title: Morphology and primary crystal structure of a silk-like protein polymer synthesized by genetically engineered Escherichia coli bacteria.
abstract: The morphology and primary crystal structure of SLPF, a protein polymer produced by genetically engineered Escherichia coli bacteria, were characterized. SLPF is a segmented copolymer consisting of amino acid sequence blocks modeled on the crystalline segments of silk fibroin and the cell attachment domain of human fibronectin. Wide angle x-ray scattering (WAXS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and molecular simulations were used to analyze the primary crystal structure of SLPF. TEM experiments conducted on SLPF droplets cast from formic acid on amorphous carbon film demonstrated that these protein films have a microstructure formed of woven sheaves. The sheaves are composed of well-defined whisker crystallites. The width of the whiskers, 11.8 +/- 2.2 nm, may be correlated to the length of the silk-like segment in SLPF as predicted by molecular simulations. WAXS data, TEM images, SAED, patterns, molecular simulations, and theoretical diffraction patterns all were consistent with the crankshaft model proposed for Silk I by Lotz and Keith.
authors.affiliation: Macromolecular Science and Engineering Center, College of Engineering, University of Michigan, Ann Arbor 48109-2136.
authors.forename: J P
authors.initials: JP
authors.lastname: Anderson
authors.forename: J
authors.initials: J
authors.lastname: Cappello
authors.forename: D C
authors.initials: DC
authors.lastname: Martin
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000032:analysis* / Q000737:chemistry*; D001704:Biopolymers; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D005349:Fibroins; D005353:Fibronectins; D005818:Genetic Engineering / Q000379:methods; D019476:Insect Proteins; D008969:Molecular Sequence Data; D011108:Polymers / Q000032:analysis* / Q000737:chemistry*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000235:genetics*; D011993:Recombinant Fusion Proteins; D012542:Scattering, Radiation; D047011:Silk; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D005353:Fibronectins; D019476:Insect Proteins; D011108:Polymers; D011506:Proteins; D011993:Recombinant Fusion Proteins; D047011:Silk; C089172:silk-like protein polymer; D005349:Fibroins