With C60 being used to define the molecule's geometry, a globular amphiphile with 10 alkyl chains which forms a variety of lamellar aggregates can be prepared. Vesicles (see picture), as well as cylindrical micelles and single molecules of this artificial lipid, can be detected by TEM investigations.
Two dendritic fullerene (DF) monoadducts, 2 and 3, which can carry up to 9 and 18 negative charges, respectively, were examined with respect to electrostatic complexation with Cytochrome c (Cytc). To facilitate comprehensive photophysical investigations, the zinc analogue of Cytc (ZnCytc) was prepared according to a novel, modified procedure. The association of ZnCytc and DF, and consequential photoinduced electron transfer within ZnCytc-DF from the photoexcited protein to the fullerene, was proven by fluorescence spectroscopy and transient absorption spectroscopy. These findings were also supported by circular dichroism as well as by extensive molecular dynamics (MD) simulations.
Monolayers at the air/water interface of a new amphiphilic molecule derived from a C60-fullerene were
studied at different lateral pressures by a combination of film balance techniques, neutron reflection (NR),
and infrared reflection−absorption spectroscopy (IRRAS). The amphiphilic fullerene derivative (AF) consisted
of a dendrimeric hydrophilic region, and 10 alkyl chains covalently attached to the fullerene cage formed
the hydrophobic part. The AF monolayers could be compressed and expanded without significant hysteresis
and the alkyl chains remained fluid at all pressures. By a titration series, the pK value of the AF monolayer
was determined as 7.5 and pH dependent measurements allowed a variation of the negative AF headgroup
charge by about 18 charges. The thickness of the AF monolayer at high lateral pressure was 30 Å, thus
similar to that of typical phospholipid monolayers in the condensed state. In contrast, the AF molecular
area was about 6-fold higher than that of phospholipids at high pressure. Moreover, the hydration capacity
of the AF headgroup is significantly higher than that of phospholipids. The negatively charged AF monolayer
showed a strong coupling of the water-soluble protein cytochrome c from the subphase, leading to the
formation of a 30 Å thick protein layer underneath the AF layer. The protein content of this layer varied
drastically with the pH value. The properties of the AF monolayers may be useful in the design of dedicated
biomimetic surfaces.
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