Atomic force microscopy reconstruction of G-wire DNAa)

A fundamental problem in atomic force microscopy (AFM) image interpretation is distinguishing features arising from tip geometry from true molecular detail. In this study, a novel 4-stranded form of DNA (the ‘‘G wire’’) was coadsorbed with 7.6-nm-diam colloidal gold probe calibration standards and examined by AFM. After the probe apices were reconstructed from AFM images of the standards, the artificial broadening of the coadsorbed G-wire DNA was removed, resulting in more reliable image interpretation. Using simple geometric models, a favorable comparison between observed and modeled G-wire cross sections suggests that reconstructions removed about 25% of the tip-broadened AFM image in these studies.