Biomedical Engineering Reference
In-Depth Information
a proton-motive force. On accumulation of suffi cient proton-motive force, protons
fl ow through the F
0
F
1
-ATP synthase, with the formation of ATP from ADP and P
i
(see Sect.
2.1
).
The above-described system is the fi rst complete biomimetic one which effec-
tively couples electrical potential derived from photoinduced electron transfer to the
chemical potential associated with the ADP-ATP conversion, thereby mimicking
the entire process of bacterial photosynthesis. It constitutes a synthetic biological
motor that, in principle, can be used to power anything which requires a proton
gradient or ATP to work, or even future nanomachines. It might also be advanta-
geous to use artifi cial, light-driven systems to produce ATP in order to carry out
enzymatic reactions in the absence of interfering biological materials and without
the need of living cells (Gust et al.
2001
) .
4.2
A Hybrid Nanomechanical Device Powered by ATP Synthase
An interesting nanomechanical device was obtained by coupling nanofabrication
techniques with biochemical engineering of a motor protein (Soong et al.
2000
) .
Such nanomechanical device consists of three elements, namely: nanofabricated
substrates of nickel posts, each 50-120 nm in diameter and 200-nm high; F
1
-ATP
synthase molecules, specifi cally modifi ed for selective interface with the nano-
fabricated structures, nanofabricated Ni rods (150 nm in diameter and 750-1,500-
nm long). The F
1
-ATP synthase molecules were attached to the Ni
2+
of partially
oxidized Ni posts using histidine tags introduced into the b -subunits (Bachand
et al.
2001
). Streptavidin was bound to the biotin residue on the g-subunit tip, and
the Ni nanorods, coated with biotinylated histidine-rich peptides, were then
attached to the substrate-mounted F
1
-ATP synthase motors through a biotin-
streptavidin linkage. Rotation of the nanopropellers, which was observed in a
fl ow cell with a CCD camera, was initiated by addition of ATP and inactivated by
addition of NaN
3
, an F
1
-ATP synthase inhibitor. Although only 5 of 400 total
observed propellers were found to rotate probably because of incorrect assembly
of the components, these experiments demonstrate the possibility to integrate
biomolecular motors with nanoengineered systems to produce nano- or micro-
mechanical machines. From a chemical point of view, however, it should be
noted that this device, unlike that described in Sect.
4.1
, does not contain any
artifi cial active component.
5
Conclusion and Perspectives
The results described here show that, by taking advantage of careful incremental
design strategies of the tools of modern synthetic chemistry, of the paradigms of
supramolecular chemistry, as well as of inspiration by natural systems, it is possible
