Fig. 4.

The validity of the classification method is illustrated for F-actin formed from a mixture of unlabeled actin and TMR-labeled actin. Segments have been classified as being in one of four states based on cross-correlations with four different reference structures. These segments are then reconstructed by using the IHRSR approach (19), with a modified Holmes et al. model for F-actin (20) used as an initial reference. The modification involves changing the twist of this volume to 162° per subunit, and this initial reference volume is shown at the bottom left (iteration 1). After 60 cycles, the resulting reconstructions are shown for the four different sets. Because these reconstructions correspond quite well to the references used for purposes of classification but have been reconstructed using a very different structure as an initial model, the sorting is shown to be reliable.