A Weighted Voting Algorithm for Detecting Reliable Common Lines in Single Particle Cryo-EM

The single-particle reconstruction of cryo-electron microscopy is an important technique to recover the three-dimensional structure of biological macromolecules from their two-dimensional noisy projection images taken from unknown random directions. Angular reconstruction is a basic algorithm for reference free ab-initio estimation of the initial three-dimensional structure of molecules, in which the relative orientation of the particle is uniquely determined from the common lines among three projection images. However, it is difficult to detect reliable common lines due to the low signal-to-noise ratio of the projection images. In this paper, a weighted voting algorithm is proposed to detect the reliable common lines, in which the iterative improvement technique is employed. The reliability of each common line is estimated by the consistency between the voted angle and projection angle computed using the common line during the iteration. Finally, the reliable common line pairs are retained, and the spurious ones are eliminated through the binary weight correction and iterative improvement. The proposed algorithm is successfully applied to the reconstruction of the Escherichia coli 50S ribosomal subunit. Experimental results show that the proposed algorithm can improve the estimation accuracy from noisy projection images.