ABSTRACT
Modern techniques of electron microscopy provide a simple and reliable visualization of protein structure at a resolution of 2-3 nm. In 1981, our group [1] and the laboratory of Engel et al. [2] independently published images of plasma fibronectin. The two studies were very largely in agreement in showing the molecule to be a long, thin strand with several or many points of flexibility. Additional details of the structure have been obtained by electron microscopy of large proteolytic fragments (domains) [1,3] and by microscopy of the molecule in different conformations [4]. Recently published data on the amino acid sequence [5] and gene splicing [6] suggest a more detailed structural model consistent with the shape and dimensions seen in the electron microscope images.
