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. Author manuscript; available in PMC: 2016 Apr 23.
Published in final edited form as: Cell. 2015 Apr 23;161(3):438–449. doi: 10.1016/j.cell.2015.03.050

Figure 1. The Steps Involved in Structure Determination by Single-Particle Cryo-EM.

Figure 1

A single-particle project should start with a characterization of the specimen in negative stain (left arm of the workflow). Only once the EM images, or potentially 2D class averages, are satisfactory, i.e., the particles are mono-disperse and show little aggregation and a manageable degree of heterogeneity (“low-resolution” sample refinement), is the sample ready for analysis by cryo-EM (right arm of the workflow). The images, 2D class averages and 3D maps obtained with vitrified specimens may indicate that the sample requires further improvement to reach near-atomic resolution (“high-resolution” sample refinement).