Alpha-O Peptides AG 1 article published in JoVE Bioengineering Production of E. coli-expressed Self-Assembling Protein Nanoparticles for Vaccines Requiring Trimeric Epitope Presentation Christopher P. Karch1,2, Peter Burkhard3, Gary R. Matyas1, Zoltan Beck1,2 1U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 2Henry M. Jackson Foundation for the Advancement of Military Medicine, 3Alpha-O Peptides AG A detailed method is provided here describing the purification, refolding, and characterization of self-assembling protein nanoparticles (SAPNs) for use in vaccine development.