Modeling Beta-Traces for Beta-Barrels from Cryo-EM Density Maps.

Cryo-electron microscopy (cryo-EM) has produced density maps of various resolutions. Although -helices can be detected from density maps at 5-8 Å resolutions, -strands are challenging to detect at such density maps due to close-spacing of -strands. The variety of shapes of -sheets adds the complexity of -strands detection from density maps. We propose a new approach to model traces of -strands for -barrel density regions that are extracted from cryo-EM density maps. In the test containing eight -barrels extracted from experimental cryo-EM density maps at 5.5 Å-8.25 Å resolution, detected about 74.26% of the amino acids in the -strands with an overall 2.05 Å 2-way distance between the detected -traces and the observed ones, if the best of the fifteen detection cases is considered.