Joining and scission in the self-assembly of nanotubes from DNA tiles.

We present the first direct observations of tile-based DNA self-assembly in solution using fluorescent nanotubes composed of a single tile. The nanotubes reach tens of microns in length by end-to-end joining rather than by sequential addition of single tiles. Their exponential length distributions withstand dilution but decay via scission upon heating, with an energy barrier Esc approximately 180kBT.

Design and characterization of programmable DNA nanotubes.

DNA self-assembly provides a programmable bottom-up approach for the synthesis of complex structures from nanoscale components. Although nanotubes are a fundamental form encountered in tile-based DNA self-assembly, the factors governing tube structure remain poorly understood. Here we report and characterize a new type of nanotube made from DNA double-crossover molecules (DAE-E tiles).

DNA electrophoresis in dilute polymer solutions: a nonbinary mechanism.

The dynamical behavior of the neutral polymer (dextran, M(w)=2 x 10(6)) is investigated during DNA electrophoresis in a dilute solution. Using a fluorescence recovery after photobleaching setup, we measured the velocity of fluorescein-labeled dextran induced by the migration of the DNA. We found that each DNA molecule drags a large number of dextrans with it.

Evidence that collagen fibrils in tendons are inhomogeneously structured in a tubelike manner.

The standard model for the structure of collagen in tendon is an ascending hierarchy of bundling. Collagen triple helices bundle into microfibrils, microfibrils bundle into subfibrils, and subfibrils bundle into fibrils, the basic structural unit of tendon. This model, developed primarily on the basis of x-ray diffraction results, is necessarily vague about the cross-sectional organization of fibrils and has led to the widespread assumption of laterally homogeneous closepacking.

Simultaneous measurements of the electrophoretic mobility, diffusion coefficient and orientation of dsDNA during electrophoresis in polymer solutions.

We determined simultaneously the electrophoretic mobility, diffusion coefficient D and molecular orientation during electrophoresis of dsDNAs in polymer solutions ranging from the dilute to the semidilute regime. We established, for the first time, master scaling laws for the diffusion coefficient showing a universal behavior. A model found in the literature designed for the dilute regime allows, surprisingly, to describe the mobility data over the whole range of concentrations studied and at the same time the biased reptation with fluctuations (BRF) failed for the semidilute regime, even when constraint release of the network was taken into account.