Motion Capture and Manipulation of a Single Synthetic Molecular Rotor by Optical Microscopy.

Angewandte Chemie (International ed. in English)

PubMedID: 24989127

Ikeda T, Tsukahara T, Iino R, Takeuchi M, Noji H. Motion Capture and Manipulation of a Single Synthetic Molecular Rotor by Optical Microscopy. Angew Chem Int Ed Engl. 2014;.
Single-molecule imaging and manipulation with optical microscopy have become essential methods for studying biomolecular machines; however, only few efforts have been directed towards synthetic molecular machines. Single-molecule optical microscopy was now applied to a synthetic molecular rotor, a double-decker porphyrin (DD). By attaching a magnetic bead (ca. 200 nm) to the DD, its rotational dynamics were captured with a time resolution of 0.5 ms. DD showed rotational diffusion with 90° steps, which is consistent with its four-fold structural symmetry. Kinetic analysis revealed the first-order kinetics of the 90° step with a rate constant of 2.8 s(-1) . The barrier height of the rotational potential was estimated to be greater than 7.4 kJ?mol(-1) at 298 K. The DD was also forcibly rotated with magnetic tweezers, and again, four stable pausing angles that are separated by 90° were observed. These results demonstrate the potency of single-molecule optical microscopy for the elucidation of elementary properties of synthetic molecular machines.