Table I.
Acetic anhydride inhibition of PSII-dependent ferricyanide reduction in spinach thylakoids
| Thylakoid Sample Used | Whole-Chain Electron Transport Rate
|
|
|---|---|---|
| Basal | Uncoupled | |
| μeq (mg Chl h)−1 | ||
| Untreated thylakoidsa | 192 | 630 (100%) |
| Glycylglycine-quenched controlb | 113 | 228 (36%) |
| Acetic anhydride-treatedc | 29 | 28 (4%) |
See “Materials and Methods” for the treatment reaction conditions and for the electron transport assay. Saturating light intensity was used (the same intensity for all assays). Nigericin (40 μm) was added to uncouple electron transport after a 1-min light exposure, followed by an additional 1 min of illumination. The numbers in parentheses are the percentages of the uncoupled, untreated control rates.
Untreated thylakoids were the stock suspension, after isolation, from which aliquots were taken for the glycylglycine-quenched and acetic anhydride treatments.
Glycylglycine was added before the acetic anhydride to quench the anhydride before appreciable reaction occurred with thylakoid reactive groups.
The anhydride was added to the thylakoids for the specified reaction time (compare with “Materials and Methods”) followed by the glycylglycine quench.