Aerosol proteinaceous matter is comprised of a substantial fraction of bioaerosols. Its origins and interactions in the atmosphere remain poorly understood. We present observations of total proteins, combined, and free amino acids (CAAs and FAAs) in fine particulate matter (PM2.5) samples in urban Beijing before and during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. The decreases in proteins, CAAs and FAAs levels were observed after the implementation of restrictive emission controls.
