Use of radial density plots to calibrate image magnification for frozen-hydrated specimens.
Accurate magnification calibration for transmission electron microscopy is best achieved with the use of appropriate standards and an objective calibration technique. We have developed a reliable method for calibrating the magnification of images from frozen-hydrated specimens. Invariant features in radial density plots of a standard are compared with the corresponding features in a "defocused" X-ray model of the same standard. Defocused X-ray models were generated to mimic the conditions of cryo-electron microscopy. The technique is demonstrated with polyoma virus, which was used as an internal standard to calibrate micrographs of bovine papilloma virus type 1 and bacteriophage phi X174. Calibrations of the micrographs were estimated to be accurate to 0.35%-0.5%. Accurate scaling of a three-dimensional structure allows additional calibrations to be made with radial density plots computed from two- or three-dimensional data.
Belnap
D M
DM
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.
Grochulski
W D
WD
Olson
N H
NH
Baker
T S
TS
D001435:Bacteriophages / Q000648:ultrastructure; D002138:Calibration / Q000592:standards; D015925:Cryopreservation; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008854:Microscopy, Electron / Q000379:methods*; D027383:Papillomaviridae / Q000648:ultrastructure; D027382:Polyomaviridae; D012015:Reference Standards