from reaction with N(2)O(4) through an independent non-radical pathway.

Light-induced protein nitration and degradation with HONO emission

“…Similar NO 2 uptake coefficients on humic acid were observed by Han et al (2016). George et al (2005) reported about a 2-fold increased NO 2 uptake coefficients for irradiated organic substrates (benzophenone, catechol, anthracene) compared to dark conditions, in the order of (0.6-5) × 10 −6 . NO 2 uptake coefficients on gentisic acid and tannic acid were in between (3.3-4.8) × 10 −7 (Sosedova et al, 2011), still higher than on fresh soot or dust (about 1 × 10 −7 ; Monge et al, 2010;Ndour et al, 2008).…”

“…Measured mixing ratios are typically about 1 order of magnitude higher than simulated ones, and an additional source of 200-800 ppt h −1 would be required to explain observed mixing ratios Acker et al, 2006;Li et al, 2012;Su et al, 2008;Elshorbany et al, 2012;Meusel et al, 2016), indicating that estimates of daytime HONO sources are still under debate. It was suggested that HONO arises from the photolysis of nitric acid and nitrate or by heterogeneous photochemistry of NO 2 on organic substrates and soot (Zhou et al, 2001(Zhou et al, , 2002(Zhou et al, and 2003Villena et al, 2011;Ramazan et al, 2004;George et al, 2005;Sosedova et al, 2011;Monge et al, 2010;Han et al, 2016). Stemmler et al (2006Stemmler et al ( , 2007 found HONO formation on light-activated humic acid, and field studies showed that HONO formation correlates with aerosol surface area, NO 2 and solar radiation (Su et al, 2008;Reisinger, 2000;Costabile et al, 2010;Wong et al, 2012;Sörgel et al, 2015) and is increased during foggy periods (Notholt et al, 1992).…”

Atmospheric chemistry of bioaerosols: heterogeneous and multiphase reactions with atmospheric oxidants and other trace gases

“…108,109 In the case of aromatic dipeptides, in addition to oxidation at the ring, the oxidative damage of dipeptide linkage occurs in the aromatic N- and C-protected dipeptides. 110 The results strongly suggest that this important atmospheric oxidant could potentially cause damage to peptides lining the respiratory tract and may contribute to pollution-derived diseases.…”

Damage of polyesters by the atmospheric free radical oxidant NO3•: a product study involving model systems

“…In the absence of any reactants the resulting radical cation 3 •+ undergoes deprotonation to give benzyl radical 7 , in analogy to the mechanism of the NO 3 • -induced oxidation of aromatic amino acids and nucleosides [10–13]. This mechanism is supported by findings by Steenken et al, who showed that in the reaction of alkylaromatic compounds with NO 3 • ET and deprotonation can occur practically in a concerted fashion in the case of highly electron-rich arenes, while in the case of less activated alkylaromatic compounds the intermediate radical cation has a lifetime on the nanosecond time scale [23].…”

“…NO 3 • , which is formed through reaction of the atmospheric pollutants nitrogen dioxide, NO 2 • , with ozone, O 3 (Scheme 1) [7–8], reacts with organic compounds through various pathways, such as hydrogen abstraction (HAT) and addition to π systems. Most importantly, NO 3 • is one of the strongest free-radical oxidants known [ E (NO 3 • /NO 3 − ) = 2.3–2.5 V vs NHE] [9], and recent product studies by us revealed that NO 3 • readily damages aromatic amino acids and pyrimidine nucleosides through an oxidative pathway [10–13]. Thus, the ease by which model compounds of biologically important macromolecules are attacked by NO 3 • leads inevitably to the question, how resistant synthetic polymers are towards oxidative damage by this environmental free-radical species, in particular in conjunction with other atmospheric radical and non-radical oxidants, which are in direct contact with these materials.…”