0000000000113941
AUTHOR
Monika Schönhoff
Incorporation of membrane proteins into lipid surface monolayers: Characterization by fluorescence and electron microscopies
The preparation of oriented protein samples is an attractive goal, e.g., to gain more detailed information from spectroscopic experiments. Our approach towards this aim was to prepare monolayers of phospholipids at the air-water interface and to incorporate the proteins into these ordered structures. Subsequently, we used the Langmuir-Boldgett (LB) transfer technique to obtain samples of oriented proteins on solid supports. — Incorporation was achieved by spreading the proteins from a detergent solution onto a prespread lipid monolayer on the water surface. We characterized successful incorporation by in situ fluoresence microscopy and by electron microscopy, and investigated the topology o…
Photoinduced optical anisotropy in organic molecular films controlled by an electric field
Abstract The photoinduced reorientation of dye molecules in molecular films on solid substrates has been controlled with external dc electric fields, leading to solid state structures, which are macroscopically polar, temporally stable at room temperature, and well-defined at the molecular level. A simulation based on the excitation-driven rotational diffusion of the molecules in the potential of their neighbors yielded a realistic model and indicated a collective character of the process. This shows that we are close to a quantitative comprehension of the molecular interactions within these films.
Photoelectropoling of azobenzene chromophores in molecular films
The photoinduced reorientation and photoelectropoling processes were investigated in molecular films of aliphatically substituted azobenzenes. While polarized illumination leads to a conversion of isotropic samples into anisotropic ones, upon application of external electric fields even macroscopically polar materials are created. The macroscopic polarity can be reversed under suitable experimental conditions. Order parameters as a function of the poling field were determined by Stark spectroscopy. Using atomic force microscopy it is shown that the structure of the sample is well defined on a microscopic length scale, whereas on a macroscopic length scale it is not.
Steric Constraints Induced Frustrated Growth of Supramolecular Nanorods in Water.
A unique example of supramolecular polymerisation in water based on monomers with nanomolar affinities, which yield rod-like materials with extraordinarily high thermodynamic stability, yet of finite length, is reported. A small library of charge-neutral dendritic peptide amphiphiles was prepared, with a branched nonaphenylalanine-based core that was conjugated to hydrophilic dendrons of variable steric demand. Below a critical size of the dendron, the monomers assemble into nanorod-like polymers, whereas for larger dendritic side chains frustrated growth into near isotropic particles is observed. The supramolecular morphologies observed by electron microscopy, X-ray scattering and diffusio…
Kinetic control in the temperature-dependent sequential growth of surface-confined supramolecular copolymers
We report the sequential growth of supramolecular copolymers on gold surfaces, using oppositely charged dendritic peptide amphiphiles. By including water-solubilising thermoresponsive chains in the monomer design, we observed non-linear effects in the temperature-dependent sequential growth. The step-wise copolymerisation process is characterised using temperature dependent SPR and QCM-D measurements. At higher temperatures, dehydration of peripheral oligoethylene glycol chains supports copolymer growth due to more favourable comonomer interactions. Both monomers incorporate methionine amino acids but remarkably, desorption of the copolymers via competing sulphur gold interactions with the …