title: Molecular shape of Lumbricus terrestris erythrocruorin studied by electron microscopy and image analysis.
abstract: The molecular structure of erythrocruorin (hemoglobin) from Lumbricus terrestris has been studied by electron microscopy of negatively stained particles. Over 1000 molecular projections were selected from a number of electron micrographs and were then classified by multivariate statistical image-processing techniques. The two main groups of top and side views were each subdivided into smaller classes with significantly different features. About half of the top-view projections exhibit perfect hexagonal symmetry at the current resolution of about 2.0 nm, while the other top views lack this symmetry, probably as a result of tilting of the molecules relative to the carbon support film. The side views were separated into two 'families', each associated with the two different stable side-view positions the molecules can take. From these narrow stable side-views, the two families of projections are, again, generated by tilting. The symmetry properties of the three non-tilted projections show that Lumbricus erythrocruorin has a pointgroup D6 (622) symmetry rather than D3 (32).
authors.affiliation: Fritz-Haber-Institut der Max-Planck Gesellschaft, Berlin, F.R.G.
authors.forename: E J
authors.initials: EJ
authors.lastname: Boekema
authors.forename: M
authors.initials: M
authors.lastname: van Heel
mesh_terms: D000818:Animals; D000845:Annelida / Q000032:analysis*; D004902:Erythrocruorins; D006454:Hemoglobins; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D015394:Molecular Structure
chemical_list: D004902:Erythrocruorins; D006454:Hemoglobins