The dynamics can also be analyzed for less abundant β -sheet features. In filaments and weakly bundled networks, there is an initial decrease in CLS within 0.5 ps and then a plateau at 0.4 (Figure ). Upon strongly bundled network formation, the lineshape does not exhibit changes throughout the entire measurement (Figure and Supplementary Table ), indicating that the β -sheet structure is "locked" with very little solvent exposure in the surroundings. Such finding demonstrates that the β -sheet structure is mostly shielded from the solvent, especially in strongly bundled network, and therefore very likely to distribute in the "buried" sites of actin networks. The interesting change in the dynamics of β -sheet provides great insight into its role in the mechanical and biochemical functions of actin bundles.