Single-Molecule Trapping and Measurement in a Nanostructured Lipid Bilayer System.

The repulsive electrostatic force between a biomolecule and a like-charged surface can be geometrically tailored to create spatial traps for charged molecules in solution. Using a parallel-plate system composed of silicon dioxide surfaces, we recently demonstrated single-molecule trapping and high precision molecular charge measurements in a nanostructured free energy landscape. Here we show that surfaces coated with charged lipid bilayers provide a system with tunable surface properties for molecular electrometry experiments.

Opto-Electrostatic Determination of Nucleic Acid Double-Helix Dimensions and the Structure of the Molecule-Solvent Interface.

A DNA molecule is highly electrically charged in solution. The electrical potential at the molecular surface is known to vary strongly with the local geometry of the double helix and plays a pivotal role in DNA-protein interactions. Further out from the molecular surface, the electrical field propagating into the surrounding electrolyte bears fingerprints of the three-dimensional arrangement of the charged atoms in the molecule.

Electroviscous effect for a confined nanosphere in solution.

A charged colloidal particle suspended in an electrolyte experiences electroviscous stresses arising from motion-driven electrohydrodynamic phenomena. Under certain conditions, the additional contribution from electroviscous drag forces to the total drag experienced by the moving particle can lead to measurable deviations of particle diffusion coefficients from values predicted by the well known Stokes-Einstein relation that describes diffusive behavior of small particles in an unbounded charge-free fluid. In this study, we investigate the role of electroviscous stresses on nanoparticle diffusion in confined geometries using both simulations and experiment.

Single-molecule trapping and measurement in solution.

Trapping of a single molecule in the fluid phase was realized decades following developments in the gas-phase, because in some ways the solution phase posed a greater challenge. The key issues have since been addressed by several different means; techniques to confine nanometer scale entities in solution now abound and are gaining traction in a variety of single molecule studies. Available methods range from pure physical entrapment of a molecule on the one hand to electrokinetic and optical techniques, and approaches that exploit thermodynamic principles on the other.