transition temperature (Fig. 3D). Interestingly, some nanostructures that are recorded at very early stages of the selfaggregation are seen in this sample, too. In addition, we have observed very large fibrillar aggregates (on the scale of hundreds of micrometers) in this system at 62 C by digital light microscopy (data not shown).
Various other systems are known to produce tubes. [5,6] For instance, in a similar dimension range, b-amyloid peptides can assemble into tubes with a 52 nm diameter [7] formed by fused helical ribbons with a positively charged bilayer wall. SLC nanotubes are formed by single-walled helical ribbons and are negatively charged. They are generated from a very simple and common natural bile salt and can be processed through shear-sensitive suspensions, and thus can also offer an interesting alternative scaffold for nanotechnology applications.
The present study shows the complexity of the mechanisms involved in SLC tube formation. Coaxial cylinders, helical ribbons, fibrils, and single-walled tubes are found to coexist in the first stage of the kinetics. The thermal stability of the tubular structures is remarkable. However, above a certain temperature they disintegrate and form nanostructures quite similar to those existing in the very early stages of self-aggregation. Further studies are under way to investigate the structure and dynamics of the monomolecular wall that is responsible for such stability, and the effect of counterions on self-aggregation in these systems.