title: Secondary organic aerosol-forming reactions of glyoxal with amino acids.
abstract: Glyoxal, the simplest and most abundant alpha-dicarbonyl compound in the atmosphere, is scavenged by clouds and aerosol, where it reacts with nucleophiles to form low-volatility products. Here we examine the reactions of glyoxal with five amino acids common in clouds. When glyoxal and glycine, serine, aspartic acid or ornithine are present at concentrations as low as 30/microM in evaporating aqueous droplets or bulk solutions, 1,3-disubstituted imidazoles are formed in irreversible second-order reactions detected by nuclear magnetic resonance (NMR), aerosol mass spectrometry (AMS) and electrospray ionization mass spectrometry (ESI-MS). In contrast, glyoxal reacts with arginine preferentially at side chain amino groups, forming nonaromatic five-membered rings. All reactions were accompanied by browning. The uptake of 45 ppb glyoxal by solid-phase glycine aerosol at 50% RH was also studied and found to cause particle growth and the production of imidazole measured by scanning mobility particle sizing and AMS, respectively, with a glyoxal uptake coefficient alpha = 0.0004. Comparison of reaction kinetics in bulk and in drying droplets shows that conversion of glyoxal dihydrate to monohydrate accelerates the reaction by over 3 orders of magnitude, allowing these reactions to occur at atmospheric conditions.
authors.affiliation: Department of Chemistry and Biochemistry, University of San Diego, 5998 Alcala Park, San Diego California 92110, USA. ddehaan@sandiego.edu
authors.forename: David O
authors.initials: DO
authors.lastname: De Haan
authors.forename: Ashley L
authors.initials: AL
authors.lastname: Corrigan
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Smith
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Stroik
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Turley
authors.forename: Frances E
authors.initials: FE
authors.lastname: Lee
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Tolbert
authors.forename: Jose L
authors.initials: JL
authors.lastname: Jimenez
authors.forename: Kyle E
authors.initials: KE
authors.lastname: Cordova
authors.forename: Grant R
authors.initials: GR
authors.lastname: Ferrell
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry*; D006037:Glyoxal / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009930:Organic Chemicals / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000336:Aerosols; D000596:Amino Acids; D009930:Organic Chemicals; D006037:Glyoxal