1 research outputs found
Nanotubes of Biomimetic Supramolecules Constructed by Synthetic Metal Chlorophyll Derivatives
Various
supramolecular nanotubes have recently been built up by lipids, peptides,
and other organic molecules. Major light-harvesting (LH) antenna systems
in a filamentous anoxygenic phototroph, <i>Chloroflexus</i> (<i>Cfl.</i>) <i>aurantiacus</i>, are called
chlorosomes and contain photofunctional single-wall supramolecular
nanotubes with approximately 5 nm in their diameter. Chlorosomal supramolecular
nanotubes of <i>Cfl. aurantiacus</i> are constructed by
a large amount of bacteriochlorophyll(BChl)-<i>c</i> molecules.
Such a pigment self-assembles in a chlorosome without any assistance
from the peptides, which is in sharp contrast to the other natural
photosynthetic LH antennas. To mimic chlorosomal supramolecular nanotubes,
synthetic models were prepared by the modification of naturally occurring
chlorophyll(Chl)-<i>a</i> molecule. Metal complexes (magnesium,
zinc, and cadmium) of the Chl derivative were synthesized as models
of natural chlorosomal BChls. These metal Chl derivatives self-assembled
in hydrophobic environments, and their supramolecules were analyzed
by spectroscopic and microscopic techniques. Cryo-transmission electron
microscopic images showed that the zinc and cadmium Chl derivatives
could form single-wall supramolecular nanotubes and their outer and
inner diameters were approximately 5 and 3 nm, respectively. Atomic
force microscopic images suggested that the magnesium Chl derivative
formed similar nanotubes to those of the corresponding zinc and cadmium
complexes. Three chlorosomal single-wall supramolecular nanotubes
of the metal Chl derivatives were prepared in the solid state and
would be useful as photofunctional materials