The diffusion of plastoquinol and its binding to the cytochrome bf complex, which occurs during linear photosynthetic electron transport and is analogous to reaction sequences found in most energy-converting membranes, has been studied in intact thylakoid membranes. The flash-induced electron transfer between the laterally separated photosystems II and photosystems I was measured by following the sigmoidal reduction kinetics of P-700(+) after previous oxidation of the intersystem electron carriers. The amount of flash-induced plastoquinol produced at photosystem II was (a) reduced by inhibition with dichlorophenyl-dimethylurea and (b) increased by giving a second saturating flash. These signals were simulated by a new model which combines a deterministic simulation of reaction kinetics with a Monte Carlo approach to the diffusion of plastoquinol, taking into account the known structural features of the thylakoid membrane. The plastoquinol molecules were assumed to be oxidized by either a diffusion-limited or a nondiffusion-limited step in a collisional mechanism or after binding to the cytochrome bf complex. The model was able to account for the experimental observations with a nondiffusion-limited collisional mechanism or with a binding mechanism, giving minimum values for the diffusion coefficient of plastoquinol of 2 x 10(-8) cm(2)s(-1) and 3 x 10(-7) cm(2)s(-1), respectively.
Are the distributional effects of environmental measures just?
Answers this question, to do which we normally use the segregation
argument: poor people live in highly polluted areas, therefore
environmental measures which reduce the pollution must be socially just.
Argues that the environment is neither a public good nor a local public
good, as is often assumed. The crucial point for distribution analysis
is the reaction of the markets and by no means the geographical
segregation of income classes. Environmental prices skim off the benefit
of environmental measures and can lead to an unjust redistribution.
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