A statistical approach to computer processing of cryo-electron microscope images: virion classification and 3-D reconstruction.
The scattering density of the virus is represented as a truncated weighted sum of orthonormal basis functions in spherical coordinates, where the angular dependence of each basis function has icosahedral symmetry. A statistical model of the image formation process is proposed and the maximum likelihood estimation method computed by an expectation-maximization algorithm is used to estimate the weights in the sum and thereby compute a 3-D reconstruction of the virus particle. If multiple types of virus particle are represented in the boxed images then multiple 3-D reconstructions are computed simultaneously without first requiring that the type of particle shown in each boxed image be determined. Examples of the procedure are described for viruses with known structure: (1). 3-D reconstruction of Flockhouse Virus from experimental images, (2). 3-D reconstruction of the capsid of Nudaurelia Omega Capensis Virus from synthetic images, and (3). 3-D reconstruction of both the capsid and the procapsid of Nudaurelia Omega Capensis Virus from a mixture of unclassified synthetic images.
Yin
Zhye
Z
Purdue University, School of Electrical and Computer Engineering, 465 Northwestern Avenue, West Lafayette, IN 47907-2035, USA. zhye@ecn.purdue.edu
Zheng
Yili
Y
Doerschuk
Peter C
PC
Natarajan
Padmaja
P
Johnson
John E
JE
D000465:Algorithms; D002213:Capsid / Q000737:chemistry; D020285:Cryoelectron Microscopy / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016013:Likelihood Functions; D015233:Models, Statistical; D016011:Normal Distribution; D012328:RNA Viruses / Q000235:genetics; D012542:Scattering, Radiation; D014771:Virion / Q000737:chemistry*; D014965:X-Rays