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. Author manuscript; available in PMC: 2012 Jul 1.
Published in final edited form as: J Photochem Photobiol B. 2011 Mar 3;104(1-2):51–59. doi: 10.1016/j.jphotobiol.2011.02.019

Figure 2.

Figure 2

Top. Fourier transforms of Sr EXAFS for intact and inactive Sr-substituted PS II samples (Chelex-treated). The dominant Fourier Peak I is due to ligating oxygens in the first coordination sphere and is common to both samples. The two Sr-PS II samples differ mainly at the R’ = 3.0 Å region, where the intact samples exhibit Fourier Peak II, which is from Sr-Mn vectors. Disruption of the Mn cluster in NH2OH-treated sample leads to the absence of Peak II. Bottom. Fourier Transform of Ca EXAFS from Chelex-treated, layered samples with 2 Ca/PS II with O2-evolving activity and an S2 EPR multiline signal. The FTs show the presence of a second Fourier peak in the 2Ca/PS II sample that fits to Ca-Mn that is absent in the control sample where the Mn complex has been disrupted with NH2OH.