Unidirectional and rotary shadowing techniques have been applied in studying the surface structure of two types of intermediate filaments. Keratin filaments and neurofilaments demonstrate a approximately 21-nm axial periodicity which probably indicates the helical pitch of the outer shell of the filament. Analysis of unidirectionally shadowed keratin showed that the helix is left-handed. The observation of a left-handed helix of 21-nm pitch supports the three-stranded protofilament model of Fraser, Macrae, and Suzuki (1976, J. Mol. Biol. 108:435-452), and indicates that keratin filaments probably consist of 10 three-stranded protofilaments surrounding a core of three such protofilaments, as predicted by models based on x-ray diffraction of hard keratin filaments. Neurofilaments do not demonstrate an easily identifiable hand, so their consistency with the model is, as yet, uncertain.
Article| September 01 1982
Visualization of a 21-nm axial periodicity in shadowed keratin filaments and neurofilaments.
H P Erickson
Online Issn: 1540-8140
Print Issn: 0021-9525
J Cell Biol (1982) 94 (3): 592–596.
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L Milam, H P Erickson; Visualization of a 21-nm axial periodicity in shadowed keratin filaments and neurofilaments.. J Cell Biol 1 September 1982; 94 (3): 592–596. doi: https://doi.org/10.1083/jcb.94.3.592
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