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Research Theme: Dynamic Biomolecular Self-Assembly

The structure and function of biological macromolecules is sensitive to the local ionic strength, pH, temperature and electrostatic environment. In particular, we are interested in the use of local electric fields to influence the structure and function of proteins and nucleic acids in the vicinity of an electrode. In the limit of ideally polarizable electrodes, there is minimal Faradaic current, but extremely high local ion concentrations and electric field gradients. These conditions allow for highly localized spatial and temporal control of molecular mechanisms without the use of redox chemistry, which may allow for direct integration into a broader array of biochemical processes.

We have recently demonstrated this approach for the electronically activated polymerization of the cytoskeletal protein actin. This protein has no redox activity, but can be switched to an activated state through the binding of Mg²⁺ at an active site. The application of a low-frequency AC voltage can be used to both activate actin monomers and to enhance its nucleation into oligomers and actin filaments. Moreover, the highly localized electrostatic conditions at the electrode surface drive the formation of unprecedented nematic architectures that have not been observed in bulk systems.

F-Actin polymerizes at the edges of two electrodes spaced 10 um apart during a 100 Hz, 5 Vpp square-wave bias. Actin filaments parallel to the electrodes are first observed at 60 s, subsequently increasing in intensity and width.

Visible actin bundles stacked with nematic ordering after 180 min with the addition of 5 uM a-actinin.

Related Publications:

Directed Hybridization and Melting of DNA Linkers using Counterion-Screened Electric Fields.
Ian Y. Wong and Nicholas A. Melosh. Nano Letters (in press)

Electronically Activated Actin Protein Polymerization and Alignment.
Ian Y. Wong, Matthew J. Footer and Nicholas A. Melosh. Journal of the American Chemical Society. 130(25), 7908 (2008)