Biological Atomic Force Microscopic Imaging and Force Spectroscopy of Protein Constructs as Potential Anti-Malaria Vaccines

Abstract

Atomic force microscope (AFM) is quickly becoming a general nano-characterization tool for biomedical samples. Here we have used AFM imaging and single molecular force spectroscopy to characterize leading malaria vaccine candidates that are various recombinant forms of Plasmodium falciparum circumsporozoite protein (Plassmeyer, M., et al., 2009. J. Bio. Chem., 284:26951-63)). We have achieved high-resolution AFM single molecule imaging and force spectroscopy of these important antigens under various buffer and surface deposition conditions to better understand the recombinant protein constructs. The protein folding domains and tertiary structure features observed from AFM imaging and deduced from AFM force spectroscopy are closely correlated with accurate computational structural predictions derived from the primary sequences and bulk solution characterizations. Bio-AFM characterizations can discriminate alternative forms of recombinant proteins according to their oligomerization and surface presentations. Our results showcase AFM as an insightful tool of nanomedicine for in-depth understanding of single proteins and protein-protein interactions.