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Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy.

Kern J, Tran R, Alonso-Mori R, Koroidov S, Echols N, Hattne J, Ibrahim M, Gul S, Laksmono H, Sierra RG, Gildea RJ, Han G, Hellmich J, Lassalle-Kaiser B, Chatterjee R, Brewster AS, Stan CA, Glöckner C, Lampe A, DiFiore D, Milathianaki D, Fry AR, Seibert MM, Koglin JE, Gallo E, Uhlig J, Sokaras D, Weng TC, Zwart PH, Skinner DE, Bogan MJ, Messerschmidt M, Glatzel P, Williams GJ, Boutet S, Adams PD, Zouni A, Messinger J, Sauter NK, Bergmann U, Yano J, Yachandra VK - Nat Commun (2014)

Bottom Line: The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash.Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å.This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

View Article: PubMed Central - PubMed

Affiliation: 1] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

ABSTRACT
The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

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Mn Kβ XES of PS II A) XES recorded with <50 fs X-ray pulses at LCLS. Spectra were measured 0.5 s after two laser flashes (2F, black; lasers 2 and 3 on), or 0.5 s after three laser flashes (3F, blue; lasers 1, 2, and 3 on), and ~250 μs after three laser flashes (3F′, red; lasers 2, 3, and 4 on), respectively. B) Difference between the Mn Kβ XES of PS II, blue: 3F – 2F; red: 3F′ – 2F. Before calculating the difference curves, spectra were smoothed by moving average (dotted line) or cubic polynomial fitting (solid line, similar to the procedure used for analyzing the synchrotron data). (C) the 3F – 2F difference spectrum (green) from SR data collected at 15 K.
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Figure 3: Mn Kβ XES of PS II A) XES recorded with <50 fs X-ray pulses at LCLS. Spectra were measured 0.5 s after two laser flashes (2F, black; lasers 2 and 3 on), or 0.5 s after three laser flashes (3F, blue; lasers 1, 2, and 3 on), and ~250 μs after three laser flashes (3F′, red; lasers 2, 3, and 4 on), respectively. B) Difference between the Mn Kβ XES of PS II, blue: 3F – 2F; red: 3F′ – 2F. Before calculating the difference curves, spectra were smoothed by moving average (dotted line) or cubic polynomial fitting (solid line, similar to the procedure used for analyzing the synchrotron data). (C) the 3F – 2F difference spectrum (green) from SR data collected at 15 K.

Mentions: We measured XES on PS II solutions at the CXI instrument32 at LCLS (see Methods). As shown in Fig. 3, a clear shift between the 2F (S3-enriched) and 3F (S0-enriched) spectra is observable. Calculation of the first moment (see Methods) revealed that the 3F spectrum is shifted about 0.1 eV to higher energies indicating a reduction of Mn26, as expected for the transition of the OEC from the highly oxidized S3 to the most reduced S0 state, in which the formal oxidation states are assigned as Mn4IV and Mn3IIIMnIV, respectively1,2,6,33,34. Comparing these data to synchrotron radiation (SR) data collected at cryogenic temperature from T. elongatus PS II and previously recorded data from spinach PS II35 shows a very similar trend (Fig. 3C and Supplementary Fig. 1).


Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy.

Kern J, Tran R, Alonso-Mori R, Koroidov S, Echols N, Hattne J, Ibrahim M, Gul S, Laksmono H, Sierra RG, Gildea RJ, Han G, Hellmich J, Lassalle-Kaiser B, Chatterjee R, Brewster AS, Stan CA, Glöckner C, Lampe A, DiFiore D, Milathianaki D, Fry AR, Seibert MM, Koglin JE, Gallo E, Uhlig J, Sokaras D, Weng TC, Zwart PH, Skinner DE, Bogan MJ, Messerschmidt M, Glatzel P, Williams GJ, Boutet S, Adams PD, Zouni A, Messinger J, Sauter NK, Bergmann U, Yano J, Yachandra VK - Nat Commun (2014)

Mn Kβ XES of PS II A) XES recorded with <50 fs X-ray pulses at LCLS. Spectra were measured 0.5 s after two laser flashes (2F, black; lasers 2 and 3 on), or 0.5 s after three laser flashes (3F, blue; lasers 1, 2, and 3 on), and ~250 μs after three laser flashes (3F′, red; lasers 2, 3, and 4 on), respectively. B) Difference between the Mn Kβ XES of PS II, blue: 3F – 2F; red: 3F′ – 2F. Before calculating the difference curves, spectra were smoothed by moving average (dotted line) or cubic polynomial fitting (solid line, similar to the procedure used for analyzing the synchrotron data). (C) the 3F – 2F difference spectrum (green) from SR data collected at 15 K.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4151126&req=5

Figure 3: Mn Kβ XES of PS II A) XES recorded with <50 fs X-ray pulses at LCLS. Spectra were measured 0.5 s after two laser flashes (2F, black; lasers 2 and 3 on), or 0.5 s after three laser flashes (3F, blue; lasers 1, 2, and 3 on), and ~250 μs after three laser flashes (3F′, red; lasers 2, 3, and 4 on), respectively. B) Difference between the Mn Kβ XES of PS II, blue: 3F – 2F; red: 3F′ – 2F. Before calculating the difference curves, spectra were smoothed by moving average (dotted line) or cubic polynomial fitting (solid line, similar to the procedure used for analyzing the synchrotron data). (C) the 3F – 2F difference spectrum (green) from SR data collected at 15 K.
Mentions: We measured XES on PS II solutions at the CXI instrument32 at LCLS (see Methods). As shown in Fig. 3, a clear shift between the 2F (S3-enriched) and 3F (S0-enriched) spectra is observable. Calculation of the first moment (see Methods) revealed that the 3F spectrum is shifted about 0.1 eV to higher energies indicating a reduction of Mn26, as expected for the transition of the OEC from the highly oxidized S3 to the most reduced S0 state, in which the formal oxidation states are assigned as Mn4IV and Mn3IIIMnIV, respectively1,2,6,33,34. Comparing these data to synchrotron radiation (SR) data collected at cryogenic temperature from T. elongatus PS II and previously recorded data from spinach PS II35 shows a very similar trend (Fig. 3C and Supplementary Fig. 1).

Bottom Line: The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash.Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å.This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

View Article: PubMed Central - PubMed

Affiliation: 1] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

ABSTRACT
The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

Show MeSH
Related in: MedlinePlus