Spinning Top-like Nanoprobes for Direct Visualization of Cooperative Ca2+-Binding-Induced Conformational Switching in Single Calmodulin Molecules

ions to the C-terminal domain, supported by a Hill coefficient of 1.81 and a binding stoichiometry of 2.43. This platform provides an approach for quantifying protein-ligand interactions and conformational kinetics at the single-molecule level, offering new insights into calcium-mediated signaling and dynamic protein function.