"The proposed project aims to explain the formation of several components of secondary organic aerosol (SOA), which constitutes a significant fraction of the fine aerosol in the atmosphere, and largely contributes to aerosol effects that influence climate, weather, air quality, human health and condition of the biosphere. The analytical and predictive modelling of this influence requires the detailed understanding of numerous chemical reactions that contribute to the formation and further transformation of SOA in the gaseous, heterogeneous and aqueous atmospheric systems. Models that contain all possible reactants and reactions are too large to be solved, hence have to be reduced based on a thorough understanding of the underlying chemistry and kinetics. By now, only a small fraction of the possible reactions has been explained, and roughly 20% of SOA has been identified. One of the most important precursors of SOA is isoprene – a dominant non-methane volatile organic compound emitted to the atmosphere mostly from biogenic sources. In the atmosphere, isoprene is oxidised to a vast variety of products. The proposed project focuses on the aqueous-phase reactions of isoprene oxidation products – methacrolein, methyl vinyl ketone and methacrylic acid – with sulphate radical-anions, which produce SOA relevant compounds, including organosulphates, and occur in cloud droplets. Sulphate radical-anions are reactive intermediates generated in cloud water during the autoxidation of sulphur dioxide or inorganic sulphites catalysed by transition metal ions. Products, rate constants and mechanisms of these reactions will be studied in laboratory experiments by advanced organic mass spectrometry, kinetic analysis and computer simulation. The expected results will extend the knowledge on the formation of recently discovered compounds, such as organosulphates, in cloud water and SOA particles, and can be used for description of multiphase and aerosol chemistry in atmospheric models."