27 research outputs found
A Spectroscopic and Cryo-Transmission Electron Microscopy Study
The aggregation behaviour of the cationic pinacyanol chloride in aqueous
solution is investigated using absorption and linear dichroism spectroscopies,
optical microscopy and cryogenic transmission electron microscopy (cryo-TEM).
The investigations are focused on solutions in a concentration range from 50
μM up to 1 mM. At a concentration of 0.7 mM H-aggregates are detected that are
characterized by a broad absorption band centred at [similar]511 nm. The
aggregates possess a tubular architecture with a single-layer wall thickness
of [similar]2.5 nm and an outer diameter of [similar]6.5 nm. Linear dichroism
spectroscopy indicates that the molecules are packed with their long axis
parallel to the tube axis. These H-aggregates are not stable, but transform
into J-aggregates on the time scale of weeks. The kinetics of J-aggregation
depends on the dye concentration and the route of sample preparation, but can
also be enhanced by shear stress. J-aggregates possess a split absorption
spectrum composed of two longitudinally polarized J-bands and one H-band that
is polarized perpendicular to the aggregate axis. The J-aggregates are
[similar]9 nm wide and several micrometer long fibrils consisting of stacked
pairs of ribbons with a dumbbell-shaped density cross-section. Upon aging
these ribbons laterally stack face-to-face to form tape-like aggregates
Towards engineering of self-assembled nanostructures using non-ionic dendritic amphiphiles
Engineering nanostructures of defined size and morphology is a great challenge
in the field of self-assembly. Herein we report on the formation of
supramolecular nanostructures of defined morphologies with subtle structural
changes for a new series of dendritic amphiphiles. Subsequently, we studied
their application as nanocarriers for guest molecules
Cyanine Dye Coupling Mediates Self-assembly of a pH Sensitive Peptide into Novel 3D Architectures
Synthetic multichromophore systems are of great importance in artificial light harvesting devices, organic optoelectronics, tumor imaging and therapy. Here, we introduce a promising strategy for the construction of self-assembled peptide templated dye stacks based on coupling of a de novo designed pH sensitive peptide with a cyanine dye Cy5 at its N-terminus. Microscopic techniques, in particular cryogenic TEM (cryo-TEM) and cryo-electron tomography technique (cryo-ET), reveal two types of highly ordered three-dimensional assembly structures on the micrometer scale. Unbranched compact layered rods are observed at pH 7.4 and two-dimensional membrane-like assemblies at pH 3.4, both species displaying spectral features of H-aggregates. Molecular dynamics simulations reveal that the coupling of Cy5 moieties promotes the formation of both ultrastructures, whereas the protonation states of acidic and basic amino acid side chains dictates their ultimate three-dimensional organization