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. 2008 Sep 19;95(12):5843–5850. doi: 10.1529/biophysj.108.136879

FIGURE 2.

FIGURE 2

Difference FT-IR spectra showing flash-induced perturbation of the azide antisymmetric stretching band in untreated, manganese-depleted, or chloride-depleted PSII samples. Difference spectra were created by ratio of data taken before and after flash excitation, followed by conversion to absorbance. In A–E, the results of three consecutive 532 nm laser flashes to a preflashed, dark-adapted PSII sample are presented in red (flash 1), green (flash 2), and blue (flash 3). In A, untreated PSII contained 400 mM sucrose, 50 mM MES-NaOH, pH 6.0, and 15 mM NaCl (average of 12). In B, untreated PSII contained in 400 mM sucrose, 50 mM HEPES-NaOH, pH 7.5 (pH 7.5 buffer) (average of 15). In C, manganese-depleted PSII contained pH 7.5 buffer (average of 38). In D and E, chloride-depleted PSII contained pH 7.5 buffer (average of 39). In A-D, the sample also contained 15 mM Inline graphic In E, chloride-depleted PSII in pH 7.5 buffer contained 15 mM [15N(14N)2]− (average of 21). In F, a dark-minus-dark control was generated from the data set in D. Delta absorbance on the y axis indicates that the spectra show changes in absorbance. All samples contained 1.5 mM recrystallized DCBQ. The tick marks on the y axis represent 5 × 10−4 AU.