MFP-3D? offline section analysis software offers the capability to outline the contours of individual molecules, using its "Freehand" option, and measure their lengths. pUC19 DNA is a 2686 base-pair (bp) molecule. Assuming each bp is 3.4 angstrom, this molecule should be approximately 913 nm long. The included table shows measured lengths and their calculated variance. AC in fluid, 2 µm scan.