Biomedical Engineering Reference
In-Depth Information
the apparent dielectric constant in the vicinity of the donor
and acceptor sites of the probe, and the calculated resonance integral,
allowed the constraction of an energetic diagram of photoreduction (Fig. 6.6).
Charge photoseparation can be performed with the use of artificial lipid membranes
known as vesicles (Shilov, 1997; and references therein). This approach can be
illustrated by a system in which the irreversible electron donor (D, EDTA) and
photosensitizer
were incorporated into the inner water pool of lipid
vesicles. The first acceptor (A
1
octadecyl viologen) was placed in the vesicular wall,
while the second electron acceptor
,
was placed in the bulk solution. The quantum
yield of the electron transfer from D to
via the excited S* and
was found to be 0.1
-
0.3 under conditions of steady state photolysis. Processes of conversion of exitation
energy to electrochemical potential energy in the form of transmembrane charge
separation, the utilization of this energy for proton transfer across the membrane and the
synthis of ATP have been chemically mimicked in artificial membranes (Gust et al.,
1999). Artificial systems of supermolecules, prepared from porphyrins and other
chromophores, electron donors and acceptors, were vectorially inserted into the lipid
bilayers of liposomes, where they function as constituents of transmembrane light-driven
proton pumps. The proton motive force thus produced can be used to synthesize ATP via
catalysis by
synthase isolated from chloroplasts.
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