The chemical components of the SSA model systems were selected based on the most recent molecular analyses of nascent submicron SSA; although, it is worth noting that only an estimated 25% of the total chemical species found in SSA has been fully characterized. There is, however, a consensus on the classes of molecules observed, namely, fatty acids, proteins, and saccharides, though their relative abundances in submicron SSA vary with ocean productivity, geographic region, season, and temperature. Fatty acids (FAs) comprise 2-80% of the observed organic species by mass, with chain lengths varying from 12-18 carbons for the most abundant subset. Our simplest system (System A, Figure ) is composed of an organic fraction containing only saturated FAs in a 1 : 2 : 4 : 3 ratio of lauric acid (LA) : myristic acid (MA) : palmitic acid (PA) : stearic acid (SA), with chain lengths 12, 14, 16, and 18 carbons, respectively. The mass fraction of proteinaceous material in SSA is also highly variable between individual particles. We chose to initialize our simple system with a number of Burkholderia cepacia lipases (BCLs). BCL is a robust enzyme found in SSA that has, notably, been observed to retain some activity after aerosolization. This enzyme was also selected because of its well-characterized structural, biological, and enzymatic properties, as well as the ease with which collaborators can incorporate it into subsequent laboratory studies. The number of lipases remains constant throughout our study at a mass fraction of approximately 3%. Finally, we initialized our simplest system with 0.4 M NaCl to reflect the concentration of seawater and nascent SSA.