Single particle electron microscopy of native cell extracts

After the linking of genetic information to the biochemical composition of proteins in the mid 20th century, the emergent field of structural biology has focused on how the three-dimensional arrangement of atoms in a protein defines its cellular function. One rapidly evolving method for probing this structure-function relationship, and the focus of this work, is single particle transmission electron microscopy. Traditionally, single to few proteins of interest are first purified to near homogeneity from a biological source before structural characterization. However, a key advantage of electron microscopy over other methods is that proteins do not need to be purified, or in the case of electron tomography, even removed from the cell. The ability to study protein structure in as close to native conditions as possible can inform biology broadly. In this dissertation, I will present work towards expanding the use of single particle electron microscopy to native cell extracts. First, we explore a pilot analysis characterizing protein structures from chromatographically separated cell lysate guided by information from mass spectrometry. Extending on our initial studies, we next investigate protein structures from individual Caenorhabditis elegans embryos. We then introduce an image processing algorithm developed to assist single particle analysis of samples containing multiple distinct protein structures. Finally, we demonstrate an application combining methods presented in this dissertation to investigate protein-protein interactions in red blood cells and their structural architectures