Biomedical Engineering Reference
In-Depth Information
stabilize it during device fabrication. Secondly, we examined the stability of
PS-I by testing its fluorescence after attaching the detergent-protein complex
to a glass slide [53, 54]. The intact PS-I emits red light with a characteristic
peak wavelength as it degrades. This peak subsides and is replaced by another
bluer peak. Even the two best standard surfactants did poorly at maintaining
the red peak. In contrast, the spectrum after A6K extraction was almost a per-
fect match for the normal one, indicating the complex was largely intact after
drying. Furthermore, the complex appeared to remain stable for up to three
weeks on the glass slide. PS-I itself remains to be fully characterized, and this
stabilization technique offers new means to explore its properties [98].
In addition, photosynthetic complexes are archetypal molecular electronic
devices, containing molecular optical and electronic circuitry organized by
a protein scaffold. Conventional technology cannot equal the density of the
molecular circuitry found in photosynthetic complexes. Thus, if integrated
with solid-state electronics, photosynthetic complexes might offer an attrac-
tive architecture for future generations of circuitry where molecular compo-
nents are organized by a macromolecular scaffold. For utilization in practical
technological devices they must be stabilized and integrated with solid-state
electronics. Our results suggest that photosynthetic complexes may be used
as an interfacial material in photovoltaic devices. Evolved within a thin mem-
brane interface, photosynthetic complexes sustain large open circuit voltages
of 1.1 V without significant electron-hole recombination, and they may be
self-assembled into an insulating membrane, further reducing recombina-
tion losses. Peptide surfactants have been shown to stabilize these complexes
during and after device fabrication. It is expected that the power conversion
efficiency of a peptide-stabilized solid-state photosynthetic device may ap-
proach or exceed 20%. Similar integration techniques may apply to other
biological or synthetic protein-molecular complexes [99].
These simply designed peptide detergents may now open a new avenue to
overcome one of the biggest challenges in biology—to obtain large number
of high resolution structures of membrane proteins. Study of the membrane
proteins will not only enrich and deepen our knowledge of how cells com-
municate with their surroundings since all living systems respond to their
environments, but these membrane proteins can also be used to fabricate
the most advanced molecular devices, from energy harnessing devices to ex-
tremely sensitive sensors and medical detection devices.
4.2
Tissue Engineering
A new type of self-assembling peptide nano-fibril that serves as a substrate
for neurite outgrowth and synapse formation is described (Fig. 8). The self-
assembling peptide scaffolds are formed through the spontaneous assembly
of ionic self-complementary
β
-sheet peptides under physiological conditions,
