Abstract
The theory for the determination of relative mass from darkfield electron micrographs is derived, and its limitations are indicated. For our geometry of darkfield apertures and at a beam voltage of 80 kV, a linear relationship between the scattering mass density and the density on the photographic plate is found experimentally to be valid for mass thicknesses of biological material up to 900 . Two applications of relative mass measurement in unstained ribosome preparations are shown. The mass ratio of the 50 S and the 30 S ribosomal subunits was found to be 1.83, which comes close to the mass ratio determined by hydrodynamic methods. It also proved possible to identify unfolded 30 S subunits as such by comparing their relative mass with the compact form. The minimum mass detected is about 2 × 10 −19 g. This represents an increase in effective sensitivity over the related method as applied to brightfield electron micrographs by a factor of about 1 000.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
