Using single-molecule DNA nanomanipulation, we show that abortive initiation involves DNA "scrunching"--in which RNA polymerase (RNAP) remains stationary and unwinds and pulls downstream DNA into itself--and that scrunching requires RNA synthesis and depends on RNA length. We show further that promoter escape involves scrunching, and that scrunching occurs in most or all instances of promoter e...

The trajectories of differently shaped nanoparticles manipulated by atomic force microscopy are related to the scan path of the probing tip. The direction of motion of the nanoparticles is essentially fixed by the distance b between consecutive scan lines. Well-defined formulas are obtained in the case of rigid nanospheres and nanowires. Numeric results are provided for symmetric nanostars. As ...

Molecular modelling with Jumna is used to study extreme stretching of the DNA double helix. The results, which correlate well with recent nanomanipulation experiments, show how the double helix can be extended to twice its normal length before its base pairs break. Depending on the way the duplex is stretched two types of conformation can occur, either an unwound flat ribbon or a narrow fibre w...

Manipulation of nanoparticles with the scanning force microscope (SFM) has been limited until now to clearing areas on a surface or to moving single particles sequentially to create two-dimensional patterns. The research reported here uses a previously described setup for nanomanipulation with the SFM to (i) build a simple three-dimensional pyramidal structure by pushing a nanoparticle on top o...

We study the local-field enhancement in a nanocavity created by optical nanomanipulation. Recently we showed that a metallic probe can modify the optical force experienced by a metallic particle and generate a material selective trapping potential. We show that the same configuration used for optical forces can be used to control both in magnitude and tune the local-field enhancement around the...

Haptic feedback for microand nanomanipulation is a research area of growing importance with many potential applications in microand biotechnology. Past research often involves the coupling of atomic force microscopes to haptic devices, but the results are not satisfactory. We propose to adopt a different approach, which consists of contactless manipulation, in particular by using optical tweeze...

We put forward the quantum screening effect in field emission [FE] nanodiodes, explaining relatively low field enhancement factors due to the increased potential barrier that impedes the electron Fowler-Nordheim tunneling, which is usually observed in nanoscale FE experiments. We illustratively show this effect from the energy band diagram and experimentally verify it by performing the nanomani...

The authors report the direct observation of a single asperity tungsten tip sliding on graphite by in situ transmission electron microscopy TEM nanomanipulation. The in situ TEM studies have confirmed that graphitic flakes transfer to a sliding tungsten probe, validating proposed friction mechanisms explaining the unique tribological properties of graphite. Wear of graphite was observed, typica...