Recent field and laboratory evidence points towards a significant failure in our understanding of the atmospheric chemistry of isoprene in low NOx conditions and notably its impact on OH, significantly inhibiting our understanding of the atmosphere-biosphere-climate system. The multidisciplinary LAMUNIO proposal, including technique development, laboratory and chamber studies and modelling evaluation, will be a major step forward to innovatively investigate isoprene chemistry. LAMUNIO contains three workpackages looking at interferences in the FAGE technique for OH observation, particularly in environments dominated by biogenic emissions; studies of isoprene oxidation focusing particularly on OH and carbonyl measurement to validate proposed mechanisms; new techniques to study HO2 reactions relevant for low NOx chemistry. This proposal is timely and will provide underpinning laboratory studies to validate both measurement techniques and the proposed mechanisms that seek to explain the unexpected observations of high OH concentrations in environments dominated by the oxidation of isoprene in low NOx conditions. OH concentrations control the oxidative capacity of the atmosphere influencing important local (air quality) and global (methane concentrations and hence radiative forcing) issues. LAMUNIO will provide world class research and training opportunities and the proposed work is facilitated by the unique breadth of knowledge and infrastructure available at the University of Leeds.