title: Peptide adsorption to cyanine dye aggregates revealed by cryo-transmission electron microscopy.
abstract: The binding interaction between aggregates of the 5-chloro-2-[[5-chloro-3-(3-sulfopropyl)-3H-benzothiazol-2-ylidene]methyl]-3-(3-sulfopropyl)benzothiazolium hydroxide inner salt ammonium salt (CD-1) and alpha-helix, as well as beta-sheet forming de novo designed peptides, was investigated by absorption spectroscopy, circular dichroism spectroscopy, and cryogenic transmission electron microscopy. Both pure dye and pure peptides self-assembled into well-defined supramolecular assemblies in acetate buffer at pH = 4. The dye formed sheetlike and tubular H- and J-aggregates and the peptides alpha-helical coiled-coil assemblies or beta-sheet rich fibrils. After mixing dye and peptide solutions, tubular aggregates with an unusual ultrastructure were found, most likely due to the decoration of dye tubes with monolayers of peptide assemblies based on the strong electrostatic attraction between the oppositely charged species. There was neither indication of a transfer of chirality from the peptides to the dye aggregates nor the opposite effect of a structural transfer from dye aggregates onto the peptides secondary structure.
authors.affiliation: Forschungszentrum für Elektronenmikroskopie, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstrasse 36 a, D-14195 Berlin, Germany. berlepsc@chemie.fu-berlin.de
authors.forename: Hans
authors.initials: H
authors.lastname: von Berlepsch
authors.forename: Enrico
authors.initials: E
authors.lastname: Brandenburg
authors.forename: Beate
authors.initials: B
authors.lastname: Koksch
authors.forename: Christoph
authors.initials: C
authors.lastname: Böttcher
mesh_terms: D000327:Adsorption; D002232:Carbocyanines / Q000737:chemistry*; D002942:Circular Dichroism; D004396:Coloring Agents / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D046529:Microscopy, Electron, Transmission; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D002232:Carbocyanines; D004396:Coloring Agents; D010455:Peptides