CO₂-switchable response of protein microtubules: Behaviour and mechanism

Recently, we proposed a small molecular "inducing ligand" strategy to assemble proteins into highly-ordered structures via dual non-covalent interactions, i.e. carbohydrate-protein interaction and dimerization of Rhodamine B. Using this approach, artificial protein microtubules were successfully constructed. In this study, we find that these microtubules exhibit a perfect CO₂ responsiveness; assembly and disassembly of these microtubules were nicely controlled by the alternative passage of CO₂ and N₂. Upon the injection of CO₂, a negative net-charged SBA turns into a neutral or positive net-charged SBA, which elongated, to some extent, the effective distance between SBA and Rhodamine B, resulting in the disassociation of the Rhodamine B dimer. Further experimental and simulation results reveal that the CO₂-responsive mechanism differs from that of solubility change of the previously reported CO₂-responsive synthetic materials.