Fig. 6

Effects of using a Gaussian circle as the starting reference for MLE optimization. The procedures shown in Fig. 5 were repeated with a Gaussian circle as the starting reference for all the data sets in the multi-reference MLE classification. The corresponding SNRs of the micrographs from which the particle sets were picked were 0.005 (a, b and c), 0.002 (d, e and f), 0.001 (g, h and i) and 0.0005 (j, k and l). The templates used for particle picking were: a Gaussian circle (a, d, g and j), one projection view of the influenza virus HA trimer (b, e, h and k), and one projection view of the HIV-1 Env trimer (c, f, i and l). In each panel, the five rows of image series correspond to five particle orientation classes generated by MLE, with the class averages of the milestone iterations (1st, 10th, 50th, 100th, 500th) shown in a row. At an SNR of 0.002 and above, the particle-picking template is not recapitulated by the MLE optimization when a Gaussian circle is used as the starting reference