Quantitative Zusammenhänge zwischen Chlorophyll-b-Reaktion, Elektronentransport und Phosphorylierung bei der Photosynthese

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Abstract
Carefully prepared spinach chloroplasts show the slow phase (half life 20 — 500 msec) of the absorption changes of Chlorophyll-b only. The decay of the absorption changes is an exponential one (fig. 1, fig. 5, eq. 1). The decay time as well as the electron transport rate are changed by coupling and uncoupling phosphorylation. A. By addition of the phosphorylation uncoupler methylamine hydrochloride the decay is accelerated up to ten times from 500 msec to 50 msec at pH = 7,4 and 20 °C (fig. 1, table 1). At the same time the electron transport rate measured by the reduction of ferricyanide increases ten times (table 1). Reciprocal decay time and electron transport rate are always proportional to each other (fig. 2, eq. 2). Phosphorylation uncouplers as carbonyl cyanide phenylhydrazone, atebrin, and dichlorphenol indophenol accelerate the decay of the Chl-b absorption changes as well (fig. 3). B. Phosphorylation accelerates the decay time of the Chl-b absorption changes up to two times from 90 to 40 msec at pH=8,4 and 20 °C (fig. 4, fig. 5, table 2). At the same time the electron transport rate too increases two times, thus reciprocal decay time and electron transport rate are proportional to each other again (fig. 6, table 2). The same result is obtained when phosphorylation is suppressed by omission of phosphate or addition of phlorizin (fig. 6, fig. 7 top). It is shown that the phosphorylation rate is identical with the extra electron transport rate stimulated by phosphorylation as measured by IZAWA et al. 18 (fig. 7 bottom). At the same time it is shown that phosphorylation is proportional to the change in the reciprocal decay time of the Chl-b absorption changes (fig. 7 bottom, eq. 3). JUNGE and WITT 3 show that the slow phase of the Chl-b absorption changes are connected with the translocation of protons across the thylakoid membrane. In connection with those results phosphorylation is coupled to an additional proton transfer. The foregoing results are discussed in this respect in 1. c. 3. The results are in part reviewed in *.

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