Table III.

Effect of acetic anhydride treatment on proton uptake in pea thylakoids in the presence and absence of HEM

Thylakoid Sample Used	Extent of H+ Uptake		Increase
	−HEM	+HEM
	nmol H+ (mg Chl)−1
Experiment 1
Glycylglycine-quenched control-reduced light	126 ± 12	220 ± 12	94
3.5 mm Anhydride-treated	91 ± 26	121 ± 14	30
Experiment 2
Glycylglycine-quenched control-reduced light	185 ± 15	312 ± 39	127
3.5 mm Anhydride-treated	165 ± 4	193 ± 11	28
Thylakoids illuminated during acetic anhydride treatment
Glycylglycine-quenched control	141 ± 8	310 ± 40	169
3.5 mm Anhydride-treated	111 ± 11	228 ± 21	117

Acetic anhydride modification and proton uptake measurements were performed as described in “Materials and Methods.” Electron transport in the anhydride-treated thylakoids was driven by saturating white light. To obtain electron transport at the same level as in the anhydride-treated thylakoids, the light intensity for the control case was reduced to give rates close to those of the anhydride-treated samples. n = 3 (all cases). Experiment 1. The extent of proton uptake was measured on the same sets of thylakoids used for determination of the electron transport rates shown in Table II. Experiment 2. Thylakoids for this experiment were isolated and treated with anhydride on a different day than in experiment 1. For the “light protection” experiment the acetic anhydride and the control (glycylglycine added before the anhydride) treatments were illuminated 30 s prior to adding the reagents with 0.5 mm methyl viologen present to activate electron transport. Illumination continued during the 30-s treatment period. n = 3 (in all cases).