Abstract

We recently developed a field free technique to trap and measure the electrical charge of single molecules in solution with sub-elementary charge precision. Such measurements open doors to a host of high precision measurement and detection problems in biophysics and soft matter. One problem that we have been interested in from the start concerns the relationship between the 3D structure of a charged molecule and its “electrostatic fingerprint” in the far field. Here I will talk about how high precision measurements of molecular effective charge in solution enable us to glean information on molecular 3D structure and conformation in solution. Using DNA origami we are able to measure differences in molecular topology rapidly and with high precision, and to readily distinguish molecular isoforms that carry identical amounts of structural charge. Taking the measurement further, we have demonstrated the ability to measure the rise per basepair and radius of different forms of the double helix with up to sub-Angstrom precision, traditionally attained using techniques such as x-ray crystallography, and NMR in the solution phase.