# Light-induced assembly and repeatable actuation in Ca2+-driven chemomechanical protein networks

## TL;DR

Researchers developed a light-controlled protein network that can rapidly assemble and contract, enabling precise control over soft materials for applications like synthetic cells and programmable biomaterials.

## Contribution

A novel light-controlled chemomechanical network using Tcb2 protein with repeatable actuation and optical control is introduced.

## Key findings

- Tcb2 networks exhibit dynamic self-assembly and contraction rates comparable to actomyosin systems.
- Optically triggered Ca2+ release enables precise growth and repeatable mechanical contractility.
- A reaction-diffusion and elastic model explains network dynamics and enables programmable actuation.

## Abstract

Programming rapid, repeatable motions in soft materials has remained a challenge in active matter and biomimetic design. Here, we present a light-controlled chemomechanical network based on Tetrahymena thermophila calcium-binding protein 2 (Tcb2), a Ca2+-sensitive contractile protein. These networks—driven by Ca2+-triggered structural rearrangements—exhibit dynamic self-assembly, spatiotemporal growth, and contraction rates comparable to actomyosin systems. By coupling light-sensitive chelators for optically triggered Ca2+ release, we achieve precise growth and repeatable mechanical contractility of Tcb2 networks, revealing emergent phenomena such as boundary-localized active regions and density gradient-driven reversals in motion. A coupled reaction-diffusion and elastic model explains these dynamics, highlighting the interplay between chemical network assembly and mechanical response. We further demonstrate active transport of particles via network-mediated forces in vitro and implement reinforcement learning to program seconds-scale spatiotemporal actuation in silico. These results establish a platform for designing responsive active materials with rapid chemomechanical dynamics and tunable optical control, with applications in synthetic cells, sub-cellular force generation, and programmable biomaterials.

Programming ultrafast, reversible motions at the micron scale in subcellular soft materials and active matter requires precise spatiotemporal control over molecular processes. Here, the authors investigate elastic cortical protein networks that assemble rapidly and demonstrate repeatable force generation that actuates using light-sensitive Ca2+ release.