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. Author manuscript; available in PMC: 2014 Aug 20.
Published in final edited form as: J Am Chem Soc. 2000 Apr 12;122(14):3399–3412. doi: 10.1021/ja992501u

Figure 4.

Figure 4

EXAFS contributions from Fourier peak II from S2 (dashed line) and S3 (solid line) states of PS II. The Fourier transform of the S3 state was obtained from the calculated S3 state EXAFS shown in Figure 1 (see text for details). Fourier peak II is assigned to Mn–Mn interactions at 2.7 Å in the S1 and S2 states. The increase in frequency evident in this figure in the S3 state compared to that in the S2 state is because of the increase in the Mn–Mn distance in the S3 state. The sin(2kR + α(k)) contribution to the EXAFS (eq 1) dictates that an increase in R will be reflected in an increase in the frequency, as shown in the S3 data compared to the S2 state spectra. EXAFS techniques are most sensitive to such changes in frequency because the changes are manifest over the entire range of the spectra and hence less susceptible to contributions from noise in the spectra.